762-3 Modified Ultrafiltration Reduces Airway Pressures and Improves Lung Compliance After Congenital Heart Surgery

Abstract

Following surgery for congenital heart disease (CHD) decreased Dynamic Compliance (DC) (Δvolume/Δpressure) results in increased airway pressures, impaired cardiovascular function and prolonged mechanical ventilation. Modified ultrafiltration (MUF) reduces total body water, promotes hemoconcentration after separation from cardiopulmonary bypass (CPB), and may improve cardiorespiratory performance. MUF is accomplished by connecting the arterial cannula in series to a roller pump, an ultrafilter and the venous cannula. To determine the acute effects of CPB and MUF on respiratory mechanics (RM) after surgery for CHD, 18 pts were evaluated. The control (CTL) group consisted of 7 pts age 1 wk–9 mo and wgt 2.5–7 kg. The 11 successive pts who underwent MUF were aged 1 wk–9 yrs and wgt 3.5–23.9 kg. Diagnoses of the study group included TOF (3), AVSD (2), AS (1), cor triatriatum (1), DORV (1), HLHS (1), MS (1) and truncus arteriosus (1). RM were measured in the OR using a pneumotach and RM monitor. The peak airway pressure and peak end expiratory pressure were obtained Pre CPB, Post CPB and Post MUF (20 min post CPB in CTL group) with the tidal volume held constant. Following 17 ± 2 min of MUF, the HCT increased from 17 ± 1 to 39 ± 3% p = 0.0002. Group Pre CPB DC Post CPB DC Post MUF or 20 min post CPB DC CTL (n = 7) 4.8 ± 0.8 3.7 ± 0.5 * 3.8 ± 0.4 * MUF (n = 11) 11.3 ± 33 8.0 ± 2.2 # 10.1 ± 2.3 τ * = P < 0.05 vs Ctl Pre CPB # = P< 0.05 τ = p = ns vs MUF Pre CPB In the CTL group there was a significant reduction in DC after CPB which persisted 20 min after CPB. However, in the MUF group the reduction in DC after CPB was reversed by MUF. MUF improves DC, possibly due to a reduction in lung water. By increasing DC, MUF allows a reduction in airway pressures thereby potentially decreasing the negative impact of elevated airway pressures on cardiovascular function and improving cardiorespiratory interactions. These acute findings suggest that MUF may improve cardiorespiratory function thereby decreasing length of ventilation and length of hospital stay. Randomized studies are therefore indicated.