Book of Medical Disorders in Pregnancy - Tintash

to procrastinate all available methods of
rapid digitalization. Liberal use of pethidine,
oxygen and suction is needed for
such patients and should be administered
judicially. Foley's catheter should
be introduced and fluid and electrolyte
balance maintained.
Fetal well being assessment should be
employed. The time of in-duction will
depend upon fetal mat-urity and state of
cervix. One may be inclined to induce a
labour earlier if the cervix is favorable.
In cases with unfavorable cervices the
dangers of caesarean section should be
weighed against continuation of the
pregnancy.
Thiazide diuretics - These drugs are
potent diuretics. The antihypertensive
action of these drugs has been ascribed
to an initial reduction in extracellular
and plasma volume and total exchangeable
sodium with a concomitant reduction
in cardiac output. The limited
hypotensive effect achieved, however,
may be blocked subsequently by either
salt administration or plasma volume
expansion. In pregnancy the use of
diuretics carries an increased risk of
sodium and potassium depletion. Its use
is associated with elevated plasma renin
levels and reduced placental clearance of
dehydro epiandrosterone sulfate. Common
maternal side effects are hyper uremia,
hypokalemia, alteration in glucose
metabolism and acute pancreatitis. Fetal
side effects reported are hyponatremia
and thrombocytopenia.
Hypotensive agents:
methyldopa (Aldomet) - Methyldopa
interferes with chemical neural transmission
at the post ganglionic nerve
endings and results in reduced peripheral
arteriolar resistance. This is accom-
57
plished by the drug acting as a competitive
inhibitor in the synthesis of
catecholamines its conversion to alpha
methyl norepinephrine and subsequent
displacement of norepinephrine stores at
the adrenergic post ganglionic nerve
endings and alteration of the norepinephrine
binding sites. Its release in
place of norepinephrine acts as a false
transmitter, thereby impairing the
intended pressor effects. The end result
is a lowering of the diastolic and systolic
pressure in both the standing and supine
positions. Regional blood flow to the
kidneys and uterus appear to be
maintained in the presence of the
hypotensive action despite the fact that a
reduction in cardiac output has been
reported. Methyldopa has been observed
to reduce plasma renin levels. The major
side effects are sedation, sodium
retention, depression and a reported 20%
positive direct Comb’s test. Methyldopa
is a good choice for long-term
antihypertensive therapy in pregnancy.
Hydralazine (Apresoline) - This drug
reduces arteriolar resistance. Hydralazine
may also elicit a central effect at
the vasomotor centre resulting in reduced
sympathetic tone. The predominant
effect of the drug is on the
arterioles rather than veins. This results
in a greater diastolic than systolic reduction
in arterial pressure and produces
minimal postural hypotension.
In addition to its hypotensive effect,
hydralazine also has a positive inotropic
and chronotropic effect upon the heart,
which results in an increased heart rate
and stroke volume. Hydralazine produces
increase in cardiac out-put and
blood flow to the cerebral, coronary, splanchnic,
renal and uterine circulations.
The direct vascular effect of hydralazine,