Abstract

As gastric acid and pepsin inhibit blood coagulation and platelet aggregation it is surprising that most upper GI haemorrhages stop spontaneously. To investigate this paradox we have studied acid and pepsin secretion, gastric motility and GI hormones after simulated upper GI haemorrhage. In seven healthy volunteers intraduodenal infusion of 160 ml autologous blood decreased pentagastrin stimulated submaximal acid secretion (mmol/h) from 30.0 (3.2) (mean (SE] in the hour preceding infusion to 21.4 (3.7) in the hour following infusion (p less than 0.02), representing a mean reduction in acid output of 30%. Pepsin output (mg/h) was also decreased from 207.5 (67.7) (mean (SE] in the hour preceding blood infusion to 135.7 (54.7) in the hour after infusion (p less than 0.02) representing a mean reduction in pepsin output of 43%. In six volunteers gastric emptying of a liquid meal was delayed after intraduodenal blood infusion compared with intubation alone with the emptying time (min) to half volume (t 1/2) being prolonged at 75.0 (8.2) (mean (SE] after blood infusion compared with 35.5 (6.6) after intubation alone (p less than 0.02). Plasma GIP concentrations (ng/l) increased to peak levels of 127.9 (62.7) (mean (SE] after intraduodenal blood infusion compared with the pre-infusion value of 58.3 (2.3) (p less than 0.02). These changes may represent protective physiological responses to facilitate haemostasis.