Abstract ID: A10
Abstract Title: Protein metabolism and glucose feeding. Does it matter whether is epidural ropivacaine or morphine?
Poster Type: Either
ABSTRACT BODY
Introduction:Pain relief with epidural analgesia has been shown to minimize the obligatory loss of body nitrogen.[1] Administration of 4 mg/kg/min dextrose in presence of epidural analgesia facilitates the oxidative utilization of glucose along with decreased amino acid oxidation.[2]We hypothesize that postoperative epidural analgesia with ropivacaine, in contrast to epidural morphine,in presence of dextrose feeding, inhibits amino acid oxidation to a greater extent.
Materials and Methods: Fourteen patients scheduled for colorectal surgery were studied on the second postoperative day. They were randomly assigned to receive either epidural analgesia with 0.2% ropivacaine infusion, 8-15 ml/h,or intermittent epidural morphine, 30-60 mcg/kg. The epidural medications were given before surgery and the analgesia was continued for three postoperative days. Stable isotopes, (L-[1-13C] leucine and [6,6-2H2]glucose, were infused over a period of six hours, three hours during a fasted state and three hours during a fed state where i.v.dextrose was administered at a rate of 4 mg/kg/min. Protein synthesis, breakdown and oxidation, and glucose production were determined using isotopic methodology. Substrate oxidation rates were calculated using indirect calorimetry, and plasma metabolic substrates and hormones measured during the isotopic infusion.
Results: Pain visual analog scale at rest and on movements was similar in both groups. No difference in protein and glucose kinetics was found between the two groups during the fasted state. Glucose feeding was associated with decreased protein breakdown (p=0.01) and glucose production (p=0.001) to the same extent in both groups. There were no changes in protein oxidation. Carbohydrate oxidation rate in the ropivacaine group was greater than in the morphine group (p=0.04). The increased carbohydrate oxidation in the ropivacaine group might be explained by the improved insulin sensitivity.
Discussion:Epidural analgesia with either ropivacaine or morphine did not suppress the catabolic response to surgery, neither under fasting conditions nor in presence of energy supply, implying that both ropivacaine and morphine lack anticatabolic effect. One could speculate that the quality of pain relief with both drugs does not necessarily determine the extent of postoperative catabolism.
References:
1. Carli F, WebsterJ, Pearson M, et al. Protein metabolism after abdominal surgery: effect of 24-h extradural block with local anesthetics. Br J Anaesth 1991; 67: 729-734
2. Schricker T, Wykes L, Carli F. Epidural blockade improves substrate utilization after surgery. Am J Physiol 2000; 279: E646-E653
ATTACHED FILES
Reg Anesth Pain Med 2004; 29(2):A10