Abstract
The effects of epidural morphine on the postoperative urinary excretion of catecholamines were studied in patients who underwent upper abdominal surgery. Either preservative-free morphine, 2 mg in 20 ml of saline (morphine group) or 20 ml of normal saline (saline group) was injected epidurally through a catheter placed in the space between Th 7-8 during surgery. Urine samples were collected just after induction and 5 hours postoperatively. Catecholamines were analyzed with high-performance liquid chromatography and expressed as ng/mg urinary creatinine (Cr).
In the saline group there was an increase in the excretion of postoperative norepinephrine and epinephrine, changing from 80.8±38.6 (Mean±SD) ng/mg Cr to 108.9±49.6 ng/mg Cr (P<0.05) and from 22.1±15.7 ng/mg Cr to 59.3±41.5 ng/mg Cr (P<0.05), respectively. In the morphine group, by contrast, no significant changes in catecholamine excretion were observed.
The present study indicates that postoperative pain relief with the use of epidural morphine suppresses the increase of sympathoadrenal activity. This procedure may be advocated in patients with poor cardiac reserve in whom avoidance of increased myocardial workload is a major consideration.
