Incidence and aetiology of perioperative hypertension.

The reported incidence of perioperative hypertension associated with coronary artery bypass-graft (CABG) surgery ranges from 30-80%, which may reflect the various definitions of the condition as well as differences in the patients' preoperative states. Systolic, diastolic and mean arterial blood pressures are variously used to define perioperative hypertension, but absolute values range from a target systolic blood pressure of below 170 mmHg in some studies to below 110 mmHg in others. Patients' preoperative states have been extensively studied to determine potential risk factors. The majority of these studies indicate that perioperative hypertension is predictive of perioperative cardiac morbidity, but others do not confirm this finding, rendering the issue unresolved. The consequences of perioperative hypertensive episodes include bleeding from vascular suture lines, cerebrovascular haemorrhage or subendocardial ischaemia, and are associated with a mortality rate that may approach 50%. Increases in peripheral vascular resistance (PVR), caused by elevated levels of circulating catecholamines, appear to be the primary aetiology. Antihypertensive agents which correct or prevent the increase in PVR would appear to be the most appropriate therapy. However, no single agent appears to be ideal for all hypertensive episodes, suggesting multiple potential aetiologies.