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PERIOPERATIVE HYPERTENSION - AN UPDATE Norman M Kaplan, MD |
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INTRODUCTION |
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Preexisting hypertension is the most common medical reason for postponing surgery. Hypertension is well known to be a risk factor for cardiovascular catastrophe, a risk that logically extends into the perioperative period. In a case-control study of 76 patients who died of a cardiovascular cause within 30 days of elective surgery, a preoperative history of hypertension was four times more likely than among 76 matched controls. |
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The issues regarding the perioperative management of the patient with hypertension are reviewed here. |
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BLOOD PRESSURE RESPONSE DURING ANESTHESIA |
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Sympathetic activation during the induction of anesthesia can cause the blood pressure to rise by 20 to 30 mmHg and the heart rate to increase by 15 to 20 beats per minute in normotensive individuals. These responses may be more pronounced in patients with untreated hypertension in whom the systolic blood pressure can increase by 90 mmHg and heart rate by 40 beats per minute. |
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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, and loss 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 intraoperative blood pressure lability (either hypotension or hypertension), which may lead to myocardial ischemia. |
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Blood pressure and heart rate slowly increase as patients recover from the effects of anesthesia during the immediate postoperative period. Hypertensive individuals in particular may experience significant increases in these parameters. |
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PERIOPERATIVE RISKS ASSOCIATED WITH HYPERTENSION |
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Preexisting hypertension can induce a variety of cardiovascular responses that potentially increase the risk of surgery, including diastolic dysfunction from left ventricular hypertrophy, systolic dysfunction leading to congestive heart failure, renal impairment, and cerebrovascular and coronary occlusive disease. The level of risk is dependent upon the severity of hypertension |
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However, much of the evidence for the impact of preoperative hypertension comes from uncontrolled studies performed before current (more effective) management was available. Furthermore, it is still unclear whether postponing surgery to achieve blood pressure control will lead to reduced cardiac risk. The ACC/AHA guidelines list uncontrolled hypertension as a "minor" risk factor for perioperative cardiovascular events . |
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Severe hypertension |
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An early study found that patients with untreated severe hypertension (mean systolic and diastolic pressure of 211 and 105 mmHg, respectively) had exaggerated hypotensive responses to the induction of anesthesia and marked hypertensive responses to noxious stimuli. Patients with well-controlled hypertension responded similarly to normotensive subjects. Other studies have found that a diastolic pressure over 110 mmHg immediately before surgery is associated with a number of complications including dysrhythmias, myocardial ischemia and infarction, neurologic complications, and renal failure. |
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Mild to moderate hypertension |
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Patients with less marked hypertension (diastolic pressure less than 110 mmHg) do not appear to be at increased operative risk. This was illustrated in a study of 676 operations involving a general anesthetic in patients over the age of 40. Subjects were divided into five groups: |
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Normotensive patients (group I, no medications; and group II on diuretics for non-hypertensive reasons) were significantly less likely to experience perioperative hypertension than patients normotensive on medication (group III), hypertensive despite treatment (group IV), and untreated hypertension (group V) |
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Patients with inadequately treated or untreated hypertension (groups IV and V) were no more likely to experience cardiac complications than normotensive patients not taking diuretics (group I). |
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Among patients with a history of hypertension (groups III, IV, and V), multivariate analysis identified only two independent risk factors for cardiac complications: the preoperative cardiac risk index score (which does not include hypertension) Table2; and marked reductions in intraoperative blood pressure (a decrease to less than 50 percent of preoperative levels or a decrease of 33 percent or more for more than 10 minutes). |
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These results suggest that elective surgery in patients with hypertension does not need to be delayed as long as the diastolic blood pressure is less than 110 mmHg and intraoperative and postoperative blood pressures are carefully monitored to prevent hypertensive or hypotensive episodes. On the other hand, when hypertension has caused end-organ disease such as congestive heart failure and renal insufficiency, the probability of adverse cardiac outcomes in the perioperative period increases significantly. |
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The impact of systolic hypertension on operative risk is less clear. One study of patients undergoing carotid endarterectomy found that a systolic pressure greater than 200 mmHg was associated with an increased risk of postoperative hypertension and neurologic deficits. Patients with isolated systolic hypertension are at increased risk for cardiovascular morbidity after coronary artery bypass surgery . |
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Secondary hypertension |
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The physical examination and simple laboratory tests can rule out some of the rare but important causes of hypertension. Further evaluation to exclude secondary hypertension is rarely warranted before necessary surgery. If pheochromocytoma is a serious possibility, surgery should be delayed to permit its exclusion. A loud abdominal bruit may suggest renal artery stenosis. A radial to femoral artery pulse delay suggests coarctation of the aorta, whereas hypokalemia in the absence of diuretic therapy raises the possibility of hyperaldosteronism. |
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MANAGEMENT OF PATIENTS ON CHRONIC ANTIHYPERTENSIVE THERAPY |
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Oral antihypertensive medications should be continued up to the time of surgery. This recommendation is based upon the following observations: |
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With few exceptions, continuing antihypertensive medications is relatively safe. |
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Abruptly discontinuing some medications (eg, beta blockers, clonidine) may be associated with significant rebound hypertension. |
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There are risks associated with severe, uncontrolled hypertension. |
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Table1: "Perioperative medication management" |
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Drug |
Day Before Surgery |
Day of Surgery |
During Surgery |
After Procedure |
Beta-blockers |
Usual dose |
Usual dose on morning of surgery with sip of water) |
IV bolus or infusion (usually not required) |
Continue IV dose until medication can be taken PO |
Calcium channel blockers |
Usual dose |
Usual dose on morning of surgery with sip of water |
IV bolus or infusion (usually not required) |
Continue IV dose until medication can be taken PO |
ACE inhibitors |
Stop day before |
Do not take day of surgery |
IV formulations (usually not required) |
Continue IV dose until medication can be taken PO |
Diuretics |
Stop day before |
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IV beta-blockers/IV calcium channel blockers |
Restart when patient on oral liquids |
Potassium supplements |
Stop day before; consider checking potassium level |
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Restart when patient on oral liquids |
Central-acting sympatholytics |
Usual dose |
Usual dose on morning of surgery with sip of water |
Transdermal clonidine/IV methyldopa |
Restart when patient on orals liquids |
Peripheral sympatholytics |
Usual dose |
Usual dose on morning of surgery with sip of water |
Any IV formulation (usually not required) |
Restart when patient on oral liquids |
Alpha-blockers |
Usual dose |
Usual dose on morning of surgery with sip of water |
Any IV formulation (usually not required) |
Restart when patient on oral liquids |
Vasodilators |
Usual dose |
Usual dose on morning of surgery with sip of water |
IV formulation (usually not required) |
Continue IV dose until medication can betaken PO |
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Safety of antihypertensive drugs preoperatively |
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Most antihypertensive agents can be continued until the time of surgery, taken with small sips of water on the morning of surgery. For perioperative drug management for Patients with Hypertension See Table1. |
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The following is a brief summary of recommendations for the various classes of antihypertensive drugs. |
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Diuretics |
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Patients in whom chronic diuretic therapy has caused hypokalemia may have potentiation of the effects of muscle relaxants used during anesthesia, as well as predisposition to cardiac arrhythmias and paralytic ileus. Physicians should be aware of the potential perioperative risks associated with diuretics and pay close attention to volume and potassium replacement. |
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Angiotensin converting enzyme inhibitors and angiotensin II receptor blockers |
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Angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers can theoretically blunt the compensatory activation of the renin-angiotensin system during surgery and result in prolonged hypotension. One study of 150 vascular surgery patients found that the incidence of hypotension during anesthetic induction was significantly lower in patients who stopped taking captopril or enalapril the evening before surgery than in those who took the medication on the morning of surgery. A high incidence of severe hypotension in patients on an angiotensin II receptor blocker who underwent general anesthesia has also been reported. |
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Although there are insufficient data upon which recommendations can be based, it seems reasonable to continue these drugs in patients who are taking them for the management of hypertension. On the other hand, it is also reasonable to withhold them on the morning of surgery in patients who are taking them for congestive heart failure in whom the baseline blood pressure is low, to avoid significant hypotension during the induction of anesthesia. |
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Calcium channel blockers |
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Patients receiving calcium channel blockers may have an increased incidence of postoperative bleeding, probably due to inhibition of platelet aggregation. The multiple benefits of these drugs probably outweigh the small risk of continued therapy. |
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Withdrawal syndromes |
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The centrally acting sympatholytic drugs (eg, clonidine, methyldopa, and guanfacine) and the beta blockers are associated with acute withdrawal syndromes that can lead to adverse perioperative events. These drugs should not be abruptly stopped perioperatively. |
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Centrally acting sympatholytic drugs |
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The primary clinical manifestation following abrupt cessation of clonidine therapy is acute, rebound hypertension above the pretreatment level. Rebound hypertension usually occurs after abrupt cessation of fairly large oral doses (eg, greater than 0.8 mg/day), but has also been noted with transdermal clonidine. Withdrawal symptoms have also been reported with methyldopa and guanfacine withdrawal but are less likely because of their slower onset of action. |
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Beta blockers |
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Beta blockers reduce intraoperative myocardial ischemia. Thus, in addition to a rise in blood pressure, beta blocker withdrawal in patients with underlying coronary disease can lead to accelerated angina, myocardial infarction, or sudden death. |
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Furthermore, atenolol or bisoprolol given before surgery to patients with, or at high risk for, coronary heart disease (CHD) decreases mortality. Thus, it is recommended that patients with one or more risk factor for CHD be given beta blockers perioperatively. |
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POSTOPERATIVE HYPERTENSION |
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A history of hypertension preoperatively is the most important risk factor for postoperative hypertension. Other factors contributing to the development of hypertension were pain (35 percent), excitement on emergence from anesthesia (16 percent), and hypercarbia (15 percent). The type of surgery may influence the likelihood of developing postoperative hypertension. |
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As illustrated in a study of 1844 patients, hypertension usually begins within 30 minutes of the completion of surgery and lasts approximately two hours. On the other hand, some patients with preexisting hypertension may experience normalization of blood pressure as a nonspecific response to surgery. This response can persist for months, usually followed by a gradual return to preoperative levels. |
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Indications for therapy |
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Any patient who experiences a marked rise in blood pressure following surgery should be treated immediately. |
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The following approach can be used in other cases: |
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Remedial causes of hypertension such as pain, agitation, hypercarbia, hypoxia, hypervolemia, and bladder distention should be excluded or treated. |
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Patients on chronic antihypertensive therapy should resume their usual medications postoperatively as needed. Those who cannot take oral medications should be given a comparable alternative (see below). |
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Therapy should be considered for patients with a sustained systolic blood pressure above 180 mmHg or diastolic blood pressure greater than 110 mmHg, once remedial causes have been excluded or treated. |
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Choice of drugs |
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A number of parenteral antihypertensive medications are available for patients who are unable to take oral medications postoperatively. These are the same drugs used to treat patients with hypertensive emergencies . (Table3) Without any data from controlled trials to indicate which is best, the experience of the surgeons, anesthesiologists, and internists who are caring for the patients should guide the choice. |
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With the exception of beta blockers and clonidine, it is not necessary for patients receiving chronic antihypertensive therapy who are unable to resume oral medications to continue the same class of drugs postoperatively. Nevertheless, in many cases a comparable parenteral alternative is available. |
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Patients taking diuretics may be given parenteral furosemide or bumetanide. |
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Patients taking beta blockers may be given parenteral propranolol, labetalol, or esmolol. |
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Patients taking an ACE inhibitor may be given parenteral enalaprilat. |
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Patients taking centrally acting agents can be given a clonidine patch. |
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Patients taking calcium channel blockers can be given intravenous nicardipine. |
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SUMMARY AND RECOMMENDATIONS |
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Patients with well-controlled hypertension preoperatively are less likely to experience intraoperative blood pressure lability and postoperative complications than patients with poorly controlled hypertension. The ideal circumstance is to normalize blood pressure (eg, to less than 140/90 mmHg) for several months prior to elective surgery. However, it is not necessary to postpone elective procedures in patients with a blood pressure below 170/110 mmHg. |
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Elective surgery should be postponed in patients with blood pressures above 170/110 mmHg. Such patients who require urgent surgery should be treated with a parenteral drug acutely. |
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Patients who are taking chronic antihypertensive medications should continue taking their medication until the time of surgery. The drug can be administered with a sip of water on the morning of surgery and resumed postoperatively as needed. Alternative parenteral agents can be prescribed for patients who are unable to resume oral medications. |
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In particular, beta blockers and centrally acting agents such as clonidine should not be stopped acutely. If necessary, intravenous propranolol or labetalol can be administered to patients taking beta blockers or transdermal clonidine can be administered to patients taking clonidine. |
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Remedial causes of postoperative hypertension such as pain, agitation, hypercarbia, hypoxia, hypervolemia, and bladder distention should be excluded or treated. Once this has been done, therapy should be considered for patients with a persistent systolic blood pressure above 180 mmHg or a diastolic blood pressure above 110 mmHg. |
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Table2: Revised Goldman cardiac risk index (RCRI) |
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Six independent predictors of major cardiac complications* |
High-risk type of surgery (includes any intraperitoneal, intrathoracic, or suprainguinal vascular procedures) |
History of ischemic heart disease (history of MI or a positive exercise test, current complaint of chest pain considered to be secondary to myocardial ischemia, use of nitrate therapy, or ECG with pathological Q waves; do not count prior coronary revascularization procedure unless one of the other criteria for ischemic heart disease is present) |
History of HF |
History of cerebrovascular disease |
Diabetes mellitus requiring treatment with insulin |
Preoperative serum creatinine >2.0 mg/dL (177 mol/L) |
Rate of cardiac death, nonfatal myocardial infarction, and nonfatal cardiac arrest according to the number of predictors |
No risk factors - 0.4 percent (95% CI 0.1-0.8 percent) |
One risk factor - 1.0 percent (95% CI 0.5-1.4 percent) |
Two risk factors - 2.4 percent (95% CI 1.3-3.5 percent) |
Three or more risk factors - 5.4 percent (95% CI 2.8-7.9 percent) |
Rate of cardiac death & nonfatal MI, cardiac arrest or ventr.fibrillation, pulmonary edema, and/or complete heart block according to the No.of predictors and use nonuse or of beta blockers |
No risk factors - 0.4 to 1.0 percent versus <1 percent with beta blockers |
One to two risk factors - 2.2 to 6.6 percent versus 0.8 to 1.6 percent with beta blockers |
Three or more risk factors - >9 percent versus >3 percent with beta blockers |
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Table3: Parenteral drugs for treatment of hypertensive emergencies |
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Drug |
Dose |
Onset of action |
Duration of action |
Adverse effects |
Special indications |
Vasodilators |
Sodium nitroprusside |
0.25-10μg/kg/min as IV infusion |
Immediate |
1-2 min |
Nausea, vomiting, muscle twitching, sweating, thiocynate and cyanide intoxication |
Most hypertensive emergencies; caution with high intracranial pressure or azotemia |
Nicardipine hydrochloride |
5-15 mg/h IV |
5-10 min |
15-30 min, May exceed 4 h |
Tachycardia, headache, flushing, local phlebitis |
Most hypertensive emergencies except acute heart failure; caution with coronary ischemia |
Clevidipine |
1-2 mg/h IV with rapid titration to max of 16 mg/h |
1-2 min |
5-15 min |
Atrial fibrillation,nausea |
All hypertensive emergencies |
Fenoldopam mesylate |
0.1-0.3 μg/kg per min IV infusion |
<5 min |
30 min |
Tachycardia,headache, nausea,flushing |
Most hypertensive emergencies; caution with glaucoma |
Nitroglycerin |
5-100 μg/min as IV infusion |
2-5 min |
5-10 min |
Headache, vomiting,methemoglobinemia,tolerance withprolonged use |
Coronary ischemia |
Enalaprilat |
1.25-5 mg every 6 h IV |
15-30 min |
6-12 h |
Precipitous fall in pressure in high rennin states; variable response |
Acute left ventricular failure; avoid in acute myocardial infarction |
Hydralazine hydrochloride |
10-20 mg IV 10-40 mg IM |
10-20 min 20-30 min IM |
1-4 h IV 4-6 h IM |
Tachycardia,flushing, headache,vomiting, aggravation of angina |
Eclampsia |
Andrenergic inhibitors |
Labetalol hydrochloride |
20-80 mg IV bolus every 10 min 0.5-2.0 mg/min IV infusion |
5-10 min |
3-6 h |
Vomiting, scalp tingling, bronchoconstriction, dizziness, nausea, heart block, orthostatic hypotension |
Most hypertensive emergencies except acute heart failure |
Esmolol hydrochlorideΔ |
250-500 μg/kg/min by infusion; may repeat bolus after 5 min or increase infusion to 300 μg/min |
1-2 min |
10-30 min |
Hypotension, nausea, asthma, first-degree heart block, HF |
Aortic dissection, perioperative |
Hydralazine hydrochloride |
10-20 mg IV 10-40 mg IM |
10-20 min 20-30 min IM |
1-4 h IV 4-6 h IM |
Tachycardia,flushing, headache,vomiting, aggravation of angina |
Eclampsia |
Phentolamine |
5-15 mg IV bolus |
1-2 min |
10-30 min |
Tachycardia, flushing, headache |
Catecholamine excess |
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SOURCE: |
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1. Perioperative management of hypertension. Norman M Kaplan, MD. Uptodate.com |
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2. ACC/AHA 2007 Guidelines on Perioperative Cardiovascular Evaluation and Care for Noncardiac Surgery. Circulation. 2007; 116: e418-e500 |
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3. Perioperative hypertension management. Vasc Health Risk Manag. 2008 Jun; 4(3): 615–627. |