Background and objective: The aim was to examine the course of intraocular pressure after relaxation with different doses of cisatracurium.

Methods: The investigation was carried out as a prospective, randomized double-blind study in a crossover design in 30 postoperative patients with stable haemodynamic and respiratory function (ASA I and II). To exclude any disrupting factors, patients remained intubated and continuously sedated. Twenty patients received an intubation dose (2 × ED95) of cisatracurium (0.1 mg kg−1) compared with atracurium (0.5 mg kg−1). In a second series, 10 patients were given an effective dose, ED95 (0.05 mg kg−1), and a repeat dose (0.02 mg kg−1) of cisatracurium. The intraocular pressure was determined before (T0) as well as 1 (T1), 5 (T5), 10 (T10), 15 (T15), 20 (T20) and 45 (T45) min after bolus administration.

Results: Intraocular pressure decreased after an intubation dose of either cisatracurium or atracurium, and reached a minimum after 10 min (6.7 ± 2.2 and 7.9 ± 2.1 mmHg, respectively). There was no significant difference between either muscle relaxant (P = 0.27). When lower doses of cisatracurium (0.05 and 0.02 mg kg−1) were applied, the intraocular pressure also decreased, albeit to a lesser extent and with a delayed onset (8.4 ± 1.9 mmHg after 10 min, 9.9 ± 3.4 mmHg after 15 min). There was no significant difference between dosages (P = 0.44).

Conclusions: Cisatracurium is a useful drug in patients when a decrease of intraocular pressure is wanted and where muscle relaxation is necessary and acceptable.

An audit of post-operative nausea and vomiting (PONV) was undertaken in 935 female patients who used morphine patient-controlled analgesia (PCA) for pain relief after major gynaecological operations in a district general hospital. We investigated retrospectively five different antiemetic policies and a reference group without policy from January 1993 to July 1995. The department’s computerized audit system was used to analyse the observations. At the beginning of the audit, the incidence of nausea and vomiting was as high as 71.5%. But as a consequence of this audit, a departmental policy was adopted 3 years later, which had an incidence of PONV of only 51.7%. During this time the compliance with antiemetic protocols increased from 41% to 76%. There was significantly less PONV if an antiemetic protocol was followed (P=0.002). This emphasizes the importance of corporate involvement in the development, formulation and evaluation of departmental protocols if compliance is to be high. We conclude that audit as a corporate effort improves the acceptance of departmental protocols. This reduces PONV significantly irrespective of the type of antiemetic drug used.

Summary

Background and objective: In October 2000, we conducted a national postal survey of consultant day case anaesthetists in the UK to explore the range and variation in the practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). The survey was carried out as part of a larger study that comprised a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery). We report the findings of this national survey of adult urology and orthopaedic day case anaesthetic practice in the UK.

Methods: The survey used a structured postal questionnaire and collected data on the duration of the surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flows used for anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

Results: The overall response rate for the survey was 74% (63% for urology, 67% for orthopaedics). The survey indicated the following practice in adult urology and adult orthopaedic day case surgery: 6 and 12% used premedication; propofol was the preferred induction agent (96 and 97%) and isoflurane the preferred maintenance agent (56 and 58%); 32 and 41% used prophylactic antiemetics; 86 and 93% used a laryngeal mask.

Conclusions: This survey identifies the variation in current clinical practice in adult day surgery anaesthesia in the UK and discusses this variation in the context of current published evidence.

Anaesthesiologists administer a wide variety of drugs, including benzodiazepines, opioids, intravenous anaesthetic agents, volatile anaesthetic agents, muscle relaxants, local anaesthetics, and other drugs, especially those influencing the cardiovascular system. Sometimes a drug is chosen because of its better effect and/or side-effect profile. However, many of the drugs within each group have similar effect and/or side-effect profiles and differ mainly in their pharmacokinetics. The choice of one drug over another may then need to be based on differences in their pharmacokinetic profiles. Traditional predictors of onset of drug effect, such as time to a specified effect, are dose-dependent. Traditional predictors of offset of drug effect, such as ‘terminal half-life’, often have little clinical relevance. Newer descriptors offer significant advantages. The time to peak effect-site concentration is an informative dose-independent descriptor of the onset of drug effect following an intravenous bolus dose. The relevant decrement time (for continuous measures of drug effect) and mean effect time (for binary measures of drug effect) build upon the context-sensitive half-time concept, by considering the time required for the concentrations to decrease from one clinically relevant level of drug effect to another.

The development, application and interpretation of risk models is becoming an important activity in a number of surgical disciplines. In this paper, we discuss the many issues that arise when constructing a risk model, with particular reference to the development of a risk model for thoracic surgery. First, we briefly revisit the origins of risk modelling in cardiothoracic surgery.

Summary

Background and objective: The aim was to determine the effect of acute and chronic administration of 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, on the righting reflex ED50 and the minimum alveolar concentration during sevoflurane anaesthesia in rats.

Methods: 7-Nitroindazole was acutely (0, 50 and 100 mg kg−1) and chronically (0 and 150 mg kg−1 day−1, 4 days) administered to rats. After the preparation, the minimum alveolar concentration and the righting reflex ED50 were measured. The concentration of cGMP in the brain, cerebellum and spinal cord was also measured.

Results: Acute administration reduced the minimum alveolar concentration (50 mg kg−1, 58.8% (95% CI: 50.3–67.3%) of the baseline value, P < 0.01; 100 mg kg−1, 55.8 (46.9–64.7), P < 0.01) and the righting reflex ED50 (50 mg kg−1, 27.2 (17.2–37.2), P < 0.01; 100 mg kg−1, 14.3 (6.6–22.0), P < 0.01). Chronic administration did not reduce the minimum alveolar concentration; however, it reduced the righting reflex ED50 (65.3 (52.9–77.7), P < 0.01). Overall, the reduction in minimum alveolar concentration in the acute and chronic protocol did not correlate with that of the righting reflex ED50. 7-Nitroindazole (100 mg kg−1, acute) reduced the cGMP concentration within the cerebellum by 55.4%; however, it did not decrease concentrations in the brain or spinal cord.

Conclusions: Different mechanisms are responsible for the observed alterations to the minimum alveolar concentration and the righting reflex ED50 following treatment with 7-nitroindazole. The nitric oxide–cGMP pathway might play a less important role in the determination of minimum alveolar concentration than the righting reflex ED50.

Summary

Background and objective: To compare the effects of sevoflurane and desflurane anaesthesia on lipid peroxidation.

Methods: We studied 40 healthy patients undergoing elective laparoscopic cholecystectomy. Patients were randomly allocated to be anaesthetized either with sevoflurane (n = 20) or desflurane (n = 20). Anaesthesia was maintained with inspiratory concentrations of sevoflurane 1–1.5 MAC (n = 20) or desflurane (n = 20). Samples were taken for plasma malondialdehyde and superoxide dismutase assays before induction of anaesthesia, before skin incision and at the end of surgery. Alveolar cell samples were obtained from the lungs using the technique of protective blind bronchoalveolar lavage, after induction of anaesthesia and at the end of surgery for malondialdehyde and superoxide dismutase concentrations.

Results: Plasma malondialdehyde increased more after the administration of desflurane than after sevoflurane: after induction 5.9 ± 0.6 nmol mL−1 for desflurane vs. 3.8 ± 0.5 nmol L−1 for sevoflurane (P < 0.001); at the end of the surgery: 6.7 ± 0.4 nmol mL−1 for desflurane vs. 4.2 ± 0.3 nmol mL−1 for sevoflurane (P < 0.001). There was a small but significant increase in plasma superoxide dismutase concentration after desflurane – from 24.2 ± 1.2 to 24.9 ± 0.9U mL−1 after induction and 25 ± 1U mL−1 at the end of the surgery (P < 0.01) but no increase with sevoflurane. Malondialdehyde concentrations increased significantly in the cells obtained by protective blind bronchoalveolar lavage at the end of surgery in the desflurane group (from 0.3 ± 0.1 to 1.7 ± 0.2 nmol mL−1 (P < 0.001)), but not in the sevoflurane group. There were no significant differences between the two anaesthetics in the amounts of superoxide dismutase in the samples obtained by protective blind bronchoalveolar lavage.

Conclusions: Desflurane may cause more systemic and regional lipid peroxidation than sevoflurane during laparoscopic cholecystectomy in healthy human beings.

Summary

Background and objectives: During partial liquid ventilation perfluorocarbons are instilled into the airways from where they subsequently evaporate via the bronchial system. This process is influenced by multiple factors, such as the vapour pressure of the perfluorocarbons, the instilled volume, intrapulmonary perfluorocarbon distribution, postural positioning and ventilatory settings. In our study we compared the effects of open and closed breathing systems, a heat-and-moisture-exchanger and a sodalime absorber on perfluorocarbon evaporation during partial liquid ventilation. Methods: Isolated rat lungs were suspended from a force transducer. After intratracheal perfluorocarbon instillation (10 mL kg−1) the lungs were either ventilated with an open breathing system (n = 6), a closed breathing system (n = 6), an open breathing system with an integrated heat-and-moisture-exchanger (n = 6), an open breathing system with an integrated sodalime absorber (n = 6), or a closed breathing system with an integrated heat-and-moisture-exchanger and a sodalime absorber (n = 6). Evaporative perfluorocarbon elimination was determined gravimetrically. Results: When compared to the elimination half-life in an open breathing system (1.2 ± 0.07 h), elimination half-life was longer with a closed system (6.4 ± 0.9 h, P < 0.01), a sodalime absorber (5.0 ± 0.6 h, P < 0.01) or a heat-and-moisture-exchanger (4.5 ± 0.8 h, P < 0.01). The combination of all three methods (7.1 ± 0.8 h) showed no significant additional effects (P > 0.05) when compared to a closed system. Conclusions: Evaporative perfluorocarbon loss can be reduced effectively with closed breathing systems, followed by the use of sodalime absorbers and heat-and-moisture-exchangers.

Summary

The aim of this Review is to introduce anaesthesiologists to the basic physical principles that are important for their work. A better understanding of the underlying processes during anaesthesia is required for greater safety and efficiency. Relevant physical quantities are presented along with the area of anaesthesiology where they are used. This approach provides better targeting to the needs of practising anaesthesiologists. This text has been a part of a specialist course in anaesthesiology at the University of Ljubljana for some years. Current results show that both the students and the specialist anaesthesiologists now show a better understanding of the underlying physical principles required for their work and are more successful in fulfilling the needs of their practical work.

A 21-year-old female weighing 55 kg was anaesthetized for facial reconstruction. After an initial bolus of pancuronium 5 mg and top-up doses of 2 mg at 135 min and 1 mg at 290 min and 335 min, no further relaxant was given for 130 min at which time neuromuscular transmission appeared fully recovered with a full train-of-four twitches and a sustained response to 50 Hz stimulation of the posterior tibial nerve. Subsequently, a single dose of mivacurium 8 mg(2 X ED95) produced extended paralysis with no response to train-of-four stimulation for 85 min. The prolonged effect of mivacurium may have been because of inhibition of plasma cholinesterase by pancuronium. The serum cholinesterase activity 12 h after surgery was 0.38 units mL−1 (normal range 0.65–1.0 units mL−1). There was no evidence of atypical choylinesterase.