Abstract Hypertension occurs commonly during the immediate post-operative period in patients who have undergone cardiac surgery. Careful monitoring is necessary and control of blood pressure often involves the use of vasodilator drugs such as sodium nitroprusside (SNP). Sensitivity to intravenous SNP varies from patient to patient and may change during its administration. Accurate delivery, by altering the infusion pump rate, can be difficult for nurses to achieve. In Glasgow Royal Infirmary a computer-controlled system has been developed which analyses the blood pressure waveforms from a cardiovascular monitor and instructs the infusion pump to deliver the appropriate rate. A study has shown that the computer system does provide better control of patient's blood pressure than manual control.