Severe asymptomatic maternal antepartum hyponatremia leading to neonatal seizures: prevention is better than cure

Severe hyponatraemia peripartum associated with omeprazole therapy

Hyponatraemia is the most commonly encountered electrolyte abnormality in pregnancy and may be associated with adverse maternal and neonatal outcomes. Rapid onset, severe hyponatraemia has been reported with proton-pump inhibitor therapy in non-pregnant individuals. Gastro-oesophageal reflux is very common during pregnancy, and proton-pump inhibitors are available without a prescription in many countries. A case of severe maternal hyponatraemia in the setting of recent omeprazole therapy is presented. Health professionals should be aware of this complication given the availability of proton-pump inhibitors without prescription and high rates of gestational gastro-oesophageal reflux.

Overconsumption of fluids during labour leading to water intoxication and a tonic-clonic seizure in a healthy labourer

A 33-year-old woman in her first pregnancy with no significant medical history had a tonic-clonic seizure one hour after delivery due to acute hyponatraemia caused by excess intake of fluids. She was admitted to a birthing centre as a low-risk labourer where she spent 19 hours including 4 hours in the second stage of labour. Throughout the labour, she was encouraged to drink as per her own initiative and thirst. However, there was no monitoring of fluid intake. In spite of initial confusion about the cause of the seizure, a multidisciplinary approach helped with diagnosis of an underlying pathology and allowed timely treatment to avoid adverse outcomes in this patient. We would like to increase awareness of a possibility, however rare, of water intoxication due to fluid overconsumption by patients in labour and encourage production of information guidance for monitoring of fluid intake of women in labour.

Preeclampsia and low sodium: A retrospective cohort analysis and literature review

BACKGROUND

The aim of this study was to retrospectively analyze the prevalence of severe preeclampsia and low sodium (PALS) among the pregnant population admitted at the University Hospital of Udine in the past 4 years and to compare these data with the current literature.

METHODS

Only women with a diagnosis of preeclampsia were included. According to the lowest sodium level measured either 5 days before or 5 days after delivery, patients were divided in two groups: women with hyponatremia (<135 mmol/L; severe <120 mmol/L) and women with normonatremia (>135 mmol/L). Moreover, a search literature was performed.

RESULTS

Of 59 patients with preeclampsia, 20 (34%) had hyponatremia. Only one case (1.6%) of severe maternal hyponatremia (sodium level 117 mmol/L) in the setting of preeclampsia was identified. After literature search, a total of 22 manuscripts including 60 case reports of PALS were identified. The lowest sodium level was 113 mmol/L, at 25 weeks of gestation. In most cases hyponatremia was treated with fluid restriction. In only 5 cases hyponatremia was treated with a saline hypertonic solution. Hyponatremia resolution, when reported, occurred in about 48 h. Sodium level in neonates ranged from 118 and 128 mmol/L.

CONCLUSIONS

PALS may occur in about a third of women with severe preeclampsia. Severe maternal hyponatremia should be treated with fluid restriction and with hypertonic saline solution. Moreover neonatologists should be alerted in order to treat the neonate for the best outcome.

Hyponatraemia reversibly affects human myometrial contractility. An in vitro pilot study

Background

In a previous study we found a significant correlation between dystocia and hyponatraemia that developed during labour. The present study examined a possible causal relationship. In vitro studies often use area under the curve (AUC) determined by frequency and force of contractions as a measure of myometrial contractility. However, a phase portrait plot of isometric contraction, obtained by plotting the first derivate of contraction against force of contraction, could indicate that bi-or multiphasic contractions might be less effective compared to the smooth contractions.

Material and methods

Myometrial biopsies were obtained from 17 women undergoing elective caesarean section at term. Each biopsy was divided into 8 strips and mounted isometrically in a force transducer. Seven biopsies were used in the first part of the study when half of the strips were immersed in the hyponatraemic study solution S containing Na⁺ 120 mmol/L and observed for 1 hour, followed by 1 hour in normonatraemic control solution C containing Na⁺ 136 mmol/L, then again in S for 1 hour, and finally 1 hour in C. The other half of the strips were studied in reverse order, C-S-C-S. The remaining ten biopsies were included in the second part of the study. Response to increasing doses of oxytocin (OT) in solutions S and C was studied. In the first part of the study we calculated AUC, and created phase portrait plots of two different contractions from the same strip, one smooth and one biphasic. In both parts of the study we registered frequency and force of contractions, and described appearance of the contractions.

Results

First part of the study: Mean (median) contractions per hour in C: 8.7 (7.6), in S 14,3 (13). Mean (SD) difference between groups 5.6 (4.2), p = 0.018. Force of contractions in C: 11.8 (10.2) mN, in S: 10.8 (9.2) mN, p = 0.09, AUC increased in S; p = 0.018. Bi-/multiphasic contractions increased from 8% in C to 18% in S, p = 0.001. All changes were reversible in C. Second part of the study: Frequency after OT 1.65 x 10−⁹ M in C:3.4 (2.9), in S: 3.8 (3.2), difference between groups: p = 0.48. After OT 1.65 x 10−⁷ M in C: 7.8 (8.9), increase from previous OT administration: p = 0.09, in S: 8.7 (9.0), p = 0.04, difference between groups, p = 0.32. Only at the highest dose of OT dose was there an increase in force of contraction in S, p = 0.05, difference between groups, p = 0.33. Initial response to OT was more frequently bi/multiphasic in S, reaching significance at the highest dose of OT(1.65 x 10−⁷ M), p = 0.015. when almost all contractions were bi/multiphasic.

Conclusion

Hyponatraemia reversibly increased frequency of contractions and appearance of bi-or multiphasic contractions, that could reduce myometrial contractility. This could explain the correlation of hyponatraemia and instrumental delivery previously observed. Contractions in the hyponatraemic solution more frequently showed initial multiphasic contractions when OT was added in increasing doses. Longer lasting labours carry the risk both of hyponatraemia and OT administration, and their negative interaction could be significant. Further studies should address this possibility.

Feto-maternal osmotic balance at term. A prospective observational study

OBJECTIVE

We performed the present study to investigate the feto-maternal osmotic relationship at term with the hypothesis that, in contrast to the literature, maternal plasma osmolality is lower than fetal levels. In a previous study, we found that maternal plasma sodium at delivery was consistently lower than the sodium in the umbilical artery. Our aim was to corroborate these results with analysis of osmolality.

METHODS

Blood was sampled from 30 women immediately before cesarean section and from the umbilical artery and vein before cord clamping and osmolality, sodium and albumin were analyzed.

RESULTS

Maternal osmolality was (mean; 95% confidence interval) 287.0 (285.8-288.2) mOsmkg/kg, arterial cord osmolality was 289.4 (287.9-291.0) mOsm/kg and venous cord osmolality was 287.3 (286.0-288.5) mOsm/kg. The paired difference between maternal and umbilical arterial osmolality was mean (SD) -2.4 (3.3) mOsm/kg (P<0.001), between maternal and umbilical vein -0.3 (3.0) mOsm/kg (P=0.63) and between umbilical artery and vein -2.1 (2.8) mOsm/kg (P<0.001).

CONCLUSION

Maternal osmolality was significantly lower than arterial cord osmolality confirming our previous results. The feto-maternal osmotic gradient favors water transport from the mother to the fetus and may increase the fetal risk of water intoxication when the mother ingests or is administered large volumes of electrolyte free solutions.