D.BASEM ELSAID ENANYLECTURER OF CARDIOLOGY

AINSHAMS UNIVERSITY

Hypertension: preoperative management

BLOOD PRESSURE RESPONSE DURING ANESTHESIA

--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.--In HTN may increase by 90 mmHg and heart rate by 40 beats per minute.--Intraoperative hypotension direct effects of the anesthetic, inhibition of the sympathetic nervous system, and loss of the baroreceptor reflex control of arterial pressure.--Patients with preexisting hypertension are more likely to experience intraoperative blood pressure lability (either hypotension or hypertension).--Postoperative: hypertensive individuals may experience significant increases in BP, HR.

--The ACC/AHA guidelines list uncontrolled hypertension as a "minor" risk factor for perioperative cardiovascular events.--Severe hypertensionexaggerated hypotensive responses to the induction of anesthesia and marked hypertensive responses to noxious stimuli.--Well-controlled hypertension responds similarly to normotensive subjects. --Elective surgery does not need to be delayed as long as the diastolic blood pressure is <110 mmHg and intraoperative and postoperative blood pressures are carefully monitored to prevent hypertensive or hypotensive episodes.--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.--When hypertension has caused end-organ disease such as congestive heart failure and renal insufficiency, the probability of adverse cardiac outcome in the perioperative period increases significantly.

-- Patients with suspected secondary hypertension (hypertension is severe and serum electrolytes and renal function are abnormal) ideally should undergo a diagnostic evaluation prior to elective surgery.--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.

MANAGEMENT OF PATIENTS ON CHRONIC ANTIHYPERTENSIVE THERAPY

--Should be continued up to the time of surgery (small sips of water on the morning):*With few exceptions, continuing antihypertensive medications is relatively safe.*Abruptly discontinuing some medications (eg, beta blockers, clonidine) may be associated with significant rebound hypertension.*There are risks associated with severe, uncontrolled hypertension.

*Diuretics:--Chronic diuretic therapy hypokalemia 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.

*ACEI, ARBs:--Can theoretically blunt the compensatory activation of the renin-angiotensin system during surgery prolonged hypotension.{seems reasonable to continue these drugs in HTN patients, 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}

*Calcium channel blockers:--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.*Withdrawal syndromes: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.*BB withdrawal also can lead to accelerated angina, myocardial infarction, or sudden death.**Thus, it is recommended that patients with 3 or more risk factor for CHD be given beta blockers perioperatively as decrease mortality

POSTOPERATIVE HYPERTENSION

--History of hypertension preoperatively--Pain, hypervolemia, and bladder distention --Excitement on emergence from anesthesia--Hypercarbia*Usually begins within 30 minutes of the completion of surgery and lasts approximately two hours.* Any patient who experiences a marked rise in blood pressure (systolic blood pressure above 180 mmHg or diastolic blood pressure greater than 110 mmHg) following surgery should be treated immediately.

Management

*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.*Therapy should be considered for patients once remedial causes have been excluded or treated.{same drugs used to treat patients with hypertensive emergencies}* 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.

--Patients taking diuretics parenteral furosemide or bumetanide.--Patients taking beta blockers parenteral propranolol, labetalol, or esmolol.--Patients taking an ACE inhibitor parenteral enalaprilat.--Patients taking centrally acting agents clonidine patch.--Patients taking calcium channel blockers intravenous nicardipine.

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