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PREOPERATIVE EVALUATION AND RISK FACTORS

Background

The 2019 update from the American Heart Association estimated that approximately 116 million US adults (46%) had hypertension, with 20% of them unaware of the diagnosis and 50% not adequately controlled.1 With 27 million noncardiac surgical procedures performed annually in the US,2 hypertension is a commonly seen comorbid condition, and uncontrolled hypertension is the most frequently cited cause of day of surgery cancellations. Complicating matters, there are no evidence-based guidelines to give health care providers direction on assessment and preoperative optimization as there are for chronic hypertension.3

Preoperative Assessment

The objective of the preoperative history, physical exam, and lab evaluation is to identify red flags that may predispose the patient to perioperative organ complications related to acute elevations in blood pressure. In addition to blood pressure measurement, this evaluation should include the duration of hypertension, medications and compliance, degree of BP control, and associated comorbidities, such as ischemic heart disease, heart failure, stroke, and chronic kidney disease. The ambulatory setting is the best time to establish baseline blood pressure.

Risk Factors for Perioperative Hypertension

Multiple studies using univariate analysis have noted an association with hypertension and various postoperative complications. This association tends to disappear in multivariable analysis when other comorbid conditions are considered, and therefore hypertension per se is not an independent risk factor for perioperative complications. However, the type of surgery, etiology of the hypertension, level of blood pressure, use of antihypertensive medications, and associated comorbidities can affect the risk of perioperative hypertension and postoperative complications. Certain surgeries, including coronary artery bypass graft, aortic aneurysm repair, and carotid endarterectomy, increase risk of perioperative hypertension. Patients undergoing pheochromocytoma resections as well as those with an undiagnosed pheochromocytoma are at risk of acute elevations of blood pressure due to tumor release of catecholamines. Mild to moderate hypertension (<180/110 mmHg) does not appear to increase risk, but BP>180/110 mmHg is controversial. Being on antihypertensive medications as opposed to no treatment tends to minimize perioperative blood pressure fluctuations. Abrupt withdrawal of certain antihypertensive medications, such as clonidine and beta-blockers, can result in rebound hypertension. Recreational use of cocaine can also be associated with elevated blood pressure. Hypertension with evidence of end organ damage may increase risk, but this is primarily related to the comorbid conditions rather the blood pressure alone.

Red Flags: Risk of Uncontrolled Hypertension

Patients presenting with an elevated blood pressure at the time of preoperative evaluation should be considered to have undiagnosed or poorly controlled hypertension or anxiety related to the surgical procedure. Secondary causes may be considered but are not the usual cause. Preoperative mean arterial blood pressure measurements tend to be approximately 11 mmHg lower than preinduction levels. This difference tended to be greater in patients with lower preoperative blood pressures and ...

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