Acute, normovolemic hemodilution: effects on systemic and splanchnic blood flows and oxygen metabolism

The impact of acute normovolemic hemodilution (HD) on splanchnic perfusion was evaluated in 21 anesthetized (fentanyl and vancuronium) mongrel dogs (16 ± 1 kg). They were randomized to controls (n = 7, no HD), moderate HD (hematocrit 25 ± 3%, n = 7) or severe HD (hematocrit 15 ± 3% ml/kg), through an isovolemic exchange of whole blood and 6% hydroxyethylstarch at a 20 ml/min rate, to the target hematocrit. The animals were followed 120 min after HD. Cardiac output (ml/min), portal vein blood flow (ml/min), portal vein-arterial CO₂ gradient (mmHg) and PCO₂ gap (gas tonometry, mmHg), and splanchnic perfusion were evaluated through portal vein blood flow and gas tonometry.

Results

Exchange blood volumes were 33.9 ± 3.3 and 61.5 ± 5.8 ml/kg for moderate HD and severe HD, respectively. Controls maintained a hematocrit of around 41% throughout the study. Arterial pressure remained stable for all animals.

Conclusion

Global and regional hemodynamic stability were maintained after moderate and severe HD. However, a moderate gastric mucosal acidosis was induced with a hematocrit of 15%, which may become relevant after major surgery or trauma.

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