Maternal and neonatal hyponatraemia: a comparison of Hartmanns solution with 5% dextrose for the delivery of oxytocin in labour

Oxytocin: physiology, pharmacology, and clinical application for labor management

Oxytocin is a peptide hormone that plays a key role in regulating the female reproductive system, including during labor and lactation. It is produced primarily in the hypothalamus and secreted by the posterior pituitary gland. Oxytocin can also be administered as a medication to initiate or augment uterine contractions. To study the effectiveness and safety of oxytocin, previous studies have randomized patients to low- and high-dose oxytocin infusion protocols either alone or as part of an active management of labor strategy along with other interventions. These randomized trials demonstrated that active management of labor and high-dose oxytocin regimens can shorten the length of labor and reduce the incidence of clinical chorioamnionitis. The safety of high-dose oxytocin regimens is also supported by no associated differences in fetal heart rate abnormalities, postpartum hemorrhage, low Apgar scores, neonatal intensive care unit admissions, and umbilical artery acidemia. Most studies reported no differences in the cesarean delivery rates with active management of labor or high-dose oxytocin regimens, thereby further validating its safety. Oxytocin does not have a predictable dose response, thus the pharmacologic effects and the amplitude and frequency of uterine contractions are used as physiological parameters for oxytocin infusion titration to achieve adequate contractions at appropriate intervals. Used in error, oxytocin can cause patient harm, highlighting the importance of precise administration using infusion pumps, institutional safety checklists, and trained nursing staff to closely monitor uterine activity and fetal heart rate changes. In this review, we summarize the physiology, pharmacology, infusion regimens, and associated risks of oxytocin.

A case series of severe symptomatic peripartum hyponatraemia

This single centre case series describes the presentation and management of six cases of peripartum hyponatraemia in women who were otherwise deemed low-risk at delivery. It highlights presenting symptoms such as fatigue, confusion and seizures as well as the effects on the neonate. It also focuses on areas of interest such as fluid intake, hormonal effects of ADH and oxytocin and the association with birthing pools for future research.

High- vs low-dose oxytocin in lean and obese women: a double-blinded randomized controlled trial

BACKGROUND

Women with obesity are likely to experience longer lengths of labor and are at an increased risk of cesarean delivery. We hypothesized that high-dose oxytocin would decrease the time to delivery in a cohort of women with obesity undergoing induction of labor.

OBJECTIVE

This study aimed to assess whether women with obesity benefited from higher doses of oxytocin for induction of labor.

STUDY DESIGN

A double-blinded randomized controlled trial was conducted to evaluate the effect of low-dose and high-dose oxytocin on length of labor. We recruited women who were undergoing induction of labor at ≥37 weeks of gestation. Patients were randomly assigned in a 1:1 ratio to receive low-dose or high-dose oxytocin stratified by obesity level (obese and lean). The primary outcome was length of time (minutes) to vaginal delivery. The secondary outcomes included overall cesarean delivery rate, cesarean delivery for labor arrest, maximum oxytocin infusion rate, oxytocin infusion discontinuation, oxytocin infusion decrease, blood loss, neonatal intensive care unit admission, and neonatal Apgar scores.

RESULTS

A total of 140 patients were randomized into receiving low-dose and high-dose oxytocin stratified into obese and lean stratum (35 for all strata). The primary outcome, time to vaginal delivery, was similar between the low-dose and high-dose oxytocin groups in the lean stratum (796 [±411] vs 694 [±466] minutes; P=.363) and the stratum with obesity (715 [±497] vs 762 [±594] minutes; P=.733). Kaplan-Meier curves between the low-dose and high-dose oxytocin groups were not significantly different in the lean stratum (P=.391) and the stratum with obesity (P=.692). There were 5 cesarean deliveries (14.29%) in the low-dose oxytocin lean stratum vs 2 cesarean deliveries (5.71%) in the high-dose oxytocin lean stratum (P=.232). There were 4 cesarean deliveries (11.43%) in the low-dose oxytocin stratum with obesity vs 1 cesarean delivery (2.86%) in the high-dose oxytocin stratum with obesity (P=.164). There was no difference in the incidence of postpartum hemorrhage between the lean stratum (P=0.526) and the stratum with obesity (P=0.212). There was no difference in mean estimated blood loss between the lean stratum (P=.472) and the stratum with obesity (P=.215).

CONCLUSION

There was no difference in time to delivery between the low-dose and high-dose oxytocin protocols in either the lean cohorts or cohorts with obesity undergoing induction of labor. We did observe a trend toward a lower rate of cesarean delivery in both lean women and women with obesity when high-dose oxytocin was used.

Intravenous fluids for reducing the duration of labour in low risk nulliparous women

BACKGROUND

Several factors may influence the progression of normal labour. It has been postulated that the routine administration of intravenous fluids to keep women adequately hydrated during labour may reduce the period of contraction and relaxation of the uterine muscle, and may ultimately reduce the duration of the labour. It has also been suggested that intravenous fluids may reduce caesarean sections (CS) for prolonged labour. However, the routine administration of intravenous fluids to labouring women has not been adequately elucidated although it is a widely-adopted policy, and there is no consensus on the type or volume of fluids that are required, or indeed, whether intravenous fluids are at all necessary. Women may be able to adequately hydrate themselves if they were allowed oral fluids during labour.Furthermore, excessive volumes of intravenous fluids may pose risks to both the mother and her newborn and different fluids are associated with different risks.

OBJECTIVES

To evaluate whether the routine administration of intravenous fluids to low-risk nulliparous labouring women reduces the duration of labour and to evaluate the safety of intravenous fluids on maternal and neonatal health.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (13 February 2013).

SELECTION CRITERIA

Randomised controlled trials of intravenous fluid administration to spontaneously labouring low-risk nulliparous women.

DATA COLLECTION AND ANALYSIS

The review authors independently assessed trials for inclusion, trial quality and extracted data.

MAIN RESULTS

We included nine randomised trials with 1781 women. Three trials had more than two treatment arms and were included in more than one comparison.Two trials compared women randomised to receive up to 250 mL/hour of Ringer's lactate solution as well as oral intake versus oral intake only. For women delivering vaginally, there was a reduction in the duration of labour in the Ringer's lactate group (mean difference (MD) -28.86 minutes, 95% confidence interval (CI) -47.41 to -10.30). There was no statistical reduction in the number of CS in the Ringer's lactate group (risk ratio (RR), 0.73 95% CI 0.49 to 1.08).Three trials compared women who received 125 mL/hour versus 250 mL/hour of intravenous fluids with free oral fluids in both groups. Women receiving a greater hourly volume of intravenous fluids (250 mL) had shorter labours than those receiving 125 mL (MD 23.87 minutes, 95% CI 3.72 to 44.02, 256 women). There was no statistically significant reduction in the number of CS in the 250 mL intravenous fluid group (average RR 1.00, 95% CI 0.54 to1.87, three studies, 334 women). In one study the number of assisted vaginal deliveries was lower in the group receiving 125 mL/hour (RR 0.47, 95% CI 0.27 to 0.81).Four trials compared rates of intravenous fluids in women where oral intake was restricted (125 mL/hour versus 250 mL/hour). There was a reduction in the duration of labour in women who received the higher infusion rate (MD 105.61 minutes, 95% CI 53.19 to 158.02); P < 0.0001, however, findings must be interpreted with caution as there was high heterogeneity amongst trials (I(2) = 53%). There was a significant reduction in CS in women receiving the higher rate of intravenous fluid infusion (RR 1.56, 95% CI 1.10 to 2.21; P = 0.01). There was no difference identified in the assisted delivery rate (RR 0.78, 95% CI 0.44 to 1.40). There was no clear difference between groups in the number of babies admitted to the NICU (RR 0.48, 95% CI 0.07 to 3.17).Two trials compared normal saline versus 5% dextrose. Only one reported the mean duration of labour, and there was no strong evidence of a difference between groups (MD -12.00, 95% CI -30.09 to 6.09). A trial reporting the median suggested that the duration was reduced in the dextrose group. There was no significant difference in CS or assisted deliveries (RR 0.77, 95% CI 0.41 to 1.43, two studies, 284 women) and (RR 0.59, 95% CI 0.21 to 1.63, one study, 93 women) respectively. Only one trial reported on maternal hyponatraemia (serum sodium levels < 135 mmol/L ). For neonatal complications, there was no difference in the admission to NICU) or in low Apgar scores, however 33.3% of babies developed hyponatraemia in the dextrose group compared to 13.3 % in the normal saline group (RR 0.40, 95% CI 0.17 to 0.93) (P = 0.03). One trial reported a higher incidence of neonatal hyperbilirubinaemia in the dextrose group of babies. There was no difference in neonatal hypoglycaemic episodes between groups.

AUTHORS' CONCLUSIONS

Although the administration of intravenous fluids compared with oral intake alone demonstrated a reduction in the duration of labour, this finding emerged from only two trials. The findings of other trials suggest that if a policy of no oral intake is applied, then the duration of labour in nulliparous women may be shortened by the administration of intravenous fluids at a rate of 250 mL/hour rather than 125 mL/hour. However, it may be possible for women to simply increase their oral intake rather than being attached to a drip and we have to consider whether it is justifiable to persist with a policy of 'nil by mouth'. One trial raised concerns about the safety of dextrose and this needs further exploration.None of the trials reported on the evaluation of maternal views of being attached to a drip during their entire labour. Furthermore, there was no objective assessment of dehydration. The evidence from this review does not provide robust evidence to recommend routine administration of intravenous fluids. Interpreting the results from trials was hampered by the low number of trials contributing data and by variation between trials. In trials where oral fluids were not restricted there was considerable variation in the amount of oral fluid consumed by women in different arms of the same trial, and between different trials. In addition, results from trials were not consistent and risk of bias varied. Some important research questions were addressed by single trials only, and important outcomes relating to maternal and infant morbidity were frequently not reported.

Variations in oxytocin regimes in Scottish labour wards in 1998

Oxytocin (Syntocinon, Sandoz Pharmaceuticals) is a commonly used drug in the modern management of labour. A recently published British survey found that 38% of low risk primigravid labours were augmented, most commonly by intravenous syntocinon. Unfortunately the misuse of syntocinon can lead to potentially serious problems for the fetus and mother. Despite the frequency of usage there appears to be no consensus as to the optimal dose and mode of administration. This paper explores the extent of this variation among Scottish obstetric units, the reasons for any variation in its use and makes some suggestions as to the way forward based on the current literature.

Current practice in oxytocin dilution and fluid administration for induction of labor

OBJECTIVE

To determine the types of intravenous fluids used to dilute oxytocin for labor induction in a national sample of obstetric units, as well as the extent to which these fluids reflect current published guidelines.

DESIGN

A descriptive design.

SETTING

Questionnaires were mailed to nurse managers at 700 obstetric units chosen via systematic random sampling from eligible hospitals listed in The AHA Guide (1998).

PARTICIPANTS

Two hundred fifty-six usable questionnaires were included in data analysis.

MAIN OUTCOME MEASURES

The Labor Induction Protocol Survey, consisting of eight questions relating to number of births per year, percentage of women whose labor is induced or augmented, methods used for induction of labor, intravenous fluids used to dilute oxytocin for induction of labor, the level of perinatal care of the unit, and the protocols units used to guide their practice in the use of oxytocin, was developed for this study.

RESULTS

Approximately 98% of the responding sites follow the current recommendations for oxytocin dilution and mainline fluid delivery. However, 5 or 2% of the sites reported the use of 5% dextrose in water for both oxytocin dilution and the mainline intravenous solution.

CONCLUSIONS

Although only 5 (2%) of the responding facilities indicated the use of 5% dextrose in water for both oxytocin dilution and the mainline intravenous solution, this may be clinically significant because of the serious nature of hyponatremia and the ease of its prevention. Nurses should be aware of the extent to which protocols for the infusion of oxytocin vary, despite what is documented as best practice and the potential consequences for their patients of implementing those protocols. Nurses who advocate for and participate in writing protocols that reflect the best-recommended practice for their patients will assist in ensuring that what is documented as best practice is actually implemented.

Drugs and uterine motility

Nurses who care for pregnant and laboring women are faced with an increasingly frequent use of pharmaceutical agents that facilitate initiation of labor (uterotropins), augment labor (uterotonics), or potentially stop labor (tocolytics). The choice of the drug, administration, side effects, and complications varies. Knowledge about uterine physiology helps the clinician understand the action of these agents. Knowledge of the differences and similarities among oxytoxics, ergots, prostaglandins, and the various drugs used as tocolytics is essential for safe and effective care of women and their fetuses who may be exposed to these agents.

Drug-induced syndrome of inappropriate antidiuretic hormone secretion. Causes, diagnosis and management

Hyponatraemia is common among the elderly, and may be caused by physiological changes, disease processes or drugs. About half of elderly patients with hyponatraemia have features typical of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is important to establish whether drugs are the cause, as this is easily remediable. The clinical manifestations of SIADH are predominantly attributable to hyponatraemia and serum hypo-osmolality. The severity of the signs and symptoms depends on the degree of hyponatraemia and the rapidity with which the syndrome develops. Although a growing number of drugs have been reported to produce SIADH, most published reports concern vasopressin and its analogues, thiazide and thiazide-like diuretics, chlorpropamide, carbamazepine, antipsychotics, antidepressants and nonsteroidal anti-inflammatory drugs. Old age is a risk factor for SIADH following the use of many of these drugs. The use of these drugs in combination, excessive fluid intake and other underlying conditions that limit free water excretion increase the risk. Drug-induced SIADH usually resolves following cessation of the offending agent(s). Additional measures are required in patients with symptomatic hyponatraemia, including fluid restriction and intravenous sodium chloride and/or furosemide (frusemide) therapy. Careful monitoring is essential, with particular attention paid to the rate and extent of correction of the hyponatraemia.