Systolic BP > 180 or diastolic BP > 120 mm Hg with evidence of active end organ damage is labelled ‘hypertensive emergency’, while the same elevation of BP without signs of endorgan damage is termed ‘hypertensive urgency’.
HYPERTENSIVE EMERGENCIES AND URGENCIES
Systolic BP > 180
or diastolic BP > 120 mm Hg with evidence of active end organ damage is
labelled ‘hypertensive emergency’,
while the same elevation of BP without signs of endorgan damage is termed ‘hypertensive urgency’.
Controlled reduction
of BP over minutes (in emergencies) or hours (in urgencies) is required to
counter threat to organ function and life in:
·
Cerebrovascular accident (haemorrhage) or head
injury with high BP.
·
Hypertensive encephalopathy.
·
Hypertensive acute LVF and pulmonary edema.
·
Unstable angina or MI with raised BP.
·
Dissecting aortic aneurysm.
·
Acute renal failure with raised BP.
·
Eclampsia.
·
Hypertensive episodes in pheochromocytoma,
cheese reaction or clonidine withdrawal.
Nifedipine
(10 mg soft geletine cap) orally every ½–1 hr was widely
employed for rapid BP reduction in urgencies. This practice has now been discarded
because of inability to control rate and degree of fall in BP as well as
serious adverse consequences/mortality. Other rapidly acting oral drugs like captopril (25 mg) or clonidine (100 μg) every 1–2 hours
have also been found unsatisfactory. Parenteral drugs with controllable action are
now used. Mean BP should be lowered by no more than 25% over minutes or a few
hours and then gradually to not lower than 160/100 mmHg. Drugs employed are:
1. Sodium Nitroprusside
Because of predictable, instantaneous, titratable and
balanced arteriovenous vasodilatory action which persists without tolerance
till infused, nitroprusside (20–300 μg/min) is the drug of choice for most
hypertensive emergencies. However, it needs an infusion pump and constant
monitoring, but is the most effective drug.
2. Glyceryl Trinitrate
Given by i.v. infusion (5–20 μg/min) GTN also acts
within 2–5 min and has brief titratable action. Its predominant venodilator
action makes it particularly suitable for lowering BP after cardiac surgery and
in acute LVF, MI, unstable angina. Tolerance starts developing after 18–24
hours of continuous infusion.
3. Diazoxide
Given as fractional i.v. bolus doses—BP once lowered
remains so for > 6 hours; constant monitoring is not required.
4. Hydralazine
10–20 mg i.m. or slow
i.v. injection; acts in
20–30 min and keeps BP low for 4–8 hours. It has been especially used in
eclampsia. It is to be avoided in patients with myocardial ischaemia or aortic
dissection.
5. Esmolol
This β blocker given as 0.5 mg/kg bolus
followed by slow i.v. injection (50–200 μg/kg/min) acts in 1–2
min; action lasts for 10–20 min. It is particularly useful when cardiac
contractility and work is to be reduced, such as in aortic dissection
(nitroprusside may be given concurrently) and during/after anaesthesia. The BP
lowering action is weaker. Excess bradycardia is to be guarded.
6. Phentolamine
This α1 + α2 blocker is the drug of choice
for hyperadrenergic states—hypertensive episodes in pheochromocytoma, cheese
reaction, clonidine withdrawal. Injected i.v. (5–10 mg) it acts in 2 min and
action lasts 5–15 min. Tachycardia and myocardial ischaemia may complicate its
use. A β blocker may be added.
7. Labetalol
Injected i.v., it is an alternative to α + β blockers for lowering
BP in pheochromocytoma, etc. but has only weak α blocking action. It
has been used to lower BP in MI, unstable angina, eclampsia also. Concomitant
CHF and asthma preclude its use.
8. Furosemide
(20–80 mg oral or i.v.) It may be given as an adjunct with any of the above drugs if
there is volume overload (acute LVF, pulmonary edema, CHF) or cerebral edema
(in encephalopathy), but should be avoided when patient may be hypovolemic due
to pressure induced natriuresis (especially in eclampsia, pheochromocytoma).
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