Adrenocorticotropin response to graded blood loss in the cat

To assess the early endocrine and physiological responses to rapid blood loss, adult cats anesthetized with chloralose-urethan sustained transient hemorrhage (H) of different magnitudes for a 3-min duration. The magnitude of H was expressed as a percentage of initial total blood volume after plasma volume determination by dye dilution or on a per unit body weight basis. Considerable variation in total blood volume was observed at all body weights (range, 44.5-80.2 mg/kg). Adrenocorticotropin (ACTH) in peripheral venous plasma was not significantly altered by 10% H but increased modestly after 20% H by 5 min (148 +/- 67 pg/ml) and rose promptly after 30% H by 2 min (541 +/- 155 pg/ml) with a peak at 5 min (579 +/- 171 pg/ml). Total change in ACTH during the 15-min sampling period was proportional to the magnitude of H (r = 0.730, P less than 0.001). Mean arterial pressure (MAP) decreased significantly to all magnitudes of H by 1 min with a graded recovery during the 3-min hypovolemic period that was well correlated (r = 0.602, P less than 0.005) with the percentage of blood volume removed. Mean plasma glucose concentration was not significantly changed by 10 or 20% H but increased after 30% H by 5 min (46.2 +/- 10.2 mg/dl). Total glucose change from prestimulus levels during the 15-min sampling period was correlated with the magnitude of H (r = 0.731, P less than 0.001). Plasma norepinephrine increased equally after 20 or 30% H or 10 ml/kg H but was not significantly elevated after 10% H.(ABSTRACT TRUNCATED AT 250 WORDS)