Relationship between increased blood pressure and hematocrit during modified ultrafiltration for pediatric open heart surgery.

OBJECTIVE: Modified ultrafiltration increases blood pressure after cardiopulmonary bypass in children. To investigate the cause of this hemodynamic improvement, we assessed the relationship between increased blood pressure and hematocrit.
METHODS: We retrospectively assessed 30 consecutive patients who underwent ventricular septal defect closure, and divided them into two groups: group M (modified ultrafiltration, n=15) and group C (conventional ultra-filtration, n=15). We compared the intraoperative transitions of blood pressure and hematocrit, and analyzed the correlations between blood pressure and hematocrit at 15 min after cardiopulmonary bypass (immediately after modified ultrafiltration in group M) and between the percent increases in blood pressure and hematocrit during modified ultrafiltration.
RESULTS: Although intraoperative central venous pressure and dopamine dosage were similar, in group M, increases in hematocrit (26.4% +/- 4.9% to 31.9% +/- 5.7%, P < 0.01) and systolic blood pressure (61.1 +/- 10.3 to 75.6 +/- 11.5 mmHg, P < 0.01) occurred during modified ultrafiltration. Furthermore, diastolic and mean blood pressure at 15 min after cardiopulmonary bypass (after modified ultrafiltration) were higher in group M than in group C. However, systolic, mean, and diastolic blood pressure were not correlated with increased hematocrit after modified ultrafiltration, and there was also no correlation between the percent increases in each blood pressure and hematocrit.
CONCLUSION: Modified ultrafiltration increased blood pressure and hematocrit immediately after cardiopulmonary bypass in children. However, no correlations were detected between the increases in blood pressure and hematocrit. These results indicate hemoconcentration is not the major cause of the increased blood pressure during modified ultrafiltration.