Hyperglycemic and Hyperosmolar Responses to Graded Hemorrhage

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Abstract
Changes in arterial plasma osmolality and glucose concentration were followed during a 30 min period of graded hemorrhagic hypotension (80, 50 and 30 mm Hg) in the cat. Bleeding evoked a significant plasma hyperosmolality at all 3 hypotension levels and the responses were quantitatively related to the degree of hypotension. An approximate steady state increase in the arterial plasma osmolality was reached about 20 min after the start of the bleeding and averaged 8, 20 and 25 m osmol/kg H2O at 80, 50 and 30 mmHg, respectively. Bleeding also evoked an increase in the plasma glucose concentration which almost entirely accounted for the observed hyperosmolality, especially at 80 and 50 mmHg. In late stages of hypotension at 30 mmHg, elevated plasma lactate and K concentrations contributed to the overall hyperosmolality. Previous hemorrhagic hypotension experiments at 50 mmHg showed that hyperosmolality serves as an important regulator of the plasma and extracellular fluid volumes during bleeding. An osmolar compensatory mechanism may operate over wide ranges of hemorrhagic hypotension.