Circulatory Responses to Acute Isovolemic Hemodilution in Hypoxic Dogs

Kim, Seong Deok; Lim, Seung Woon

Abstract

The circulatory responses to acute isovolemic hemodilution were studied in nine mongrel dogs in hypoxic(FIO2=0.15) environment. The animals were bled 20ml/kg of blood. The shed blood was replaced by equivalent amounts of low molecular weight extran(LMWD). Hemodynamic measurements and calculations were performed in control normoxic period, hypoxic period before bleeding, hypoxic period after fleeding and after hemodilution with LMWD. By hemodilution, Hb and Hct were decreased from 13.6+/-0.8gm/dl and 41+/-2% to 12.9+/-0.9gm/dl and 21+/-2%, respectively. Hypoxia itself did not cause any hemodynamic changes. Bleeding caused significant increases in SVR(60%) and PVR(77.9%), and resulted in decreases in CI(40.0%), TI(32.7%) and PCWP(2.0%) compared with the data in control period. Hemodilution reversed hemodynamic changes induced by bleeding. PVR returned to normal and SVR was rather decreased by 24.2%, CI, PCWP and CVP were increased by 25.4%, 6.0%, and 37.5%, respectively. The parameters such as HR and RPP which might be related to oxygen consumption were decreased by 10.6%, compared with control data. This study demonstrated that, in spite of lowered arterial oxygen content during hemodilution, tissue oxygen supply and cardiac performance might be well maintained by combined effects of decreased afterload and oxygen consuming factors, and increased preload. In conclusion, acute isovolemic hemodilution with LMWD might be a safe tolerable method in the aspects of circulatory response in hypoxic dogs.