SummaryIn this study the effect of phenylephrine and norepinephrine for the treatment of systemic hypotension were evaluated in patients with chronic pulmonary hypertension. When systemic hypotension (systolic arterial pressure , 100 mmHg) occurred following induction of anaesthesia, either phenylephrine or norepinephrine were infused in a random manner to raise the systolic blood pressure by 30% and 50% above baseline values. Norepinephrine decreased the ratio of pulmonary arterial pressure to systemic blood pressure without a change in cardiac index. However, phenylephrine did not increase arterial blood pressure by more than 30% from baseline in one-third of patients and decreased cardiac index without a significant decrease in ratio of pulmonary arterial pressure to systemic blood pressure. These vasoconstrictors showed different systemic and pulmonary haemodynamic effects in patients with chronic pulmonary hypertension as compared to acute pulmonary hypertension. Norepinephrine was considered to be preferable to phenylephrine for the treatment of hypotension in patients with chronic pulmonary hypertension. Pulmonary hypertension may result from a number of different conditions producing a chronic increase in pulmonary arterial pressure (PAP). Generally, PAP . 35 mmHg systolic and 15 mmHg diastolic pressure or a mean pressure . 20 mmHg at rest or 30 mmHg with exercise is indicative of pulmonary hypertension [1]. In the vast majority of patients, pulmonary hypertension is secondary to cardiac or pulmonary disease [2].The clinical significance of pulmonary hypertension lies in the resultant right ventricular failure and consequent left ventricular failure [3]. Right ventricular performance is governed by preload, afterload, contractility and heart rate. In contrast to the left ventricle, small increases in right ventricular afterload are associated with a sharp decrease in right ventricular ejection fraction [4]. The therapy and prevention of right ventricular failure caused by pulmonary arterial hypertension requires the combination of vasodilators producing a decrease in pulmonary vascular resistance (PVR) and a peripheral vasoconstrictor to produce an increase in coronary blood flow [5].Most patients with chronic pulmonary hypertension undergoing mitral valvular surgery are hypovolaemic when they arrive in the operating theatre due to longterm diuretic therapy. Systemic hypotension frequently occurs following induction of anaesthesia. Systemic hypotension should be treated vigorously in these patients, the ideal drug being one which increases the systemic arterial blood pressure (SBP) but producing minimal effects on pulmonary arterial pressure. A number of studies in animal models or in patients with acute pulmonary hypertension have reported that phenylephrine or norepinephrine effectively increased SBP with an q 2002 Blackwell Science Ltd 9

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