European Society of Anaesthesiologists; 8th Annual Meeting with the Austrian International Congress; Vienna, Austria, 1-4 April 2000
Background and goal of study: The bispectral analysis of the EEG (BIS) measures the effects of drugs on the spontaneous activity of cortical and subcortical structures. Nociceptive stimuli transmitted by afferent pathways reach supraspinal sites and thus may modify the level of consciousness. However the BIS does not directly assess nociceptive responses resulting in a sympathetic discharge clinically reflected by hypertension and tachycardia. Our aim was to correlate the "depth" of anaesthesia using MAP and the BIS, during endotracheal intubation (EIT). A secondary goal was to evaluate the effects of alfentanil on thiopental requirements during EIT.
Materials and methods: Twenty ASA II-III patients (age 66-90 years) scheduled for knee replacement under general anaesthesia (GA) were studied. The Ethic Committee approved the protocol and all subjects gave informed consent. All patients received for induction of GA: midazolam (3 mg), lidocaine (1 mg kg−1), atracurium (0.3 mg kg−1) and thiopental until abolishment of the eyelid reflex. In addition, patients in group I (n = 10) received a bolus of 30 μg kg−1 of alfentanil, while those in group II (n = 10) had saline. We measured thiopental requirements, MAP, HR and BIS at: baseline (BAS), after IV induction (PRE-EIT) and five minutes afterwards (POST-EIT). Results were analysed by two way ANOVA followed by Student's-Newman-Keuls.
Results: The groups were comparable regarding ASA, demographic parameters as well as the basal values of BIS and MAP. TABLE
MAP similarly decreased at PRE-EIT (P < 0.01) in both groups. At POST-EIT, the MAP further decreased in Group I (P < 0.05), while returned to basal values in Group II. BIS values decreased in both groups (P < 0.01), but patients in Group II showed significantly lower values than Group I at all times (P < 9.05). thiopental requirements were significantly reduced in Group I. Correlation coefficients between MAP and BIS for groups I and II were 0.75 and 0.85 respectively.
Conclusions: Intravenous induction of GA induces comparable changes in MAP and BIS. Alfentanil decreased thiopental requirements, induced more changes in MAP and higher BIS values. The results show that cortical depression induced by thiopental is reflected in the BIS, while opioids do not affect this parameter.
The abstracts published in this supplement have been typeset from camera-ready copies prepared by the authors. Every effort has been made to reproduce faithfully the abstracts as submitted. However, no responsibility is assumed by the organisers for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of methods, products, instructions or ideas contained in the material herein. Because of the rapid advances in medical sciences, we recommend that independent verification of diagnoses and drug doses should be made.
Patient safety, equipment, monitoring and computers