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J Thorac Cardiovasc Surg 1997;114:867-868
© 1997 Mosby, Inc.
LETTERS TO THE EDITOR |
Department of Pediatric Cardiologya
Department of Pediatricsb
Department of Cardiac Surgeryc
University of Graz
Auenbruggerplatz 30
A-8036 Graz, Austria
Reply to the Editor:
We would like to thank Dr. Day for his comments relating to our article.
1 On the basis of our study design, we cannot rule out whether the elevated central venous pressures and the transpulmonary pressure gradients may not have spontaneously improved without inhaled nitric oxide treatment in our study patients. However, diagnoses, preoperative selection criteria (in particular pulmonary vascular resistance), surgical technique, and perioperative and postoperative management of the study patients did not differ from those of other patients undergoing the Fontan procedure during the study period; these patients did not meet our selection criteria for nitric oxide treatment: central venous pressure greater than 20 mm Hg or transpulmonary pressure gradient greater than 10 mm Hg. As stated in our article, treatment with inhaled nitric oxide was started after conventional therapy had failed to improve the hemodynamic state. Previously, Kirklin and associates 2 demonstrated a continuous relation between elevated right atrial pressures early after the Fontan operation and the probability of death or takedown within 30 days after the operation. They reported a probability of death or Fontan takedown of 38% and 52% when the right atrial pressure 3 hours after operation exceeded 20 and 22 mm Hg, respectively. Only one of our 13 patients died in the early postoperative period. This patient died of cerebral hemorrhage 5 days after being weaned from nitric oxide therapy, in stable hemodynamic condition. Among the remaining 12 patients, there was only one late death, which occurred 14 months after the operation as a result of chronic cardiac failure. In the meantime the second step of total cavopulmonary connection was successfully performed in the four patients who had a bidirectional Glenn anastomosis. These four patients and the remaining seven patients (11/13 = 85%) are clinically well at a mean follow-up of 2.2 years (1.3 to 3.5 years). Although this study was not designed to assess clinical outcome, we believe that inhaled nitric oxide may have positively influenced the early postoperative course in this high-risk cohort.
Despite normal preoperative pulmonary vascular resistance, some patients have a transient elevation of pulmonary vascular resistance in the early postoperative period after Fontan operations. This elevation is caused by pulmonary endothelial dysfunction after cardiopulmonary bypass 3 or pulmonary vasoconstriction induced by hypoxia or acidosis. In our study patients, a transient elevation of pulmonary vascular resistance resulting from endothelial pulmonary dysfunction seems likely. Before the start of nitric oxide treatment, all study patients had high central venous pressures (22 ± 0.9 mm Hg, 16 to 25 mm Hg) and transpulmonary pressure gradients (14.2 ± 0.7 mm Hg, 11 to 19 mm Hg) associated with severe hemodynamic compromise. These conditions were present despite maximal conventional therapy and normal pH and carbon dioxide tension and after excluding cardiac and pulmonary causes of systemic venous hypertension by echocardiography and chest roentgenograms, respectively. After starting nitric oxide treatment, all patients had uniform improvement of hemodynamic condition and oxygenation. Unfortunately, we did not use the data at the start of nitric oxide treatment as baseline values in our study. Thus, on the basis of our study design, we cannot exclude a withdrawal phenomenon that transiently raises pulmonary vascular resistance even after a short exposure of low-dose nitric oxide therapy.
We agree with Dr. Day that appropriate preoperative patient selection has the most important influence on clinical outcome after Fontan operations. The postoperative use of inhaled nitric oxide is not a substitute for treatment of patients in whom the Fontan procedure is inappropriate. We believe that inhaled nitric oxide may rather be an additional therapeutic option in the postoperative management after Fontan operations. In accordance with Goldman and coworkers, 4 we suggest that in the early postoperative period patients with high central venous pressures or transpulmonary pressure gradients associated with cardiocirculatory compromise should be offered a trial of inhaled nitric oxide after failure of conventional treatment and before considering a Fontan takedown. A trial of inhaled nitric oxide may also be of value to direct further investigations toward anatomic and surgically remediable obstructions of pulmonary blood flow. 5
However, these initial encouraging results of postoperative inhaled nitric oxide therapy in a small number of patients having either the Fontan or Glenn operation warrant further investigations in a larger cohort of patients. A prospective randomized study may clarify the influence of inhaled nitric oxide on postoperative morbidity and mortality and long-term outcome, respectively.
12/8/84444
References
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