The principles of treatment are:
1. Assessment of the extent of maternal organ system involvement,
2. Assessment of the fetus,
3. Correction of the underlying patho-physiologic changes.
1. The first aim is rapidly achieved by
(a) checking the blood pressure (an appropriate sized cuff and a sphygmomanometer remain the gold standard for this),
(b) examining for hyperreflexia and clonus (signs of central nervous system involvement), epigastric tenderness (subcapsular liver swelling due to ischaemia) and pulmonary oedema, and
(c) measuring the haemoglobin and haematocrit (a haematocrit above 0.40 is probably abnormal; certainly > 0.45 reflects plasma volume contraction) (1), platelet count and coagulation studies (the latter are rarely abnormal when the platelet count is normal) (2), liver enzymes, plasma creatinine concentration (greater than 90 micromol/L is abnormal for pregnancy).
2. The fetus can be assessed rapidly by examining fundal height, fetal heart rate and CTG. Check whether steroids have been given in cases of severe prematurity as these will have aided fetal lung maturity.
3. Hypertension is generally treated when BP is persistently above 160 mmHg systolic and/or 90 mmHg diastolic. Chronic treatment centres around medications such as oxprenolol, methyldopa, labetalol, clonidine, prazosin, hydralazine and nifedipine (3). In the acute setting, BP should be lowered if systolic BP >170 mmHg and/or diastolic > 110 mmHg, using sublingual nifedipine 10 mg or intravenous hydralazine 5 mg boluses. If hypertension is refractory to 3 such doses at 20 minute intervals then a hydralazine infusion (5mg/hr) is often successful. If this fails sodium nitroprusside should be used and delivery effected quickly.
Convulsion prophylaxis is required when there is evidence of central nervous system involvement, ie. following a convulsion or else prophylactically when there is hyperreflexia with clonus, severe headaches with hyperreflexia or repeated visual scotomata. Magnesium sulphate (there are many regimens but a 4gm intravenous loading dose followed by 1.5gm/hr until 48 hours post delivery is one useful method) is now thought to be superior to phenytoin for convulsion prophylaxis (4, 5).
Thrombocytopenia is generally treated (with 6 to 8 units of platelets) if the platelet count is below 40,000 as the accompanying severe hypertension makes intracerebral haemorrhage a very real risk. Coagulation abnormalities are uncommon but should be corrected with fresh frozen plasma.
Volume expansion remains a controversial area of management. In severe pre-eclampsia, the plasma volume is likely to be contracted. Particularly when vasodilators have been given or an epidural anaesthetic is about to be administered, preloading with 500 ml (approximately the plasma volume deficit in most cases) of a colloid containing solution (125 ml/hr) is a safe technique which helps prevent sudden hypotension and is very unlikely to induce pulmonary oedema. Oliguria is very worrying and should be treated initially with careful volume restoration (up to 1000 ml of a colloid solution is adequate). If there is no response to volume restoration, a diuretic (20 mg frusemide intravenously is often enough) can be administered after collecting blood and urine to check the fractional sodium excretion. Invasive haemodynamic monitoring is unnecessary in most cases and should be reserved for the pre-eclamptic woman with continuing oliguria or pulmonary oedema (3).
In general, it must be remembered that the best treatment of severe pre-eclampsia is delivery of the placenta. This should be effected quickly but the best outcomes are obtained when the pre-eclamptic woman has been adequately prepared for delivery, as outlined above.
References:
1. Brown MA, Zammit VC, Mitar DM. Extracellular fluid volumes in pregnancy-induced hypertension. J. Hypertension. 1992; 10: 61-68.
2. Barker P, Callandar CC. Coagulation screening before epidural analgesia in pre-eclampsia. Anaesthesia. 1991; 46: 64-67.
3. Australasian Society for the Study of Hypertension in Pregnancy. Management of hypertension in pregnancy: Consensus summary. Med J Aust. 1993; 158: 700-702.
4. Eclampsia Trial Collaborative Group. Which anticonvulsant for women with eclampsia? Evidence from the collaborative eclampsia trial. Lancet. 1995; 345:1455-1462.
5. Lucas M, Leveno K, Cunningham G. A comparison of magnesium sulfate with phenytoin for the prevention of eclampsia. New Engl J Med. 1995; 333: 201-205.