The aim of specific monitoring in neuroanaesthesia is to detect, as quickly as possible, intraoperative ischaemic insults so that the brain and the spinal cord may be protected from harmful and frequently inevitable events due to the type of surgery, patient positioning, haemodynamic changes or any intercurrent event. New monitors are being introduced into the operating theatre, but only a few are considered to be an absolute standard of care in neurosurgery, e.g. facial nerve monitoring for surgery of acoustic neuromas and recording of evoked potentials during repair of scoliosis. In the past decade, new monitoring devices have moved from the experimental stage to the operating theatre and although most are still in a phase of technological development and/or definition of their field of applicability they are being used as guides for clinical practice in those instances where cerebral well-being might be impaired. The metabolic consequences of hyperventilation, pharmacological electroencephalogram burst suppression, hypothermia, etc. can now be assessed in the operating theatre. Non-invasive monitoring is being rapidly integrated into our daily work because of its lack of secondary effects. Nevertheless, each new development is regarded as an addition rather than as a substitute for existing equipment. The perfect combination of monitors to provide essential information during an individual surgical procedure to influence a better patient outcome, is still uncertain and needs extensive clinical research.

Background and objective This study investigates the interaction of sevoflurane and nitrous oxide on EEG median power frequency of 2.5 Hz during surgery.

Methods Sevoflurane concentrations required for electroencephalographic median power frequency between 2 and 3 Hz were measured in 25 patients during gynaecological laparotomies. Nitrous oxide was randomly administered at 0, 20, 40, 60 and 75 vol%, subsequently two different concentrations in each patient. The data were analysed using isobolographic analysis together with previously published data on nitrous oxide-isoflurane, -enflurane, or -desflurane interaction.

Results The interaction is described by the equation: C volatile anaesthetic/C0 volatile anaesthetic + C N2O/C0 N2O = 1 (C is the concentrations for a drug combination to achieve the desired effect; C0 is the concentration for single drug use). The parameters are C0 isoflurane = 1.11 vol% (95% CI 1.03–1.19), C0 enflurane = 1.64 (1.52–1.77), C0 desflurane = 5.31 (4.92–5.73), C0 sevoflurane = 2.12 (1.96–2.29), C0 N2O = 174 (153–202). These parameters decrease by 6% (2.5–10) for every 10 years of patients’ age > 40 years.

Conclusions The interaction is compatible with additivity. The potency of nitrous oxide to substitute the volatile anaesthetics is less than anticipated from previously reported MAC values.

Background and objective The aim of the present study was to compare and assess the quality of analgesia, the safety and the side-effects after the use of a continuous, thoracic epidural infusion of sufentanil (5 μg h−1), 0.25% bupivacaine (10 mL h−1), 0.2% ropivacaine (10 mL h−1) alone or in combination in patients who had undergone major urological surgery. This prospective, randomized, double-blinded study investigated the efficacy of thoracic epidural infusions after major urological surgery.

Methods Patients received a 72-h continuous infusion␣(10 mL h−1) of 0.25% bupivacaine (B), 0.2% ropivacaine (R), 0.25% bupivacaine with 0.5 μg mL−1 sufentanil (BS), 0.2% ropivacaine with 0.5 μg mL−1 sufentanil (RS) or 0.5 μg mL−1 sufentanil only (S). The analysis included 109 patients.

Results The mean visual analogue scale (VAS) scores for pain were highest in the groups R and S (P < 0.001). The PaCO2 values were significantly higher in the groups RS and S (P = 0.003). Motor block occurred more frequently in the groups B and BS than in the other groups (P < 0.001). Sedation, nausea and pruritus were more common in the groups that received sufentanil.

Conclusions A continuous, epidural infusion with these drugs was safe and effective in our patients. The combination of 0.2% ropivacaine plus sufentanil appeared preferable because of the low incidence of motor block.

Background and objective Minimal- and low-flow anaesthesia (fresh gas flow below 1 L min−1) provide many advantages, including reduced cost, conservation of body heat and airway humidity. An airtight seal is essential between the airway device and the airway of the patient. Therefore, we investigated whether the airtight seal created by a laryngeal mask airway allows controlled ventilation of the lungs when the fresh gas flow is reduced to 0.5 L min−1 and compared this with an endotracheal tube.

Methods In a prospective clinical study, 207 patients were managed using a laryngeal mask or an endotracheal tube. After intravenous induction of anaesthesia and 15 min of high fresh gas flow, the flow was reduced to 0.5 L min−1. The breathing system was monitored for airway leaks, and the patients were assessed for complications after airway removal and postoperative discomfort.

Results Both the laryngeal mask and endotracheal tube allowed fresh gas flow reduction to 0.5 L min−1 in 84.7% and 98.3% of cases respectively (small leaks: 12% laryngeal mask, 1.7% endotracheal tube). Three patients with the laryngeal mask (3.3%l) had airway leaks that were too large to permit any reduction in the fresh gas flow.

Conclusions The use of the laryngeal mask airway was more likely to be associated with a gas leak than use of an endotracheal tube; however, if modern anaesthesia machines and monitors are used, in 96.7% of the patients managed with a laryngeal mask a reduction in the fresh gas flow to 0.5 L min−1 was possible. The incidence of coughing and postoperative complaints (sore throat, swallowing problems) was higher after use of an endotracheal tube.

Background and objective Perioperative hypothermia has been found to impair the coagulation cascade and to increase blood loss and transfusion requirements. The effect of concomitant in vitro heparinization on coagulation during hypo- and hyperthermic conditions has not been well defined.

Methods In the present study, activated partial thromboplastin time was examined in vitro at 33°C, 35°C, 37°C, 39°C and 41°C in normal human plasma in response to unfractionated heparin.

Results Hypothermia ≤ 35°C prolonged activated partial thromboplastin time by 10% compared with test temperatures at 37°C (P < 0.05). Hyperthermia alone had no effect. Unfractionated heparin (0.1–0.4 IU mL−1) increased activated partial thromboplastin time in a dose-dependent manner (by 189% at 0.4 IU mL−1, P < 0.05). Test temperatures of 33°C and 41°C increased heparin-induced prolongation of activated partial thromboplastin time. At a heparin concentration of 0.4 IU mL−1, hypothermia (33°C) and hyperthermia (41°C) prolonged partial thromboplastin time by 12% and 22%, respectively, compared with normothermic test temperature of 37°C within the heparin group (P < 0.05).

Conclusions These observations suggest that both hypo- and hyperthermia increase the response to heparin in vitro. Further studies are needed to identify the effect of patient’s body temperature on heparin activity and bleeding tendency in vivo.

Background and objective The intubating laryngeal mask (intubating laryngeal mask airway) was designed to facilitate blind intubation. Its value as an adjunct to fibreoptic laryngoscopy has not been evaluated. This study compares the intubating laryngeal mask airway with the standard laryngeal mask airway as conduits for fibreoptic laryngoscopy.

Methods The fibreoptic view of the laryngeal inlet was graded via both devices in 60 anaesthetized patients. The fibreoptic view through the intubating laryngeal mask airway was assessed after the central epiglottic elevator bar had been lifted out of the field of vision by an 8-mm Euromedical® tracheal tube, which was inserted to a depth of 18 cm. The fibreoptic view from the aperture bars of the laryngeal mask was recorded.

Results The vocal cords were viewed less frequently through the intubating laryngeal mask airway (52%) than through the laryngeal mask airway (92%) [difference = 40% (95% CI = 26% to 54%), P < 0.0001].

Conclusion The view of the laryngeal inlet is better through the laryngeal mask airway than through a tracheal tube inserted to 18 cm in the intubating laryngeal mask.

Background and objective Variability in blink duration was examined to see whether it was sensitive to sevoflurane sedation at 0.05 and 0.1 minimum alveolar concentration (MAC).

Methods Blinks were measured with an infrared transducer in eight subjects. Sedation was scored using a visual analogue scale (VAS).

Results At baseline, 0.05 and 0.1 MAC sevoflurane, respectively, the overall median value of blink duration and its interquartile range were 95 (80–110) ms, 198 (163–245) ms and 210 (130–980) ms. The median percentage of blinks exceeding 500 ms was 0% (0–0.7%), 33.3% (25.5–34.7%) and 25% (15.7–63.3%) respectively. Values during 0.05 and 0.1 MAC sevoflurane were significantly different from baseline (P < 0.035) but not from each other. Baseline visual analogue scales showed large intersubject variability. Compared with baseline, VAS scores were higher at 0.05 MAC (P < 0.035) but not at 0.1 MAC. After discontinuing sevoflurane, median blink duration returned to baseline with a recovery half-life of 2.6 min (R2 = 0.95).

Conclusion Blink duration is a sensitive measure of sevoflurane sedation even at 0.05 MAC.