Luc Herregods

Effect of propofol on elevated intracranial pressure. Preliminary results

The effects of a bolus injection of propofol on mean intracranial pressure were studied in six adult, comatose patients who had severe head injuries. Propofol 2 mg/kg was given intravenously over 90 seconds when the mean intracranial pressure reached or exceeded 25 mmHg. Arterial blood gas values, heart rate and central venous pressure remained stable at all measurements. Arterial blood pressure decreased statistically significantly (p < 0.05) within one minute after propofol administration. The mean (SEM) intracranial pressure decreased statistically significantly (p < 0.05) at 30 seconds and at J and 2 minutes, from 25 (3) to 11 (4) mmHg. The cerebral perfusion pressure decreased statistically significantly from 92 (8) mmHg at all measurements (p < 0.05). The lowest value at 3 minutes was 50 (7) mmHg but in jour patients at that time the perfusion pressure was below 50 mmHg.

Propofol versus remifentanil for monitored anaesthesia care during colonoscopy

Background and objective: We conducted an open, prospective, randomized study to compare the efficacy, safety and recovery characteristics of remifentanil or propofol during monitored anaesthesia care in patients undergoing colonoscopy. Methods: Forty patients were randomly assigned to receive either propofol (1 mg kg−1 followed by 10 mg kg−1h−1, n = 20) or remifentanil (0.5 μg kg−1 followed by 0.2 μg kg−1 min−1, n = 20). The infusion rate was subsequently adapted to clinical needs. Results: In the propofol group, arterial pressure and heart rate decreased significantly from the baseline. These variables remained unchanged in the remifentanil group, but hypoventilation occurred in 55% of patients. Early recovery was delayed in the propofol group (P < 0.002). Recovery of cognitive and psychomotor functions was faster in the remifentanil group. Fifteen minutes after anaesthesia, the Digit Symbol Substitution Test score was 28.6 ± 12.8 versus 36.2 ± 9.4 and the Trieger Dot Test score was 25.6 ± 8.1 versus 18.7 ± 4.1 in the propofol and remifentanil groups, respectively (both P < 0.05). Patient satisfaction, using a visual analogue scale, was higher in the propofol group (96 ± 7 versus 77 ± 21, P < 0.001). Conclusions: Remifentanil proved efficient in reducing pain during colonoscopy. Emergence times were shorter and the recovery of cognitive function was faster with remifentanil compared with propofol. Remifentanil provided a smoother haemodynamic profile than propofol; however, the frequent occurrence of remifentanil‐induced hypoventilation requires the cautious administration of this agent.

Comparison of computer-controlled administration of propofol with two manually controlled infusion techniques

Ninety women were studied in order to compare dose requirements and quality of anaesthesia between target‐controlled infusion and two manually controlled infusion schemes for propofol administration: group I received target‐controlled infusion for induction (4 μg.ml−1 target blood concentration, increased by 2 μg.ml−1 after 3 min if consciousness not lost), groups II and III received an induction bolus of propofol at infusion rates of 1200 or 600 ml.h−1, respectively, until loss of consciousness. Anaesthesia was maintained with propofol target‐controlled infusion in group I or by constant rate infusion in the other two groups. Computer simulations were used to calculate blood and effect‐site propofol concentrations. Mean induction times (SD) were 78 (65) s in group I versus 51 (10) s and 62 (12) s in groups II and III, respectively (p < 0.05 between groups II and III). Mean induction doses were: 1.31 (0.44), 2.74 (0.56) and 1.77 (0.43) mg.kg−1 and mean maintenance doses were 13.4 (3.55), 9.32 (1.71) and 9.97 (1.53) mg.kg−1.h−1 in groups I, II and III, respectively (p < 0.05 between all groups). There was a lower incidence of apnoea in group I than in groups II and III. There were no significant differences between the groups in other objective parameters of anaesthetic quality studied. Computer simulations showed an ‘overshoot’ in propofol blood and effect‐site concentration with manual induction and significantly higher maintenance levels with target‐controlled infusion.

Cost-reduction analysis of propofol versus sevoflurane: maintenance of anaesthesia for gynaecological surgery using the bispectral index.

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 (&U20AC;25.14 ± 10.69) than sevoflurane (&U20AC;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.

Comparative study of limited intentional normovolaemic haemodilution in patients with left main coronary artery stenosis

Intentional normovolaemic haemodilution is a blood saving technique which can be performed when major blood loss is expected. Severe coronary artery disease and particularly left main stenosis are considered a contraindication for intentional normovolaemic haemodilution. The effects and complications of limited intentional normovolaemic haemodilution in patients with left main coronary artery stenosis scheduled for coronary artery bypass grafting were evaluated. Patients were randomly allocated to two groups: group A (n = 15) underwent limited intentional normovolaemic haemodilution to a haematocrit of 34%; group B(n = 15), no intentional normovolaemic haemodilution was performed. In both groups succinyl‐linked gelatin was used to maintain normovolaemia. Haemodynamic parameters were kept as constant as possible. In group A, a mean (SD) volume of 785 (250) ml of blood was withdrawn [range 500–1200 ml]. ST segment changes occurred on the ECG in three patients in each group. There were no statistically significant differences for frequency, maximum deflection and duration of ST‐segment changes. Limited intentional normovolaemic haemodilution can be performed safely in patients with left main coronary artery stenosis. In this study it was not associated with increased frequency, severity or duration of ST‐segment changes, or with arrhythmias or haemodynamic instability.

Influence of anaesthesia on defibrillation threshold.

Internal cardioverter–defibrillator implantation can be performed under local or general anaesthesia. Whether the technique of general anaesthesia influences the defibrillation threshold remains a matter of debate. We therefore compared, in a prospective, randomised clinical study, the effect of intravenous anaesthesia using propofol with inhalational anaesthesia using isoflurane on the defibrillation threshold in 68 patients scheduled for transvenous single‐lead internal cardioverter–defibrillator implantation. Defibrillation threshold was measured at implantation and at device testing 1 week and 1 month after implantation. Patients acted as their own controls. Neither the anaesthetic technique nor the duration of anaesthesia was associated with significant changes in the defibrillation threshold. We conclude that in this group of high‐risk patients, both types of anaesthesia are acceptable techniques for internal cardioverter–defibrillator implantation and testing.

EEG and SEMG monitoring during induction and maintenance of anesthesia with propofol

SummaryPropofol has been used as IV induction (2 mg/kg) and maintenance agent (150 µg/kg/min and 100 µg/kg/min after 30 min), combined with N2O/O2 in 16 premedicated (atropine 0.5 mg, Thalamonal 2 ml IM) and mechanically ventilated patients, having ear surgery or arthroscopy.Cranial biopotentials were analysed by 2 different techniques:1.The Anesthesia and Brain Activity Monitor (ABM Datex) providing the zero crossing frequency (ZXF) as a value for the mean frequency of the EEG signal during a considered time interval, the mean integrated voltage (MIV) as a mean value of the amplitude of the same EEG signal and the spontaneous electromyography of the frontal muscle (SEMG).2.The EEG trend monitor (rough signal, spectral analysis (S.A.), procentual display). The EEG changes, recorded during propofol anesthesia, are comparable with both techniques. Induction is characterised by a decrease in ZXF, caused by a procentual increase in the low frequency bands (the delta band represents more than 80% of the total power). During the perfusion period an increase in the power of the alpha band (10% to 40%) and a decrease in the delta band is noticed. The ZXF regains its original value. At the end of the procedure the ZXF increases (beta band to more than 30%).A correlation was looked for between the EEG changes and the propofol blood concentrations. The higher the propofol blood concentrations, the more pronounced the low frequency bands. The appearance of beta waves or a ZXF greater than 10 Hz indicates pending arrousal.

Ambulatory electrical external cardioversion with propofol or etomidate

STUDY OBJECTIVE To compare, in pairwise fashion, the effects of propofol and etomidate during ambulatory cardioversion and early recovery. DESIGN Clinical, prospective, randomized, blinded, monocenter, pairwise, comparative study SETTING OR and recovery area of the electrophysiological department, University Hospital Ghent, Belgium. PATIENTS 34 patients with atrial arrhythmia who were scheduled for repetitive electrical cardioversion, of whom 25 patients completed the study. INTERVENTIONS Nonpremedicated patients received during the first cardioversion either propofol (1 mg/kg) or etomidate (0.2 mg/kg) until loss of consciousness, followed by electrical external cardioversion. If after restoration of sinus rhythm for at least 1 day, atrial arrhythmia reoccurred, a second session was performed a week later, using the other induction drug. MEASUREMENTS Systolic and diastolic blood pressure values taken before drug administration, at loss of consciousness, 60 seconds after cardioversion, and awake; the number of shocks, the total amount of energy, the number of patients in which we failed to restore sinus rhythm, the time before opening eyes, answering simple questions and be able to sit, were all noted. Aldrete scores and the Steward postanesthetic recovery scores were noted every minute until 10 minutes after the external cardioversion. Recovery tests were performed and evaluated 5, 10, 15, and 20 minutes after energy delivery. MAIN RESULTS Number of shocks, amount of energy, and blood pressure values were comparable in both groups. Recovery times and Aldrete and Steward postanesthetic recovery scores showed a faster awakening in patients who were induced with propofol. Overall performance of the psychomotor test was better in the propofol group, and most pronounced at 10 and 15 minutes. CONCLUSIONS Etomidate and propofol are both useful during ambulatory external electrical cardioversion. The described doses maintain stable hemodynamic conditions in nonpremedicated patients. Recovery scores and psychomotor test indicate a faster recovery in the propofol group. However, no intergroup differences were noted at 20 minutes after the cardioversion. A safe discharge of all patients from the critical care unit or postanesthesia care unit to the ward can be considered after 30 minutes.

Retraining basic life support skills using video, voice feedback or both: A randomised controlled trial

INTRODUCTION The optimal strategy to retrain basic life support (BLS) skills on a manikin is unknown. We analysed the differential impact of a video (video group, VG), voice feedback (VFG), or a serial combination of both (combined group, CG) on BLS skills in a self-learning (SL) environment. METHODS Two hundred and thirteen medicine students were randomly assigned to a VG, a VFG and a CG. The VG refreshed the skills with a practice-while-watching video (abbreviated Mini Anne™ video, Laerdal, Norway) and a manikin, the VFG with a computer-guided manikin (Resusci Anne Skills Station™, Laerdal, Norway) and the CG with a serial combination of both. Each student performed two sequences of 60 compressions, 12 ventilations and three complete cycles of BLS (30:2). The proportions of students achieving adequate skills were analysed using generalised estimating equations analysis, taking into account pre-test results and training strategy. RESULTS Complete datasets were obtained from 192 students (60 VG, 69 VFG and 63 CG). Before and after training, ≥70% of compressions with depth ≥50 mm were achieved by 14/60 (23%) vs. 16/60 (27%) VG, 24/69 (35%) vs. 50/69 (73%) VFG and 19/63 (30%) vs. 41/63 (65%) CG (P<0.001). Compression rate 100-120/min was present in 27/60 (45%) vs. 52/60 (87%) VG, 28/69 (41%) vs. 44/69 (64%) VFG and 27/63 (43%) vs. 42/63 (67%) CG (P=0.05). Achievement of ≥70% ventilations with a volume 400-1000 ml was present in 29/60 (49%) vs. 32/60 (53%) VG, 32/69 (46%) vs. 52/69 (75%) VFG and 25/63 (40%) vs. 51/63 (81%) CG (P=0.001). There was no between-groups difference for complete release. CONCLUSIONS Voice feedback and a sequential combination of video and voice feedback are both effective strategies to refresh BLS skills in a SL station. Video training alone only improved compression rate. None of the three strategies resulted in an improvement of complete release.

A new transvenous internal cardioverter-defibrillator: Implantation technique, complications, and short-term follow-up

Twenty-four patients with ventricular fibrillation or sustained ventricular tachycardia underwent implantation of a new transvenous defibrillator. All patients had a device implanted without thoracotomy. High placement of a shock lead in the anonymous vein and inversion of the shock-wave polarity allowed avoidance of placement of subcutaneous patches. Implantation time decreased from 138 minutes for the first 12 patients to 82 minutes for the last 12 patients, with 4 and 11 subpectoral pockets, respectively. Three patients required a minor reintervention. No bleeding or infection occurred. One episode of pulmonary edema and one pulmonary embolism were seen in the postoperative course. No postoperative deaths were observed. During a mean follow-up period of 4.12 months, 58% of the 24 patients had symptomatic arrhythmic episodes, with shocks in 50% of the 24. Inappropriate shocks were delivered in three cases (atrial fibrillation and T-wave sensing). One episode was not terminated even with four internal shocks. One patient had ventricular fibrillation because of a sensing problem. By reprogramming of sensitivity, back-up pacing, and adjustment of drug therapy these arrhythmic complications could be prevented. Pectoral implantation of a cardioverter-defibrillator is easy and can be performed by cardiologists experienced in pacemaker implantation. Careful postoperative observation, reprogramming after the first spontaneous event, and prehospital discharge induction of ventricular fibrillation will prevent arrhythmic complications.