Summary

Background and objective: Changes in the middle latency auditory evoked response following the administration of opioids have been shown. However, it remains unclear as to whether these changes are due to a direct depressant effect of opioids on the middle latency auditory evoked response itself, or an indirect effect on account of their action in attenuating central nervous system arousal associated with noxious stimuli. By comparing changes in the middle latency auditory evoked response in intubated and non-intubated patients, receiving saline or remifentanil in different doses, this study attempts to answer this question.

Methods: Fifty-four patients were anaesthetized with isoflurane and nitrous oxide (0.9 MAC) and randomized to 1–6 groups. Groups 1–3 received a bolus injection of either saline 0.9%, low-dose remifentanil (1 μg kg−1) or high-dose remifentanil (3 μg kg−1) prior to intubation of the trachea. Groups 4–6 were not intubated following the bolus injection.

Results: Pa and Nb amplitudes of the middle latency auditory evoked response increased by 82% and 79% with intubation in the saline group (P < 0.005) and these changes were not seen in the patients given remifentanil. There was a significant linear trend for the reduction in Pa and Nb amplitude with increasing remifentanil dose (P < 0.05). In the absence of endotracheal intubation remifentanil had no effect on either the amplitudes or latencies of the waves Pa and Nb and there was no effect of dose. For the haemodynamic measurements remifentanil attenuated the pressor response to intubation (P < 0.001) and had a significant dose-related effect (P < 0.001) in the absence of intubation.

Conclusions: We demonstrated an effect of remifentanil on both the middle latency auditory evoked response and haemodynamic changes to endotracheal intubation. For the non-intubated patients there was only an effect of remifentanil on the haemodynamic measurements. This suggests that remifentanil has an effect on the middle latency auditory evoked response in attenuating the arousal associated with intubation of the trachea but has no effect in the absence of a stimulus.

Summary

Background and objective: Venous air embolism is a constant threat during neurosurgery performed in the sitting position. No large prospective study has compared the incidence of venous air embolism and associated hypotension between adults and children.

Methods: Four hundred and thirty patients (334 adults, 96 children) scheduled to undergo planned posterior fossa surgery in the sitting position (between January 1989 to December 1994) were studied with end-tidal carbon dioxide monitoring. Intraoperatively, a sudden and sustained decrease in end-tidal carbon dioxide tension of >0.7 kPa was presumed to be due to venous air embolism. Management during the episode was on the established guidelines. Hypotension (decrease in systolic arterial pressure of 20% or more from the previous level) was treated with crystalloids and/or a vasopressor.

Results: Capnometry detected a 28% incidence rate of air embolism in adults (93/334) and a 22% incidence rate in children (21/96) (P = 0.29). In both groups, the highest incidence rate of embolism took place during muscle handling (44% of adults versus 38% of children, P = 0.8). Embolic episodes were accompanied by hypotension in 37% of adults (34/93) and in 33% of children (7/21) (P = 0.98). To restore arterial pressure to pre-embolic levels, 53% of adults (18/34) and 43% of children (3/7) were administered vasopressors (P = 0.94). There was no intraoperative mortality. The surgical procedure on one adult was abandoned because of persistent hypotension following the embolic episode.

Conclusion: The incidence of venous air embolism and consequent hypotension is similar in adults and children.

Summary

Background and objective: The prognosis of diabetic patients after surgery remains controversial. Some suggest that the rates of death and complications today are almost identical in diabetic and non-diabetic patients within hospital stay or for 30 days postoperatively, whereas others suggest that diabetes still constitutes a major risk factor for both short-term (≤30 days) and long-term (>30 days) patients especially after major cardiac surgery. We examined the long-term postoperative mortality of diabetic patients undergoing major non-cardiac surgery to identify possible perioperative risk factors.

Methods: Data from 179 consecutive diabetic patients, who underwent major non-cardiac surgery at Herlev Hospital, Denmark, during a 12 month period, have been retrospectively analysed. Data were obtained from patient records and from The Danish National Health Register. The main outcome measure was postoperative mortality. Patients were followed for a maximum of 18 months.

Results: The median postoperative observation period was 10 months (range 0–18 months). Overall postoperative mortality was 24% (95% confidence interval (CI) 17–31%). One third of the fatalities occurred during the first 30 days. Ischaemic heart disease diagnosed before the operation was associated with an overall postoperative mortality of 44% (95% CI 29–58%), which was significantly (P < 0.03) higher than in diabetic patients without known cardiovascular disease. The major causes of death in 18 out of 39 (46%) patients were diseases of the cardiovascular system.

Conclusions: Diabetic patients undergoing major non-cardiac surgery seem to have a high mortality, often because of cardiovascular death. Future strategies should focus on implementing cardio-protective treatment during the perioperative period.

Summary

Background and objective: Sevoflurane and propofol reduce the extent of necrosis and improve neurological outcome in rodent models of cerebral ischaemia and reperfusion. However, the effects of these anaesthetics on programmed cell death (apoptosis) are unclear. The present study investigates whether sevoflurane and propofol affect the expression of apoptosis-regulating proteins after cerebral ischaemia in rats.

Methods: Thirty-two fasted male Sprague–Dawley rats were tracheally intubated and the lungs were ventilated (isoflurane and N2O/O2 anaesthesia). After surgical preparation, the animals were randomly assigned to one of the following groups: control (n = 8): fentanyl intravenous (10 μg kg−1 bolus and 25 μg kg−1 h−1 infusion) with N2O/O2; sevoflurane (n = 8): 2.0% sevoflurane (end-tidal concentration) and O2/air; propofol (n = 8): 0.8–1.0 mg kg−1 min−1 propofol intravenous and O2/air; sham-operated (n = 8): 25 μg kg−1 h−1 fentanyl intravenous and N2O/O2, no cerebral ischaemia. Ischaemia (30 min) was induced by unilateral common carotid artery occlusion plus haemorrhagic hypotension to a mean arterial pressure of 30–35 mmHg. Four hours after cerebral ischaemia the brains were removed and the expression of apoptosis-regulating proteins (Bax, Bcl-2, p53, Mdm-2) was determined using immunofluorescence and Western-blot analyses.

Results: The expression of the pro-apoptotic protein Bax was greater in control animals than in sevoflurane or propofol anaesthetized rats and than in sham-operated animals. The concentrations of Bcl-2, p53 and Mdm-2 were not changed 4 h after cerebral ischaemia.

Conclusions: In addition to the anti-necrotic effects of sevoflurane and propofol, these anaesthetics also reduce the concentration of the apoptosis-inducing protein Bax as early as 4 h after ischaemia.

Summary

Background and objective: In children, emergence agitation frequently complicates sevoflurane and desflurane anaesthesia. The effect of intravenous fentanyl 2.5 μg kg−1 was examined on the incidence of emergence agitation in children who received desflurane or sevoflurane after midazolam premedication and intravenous thiopental induction.

Methods: One hundred and twenty children (2–7 yr) undergoing adenoidectomy or tonsillectomy, or both, were studied. All children were premedicated orally with midazolam 0.5 mg kg−1. After intravenous induction with thiopental and atracurium to facilitate endotracheal intubation, patients were randomly assigned to one of four groups: Patients in Groups 1 and 3 received physiological saline solution, whereas patients in Groups 2 and 4 received intravenous fentanyl 2.5 μg kg−1 during induction. Anaesthesia was maintained with sevoflurane in Groups 1 and 2 and with desflurane in Groups 3 and 4. After discontinuation of the volatile anaesthetic, the times to tracheal extubation and response to verbal stimuli (emergence time), and emergence behaviours were recorded.

Results: The time to tracheal extubation was significantly shorter in Groups 3 (5.2 ± 1.7 min) and 4 (6.4 ± 2.1 min) than in Groups 1 (8.1 ± 2.1 min) (P = 0.0001 and 0.006, respectively) and 2 (8.8 ± 1.9 min) (P = 0.0001). The emergence time was significantly shorter in Group 3 (10.0 ± 3.9 min) than in Groups 1 (13.8 ± 4.9 min) (P = 0.017) and 2 (14.9 ± 4.1 min) (P = 0.003). The incidence rate of severe agitation was 13% in Groups 1 and 3, and 7 and 10% in Groups 2 and 4, respectively (P > 0.05).

Conclusions: After midazolam premedication and intravenous induction of anaesthesia with thiopental, administration of intravenous fentanyl 2.5 μg kg−1 did not provide any clinically significant benefit on emergence agitation in children who receive sevoflurane or desflurane anaesthesia.

Summary

Background and objective: To compare two techniques to achieve induction of anaesthesia for laparoscopic surgery. A single-breath vital capacity rapid inhalation induction with sevoflurane was compared to intravenous propofol. Their effects on haemodynamics and the QT interval of the electrocardiogram were assessed.

Methods: Forty-four ASA I–II patients scheduled to undergo elective laparoscopic gynaecological surgery were divided into two groups. In the sevoflurane group (Group S, n = 22), general anaesthesia was induced with a single-breath vital capacity rapid inhalation of sevoflurane 5% with nitrous oxide (N2O) 65% in O2 and then anaesthesia was maintained with sevoflurane 1–1.5% with N2O 65% in O2. In the propofol group (Group P, n = 22), general anaesthesia was induced with propofol 2 mg kg−1 intravenously and maintained with propofol 6 mg kg−1 h−1 . Systolic, diastolic and mean arterial pressures, heart rate and end-tidal CO2 values were recorded before anaesthesia (basic value), during the induction period (time X), at 10 min (time Y) and at 30 min (time Z) of CO2 insufflation in all patients. QT intervals were calculated using Bazett's equation.

Results: Systolic, diastolic and mean arterial pressure values during the induction period (time X) were lower than the basic value in both groups (P < 0.05). In Group S, QTc intervals were significantly longer during the induction period (time X) and at the tenth min of CO2 insufflation (time Y) than Group P (P < 0.05). Five patients at time X and two patients at time Y developed ventricular dysrhythmias, which improved spontaneously in Group S. In Group P, there was no significant difference in QTc intervals and only one patient developed a ventricular dysrhythmia at time Y.

Conclusions: Single-breath vital capacity rapid inhalation induction technique with sevoflurane can cause prolongation of the QT interval and dysrhythmias, compared with induction and maintenance of anaesthesia with propofol in laparoscopic surgery.

Summary

Background and objective: There are concerns over the intra-cuff pressure of the laryngeal mask and laryngo-pharyngeal morbidity. In a randomized study, the authors compared cuff-pressure changes in the LMA-Classic® and the new disposable Soft Seal® laryngeal mask during nitrous oxide anaesthesia.

Methods: Two-hundred adult patients were randomly assigned to a size 4 laryngeal mask in two equal-sized groups for airway management: (a) the re-usable LMA-Classic®, or (b) the new disposable Soft Seal® laryngeal mask. Anaesthesia was administered with fentanyl, propofol, nitrous oxide, O2 and sevoflurane. The cuff pressures, adjusted to 45 mmHg at insertion, were monitored continuously until the end of the operation without any further attempt to reduce cuff pressure. On removal of the laryngeal mask, any blood at all was considered positive. Patients were requested to report any sore throat at 2 and 24 h postoperatively.

Results: During nitrous oxide anaesthesia, cuff pressures increased in the LMA-Classic® group from 45 to 100.3 mmHg and from 45 to 46.8 mmHg in the Soft Seal® laryngeal mask group (P < 0.001). The incidence of sore throat was significantly higher at 2 h postoperatively when using the LMA-Classic®, although there was no difference at 24 h following the operation. Macroscopic blood was only seen on four occasions in the LMA-Classic® group (not significant).

Conclusions: During nitrous oxide anaesthesia, cuff pressure increases in the LMA-Classic® mask were significantly higher than those of the Soft Seal® laryngeal mask. Trauma to patients, as assessed by the incidence of sore throat in the early postoperative period was significantly higher in the LMA-Classic® group. Cuff pressures should be monitored during nitrous oxide anaesthesia when LMA-Classic® is used but to do so is of less importance when using the disposable Soft Seal® laryngeal mask.

Summary

Background and objective: To compare the perioperative effects of melatonin and midazolam given in premedication, on sedation, orientation, anxiety scores and psychomotor performance.

Methods: Exogenous administration of melatonin not only facilitates the onset of sleep but also improves its quality. A prospective, randomized, double-blind, placebo-controlled study was performed in 66 patients undergoing laparoscopic cholecystectomy. Patients were given melatonin 5 mg, midazolam 15 mg or placebo, 90 min before anaesthesia, sublingually. Sedation, orientation and anxiety were quantified before; 10, 30, 60 and 90 min after premedication; and 15, 30, 60 and 90 min after admission to the recovery room. Neurocognitive performance was evaluated at these times, using the Trail Making A and B and Word Fluency tests. The differences between the groups were analysed by ANOVA. Two-way comparisons were performed by Scheffé analysis. Sedation and amnesia were analysed by the χ2 test.

Results: Patients who received premedication with either melatonin or midazolam had a significant increase in sedation and decrease in anxiety before operation compared with controls. After operation, there was no difference in sedation scores of all groups. Whereas, 30, 60 and 90 min after premedication the melatonin and midazolam groups exhibited a significantly poorer performance in Trail Making A and B tests compared with placebo, there were no significant differences among the groups in terms of neuropsychological performance after the operation. Amnesia was notable only in the midazolam group for one preoperative event.

Conclusion: Melatonin premedication was associated with preoperative anxiolysis and sedation without postoperative impairment of psychomotor performance.

Summary

Background and objective: To examine the calibration of the prognostic system Acute Physiology and Chronic Health Evaluation Score (APACHE II) regarding hospital mortality and predicting weaning outcome after long-term mechanical ventilation of the lungs.

Methods: Prospective observational cohort study performed in a respiratory intensive care unit including 246 patients whose lungs were ventilated for 42.1 ± 37.8 (median 30) days in the referring hospital. APACHE II (24 h after admission to our respiratory intensive care unit) and the cause of respiratory failure, underlying disease, prior duration of mechanical ventilation and gender were recorded. The predictive power was evaluated with sensitivity and specificity for different cut-off points and summarized in a receiver operating characteristic curve.

Results: No difference was found between survivors (APACHE II 16.0 ± 4.3) and non-survivors (APACHE II 16.9 ± 5.1). In a mean time of 8.0 ± 10.3 days, 146 patients (59.3%) were successfully weaned (APACHE II 15.2 ± 3.5). One-hundred patients (40.7%) were considered unweanable (APACHE II 17.7 ± 5.3). Recalibration of APACHE II to predict weaning failure was possible, resulting in an area under the receiver operating characteristic curve (AUC) of 0.638. Furthermore the AUC improved to 0.723 by changing the weights of selected APACHE items and introducing external factors. Diagnostic accuracy fell from group with mechanical ventilation ≤25 days (AUC 0.770) to group with mechanical ventilation >50 days (AUC 0.517).

Conclusions: APACHE II did not predict hospital mortality after long-term mechanical ventilation of the lungs. Not the original APACHE II but a recalibrated and adapted APACHE II can be useful to predict weaning outcome in patients with less than 25 days of prior lung ventilation.

Summary

Background and objective: To determine if there is any significant difference between the effects of desflurane, isoflurane and sevoflurane on the QT interval, QT dispersion, heart rate corrected QT interval and QTc dispersion of the electrocardiogram.

Methods: The study was conducted in a prospective, double blind and randomized manner in a teaching hospital. Ninety ASA I patients, aged 16–50 yr, undergoing general anaesthesia for noncardiac surgery were studied.

Results: There was no significant change in QT intervals during the study in any group (P > 0.05). QT dispersion in the sevoflurane group 49 ± 14 ms vs. 37 ± 10 ms; in the desflurane group 55 ± 16 and 62 ± 21 ms vs. 35 ± 14 ms and in the isoflurane group 54 ± 26 and 59 ± 24 ms vs. 42 ± 19 ms were significantly increased at 3 and 10 min after 1 MAC of steady end-tidal anaesthetic concentration compared with baseline values (P < 0.05). QTc values in the sevoflurane group were 444 ± 24 and 435 ± 21ms vs. 413 ± 19 ms (P < 0.05), in the isoflurane group were 450 ± 26 and 455 ± 34 ms vs. 416 ± 34 ms (P < 0.05), in the desflurane group were 450 ± 26 and 455 ± 34 ms vs. 416 ± 34 ms (P < 0.05) at 3 and 10 min after reaching 1 MAC of anaesthetic concentration and significantly increased compared with baseline values. QTc dispersion increased significantly with sevoflurane 62 ± 14 ms vs. 45 ± 16 ms (P < 0.05); isoflurane 70 ± 36 ms at 3 min and 75 ± 36 ms at 10 min after reaching 1 MAC of anaesthetic concentration vs. 50 ± 24 ms (P < 0.05); desflurane 67 ± 25 ms at 3 min and 74 ± 27 ms at 10 min after 1 MAC concentration vs. 41 ± 22 ms (P < 0.05).

Conclusion: Sevoflurane, isoflurane and desflurane all prolonged QTd, QTc and QTcd but there were no significant intergroup differences.