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Background: Independent bench studies using specific ventilation scenarios allow testing of the performance of ventilators in conditions similar to clinical settings. The aims of this study were to determine the accuracy of the latest generation ventilators to deliver chosen parameters in various typical conditions and to provide clinicians with a comprehensive report on their performance., Methods: Thirteen modern intensive care unit ventilators were evaluated on the ASL5000 test lung with and without leakage for: (i) accuracy to deliver exact tidal volume (VT) and PEEP in assist-control ventilation (ACV); (ii) performance of trigger and pressurization in pressure support ventilation (PSV); and (iii) quality of non-invasive ventilation algorithms., Results: In ACV, only six ventilators delivered an accurate VT and nine an accurate PEEP. Eleven devices failed to compensate VT and four the PEEP in leakage conditions. Inspiratory delays differed significantly among ventilators in invasive PSV (range 75-149 ms, P=0.03) and non-invasive PSV (range 78-165 ms, P<0.001). The percentage of the ideal curve (concomitantly evaluating the pressurization speed and the levels of pressure reached) also differed significantly (range 57-86% for invasive PSV, P=0.04; and 60-90% for non-invasive PSV, P<0.001). Non-invasive ventilation algorithms efficiently prevented the decrease in pressurization capacities and PEEP levels induced by leaks in, respectively, 10 and 12 out of the 13 ventilators., Conclusions: We observed real heterogeneity of performance amongst the latest generation of intensive care unit ventilators. Although non-invasive ventilation algorithms appear to maintain adequate pressurization efficiently in the case of leakage, basic functions, such as delivered VT in ACV and pressurization in PSV, are often less reliable than the values displayed by the device suggest., (© The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Women in labour are considered at risk of gastric content aspiration partly because the stomach remains full before delivery. Ultrasonographic measurement of antral cross-sectional area (CSA) is a validated method of gastric content assessment. Our aim was to determine gastric content volume and its changes in parturients during labour under epidural analgesia using bedside ultrasonography., Methods: The cut-off value corresponding to an increased gastric content was determined by ultrasound measurement of antral CSA in six pregnant women in late pregnancy before and after ingestion of 250 ml of non-clear liquid. Antral CSA was then measured twice in 60 parturients who presented in spontaneous labour: when the anaesthesiologist was called for epidural analgesia catheter placement, and at full cervical dilatation. Patient-controlled epidural analgesia was performed with a solution of ropivacaine and sufentanil., Results: After liquid ingestion, antral CSA (mm(2)) increased from 90 (range, 80-151) to 409 (range, 317-463). A CSA of 320 was taken as cut-off value. The feasibility rate of antral CSA determination was 96%. CSA decreased from 319 [Q1 158-Q3 469] to 203 [Q1 123-Q3 261] during labour (P=2×10(-7)). CSA was >320 in 50% of parturients at the beginning of labour vs 13% at full cervical dilatation (P=0.006)., Conclusions: Bedside ultrasonographic antral CSA measurement is feasible in pregnant women during labour and easy to perform. The observed decrease in antral CSA during labour suggests that gastric motility is preserved under epidural anaesthesia. The procedure could be used to assess individual risk of gastric content aspiration during labour.

Background: Transversus abdominis plane (TAP) block has been reported to provide effective analgesia after lower abdominal surgery, but there are few data comparing ilioinguinal/iliohypogastric nerve (IHN) block with ultrasound-guided TAP block in patients undergoing inguinal hernia repair., Methods: Two hundred and seventy-three patients undergoing day-case open inguinal hernia repair with a mesh were randomly allocated to receive either ultrasound-guided TAP block or blind IHN block with levobupivacaine 0.5%, before surgery. Patients were monitored for visual analogue scale (VAS) scores at rest (in the post-anaesthesia care unit, and at 4 and 12 h) and at rest and during movement (at 24, 48 h, 3 and 6 months). Pain at 6 months was also assessed using the DN4 questionnaire for neuropathic pain., Results: Median VAS pain scores at rest were lower in the ultrasound-guided TAP group at 4 h (11 vs 15, P=0.04), at 12 h (20 vs 30, P=0.0014), and at 24 h (29 vs 33, P=0.013). Pain after the first 24 h, at 3 and 6 months after surgery, and DN4 scores were similar in both groups (P=NS). The proportion of patients with VAS >40 mm on movement at 6 months was comparable {18.2% [95% CI (12.2-26.1%)] vs 22.4% (15.8-30.6%) in the TAP and IHN groups, respectively, P=0.8}. Postoperative morphine requirements were lower during the first 24 h in the TAP block group (P=0.03)., Conclusions: Ultrasound-guided TAP block provided better pain control than 'blind' IHN block after inguinal hernia repair but did not prevent the occurrence of chronic pain.

Background: The fentanyl iontophoretic transdermal system (fentanyl ITS) enables needle-free, patient-controlled analgesia for postoperative pain management. This study compared the efficacy, safety, and ease of care of fentanyl ITS with patient-controlled, i.v. analgesia (PCIA) with morphine for postoperative pain management., Methods: A prospective, randomized, multicentre trial enrolled patients in Europe after abdominal or orthopaedic surgery. Patients received fentanyl ITS (n = 325; 40.0 microg fentanyl over 10 min) or morphine PCIA [n = 335; bolus doses (standard at each hospital)] for < or =72 h. Supplemental i.v. morphine was available during the first 3 h. The primary efficacy measure was the patient global assessment (PGA) of the pain control method during the first 24 h., Results: PGA ratings of 'good' or 'excellent' were reported by 86.2 and 87.5% of patients using fentanyl ITS or morphine PCIA, respectively (95% CI, -6.5 to 3.9%). Mean (sd) last pain intensity scores (numerical rating scale, 0-10) were 1.8 (1.77) and 1.9 (1.86) in the fentanyl ITS and morphine PCIA groups, respectively (95% CI, -0.38 to 0.18). More patients reported a system-related problem for fentanyl ITS than morphine PCIA (51.1 vs 17.9%, respectively). However, fewer of these problems interrupted pain control (4.4 vs 41.3%, respectively). Patients, nurses, and physiotherapists reported more favourable overall ease-of-care ratings for fentanyl ITS than morphine PCIA. Study termination rates and opioid-related side-effects were similar between groups., Conclusion: Fentanyl ITS and morphine PCIA were comparably effective and safe.

Postoperative symptoms and complications can be prevented by a suitable choice of anaesthetic and analgesic technique for specific procedures. The aim of analgesic protocols is not only to reduce pain intensity but also to decrease the incidence of side-effects from analgesic agents and to improve patient comfort. Moreover, adequate pain control is a prerequisite for the use of rehabilitation programmes to accelerate recovery from surgery. Thus, combining opioid and/or non-opioid analgesics with regional analgesic techniques not only improves analgesic efficacy but also reduces opioid demand and side-effects such as nausea and vomiting, sedation, and prolongation of postoperative ileus. Although all attempts to demonstrate that regional anaesthesia and analgesia decrease postoperative mortality are unsuccessful, there is evidence supporting a reduction in pulmonary complications after major abdominal surgery, and an improvement in patient rehabilitation after orthopaedic surgery. When such techniques are used, cost-benefit analysis should be considered to determine suitable analgesic protocols for specific surgical procedures.

Number needed to treat (NNT) values have been recommended and used to assess efficacy of analgesics for acute pain management. However, the data analysed come from a variety of procedures, which may potentially hinder the interpretation of the NNT value for specific procedures. We reanalysed available NNT data with acetaminophen in relation to the magnitude of surgical injury. Acetaminophen was less effective for pain relief after orthopaedic procedures than after dental procedures. The relative risk ratio for more than 50% pain relief, compared with placebo, was only 1.87 compared with 3.77 (P<0.05). Although NNT can give a valuable overview of efficacy, this concept is not necessarily applicable to all types of surgery. We suggest that estimates of NNT should be related to specific surgical procedures.

Background: Acetaminophen is commonly used for the management of perioperative pain. However, there is a marked discrepancy between the extent to which acetaminophen is used and the available evidence for an analgesic effect after major surgery. The aim of this systematic review is to determine the morphine-sparing effect of acetaminophen combined with patient-controlled analgesia (PCA) with morphine and to evaluate its effects on opioid-related adverse effects., Methods: MEDLINE and the Cochrane Library were searched to select randomized controlled trials which compared PCA morphine alone with PCA morphine plus acetaminophen administered orally or intravenously. Studies were evaluated for their quality based on the Oxford Quality Scale. Outcome measures were morphine consumption over the first 24 h after surgery, patient satisfaction and the incidence of morphine side-effects, including nausea and vomiting, sedation, urinary retention, pruritus and/or respiratory depression., Results: Seven prospective randomized controlled trials, including 265 patients in the group with PCA morphine plus acetaminophen and 226 patients in the group with PCA morphine alone, were selected. Acetaminophen administration was not associated with a decrease in the incidence of morphine-related adverse effects or an increase in patient satisfaction. Adding acetaminophen to PCA was associated with a morphine-sparing effect of 20% (mean, -9 mg; CI -15 to -3 mg; P=0.003) over the first postoperative 24 h., Conclusion: Acetaminophen combined with PCA morphine induced a significant morphine-sparing effect but did not change the incidence of morphine-related adverse effects in the postoperative period.

Background: Postoperative bladder distension and urinary retention are commonly underestimated. Ultrasound enables accurate measurement of bladder volume and thus makes it possible to determine the prevalence of postoperative bladder distension., Methods: Using ultrasound, we measured the volume of the bladder contents at the time of discharge from the recovery room in 177 adult patients who had undergone thoracic, vascular, abdominal, orthopaedic or ENT surgery., Results: Forty-four per cent of the patients had a bladder volume >500 ml and 54% of the 44%, who had no symptoms of bladder distension, were unable to void spontaneously within 30 min. The risk factors for urinary retention were age >60 yr (odds ratio (OR) 2.11, 95% confidence interval (CI) 1.01-4.38), spinal anaesthesia (OR 3.97, 95% CI 1.32-11.89) and duration of surgery >120 min (OR 3.03, 95% CI 1.39-6.61)., Conclusion: Before discharge from the recovery room it seems worthwhile to systematically check the bladder volume with a portable ultrasound device in patients with risk factors.

Background: Ketorolac is approved for the relief of postoperative pain but concerns have been raised over a possible risk of serious adverse effects and death. Two regulatory reviews in Europe on the safety of ketorolac found the data were inconclusive and lacked comparison with other non-steroidal anti-inflammatory drugs. The aim of this study was to compare the risk of serious adverse effects with ketorolac vs diclofenac or ketoprofen in adult patients after elective major surgery., Methods: This prospective, randomized multicentre trial evaluated the risks of death, increased surgical site bleeding, gastrointestinal bleeding, acute renal failure, and allergic reactions, with ketorolac vs diclofenac or ketoprofen administered according to their approved parenteral and oral dose and duration of treatment. Patients were followed for 30 days after surgery., Results: A total of 11,245 patients completed the trial at 49 European hospitals. Of these, 5634 patients received ketorolac and 5611 patients received one of the comparators. 155 patients (1.38%) had a serious adverse outcome, with 19 deaths (0. 17%), 117 patients with surgical site bleeding (1.04%), 12 patients with allergic reactions (0.12%), 10 patients with acute renal failure (0.09%), and four patients with gastrointestinal bleeding (0.04%). There were no differences between ketorolac and ketoprofen or diclofenac. Postoperative anticoagulants increased the risk of surgical site bleeding equally with ketorolac (odds ratio=2.65, 95% CI=1.51-4.67) and the comparators (odds ratio=3.58, 95% CI=1.93-6.70). Other risk factors for serious adverse outcomes were age, ASA score, and some types of surgery (plastic/ear, nose and throat, gynaecology, and urology)., Conclusion: We conclude that ketorolac is as safe as ketoprofen and diclofenac for the treatment of pain after major surgery.

The circulating blood volume (CBV) of critically ill patients may be difficult to estimate on the basis of history and physical examination. The aim of this study was to evaluate the ability of seven clinical signs and central venous pressure (CVP) to predict CBV in critically ill patients; CBV was evaluated with the [125I]human serum albumin technique. A scoring system was constructed using a combination of independence Bayes method and logistic regression. Sixty-eight patients constituted a 'model development' sample and 30 patients a validation sample. Thirty-six patients (53%) in the model development sample were found to have a low CBV (measured CBV at least 10% lower than the predicted mean normal CBV). Neither the haemodynamic variables monitored in ICU, nor the spot urinary sodium concentrations were different between patients with and without a low CBV. Individually, none of the clinical signs tested have a good positive or negative predictive value. For CVP, only extreme values seem to have clinical significance. To construct the score, the signs tested were ranked according to their discriminating efficacy. The probability of a low CBV was obtained by adding the weights of each sign tested and converting the score obtained into a probability. On a validation sample of 30 patients, the predictions are reliable as assessed by Z statistics ranging between -2 and +2. Our results suggest that: (1) individually, no clinical sign presented a clinical useful predictive value; and (2) a clinical scoring system may be helpful for the evaluation of CBV in critically ill patients.

We have investigated the relationship between the extent of spinal block and occurrence of sedation. In a first series of 43 patients, the distribution of sedation score (measured on the Ramsey scale) was related to the extent of spinal block (pinprick). In a second series of 33 patients, the relationship between sedation score and spinal block persisted after injection of midazolam 1 mg. This study confirmed that high spinal block was associated with increased sedation.

Clonidine, an alpha2 adrenoceptor agonist, has anti-hypertensive and anti-nociceptive effects. It is commonly used in association with local anaesthetics and opioids to enhance the quality and duration of extradural analgesia in the postoperative period, and to decrease the incidence of side effects. As a sole analgesic, it has seldom been used to relieve postoperative pain. The dose of extradural clonidine to achieve good pain relief without deleterious side effects remains undetermined. In order to address this problem, we performed a computer search via two well-known databases, Medline and Excerpta Medica, covering the period from 1985 to September 1997. One hundred and fifty-nine articles were retrieved of which 38 dealt with extradural clonidine and postoperative pain. All but 16 studies suffered from serious design flaws, such as lack of controls and/or randomization, or inadequate statistical analysis. The data from these studies were difficult to interpret because of the tremendous variation in variables, especially dose of clonidine, level of extradural injection, time of administration, type of anaesthesia, type of surgery, and reference and rescue drugs. The simultaneous extradural use of local anaesthetics and opioids further hindered data interpretation, and precluded any meta-analysis. Proposals for a standard study design are made to help comparison between studies involving extradural clonidine and postoperative pain.

We have conducted a double-blind, randomized study in two groups of 20 patients each, undergoing hip surgery during spinal anaesthesia, to compare the incidence of urinary retention after spinal morphine or clonidine. Patients received 0.5% spinal bupivacaine 15 mg combined with either clonidine 75 micrograms or morphine 0.2 mg. After operation, patients were examined for micturition, bladder distension, or both; when they failed to void, they received naloxone 0.2 mg, and if bladder distension persisted, a catheter was inserted. At 12 h, all patients in the morphine group but only five in the clonidine group had bladder distension, and at 24 h this was present in seven and one patient in the morphine and clonidine groups, respectively (P < 0.001). Naloxone was given in 16 and one, and a catheter was placed in one and six patients in the morphine and clonidine groups, respectively (P < 0.001). We conclude that spinal clonidine impaired bladder function to a lesser extent than morphine.

The postoperative period after major abdominal surgery is known to be a period of increased episodic oxygen desaturation. In order to assess the risk factors for episodic desaturation, we have studied 29 surgical patients using pulse oximetry during the preoperative night (Npre) when they received benzodiazepine premedication and breathed air, and also during the first three nights after operation when they received nasal oxygen supplementation. Modal oxygen saturation (SpO2) exceeded 95% during all nights studied. The time spent at less than 90% (t90) and 85% (t85) SpO2 and the average SpO2 nadir (SpO2, nadir) did not differ each night. Heart rate was greater (mean 90.1 (SD 16.6) vs 68.2 (12.0) beat min-1, P < 0.001) during the second night after operation (N2) than during Npre. Before operation, the number of desaturations, t90 and t85 correlated with pharyngeal hypertrophy (P = 0.003, P = 0.002, P = 0.001, respectively). At the same time, t90 and t85 correlated with body mass index (P = 0.02 and P = 0.05, respectively). During N2, t90 correlated with radiological lung consolidation (P = 0.05) and SpO2, nadir correlated with FEV1 (P = 0.03). We conclude that there are several mechanisms responsible for oxygen desaturation and that these mechanisms differ before and after surgery.

Twenty ASA I patients, undergoing thyroid surgery were allocated randomly to receive at the end of surgery either an isotonic saline solution or clonidine 2 micrograms kg-1 i.v. administered over 20 min. Oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured during recovery in patients breathing spontaneously with a head canopy system. Clonidine was found to attenuate the increase in VO2 and VCO2 associated with recovery from anaesthesia. The effect of clonidine was associated with a reduction in shivering. Sedative and analgesic properties of clonidine may also contribute to the reduction in metabolic demand during recovery from anaesthesia.

Clonidine is known to reduce anaesthetic requirements and improve haemodynamic stability when given as premedication. This study, of 46 ASA I-II patients undergoing thyroid surgery, was designed to assess if clonidine interferes with recovery from anaesthesia. Patients were allocated randomly to three groups to receive, 2 h before surgery, flunitrazepam 1 mg, clonidine 150 micrograms, or both drugs. Anaesthesia comprised thiopentone, alfentanil, isoflurane and 70% nitrous oxide in oxygen. Recovery from anaesthesia was assessed using a clinical score, electro-oculographic measurements and reaction times to auditory stimuli. Psychomotor tests were performed the day before surgery and 30, 60, 120 and 240 min after arrival of the patient in the recovery room. Psychomotor performance was decreased significantly after operation in the three groups (P less than 0.05) and returned to baseline at 240 min. There was no significant difference between the three groups. This study indicates that clonidine 150 micrograms orally before surgery does not delay recovery from anaesthesia.

After completion of abdominal aortic graft, 29 patients received an i.v. infusion of placebo (n = 16) or clonidine 7 micrograms kg-1 (n = 13) over 120 min in a double-blind study. Cardiovascular variables were measured and plasma samples obtained up to 5 h after arrival in the recovery room, for assay of noradrenaline, adrenaline, vasopressin and renin concentrations. Noradrenaline, adrenaline and vasopressin concentrations decreased in the clonidine group throughout recovery (P less than 0.001, 0.05 and 0.05, respectively, vs placebo). Heart rate was less in the clonidine group (P less than 0.01). There was no significant difference in mean arterial pressure between groups. Stroke volume was larger (P less than 0.01) and there were fewer episodes of hypertension (P less than 0.05) and tachycardia in the clonidine group. In addition, a reduction in the number of circulatory interventions (P less than 0.05) and episodes of shivering was noted in the clonidine group. Mean (SD) postoperative volume requirements were larger in the clonidine group (total postoperative input: clonidine 1462 (604) ml; placebo 1064 (348) ml (P less than 0.05]. These data are consistent with the observation that clonidine modifies endocrine and circulatory status after major surgery.

The effect of extradural morphine on antidiuretic hormone (ADH) secretion was assessed for the first 6 h after surgery in three groups of patients. Surgery was conducted under extradural bupivacaine: thereafter patients in group I (n = 6) received further injections of bupivacaine, patients in group II (n = 6) received an extradural injection of morphine and in patients in group III (n = 5) both bupivacaine and morphine, were administered extradurally. In group I, plasma ADH values remained unchanged throughout the study. In contrast, in the two groups of patients receiving extradural morphine a delayed and stepwise increase in plasma ADH concentration was documented. These results indicate that extradural morphine induces ADH secretion and suggest that this effect is the consequence of the migration of morphine to the brainstem.

The analgesic effect of extradural clonidine was evaluated in a double-blind study. In the recovery room, following orthopaedic or perineal surgery 20 ASA I and II patients were allocated randomly to two groups. The extradural clonidine (EC) group received clonidine 2 micrograms kg-1 in isotonic saline solution 15 micrograms ml-1. The extradural saline (ES) group received the equivalent volume of plain isotonic saline solution. Pain was evaluated by a visual analogue scale (VAS) at 15-min intervals for the first 2 h and subsequently at 30-min intervals for the following 4 h. Morphine 5 mg was given s.c. when patients complained of pain after extradural saline or clonidine. In the EC group, the mean (SD) maximum pain relief was 68.2 (24.1)% of the initial VAS score, but it was only 14.7 (25.2)% in the ES group. The mean duration of analgesia, before injection of morphine, was significantly longer in the EC group (210 (87) min) compared with the ES group (45 (27) min) (P less than 0.001). Drowsiness and moderate hypotension were observed in the EC group.

In order to assess the effect of spinal clonidine on tourniquet pain, 30 patients scheduled to undergo orthopaedic surgery under spinal anaesthesia were allocated randomly to two groups. Patients in group I (n = 15) received 0.5% isobaric bupivacaine 15 mg plus isotonic saline 1 ml. Patients in group II (n = 15) received 0.5% bupivacaine 15 mg plus clonidine 1 ml (150 micrograms). Sensory block was evaluated by pinprick and motor block with Bromage's scale. The presence of clonidine significantly prolonged the duration of sensory and motor block. Three patients in group I, but none in group II, experienced tourniquet pain. Hypotension and bradycardia were not worsened by spinal clonidine. The use of clonidine may be a useful technique to augment bupivacaine spinal block.