Cambridge Journals Online

Original Article

Regular tramadol use does not affect the propofol dose requirement for induction of anaesthesia

H. Kokkia1a2, J. Wennervirtaa3, M. Laisalmia1 and A. Vakkuria4 c1 a1 Kuopio University Hospital, Department of Anaesthesiology and Intensive Care, Kuopio, Finland a2 University of Kuopio, Department of Pharmacology and Toxicology, Kuopio, Finland a3 Helsinki University Hospital, Jorvi Hospital, Department of Anaesthesiology and Intensive Care Medicine, Helsinki, Finland a4 Helsinki University Hospital, Surgical Hospital, Department of Anaesthesiology and Intensive Care Medicine, Helsinki, Finland

Article author query Kokki H   Wennervirta J   Laisalmi M   Vakkuri A

Summary

Background and objectives An increased risk of awareness during general anaesthesia in patients receiving tramadol has been reported. We studied whether tramadol affects the amount of propofol required for induction of anaesthesia.

Methods In this prospective controlled study, we evaluated 46 patients, half of whom used tramadol regularly. Entropy indices, state entropy and response entropy, were used to assess the level of hypnosis. Patients were anaesthetized with a propofol infusion (1 mg kg⁻¹ min⁻¹) until they first became unconscious, and further until they developed a burst suppression pattern in the electroencephalogram. The doses of propofol needed to reach these end-points were recorded.

Results The amount (median, (range)) of propofol required for loss of consciousness was 2.0 (1.0–5.5) mg kg⁻¹ and 2.4 (0.9–8.3) mg kg⁻¹ (P = 0.95) in the tramadol users and controls, respectively. The amount of propofol required for burst suppression was 5.8 (3.9–12.7) mg kg⁻¹ and 6.4 (2.9–15.1) mg kg⁻¹ (P = 0.89) in the tramadol users and controls. There was no difference between the groups in state entropy and response entropy during different stages of induction of anaesthesia.

Conclusions Tramadol did not affect the dose of propofol required to achieve loss of consciousness or burst suppression pattern in electroencephalogram during induction of general anaesthesia. However, there was a ninefold inter-individual variation in propofol dose requirement for loss of consciousness and a fivefold variation for reaching burst suppression. Due to extensive inter-individual variability, monitoring the level of hypnosis during general anaesthesia using propofol may enhance the correct dosage.

(Accepted March 09 2007)

Key Words: TRAMADOL; PROPOFOL; ELECTROENCEPHALOGRAM, bispectral index; ENTROPY; DRUG INTERACTIONS

Correspondence:

^c1 Correspondence to: Anne Vakkuri, Department of Anaesthesiology and Intensive Care, Surgical Hospital, Helsinki University Hospital, P.O. Box 263, FI-00029 HUS, Helsinki, Finland. E-mail: anne.vakkuri@hus.fi; Tel: +358 50 427 0653; Fax: +358 9 47188609