HYPOTENSION INDUCED BY HEMORRHAGE IMPAIRS LOWER ESOPHAGEAL SPHINCTER FUNCTION

The effect of haemorrhage-induced hypotension on lower oesophageal sph incter (LOS) tone was studied in 11 adult mongrel dogs. Mean(s.e.m.) b lood loss of 760(66)ml, corresponding to 42 per cent of estimated bloo d volume, was associated with a significant fall in LOS tone (14.2(1.0 ) versus 7.2(0.6) sphinctometer units, P<0.002). This was associated w ith a reduction in mean(s.e.m.) arterial blood pressure (99(7) versus 53(3) mmHg, P<0.002) and heart rate (113(6) versus 106(5) beats per mi n, P=0.06). Group 1 animals (n=6) received autotransfusion, restoring LOS tone to prehaemorrhage values. Dogs in group 2 (n=5) were given in travenous erythromycin 4 mg/kg, which also restored LOS tone. This eff ect was transient, lasting a mean(s.e.m.) of only 67(7) min. Infusion of an equivalent volume of 0.9 per cent saline following cessation of the erythromycin effect restored LOS tone to control values although t he animals remained hypotensive. Reduction in LOS tone with haemorrhag e may be part of a vagal reflex mediated by myocardial afferent C fibr es and may explain the high incidence of pulmonary aspiration in shock ed patients.