Isolated systolic hypertension and anaesthesia

Do we need to change the diagnostic criteria for hypertension in our practice? In two separate articles, Poulter 1 and Wilkinson 2 identified the importance of isolated systolic hypertension (ISH) as a significant predictor of future cardiac morbidity and mortality. The British Hypertension Society (BHS) also recommended, in recently published guidelines, drug therapy in people with sustained systolic blood pressure (SBP) greater than or equal to 160 mmHg, and the decision to treat sustained SBP between 140 and 159 mmHg to be made according to the presence or absence of other risk factors. In his article, Poulter referred to the Framingham data, which challenged the notion that diastolic blood pressure (DBP) alone is chiefly responsible for the cardiovascular sequelae of hypertension. Compared with DBP, SBP correlates more strongly with stroke, congestive heart failure, coronary artery disease, declining renal function and left ventricular hypertrophy. According to the latest BHS guidelines, target blood pressure in non-diabetic patients should be 140/85 mmHg, and in patients with diabetes < 140/80 mmHg. In anaesthetic practice, however, the attitude towards cardiac disease in general, and hypertension in particular, has not changed over the last 50 years. Ischaemic heart disease and hypertension are considered to be associated with operative risk. Having said that, Goldman did not include hypertension as one of the independent risk factors in his famous pre-operative cardiac risk factors in non-cardiac surgery. Pre-operative management of hypertension has swung from one extreme to another. With the advent of antihypertensive drug therapy in the early 1950s and the introduction of potent antihypertensive drugs, such as methyl dopa and guanethidine, fears were expressed that cardiovascular homeostasis would be adversely affected during anaesthesia and surgery. Thus, it was commonly proposed that antihypertensive therapy should be withdrawn prior to elective surgery 3. In fact, Goldman and Caldera 4 suggested that elective surgery in the absence of ideal antihypertensive control need not subject patients to an added clinical risk provided DBP is stable, not higher than 110 mmHg and peri-operative blood pressures are closely monitored and treated to prevent hypertensive or hypotensive episodes. The postponement of scheduled surgery because of incidentally discovered mild to moderate hypertension causes inconvenience to patients and doctors, as well as hospital management. Adequate blood pressure control may take weeks, if not months, to achieve. At the same time, the foregoing data, which suggest beyond doubt that ISH is a definitive risk factor for cardiac morbidity and mortality in the community, cannot be ignored. The million-pound question now is that should we, as peri-operative physicians, take this as a gospel fact? Or should we wait for more prospective randomised trials of pre-operative blood pressure control of hypertensive patients to establish the effect of anaesthesia and surgery on the outcome in these patients? The answer to the first question is that we should, since we live in the era of evidence-based medicine. Any inconvenience would certainly be justified if postponing surgical procedures until hypertension has been controlled decreases the risk of peri-operative complications. However, the answer is not as easy for the second question, as waiting may lead to more lives being put at risk.