Acid-Base and Point of Care Ultrasound in Severe Preeclampsia

Plain-language summary

Preeclampsia remains a leading cause of maternal morbidity and mortality, in both the developed and developing world. It is a complex, multisystem disease which, in its severe form, affects the cardiovascular, renal, hepatic, neurological and haematological systems. The University of Cape Town-associated medical institutions alone were responsible for the treatment of 800 women in 2014, who were classified as having preeclampsia with severe features. Given the complexity of the disease, anesthetic management for Caesarean section in these patients remains very challenging. Recent studies have begun to demonstrate novel markers of preeclampsia severity, including point-of-care ultrasound (POC-US) and acid-base (AB) abnormalities. For example, pilot studies have demonstrated that approximately 25% of women diagnosed with severe preeclampsia show signs of increased intracranial pressure and elevated lung water as evaluated by point of care ultrasound. These findings could serve as noninvasive markers of disease severity, and thus may be used to predict maternal and fetal outcome in preeclamptic women. Point of care ultrasound is playing an increasing role in perioperative diagnosis, and newer, less expensive devices are continuously being developed, and will in all likelihood play an important role in South Africa in the near future. In a recent trial performed at the University of Cape Town, a comprehensive acid-base analysis in severe preeclamptic women demonstrated significant abnormalities in independent acid-base determinants. In addition, strong indications were found that changes in acid-base status in preeclampsia are more pronounced earlier in pregnancy and are associated with urgent deliveries. As in other clinical arenas in critically ill patients, acid-base abnormalities are associated with increased lung water, increased intracranial pressure, and outcome, and we hypothesize that similar associations might be found in severe preeclamptic women. Therefore, one aim of this study is to evaluate the association of venous acid base abnormalities (an inexpensive and readily available test) observed in late onset severe preeclampsia and organ manifestations identified with ultrasound, a well-validated and robust tool for identifying these manifestations. Investigators will further examine the association between ultrasound findings and/or venous acid-base abnormalities with urgent delivery. It is intended to do a subsequent comparison between early- and late onset preeclampsia, when a suitable tertiary site has been identified.

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