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Aspects of Cardiothoracic Anaesthesia

Comparison of bispectral index during normothermic and hypothermic cardiopulmonary bypass: 020

Han, S.-H.; Ham, B.-M.; Kim, Y.-R.; Kim, C.-S.; Bahk, J.-H.; Oh, Y.-S.; Lee, J.-L.

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European Journal of Anaesthesiology: June 2004 - Volume 21 - Issue - p 19

Introduction: Because of the reports of improved myocardial performance, cardiopulmonary bypass (CPB) with systemic normothermia is being increasingly used in many institutions recently [1]. During hypothermic CPB anaesthetic requirements are reduced by hypothermia itself [2]. However, during normothermic CPB, anaesthetic requirements should not be changed, thus the anaesthetic requirements may be higher than that during hypothermic CPB. To investigate the difference in anaesthetic requirements, we performed a prospective, randomized study of bispectral index (BIS) changes in patients with either normothermic or hypothermic CPB.

Method: Patients scheduled for elective coronary artery bypass graft surgery were randomly allocated to a normothermic group (GN; n = 20) or hypothermic group (GH; n = 20). Anaesthesia was maintained with isoflurane (0.5-1.2% volume) and supplemented with fentanyl (0.1-0.3 μg kg−1 min−1). The fentanyl infusion rate and the concentration of isoflurane were not changed from the period 15 min before starting CPB and throughout CPB. In GH, hypothermia was induced with a target rectal temperature of 30°C. The anaesthesiologist in charge was blinded to BIS. Change in BIS, mean arterial pressure (MAP), and nasopharyngeal temperature were recorded at the following times: (1) pre-CPB; after induction when vital signs were stable, (2) CPB 10; 10 min after start of CPB, (3) CPB 60; 60 min after start of CPB, (4) CPB off; 30 min after weaning from CPB.

Results: There was no difference in patients' demographic data, duration of CPB or MAP nor in isoflurane concentration or fentanyl requirement between the two groups. In the follow-up, no patients could recall anything from the operation.

Table 1
Table 1:
Change in nasopharyngeal temperature (Temp) and BIS.

Discussion: During CPB, GN showed higher BIS values than GH. Our results suggest that during normothermic CPB, anaesthetic requirements may be greater than that of hypothermic CPB.

References:

1 Lichtenstein SV, Ashe KA, el Dalati H, et al. Warm heart surgery. J Thorac Cardiovasc Surg 1991; 101(2): 269-274.
2 Vitez TS, White PF, Eger EI. Effects of hypothermia on halothane MAC and isoflurane MAC in the rat. Anesthesiology 1974; 41(1): 80-81.
© 2004 European Society of Anaesthesiology