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Equilibrium of acidifying and alkalinizing metabolic acid-base disorders in severe preeclampsia
Abstract Number: T-27
Abstract Type: Original Research
Background: Acid-base (AB) disorders are associated with clinical outcome in critically ill patients. Conflicting results exist with regard to the metabolic AB status of severe preeclampsia, when the traditional concept of AB analysis is applied. The influence of common disturbances of water, electrolytes and albumin on AB status in preeclampsia has not been studied. The aim of this study was to clarify AB status in early and late onset severe preeclampsia by applying the physico-chemical approach (Stewart-Gilfix method) (1,2) in AB analysis, and therefore describing all independent parameters affecting womens’ AB status.
Methods: 49 women with severe preeclampsia (24 at <34 weeks gestation [early onset] and 25 at >34 weeks gestation [late onset]) (PE gp) were enrolled in this prospective case-control study. 20 healthy non-pregnant women (NPW gp), and 45 healthy pregnant women, (HPW gp) equally distributed from 26-40 weeks gestation. AB analysis was performed at the time of diagnosis of the disease, before induction of labor, or with the decision to perform emergency cesarean delivery. AB status was analyzed applying the Stewart-Gilfix method. Power analysis was based on expected strong ion difference (α 0.05 and β 0.95); AB parameters were compared using one-way ANOVA.
Results: When compared with the NPW gp, we found respiratory alkalosis with metabolic compensation in the HPW gp (PvCO2=36±5 mmHg), due to a decreased strong ion difference (SID) and increased strong ion gap (SIG), resulting in a net base excess (BE)=-3.5±1.9 mEq/L and vpH=7.39±0.03. There was no difference between the HPW and PE gps (BE=-3.9±2.6, vpH=7.41±0.03), however when analyzing factors determining BE, we find a hypoalbuminic alkalosis offset by hyperchloremic acidosis in preeclamptics, which explains a similar net BE. There was no difference in the accumulation of unmeasured anions (BE(UMA)), lactate (BE(Lac)) or free water (BE(Na)) between HPW and PE (Fig).
Conclusion: This is the 1st study demonstrating that while AB status in severe preeclampsia appears to be similar to that in healthy pregnant women, there is in fact a balance offsetting hypoalbuminic alkalosis and hyperchloremic acidosis. The clinical implications of these novel findings require further analysis to determine whether this measure can be used to monitor the severity of the disease.
1. Stewart PA, Can J Physiol Pharmacol 1983
2. Gilfix BM, J Crit Care 1993