Postoperative nitric oxide therapy in children with congenital heart disease. Can the need be predicted?

The necessity for postoperative inhaled nitric oxide (NO) therapy and predictive factors for that need were retrospectively analysed in 457 paediatric patients at risk of pulmonary hypertensive events following open-heart surgery for congenital heart disease. Inhaled NO was given postoperatively to 46% of the study group and to 23% of all patients undergoing open-heart surgery during the study period. Factors associated with increased need for postoperative NO were age <1 year, Down's syndrome, preoperative pulmonary hypertension and increased pulmonary vascular resistance. Using a multivariate model based on these factors, 73% of the patients who were given NO were identified. Thus, in a setting with unrestricted access to NO therapy, almost half of the patients with cardiac lesions that commonly give rise to postoperative pulmonary hypertension were given postoperative NO. Seventy-three percent of postoperative NO treatment was associated with a relatively small number of pre- and perioperative patient-related risk factors.

Preoperative and postoperative response to inhaled nitric oxide.

The preoperative dose response to inhaled nitric oxide (NO) was compared with the need for and response to NO after cardiac surgery in patients with congenital heart defect and secondary pulmonary hypertension. In a preoperative vasodilator test with inhaled NO 20, 40 and 80 ppm and oxygen, mean pulmonary artery pressure (PAP) was at least 40 mmHg and/or the pulmonary vascular resistance index (PVRI) 4 Wood units. Preoperatively, NO 40 ppm and FiO2 0.9 reduced systolic pulmonary/systemic arterial pressure (PAPs/SAPs) from 0.89 (SD 0.10) to 0.80 (0.18) and pulmonary/systemic vascular resistance (PVR/SVR) from 0.26 (0.13) to 0.13 (0.08). Haemodynamic assessment was repeated in 11 patients postoperatively. NO treatment was started if PAPs/SAPs rose to 0.8 or the pulmonary oximetry fell below 40%. Postoperatively, eight of 11 patients, including 6 patients with Down's syndrome, needed NO. PAPs/SAPs decreased more than preoperatively: 48.5% vs 11.2, p = 0.0045. Pulmonary oximetry increased by 15.7%, p = 0.02. The degree of preoperative response to NO did not differ between the patients with postoperative pulmonary hypertension and the other children. Patients with early pulmonary hypertensive crisis (first 24 h; n = 6) had a higher PVRI (7.6 vs 4.4 Um2; p = 0.003) and PVR/SVR (0.34 VS 0.17; p = 0.02) preoperatively. Two patients died in pulmonary hypertensive crisis.

Nitric oxide, oxygen, and prostacyclin in children with pulmonary hypertension.

OBJECTIVE: To test the vasodilatory response of the pulmonary vascular bed in children with pulmonary hypertension. DESIGN: Prospective dose response study in which the effects of inhaled nitric oxide (NO) are compared with those of oxygen and intravenous prostacyclin. PATIENTS AND INTERVENTIONS: The vasodilator test was performed in 20 patients in whom mean pulmonary artery pressure (PAPm) was > or = 40 mm Hg and /or pulmonary vascular resistance index was > or = 4 Um2. Haemodynamic effects of inhaled NO (20, 40, and 80 ppm) at a fractional inspired oxygen (FiO2) value of 0.3, pure oxygen, oxygen at FiO2 0.9-1.0 combined with NO as above or with intravenous prostacyclin at 10 and 20 ng/kg/min were measured. RESULT: NO decreased PAPm with a dose response from 20 to 40 ppm (mean change at 40 ppm-5.50, 95% confidence interval (CI) -7.98 to -3.02 mm Hg. Maximal decrease in the ratio of pulmonary to systemic vascular resistance was achieved with a combination of NO 80 ppm and oxygen (-0.18, 95% CI -0.26 to -0.10). Increase in the pulmonary flow index was greatest with pure oxygen in those with an intracardiac shunt (8.52, 95% CI -0.15 to 17.20 l/min/m2). Neither NO nor oxygen altered systemic arterial pressure but intravenous prostacyclin lowered systemic arterial pressure and resistance. CONCLUSIONS: NO selectively reduces pulmonary vascular resistance and pressure maximally at 40 ppm. Oxygen reduces pulmonary vascular resistance and NO potentiates this reduction without affecting the systemic circulation. Prostacyclin vasodilates the pulmonary and the systemic circulations.

Measured versus predicted oxygen consumption in children with congenital heart disease.

OBJECTIVE: To compare measured and predicted oxygen consumption (VO2) in children with congenital heart disease. DESIGN: Retrospective study. SETTING: The cardiac catheterisation laboratory in a university hospital. PATIENTS: 125 children undergoing preoperative cardiac catheterisation. INTERVENTIONS: VO2 was measured using indirect calorimetry; the predicted values were calculated from regression equations published by Lindahl, Wessel et al, and Lundell et al. Stepwise linear regression and analysis of variance were used to evaluate the influence of age, sex, weight, height, cardiac malformation, and heart failure on the bias and precision of predicted VO2. An artificial neural network was trained and used to produce an estimate of VO2 employing the same variables. The various estimates for VO2 were evaluated by calculating their bias and precision values. RESULTS: Lindahl's equation produced the highest precision (+/- 42%) of the regression based estimates. The corresponding average bias of the predicted VO2 was 3% (range -66% to 43%). When VO2 was predicted according to regression equations by Wessel and Lundell, the bias and precision were 0% and +/- 44%, and -16% and +/- 51%, respectively. The neural network predicted VO2 from variables included in the regression equations with a bias of 6% and precision +/- 29%; addition of further variables failed to improve this estimate. CONCLUSIONS: Both regression based and artificial intelligence based techniques were inaccurate for predicting preoperative VO2 in patients with congenital heart disease. Measurement of VO2 is necessary in the preoperative evaluation of these patients.