Epidural morphine delays gastric emptying and small intestinal transit in volunteers.

The influence of a painful stimulus and lumbar epidural morphine on gastric emptying, the orocecal transit time and small intestinal transit were studied in nine healthy volunteers. Acetaminophen absorption was used as a measure of the rate of gastric emptying. Orocecal transit time was determined by measuring the end-expiratory hydrogen concentration. Small intestinal transit was calculated from measurements of the orocecal transit time and gastric emptying. Cold pain stress with intermittent immersion of the feet in ice-cold water was used as a painful stimulus. Each volunteer was investigated on 3 different days: once after receiving 4 mg of epidural morphine and during cold pain; once during cold pain; and once under control conditions without pain and epidural morphine. Immersion of the feet in ice-cold water was always very painful, but was more tolerable during epidural morphine analgesia. The increase in blood pressure which accompanied the cold pain was the same whether this pain was induced without or during epidural morphine analgesia. Gastric emptying, orocecal transit time and small intestinal transit were delayed during epidural morphine analgesia compared with the findings under the control and plain cold pain conditions. Cold pain stress alone did not influence gastric emptying, orocecal transit time or intestinal transit. To conclude, epidural morphine in itself delayed gastric emptying, orocecal transit and transit through the small intestine in healthy volunteers.