The Annals of Thoracic Surgery, Vol 31, 121-133, Copyright © 1981 by The Society of Thoracic Surgeons
Effects of hypothermia, hemodilution, and pump oxygenation on organ water content, blood flow and oxygen delivery, and renal function
JR Utley, C Wachtel, RB Cain, EA Spaw, JC Collins and DB Stephens
Hypothermia, hemodilution, and the pump-oxygenator each contribute
important effects during cardiopulmonary bypass. We studied their separate
effects with a 2(3) factorial, completely fixed experimental design in 16
adult male mongrel dogs. Animals undergoing hypothermia were cooled to 25
degrees +/- 1 degree C. In dogs having hemodilution, hematocrit was
adjusted to 25 +/- 2%. An analysis of variance was used to determine the
effects of hypothermia, hemodilution, and pump oxygenation. The experiments
show that hemodilution produces increased water content in tissue and that
edema is greatest in heart and gastrointestinal organs. The pump-oxygenator
decreased flow to the subendocardium, whereas hemodilution increased
subendocardial flow. Both hypothermia and pump oxygenation diminished flow
to the outer kidney cortex, and hemodilution augmented flow to this region.
Hypothermia and pump oxygenation decreased and hemodilution raised renal
free-water clearance. Although none affected glomerular filtration rate,
hypothermia increased filtration fraction while hemodilution diminished it.
Hypothermia lessened cerebral cortical flow, an effect opposite that of
hemodilution. Thus, hemodilution opposes the adverse effect of hypothermia
or pump oxygenation on blood flow, oxygen delivery, or renal function.
Increased water content in gastrointestinal organs and myocardium
accompanies the beneficial vascular and renal effects of hemodilution.
