NEGATIVE-PRESSURE VENTILATION IMPROVES CARDIAC-OUTPUT AFTER RIGHT HEART-SURGERY

Background A low cardiac output state can complicate the postoperative course of patients undergoing Fontan-type operations and tetralogy of Fallot repair. Methods and Results We investigated the effect of nega tive pressure ventilation on cardiac output in 11 children in the earl y postoperative period after right heart surgery. All patients were in itially ventilated with volume-cycled intermittent positive-pressure v entilation, and negative-pressure ventilation was delivered with the H ayek external high-frequency oscillator. Cardiac output was calculated by the direct Fick method, oxygen consumption being measured by respi ratory mass spectrometry. Cardiac output was measured during intermitt ent positive-pressure ventilation and after 15 minutes of negative-pre ssure ventilation. Negative-pressure ventilation improved the cardiac output by a mean of 46% (P=.005). Heart rate did not change, and strok e volume increased by a mean of 48.5% (P=.005). Mixed venous saturatio n increased by 4.6% (P<.02), and consequently arteriovenous oxygen con tent difference fell significantly (P=.01). The systemic and pulmonary vascular resistances were reduced significantly during negative-press ure ventilation (P<.05 and P<.03, respectively). Conclusions Negative- pressure ventilation improves cardiac output in children after total c avopulmonary connection and tetralogy of Fallot repair and may prove t o be an important therapeutic option in children with the low cardiac output state.