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Hypertensive
emergencies
are events that require immediate blood pressure reduction to decrease or
prevent target organ damage. The
blood pressure usually should not be brought down to the normal range
immediately after the event.
-Examples
of hypertensive emergencies include acute myocardial infarction, acute left
ventricular failure with pulmonary edema, dissecting aortic aneurysm,
eclampsia, hypertensive encephalopathy, intracranial hemorrhage, and
unstable angina pectoris.
-The
mean arterial pressure should be reduced by approximately 25% within minutes
to two hours after treatment is initiated, and subsequently the
blood pressure should be reduced toward 160/100 mm Hg within 2 to 6
hours, and excessive falls in blood pressure should be avoided which may
precipitate cerebral, coronary, or renal ischemia.
-The
mean arterial pressure (MAP) is approximately one-third of the sum of twice
the diastolic pressure (DBP) plus the systolic pressure (SBP).
MAP= 0.33(2xDBP+SPB)
Treatment
of Hypertensive emergency:
-Nitroprusside
(Nipride) IV is first line treatment.
Consider placing an arterial line to obtain accurate blood
pressure monitoring. Monitor
for thiocyanate toxicity in patients with renal failure, renal
insuffiency, large doses of nitroprusside, and/or taking the medication
greater than 2-3 days. Consider
checking a thiocyanate level and/or cyanide level for patients at risk
for toxicity. Signs of
thiocyanate toxicity are seizures, tinnitus, visual blurring, changes in
mental status, abdominal pain, nausea, and hyperreflexia.
Patients with hepatic insuffiency or hepatic failure are at risk
for cyanide toxicity. The
antidote for thiocyanate toxicity due to nitroprusside is sodium
thiosulfate.
-Nitroglycerin
IV is the preferred treatment for patients with angina, myocardial
infarction, or congestive heart failure, especially in patients with
ischemic heart disease.
-Esmolol
and other IV Beta-blockers are second line for hypertensive emergencies.
Esmolol has a half-life of approximately 9 minutes which is the
shortest half-life of the IV Beta-blockers (atenolol, metoprolol,
labetalol, and propranolol).
Propranolol blocks both Beta1 and
Beta2
and
labetalol blocks alpha1, alpha2
, Beta1
, and Beta2
receptors
while esmolol, atenolol, and metoprolol are Beta1 selective.
-Phentolamine
is indicated to treat pheochromocytoma induced by blocking the alpha
receptors. Once the alpha
receptors have been blocked then propranolol can be added to block the
beta receptors. It is
important that the phentolamine is used FIRST to block the alpha
receptors prior to starting propranolol; otherwise, there could be
worsening of the hypertension due to unopposed beta blockade.
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