Blood pressure disturbances

1

What blood pressure value is considered hypertensive?

The definitions for blood pressure (BP) categories changed in 2017 according to the guidelines released by the American Heart Association/American College of Cardiology. A normal BP is less than 120/80 mm Hg. An elevated BP is a systolic BP of 120 to 129 mm Hg and a diastolic BP less than 80 mm Hg. Stage 1 hypertension (HTN) is a systolic BP of 130 to 139 mm Hg or a diastolic BP of 80 to 89 mm Hg. Stage 2 HTN is a systolic BP of at least 140 mm Hg or a diastolic BP of at least 90 mm Hg. A hypertensive crisis is defined as a systolic BP greater than 180 mm Hg or a diastolic BP greater than 120 mm Hg. A hypertensive crisis is considered hypertensive urgency if there is no evidence of end-organ damage or a hypertensive emergency if there is evidence of end-organ damage. End-organ damage involves the development of posterior reversible encephalopathy syndrome, acute kidney injury, heart failure, and subsequent pulmonary edema among others. BP changes throughout the day and can be affected by posture, exercise, medications, smoking, caffeine ingestion, and mood. HTN cannot be diagnosed on the basis of one abnormal BP reading but an average of at least two measurements on at least two different occasions.

2

What causes hypertension?

• Primary (or essential) HTN: unknown cause; more than 90% of all cases fall into this category

• Medications: oral contraceptives, weight-loss medications, stimulants, corticosteroids

• Endocrine: Cushing syndrome, hyperaldosteronism, pheochromocytoma, thyrotoxicosis, acromegaly

• Renal: chronic pyelonephritis, renovascular stenosis, glomerulonephritis, polycystic kidney disease

• Neurogenic: increased intracranial pressure, autonomic hyperreflexia

• Miscellaneous: obesity, hypercalcemia, preeclampsia, acute intermittent porphyria, obstructive sleep apnea, pain, anxiety, illicit drugs

3

What are the consequences of chronic HTN?

Chronically hypertensive patients are at risk for developing end-organ disease, including left ventricular hypertrophy, systolic and diastolic heart failure, coronary artery disease with increased risk of myocardial infarction, chronic renal failure, retinopathy, ischemic stroke, and intracerebral hemorrhage (ICH).

4

Why should most antihypertensives be taken up until the time of surgery?

A well-controlled hypertensive patient has less intraoperative BP lability (either HTN or hypotension). Acute withdrawal of antihypertensives, specifically β blockers and α ₂ agonists, may precipitate rebound HTN or myocardial ischemia. With a few exceptions, it is recommended to continue antihypertensive therapy until the time of surgery and restart therapy as soon as possible after surgery ( Table 30.1 ).

5

Which antihypertensives should be held on the day of surgery?

Although there is no universal agreement, many believe renin-angiotensin system antagonists (angiotensin-converting-enzyme [ACE] inhibitors and angiotensin II receptor blockers [ARBs]) should be held the day of surgery. Diuretics may be withheld when depletion of intravascular volume is a concern.