Background and objective: Monitoring the depth of anaesthesia by the bispectral index facilitates the titration of anaesthetic drugs during operation as well as assisting in early recovery. We planned to use this index to control the administration of anaesthetic agents in order to stabilize haemodynamics and promote recovery from anaesthesia in patients undergoing cardiac surgery with cardiopulmonary bypass.
Methods: Thirty adult patients undergoing valve replacement or coronary artery grafting under cardiopulmonary bypass were studied in a prospective, randomized, controlled study. Bispectral index monitoring was used in all patients. Patients received isoflurane anaesthesia and boluses of morphine: in the study group, anaesthetic depth was controlled using the bispectral index and clinical variables. In the control group, the bispectral index monitor could not be viewed by the anaesthesiologist. Bispectral index, mean arterial pressure and heart rate were noted every 5 min, and the incidence of hypotension, hypertension, tachycardia and bradycardia also noted. The time to recovery, when patients started obeying commands, was also recorded.
Results: Patients in the study group had significantly less hypertension and tachycardia (P < 0.05) than those in the control group. The time to recovery of consciousness was less in the study group than in the control group (n.s., P > 0.05). The bispectral index rose significantly in the control group at the time of institution and termination of cardiopulmonary bypass (P < 0.05).
Conclusions: Anaesthesia controlled by bispectral index monitoring decreases the incidence of haemodynamic disturbances and facilitates titration of anaesthetic agents during cardiopulmonary bypass and thus may assist recovery from anaesthesia.