. (1976). Thorax, 31,[332][333][334][335][336] (Emanuel, 1963). In general, it has been held that severe pulmonary hypertension was associated with greater operative risk, higher operative mortality, and a poorer long-term prognosis.However, a significant reduction in the level of pulmonary hypertension in some patients after mitral valve surgery and a more favourable longterm outlook have been reported (Dalen et al., 1967;Zener et al., 1972). Furthermore, Ward and Hancock (1975) suggested that extreme pulmonary hypertension should be regarded as a positive indication for early operation. In their series there was a high mortality in this group, but the prognosis was nonetheless considerably better than the natural history of the disease without surgical intervention. In our series in the last five years, only one of 16

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A merhod of protwine rirrarion, with rhe use of rhe 'Haemochron 400' system for reversal of heparmisarion ajler cardiopuhonary bypass is described. Twenty-three patients. average age 4 7 years. &going this procedure for either valve replacement or coronary artery bypass grafring were studied. Accurare reversal of heparinisation was achieved using comparative& small doses of protamine. A linear relationship between the dose ratio of protamine and heparin and rhe time interval between their respective ahinistrations was akjined where only a single dose of heparin had been administered. Key wonkBlood; anticoagulation, heparin. Measurement technques; protarnine requirements.Rotamine sulphate was introduced as an antagonist to heparin in 1937' and has become widely used for this purpose since the advent of cardiopulmonary bypass techniques. This drug, however, also has an anticoagulant property which was described 36 years prior to its introduction as a heparin antagonist.* Rotamine titration methods, originally des- who described only minimal short term effects on the coagulation system after protamine ovcrdoses of up to 800 mg per 70 kg subject. It has, however, been the experience of the authors that the anticoagulant property of protamine can be produced after considerably smaller doses have been administered for the reversal of heparinisation. MetbodHeparin was administered intra-operatively as a bolus intravenous dose of 3.0 mg/kg body weight prior to the insertion of the aortic, superior vena caval, and inferior vcna caval cannulae. An additional 80 mg heparin was added to the pump priming volume of two litres of Ringers lactate solution. Monitoring of the degree of anti--

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