To decrease homologous transfusion and bleeding, hemodilution may be combined with induced hypotension. The effects of the above method on hemodynamics and oxygen carrying capacity in human is not studied.
Ten patients, age 16-62 yr, having posterior spinal fusion, were studied. Acute preoperative hemodilution to hematocrit 27% with infusion of 10% pentastarch was performed in the patients. After induction of anesthesia and positioning we decreased
mean
arterial pressure to around 55mmHg by isoflurane and sodium nitroprusside. We observed the changes of hemodynamics and oxygen carrying capacity before hemodilution, after hemodilution, after induced hypotension and before the end of operation.
After hemodilution, heart rate and arterial pressure were not changed significantly. Cardiac output and central venous pressure increased significantly. Systemic vascular resistance decreased significantly. There were no significant changes in
arterial
and mixed venous blood gas analysis. Oxygen flux was not changed significantly. Oxygen consumption and oxygen extraction ratio increased significantly but remained within normal range.
After induced hypotension, heart rate was not changed. Cardiac output became lower than that after hemodilution, but was not different from the preoperative value. Systemic vascular resistance became lower than the preoperative value. There were
no
significant changes in arterial and mixed venous blood gas analysis except for mixed venous blood oxygen saturation. The mixed blood oxygen saturation increased to the preoperative level. Oxygen flux decreased, but oxygen consumption and oxygen
extraction ratio were not significantly different from the preoperative values.
There were no clinically significant changes in hemodynamics and oxygen carrying capacity before the end of operation.
By the above results, we concluded that the combined use of hemodilution and induced hypotension is safe in the aspect of hemodynamics and oxygen carrying capacity.
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