Summary

The place of sub-Tenon's block in ophthalmic surgery is now established. This block was introduced into clinical practice in the early 1990s as a simple, safe and effective technique. Since then, techniques have evolved, newer cannulae have been introduced and many complications, both minor as well as major, have been reported. This review deals with the recent developments in sub-Tenon's block.

Summary

Electromagnetic interference produced by wireless communication can affect medical devices and hospital policies exist to address this risk. During the transfer of ventilated patients, these policies may be compromised by essential communication between base and receiving hospitals. Local wireless networks (e.g. Bluetooth®) may reduce the ‘spaghetti syndrome’ of wires and cables seen on intensive care units, but also generate electromagnetic interference. The aim of this study was to investigate these effects on displayed and actual ventilator performance. Methods: Five ventilators were tested: Drager Oxylog 2000, BREAS LTV-1000, Respironics BiPAP VISION, Puritan Bennett 7200 and 840. Electromagnetic interference was generated by three devices: Simoco 8020 radio handset, Nokia 7210 and Nokia 6230 mobile phone, Nokia 6230 communicating via Bluetooth with a Palm Tungsten T Personal Digital Assistant. We followed the American National Standard Recommended Practice for On-Site, Ad Hoc Testing (ANSI C63) for electromagnetic interference. We used a ventilator tester, to simulate healthy adult lungs and measure ventilator performance. The communication device under test was moved in towards each ventilator from a distance of 1 m in six axes. Alarms or error codes on the ventilator were recorded, as was ventilator performance. Results: All ventilators tested, except for the Respironics VISION, showed a display error when subjected to electromagnetic interference from the Nokia phones and Simoco radio. Ventilator performance was only affected by the radio which caused the Puritan Bennett 840 to stop functioning completely. The transfer ventilators' performance were not affected by radio or mobile phone, although the mobile phone did trigger a low-power alarm. Effects on intensive care ventilators included display reset, with the ventilator restoring normal display function within 2 s, and low-power/low-pressure alarms. Bluetooth transmission had no effect on the function of all the ventilators tested. Conclusion: In a clinical setting, high-power-output devices such as a two-way radio may cause significant interference in ventilator function. Medium-power-output devices such as mobile phones may cause minor alarm triggers. Low-power-output devices such as Bluetooth appear to cause no interference with ventilator function.

Summary

Background and objective: Reducing postoperative mechanical ventilation in patients undergoing liver transplantation may have clinical and organizational advantages. On the basis of our experience, we here evaluate the possibility of practising immediate tracheal extubation in the operating theatre. Methods: In this prospective study, patients consecutively undergoing liver transplantation between 1 June 1999 and 31 May 2004 were extubated in the operating theatre at the end of surgery on the basis of standardized and universally accepted criteria, under conditions of haemodynamic and metabolic stability. Results: Two hundred and seven of the 354 patients (58.5%) were extubated immediately after the completion of the surgical procedure (mean time between end of surgery and extubation: 0.4 ± 1.4 min); two were re-intubated. In the last of the 5 yr of the study, the percentage of immediate extubations increased to 82.5%. During the study period, there was a progressive increase in the number of immediate extubations per individual member of the team of anaesthetists. The pre-transplant Child-Pugh severity of the underlying liver disease did not predict rapid extubation, but the Model for End-stage Liver Disease score of <11 did (receiver operator characteristic area under the curve = 0.61; P < 0.05). Conclusions: Immediate extubation after liver transplantation is possible in a substantial percentage of cases; confidence, habit and a spirit of emulation are decisive factors in encouraging anaesthetists to extend this practice to the largest possible number of patients. A successful immediate extubation may be an important indicator of perioperative quality of care in liver transplantation.

Summary

Background: In myasthenic patients, the time course of action of non-depolarizing neuromuscular blocking agents is prolonged and the sensitivity is increased. We used our antegrade perfused rat peroneal nerve anterior tibialis muscle model to investigate if this altered time course of effect and sensitivity can be explained by the decreased acetylcholine receptor concentration that is caused by the disease. Methods: Functional acetylcholine receptors were reduced by administration of α-bungarotoxin or by injecting monoclonal antibodies against rat acetylcholine receptors (experimental autoimmune myasthenia gravis). After induction of anaesthesia, the model was set up and perfusion of the tibialis anterior muscle with blood was started. After stabilization of the twitch, rocuronium or pancuronium were infused until 90% block was obtained. Twitch data and infusion data were recorded and used to calculate the time course of effect and potency. Results: The potency of neuromuscular blocking agents was increased and the offset of the neuromuscular block was prolonged in both the α-bungarotoxin groups and the experimental autoimmune myasthenia gravis groups compared to controls. Conclusion: This study shows that the increased sensitivity to neuromuscular-blocking agents in myasthenia gravis can be accounted for by a decreased number of acetylcholine receptors. It also shows that the antegrade perfused rat peroneal nerve anterior tibialis muscle model is a suitable model to study the effects of myasthenia gravis on the time course of effect of neuromuscular blocking agents.

Summary

Background and objectives: Increasing numbers of patients taking herbal medicine products are presenting for anaesthesia and surgery. Anaesthetists need to consider the perioperative implications of herbal medicines and should, therefore, have some knowledge of this subject. Methods: A postal questionnaire survey was sent to a random 5% of practising members of the Association of Anaesthetists of Great Britain and Ireland residing in the UK, to identify attitudes, practice and knowledge regarding herbal medicines. Results: From 341 questionnaires there were 221 replies, a 65% response rate. Ninety per cent stated that they seldom or never asked patients about herbal medicine usage, yet 65% felt that there could be potentially harmful effects of herbal medicines in the perioperative period. There was a very poor level of knowledge with respect to the current management of 10 well-known herbal medicines. However, 75% agreed that information about perioperative usage of herbal medicines is important, and 77% felt that herbal medicines should be in the undergraduate medical curriculum. Reading was the usual source of herbal medicine product information. Most (82%) felt their knowledge of herbal medicine products and the implications in patient care were inadequate. Conclusions: This sample of anaesthetists require education on herbal medicines. Suggestions for remedial action are given.

Summary

Background: In this double-blind randomized study, the analgesic effects of morphine alone and with methylprednisolone were examined in 72 patients undergoing arthroscopic knee surgery. Methods: At the end of arthroscopy, patients were allocated randomly to one of four groups to receive intra-articular administrations of saline, morphine 1 mg, morphine 5 mg or morphine 1 mg with methylprednisolone 40 mg. Preoperative and postoperative pain levels at rest and during movement (active flexion of the knee) were measured by a visual analogue scale (VAS). Postoperative analgesic requirements to alleviate pain were evaluated. Results: Pain scores were significantly lower for the patients who received 5 mg morphine and 1 mg morphine with 40 mg methylprednisolone than for those who received saline or 1 mg morphine. This was accompanied by a decrease in the postoperative consumption of analgesics and prolongation of the duration of pain relief. Conclusions: This study confirms that the analgesic effect of morphine given intra-articularly is dose dependent and that combination of methylprednisolone with morphine has an additive effect on analgesia.

Summary

Background and objective: MDA-MB-468 breast carcinoma cells respond to non-volatile anaesthetics such as propofol with an increased migration. Here we investigated the relationship between GABA-A receptor modulators, the mode of calcium oscillation and actin reorganization with regard to breast carcinoma cell migration. Methods: Expression of the GABA-A receptor was determined by Western blot analysis. Calcium-imaging experiments of individual MDA-MB-468 cells as well as visualization of the F-actin distribution were performed by confocal laser scanning microscopy. Cell migration was investigated in a three-dimensional collagen matrix by time-lapse video microscopy. The GABA agonist propofol was used in a final concentration of 6 μg mL−1. GABA-A receptor antagonist bicuculline (50 μmol) and selective L-type calcium channel blocker verapamil (5 μmol) were used to modulate the propofol effects. Results: A functional GABA-A receptor is expressed by MDA-MB-468 cells. Activation with propofol resulted in sustained increased intracellular calcium concentrations concomitant with actin reorganization and induction of migration in MDA-MB-468 cells. These propofol effects were completely blocked by verapamil. Spontaneous migration of MDA-MB-468 cells (64.4 ± 7.0%) was significantly increased by propofol to 85.0 ± 5.0%. MDA-MB-468 cells co-treated with propofol and verapamil showed a migratory activity of 63.0 ± 2.0% indicating that verapamil blocked the propofol effect. Similar results were achieved with the GABA-A receptor inhibitor bicuculline (control: 56.3 ± 8.5%; propofol: 80.5 ± 7.1%; propofol + bicuculline: 52.5 ± 8.6%). Conclusion: Activation of GABA-A receptor by propofol correlated with an increased migration of MDA-MB-468 breast carcinoma cells, mediated by calcium influx via L-type calcium channels and reorganization of the actin cytoskeleton.

Summary

Background and objective: Anaesthesia may affect the regulatory balance of postoperative immune response. The aim of this study was to investigate the effects of different volatile and non-volatile anaesthetic agents and particularly of clinically used agent combinations on the proliferation capacity and cytokine production of immune cells. Methods: Peripheral blood mononuclear cells from healthy donors were PHA-activated in the presence or absence of various concentrations of thiopental, propofol, fentanyl, sufentanil, sevoflurane, nitrous oxide and combinations of these anaesthetics. Cell proliferation was assessed by tritiated thymidine uptake. Interleukin-2 production and release of the soluble IL-2 receptor were determined by enzyme immunoassays and used as measures of lymphocyte activation. Results: Thiopental inhibited cell proliferation in a dose dependent manner (P < 0.001) and reduced sIL-2R release (2090–970 pg mL−1; P < 0.05). Propofol reduced sIL-2R release at the high concentration of 10 μg mL−1 (2220 pg mL−1–1780 μg mL−1; P < 0.05). Fentanyl and sufentanil did not compensate for or enhance the inhibitory effects of thiopental. Nitrous oxide, but not sevoflurane, reduced the proliferation of human peripheral blood mononuclear cells (P < 0.05). In combinations with thiopental or nitrous oxide, sevoflurane compensated the inhibitory effects of these two agents. Fentanyl, sufentanil, sevoflurane and nitrous oxide did not affect PHA-induced IL-2 and sIL-2 receptor release by human peripheral blood mononuclear cells. Conclusion: Thiopental and nitrous oxide have immunosuppressive activity. In contrast, sevoflurane may have a beneficial effect by alleviating the immunosuppressive effects of both substances.

Summary

Background and objective: The effects of bicarbonated Ringer's solution were evaluated and compared with those of acetated Ringer's, lactated Ringer's and Ringer's solutions in partially hepatectomized rabbits. Method: Animals were randomly divided into six groups (n = 6 in each group): a sham-operated group, an operated group without infusion, and four operated groups with infusions of each of the four Ringer's solutions. Each Ringer's solution was intravenously administered at 40 mL kg−1 h−1 for 1.5 h. Arterial blood gases, plasma magnesium concentrations and cardiovascular parameters were analysed. Results: The partial hepatectomy-induced decrement of base excess was inhibited by bicarbonated Ringer's solution more remarkably than by either lactated or plain solutions (P < 0.01). The alkalinizing effect of bicarbonated Ringer's solution tended to be more marked than that of the acetated solution but not significantly so. Plasma magnesium concentrations were well maintained by bicarbonated solution as compared to the other solutions (P < 0.01). Conclusions: These results suggest that bicarbonated Ringer's solution is the most suitable perioperative solution for metabolic acidosis and plasma electrolyte balance among the Ringer's solutions tested.

Summary

Background and objective: There are no data about the influence of anaesthetics on cardiovascular variables during pressure support ventilation of the lungs through the laryngeal mask airway. We compared propofol, sevoflurane and isoflurane for maintenance of anaesthesia with the ProSeal® laryngeal mask airway during pressure support ventilation. Methods: Sixty healthy adults undergoing peripheral musculo-skeletal surgery were randomized for maintenance with sevoflurane end-tidal 2%, isoflurane end-tidal 1.1% or propofol 6 mg kg−1 h−1 in oxygen 33% and air. Pressure support ventilation comprised positive end-expiratory pressure set at 5 cmH2O, and pressure support set 5 cmH2O above positive end-expiratory pressure. Pressure support was initiated when inspiration produced a 2 cmH2O reduction in airway pressure. A blinded observer recorded cardiorespiratory variables (heart rate, mean blood pressure, oxygen saturation, airway occlusion pressure, respiratory rate, expired tidal volume, expired minute volume and end-tidal CO2), adverse events and emergence times. Results: Respiratory rate and minute volume were 10–21% lower, and end-tidal CO2 6–11% higher with the propofol group compared with the sevoflurane or isoflurane groups, but otherwise cardiorespiratory variables were similar among groups. No adverse events occurred in any group. Emergence times were longer with the propofol group compared with the sevoflurane or isoflurane groups (10 vs. 7 vs. 7 min). Conclusion: Lung ventilation is less effective and emergence times are longer with propofol than sevoflurane or isoflurane for maintenance of anaesthesia during pressure support ventilation with the ProSeal® laryngeal mask airway. However, these differences are small and of doubtful clinical importance.