Comparison of analgesic methods for total knee arthroplasty: metabolic effect of exogenous glucose

This study was set up to assess whether postoperative suppression of gluconeogenesis by dextrose infusion would be influenced by continuous peripheral nerve block (CPNB) with local anesthetics, in comparison with epidural and with intravenous analgesia.

Twenty-seven patients, undergoing elective primary total knee arthroplasty for osteoarthritis, were randomly allocated to one of the three groups of 9 patients each: patient controlled analgesia (PCA) with i.v. morphine, epidural with bupivacaine 0.1% and fentanyl 3mug/ml, or continuous femoral and sciatic blocks with ropivacaine 0.2%. Endogenous glucose production, an index of gluconeogenesis, and glucose clearance, an index of whole body glucose uptake, were assessed on the second postoperative day by measuring [6,6-(2)H(2)]glucose kinetics after an overnight fast (fasted state), and during a 3-h period infusion of dextrose at 4 mg/kg/min (fed state). Visual analog scale (VAS) at rest and at knee flexion, use of morphine, mobilization, nutritional intake, and bowel function were also collected.

Endogenous glucose production was totally suppressed by 3 h of dextrose infusion in all 3 groups (P < .001) while glucose clearance was unchanged. Blood glucose and insulin increased (P < .001), while glucagon decreased, with the greatest change in the epidural group (P < .05). VAS at rest and at knee flexion was significantly lower in patients receiving epidural and CPNB compared to i.v. morphine (P < .05). Restoration of bowel function, assessed as return of bowel movements, was faster in the CPNB group (P < .05).

Excellent analgesia was achieved in the epidural and continuous nerve block groups. Postoperative gluconeogenesis was totally suppressed by dextrose infusion independent of the analgesia technique with no change in glucose utilization.