Influence of morphine on the distal oesophagus and the lower oesophageal sphincter--a manometric study.

Basal pressure and relaxation of the lower oesophageal sphincter (LOS) as well as amplitude, duration and propagation velocity of peristaltic waves in the distal third of oesophagus were measured in 15 healthy adults (nine men and six women). A highly standardised technique was used employing manometric equipment including a low-compliance pneumohydraulic infusion system and a triple lumen recording catheter. After establishment of baseline manometry values the catheter was positioned with its distal orifice in the lower oesophageal sphincter. In 10 subjects 0.2 mg/kg body weight of morphine sulphate was then injected subcutaneously. In five others equal volume of saline was given. The manometric data were analysed blindly. Repeated manometric evaluations were carried out 15, 30, 45, 60, and 75 minutes after the injection. Morphine increased slightly LOS-pressure and significantly (p less than 0.001) decreased LOS-relaxation, the maximal effect occurring 30 minutes after the injection. Amplitude of peristaltic waves increased slightly but insignificantly, whereas propagation velocity and duration were uninfluenced. The results of this study suggest that pharmacologic doses of morphine influence normal function of the LOS and possibly the distal oesophagus. The role of endogenous opiates in this respect, however, awaits further studies. It is suggested that abnormalities in opioid neurotransmission may explain some of the non-specific oesophageal motility disorders.