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Preoperative hypertension
1. D . B A S E M E L S A I D E N A N Y
L E C T U R E R O F C A R D I O L O G Y
A I N S H A M S U N I V E R S I T Y
Hypertension: preoperative
management
2. 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.
3. --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.
4. -- 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.
5. 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.
6. *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.
7. *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}
8. *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
9. 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.
10. 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.
