Effects of protamine on nitric oxide level in the pulmonary circulation

Protamine reversal of heparin anticoagulation often causes systemic hypoten sion by releasing nitric oxide (NO) from vascular endothelium. We investiga ted the hypothesis that protamine prevents severe pulmonary vasoconstrictio n by increasing NO. Twenty patients undergoing elective coronary artery bypass graft surgery we re included in the study. Nitrite and nitrate levels -as end-metabolites of NO- were measured in blood samples obtained before and after protamine adm inistration. Mean arterial pressure, heart rate, mean pulmonary artery pres sure, central venous pressure and left atrial pressure were noted as hemody namic data. Nitrite levels were 4.64 +/- 0.67 mu mol in the right atrium and 4.84 +/- 0 .95 mu mol in the left atrium before protamine administration. The differen ce was insignificant statistically. These measurements were 4.85 +/- 0.92 i n the right atrium and 5.28 +/- 0.66 mu mol in the left atrium after protam ine administration. This increase was significant (P < 0.05). The measureme nts of nitrate levels were completely parallel with those of nitrite. Mean arterial pressures were 78.9 +/- 7.59 mm-Hg before protamine and 74.1 +/- 8 .55 mm-Hg after protamine (P = 0.03). The changes in other hemodynamic para meters were not significant. Protamine augments NO production and prevents the pulmonary circulation fro m possible vasoconstriction.