Elevated plasma vasopressin concentrations during endotoxin and E. coli shock.

Plasma vasopressin concentrations, measured by radioimmunoassay, were remarkably elevated during endotoxin and E. coli shock. The concentrations were often above 500 pg/ml in dogs and above 300 pg/ml in baboons; they reached 1200 pg/ml in two dogs and 1800 pg/ml in another. Plasma concentration in a quiet, hydrated subject is 4 pg/ml; osmoregulation is maximally effective at 20 pg/ml. Elevation of plasma vasopressin occurred by 15 minutes after beginning infusion of endotoxin or E. coli and reached concentrations of 200-350 pg/ml with a decrease in cardiac output but before hypotension, which suggests decreased thoracic blood volume and decompression of left atrial stretch receptors. Even higher vasopressin levels were associated with a reduction of arterial blood pressure. The typical pattern was an early peak elevation followed by a sustained plateau of plasma vasopressin concentration in dogs and baboons with endotoxin and/or E. coli-induced circulatory shock.