Summary

Background and objective: Xenon may have favourable applications in the setting of cardiac surgery. Its advantages include a desirable haemodynamic profile as well as potential cardiac and neuroprotective properties. However, its low solubility may lead to enhanced diffusion into enclosed gas spaces. The purpose of this study was to compare the effects of xenon (Xe), nitrous oxide (N2O) and nitrogen (N2) on gas bubble size during cardiopulmonary bypass (CPB).

Methods: Rats were randomized to receive 70% Xe, 26% oxygen (O2), 4% carbon dioxide (CO2) (xenon group); 70% N2O, 26% O2, 4% CO2 (nitrous oxide group) or 70% N2, 26% O2, 4% CO2 (nitrogen group) during 90 min of normothermic CPB. Small gas bubbles (300–500 μL; n = 12 per group) were injected into a bubble chamber on the venous side of the bypass circuit. After 10 min of equilibration, they were removed for volumetric analysis.

Results: The increase in bubble size was 2 ± 2% with nitrogen, 17 ± 6% with xenon (P = 0.0192 vs. nitrogen) and 63 ± 23% with nitrous oxide (P = 0.0001 vs. nitrogen). The nitrous oxide group had significantly increased bubble size compared to the xenon group (P = 0.0001).

Conclusions: During CPB, xenon anaesthesia produced a small increase in gas bubble size compared to nitrogen. Nitrous oxide resulted in significantly larger bubbles compared to both nitrogen and xenon.

Summary

Background and objective: The aim of this study was to investigate any possible protective effect of ketamine in acute muscular ischaemia and reperfusion injury by measuring malondialdehyde using thiobarbituric acid assay in rats. Methods: Twelve female Wistar albino rats were anaesthetized with chloral hydrate and randomly assigned into two groups to receive ketamine 1 mg kg−1 min−1 or saline infusion. Blood and gastrocnemius muscle samples were obtained 10 min after onset of infusion, before ischaemia. Then, femoral arteries were clamped for 30 min. Blood and muscle samples were obtained at the 30th minute of ischaemia and 10 min after reperfusion. Results: Muscle malondialdehyde concentrations were 27.88 ± 2.45, 27.62 ± 3.98 before ischaemia, 32.10 ± 4.19, 30.77 ± 2.73 in the 30th minute of ischaemia and 44.34 ± 2.45, 34.83 ± 2.78 after reperfusion in saline and ketamine-treated rats, respectively (nmol g−1, mean ± SD). The muscle malondialdehyde level after reperfusion was lower in ketamine-treated rats compared to saline group (P < 0.002). Plasma malondialdehyde levels were 3.77 ± 0.16, 3.78 ± 0.18 before ischaemia, 3.81 ± 0.25, 4.00 ± 0.86 at the 30th minute of ischaemia and 4.00 ± 0.53, 3.94 ± 0.95 after reperfusion, respectively, in saline and ketamine-treated rats (μmol L−1, mean ± SD). The effect of ketamine on muscular malondialdehyde was not observed in concurrent plasma malondialdehyde levels. Conclusion: Ketamine was found to attenuate acute ischaemia–reperfusion injury in muscle tissue in rats (muscular protective). Ketamine may attenuate lipid peroxidation in muscle tissue in tourniquet-requiring manoeuvres.

Summary

Background and objectives: The On-Line Electronic Help (OLEH) is a point-of-care information system for anaesthesia providers prepared by the European Society of Anaesthesiologists. In this preliminary study the effect of the OLEH availability on the incidence of knowledge-based errors during the management of case scenarios and participants' subjective evaluation of the OLEH were evaluated. Methods: After a short training session, 48 anaesthesiologists (24 junior residents, 12 senior residents and 12 board-certified) were presented randomly with six computer screen-based case scenarios with, and six without, the option of using the OLEH. Two reviewers evaluated the answers independently according to preconfigured guidelines. Results: The availability of the OLEH was associated with higher scores in 11 of the 12 scenarios, and with a decrease in the incidence of critical errors in 10 scenarios. Time to task completion was increased in one scenario only when the OLEH was used. The degree of professional experience was associated with better scores in five of the scenarios and with a reduced occurrence of critical errors in three scenarios. Forty-two out of 48 participants stated that finding information in the OLEH software was easy and that the system was helpful in managing the scenarios. Conclusions: This preliminary study demonstrates the potential value of the OLEH in decreasing the number of knowledge-based errors made by anaesthesiologists. According to the encouraging results, the OLEH system is currently under evaluation using full-scale simulation scenarios in an operating room environment.

Trauma is often assumed to increase the risk of pulmonary aspiration of gastric contents. The 247 anaesthetists in the Trent region of England were surveyed by postal questionnaire to ascertain the current practice for identifying patients at risk of pulmonary aspiration of gastric contents following trauma. The response rate was 79%. The anaesthetists rated the reliability of several criteria when predicting ‘gastric safety’ and stated whether each criterion formed part of their clinical practice. Interval of eating to injury was the most used (88%) and highest rated criterion (4/5) followed by use of opioids. Presence or absence of bowel sounds was the least used (7%) and lowest rated criterion (0/5). Currently there is little evidence that the commonly used criteria accurately identify ‘at-risk’ patients. There is little evidence that trauma increases the risk of aspiration although a number of factors associated with trauma are known to delay gastric emptying.

Ondansetron 4 mg was compared with metoclopramide 10 mg for prevention of post-operative nausea and emesis in in-patients undergoing major gynaecological surgery in this double-blind, randomized, placebo-controlled, multicentre study. A total of 1044 patients received a single intravenous (i.v.) injection of study medication immediately before induction of anaesthesia. Nausea and emesis were assessed over the 24 h post-operative period. Significantly more patients who received ondansetron experienced no emetic episodes (44%) compared with those who received metoclopramide (37%, P=0.049) or placebo (25%, P<0.001). No nausea was experienced by significantly more patients who received ondansetron (32%) than with patients who received metoclopramide (24%, P=0.009) or placebo (16%, P<0.001). In addition, fewer emetic episodes, less severe nausea and a reduced need for rescue antiemetics were also observed with ondansetron (P<0.05 vs. metoclopramide and placebo). Metoclopramide and placebo-treated patients were also 1.5 times (95% CI 1.5–4.2) and 2.5 times (95% CI 1.1–2.0) more likely, respectively, to experience nausea post-operatively. Overall, ondansetron was the most effective antiemetic in this patient population.

Von Hippel-Lindau disease is a rare autosomal dominant disease with incomplete penetrance and variable expression and is characterized by diffuse haemangioblastomas of the central nervous system and viscera. The majority of the central nervous system lesions are located in the cerebellum. This report describes the successful management with epidural anaesthesia of a woman with a term gestation, von Hippel-Lindau disease and cerebellar haemangioblastoma.

Ambulatory surgery is growing worldwide. The challenge of providing anaesthesia for longer and more complex surgery in sicker and elderly patients is a reality. To maintain the safety and good outcomes of ambulatory anaesthesia, high-risk patients will need to be evaluated carefully. Anaesthetic techniques that use short-acting drugs and minimize postoperative morbidity and mortality should become the focus. Policies on management of postoperative pain, nausea, vomiting, voiding and discharge from hospital will maintain good outcome measures.

In order to elucidate temporal changes in airway reflex responses to prolonged tracheal intubation, 14 patients anaesthetized with sevoflurane were studied. In each spontaneously breathing patient with an endotracheal tube in place, the end-tidal concentration of sevoflurane was slowly decreased from the initial value of 1.3% until signs of airway irritation were observed. The value of end-tidal sevoflurane concentration at which the airway reflexes occurred (Tar)and the types of airway reflex response elicited at onset of airway reflex response were determined during the periods immediately before (presurgical period) and after surgery (post-surgical period), with an interval ranging from 2 to 7 h between the two periods. There was no significant difference in the values of Tar between the presurgical period(0.6±0.3%, mean±SD) and the post-surgical period(0.7±0.1%). There was a considerable difference in the type of airway reflexes elicited during the two different periods; the initial responses during the presurgical period were the apnoeic reflex and/or forceful expiratory efforts, whereas the initial response during the post-surgical period, in the majority of patients, was the swallowing reflex. Our results indicate that there may be adaptation mechanisms responsible for temporal changes in airway protective reflexes after prolonged endotracheal intubation in surgical patients.

Summary

Background and objective: To compare the onset of action, and quality of block, of lidocaine 2% with levobupivacaine 0.75% for sub-Tenon's block in patients undergoing cataract surgery. Methods: We performed a two-centre trial in 91 patients who were randomized to receive 4 mL of lidocaine 2% (n = 44) or levobupivacaine 0.75% (n = 47) for sub-Tenon's block, both with hyaluronidase 15 IU mL−1. Onset of akinesia was assessed every 2 min for 10 min. Numbers of patients requiring supplementary injections to achieve clinically satisfactory akinesia or rescue analgesia were recorded. Data were analyzed with Fisher's exact test, U-test and t-test where appropriate. Results were considered significant when P < 0.05. Results: The speed of onset was statistically significantly faster for lidocaine compared to levobupivacaine (3.02 vs. 5.06 min, P < 0.001). There was no statistical difference in number of patients requiring a supplementary injection of local anaesthetic (levobupivacaine 3 vs. lidocaine 0, P = 0.24), rescue analgesia with topical tetracaine (levobupivacaine 0 vs. lidocaine 2, P = 0.5), or ocular akinesia scores at the completion of surgery (lidocaine 1.4 vs. levobupivacaine 1.6, P = 0.12). Pain scores measured by a verbal analogue scale were not significantly different for injection, perioperatively or postoperatively. Conclusions: Both agents produce a rapid onset of anaesthesia when used for sub-Tenon's block. The difference between the two agents, although statistically significant, is not clinically important.

Summary

Background and objective: The level of performance in junior and senior anaesthetists was investigated after 24-h shift working and on-call duties. Methods: Pre- and post-duty psychomotor function, influence on response time, cognitive function and well-being in 23 individuals (13 junior and 12 senior anaesthetists) was assessed before and after 24-h in-house on-call duty. Subjective perception of tiredness and concentration abilities was estimated by applying a visual analogue scale. Results: The self-assessed tiredness prior to duty was high in both age groups and significantly increased in senior anaesthetists after night duty (P = 0.01). Post-duty impairment of concentration abilities was reported in both groups. Comparing results from pre- and post-duty psychometric testing showed a comparable decline in junior and senior anaesthetists as well. Assessment of burnout showed a significant lack of personal accomplishment in junior anaesthetists as compared to their older colleagues (P = 0.038). Senior anaesthetists judged their contribution to patient well-being significantly higher than did their younger colleagues (P = 0.035). Conclusions: Although tiredness and subjective impairment of concentration abilities was high in senior anaesthetists after 24-h in-house on-call duty, performance assessed by psychometric testing does not support the hypothesis that senior colleague's performance cannot keep up with routine hospital shift work.

Fibreoptic bronchoscopy is often used to diagnose tracheomalacia under local anaesthesia. However, in children, general anaesthesia may be required due to difficulty in obtaining co-operation. A 1-yr-old girl with a suspected congenital tracheomalacia was scheduled for diagnostic fibreoptic bronchoscopy. During induction of anaesthesia by inhalation of increasing concentration of sevoflurane, spontaneous breathing became irregular and a partial airway obstruction occurred. Because vecuronium relieved the airway obstruction, the airway was managed using a laryngeal mask. No further airway obstruction occurred during fibrescopy under controlled ventilation, but when spontaneous breathing resumed, marked airway obstruction occurred. The trachea was intubated immediately. Caution is required to manage the airway without tracheal intubation during general anaesthesia in the patient with tracheomalacia.

Routine motor nerve conduction studies measure latencies, conduction velocities and amplitudes of compound action potentials. These measurements can be very useful in defining the pathology, while they provide little insight into the underlying disease mechanisms. Increasingly, the technique of ‘threshold tracking’ is being used in research and clinical studies on large myelinated axons. Nerve excitability testing is a non-invasive approach in investigating the pathophysiology of peripheral nerve disorders, which determines the electrical properties of the nerve membrane at the site of stimulation. We have found evidence that in patients with critical illness polyneuropathy peripheral nerves are depolarized. The correlations with serum factors suggest that this membrane depolarization is related to endoneurial hyperkalemia and/or hypoxia. While other mechanisms of depolarization may well be involved, the degree to which potential-sensitive nerve excitability indices are related to serum potassium and bicarbonate suggests that other factors, independent of potassium and acid–base balance, are likely to be of relatively minor significance.