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  14/9/2019Perioperative management of hypertension - UpToDateissemym.bi-digital.com/uptodate1/16 Official reprint from UpToDate www.uptodate.com ©2019 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Per ioperative management of hypertension Author: John D Bisognano, MD, PhD Section Editors: Mark D Aronson, MD, George L Bakris, MD Deputy Editors: Lisa Kunins, MD, John P Forman, MD, MSc All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through:  Aug 2019. | This topic last updated:  Jul 15, 2019. INTRODUCTION Preexisting hypertension is the most common medical reason for postponing surgery [1].Hypertension is well known to be a risk factor for cardiovascular catastrophe, a risk that logicallyextends into the perioperative period [2,3]. In a case-control study of 76 patients who died of acardiovascular cause within 30 days of elective surgery, a preoperative history of hypertension wasfour times more likely than among 76 matched controls [4].The issues regarding the perioperative management of the patient with hypertension are reviewedhere. Intraoper ative management of hyper tensive patients is presented elsewhere. (See Anesthesia for patients with hypertension .) BLOOD PRESSURE RESPONSE DURING ANESTHESIA Sympathetic activation during the induction of anesthesia can cause the blood pressure to rise by 20to 30 mmHg and the heart rate to increase by 15 to 20 beats per minute in normotensive individuals[5]. These responses may be more pronounced in patients with untreated hypertension in whom thesystolic blood pressure can increase by 90 mmHg and the heart rate by 40 beats per minute.The mean arterial pressure tends to fall as the period of anesthesia progresses due to a variety of factors, including direct effects of the anesthetic, inhibition of the sympathetic nervous system, andloss of the baroreceptor reflex control of arterial pressure. These changes can result in episodes of intraoperative hypotension. Patients with preexisting hypertension are more likely to experience ®  14/9/2019Perioperative management of hypertension - UpToDateissemym.bi-digital.com/uptodate2/16 intraoperative blood pressure lability (either hypotension or hypertension) [6], which may lead tomyocardial ischemia [7].Blood pressure and heart rate slowly increase as patients recover from the effects of anesthesiaduring the immediate postoperative period. Hypertensive individuals, in particular, may experiencesignificant increases in these parameters [8]. PERIOPERATIVE RISKS ASSOCIATED WITH HYPERTENSION Preexisting hypertension can induce a variety of cardiovascular responses that potentially increasethe risk of surgery, including diastolic dysfunction from left ventricular hypertrophy, systolicdysfunction leading to congestive heart failure, renal impairment, and cerebrovascular and coronaryocclusive disease. The level of risk is dependent upon the severity of hypertension.However, much of the evidence for the impact of preoperative hypertension comes from uncontrolledstudies performed before contemporary (more effective) management was available. Furthermore, itis still unclear whether postponing surgery to achieve blood pressure control will lead to reducedcardiac risk [9]. The American College of Cardiology/American Heart Association (ACC/AHA)guidelines list uncontrolled hypertension as a minor risk factor for perioperative cardiovascular events [10]. Severe hypertension  — An early study found that patients with untreated severe hypertension(mean systolic and diastolic pressures of 211 and 105 mmHg, respectively) had exaggeratedhypotensive responses to the induction of anesthesia and marked hypertensive responses to noxiousstimuli [11]. Patients with well-controlled hypertension responded similarly to normotensive subjects.Other studies have found that a diastolic pressure over 110 mmHg immediately before surgery isassociated with a number of complications including dysrhythmias, myocardial ischemia andinfarction, neurologic complications, and renal failure [5]. (See Possible prevention and therapy of  ischemic acute tubular necrosis .) Mild to moderate hypertension  — Patients with less marked hypertension (diastolic pressure lessthan 110 mmHg) do not appear to be at increased operative risk. This was illustrated in a study of 676operations involving a general anesthetic in patients over the age of 40 years [6]. Subjects weredivided into five groups:Normotensive patients (group I, no medications; group II, on diuretics for nonhypertensivereasons) were significantly less likely to experience perioperative hypertension than patients whowere normotensive on medication (group III), who were hypertensive despite treatment (group ●  14/9/2019Perioperative management of hypertension - UpToDateissemym.bi-digital.com/uptodate3/16 These results suggest that elective surgery in patients with hypertension does not need to be delayedas long as the diastolic blood pressure is less than 110 mmHg and intraoperative and postoperativeblood pressures are carefully monitored to prevent hypertensive or hypotensive episodes. On theother hand, when hypertension has caused end-organ disease such as congestive heart failure andrenal insufficiency, the probability of adverse cardiac outcome in the perioperative period increasessignificantly [12]. (See Evaluation of cardiac risk prior to noncardiac surgery .) The impact of systolic hypertension on operative risk is less clear. One study of patients undergoingcarotid endarterectomy found that a systolic pressure greater than 200 mmHg was associated with anincreased risk of postoperative hypertension and neurologic deficits [13]. Patients with isolatedsystolic hypertension are at increased risk for cardiovascular morbidity after coronary artery bypasssurgery [2]. Secondary hypertension  — Patients with suspected secondary hypertension should ideally undergoa diagnostic evaluation prior to elective surgery (see Evaluation of secondary hypertension ).However, most patients are not at increased perioperative risk as long as the hypertension is notsevere and serum electrolytes and renal function are normal. An important exception is the patientwith pheochromocytoma, in whom operative mortality may be as high as 80 percent in unsuspectedcases [14]. (See Clinical presentation and diagnosis of pheochromocytoma .) MANAGEMENT OF PATIENTS ON CHRONIC ANTIHYPERTENSIVE THERAPY Oral antihypertensive medications should be continued up to the time of surgery. Thisrecommendation is based upon the following observations:IV), and who had untreated hypertension (group V) (8 and 6 versus 27, 25, and 20 percent,respectively).Patients with inadequately treated or untreated hypertension (groups IV and V) were no morelikely to experience cardiac complications than normotensive patients not taking diuretics (groupI). ●  Among patients with a history of hypertension (groups III, IV, and V), multivariate analysisidentified only two independent risk factors for cardiac complications: the preoperative cardiacrisk index score (which does not include hypertension (table 1)); and marked reductions inintraoperative blood pressure (a decrease to less than 50 percent of preoperative levels or adecrease of 33 percent or more for more than 10 minutes). ● With few exceptions, continuing antihypertensive medications is relatively safe. ●  14/9/2019Perioperative management of hypertension - UpToDateissemym.bi-digital.com/uptodate4/16 Safety of antihypertensive drugs preoperatively  — Most antihypertensive agents can becontinued until the time of surgery, taken with small sips of water on the morning of surgery. However,we typically hold angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers(ARBs) for a period of 24 hours prior to surgery. A more complete discussion of perioperativemedication management is found separately. (See Perioperative medication management , sectionon 'Cardiovascular medications'.)The following is a brief summary of recommendations for the various classes of antihypertensivedrugs. Diuretics  — Patients in whom chronic diuretic therapy has caused hypokalemia may havepotentiation of the effects of muscle relaxants used during anesthesia, as well as predisposition tocardiac arrhythmias and paralytic ileus [15]. Clinicians should be aware of the potential perioperativerisks associated with diuretics and pay close attention to volume and potassium replacement. (See Perioperative medication management , section on 'Diuretics'.) Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers  — It isreasonable to hold ACE inhibitors and ARBs for a period of 24 hours prior to surgery unless there is acompelling reason to continue them, such as with heart failure or with inadequately treatedhypertension that cannot be improved before surgery. Such drugs can theoretically blunt thecompensatory activation of the renin-angiotensin system during surgery and result in prolongedhypotension. Several studies have reported a higher incidence of hypotension in patients who took ACE inhibitors or ARBs prior to undergoing surgery [16-19]. As an example, one study of 150vascular surgery patients found that the incidence of hypotension during anesthetic induction wassignificantly lower in patients who stopped taking captopril or enalapril on the evening before surgery than in those who took the medication on the morning of surgery [16]. A high incidence of severehypotension in patients on an ARB who underwent general anesthesia has also been reported [17].(See Perioperative medication management , section on 'ACE inhibitors and angiotensin II receptor blockers'.) Calcium channel blockers  — Patients receiving calcium channel blockers may have anincreased incidence of postoperative bleeding, probably due to inhibition of platelet aggregation [20].The multiple benefits of these drugs probably outweigh the small risk of continued therapy.(See Perioperative medication management , section on 'Calcium channel blockers'.) Abruptly discontinuing some medications (eg, beta blockers, clonidine) may be associated withsignificant rebound hypertension. ● There are risks associated with severe, uncontrolled hypertension. (See 'Severe hypertension'above.) ●
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