Effect of modified ultrafiltration on pulmonary function after cardiopulmonary bypass.

BACKGROUND Pulmonary dysfunction is one of the most common manifestations of inflammatory response after cardiopulmonary bypass (CPB). OBJECTIVE This prospective randomized study was conducted to evaluate the effect of a modified ultrafiltration (MUF) technique on pulmonary function after CPB in children. METHODS Forty patients weighing from 5 to 10 kg with congenital heart disease who required CPB for primary biventricular operative repair were prospectively randomized into two groups. The control group received conventional ultrafiltration (CUF) during CPB, and the study group received CUF and MUF. Pulmonary compliance (static and dynamic) and gas exchange capacity of the lung expressed as oxygen index, respiratory index, ventilation index, and alveolar-arterial oxygen pressure difference were measured after intubation (baseline), at the termination of CPB, at the end of MUF, on admission to the ICU, and 6 h postoperatively. RESULTS There was no significant difference in lung compliance and gas exchange between the two groups before CPB. CPB produced a significant decrease in static and dynamic lung compliance in both groups. In the control group, static and dynamic lung compliance decreased from 1.0 +/- 0.3 to 0.90 +/- 0.3 mL/cm/kg and 0.87 +/- 0.2 to 0.71 +/- 0.1 mL/cm/kg (+/- SE) [p = 0.0002 and p = 0.002, respectively]. In the study group, static and dynamic lung compliance decreased from 1.0 +/- 0.2 to 0.89 +/- 0.03 mL/cm/kg and 0.94 +/- 0.2 to 0.77 +/- 0.1 mL/cm/kg (p = 0.002 and p = 0.002, respectively). There was no significant difference in the decrease in static (p = 0.9) or dynamic lung compliance (p = 0.3) between the two groups. MUF produced a significant immediate improvement in both static lung compliance (0.89 +/- 0.2 to 0.98 +/- 0.2 mL/cm/kg, p = 0.03) and dynamic lung compliance (0.77 +/- 0.1 to 0.93 +/- 0.2 mL/cm/kg, p = 0.007). The same was observed regarding the gas exchange capacity. CPB produced a significant decrease in lung gas exchange capacity, and MUF produced a significant immediate improvement in lung gas exchange capacity. The effect of MUF on lung compliance and gas exchange capacity was not sustained after admission to the ICU nor 6 h later postoperatively. There was no significant difference in the time of extubation between the two groups (12 +/- 3 h and 13 +/- 2 h, p = 0.4), the length of ICU stay, or the total hospital stay postoperatively. CONCLUSIONS The use of MUF after CPB can produce an immediate improvement in lung compliance and gas exchange capacity, which may effectively minimize pulmonary dysfunction postbiventricular repair of congenital heart disease. However, these improvements are not sustained for the first 6 h postoperatively and do not reduce the duration of postoperative intubation, ICU stay, or total hospital stay.