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To determine the performance and impact of an airway management team (AMT) assembled during the COVID-19 pandemic.We conducted a retrospective cohort review of all adult patients who had received airway management services from the AMT (n = 269) and administered a survey questionnaire targeting physicians who had the option to activate the AMT (n = 77). The retrospective review determined the performance of the AMT, and the physicians' survey evaluated the impact of the AMT. The study was conducted at a large Canadian health centre (1,133 beds) from 28 March to 30 June 2020. We included patients in the cohort review who were ≥18 yr of age, whose chart showed that the AMT was activated, and whose airway was managed outside the operating room. We reviewed both electronic medical records and paper chart documentation. Outcomes included intubation success, number of intubation attempts, intubation time, team response time, patient contact time, intubation complications, and breaches of personal protective equipment (PPE) protocol. The physicians' survey evaluated the relevance, performance, reasonableness, and clinical utility of the AMT.The AMT intubated 231 patients. Charts showed that 91% of intubations were accomplished on first attempt. The mean (standard deviation) intubation time was 2.1 (0.2) min. The complication rate was minimal. The incidence of breaching PPE protocol items was less than 6%. No AMT members reported COVID-19 symptoms. The response rate for the physician's survey was 36%. The consensus among the participants was that the AMT had considerable clinical utility during the COVID-19 pandemic.An AMT assembled during the COVID-19 pandemic showed high competency and effectiveness, and had favourable impact on the main responsible physicians who activated the team.RéSUMé: OBJECTIF: Déterminer la performance et l’impact d’une équipe de prise en charge des voies aériennes (AMT - Airway Management Team) assemblée pendant la pandémie de COVID-19. MéTHODE: Nous avons réalisé une revue de cohorte rétrospective de tous les patients adultes qui avaient bénéficié des services de prise en charge des voies aériennes par l’AMT (n = 269) et avons soumis un questionnaire aux médecins qui avaient eu la possibilité de faire appel à l’AMT (n = 77). La revue rétrospective a permis de déterminer la performance de l’AMT, et le sondage auprès des médecins a évalué l’impact de cette équipe dédiée. L’étude a été réalisée dans un grand centre de santé canadien (1133 lits) du 28 mars au 30 juin 2020. Dans la revue de cohorte, nous avons inclus des patients âgés de ≥18 ans, dans le dossier médical desquels il était fait mention de l’activation de l’AMT et dont les voies aériennes avaient été prises en charge à l’extérieur de la salle d’opération. Nous avons passé en revue à la fois la documentation des dossiers médicaux informatisés et des dossiers papier. Les résultats mesurés comprenaient le succès de l’intubation, le nombre de tentatives d’intubation, le temps pour intubation, le temps de réponse de l’équipe, le temps de contact avec le patient, les complications de l’intubation et les violations du protocole relatif aux équipements de protection individuelle (EPI). Le sondage auprès des médecins a évalué la pertinence, la performance, le caractère raisonnable et l’utilité clinique de l’AMT. RéSULTATS: L’AMT a intubé 231 patients. Les dossiers ont montré que 91 % des intubations ont réussi à la première tentative. Le temps moyen (écart type) d’intubation était de 2,1 (0,2) min. Le taux de complications était minime. L’incidence d’infractions aux articles du protocole pour les EPI était inférieure à 6 %. Aucun membre de l’AMT n’a rapporté de symptômes de COVID-19. Le taux de réponse au sondage auprès des médecins était de 36 %. Le consensus parmi les participants était que l’AMT était d’une utilité clinique considérable pendant la pandémie de COVID-19. CONCLUSION: Une équipe de prise en charge des voies aériennes assemblée pendant la pandémie de COVID-19 a démontré une compétence et une efficacité élevées et a eu un impact favorable sur les principaux médecins en charge qui ont fait appel à l’équipe.

Background: We hypothesize that the addition of local infiltration analgesia (LIA) to a multimodal pain protocol will reduce the total amount of opioids consumed for acute pain control post total knee arthrolplasty (TKA). Methods: This study was a retrospective, matched pair study including patients who had primary TKA. All patients included in the analysis had preoperative oral celecoxib and acetaminophen, had single-dose spinal anesthetic with intrathecal morphine, and had intravenous patient-controlled analgesia with an opioid agent in addition to gabapentin and celecoxib in the first 48 h. Patients whose charts were excluded from the study had revision TKA, received opioid therapy prior to the surgery, were classified as American Society of Anesthesiology (ASA) IV, and had general anesthesia. Fifty patients who underwent TKA and had LIA were matched for age, body mass index (BMI), and gender with patients who did not receive LIA. The primary outcome measures were total doses of opioids consumed post TKA. Results: Patients receiving LIA consumed on average significantly less intravenous (IV) morphine equivalents than patients not receiving LIA, with a mean difference (±SD) of 88.9 ± 15.6 mg IV morphine equivalents. Furthermore, pain control was better in the LIA group. The incidences of nausea and vomiting, pruritis, and excessive sedation were higher in the non-LIA group compared to the LIA group. There was no difference in the hospital length of stay between both groups. Conclusions: The addition of LIA to our multimodal pain protocol for TKA was associated with a reduction in total opioid consumption.

[Introduction][1] Total knee arthroplasty alleviates pain and restores function in patients with osteoarthritis of the knee, but it is associated with postoperative blood loss resulting in anemia and allogeneic blood transfusion in 10% to 38% of patients. [Step 1: Prepare Solution][2] Prepare tranexamic acid solution using aseptic technique. ![Figure][3] [Step 2: Apply Solution][4] Apply tranexamic acid solution to the open joint and soft-tissue surfaces. ![Figure][3] [Step 3: Remove Solution and Close][5] Remove tranexamic acid, keeping the tourniquet inflated until the wound is closed and the dressing is applied. [Results & Preop./Postop. Images][6] We showed, in a prospective, double-blinded, placebo-controlled randomized trial, that topical application of tranexamic acid directly into the surgical wound prior to closure at the end of a total knee arthroplasty reduces postoperative bleeding by 20% to 25%, or 300 to 400 mL. [What to Watch For][7] [Indications][8] [Contraindications][9] [Pitfalls & Challenges][10] [Introduction][1] Total knee arthroplasty alleviates pain and restores function in patients with osteoarthritis of the knee, but it is associated with postoperative blood loss resulting in anemia and allogeneic blood transfusion in 10% to 38% of patients. [Step 1: Prepare Solution][2] Prepare tranexamic acid solution using aseptic technique. ![Figure][3] [Step 2: Apply Solution][4] Apply tranexamic acid solution to the open joint and soft-tissue surfaces. ![Figure][3] [Step 3: Remove Solution and Close][5] Remove tranexamic acid, keeping the tourniquet inflated until the wound is closed and the dressing is applied. [Results & Preop./Postop. Images][6] We showed, in a prospective, double-blinded, placebo-controlled randomized trial, that topical application of tranexamic acid directly into the surgical wound prior to closure at the end of a total knee arthroplasty reduces postoperative bleeding by 20% to 25%, or 300 to 400 mL. [What to Watch For][7] [Indications][8] [Contraindications][9] [Pitfalls & Challenges][10] [1]: #sec-7 [2]: #sec-8 [3]: pending:yes [4]: #sec-9 [5]: #sec-10 [6]: #sec-11 [7]: #sec-12 [8]: #sec-13 [9]: #sec-14 [10]: #sec-15

The incidence of perioperative brachial plexus injury is not precisely known. Retrospective studies suggested that brachial plexus injuries represent about 20-28% of the total perioperative peripheral nerve injuries. There are various risk factors for brachial plexus injury under anesthesia and surgery including preexisting disease, preexisting abnormal anatomical features, poor positioning, long surgical duration, hypotension, and hypothermia. Brachial plexus injury can be classified into preganglionic, postganglionic, or mixed pre and postganglionic. The most common perioperative brachial plexus injury are ulnar nerve injury, upper/middle trunk injury and lower trunk injury. Pathologically, a brachial plexus injury is classified into neuropraxia, axonotmesis, and neurotemsis. Such pathologic classification has a prognostic value and can determine treatment strategy. Treatment of brachial plexus injury is essentially conservative. If surgical intervention is necessary, it is usually a lengthy procedure associated with specific anesthetic considerations including pressure care, temperature control, adequate fluid therapy to maintain normal volume status, prolonged ventilation strategy, control of blood sugar and acid-base balance, electromyography testing, and thromboembolic prophylaxis.

Background Propofol is used to induce deep sedation or general anaesthesia for procedures in children. Adjuvants, such as ketamine, are routinely added to reduce the dose of propofol required and propofol-related adverse events. We conducted a randomised controlled trial to determine the effective bolus dose of propofol in combination with ketamine that induces adequate depth of anaesthesia in 50% of children (ED50) undergoing gastro-duodenoscopy. Methods Children were randomised to one of four doses of ketamine: 0 (control), 0.25, 0.5, and 1 mg kg−1, followed by a dose of propofol according to Dixon's up-and-down methodology. Excessive movement, coughing, gagging, or airway obstruction that prevented endoscope insertion was considered a failure. Results The ED50 of propofol (median, 95% CI) was greater in the ketamine 0, 0.25, and 0.5 mg kg−1 groups compared with the ketamine 1 mg kg−1 group (6.1, 4.1–8.1; 4.5, 2.9–6; 4.7, 3.1–6.2 mg kg−1 vs 1.1, 0.5–1.8 mg kg−1, respectively, P Conclusions Ketamine at 0.5–1 mg kg–1 reduces the dose of propofol required to provide general anaesthesia for gastro-duodenoscopy in children and may reduce the incidence of propofol-related changes in haemodynamics. Clinical trial registration NCT 02295553.

The prevalence of congenital heart disease (CHD) is about 8–9 per 1000 live births and 3–6 per 1000 adults [1]. The survivability of infants and children born with CHD has increased dramatically compared to four decades ago where 85% of patients died in childhood. Recent reports showed that approximately 96%, 98%, and 56% of pediatric patients with mild, moderate, and severe CHD survived until adulthood, respectively [1]. Improvements in diagnosis of defects, surgical techniques, and perioperative care have contributed to this marked increase in survival [2]. Therefore, the clinical anesthesiologist will have to increasingly administer anesthesia to surviving patients with CHD who have neurosurgical emergencies or elective procedures. A thorough understanding of CHD and its pathophysiologic impact is essential for successful anesthetic management.

Intracerebral hemorrhage (ICH) is a catastrophic event that may lead to severe disability or death. It is associated with major disruption of intracranial neurophysiology and subsequent neuronal tissue injury. The etiology of ICH may be primary (e.g., hypertensive) or secondary (e.g., traumatic). Treatment options include conservative management or neurosurgical intervention in selected patients. In order to manage these challenging cases, the anesthesiologist and the intensivist should have thorough knowledge pertaining to neurophysiologic concepts of cerebral blood flow, cerebral autoregulation, and neuroprotection principles. Additionally, the specialized team managing the patient with ICH should be cognizant of the most recent evidence-based guidelines recommended by the pertinent associations.

Background Post-operative delirium (POD) is a common post-operative complication in elderly individuals and imposes a significant health and financial burden. Identifying predictive biomarkers may help understand the pathophysiology of POD. Our objective is to summarize the evidence of pre-operative biomarkers and imaging tests to predict POD in patients undergoing non-cardiac surgery. Methods A systematic search of English language articles in MEDLINE, EMBASE, Cochrane Database, PsychINFO, PubMed and ClinicalTrials. Gov up to January 2018 was performed. Studies that used biomarkers or imaging tests to predict POD and a validated POD assessment tool were included. Animal studies, paediatric, cardiac and intracranial surgery were excluded. Risk of bias was assessed using the Quality In Prognosis Study tool. Results Thirty-four prospective cohort studies involving 4424 patients were included. Nineteen studies described serum tests [Interleukin-6, Insulin-like Growth Factor 1, C-Reactive Protein (CRP), cholinesterases, apolipoprotein-E genotype, leptin, hypovitaminosis, hypoalbuminaemia, gamma-amino butyric acid], 10 described cerebral-spinal fluid tests (monoamine precursor, melatonin, acute phase proteins, S100B and neurofibrillary tangles), and 5 described imaging tests. Two studies had high risk of bias due to unclear outcome measurement and study participation. CRP was significantly associated with POD in 5 studies. Other biomarkers were either examined by only a single study or two or more studies with conflicting results. Conclusion CRP is the most promising biomarker associated with POD. However, we are still in the early stages in identifying biomarkers and imaging tests that may further understanding of the pathophysiology of POD. Electronic supplementary material The online version of this article (10.1186/s12871-019-0693-y) contains supplementary material, which is available to authorized users.

This paper presents a novel method for extracting auditory steady state response (ASSR) signals from background electroencephalogram. 40-Hz ASSR signals are sensitive to subject's state of consciousness and can be used as a monitor for the depth of anaesthesia. The suggested method is a multilevel adaptive wavelet denoising scheme that extracts ASSR cycles faster than the currently used averaging schemes and can monitor depth of anesthesia with minimum delay. It estimates the variance of noise and adapts the threshold at each denoising level. The algorithm benefits from the fact that wavelet transform preserves temporality and takes into consideration the correlation of the neighbor wavelet coefficients. Our method extracts ASSR from small number of epochs in a short time moreover, it does not neglect the variations of the signal from one epoch to the other and outperforms averaging. The performance of the proposed scheme is evaluated on the synthetic and on real data recorded during induction of anaesthesia ASSR signals in the paper.

OBJECTIVE Peripheral nerve imaging by portable ultrasound (US) may serve as a noninvasive and lower-cost alternative to nerve conduction studies (NCS) for diagnosis and staging of diabetic sensorimotor polyneuropathy (DSP). We aimed to examine the association between the size of the posterior tibial nerve (PTN) and the presence and severity of DSP. RESEARCH DESIGN AND METHODS We performed a cross-sectional study of 98 consecutive diabetic patients classified by NCS as subjects with DSP or control subjects. Severity was determined using the Toronto Clinical Neuropathy Score. A masked expert sonographer measured the cross-sectional area (CSA) of the PTN at 1, 3, and 5 cm proximal to the medial malleolus. RESULTS Fifty-five patients had DSP. The mean CSA of the PTN in DSP compared with control subjects at distances of 1 (23.03 vs. 17.72 mm2; P = 0.004), 3 (22.59 vs. 17.69 mm2; P < 0.0001), and 5 cm (22.05 vs. 17.25 mm2; P = 0.0005) proximal to the medial malleolus was significantly larger. Although the area under the curve (AUC) for CSA measurements at all three anatomical levels was similar, the CSA measured at 3 cm above the medial malleolus had an optimal threshold value for identification of DSP (19.01 mm2) with a sensitivity of 0.69 and a specificity of 0.77 by AUC analysis. CONCLUSIONS This large study of diabetic patients confirms that the CSA of the PTN is larger in patients with DSP than in control subjects, and US is a promising point-of-care screening tool for DSP.

Background Perioperative hypothermia has been reported to increase the occurrence of cardiovascular complications. By increasing the activity of sympathetic nervous system, perioperative hypothermia also has the potential to increase cardiac injury and dysfunction associated with subarachnoid hemorrhage. Methods The Intraoperative Hypothermia for Aneurysm Surgery Trial randomized patients undergoing cerebral aneurysm surgery to intraoperative hypothermia (n = 499, 33.3 degrees +/- 0.8 degrees C) or normothermia (n = 501, 36.7 degrees +/- 0.5 degrees C). Cardiovascular events (hypotension, arrhythmias, vasopressor use, myocardial infarction, and others) were prospectively followed until 3-month follow-up and were compared in hypothermic and normothermic patients. A subset of 62 patients (hypothermia, n = 33; normothermia, n = 29) also had preoperative and postoperative (within 24 h) measurement of cardiac troponin-I and echocardiography to explore the association between perioperative hypothermia and subarachnoid hemorrhage-associated myocardial injury and left ventricular function. Results There was no difference between hypothermic and normothermic patients in the occurrence of any single cardiovascular event or in composite cardiovascular events. There was no difference in mortality (6%) between groups, and there was only a single primary cardiovascular death (normothermia). There was no difference between hypothermic and normothermic patients in postoperative versus preoperative left ventricular regional wall motion or ejection fraction. Compared with preoperative values, hypothermic patients had no postoperative increase in cardiac troponin-I (median change 0.00 microg/l), whereas normothermic patients had a small postoperative increase (median change + 0.01 microg/l, P = 0.038). Conclusion In patients undergoing cerebral aneurysm surgery, perioperative hypothermia was not associated with an increased occurrence of cardiovascular events.

Intraneural injection can be seen as nerve expansion during ultrasound-guided regional anesthesia. The purpose of this animal study was to determine if nerve expansion seen on ultrasound during intraneural injection results in nerve injury.Ten pigs underwent general anesthesia for this randomized control study. After skin incision, the right and left median nerves for each animal were randomly assigned to the local anesthetic (LA) side or control side. For the LA side, a needle was placed intraneurally under direct vision. Nerve expansion seen on ultrasound was produced by injecting up to 20 mL lidocaine 2% with epinephrine intraneurally. For the control side, no needle puncture or injection was administered. The primary outcome was histologic evidence of nerve injury (axonal retraction balls) on the seventh postoperative day after intraneural injection seen as nerve expansion on ultrasound. Correlation coefficients were calculated between the maximum volume injected, maximum injection pressure, degree of nerve expansion, and histologic and functional nerve injury.Six nerves from the LA side and none from the control side had histologic evidence of injury (P0.01). All 10 nerves from the LA side exhibited histologic evidence of inflammation compared with 3 from the control side (P0.005). No pigs exhibited functional nerve injury. We were unable to demonstrate any correlation between the maximum volume injected or pressure generated and the relative increase in nerve cross-sectional area or the graded presence of any histologic markers of inflammation or injury.This animal study suggests that nerve expansion seen on ultrasound during intraneural injection of clinically relevant volumes of LA results in histologic but not functional nerve injury.

Background and Objectives: The aim of this study was to determine the minimum effective anesthetic volume required to produce an effective supraclavicular block for surgical anesthesia using an ultrasound (US)-guided technique. Methods: Twenty-one adults undergoing elective upper limb surgery received a US-guided supraclavicular block. The initial volume of local anesthetic (LA; 50:50 mixture of lidocaine 2% and bupivacaine 0.5% with epinephrine) injected was 30 mL, which was subsequently varied by 5 mL for each consecutive patient according to the response of the previous patient. The minimum effective anesthetic volume in 50% of patients was determined using the Dixon and Massey up-and-down method. The effective volume in 95% of patients (ED95) was calculated using probit transformation and logistic regression. Results: The minimum effective anesthetic volume in 50% and calculated effective volume in 95% of patients were 23 mL (95% confidence interval, 13-39 mL) and 42 mL (95% confidence interval, 19-65 mL), respectively. Seven patients received supplemental LA, with no patient requiring a general anesthetic. Conclusion: In this study, the minimum volume required for US-guided supraclavicular block in 50% of patients was 23 mL, and in 95% of patients was 42 mL. Under the present study conditions, the calculated volume of LA required for US-guided supraclavicular block does not seem to differ from the conventionally recommended volume required for supraclavicular blocks using non-US-based nerve localization techniques.

We aimed to identify current clinical practice patterns among members of the American Society of Regional Anesthesia and Pain Medicine (ASRA) members that relate to complications of regional anesthesia (RA).Invitations were posted to the 3,732 ASRA members, to participate in our survey. Members were asked to report the types and numbers of blocks performed annually, preferred nerve localization techniques, and routine risk disclosure practices prior to common neuraxial (NAB) and peripheral nerve (PNB) block techniques.The number of respondents was 801 (response rate: 21.7%). Approximately half of the respondents perform100 spinal and epidural blocks but50 of each listed PNB annually. With the exception of axillary block, nerve stimulation is the overwhelmingly preferred nerve localization technique for PNB. Five hundred twenty-nine respondents (66.2%) disclose of RA primarily to allow patients to make an informed choice, while 227 (28.4%) disclose for medicolegal reasons. For NAB, the most commonly disclosed risks are headache and local pain/discomfort. Neurological complications following NAB such as permanent neuropathy and paralysis are inconsistently disclosed. For PNB, the most commonly disclosed risks are local pain/discomfort and transient neuropathy. The least commonly disclosed risks for both NAB and PNB include seizures, respiratory failure, cardiac arrest, and death. With the exception of headache following spinal anesthesia (1:100) and Horner's syndrome following interscalene block (1:10), there is little consensus regarding the perceived incidence of complications.Based on a 22% response rate, our survey suggests that the risks of RA most commonly disclosed to patients by ASRA members are benign while severe complications of RA are far less commonly disclosed. There is little agreement among ASRA members regarding their perceived incidence of complications following RA.

Purpose: Ultrasound (US) is being used increasingly to guide needle placement during axillary brachial plexus blockade (AXB). This retrospective study investigated whether US guidance can increase the success rate, decrease block onset time, and reduce local anesthetic (LA) volume for AXB compared to a traditional (TRAD) approach, namely, peripheral nerve stimulation (PNS) and transarterial (TA) techniques. Methods: The anesthetic records, operative reports, discharge summaries, and surgical consultation notes of all patients who had undergone AXB for surgical anesthesia at the Toronto Western Hospital, between October 2003 and November 2006 were, retrospectively reviewed for evidence of block success and associated complications. Block success was defined as the achievement of surgical anesthesia without additional LA supplementation. Results: Among the 662 patients, 535 patients underwent AXB using US guidance (US group), and 127 using TRAD techniques (TRAD group), namely, 56 using PNS (PNS subgroup) and 71 using the TA technique (TA subgroup). The block success rate was higher in the US group compared to the TRAD group (91.6%vs 81.9%,p=0.003). The LA volume used for AXB was less in the US group compared to the TRAD group (39.8±6.4 mLvs 46.7±17.1 mL,p

Background and Objectives: In view of the relatively few large studies available to estimate the rates of complications following regional anesthesia, we aimed to identify and quantify the risks that academic regional anesthesiologists and regional anesthesia fellows disclose to their patients before performing central and peripheral nerve blockade. Methods: We asked 23 North American regional anesthesia fellowship program directors to distribute a questionnaire to the regional anesthesiologists and regional anesthesia fellows at their institutions. The questionnaire was designed to capture the risks and corresponding incidences that are routinely disclosed to patients before performing the most common central and peripheral nerve block techniques. Results: The total number of respondents was 79 from 12 different institutions. Fifty-eight (74%) respondents disclose risks of regional anesthesia in order to allow their patients to make an informed choice, whereas 20 (26%) disclose risks for medicolegal reasons. For central neural blockade, the most commonly disclosed risks are headache, local pain/discomfort, and infection. For peripheral nerve blockade, the most commonly disclosed risks are transient neuropathy, local pain/discomfort, and infection. For both central and peripheral nerve blockade, the risks most commonly disclosed are also those with the highest-reported incidences. Conclusions: The risks of regional anesthesia most commonly disclosed to patients by academic regional anesthesiologists and regional anesthesia fellows are benign in nature and occur frequently. Severe complications of regional anesthesia are far less commonly disclosed. The incidences of severe complications disclosed by academic regional anesthesiologists and their fellows can be inconsistent with those cited in the contemporary literature.

40-Hz auditory steady state responses (ASSR)s recorded from 12 human subjects during Propofol-induced anesthesia are studied in this paper. The 40-Hz ASSR signals are recorded in 8 channel stimulated electroencephalogram (EEG). The ASSR sweeps are extracted from 300 stimulated EEG epochs and updated every 0.5 seconds. Variations of the signal in time and frequency in 8 different channels are investigated both in constant times before and after anesthetic injection and relative to eyelash reflex disappearance in order to achieve a consistent result among all subjects. The latter demonstrates reduction in peak to peak amplitude 40 Hz and 80 Hz components of the signals after eyelash reflex disappearance in all 8 channels for all subjects.

Gap junctions are protein channels that directly connect the cytosol of neighboring cells, thus forming electrical synapses and promoting synchronous neuronal activities. Such activities lead to the initiation and propagation of electroencephalogram oscillations implicated in cognition and consciousness. In this study, we investigated the effects of propofol, thiopental, and halothane on gap junction communication in cultured organotypic hippocampal slices by recovery of fluorescence after photo bleaching (FRAP) technique and electrophysiological recordings. Propofol 15 microM and thiopental 10 microM attenuated gap junction communication in slice cultures by 46.7% +/- 4.5% and 48.8% +/- 5.5%, respectively, as measured by FRAP. Smaller concentrations of propofol 5 microM and thiopental 2 microM did not change gap junction coupling. Accompanying the decreased gap junction communication, hippocampus slice cultures exposed to propofol 15 microM and thiopental 10 microM were found to have reduced electrophysiologic spontaneous discharges and primary after discharges evoked by a tetanic train of 50 Hz for 2 s. On the other hand, halothane 0.64 mM, a concentration slightly larger than twice its minimum alveolar concentration had no effect on gap junction coupling while halothane 2.8 mM blocked FRAP by 70%. The current study illustrates that anesthetic concentrations of propofol and thiopental, but not halothane, attenuate gap junction communication in cultured hippocampal slices. Suppression of gap junction function could compound the mechanisms of anesthetic actions.

Impaired regulation of intracellular calcium is thought to adversely affect synaptic plasticity and cognition in the aged brain. Comparing young (2–3 months) and aged (23–26 months) Fisher 344 rats, stratum radiatum-evoked CA1 field EPSPs were smaller and long-term potentiation (LTP) was diminished in aged hippocampal slices. Resting calcium, in presynaptic axonal terminals in the CA1 stratum radiatum area, was elevated in aged slices. Loading the slice with the calcium chelator, BAPTA-AM, depressed LTP in young slices, but enhanced this plasticity in old slices. Forty-five minutes following LTP-inducing high frequency stimulation, resting calcium levels were significantly increased in both young and old presynaptic terminals, and significantly reduced by pretreatment with BAPTA-AM. In vivo, intraperitoneal administration of BAPTA-AM prior to training in the reference memory version of the Morris water maze test, significantly improved the acquisition of spatial learning in aged animals, without a significant effect in young rats. These results support the hypothesis that increasing intracellular neuronal buffering power for calcium in aged rats ameliorates age-related impaired synaptic plasticity and learning.

Gap junction communication is widespread throughout the mammalian nervous system among neurons as well as glia. We addressed the hypothesis that general anesthetics attenuate gap junction mediated coupling in P19 cell line that can differentiate into neuronal-like cells and astrocytes and oligodendrocytes. We characterized the extent of dye coupling over time in the P19 cell line using colocalization of chlormethylbenzamido-1,1 dioctadecyl-3,3,3',3'-tetramethylindocarbocyamine (CM-DiI) and calcein-AM in donor and recipient cells in cocultures. After seeding, the gap junction permeant dye calcein spreads from donor to recipient cells. CM-DiI and calcein fluorescence identified donor and recipient cells, respectively. The extent of intercellular connections was evaluated using cell counting and flow cytometry up to 2 hr after treatment. Clinically relevant concentrations of the intravenous anesthetics propofol (15 microM) and thiopental (10 microM) attenuated gap junction permeability in P19 cell cultures. In contrast, halothane, a volatile anesthetic in a concentration (0.64 mM) relevant to its free aqueous EC50 had no effect on gap junction coupling; however, very high halothane concentrations (2.8 mM) blocked dye transfer by approximately 90%. The results indicate that halothane concentrations pertinent to clinical anesthesia were unable to attenuate gap junction communication in a cell line that can express neuronal and glial gap junction proteins; however, clinically relevant concentrations of propofol and thiopental depressed gap junction coupling.

Background Opioids are known to stimulate surface electroencephalographic activity in patients with temporal lobe epilepsy. The objective of the current study was to compare the electrocorticographic activation effects of the newer short-acting opioid remifentanil with those of alfentanil during epilepsy surgery under general anaesthesia. Methods Thirteen patients undergoing temporal lobe epilepsy surgery under general anaesthesia received alfentanil 30 μg kg−1 and remifentanil 1 μg kg−1 as i.v. boluses in sequence. The design was a randomized double-blind cross-over study. After opening the dura, electrocorticogram (ECoG) electrode contact strips were placed over the temporal and supratemporal neocortex and depth electrodes were inserted in the amygdala and hippocampus. Alfentanil 30 μg kg−1 or remifentanil 1 μg kg−1 were administered randomly in a blinded fashion. The ECoG was recorded continuously before and after the injection of each drug. The interictal epileptiform activity (spikes and sharp waves) above baseline was analysed. Results Both drugs increased epileptiform activity especially that recorded from depth electrodes in the temporal limbic structures. No epileptiform activity was recorded from the electrodes overlying the supratemporal neocortex before or after drug administration. The more potent activator was alfentanil, which caused an increase in activation from baseline of 99.8% compared with 67.4% for remifentanil. In addition, alfentanil activated the epileptiform activity in 3 patients in which remifentanil had no effect. There were no changes in heart rate after the opioid boluses. Both remifentanil and alfentanil caused significant reductions in blood pressure at 3 and 5 min after administration. Conclusion We conclude that at the doses used in this study, alfentanil is the better opioid for intraoperative activation of the ECoG in neurosurgical patients undergoing resection of a temporal lobe epileptic focus. This pharmacological activation of epileptiform activity assists in localizing and confirming the site of surgical excision. Neither alfentanil nor remifentanil activated epileptiform activity in non-epileptic brain tissue.

Regional analgesic techniques are commonly used in pediatric urology. Ultrasound guided transversus abdominis plane block has recently gained popularity. However, there is a paucity of information supporting a benefit over regional field infiltration. We present a parallel group, randomized, controlled trial evaluating ultrasound guided transversus abdominis plane block superiority over surgeon delivered regional field infiltration for children undergoing open pyeloplasty at a tertiary referral center.Following ethics board approval and registration, children 0 to 6 years old were recruited and randomized to undergo perioperative transversus abdominis plane block or regional field infiltration for early post-pyeloplasty pain control. General anesthetic delivery, surgical technique and postoperative analgesics were standardized. A blinded assessor regularly captured pain scores in the recovery room using the FLACC (Face, Legs, Activity, Cry, Consolability) scale. The primary outcome was the need for rescue morphine administration based on a FLACC score of 3 or higher.Two pediatric urologists performed 57 pyeloplasties during a 2.5-year period, enrolling 32 children (16 in each group, balanced for age and weight). There were statistically significant differences in the number of children requiring rescue morphine administration (13 of 16 receiving transversus abdominis plane block and 6 of 16 receiving regional field infiltration, p = 0.011), mean ± SD total morphine consumption (0.066 ± 0.051 vs 0.028 ± 0.040 mg/kg, p = 0.021) and mean ± SD pain scores (5 ± 5 vs 2 ± 3, p = 0.043) in the recovery room, in favor of surgeon administered regional field infiltration. No local anesthetic specific adverse events were noted.Ultrasound guided transversus abdominis plane block is not superior to regional field infiltration with bupivacaine as a strategy to minimize early opioid requirements following open pyeloplasty in children. Instead, our data suggest that surgeon delivered regional field infiltration provides better pain control.

To describe loss of the airway during tracheostomy and suggest a method for re-establishment of the airway and providing rescue oxygenation.A 22-yr-old female diagnosed with encephalomyelopathy was admitted to the intensive care unit with a progressively deteriorating level of consciousness and respiratory failure requiring intubation and ventilation. Several weeks later, an elective tracheostomy was performed under anesthesia. The surgeon made an anterior tracheal wall incision and inserted a cuffed #6 Shiley tracheostomy tube. No end-tidal CO(2) was detected and the patient could not be ventilated. After another failed attempt at insertion of a second tracheostomy tube, the diagnosis was made of a false passage within the trachea. The Shiley tracheostomy tube was removed and a #6 regular endotracheal tube was introduced in the trachea through the tracheostomy incision. The patient now could be ventilated with difficulty and low readings of end-tidal CO(2) were noted. Despite all efforts to further ventilate the patient, the arterial oxygen saturation never recovered, resulting in cardiac arrest.To restore a lost airway during tracheostomy, we recommend that a jet ventilation airway exchange catheter (JVAE) be inserted in the endotracheal tube through a bronchoscope port attachment prior to surgical entry into the trachea. The JVAE will also ensure continued ability to oxygenate the patient.

Retropharyngeal abscess formation has the potential for acute respiratory compromise from obstruction or secondarily from rupture. The initial attempt to secure the airway is of paramount importance. We describe a patient with an unstable cervical spine secondary to Pott’s disease who developed progressively obstructing retropharyngeal cold abscess. A 33-yr-old man with an unstable C-spine in halo traction presented with progressive airway obstruction secondary to retropharyngeal abscess extending from the cervical to the mid-thoracic vertebrae. After review of computerized tomography (CT) and magnetic resonance (MR) studies, preparations were made to secure the airway through fibreoptic assisted intubation. A conservative approach was chosen to secure the airway before surgical airway control as a first line approach. Following local and topical anesthesia, awake endoscopy was performed to assess the extent of obstruction and possibility of intubation without abscess rupture. A narrow tract along the lateral pharynx was identified to continue inferiorly to the epiglottis, from which point the cords were visualized. Extensive edema and abscess formation otherwise distorted the normal anatomy and prevented visualization from other directions. The airway was successfully secured without trauma with a well-lubricated 7.0 mm ID endotracheal tube. This report suggests that selected cases of tense obstructing retropharyngeal abscesses can be effectively managed with fibreoptic endoscopy for assessment and subsequent intubation before requiring surgical airway control as a first line strategy.

We evaluated the effectiveness of alfentanil and fentanyl in stimulating epileptogenic activity during surgery for intractable temporal lobe epilepsy under general anesthesia. Ten patients received a standardized anesthetic induction with IV fentanyl 5 mg/kg, propofol 3‐5 mg/kg, and atracurium 0.5 mg/kg. Maintenance was with isoflurane, 70% N2O/30% O2, and an atracurium infusion. After dural opening, droperidol 0.02 mg/kg was administered IV. Both inhaled anesthetics were discontinued and verified to be at 0 endtidal concentration before the study. Baseline electrocorticography over the surface of the temporal lobe and depth electrode recordings in the amygdala and hippocampus were obtained, followed by 10 min of recording before and after the IV administration of both alfentanil 50 mg/kg and fentanyl 10 mg/kg. Any changes in cardiovascular variables were documented. The number of interictal epileptiform spikes at the most active site for each patient was tabulated before and after the administration of each drug. Both alfentanil and fentanyl induced an increase in spike activity in all patients. Alfentanil was more potent, increasing the median number of spikes per epoch from 18 to 58, compared with fentanyl (20 to 42 spikes) (P , 0.05). Alfentanil had a shorter duration of action (4.9 6 1.3 min) compared with fentanyl (8.5 6 2 min) (P , 0.009). In nine patients, the most active site was the hippocampus or amygdala. There was a decrease in mean blood pressure, but only after the administration of alfentanil (P , 0.05). Two patients had electrographic evidence of seizure activity. These opioids can be used to assist in the localization of the epileptogenic focus during surgery. Implications: Both alfentanil and fentanyl activate epileptiform activity in patients with temporal lobe epilepsy. These opioids can be used to assist in the localization of the epileptogenic focus during surgery.

In replantation surgery, the use of continuous brachial plexus blockade (CBPB) is popular as it improves postoperative analgesia and vascular flow. The aim of our study was to determine whether CBPB may affect the odds of survivability of replanted digit(s). A four-year retrospective chart review was performed and various parameters affecting replant survival were examined. Outcome was recorded as successful if the transplanted digit(s) survived six months after discharge. All the independent variables were forced into a regression model without using a specific variable selection algorithm. The data for 146 patients was obtained from our chart review. The success rate of replanted digits in the patients reviewed was 65.8%. The logistic regression model showed a relation between the number of digits injured and replanted digit(s) survival. Our study showed that CBPB has no effect on the survivability of the replanted digit(s) till six months after hospital discharge.

Immunohistochemical staining for the calcium-binding protein calbindin-D28k (CaBP) was combined with Lucifer Yellow (LY) identification and intracellular recording of changes in membrane parameters of pyramidal neurons in CA2, CA1, and the sebiculum of rat hippocampal slices during brief exposure (4.0 ± 0.19 min) to N2. Anoxia evoked either a depolarization or hyperpolarization of membrane potential (VM) (+21.5 ± 2.79 mV above VM = −70.5 ± 1.50 mV, n = 30 and −7.2 ± 0.72 mV below VM = −68.2 ± 1.34 mV, n = 24, respectively) and a fall in membrane resistance of =20%. Differences in the response could be correlated with the presence or absence of CaBP and the localization of neurons in different layers of stratum pyramidale and sectors of the hippocampus. For neurons immunopositive for calbindin (CaBP(+)), depolarization was observed more frequently (83%) than hyperpolarization (17%); in contrast, 44% of responses of calbindin-negative (CaBP(−)) neurons were depolarizing and 56% were hyperpolarizing. Depolarizations of CaBP(+) neurons were more gradual in slope, and more rapidly reached a plateau in comparison with those recorded in CaBP(−) neurons. Responses of neurons in the superficial layer of stratum pyramidale (in which 79% of CaBP(+) pyramidal neurons were situated) were mainly depolarizing (91%), while for those in the deep layer (which contained 89% of the CaBP(−) cells) such responses were observed less often (45%). Depolarization was also more common than hyperpolarization for cells located in CA2/CA1c/CA1b (63%) than in the CA1a/subicular region (37%). The depolarizing response of the majority of pyramidal neurons which are CaBP(+), superficial, and closer to CA3 may reflect an efficient buffering of intracellular Ca2+, which maintains a low [Ca2+]i, steep gradient for Ca2+ influx and may facilitate the movement of Ca2+ away from points of entry. The neurons which are CaBP(−), deep, and closer to subiculum and in which N2 evokes hyperpolarization, on the other hand, may have a sustained elevation/accumulation of cytosolic Ca2+ which could activate K+ conductance, inhibit Ca2+ influx, and stabilize the membrane potential. These experiments provide a functional correlate for CaBP and suggest that it may have a significant role in Ca2+ homeostasis and the determination of selective neuronal vulnerability. © 1995 Wiley-Liss, Inc.

Study Objectives To determine the combined effects of aging and propofol on autonomic nervous system activity using heart rate variability (HRV) analysis. Design Prospective, two-parallel group, repeated-measures study. Setting Operating room of an academic hospital. Patients ASA physical status 1, 2, and 3 patients, including 14 young ( 65 yrs) patients. All patients were scheduled for general surgical procedures with general anesthesia. Interventions Each patient received two successive propofol doses during induction (0.5 mg/kg and 1.5 mg/kg) with a time interval allowing the return of Bispectral Index (BIS) to awake values. Measurements Primary outcomes were HRV parameters, which included normalized power spectral density at low frequency (LFnorm) and high frequency (HFnorm) bands and the ratio LF/HF. Secondary outcomes were BIS values, blood pressure, heart rate, respiratory rate, and body temperature. Main Results The interaction of age and propofol dose level was significant [multivariate analysis of variance, F (3,74) = 4.72, P = 0.005], representing a combined effect of age and propofol dose level on the mean HRV parameters. Propofol induction decreased the HFnorm component and enhanced LFnorm and LF/HF in the younger group, but had no significant effect in the older group. Such an effect was not associated with a significant difference in systolic blood pressure (SBP) decrements between the younger and older groups. Within each group, propofol caused significant decreases in SBP compared with preinduction values. Heart rate did not change significantly during propofol administration between groups or within groups. Conclusions Propofol and aging act in synergy to depress the activity of the cardiovascular component of the autonomic nervous system. However, a compensatory increase in sympathetic outflow was seen in young patients. Such counterbalance was not observed in the older group.

Purpose of review The quest for neuroprotection strategies during periods of neuronal vulnerability persists despite decades of basic and clinical research. This review will focus on the latest developments in the area of clinical brain protection with the major emphasis on strategies that can be beneficial during neurosurgical procedures. Recent findings Brain protection in neurosurgical patients may be achieved by nonpharmacological and pharmacological strategies. Pharmacological neuroprotection including anaesthetic administration have not been recently shown to be successful. Alternatively, nonpharmacological strategies including maintenance of cerebral perfusion by adequate control of mean arterial pressure (≥80 mmHg), liberal normoglycaemia (7.8-10 mmol/l), adequate haemoglobin levels (preoperative ≥120 g/l and intraoperative ≥90 g/l) and induction of hypertension (20-40% of preoperative values) in certain neurosurgical situations can be beneficial as neuroprotectants during neurosurgery. Mild hypothermia (32-35°C) failed to achieve neuroprotective effects in several situations of brain injury. Summary The findings of this review suggest that the anaesthesiologist is compelled to use nonpharmacological strategies sometimes based on empiric evidence to protect the brain during neurosurgical procedures. These strategies are simple, have high benefit/risk ratios and are inexpensive. Rigorous controlled clinical studies are needed to investigate the neuroprotective efficacy of these commonly used nonpharmacological methods.

The administration of the anesthetic agents is known to alter the electroencephalogram (EEG) signal significantly with the brain being their primary target. In this study, we analyzed the EEG recorded from six ASA I/II patients undergoing a 1-2 hour surgery. The EEG was collected before and during induction, maintenance and recovery of anesthesia using the 10/20 lead-system. A combination of fentanyl and propofol (± rocuronium) was used for induction and a Sevoflurane in air/O(2) mixture was administered through an endotracheal tube to achieve the steady minimum alveolar concentration (MAC). This study showed that 0 to 4 Hz signal power was most sensitive to the changes associated with induction of anesthesia whereas the 4 to 12 Hz power was important in classifying states during maintenance of anesthesia. Anesthesia also promoted heightened phase coherence in 8 to 16 Hz and 16 to 30 Hz ranges during maintenance and induction of anesthesia, respectively. Additionally, strong cross-frequency coupling between 7 to 20 Hz and 10 to 40 Hz was observed during anesthesia suggesting alteration of neural coding.

Background: Topical application of tranexamic acid to bleeding wound surfaces reduces blood loss in patients undergoing some major surgeries, without systemic complications. The objective of the present trial was to assess the efficacy and safety of the topical application of tranexamic acid on postoperative blood loss in patients undergoing primary unilateral total knee arthroplasty with cement. Methods: In a prospective, double-blind, placebo-controlled trial, 124 patients were randomized to receive 1.5 or 3.0 g of tranexamic acid in 100 mL of normal saline solution or an equivalent volume of placebo (normal saline solution) applied into the joint for five minutes at the end of surgery. The primary outcome was blood loss calculated from the difference between the preoperative hemoglobin level and the corresponding lowest postoperative value or hemoglobin level prior to transfusion. The safety outcomes included Doppler ultrasound in all patients and measurement of plasma levels of tranexamic acid one hour after release of the tourniquet. Results: Twenty-five patients were withdrawn for various reasons; therefore, ninety-nine patients were included in the intention-to-treat analysis. The postoperative blood loss was reduced in the 1.5 and 3-g tranexamic acid groups (1295 mL [95% confidence interval, 1167 to 1422 mL] and 1208 mL [95% confidence interval, 1078 to 1339 mL], respectively) in comparison with the placebo group (1610 mL [95% confidence interval, 1480 to 1738 mL]) (p < 0.017). The postoperative hemoglobin levels were higher in the 1.5 and 3.0-g tranexamic acid groups (10.0 g/dL [95% confidence interval, 9.5 to 10.4 g/dL] and 10.1 g/dL [95% confidence interval, 9.8 to 10.5 g/dL], respectively) in comparison with the placebo group (8.6 g/dL [95% confidence interval, 8.2 to 9 g/dL]) (p < 0.017). With the numbers studied, there was no difference in the rates of deep-vein thrombosis or pulmonary embolism between the three groups. Minimal systemic absorption of tranexamic acid was observed. Conclusions: At the conclusion of a total knee arthroplasty with cement, topical application of tranexamic acid directly into the surgical wound reduced postoperative bleeding by 20% to 25%, or 300 to 400 mL, resulting in 16% to 17% higher postoperative hemoglobin levels compared with placebo, with no clinically important increase in complications being identified in the treatment groups. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

We hypothesized that a more accurate alignment of the tip of the drain tube with the upper esophageal opening would be achieved in adult patients, as confirmed by fibreoptic bronchoscopy, by placing the ProSeal™ laryngeal mask airway (PLMA) by means of guiding it over an Eschmann™ tracheal tube introducer, commonly know as a gum elastic bougie (GEB), that was previously inserted into the esophagus, rather than by placing the PLMA with a curved metal introducer (IT). Seventy-five adult elective surgery patients, whose airway management involved a PLMA, were randomly allocated to either the GEB- or IT-guided techniques. After inserting the PLMA, alignment of the tip of the drain tube relative to the esophageal opening was verified by a fibrescope introduced through the drain tube. Placing the fibrescope through the PLMA identified the glottic structures. The primary endpoint indicating the proper alignment of the tip of the drain tube of the PLMA with the upper esophageal opening was the ability to pass the fibrescope into the esophagus through the drain tube by a distance >35 cm without obstruction and the ability to simultaneously visualize the esophageal mucosa. The overall success rates of PLMA insertion were similar in the GEB and IT groups. However, the mean airway insertion times were longer with the GEB than with the IT-PLMA. The GEB group achieved proper alignment of the drain tube and the upper esophageal opening more frequently than the IT group (97% confidence interval (CI95) 91.5–100% vs 81% CI95 68.5–93.5% of subjects, respectively; P = 0.027). When the GEB was used to place the PLMA, the patients’ vocal cords were visualized more frequently than when the IT technique was used (100% vs 73% CI95 58.9–87.1% of subjects, respectively; P = 0.003). Fibreoptic bronchoscopy confirmed that GEB is superior to the IT technique in ensuring precise alignment of the tip of the drain tube of the PLMA with the upper esophageal opening. Accurate positioning may better preserve gastroesophageal drainage function of the PLMA.

High-dose opioid therapy can precipitate seizures; however, the mechanism of such a dangerous adverse effect remains poorly understood. The aim of our study was to determine whether the neuroexcitatory activity of high-dose morphine is mediated by selective stimulation of opioid receptors.Mice hippocampi were resected intact and bathed in low magnesium artificial cerebrospinal fluid to induce spontaneous seizure-like events recorded from CA1 neurons.Application of morphine had a biphasic effect on the recorded spontaneous seizure-like events. In a low concentration (10 microM), morphine depressed electrographic seizure activity. Higher morphine concentrations (30 and 100 microM) enhanced seizure activity in an apparent dose-dependent manner. Naloxone, a nonselective opiate antagonist blocked the proconvulsant action of morphine. Selective mu and kappa opiate receptor agonists and antagonists enhanced and suppressed the spontaneous seizure activity, respectively. On the contrary, delta opioid receptor ligands did not have an effect.The proseizure effect of morphine is mediated through selective stimulation of mu and kappa opiate receptors but not the activation of the delta receptor system. The observed dose-dependent mechanism of morphine neuroexcitation underscores careful adjustment and individualized opioid dosing in the clinical setting.

The perioperative management of the airway in patients with cervical spine disease requires careful consideration. In an observational prospective cohort study, we assessed the preoperative factors that may have influenced the anesthesiologists' choice for the technique of intubation and the incidence of postoperative airway complications. We recorded information from 327 patients: mean (+/-SD) age 51+/-15 year, 138 females and 189 males, for anterior surgical approach (n=195) and posterior (n=132). The technique of intubation used was awake fiberoptic bronchoscopy (FOB) in 39% (n=128), asleep FOB 32% (n=103), asleep laryngoscopy 22% (n=72), and other asleep 7% (n=24). Awake FOB was predominately chosen for intubating patients with myelopathy (45%), unstable/fractured spine (73%), and spinal stenosis (55%) but patients with radiculopathy had more asleep FOB (49%) (P

Emerging evidence suggests that cell-based remyelination strategies may be a feasible therapeutic approach for CNS diseases characterized by myelin deficiency as a result of trauma, congenital anomalies, or diseases. Although experimental demyelination models targeted at the transient elimination of oligodendrocytes have suggested that transplantation-based remyelination can partially restore axonal molecular structure and function, it is not clear whether such therapeutic approaches can be used to achieve functional remyelination in models associated with long-term, irreversible myelin deficiency. In this study, we transplanted adult neural precursor cells (aNPCs) from the brain of adult transgenic mice into the spinal cords of adultShiverer(shi/shi) mice, which lack compact CNS myelin. Six weeks after transplantation, the transplanted aNPCs expressed oligodendrocyte markers, including MBP, migrated extensively along the white matter tracts of the spinal cord, and formed compact myelin. Conventional and three-dimensional confocal and electron microscopy revealed axonal ensheathment, establishment of paranodal junctional complexes leading tode novoformation of nodes of Ranvier, and partial reconstruction of the juxtaparanodal and paranodal molecular regions of axons based on Kv1.2 and Caspr (contactin-associated protein) expression by the transplanted aNPCs. Electrophysiological recordings revealed improved axonal conduction along the transplanted segments of spinal cords. We conclude that myelination of congenitally dysmyelinated adult CNS axons by grafted aNPCs results in the formation of compact myelin, reconstruction of nodes of Ranvier, and enhanced axonal conduction. These data suggest the therapeutic potential of aNPCs to promote functionally significant myelination in CNS disorders characterized by longstanding myelin deficiency.

Regional anesthesia (RA) provides excellent anesthesia and analgesia for many surgical procedures. Anesthesiologists and patients must understand the risks in addition to the benefits of RA to make an informed choice of anesthetic technique. Many studies that have investigated neurological complications after RA are dated, and do not reflect the increasing indications and applications of RA nor the advances in training and techniques. In this brief narrative review we collate the contemporary investigations of neurological complications after the most common RA techniques.We reviewed all 32 studies published between January 1, 1995 and December 31, 2005 where the primary intent was to investigate neurological complications of RA.The sample size of the studies that investigated neurological complications after central and peripheral (PNB) nerve blockade ranged from 4185 to 1,260,000 and 20 to 10,309 blocks, respectively. The rate of neuropathy after spinal and epidural anesthesia was 3.78:10,000 (95% CI: 1.06-13.50:10,000) and 2.19:10,000 (95% CI: 0.88-5.44:10,000), respectively. For common PNB techniques, the rate of neuropathy after interscalene brachial plexus block, axillary brachial plexus block, and femoral nerve block was 2.84:100 (95% CI 1.33-5.98:100), 1.48:100 (95% CI: 0.52-4.11:100), and 0.34:100 (95% CI: 0.04-2.81:100), respectively. The rate of permanent neurological injury after spinal and epidural anesthesia ranged from 0-4.2:10,000 and 0-7.6:10,000, respectively. Only one case of permanent neuropathy was reported among 16 studies of neurological complications after PNB.Our review suggests that the rate of neurological complications after central nerve blockade is4:10,000, or 0.04%. The rate of neuropathy after PNB is3:100, or 3%. However, permanent neurological injury after RA is rare in contemporary anesthetic practice.

The effects of the volatile anaesthetic isoflurane on dendritic field excitatory postsynaptic potentials (fEPSP) were compared in hippocampal slices taken from young mature and old Fisher 344 rats. Application of isoflurane (1% v/v) to young brain slices produced minimal effects on the recorded fEPSPs. On the contrary, the same anaesthetic concentration depressed field responses obtained from old hippocampal slices by 42 +/- 6.8% compared with baseline values. Such increased sensitivity to anaesthetic action in the old slices was consistently observed with administration of higher isoflurane concentrations. The presynaptic afferent volley was unaffected by application of low or high anaesthetic concentration, suggesting that age-induced changes in nerve fibre conduction and probably nerve ending excitability are not involved in the increased vulnerability of old synapses to anaesthetic action. Other synaptic sites are probably involved in the mechanisms of age-dependent potentiation of anaesthetic suppression of synaptic transmission.

Hyperventilation should speed up elimination of volatile anaesthetic agents from the body, but hyperventilation usually results in hypocapnia. We compared recovery from isoflurane anaesthesia in patients allowed to recover with assisted spontaneous ventilation (control) and those treated with isocapnic hyperpnoea.Fourteen patients were studied after approximately 1 h of anaesthesia with isoflurane. Control patients were allowed to recover in the routine way. Isocapnic hyperpnoea patients received 2-3 times their intraoperative ventilation using a system to maintain end tidal PCO(2) at 45-50 mm Hg. We measured time to removal of the airway and rate of change of bispectral index (BIS) during recovery.With isocapnic hyperpnoea, the time to removal of the airway was markedly less (median and interquartile range values of 3.6 (2.7-3.7) vs 12.1 (6.8-17.2) min, P0.001); mean (SD) BIS slopes during recovery were 11.8 (4.4) vs 4.3 (2.7) min(-1) (P0.01) for isocapnic hyperpnoea and control groups, respectively. Isocapnic hyperpnoea was easily applied in the operating room.Isocapnic hyperpnoea at the end of surgery results in shorter and less variable time to removal of the airway after anaesthesia with isoflurane and nitrous oxide.

To report a non-fatal case of intraoperative venous air embolism (VAE) during an awake craniotomy. VAE presented with unusual clinical features. VAE during an awake craniotomy has not been reported frequently. The patient we describe presented with persistent coughing followed by tachypnea, hypoxia and reduction in end-tidal CO2 during dural opening while undergoing an awake craniotomy in the supine position. Cardiovascular variables were stable during the episode except for transient hypertension. Having ruled out airway obstruction and low cardiac output, we concluded that air embolism was the cause. The patient responded immediately to the standard treatment of air embolism and recovered without any complication. This case illustrates a VAE during an awake craniotomy and emphasizes the importance of early diagnosis in the management.

The objective of this study was to determine the effectiveness of two prophylactic approaches against the anticipated hypotension induced by propofol during rapid-sequence intubation. Thirty-six male or female nonpremedicated ASA class I-II patients aged 21-60 yr undergoing elective outpatient surgery were included in the study. Patients were randomly allocated to receive pre-induction ephedrine sulphate (70 micrograms x kg(-1)iv), pre-induction volume loading (12 ml x kg(-1) Ringer's lactate) or no treatment. Rapid-sequence intubation with cricoid pressure was then performed with propofol (2.5 mg. x kg(-1)) and succinylcholine (1.5 mg x kg(-1). The lungs were subsequently ventilated with 0.25-0.5% isoflurane in a 2:1 N2O/O2 mixture. Vecuronium was given once neuromuscular function had recovered from the succinylcholine. Heart rate and systemic arterial blood pressure were measured non-invasively before induction, after propofol administration and every minute for ten minutes after intubation. Pre-induction volume loading prevented the hypotension observed before surgical stimulation in control and ephedrine groups. Moreover, pre-induction volume loading was not associated with increases in heart rate after intubation as was ephedrine administration. The intubating conditions were excellent to satisfactory in most patients and the overall incidence of adverse events during intubation was mainly due to pain during injection of propofol. The present study showed that preoperative volume loading is more efficacious than pre-induction administration of ephedrine sulphate in maintaining haemodynamic stability during rapid-sequence induction with propofol and succinylcholine. In addition, propofol in combination with succinylcholine provides excellent conditions for rapid-sequence intubation.

Simultaneous assessment of synaptic activity and glutamate efflux in guinea pig hippocampal brain slices was made before, during and after a 10-min period of hypoxia. Spontaneous glutamate efflux was assessed by determining glutamate concentration in the superfusion medium at discrete times using high performance liquid chromatography (HPLC). Synaptic activity was assessed using extracellular recording of the evoked population spike in the CA1 region following stimulation of the Schaffer collateral pathway. Hypoxia decreased (P0.05) the amplitude of the population spike by 3 min and abolished it by 5 min. This was accompanied by an increase (P0.05) in glutamate concentration in the superfusate at 10 min. Following re oxygenation, the population spike returned to baseline amplitude by 5 min and was greater (P0.05) than baseline at 10 and 20 min of recovery. Glutamate concentration returned to baseline levels by 1 min of recovery. This experimental preparation can be used to explore the temporal relationship between glutamate efflux and synaptic activity during hypoxia. The results of this study indicate that, in the hippocampal CA1 region, post-synaptic elements are more sensitive than their presynaptic counterparts to hypoxia.