Page 65 - Clinical Pearls in Cardiology

Arterial Pulse and Blood Pressure 53

Hypertensive emergencies demand immediate and
rigorous medical treatment in an intensive care unit
with continuous monitoring of blood pressure. Because
chronic hypertension is associated with autoregulatory
changes in heart, brain and kidneys, care should be taken
to avoid excessively rapid decrease in blood pressure,
which can lead to hypoperfusion and ischemic injury.
The initial goal of treatment in hypertensive emergencies
is to reduce the mean arterial pressure by no more than
20% within the first hour, and then towards a level of
around 120 mm Hg within the next few hours (Ref:
Schrier’s Diseases of the Kidney, 9th edn, Pg 1241).
Labetalol, glyceryl trinitrate, hydralazine and sodium
nitroprusside are all effective parenteral drugs used for
managing hypertensive emergencies.
37. What is malignant hypertension?
Malignant hypertension is characterized by sudden
marked elevation in blood pressure associated with
papilledema, retinal hemorrhages and/or exudates (i.e.
hypertensive neuroretinopathy). There is apparently no
absolute level of blood pressure above which malignant
hypertension occurs. But the diastolic blood pressure is
usually above 120 to 130 mm Hg. There may be intense
spasm of the cerebral arteries in malignant hypertension.
Cerebral vasoconstriction probably is an exaggerated
homeostatic response designed to protect the brain from
excesses of blood pressure and blood flow. But these
regulatory mechanisms are often insufficient to protect
the brain, and cerebral edema frequently develops.
This ultimately results in papilledema. Prolonged and
severe exposure to exaggerated levels of blood pressure
in malignant hypertension injures the walls of the
arterioles. This results in intravascular coagulation and