NO INHALATION IN HEART-SURGERY PROCEDURES - RELEVANCE FOR RIGHT-SIDE HEART FUNCTION

The right ventricle is more jeopardized by a cardiopulmonary bypass th an the left one. Impaired right ventricular performance may profit fro m an afterload reduction. A selective reduction in pulmonary artery pr essure (PAP) or pulmonary vascular resistance (PVR) without impairment of the systemic circulation seems to be possible by inhalation of nit ric oxide (NO). Therefore in the present study we looked for influence s of NO inhalation on PAP, PVR and right heart parameters immediately after weaning from the bypass. The dependence of endothelial function on age, preoperative heart function and extracorporeal circulation is well established. The relevance of such parameters on NO inhalation wa s also investigated. Methods. After ethical approval and informed cons ent were obtained, 20 patients with moderately increased PAP were incl uded in the study. Ten patients inhaled NO at a concentration of 30 pp m; the other group served as a control group. Measurement points were 10 min after the end of extracorporeal circulation (baseline), 3, 10, and 20 min after the start, as well as 10 min after the end of NO inha lation. NO was injected near the tube into the tubing system during in spiration; dosage and monitoring of the concentration were achieved by means of a chemiluminometer. Measured parameters consisted of PAP, PV R, right ventricular ejection fraction and volumes, systemic blood pre ssure and resistance, central venous pressure, pulmonary capillary wed ge pressure, and oxygenation parameters (p(a)O(2), p(v)O(2), p(a)CO(2) ). Results. The decrease in PAP (from 29.7+/-3.9 to a minimal 25.4+/-4 .3 mm Hg, P<0.05) and in PVR (from 169.4+/-51.9 to a minimal 116.3+/-6 0.9 dyn . s . cm(-5), P . 0.05) did not improve right heart function. A similar significant increase in SVR was observed in the NO group and in the control group. Age, haemodynamic parameters or duration of the ischaemic phase of the cardiopulmonary bypass did not influence the c ourse of PAP or PVR. Changes in PAP (from 30.0+/-4.0 to a minimal 26.7 +/-3.6 mm Hg, P<0.05) and PVR (from 149.0+/-41.5 to a minimal 125.2+/- 51.5 dyn . s . cm(-5), in the control group were not statistically dif ferent from those in the NO group. Indicators of intoxication like an increase in NO2 or methaemoglobin concentrations or changes in complia nce or resistance were not observed. Conclusions. Patients with modera te pulmonary hypertension did not profit fr om NO inhalation immediate ly after weaning from the cardiopulmonary bypass. The decreases in PAP and PVR found in the NO or control group did not improve right-heart Function. When the NO and control group were compared, specific effect s of NO inhalation on PAP and PVR must be questioned This could perhap s be explained by data from animal experiments, which found high endog enous NO levels in situations with elevated cytokine levels. Cytokines are increased after extracorporeal circulation. Oxygenation was not i mpaired by inhalation of relatively high concentrations of NO. For all investigations with NO inhalation not preceded by steady-state condit ions, a control group is recommended.