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Item does not contain fulltext This study aimed at assessing the effects of cognitive activity and mental task load on the correlation dimension of the human electroencephalogram (EEG). Three experimental conditions were created: a baseline condition and two cognitive task conditions, a calculation task and a time estimation task. The calculation task was supposed to induce a higher mental load than the time estimation task, which is regarded as a less complex one. This was verified by a subjective rating scale. All conditions differed significantly in subjective estimated task load. The correlation dimension appeared to be higher in both task conditions compared tot the baseline condition. A comparison of the two tasks indicated that the difference in correlation dimension between calculation and time estimation was also significant, with the highest value for calculation. Its is concluded that cognitive and mental activity is associated with a higher correlation dimension in the EEG. This implies that the correlation dimension is a sensitive parameter in the analysis of electrical brain activity.

Background: Prospective evaluation of the percutaneous tracheostomy by the guide wire dilating forceps (GWDF) technique. Methods: In 50 selected patients percutaneous tracheostomy with fiberscopic control was performed and evaluated. Results: Most percutaneous tracheostomies were performed without any adverse effect. No life-threatening complications or deaths were related to the procedure. The procedure was successful in 49 of 50 patients (98%). In 1 patient the procedure was converted to an open tracheostomy because significant bleeding occurred. Five perioperative complications, including this significant bleeding and four minor complications, occurred in 50 patients (10%). Early complications occurred in 6 of 48 patients (13%), including one significant bleeding and five minor complications. A subglottic stenosis occurred in 2 of 36 successfully decannulated patients (6%). In one case this was certainly due to prolonged endotracheal intubation. Conclusions: The GWDF technique is a safe and efficient bedside alternative to open tracheostomy. Fiberscopic control is recommended to increase the safety of the procedure. Although studies of late complications are necessary, it appears to be justifiable to consider percutaneous tracheostomy for patients who require tracheostomy.

The bispectral index, a value derived from the electroencephalogram, has been proposed as a measure of anaesthetic effect. The aim of the present study was to evaluate the bispectral index during midazolam-fentanyl anaesthesia for cardiac surgery for its possible role as a predictor of increases in systolic blood pressure during endotracheal intubation and sternotomy. After institutional approval 15 consenting patients, scheduled for elective cardiac surgery, were selected for the study. Anaesthesia was induced in all patients with a loading dose of fentanyl 7.5-10 micrograms kg-1, midazolam 0.15 mg kg-1 and pancuronium 0.1 mg kg-1. After a further bolus dose of fentanyl 10-12.5 micrograms kg-1 prior to the start of incision and sternotomy, maintenance infusion rates of fentanyl 4-6 micrograms kg-1 h-1 and midazolam 0.1 mg kg-1 h-1 were started and continued through surgery at the discretion of the anaesthetist and guided by the presenting clinical and haemodynamic responses. The control of anaesthesia was never based on the value of the bispectral index. The mean bispectral index value decreased from 95.7 (3.1) at base-line to 59.5 (12.0) after induction of anaesthesia and then remained below 70 throughout surgery. However, there was an important interindividual variability in bispectral index values despite standardized dosages of fentanyl and midazolam. There was no significant correlation between the bispectral index values in the pre-intubation and pre-incision period and the changes in systolic blood pressure during endotracheal intubation and sternotomy, respectively. In conclusion, the large intersubject variability in the bispectral index values should be investigated further in the light of the great variability in the clinical effects of midazolam and fentanyl. The lack of significant correlation between the bispectral index values and the haemodynamic responses suggest that the bispectral index, which is a helpful monitor of anaesthetic depth, is not a very reliable monitor of global anaesthetic adequacy during total intravenous anaesthesia with a combination of midazolam and fentanyl in cardiac surgical patients.

Background and Objectives The PENCAN 25-gauge spinal needle is a new pencil-point needle with an inner diameter of 0.32 mm resulting in a relatively high cerebrospinal fluid (CSF) flow. The PENCAN 25-gauge needle was tested for ease of identification of a successful dural puncture, the failure rate of spinal anesthesia, and the incidence of postdural puncture headache (PDPH). Methods In a multicenter trial, the needle was tested in patients undergoing spinal anesthesia. A questionnaire evaluated the characteristics of the dural puncture. A second questionnaire was used to assess postspinal side effects (PDPH, atypical headache, audiovisual disturbances). Results In 1,193 patients, dural puncture was evaluated as easy in 85.2%, as moderate in 6.2%, as difficult in 6.7%, and as impossible in 1.9%. Needle performance was assessed as excellent or satisfactory in 96.9%. In 95.9% of patients, CSF appeared within 2 seconds. A perceptible “click” was noticed in 78.4% of patients. In 1.9%, CSF could not be obtained, because of spine deformities, obesity, or bending of the needle. In 1,166 patients, postpuncture complaints were evaluated, involving 635 women (54.5%), 773 patients (66.3%) under the age of 50 years old, and 170 (14.6%) cesarean deliveries. The overall incidence of PDPH was 1.3% (n = 15). A bloodpatch was needed in five patients. After cesarean delivery the incidence of PDPH was 3.4%, all responding to conservative treatment. Atypical headache and isolated audiovisual disturbances occurred in 7.5% and 1.5% of patients, respectively. Conclusions A failure rate of 1.9% together with a 1.3% incidence of PDPH were comparable to other 25-gauge pencil-point needles. The rapid appearance of CSF and a perceptible “click” made prompt recognition of successful dural puncture possible. Reg Anesth Pain Med 1999: 24: 43–50.

To study the relationship between ischaemia-reperfusion and multiple organ dysfunction syndrome (MODS), a new anaesthesia method was required to be applied to C57BL/6 mice. These mice are also used in a well accepted, standardized model for MODS using intraperitoneally administered zymosan (zymosan induced general inflammation, ZIGI). The aim was to develop a new model for ischaemia-reperfusion with 6 h of anaesthesia. This and further specific requirements for the combination of ischaemia-reperfusion and the ZIGI method, made us select inhalational anaesthesia using isoflurane in oxygen. This study evaluates whether long-term anaesthesia confounds the results of ischaemia-reperfusion and the ZIGI model. In addition the benefits of using the analgesic buprenorphine were evaluated. Ischaemia was induced with a tourniquet around the hindlimb. Ischaemia and reperfusion were verified by imaging a radioactive tracer with a gamma-camera. It was established that anaesthesia with isoflurane in oxygen caused little perturbation of body temperature and respiratory rate. A survival rate of 89% without noteworthy influence on organs was obtained. Buprenorphine proved to provide adequate analgesia and had no influence on measured parameters. In our experimental setting, this model with long duration anaesthesia allowed us to induce ischaemia and reperfusion of the hindlimb without perturbation of measurements. It also allowed good exposure of the abdomen and facilitated combination with the ZIGI model.

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Combined coronary artery bypass grafting (CABG) and pneumonectomy has a high morbidity and mortality rate, especially when the right lung has to be removed. A patient is described who underwent a CABG operation through a midline sternotomy without the use of cardiopulmonary bypass (CPB), and a right pneumonectomy through a right lateral thoracotomy in one operative session. To our knowledge, this is the first case in which this operative strategy was employed. CABG operations without the use of CPB might put concomitant lung surgery in a new perspective.

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The value of surgical and chemical lumbar sympathectomy was studied in patients with critical lower-limb ischaemia without the option of vascular reconstruction. Clinical success rates, defined as improvement of ischaemia stage, and limb salvage rates were recorded for 76 limbs of 70 consecutive patients. Chemical lumbar sympathectomy patients were older and had more concomitant diseases than surgical lumbar sympathectomy patients. The short-term (6-week) success rate in 36 cases treated with surgical lumbar sympathectomy (44%) was better than in 40 cases treated with chemical lumbar sympathectomy (18%) (P = 0.01). The long-term (1-year) success rate was 47% for surgical lumbar sympathectomy and 45% for chemical lumbar sympathectomy (P = NS). The 1-year limb salvage rates were 61% for surgical lumbar sympathectomy and 58% for chemical lumbar sympathectomy (P = NS). Complications were minor in both groups. Lumbar sympathectomy still has a limited role in the treatment of critical limb ischaemia in patients without the option of vascular reconstruction. Both surgical and chemical lumbar sympathectomy can be performed with very little morbidity and may provide a benefit over the natural course of the arterial insufficiency.

Item does not contain fulltext Within the context of the discussion about rational polytherapy, we determined the effects of four anaesthetics on the binding of [H-3]t-butylbicycloorthobenzoate ([H-3]TBOB) to the GABA(A) receptor complex in the presence of several concentrations of GABA (gamma-aminobutyric acid), in order to build a molecular model that can describe and quantify the interactions between the compounds. The empirical isobole method revealed that GABA and the anaesthetics acted synergically in displacing [H-3]TBOB. This synergy could be described by a simple molecular model in which both GABA and the anaesthetics displaced [H-3]TBOB allosterically and in which GABA allosterically enhanced the binding of the anaesthetics. To get information about the interaction between GABA and anaesthetics, we used [H-3]TBOB as a tracer ligand. The model indicated that GABA enhanced the affinity of thiopental 3.0-fold, propofol 5.0-fold, the neuroactive steroids Org 20599 3.5-fold and Org 20549 13-fold. Insight into the molecular mechanism and strength of these interactions can help clinicians to choose therapeutically optimal drug and dose combinations: a step towards rational polytherapy.

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The acute effects of various doses of two selective serotonin reuptake inhibitors (fluoxetine and fluvoxamine) on thermal and electrical stimulation-induced pain were investigated in drug-naive Wistar rats. The hot-plate and the tail-flick test and the noxious-induced withdrawal test were used. The two drugs had no effects on heat-induced pain behavior. However, the two compounds enhanced the motor responses induced by noxious electrical stimulation. These data contrast to what is generally found for tricyclic antidepressants and suggest a modality specific pain system. Cardiac and blood pressure were also found to change, but these changes were not correlated to changes in nociception. Taken together, the data suggest that the acutely administered selective serotonin reuptake inhibitors may exacerbate an acute type of pain.

UNLABELLED To evaluate the relationship between the level of thoracic epidural injection and the extension of sensory blockade, we inserted radiopaque epidural catheters in 87 patients at the high (C7-T2, n = 28), mid (T3-5, n = 29) or low (T7-9, n = 30) thoracic levels. Fifteen minutes after the epidural administration of 60 mg of lidocaine, the mean (+/- SD) sensory block extension varied from 5.4 +/- 3.1 to 7.7 +/- 1.8 segments. The level of epidural puncture was a statistically significant factor in determining the cranial and caudal borders of sensory blockade (P = 0.0001, analysis of variance), but in determining for the total number of segments blocked. The number of blocked dermatomes located cranially of the puncture level increased significantly with descending injection site (P = 0.0001). We acquired chest radiographs in 61 patients to determine epidural catheter tip position. Direction of the epidural catheter tip was not a significant factor in determining the extension or borders of sensory blockade. We conclude that the extension of sensory blockade in thoracic epidural anesthesia is not influenced by the level of epidural puncture or catheter tip direction. There is, however, a more cranial spread of sensory blockade in the low thoracic region compared with the high thoracic region. IMPLICATIONS After evaluating the extension and pattern of sensory blockade in high, mid, and low thoracic epidural analgesia, the authors suggest that it is safe to use similar dosage regimens in all three regions, and that in high thoracic epidural analgesia, it is important to insert the epidural catheter at the level of the intended cranial border of blockade.

Background Long-term postoperative cognitive dysfunction may occur in the elderly. Age may be a risk factor and hypoxaemia and arterial hypotension causative factors. We investigated these hypotheses in an international multicentre study. Methods 1218 patients aged at least 60 years completed neuropsychological tests before and 1 week and 3 months after major non-cardiac surgery. We measured oxygen saturation by continuous pulse oximetry before surgery and throughout the day of and the first 3 nights after surgery. We recorded blood pressure every 3 min by oscillometry during the operation and every 15–30 min for the rest of that day and night. We identified postoperative cognitive dysfunction with neuropsychological tests compared with controls recruited from the UK (n=176) and the same countries as study centres (n=145). Findings Postoperative cognitive dysfunction was present in 266 (25·8% [95% CI 23·1–28·5]) of patients 1 week after surgery and in 94 (9·9% [8·1–12·0]) 3 months after surgery, compared with 3·4% and 2·8%, respectively, of UK controls (p

Genetically-determined regional differences in the GABA-ergic make-up of the brain exist in two lines of Wistar rats viz.: apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) Wistar rats. Propofol is a GABA-mimetic general anesthetic. This study compared the responses to propofol in APO-SUS and APO-UNSUS rats. Propofol induced a higher incidence of involuntary muscular contractions and oral movements, but a lower incidence of grooming, in APO-SUS rats than in APO-UNSUS rats. Reflex inhibition and narcosis, being defined as the behavior marked by both full absence of purposeful movements and by complete loss of righting reflexes, after propofol did not differ between the two lines. APO-SUS rats had less variation of the heart rates and greater variations of diastolic arterial pressures in response to electrical stimulation than the APO-UNSUS rats, and these variations were reduced by increasing doses of propofol. Arterial pressures in APO-SUS rats were higher than in APO-UNSUS rats. Propofol caused a biphasic change in intra-arterial pressures and had the greatest effect in APO-SUS rats. Differences in cerebral GABA transmission, especially in the striato-nigro-collicular pathway, did not give rise to differences in the effect of propofol on narcosis and hindlimb withdrawal reflex. In contrast, these differences in GABA transmission were accompanied by line-specific differences in effect of propofol on certain behavioral and cardiovascular parameters.

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We compared the effects of the Brain laryngeal mask airway with a tracheal tube on intra-ocular pressure. Propofol was used as induction agent and atracurium as relaxant. Twenty-six patients with normal intra-ocular pressure undergoing cataract surgery were randomly allocated to two groups. Group A (n = 13) had a laryngeal mask airway inserted and Group B (n = 13) had a tracheal tube inserted. Intra-ocular pressure was measured just before insertion of the airway, 20 s after insertion and at 2 min. In the laryngeal mask airway group there were no significant changes in mean intra-ocular pressure. In the tracheal tube group there was a significant rise in mean intra-ocular pressure at 20 s (p = 0.0056) which returned to pre-insertion levels at 2 min. We conclude that the laryngeal mask airway continues to have advantages over the tracheal tube for ophthalmic surgery despite the use of propofol and atracurium as anaesthetic agents.

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he use of pins to stabilize the head of neurosur- gical patients in a Mayfield head holder causes a painful stimulus that may increase the arterial blood pressure and heart rate (1). To blunt this hemo- dynamic response, several approaches are possible, based on either the IV administration of drugs or the application of local anesthesia. The IV use of alfentanil 2-3 min before applying the Mayfield head holder is effective (2). Although Doblar et al. (2) could not dem- onstrate any effect, a bolus dose of thiopental is also used, but this can cause hemodynamic instability. Lo- cal injection of lidocaine into the scalp where the skull pins are placed is also effective (2), but it poses the problem that the anesthesiologist must know exactly where the surgeon will place the skull pins. Reposi- tioning of the Mayfield head holder also requires ad- ditional injections of a local anesthetic. Pinosky et al. (3) showed that a full scalp block effectively blunts the hemodynamic response to head pinning. They used bupivacaine to block the major nerves that innervate the scalp, as identified by bony landmarks (the supraorbital and supratrochlear nerves; the auriculotemporal nerves; the greater auric- ular nerves; and the greater, lesser, and third occipital nerves). After the publication by Pinosky et al. (3), we incorporated this technique into the clinical care of >50 neurosurgical patients with similar favorable re- sults. We now report a case of postoperative facial nerve block after intraoperative scalp block that rein- forces the need for care in using this procedure.

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