Tramadol does not modify the Bispectral Index during anaesthesia with sevoflurane and remifentanil

The aim of this study was to investigate the effects of tramadol administered with ketorolac on the Bispectral Index (BIS) during anaesthesia with sevoflurane and remifentanil.

Forty-six adult patients, ASA I-III, scheduled for elective minor surgical procedures were studied. Patients were premedicated with remifentanil infusion 0.4 microg kg(-1) min(-1) and anaesthesia was induced 4-5 min later with propofol 1.5 mg kg(-1) and maintained with air-oxygen (FI(O(2)) 0.4), remifentanil 0.1-0.15 microg kg(-1) min(-1) and sevoflurane, adjusted to keep the BIS between 40 and 50. After 20 min of stable anaesthesia, the subjects were allocated randomly to receive i.v. tramadol 1.5 mg kg(-1) and i.v. ketorolac 0.3 mg kg(-1) (tramadol group) or saline (control group). BIS values, mean arterial pressure, heart rate and end-tidal carbon dioxide were recorded every 5 min for 20 min.

Mean BIS values after tramadol administration were not significantly different from those recorded in patients receiving saline throughout the period of observation. There were no patients who presented explicit recall of events under anaesthesia. No significant changes in mean arterial pressure, heart rate and end-tidal carbon dioxide were noted after tramadol injection.

Tramadol, given with ketorolac to prevent postoperative pain, during anaesthesia maintained with sevoflurane and remifentanil at BIS between 40 and 50, does not modify the BIS value.