Vasopressin secretion in response to haemorrhage: mathematical modelling of the factors involved

Stimulus for vasopressin release during elective intra-abdominal operations

In 12 patients undergoing an upper abdominal operation, blood pressure and peripheral venous blood samples were taken at intervals throughout the procedure. There was no significant increase in plasma vasopressin concentration after induction of anaesthesia or skin incision; within 3 min of opening the peritoneum and commencing intraperitoneal manipulation there was a highly significant rise (P less than 0.01), maintained with fluctuations until closure of the abdomen. There was no correlation between the changes of blood pressure and those in plasma vasopressin level. In 16 patients undergoing elective cholecystectomy similar observations were made to coincide with events believed, on the basis of the first study, to be related to changes in the concentration of vasopressin. There was a significant rise in vasopressin concentration (P less than 0.01) after incision of the peritoneum, 1 min after the start of intraperitoneal manipulation (P less than 0.01) and after deliberate traction on the stomach (P less than 0.01). During operative cholangiography, when there was no intraperitoneal manipulation, there was a significant fall in the vasopressin level. There was no correlation between changes in vasopressin concentration and blood pressure. These findings indicate that during an abdominal operation nervous stimuli, arising from within the peritoneal cavity and probably mediated via the autonomic system, are an important factor responsible for the increased secretion of vasopressin, and, at least in the absence of major changes in blood pressure and osmolality, the determinant factor.

Vasopressin: its role in antipyresis and febrile convulsion

When pyrogenic substances are injected intravenously into experimental animals, a sequence of events is set in motion which involves the hypothalamus and perhaps other portions of the diencephalon to produce a febrile response. We now present evidence that the brain produces its own endogenous antipyretic which may serve as a means of controlling the extent of the fever. When arginine vasopressin is perfused through the lateral septal area of the hypothalamus of the sheep, fever is suppressed. Vasopressin alone does not lower normal body temperature when perfused through this region of the brain. In addition, evidence is provided to indicate that vasopressin is released within the lateral septal area during the febrile response. It is concluded that, in fever, arginine vasopressin may be released in the lateral septal area of the brain and serve as an endogenous antipyretic. Results indicate that, following an initial application of vasopressin into the brain itself, a subsequent similar administration of vasopressin produces seizure-like activity. Therefore, it is suggested that this release of arginine vasopressin may contribute to the production of febrile convulsion.

Effect of osmolality on arginine vasopressin and renin release after hemorrhage

The effects of alterations of plasma osmolality on plasma arginine vasopressin (AVP) and renin activity (PRA) following graded hemorrhage were studied in conscious dogs who were either euhydrated, dehydrated, water loaded, or infused with hypertonic saline. Base-line plasma osmolality and AVP were significantly different in the four treatment groups; however, following hemorrhage the increases in log AVP did not significantly differ. An unexpected finding was that water loading resulted in significant elevations in PRA and plasma aldosterone concentrations, whereas plasma osmolality and AVP were reduced. Prior to hemorrhage, PRA was significantly greater in the water-loaded and dehydrated groups than in the euhydrated or saline-infused groups; following hemorrhage the increases in log PRA were not significantly different in all four treatment groups. The data suggest that, although alterations in osmolality influence base-line levels of AVP, they have no effect on relative (logarithmic) rises in AVP following hemorrhage. Similarly, alterations in AVP may influence base-line PRA, but do not influence relative rises in PRA following hemorrhage.