Sun21November0452PM 10

Magnesium sulphate is used extensively for prevention of eclamptic seizures during and immediately after pregnancy.

Which one of the following mechanisms of action of magnesium sulphate is most commonly attributed to the prevention eclampsia?

(Please select 1 option)

Increasing the convulsive threshold by NMDA receptor antagonism

Dilatation of cerebral circulation due to calcium channel antagonism reducing cerebral vascular spasm Correct

Dilatation of systemic circulation due to calcium channel antagonism reducing blood pressure

Reduction of cerebral oedema formation opposing movement of solutes across capillaries

Reduction of cerebral oedema formation opposing movement of water across capillaries by down-regulating aquaporin receptors

Explanation

Though the specific mechanisms of action remain unclear the effect of magnesium sulphate in the prevention of eclampsia is likely multi-factorial.

Magnesium sulphate acts as a vasodilator with actions on both the peripheral vasculature and the cerebral circulation to decrease peripheral vascular resistance and/or relieve vasoconstriction. The most likely mechanism is the effect of magnesium on the cerebral vasculature.

The theory of cerebrovascular vasospasm as the etiology of eclampsia seemed to be reinforced by transcranial Doppler (TCD) studies that suggested that MgSO4 treatment caused dilation in the cerebral circulation.

Additionally, magnesium sulphate may also protect the blood-brain barrier and limit cerebral oedema formation or it may act through a central anticonvulsant action.

Reference:

Euser AG, Cipolla MJ. Magnesium sulfate for the treatment of eclampsia: a brief review. Stroke. 2009;40:1169-75.

Answer Statistics

1

35%

2

47%

3

15%

4

2%

5

3%

Times answered: 244