Influences of fasting and water intake on plasma refill during hemorrhagic shock.

The hyperglycemic response to hypovolemia has been regarded as an essential osmotic force for promoting the early phase of the internal restoration of plasma volume. Our previous studies of rats fasted 24 hours revealed that they did not develop the hyperglycemic response to hemorrhage observed in fed animals but they had a similar hyperosmotic response. The solutes responsible for the hyperosmolality in the fasted animals were primarily products of anaerobic glycolysis, rather than glucose which accounted for most of the hyperosmolality in fed animals. Plasma refill as reflected by a fall in the hematocrit (Hct) and survival time was significantly reduced in the fasted animals. This study was undertaken to test the hypothesis that the failure of fasted rats to exhibit a normal restoration of plasma volume after hemorrhage may reflect the detrimental effects of fasting on the state of hydration and on the plasma oncotic pressure of the fasted animals rather than the absence of a hyperglycemic response. Four groups of anesthetized rats (280-380 gm) were bled acutely and maintained at an arterial pressure of 40 mm Hg. Before hemorrhage animals in Group A were well fed, those in Groups B, C, and D were fasted for 24 hours. Rats in Group B were induced to drink by addition of sodium chloride in their water, rats in Group C spontaneously had a normal fluid intake, and rats in Group D had a significant reduction in their 24-hour fluid intake. The results demonstrated that 24 hours of fasting led to a loss of body weight of 7 to 10% and a fall in the concentration of plasma total protein of 12 to 17% in all rats.(ABSTRACT TRUNCATED AT 250 WORDS)