CARDIOPULMONARY INTERACTIONS AFTER FONTAN OPERATIONS - AUGMENTATION OF CARDIAC-OUTPUT USING NEGATIVE-PRESSURE VENTILATION

Background The low-output state is the chief cause of morbidity and mo rtality after Fontan operations. An alternative hemodynamic tool would be a welcome addition for these patients, who are typically resistant to conventional therapeutic measures. Methods and Results The hemodyn amic effects of conversion from conventional intermittent positive pre ssure ventilation (IPPV) to cuirass negative pressure ventilation (NPV ) was investigated in nine acute postoperative Fontan patients on the pediatric intensive care unit and nine anesthetized patients undergoin g cardiac catheterization in the convalescent phase after Fontan opera tions. Pulmonary blood flow was measured using the direct Fick method during IPPV and after a brief period of NPV. In one subgroup of patien ts, pulmonary blood flow was measured again after reinstitution of IPP V, and in a second subgroup, pulmonary blood flow was measured after a n extended period of NPV. A brief period of NPV increased pulmonary bl ood flow from 2.4 to 3.5 L.min(-1)./m(-2), with a mean increase of 42% . Pulmonary blood flow continued to improve, with a total increase of 54% after an extended period of NPV. Values fell toward baseline after reinstitution of IPPV. Heart rate was unchanged during NPV, and the i mprovement in pulmonary blood flow was achieved by an increase in stro ke volume from 25 mL/m(2) to 37 mL/m.(2) Conclusions Through improveme nt of the stroke volume alone, NPV brought about a marked increase in the pulmonary blood flow and, hence, cardiac output of Fontan patients . An improvement in cardiac output of this order, and by this mechanis m, is currently unmatched by any therapeutic alternatives.