Epidural analgesia reduces the release of amino acids from peripheral tissues in the ebb phase of the metabolic response to major upper abdominal surgery

Intraoperative epidural blockade prevents the increase in protein breakdown after abdominal surgery

BACKGROUND

The aim of this study was to investigate the effect of epidural blockade with bupivacaine, restricted to the intraoperative period, on protein catabolism after major abdominal surgery.

METHODS

Fourteen patients undergoing cystoprostatectomy were randomly assigned to receive either general anaesthesia with isoflurane (control group, n=7) or a combination of general anaesthesia and epidural blockade with bupivacaine from segment T4 to S5 (epidural group, n=7). Rates of urea (Ra urea) and glucose production (Ra glucose) were measured three days before and three days after the operation using stable isotope tracers ([15N2]urea, [6,6-2H2]glucose). Protein breakdown was calculated from the urea production rate. Plasma concentrations of metabolic substrates (urea, glucose, lactate, glycerol, amino acids) and hormones (insulin, glucagon, cortisol, adrenaline, noradrenaline) were also determined.

RESULTS

Protein breakdown significantly increased after surgery in the control group (P<0.05), while it remained unaltered in the epidural group (control; 66 (54-76), epidural; 43 (29-58) mg x kg(-1) x h(-1), P<0.05, median (range)). Glucose plasma concentration and Ra glucose increased in both groups to a similar extent (P<0.05). Plasma concentration of branched chain amino acids decreased after epidural analgesia to a value significantly lower than in the control group (P<0.05). Glutamine plasma concentration decreased in the control group (P<0.05), but did not change in the epidural group. There were no differences in plasma concentrations of insulin, cortisol and catecholamines between the two groups. Glucagon plasma concentration in the epidural group was significantly lower than in the control group (P<0.05).

CONCLUSION

Intraoperative epidural blockade inhibits the increase in protein breakdown after abdominal surgery.

Epidural analgesia with a combination of bupivacaine and buprenorphine in rats

We determined the analgesic effects of epidural administration of either bupivacaine at 62.5, 125, 250, and 500 micrograms/kg; buprenorphine at 5 and 10 micrograms/kg; and the combination of bupivacaine at 125 micrograms/kg and buprenorphine at 5 or 10 micrograms/kg, using the tail flick (TF) and colorectal distension (CD) tests in rats and compared the results with those obtained using morphine at 100 micrograms/kg. In both the TF and CD tests, all doses of bupivacaine alone produced potent anti-nociceptive effects, although the effect rapidly diminished after 20-30 min of administration. The administration of buprenorphine at 10 and 5 micrograms/kg produced mild to moderate anti-nociceptive effects in both the TF and CD tests, and the effects were relatively constant throughout the 2-h experimental period. Combinations of 5 or 10 micrograms/kg of buprenorphine with 125 mg/kg of bupivacaine produced a significantly higher percentage of maximum possible analgesic effect (%MPE) than that of the calculated additive effect of each drug alone in the TF and CD tests. The analgesic effect of this combination was similar to that of morphine. Minimal ataxia was observed in rats administered this combination.