This hypertensive disorder of pregnancy is defined as a new onset of hypertension and proteinuria after 20 weeks of gestation. In Australia, we don't need proteinuria; we are happy to make the diagnosis with any sort of organ dysfunction. The definition of eclampsia is the presence of otherwise unexplainable seizures in a patient with preeclampsia.
This comes up fairly frequently in the SAQs. In broader terms, the pregnancy-related SAQs which are not about the jaundiced comatose woman are usually about the hypertensive seizure lady. These two variants between them seem to cover about 75% of the total spectrum of past paper questions. So, knowing these topics well sets you up to pass the majority of O&G material in the Part II exam. Here is a list of previous preeclampsia related questions:
Of these, several are not specifically about preeclampsia. Rather, it is the most sensible differential from a list of differentials which the candidates are expected to generate. For instance, Question 19 from the second paper of 2014 offers a scenario where a medically complex pregnant patient presents in such a manner as to bring up serotonin syndrome and PRES as sensible differentials, and preeclampsia is merely one of the possibilities.
There are certain features, identifiable at antenatal booking, which are associated with an increased risk of preeclampsia:
Risk factors for pre-eclampsia and eclampsia
Others have held forth extensively on the pathogenesis of this condition; suffice to say it is thought to be a systemic response to placental hypoperfusion, with increased activation of the potent vasoconstrictor endothelin-1, as well as an increased sensitivity to vasoconstrictors in general, and a down-regulation of vasodilatory mechanisms such as nitric oxide synthase.
In order to be labelled as a pregnant woman with preeclampsia, one must have a certain set f features:
Diagnostic criteria for preeclampsia:
Furthermore, there are several features which suggest that the condition is severe, and worth worrying about:
Features of severe preeclampsia:
A standard panel of tests should be requested:
Continuous ECG monitoring of the mother, and continuous foetal heart monitoring should commence.
Question 19 from the second paper of 2014 presented a scenario with numerous possible causes for fever and decreased level of consciousness; the question from the college was mainly about generating differentials and doing a diagnostic workup. The list of differentials was enormous, made more so by the following features of the presenting history:
With this, you could do just about any sort of differential diagnosis list. Here is a sample, adopted from the chapter on approaching the unconscious ICU patient.
Causes | Investigations |
Vascular causes:
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Infectious causes:
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Drug-related causes:
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Intrinsic neurological cause
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Autoimmune causes
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Traumatic or environmental causes
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Endocrine and metabolic causes:
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Differentials specific to pregnancy:
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So, perhaps it is not eclampsia but the consequences of normally well controlled epilepsy going haywire. Reasons an epileptic might have more seziures during pregnancy:
Weirdly, progensterone has an antiepileptic effect, and its levels are wildly elevated in pregnancy. In fact Vajda et al (2007) did a review of this issue and found that "the epileptic process seemed to become “better” no less often than it became “worse” during pregnancy".
Consequences to the foetus:
The key step is to get the baby out. Everything returns to normal after delivery. Except pulmonary oedema: this may actually be exacerbated.
While you are organising the delivery, there are various supportive measures which should be taken:
On one hand, one must prevent maternal stroke, intracranial haemorrhage and cerebral oedema. On the other hand, one must perfuse the placenta. The key is to keep the systolic under 160, and the diastolic under 110.
Labetalol, hydralazine and nifedipine are used as first line agents. There is no difference between them in terms of outcomes.
Methyldopa and sodium nitroprusside are second-line agents, if the hypertension is refractory.
Magnesium sulfate is the primary agent. Both Oh's manual and the RCOG statement quote the MAGPIE study, which convincingly demonstrated a reduction in maternal morbidity with magnesium. How it works, nobody knows. It has a half-life of 4 hours and is rapidly excreted (its pharmacokentics are dealt with elsewhere). One aims for a serum level of 2.0-3.5mmol/L.
Respiratory paralysis is difficult to accomplish; you need a level over 7.5mmol/L. As long as the deep tendon reflexes are present, you are unlikely to develop that sort of toxicity.
In general, there might be many possible aetiologies for the seizures, and one must consider a CT head to exclude major structural pathology.
Oh's Intensive Care manual: Chapter 63 (pp. 677) Preeclampsia and eclampsia by Wai Ka Ming and Tony Gin
RCOG Guidelines for the management of severe pre-eclampsia/eclampsia (2006)
Duckitt, Kirsten, and Deborah Harrington. "Risk factors for pre-eclampsia at antenatal booking: systematic review of controlled studies." Bmj 330.7491 (2005): 565.
Lorquet, Sophie, et al. "Aetiology and physiopathology of preeclampsia and related forms." Acta Clinica Belgica 65.4 (2010): 237-241.
Young, Brett C., Richard J. Levine, and S. Ananth Karumanchi. "Pathogenesis of preeclampsia." Annual Review of Pathological Mechanical Disease 5 (2010): 173-192.
Altman, D., et al. "Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial."Lancet 359.9321 (2002): 1877-1890.
Beach, Robert L., and Peter W. Kaplan. "Seizures in pregnancy: diagnosis and management." International review of neurobiology 83 (2008): 259-271.
Walker, S. P., M. Permezel, and S. F. Berkovic. "The management of epilepsy in pregnancy." BJOG: An International Journal of Obstetrics & Gynaecology116.6 (2009): 758-767.
Chen, Yi-Hua, et al. "Affect of seizures during gestation on pregnancy outcomes in women with epilepsy." Archives of neurology 66.8 (2009): 979-984.
Otani, Koichi. "Risk factors for the increased seizure frequency during pregnancy and puerperium." Psychiatry and Clinical Neurosciences 39.1 (1985): 33-42.
Teramo, K., et al. "Fetal heart rate during a maternal grand mal epileptic seizure." Journal of Perinatal Medicine-Official Journal of the WAPM 7.1 (1979): 3-6.
LaJoie, Josiane, and Solomon L. Moshé. "Effects of seizures and their treatment on fetal brain." Epilepsia 45.s8 (2004): 48-52.
Klein, Pave, and Andrew G. Herzog. "Hormonal effects on epilepsy in women."Epilepsia 39.s8 (1998): S9-S16.
Vajda, Frank JE, et al. "Seizure control in antiepileptic drug‐treated pregnancy." Epilepsia 49.1 (2008): 172-176.