Hypertension and Surgery

Dr. Basit

• the most common medical reason for postponing surgery

• well known to be a risk factor for cardiovascular catastrophe

• 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/min 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/min.

• Patients with preexisting hypertension are more likely to experience intraoperative blood pressure lability, which may lead to myocardial ischemia.

• Blood pressure and heart rate slowly increase as patients recover from the effects of anesthesia during the immediate postoperative period.

PERIOPERATIVE RISKS ASSOCIATED WITH HYPERTENSION

• The level of risk is dependent upon the severity of hypertension.

• cardiovascular responses that potentially increase the risk of surgery• diastolic hdysfunction• systolic dysfunction• renal impairment• cerebrovascular and coronary occlusive disease

Severe hypertension 

• patients with untreated severe hypertension (mean systolic and diastolic pressure of 211 and 105 mmHg, respectively) have exaggerated hypotensive responses to the induction of anesthesia and marked hypertensive responses to noxious stimuli

Mild to moderate hypertension

• Patients with less marked hypertension (diastolic pressure less than 110 mmHg) do not appear to be at increased operative risk.

• 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

Secondary hypertension

• Patients with suspected secondary hypertension ideally should undergo a diagnostic evaluation prior to elective surgery.

• most patients are not at increased perioperative risk as long as the hypertension is not severe and serum electrolytes and renal function are normal.

MANAGEMENT OF PATIENTS ON CHRONIC ANTIHYPERTENSIVE

THERAPYOral antihypertensive medications should be

continued up to the time of surgery.

Safety of antihypertensive drugs preoperatively

• Diuretics

• ACE/ARB

• Ca channel blockers

• Centrally acting sympatholytic drugs

• Beta blockers

POSTOPERATIVE HYPERTENSION

A history of hypertension preoperatively is the most important risk factor for

postoperative hypertension

Indications for therapy

• Any patient who experiences a marked rise in blood pressure following surgery should be treated immediately.

• Remedial causes of hypertension such as pain, agitation, hypercarbia, hypoxia, hypervolemia, and bladder distention should be excluded or treated.

• Patients on chronic antihypertensive therapy should resume their usual medications postoperatively as needed.

• 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.

Choice of drugs

• 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 may be given parenteral furosemide or bumetanide

• Patients taking an ACE inhibitor may be given parenteral enalaprilat.

• Patients taking centrally acting agents can be given a clonidine patch.

• Patients taking calcium channel blockers can be given intravenous nicardipine.