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EPIDURAL BLOCKADE AND FEEDING INCREASE PROTEIN SYNTHESIS AFTER SURGERY

Department of Anesthesia, McGill University, Royal Victoria Hospital, 687 Pine Avenue West,Montreal, Quebec, Canada H3A 1A1

INTRODUCTION

Epidural blockade with local anesthetics established before and maintained after abdominal surgery has been shown to improve postoperative uptake and oxidative utilization of exogenous glucose and to decrease amino acid oxidation when compared with intravenous analgesia using morphine.¹Probably due to the lack of anabolic substrate provision epidural blockade failed to exert any ben-eficial effect upon protein synthesis. The purpose of this study was to test the hypothesis that peri-operative epidural blockade significantly enhances whole body protein synthesis during combined intravenous administration of glucose and amino acids.

METHODS

After approval by the local Ethics Committee, twelve metabolically healthy patients undergoing col-orectal surgery for non-metastatic disease were randomly assigned to receive either general anesthesia combined with continuous perioperative epidural analgesia (EDA, n=6) or general anesthesia alone followed by patient controlled intravenous analgesia with morphine (PCA, n=6). A six hour L-[1-¹³C]leucine infusion study (three hours fasted followed by a three hour glucose infusion at 4 mg/kg/min combined with amino acids (Travasol^TM 10%) administered at 0.02 ml/kg/min) was performed on the second postoperative day to determine whole body protein breakdown (rate of appearance, R_a of leucine), amino acid oxidation and protein synthesis in the fasted and fed state.

RESULTS

There was no significant difference between the two groups regarding the R_a of leucine (PCA 109±16 µmol/kg/h, EDA 103±17 µmol/kg/h), amino acid oxidation (PCA 18±4 µmol/kg/h, EDA 17±9 µmol/kg/h) and protein synthesis (PCA 91±15 µmol/kg/h, EDA 86±11 µmol/kg/h) in the fasted state. Administration of glucose and amino acids significantly decreased the endogenous protein breakdown to 87±11 µmol/kg/h in the PCA group (p<0.05) and to 87±15 µmol/kg/h in the EDA group (p<0.05). The significant increase in leucine oxidation dur-ing feeding tended to be higher in patients with PCA (26±11 µmol/kg/h) than in patients receiving EDA (18±4 µmol/kg/h, PCA vs. EDA p>0.05). Epidural blockade was associated with a significantly more pronounced increase in protein synthesis when compared to PCA (EDA 13±7 µmol/kg/h, PCA 1±9 µmol/kg/h, PCA vs. EDA p<0.05)

DISCUSSION

Epidural blockade does not affect postoperative protein catabolism in the fasted state. In contrast to intravenous analgesia with morphine, epidural blockade increases protein synthesis in presence of energy (glucose) and anabolic substrate (amino acids) supply indicating a better preservation of whole body protein.

REFERENCES

1 Am J Physiol2000;279: 646–53

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