Hematocrit correction of pulmonary vascular resistance significantly alters values, demonstrating that a PVR of 1.5 WU at 20% hematocrit becomes 4.1 WU at 45% and 10.8 WU at 80%.
Does hematocrit correction improve the accuracy of pulmonary vascular resistance estimation in patients with anemia or polycythemia?
Hematocrit corrections of PVR should be considered for the diagnosis and assessment of pulmonary hypertension in patients with anemia or polycythemia.
The diagnosis and evaluation of severity of pulmonary vascular disease rests on the invasive determination of a pulmonary vascular resistance (PVR). It is often overlooked that PVR is linearly related to the viscosity of the blood, which in turn is curvilinearly related to hematocrit. We propose a correction diagram for patients with anemia or with polycythemia. Based on a distensibility model of the pulmonary circulation, we show that magnitude of hematocrit correction of PVR is increased in proportion to pulmonary artery wedge pressure (PAWP) and the measured levels of PVR or hematocrit, and decreased in case of preserved resistive vessel distensibility and absence of pulmonary hypertension. We also demonstrate that hematocrit correction of PVR is independent of the absolute levels of pulmonary artery pressure or cardiac output. A PVR of 1.5 Wood units (WU) at a hematocrit of 20 % and a high-normal PAWP becomes 4.1 WU at a hematocrit of 45 % and 10.8 WU at a hematocrit of 80 %. A review of reported hemodynamic measurements before and after either blood transfusion or iso-volemic hemodilution shows that deviations from our model's predictions are uncommon. However, their identification may be useful to estimate the contribution of neuro-humoral mechanisms to the functional state of the pulmonary circulation in these patients, and further uncover possible impact of background conditions such as hemolysis or red blood cell deformation. We conclude that hematocrit corrections of PVR should be considered for the diagnosis and assessment of pulmonary hypertension in case of anemia or polycythemia.
Vanderpool et al. (Wed,) conducted a review in Pulmonary vascular disease. Hematocrit correction of pulmonary vascular resistance was evaluated on Hematocrit-corrected pulmonary vascular resistance. Hematocrit correction of pulmonary vascular resistance significantly alters values, demonstrating that a PVR of 1.5 WU at 20% hematocrit becomes 4.1 WU at 45% and 10.8 WU at 80%.