Canadian Journal of Anesthesia, Vol 44, 202-207, Copyright © 1997 by Canadian Anesthesiologists' Society

ARTICLES

Chronic cocaine administration does not modify haemodynamic responses to isoflurane anaesthesia in sheep

CM Bernards, C Kern and BF Cullen
Department of Anesthesiology, University of Washington School of Medicine, Seattle 98195-6540, USA. chrisb@u.washington.edu

PURPOSE: Cocaine use is epidemic in the developed world, resulting in numerous patients presenting for surgery and anaesthesia with a history of chronic cocaine exposure. The purpose of this study was to determine the effect of chronic cocaine exposure on the cardiovascular response to isoflurane general anaesthesia. METHODS: The changes in mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP) and systemic vascular resistance (SVR) with increasing concentration of isoflurane (1%, 1.7%, and 2.4% end tidal) were determined at baseline in six sheep. The animals then received a continuous cocaine infusion (0.2 mg.kg-1.hr-1) and twice daily cocaine boluses (4 mg.kg-1) for 17 days followed on day 18 by a cocaine binge consisting of eight cocaine boluses (4 mg.kg-1) administered at one hour intervals. The haemodynamic studies conducted at baseline prior to cocaine exposure were then repeated on days 15 and 18. RESULTS: Increasing concentrations of isoflurane produced the expected dose-dependent cardiovascular depression, but this was not altered by cocaine exposure. CONCLUSION: Although chronic cocaine exposure has been shown to increase isoflurane minimum alveolar concentration by 25% in sheep; chronic cocaine exposure does not result in tolerance of the cardiovascular depression produced by isoflurane.