Systemic administration of lidocaine reduces morphine requirements and postoperative pain of patients undergoing thoracic surgery after propofol-remifentanil-based anaesthesia.

BACKGROUND AND OBJECTIVE: Remifentanil is being increasingly used as an analgesic in fast-track surgery, but severe postoperative pain may happen occasionally. In this study, we evaluated the effects of systemic administration of lidocaine on postoperative pain and morphine requirements after propofol-remifentanil-based anaesthesia.

METHODS: Forty patients undergoing thoracic surgery were randomly assigned to lidocaine (33.0 microg kg(-1) min(-1)) and physiological saline control groups in propofol-remifentanil-based anaesthesia. The setting of the plasma concentration (C(p)) of the target-controlled infusion of propofol was adjusted according to the bispectral index of the electroencephalogram and blood pressure. The C(p) and effect-site concentration (C(e)) of propofol were calculated by target-controlled infusion pump during the intraoperative period. Pain scoring includes a four-point verbal rating scale, Riker's sedation-agitation scale and a visual analogue scale; the morphine requirement in the postanaesthesia care unit and the morphine consumption via a patient-controlled analgesia device on the ward were recorded during the postoperative period.

RESULTS: Morphine requirements within 30, 30-60 and 0-120 min in the postanaesthesia care unit of the lidocaine group decreased significantly (P < 0.05, n = 20 per group) compared with that of the control group. The four-point verbal rating scale at 30 min in the postanaesthesia care unit, visual analogue scale at 6 h on coughing and patient-controlled analgesia morphine consumption during 2-6 h postoperative time were also significantly (P < 0.05, n = 20 per group) reduced in the lidocaine group. In addition, the intraoperative propofol C(e) in the lidocaine group during the periods of intubation, organ resection, closing of chest cavity and extubation was significantly lower (P < 0.05, n = 20 per group) than that in the control group under the same hypnotic depth.

CONCLUSION: Systemic administration of lidocaine could reduce morphine requirements, postoperative pain and intraoperative propofol C(e) of patients undergoing thoracic surgery after propofol-remifentanil-based anaesthesia.