Background and objective: The study was designed to compare the costs of propofol versus sevoflurane for the maintenance of the hypnotic component of anaesthesia during general anaesthesia, guided by the bispectral index, for gynaecological laparoscopic surgery.

Methods: Forty ASA Grade I—II female patients scheduled for gynaecological laparoscopy were randomly allocated to two groups. All patients received a continuous infusion of remifentanil (0.25 µg kg−1 min−1) for 2 min. Then anaesthesia was induced with propofol 1% at 300 mL h−1 until loss of consciousness. To guide the bispectral index between 40 and 60, Group 1 patients received propofol 10 mg kg−1 h−1 initially, which was increased or decreased by 2 mg kg−1 h−1 steps; Group 2 patients received sevoflurane, initially set at 2 vol.% and adjusted with steps of 0.2–0.4%. The time and quality of anaesthesia and recovery were assessed in two postoperative standardized interviews.

Results: Patient characteristics, the propofol induction dose, the bispectral index and the haemodynamic profiles during induction of anaesthesia, and its duration, were similar between the groups. In Group 1, 7.55 ± 1.75 mg kg−1 h−1 propofol and in Group 2, 0.20 ± 0.09 mL kg−1 h−1 liquid sevoflurane were used for maintenance. The cost for maintenance, including wasted drugs, was higher when using propofol (€25.14 ± 10.69) than sevoflurane (€12.80 ± 2.67). Postoperatively, recovery profiles tended to be better with propofol; however, the day after discharge no differences were found.

Conclusions: When applying the bispectral index to guide the administration of hypnotic anaesthetic drugs, propofol-based maintenance of anaesthesia was associated with the highest cost. A trend towards a better recovery profile was obtained with propofol. However, on the day after discharge, no differences in quality were observed.

Background and objective: Clinical sedation assessment becomes insufficient in deeply sedated patients. Bispectral index as a processed electroencephalogram parameter provides a continuous and observer-independent value reported to change with sedation. The aim of this prospective observational study was to determine the reliability and possible confounding factors of the bispectral index to assess sedation in surgical intensive care patients.

Methods: Following major surgery, bispectral index, body temperature and electromyographic activity of 44 ventilated patients were recorded. Sedation levels were assessed with Ramsay sedation score.

Results: Although bispectral index correlated with Ramsay sedation score (-0.64; P < 0.01) we found that in deeply sedated patients temperature instability and electromyographic activity increased bispectral index. Bispectral index correlated significantly with electromyographic activity (0.80; P < 0.01) and with an increase of body temperature (0.55; P < 0.01) not only in all patients but also in clinically deeply sedated patients (0.57; P < 0.01 and 0.46; P < 0.05).

Conclusions: Only under certain conditions, such as low muscular activity and body temperature stability, may the bispectral index be a useful addition to clinical scoring in the sedation assessment of critically ill patients.

This study investigated the changes in the hypnotic component of anaesthesia, estimated by the bispectral index of the electroencephalogram, during normothermic cardiopulmonary bypass. Twenty-six patients (20 men, 6 women), aged 61±11 years (Mean±SD) scheduled for cardiac surgery were premedicated with hydroxyzine and meperidine. Anaesthesia was induced and maintained with a computer-controlled continuous infusion (not adjusted for haemodilution) of sufentanil (effect site concentration 0.4–0.6 ng mL−1) and a manually adjusted continuous infusion of propofol (4.4±1.8 mg kg−1 h−1). Cardiopulmonary bypass was normothermic with moderate haemodilution. Bispectral index was measured with a referential montage before, 30 s, 1, and 3 min after cardiopulmonary bypass onset, before and after aortic cross-clamping, 30 min after cardiopulmonary bypass onset, before and after aorta cross-clamp release and before and after weaning from cardiopulmonary bypass. Bispectral index values were 48±8 before cardiopulmonary bypass onset, 50±10 before, and 48±8 after end of cardiopulmonary bypass (P=NS). No patient had increases in bispectral index values during cardiopulmonary bypass consistent with awakening. We conclude that with the anaesthetic regimen presented in this study bispectral index values do not change during normothermic cardiopulmonary bypass.

In this study, we have sought to establish whether N2O and ketamine alter the bispectral index during propofol–fentanyl anaesthesia. Fourteen surgical patients were randomly assigned to one of two groups: the N2O group (n=7) and the ketamine group (n=7). In both groups, anaesthesia was induced with propofol 1.5–2 mg kg−1 and fentanyl 2 μg kg−1 and maintained with propofol 5–7 mg kg−1 hr−1 to target the bispectral index between 40 and 50. After the bispectral index value had stabilized the propofol infusion rate was fixed. In the N2O group, the following concentrations of N2O were subsequently inhaled at 20-min intervals; 20, 40, 60 and 70%, and then N2O was terminated. In the ketamine group, ketamine (0.4 mg kg−1+1.0 mg kg−1h−1) was given. The bispectral index and 95% spectral edge frequency were recorded 20 min after each change in concentration of N2O or ketamine infusion. The bispectral index and 95% spectral edge frequency did not change significantly in the N2O group, but increased significantly from 44.1±0.7 and 16.0±0.5 to 58.6±1.4 and 19.5±0.3 (P <0.01), respectively, in the ketamine group. Additional N2O or ketamine did not decrease the bispectral index and 95% spectral edge frequency values. The depth of sedation should be assessed carefully using a bispectral index monitor when these anaesthetic agents are used together.

The bispectral index, a value derived from the electroencephalogram, has been proposed as a measure of anaesthetic effect. The aim of the present study was to evaluate the bispectral index during midazolam–fentanyl anaesthesia for cardiac surgery for its possible role as a predictor of increases in systolic blood pressure during endotracheal intubation and sternotomy. After institutional approval 15 consenting patients, scheduled for elective cardiac surgery, were selected for the study. Anaesthesia was induced in all patients with a loading dose of fentanyl 7.5–10 μg kg−1, midazolam 0.15 mg kg−1 and pancuronium 0.1 mg kg−1. After a further bolus dose of fentanyl 10–12.5 μg kg−1 prior to the start of incision and sternotomy, maintenance infusion rates of fentanyl 4–6 μg kg−1 h−1 and midazolam 0.1 mg kg−1 h−1 were started and continued through surgery at the discretion of the anaesthetist and guided by the presenting clinical and haemodynamic responses. The control of anaesthesia was never based on the value of the bispectral index. The mean bispectral index value decreased from 95.7 (3.1) at base-line to 59.5 (12.0) after induction of anaesthesia and then remained below 70 throughout surgery. However, there was an important interindividual variability in bispectral index values despite standardized dosages of fentanyl and midazolam. There was no significant correlation between the bispectral index values in the pre-intubation and pre-incision period and the changes in systolic blood pressure during endotracheal intubation and sternotomy, respectively. In conclusion, the large intersubject variability in the bispectral index values should be investigated further in the light of the great variability in the clinical effects of midazolam and fentanyl. The lack of significant correlation between the bispectral index values and the haemodynamic responses suggest that the bispectral index, which is a helpful monitor of anaesthetic depth, is not a very reliable monitor of global anaesthetic adequacy during total intravenous anaesthesia with a combination of midazolam and fentanyl in cardiac surgical patients.

The efficacy of anaesthetic premedication has been assessed using sedative scores or a visual analogue scale. However, in both it may be difficult to exclude evaluators’ subjectivity or a placebo effect. Plasma concentration of catecholamines may also be useful for the assessment of patient anxiety. Recently bispectral electro-encephalographic analysis has been developed, and the bispectral index monitor has been reported to give measurements which correlate well with the depth of sedation. In the present study, we have examined the relation between bispectral index values and plasma catecholamine concentrations after oral diazepam premedication. Twenty-eight patients scheduled for elective surgery were randomly assigned to one of two groups: diazepam premedication group (group D(+), n=14) and no premedication group (group D(−), n=14). The patients were premedicated orally with diazepam 10 mg and roxatidine 75 mg in group D(+), and with roxatidine 75 mg only in group D(−) 90 min before arrival in the operating theatre. After patients arrived in the operating theatre, the bispectral index monitor was applied. Venous blood samples(6 mL) were collected in the case of patients in group D(+) for the measurement of plasma catecholamines levels using high-performance liquid chromatography. The bispectral index level (mean±SD) in group D(+): 93.5±773.5 was significantly lower than that in group D(−): 96.1±1.8(P<0.05). There was a significant correlation between bispectral index and plasma norepinephrine levels (r=0.567, P<0.05). The present study suggests that the bispectral index monitor may detect the effect of oral diazepam premedication.