Hypertension is a minor clinical predictor of increased preoperative cardiovascular risk. Hypertension is classified as primary (essential or idiopathic) in 95 percent of cases. Secondary hypertension is found in 5 percent of patients. The five most common causes of secondary hypertension include renal artery stenosis, primary hyperaldosteronism, Cushing syndrome, pheochromocytoma, and aortic stenosis. Several studies have suggested that intraoperative blood pressure changes may be greater in untreated hypertensive patients. Patients are therefore advised to take their antihypertensive medications on the day of surgery, with the exception of diuretics. These are withheld to avoid hypovolemia or hypokalemia.
Application of ASA grading to hypertensive disease classifies those patients with well-controlled hypertension on a single agent as ASA Class 2
patients and those patients with poorly controlled hypertension and on multiple drugs as ASA Class 3 patients. Elegant studies by Goldman3 revealed that elective surgery in patients with inadequately controlled hypertension was not associated with increased risk of perioperative cardiac morbidity provided the diastolic blood pressure was less than 110 mmHg and perioperative blood pressure was closely monitored. Discontinuation of antihyper-tensive therapy can be dangerous. Examples include rebound hypertension after discontinuation of a centrally acting a2-adrenergic agonist such as clonidine or congestive heart failure (CHF) in the perioperative period after withholding ACE inhibitors. p-Adrenergic blockade should be continued throughout the preoperative period. Myocardial ischemia is associated with tachycardia but not with acute changes in blood pressure. Beta-blockers such as atenolol are found to be cardio protective. A study by Mangano and Goldman4 has shown that beta-blockers given pre- and postoperatively can reduce the risk of death in patients with known coronary artery disease (CAD) or at risk for CAD. Contraindications to the use of beta-blockers include a heart rate of less than 55, systolic blood pressure of less than 100, bronchospasm, CHF, and patients with second- or third-degree heart block. A recent myocardial infarction (MI) is the single most important factor that can predict perioperative infarction. The risk is greatest within the first 3 months after an infarction. In a patient with a recent MI, elective surgery should be postponed to after 6 months, when the risk of reinfarction drops to 4.5 percent as opposed to 30 percent within 3 months. Urgent surgery should be preceded by coronary artery bypass or stenting.
In cases of emergency surgery, uncontrolled hypertension should not be a deterrent to proceeding with surgery. Short-acting beta-blockers can be used to control hypertension in the perioperative period. Ketamine should be avoided, as tachycardia, hypertension, and increased intracranial pressure are all associated with its use. Most importantly, perioperative treatment of hypertension with the parenterally administered drugs mentioned earlier should be undertaken only after optimization of ventilation, oxygenation, and circulation in the patient.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...