Effect of prenatal steroids on potassium balance in extremely low birth weight neonates

Fluid and electrolyte management in the neonate and what can go wrong

PURPOSE OF REVIEW

This review highlights recent advances in understanding fluid and electrolyte homeostasis during the newborn period, including heightened recognition of fluid overload and acute kidney injury contributing to poor clinical outcomes. Particular attention is given towards the care of extremely preterm infants.

RECENT FINDINGS

Emerging data demonstrate (i) disproportionally large transepidermal water loss in the extremely preterm population, (ii) the relationship between postnatal weight loss (negative fluid balance) and improved outcomes, (iii) the frequency and negative effects of dysnatremias early in life, (iv) the role of sodium homeostasis in optimizing postnatal growth, and (v) the deleterious effects of fluid overload and acute kidney injury.

SUMMARY

As clinicians care for an increasing number of preterm infants, understanding progress in approaches to fluid and electrolyte management and avoidance of fluid overload states will improve the care and outcomes of this vulnerable population. Further translational and clinical studies are needed to address remaining knowledge gaps and improve current approaches to fluid and electrolyte management.

A physiological approach to fluid and electrolyte management of the preterm infant: Review

Despite the fact that hundreds of thousands of preterm infants receive parenteral fluids each year, study of optimal fluid and electrolyte management in this population is limited. Compared to older children and adults, preterm infants have an impaired capacity to regulate water and electrolyte balance. Appropriate fluid and electrolyte management is critical for optimal care of low birth weight or sick infants, as fluid overload and electrolyte abnormalities pose significant morbidity. This review highlights basic physiological principles which need to be applied when prescribing parenteral fluids and builds upon published literature to outline a rational approach to initial fluid and electrolyte management of the preterm infant.

Characteristics of nonoliguric hyperkalemia in preterm infants: A case-control study in a single center

BACKGROUND

Preterm infants often present with hyperkalemia during the first days after birth without showing oliguria. This is known as nonoliguric hyperkalemia (NOHK). As its clinical features have not been completely understood to date, we aimed to elucidate the characteristics of NOHK, including its risk factors, in preterm infants.

METHODS

For this case-control study, we reviewed the files of all infants born before 32 weeks of gestational age in our neonatal intensive care unit between 2011 and 2018. We distinguished the NOHK and non-NOHK groups and compared their characteristics and blood potassium levels. Nonoliguric hyperkalemia was defined as peak blood potassium concentration of ≥6.0 mmol/L during the first 72 h of life with a urine output of ≥1 mL/kg/h.

RESULTS

Of the 99 infants enrolled, 21 (21%) demonstrated NOHK. Infants with NOHK were more likely to have been exposed to antenatal magnesium sulfate (MgSO₄ ) (P = 0.019) than those in the non-NOHK group. Acute morbidities and mortality were not statistically different. Multivariate analysis indicated that administration of maternal MgSO₄ for longer than 24 h at any point before delivery was a risk factor for NOHK. Its adjusted odds ratio and 95% confidence interval were 4.0 and 1.4-12.3, respectively (P = 0.012).

CONCLUSIONS

In this study, maternal MgSO₄ administration for longer than 24 h proved to be a risk factor for NOHK in infants born before 32 weeks of gestational age. Infants born to mothers who have received MgSO₄ should be regularly monitored for their electrolytes.

Potassium disorders in pediatric emergency department: Clinical spectrum and management

INTRODUCTION

Potassium abnormalities are frequent in intensive care but their incidence in the emergency department is unknown.

AIM

We describe the spectrum of potassium abnormalities in our tertiary-level pediatric emergency department.

METHODS

Retrospective case-control study of all the patients admitted to a single-center tertiary emergency department over a 2.5-year period. We compared patients with hypokalemia (<3.0mEq/L) and patients with hyperkalemia (>6.0mEq/L) against a normal randomized population recruited on a 3:1 ratio with potassium levels between 3.5 and 5mEq/L.

RESULTS

Between January 1, 2013 and August 31, 2016 we admitted 108,209 patients to our emergency department. A total of 9342 blood samples were tested and the following potassium measurements were found: 60 cases of hypokalemia (2.8±0.2mEq/L) and 55 cases of hyperkalemia (6.4±0.6mEq/L). In total, 200 patients with normokalemia were recruited (4.1±0.3mEq/L). The main causes of the disorders were non-specific: lower respiratory tract infection (23%) and fracture (15%) for hypokalemia, lower respiratory tract (21.8%) and ear-nose-throat infections (20.0%) for hyperkalemia. Patients with hyperkalemia had an elevated creatinine level (0.72±1.6 vs. 0.40±0.16mg/dL, P<0.0001) with lower bicarbonate (19.4±3.8 vs. 21.8±2.8mmol/L, P=0.0001) and higher phosphorus levels (1.95±0.6 vs. 1.42±0.27mg/dL, P=0.0001). Patients with hypokalemia had an elevated creatinine level (0.66±0.71 vs. 0.40±0.16mg/dL, P<0.0001) and a lower phosphorus level (1.12±0.31 vs. 1.42±0.27mg/dL, P=0.0001). We did not observe significant differences in pH, PCO₂, base excess and lactate, or in the mean duration of hospitalization in general wards and pediatric intensive care units according to the PIM and PRISM scores.

DISCUSSION

Dyskalemia is rare in emergency department patients: 0.64% for hypokalemia and 0.58% for hyperkalemia. This condition could be explained by a degree of renal failure due to transient volume disturbance. The main mechanism is dehydration due to digestive losses, polypnea in young patients, and poor intake. In the case of hypokalemia, poor intake and digestive losses could be the main explanation. These disorders resolve easily with feeding or perfusion and do not impair development.

CONCLUSION

Dyskalemia is rare in emergency department patients and is easily resolved with feeding or perfusion. A plausible etiological mechanism is a transient volume disturbance. Dyskalemia is not predictive of poor development in the emergency pediatric population.

Early-onset neonatal hyperkalemia associated with maternal hypermagnesemia: a case report

BACKGROUND

Neonatal nonoliguric hyperkalemia (NOHK) is a metabolic abnormality that occurs in extremely premature neonates at approximately 24 h after birth and is mainly due to the immature functioning of the sodium (Na⁺)/potassium (K⁺) pump. Magnesium sulfate is frequently used in obstetrical practice to prevent preterm labor and to treat preeclampsia; this medication can also cause hypermagnesemia and hyperkalemia by a mechanism that is different from that of NOHK. Herein, we report the first case of very early-onset neonatal hyperkalemia induced by maternal hypermagnesemia.

CASE PRESENTATION

A neonate born at 32 weeks of gestation developed hyperkalemia (K⁺ 6.4 mmol/L) 2 h after birth. The neonate's blood potassium concentration reached 7.0 mmol/L 4 h after birth, despite good urine output. The neonate and his mother had severe hypermagnesemia caused by intravenous infusion of magnesium sulfate given for tocolysis due to pre-term labor.

CONCLUSION

The early-onset hyperkalemia may have been caused by the accumulation of potassium ions transported through the placenta, the shift of potassium ions from the intracellular to the extracellular space in the infant due to the malfunctioning of the Na⁺/K⁺ pump and the inhibition of renal distal tube potassium ion secretion, there is a possibility that these mechanisms were induced by maternal and fetal hypermagnesemia after maternal magnesium sulfate administration. Because neonatal hyperkalemia poses a significant risk for the development of life-threatening cardiac arrhythmia, this case highlights the necessity of maternal blood magnesium monitoring during magnesium sulfate administration and neonatal blood potassium monitoring when there is severe maternal hypermagnesemia at delivery.

Potassium regulation in the neonate

Potassium, the major cation in intracelluar fluids, is essential for vital biological functions. Neonates maintain a net positive potassium balance, which is fundamental to ensure somatic growth but places these infants, especially those born prematurely, at risk for life-threatening disturbances in potassium concentration [K⁺] in the extracellular fluid compartment. Potassium conservation is achieved by maximizing gastrointestinal absorption and minimizing renal losses. A markedly low glomerular filtration rate, plus adaptations in tubular transport along the nephron, result in low potassium excretion in the urine of neonates. Careful evaluation of clinical data using reference values that are normal for the neonate's postmenstrual age is critical to avoid over-treating infants with laboratory results that represent physiologic values for their developmental stage. The treatment should be aimed at correcting the primary cause when possible. Alterations in the levels or sensitivity to aldosterone are common in neonates. In symptomatic patients, the disturbances in [K⁺] should be corrected promptly, with close electrocardiographic monitoring. Plasma [K⁺] should be monitored during the first 72 h of life in all premature infants born before 30 weeks of postmenstrual age as these infants are prone to develop non-oliguric hyperkalemia with potential serious complications.

Renal adaptive changes and sodium handling in the fetal-to-newborn transition

Appropriate fluid and electrolyte management is critical for optimal care of very low birth weight or sick infants. Delivery of such care requires an understanding of developmental changes in renal water and salt handling that occur with advancing gestational age as well as postnatal age. This review focuses on the principles of sodium homeostasis during fetal and postnatal life. The physiology of renal tubular transport mechanisms, as well as neurohumoral factors impacting renal tubular transport are highlighted. Clinical implications and guidelines to the provision of sodium to this vulnerable population are also discussed.

Extremely preterm infants who are small for gestational age have a high risk of early hypophosphatemia and hypokalemia

AIM

Electrolyte balances have not been sufficiently evaluated in extremely preterm infants after early parenteral nutrition. We investigated the risk of early hypophosphatemia and hypokalemia in extremely preterm infants born small for gestational age (SGA) who received nutrition as currently recommended.

METHODS

This prospective, observational cohort study included all consecutive extremely preterm infants born at 24-27 weeks who received high amino acids and lipid perfusion from birth. We evaluated the electrolyte levels of SGA infants and infants born appropriate for gestational age (AGA) during the first five days of life.

RESULTS

The 12 SGA infants had lower plasma potassium levels from Day One compared to the 36 AGA infants and were more likely to have hypokalemia (58% vs 17%, p = 0.001) and hypophosphatemia (40% vs 9%, p < 0.01) during the five-day observation period. After adjusting for perinatal factors, SGA remained significantly associated with hypophosphatemia (odds ratio 1.39, confidence intervals 1.07-1.81, p = 0.01).

CONCLUSION

Extremely preterm infants born SGA who were managed with currently recommended early parenteral nutrition had a high risk of early hypokalemia and hypophosphatemia. Potassium and phosphorus intakes should be set at sufficient levels from birth onwards, especially in SGA infants.

Doxapram and hypokalaemia in very preterm infants

BACKGROUND

We observed two preterm infants who developed severe hypokalaemia following doxapram. We therefore wished to review the possible association between doxapram and severe hypokalaemia.

STUDY DESIGN

A retrospective study of preterm infants born before 32 weeks of gestation and hospitalised in our intensive care unit in 2004. For each infant, treatment with doxapram or with any drug known to interfere with potassium metabolism, potassium intakes and episodes of hypokalaemia have been recorded.

RESULTS

Out of 105 infants, 54 received doxapram. Doxapram-treated infants were significantly younger and had a lower birth weight. Doxapram treated infants were more likely to receive caffeine, furosemide, insulin and mechanical ventilation. There was no difference between the two groups for the other parameters. Hypokalaemia was frequently encountered in our population since it occurred in 76% of enrolled patients and severe hypokalaemia (potassium plasma level below 3 mmol/l) was found in 41%. Bivariate analysis underlined several risk factors for severe hypokalaemia: use of doxapram, gestational age below 28 weeks, use of mechanical ventilation, furosemide, ibuprofen, insulin and postnatal corticosteroids. Cox model's multivariate analysis showed that administration of furosemide and doxapram significantly increased the occurrence of severe hypokalaemia with relative risks of 4.9 (95% CI 1.9 to 12.5) and 8.2 (95% CI 3.1 to 21.7), respectively.

CONCLUSIONS

This retrospective study underlines the high incidence of severe hypokalaemia in very preterm infants and an increased risk of severe hypokalaemia during doxapram treatment. We recommend potassium monitoring during any use of doxapram.

Non-oliguric hyperkalemia in extremely low birth weight infants

PURPOSE

It is to examine clinical manifestations, early biochemical indicators, and risk factors for non-oliguric hyperkalemia (NOHK) in extremely low birth weight infants (ELBWI).

MATERIALS AND METHODS

We collected clinical and biochemical data from 75 ELBWI admitted to Ajou University Hospital between Jan. 2008 and Jun. 2011 by reviewing medical records retrospectively. NOHK was defined as serum potassium≥7 mmol/L during the first 72 hours of life with urine output≥1 mL/kg/h.

RESULTS

NOHK developed in 26.7% (20/75) of ELBWI. Among NOHK developed in ELBWI, 85% (17/20) developed within postnatal (PN) 48 hours, 5% (1/20) experienced cardiac arrhythmia and 20% (4/20) of NOHK infants expired within PN 72 hours. There were statistically significant differences in gestational age, use of antenatal steroid, and serum phosphorous level at PN 24 hours, and serum sodium, calcium, and urea levels at PN 72 hours between NOHK and non-NOHK groups (p-value<0.050). However, there were no statistical differences in the rate of intraventricular hemorrhage, arrhythmia, mortality occurred, methods of fluid therapy, supplementation of amino acid and calcium, frequencies of umbilical artery catheterization and urine output between the two groups.

CONCLUSION

NOHK is not a rare complication in ELBWI. It occurs more frequently in ELBWI with younger gestational age and who didn't use antenatal steroid. Furthermore, electrolyte imbalance such as hypernatremia, hypocalcemia and hyperphosphatemia occurred more often in NOHK group within PN 72 hours. Therefore, more use of antenatal steroid and careful control by monitoring electrolyte imbalance should be considered in order to prevent NOHK in ELBWI.

High-dose calcium reduces early-onset hyperkalemia in extremely preterm neonates

BACKGROUND

Early-onset hyperkalemia often occurs in extremely preterm infants during a few days after birth. While there are several treatments for hyperkalemia, calcium infusion to reduce plasma potassium concentrations remains controversial. The purpose of this study is to investigate whether a high dosage of calcium reduces early-onset hyperkalemia.

METHODS

Extremely low-birthweight neonates born at 22-25 weeks' gestation were enrolled. We analyzed data using multivariate regression analysis and performed a retrospective cohort study with patients divided into two groups according to the dosage of calcium in their initial infusion.

RESULTS

A total of 103 patients were eligible. Early-onset hyperkalemia was observed in 27 patients. The dosage of calcium gluconate during 24 h after birth was the only independent factor affecting early-onset hyperkalemia. The maximum plasma potassium concentration during 72 h after birth was negatively correlated with the dosage of calcium. High-dose calcium reduced occurrences of hyperkalemia and hypoglycemia caused by insulin infusion given for treatment of hyperkalemia, without increasing the risk of any other complications.

CONCLUSIONS

Infusion of calcium gluconate may reduce early-onset hyperkalemia in a dose-dependent manner.

Interventions for non-oliguric hyperkalaemia in preterm neonates

BACKGROUND

Non-oliguric hyperkalaemia of the newborn is defined as a plasma potassium level > 6.5 mmol/L in the absence of acute renal failure. Hyperkalaemia is a common complication in the first 48 hours of life in very low birth weight (VLBW) (birth weight < 1500 g) and/or very preterm newborns (≤32 weeks gestational age).

OBJECTIVES

To determine the effectiveness and safety of interventions for non-oliguric hyperkalaemia [for the purpose of this review defined as serum potassium > 6.0 mmol/L (the clinical setting in which interventions would likely be introduced prior to reaching a grossly abnormal level) and urine output > 0.5 ml/kg/hour] in preterm or VLBW infants during their first 72 hours of life.

SEARCH METHODS

The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2006) was searched to identify relevant randomised and quasi-randomised controlled trials. The following data bases were searched in June 2006; MEDLINE from 1966, EMBASE from 1980, CINAHL from 1982. Search updated in June 2011.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials conducted in preterm and/or VLBW neonates with a diagnosis of non-oliguric hyperkalaemia. Interventions included were those aimed at redistributing serum potassium (sodium bicarbonate or insulin and glucose) or increasing the elimination of potassium from the body [diuretics (any type) or ion exchange resins (any type), or exchange transfusion, or peritoneal dialysis, or salbutamol, or albuterol] or counteracting potential arrhythmias from hyperkalaemia (calcium) versus placebo or no intervention; or comparing any two of these interventions. Primary outcome measure was 'All cause mortality during initial hospital stay'. Secondary outcomes included common adverse outcomes seen in preterm infants.

DATA COLLECTION AND ANALYSIS

We used the standard review methods of the Cochrane Neonatal Review Group. Two authors assessed all studies identified as potentially relevant by the literature search for inclusion in the review. Statistical methods included relative risk (RR), risk difference (RD), number needed to treat to benefit (NNTB) or number needed to treat to harm (NNTH) for dichotomous and weighted mean difference (WMD) for continuous outcomes reported with 95% confidence intervals (CI). We used a fixed effect model for meta-analysis. Heterogeneity was assessed using the I squared (I(2) ) statistic.

MAIN RESULTS

Three randomised trials, enrolling 74 preterm infants (outcome data available on 71 infants) evaluated interventions for hyperkalaemia. Urine output was ascertained in only one study (Hu 1999). In none of the trials could we ascertain that allocation to the comparison groups was concealed. The sample sizes of the three trials were very small with 12 (Malone 1991), 19 (Singh 2002) and 40 infants enrolled (Hu 1999). The intervention and the outcome assessments could not be blinded to the clinical staff in two trials (Malone 1991; Hu 1999).One study (Malone 1991), glucose and insulin, compared to cation-exchange resin, caused a reduction in all cause mortality that was of borderline statistical significance: RR 0.18 (95% CI 0.03 to 1.15); RD -0.66 (95% CI -1.09 to -0.22); NNTB 2 (95% CI 1 to 5)]. In the study of Hu (Hu 1999), the incidence of intraventricular haemorrhage ≥ grade 2 was significantly reduced [RR 0.30 (95% CI 0.10 to 0.93); RD -0.35 (95% CI -0.62 to -0.08); NNTB 3 (95% CI 2 to 13).Albuterol inhalation versus saline inhalation changed serum K+ from baseline at four hours [WMD -0.69 mmol/L (95% CI -0.87 to -0.51)] and at eight hours [WMD -0.59 mmol/L (95% CI -0.78 to -0.40)] after initiation of treatment. No differences noted in mortality or other clinical outcomes (Singh 2002).No serious side effects were noted with either the combination of insulin and glucose or albuterol inhalation. Other interventions listed in our objectives have not been studied to date.

AUTHORS' CONCLUSIONS

In view of the limited information from small studies of uncertain quality, no firm recommendations for clinical practice can be made. It appears that the combination of insulin and glucose is preferred over treatment with rectal cation-resin for hyperkalaemia in preterm infants. Both the combination of insulin and glucose and albuterol inhalation deserve further study. The two interventions could possibly be tested against each other. The effectiveness of other potentially effective interventions for non-oliguric hyperkalaemia (diuretics, exchange transfusion, peritoneal dialysis and calcium) have not been tested in randomised controlled trials.

Effects of the use of semipermeable membranes on fluid loss in low-birth-weight premature newborns

Studies have shown that the application of semipermeable membranes to the skin of premature newborns (NBs) can aid in protecting the skin, reduce disturbances in fluid and electrolyte levels, and decrease neonatal mortality. The aim of this study was to verify the effect of using semipermeable membranes in low-birth-weight preterm newborns (PTNBs). A randomized controlled trial was carried out in the neonatal intensive care unit (NICU) with 42 NBs split evenly into an intervention group (IG), in which semipermeable membranes were used to cover large areas of the skin for the first 7 days of life, and a control group (CG), which received normal care. The variables investigated for the study were weight, hydration status, urinary density, glycemic control, sodium concentration, and daily hydration quota. The following variables displayed significant daily variation: weight, hydration quota, and sodium concentration. Statistically significant individual effects by day and by group were found only for sodium concentration. In the overall analysis of the intersubject effects, sodium concentration, alone, proved to be significant (p = .055). Significant effects by group in relation to the sodium concentration were found, with the IG showing a lower average sodium concentration than the CG. Thus, the use of semipermeable membranes reduced fluid loss in premature NBs in the current study, confirming the findings of previous studies. Guidelines for practice may now be warranted.

Renal glomerular and tubular function in neonates with perinatal problems

OBJECTIVE

To investigate perinatal risk factors that may be associated with impaired renal function during the first 2 weeks of life.

METHODS

The case notes of 150 neonates of gestational age (GA) 34-36 weeks and 494 of GA > 36 weeks were studied. Clinical risk factors were retrieved, along with indices of renal function: serum creatinine (SeCr), fractional excretion (FE) of sodium (FENa) and potassium (FEK), and the urinary calcium to creatinine ratio (UCa/UCr). Associations were identified by multiple and logistic regression analysis.

RESULTS

In infants with GA > 36 weeks, raised SeCr was related to perinatal stress, odds ratio (OR): 1.9, confidence interval (CI): 1.2-2.9, p < 0.05, and to duration of treatment with aminoglycosides (AGs) (t = 2.4, p < 0.01); FEK was associated with jaundice (t = -3.1, p < 0.01), and FENa with duration of AGs treatment (t = 2.6, p < 0.01). Full-term neonates with both hypoxic-ischemic encephalopathy (HIE) and AGs administration had an 80% increase in OR for impaired SeCr levels. In infants of GA 34-36 weeks, SeCr was related to perinatal stress (OR: 9, CI: 1.3-38, p < 0.05), FEK to jaundice (t = -2.1, p < 0.05), and FENa to duration of AGs administration (t = 2.2, p < 0.05) and antenatal steroid treatment (OR: 0.8, CI: 0.6-0.95, p < 0.05).

CONCLUSION

In neonates, renal impairment, being multifactorial in origin, may be caused by the additive effect of different perinatal factors. The strong negative relationship observed between jaundice and K excretion merits further investigation.

Does parenteral nutrition influence electrolyte and fluid balance in preterm infants in the first days after birth?

Background

New national guidelines recommend more restricted fluid intake and early initiation of total parenteral nutrition (TPN) in very preterm infants. The aim was study the effect of these guidelines on serum sodium and potassium levels and fluid balance in the first three days after birth.

Methods

Two cohorts of infants <28 weeks gestational age, born at the Leiden University Medical Center in the Netherlands, were compared retrospectively before (2002–2004, late-TPN) and after (2006–2007, early-TPN) introduction of the new Dutch guideline. Outcome measures were serum sodium and potassium levels, diuresis, and changes in body weight in the first three postnatal days.

Results

In the first three postnatal days no differences between late-TPN (N = 70) and early-TPN cohort (N = 73) in mean (SD) serum sodium (141.1 (3.8) vs 141.0 (3.7) mmol/l) or potassium (4.3 (0.5) vs 4.3 (0.5) mmol/l) were found, but in the early-TPN cohort diuresis (4.5 (1.6) vs 3.2 (1.4) ml/kg/h) and loss of body weight were decreased (−6.0% (7.7) vs −0.8% (8.0)).

Conclusions

Initiation of TPN immediately after birth and restricted fluid intake in very preterm infants do not seem to influence serum sodium and potassium levels in first three postnatal days. Further research is needed to see if a decreased diuresis and loss of body weight in the first days is the result of a delayed postnatal adaptation or better energy balance.

Phase 1 trial of 4 thyroid hormone regimens for transient hypothyroxinemia in neonates of <28 weeks' gestation

BACKGROUND

Transiently low levels of thyroid hormones occur in approximately 50% of neonates born 24-28 weeks' gestation and are associated with higher rates of cerebral palsy and cognitive impairment. Raising hormone levels shows promise for improving neurodevelopmental outcome.

OBJECTIVE

To identify whether any of 4 thyroid hormone supplementation regimens could raise T(4) and FT(4) without suppressing TSH (biochemical euthyroidism).

METHODS

Eligible subjects had gestational ages between 24 07 and 2767 weeks and were randomized <24 hours of birth to one of six study arms (n = 20-27 per arm): placebo (vehicle: 5% dextrose), potassium iodide (30 microg/kg/d) and continuous or bolus daily infusions of either 4 or 8 microg/kg/d of T(4) for 42 days. T(4) was accompanied by 1 microg/kg/d T(3) during the first 14 postnatal days and infused with 1 mg/mL albumin to prevent adherence to plastic tubing.

RESULTS

FT(4) was elevated in the first 7 days in all hormone-treated subjects; however, only the continuous 8 microg/kg/d treatment arm showed a significant elevation in all treatment epochs (P < .002 versus all other groups). TT(4) remained elevated in the first 7 days in all hormone-treated subjects (P < .05 versus placebo or iodine arms). After 14 days, both 8 microg/kg/d arms as well as the continuous 4 microg/kg/d arm produced a sustained elevation of the mean and median TT(4), >7 microg/dL (90 nM/L; P < .002 versus placebo). The least suppression of THS was achieved in the 4 microg/kg/d T(4) continuous infusion arm. Although not pre-hypothesized, the duration of mechanical ventilation was significantly lower in the continuous 4 microg/kg/d T(4) arm and in the 8 microg/kg/d T(4) bolus arm (P < .05 versus remaining arms). ROP was significantly lower in the combined 4 thyroid hormone treatment arms than in the combined placebo and iodine arms (P < .04). NEC was higher in the combined 8 microg/kg/d arms (P < .05 versus other arms).

CONCLUSIONS

Elevation of TT(4) with only modest suppression of TSH was associated with trends suggesting clinical benefits using a continuous supplement of low-dose thyroid hormone (4 microg/kg/d) for 42 days. Future trials will be needed to assess the long-term neurodevelopmental effects of such supplementation.

Alpha-ketoglutarate protects the liver of piglets exposed during prenatal life to chronic excess of dexamethasone from metabolic and structural changes

Glucocorticoids play a role in the origin of the features of the metabolic diseases. Alpha-ketoglutarate (AKG) is defined as glutamine homologue and derivative, conditionally an essential amino acid. In the liver, glutamine serves as a precursor for ureagenesis, gluconeogenesis and acute phase protein synthesis The aim of the study was to determine the effect of AKG administered to piglets prenatally exposed to dexamethasone, on the structure of the liver and its metabolic function. Sows were administered with dexamethasone (3 mg/sow/48 h) from day 70 of pregnancy to the parturition, and then after the birth, the piglets were divided into the group administered with AKG (0.4 g/kg body weight) or physiological saline. Biochemical markers, lysozyme and ceruloplasmin serum activities, concentrations of selected free amino acids, macro- and microelements and histomorphometry of the liver tissue were determined. The total cholesterol concentrations in the sows and their newborns from the Dex groups were higher by 72% and 64%, respectively, compared with the control groups. Triacylglycerol concentration was higher by 50% in sows from the Dex group and 55% in the new-born piglets. Alpha-ketoglutarate administered to the piglets after prenatal influence of dexamethasone lowered the total cholesterol concentration by 40%, and enhanced aspartate by 41%, serine by 76%, glutamate by 105%, glutamine by 36%, glycine by 53% and arginine by 105%, as well as methionine and cystathionine, but increased the sulphur concentration compared with the control (p < 0.01). Intracellular space D decreased after AKG administration in comparison with the piglets from Dex/Control group not treated with AKG. Postnatal administration of AKG had a protective effect on liver structure, and lowered the total cholesterol concentration in piglets prenatally exposed to dexamethasone, and also influenced selected macro- and microelement serum concentrations and amino acids plasma concentration.

Metabolic responses to early and high protein supplementation in a randomized trial evaluating the prevention of hyperkalemia in extremely low birth weight infants

OBJECTIVE

To determine whether early and higher intravenous amino acid (EHAA) supplementation decreases hyperkalemia in extremely low birth weight (ELBW) infants (<1000 g).

STUDY DESIGN

Infants were enrolled at birth in a randomized, double-masked, prospective fashion and treated for 7 days. The standard group (SAA) infants received intravenous amino acid (AA) starting at 0.5 g x kg(-1) x d(-1) and increased by 0.5 g x kg(-1) every day to a maximum of 3 g x kg(-1) x d(-1). EHAA group infants received 2 g x kg(-1) x d(-1) of AA soon after birth and advanced by 1 g x kg(-1) every day to 4 g x kg(-1) x d(-1). Data analysis was by SPSS 11.5, with statistical significance at alpha = 0.05 and 90% power to determine a difference in mean K(+) level of 2.

RESULTS

Sixty-two patients, mean gestational age of 26.0 +/- 2.0 weeks and birth weight of 775 +/- 136 g, were enrolled. Hyperkalemia (K(+) > or =6.5 mEq/L) occurred in 13% of the studied population; no difference in incidence of hyperkalemia was found between the SAA and EHAA groups (16% vs 10%, respectively, P = .70). Serum blood urea nitrogen was higher in the EHAA group. AA infusion was stopped early in 6 patients for high blood urea nitrogen or elevated ammonia level.

CONCLUSIONS

During the study period, hyperkalemia decreased significantly and was not affected by EHAA supplementation in the first week of life.

Interventions for non-oliguric hyperkalaemia in preterm neonates

BACKGROUND

Non-oliguric hyperkalaemia of the newborn is defined as a plasma potassium level > 6.5 mmol/L in the absence of acute renal failure. Hyperkalaemia is a common complication in the first 48 hours of life in very low birth weight (birth weight < 1500 g) and/or very preterm newborns (< 32 weeks gestational age).

OBJECTIVES

To determine the effectiveness and safety of interventions for non-oliguric hyperkalaemia [for the purpose of this review defined as serum potassium > 6.0 mmol/L ( the clinical setting in which interventions would likely be introduced prior to reaching a grossly abnormal level) and a urine output > 0.5 ml/kg/hour] in preterm or very low birth weight (VLBW) infants during their first 72 hours of life.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2006) was searched to identify relevant randomised and quasi-randomised controlled trials. The following data bases were searched in June 2006; MEDLINE from 1966, EMBASE from 1980, CINAHL from 1982.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials conducted in preterm and/or VLBW neonates with a diagnosis of non-oliguric hyperkalaemia. The interventions included were those aimed at redistributing serum potassium (sodium bicarbonate or insulin and glucose) or increasing the elimination of potassium from the body [diuretics (any type) or ion exchange resins (any type), or exchange transfusion, or peritoneal dialysis, or salbutamol, or albuterol] or counteracting potential arrhythmias from hyperkalaemia (calcium) vs. placebo or no intervention; or comparing any two of these interventions. The primary outcome measure was 'All cause mortality during initial hospital stay'. Secondary outcomes included common adverse outcomes seen in infants born preterm.

DATA COLLECTION AND ANALYSIS

The standard review methods of the Cochrane Neonatal Review Group were used. All studies identified as potentially relevant by the literature search were assessed for inclusion in the review by the two authors. The statistical methods included relative risk (RR), risk difference (RD), number needed to treat to benefit (NNTB) or number needed to treat to harm (NNTH) for dichotomous and weighed mean difference (WMD) for continuous outcomes reported with 95% confidence intervals (CI). A fixed effects model was used for meta-analysis. Heterogeneity was assessed using the I squared (I(2 )) statistic.

MAIN RESULTS

Three randomized trials, enrolling 74 preterm infants (outcome data available on 71 infants) evaluated interventions for hyperkalemia. Urine output was ascertained only in one study (Hu 1999). In none of the trials could we ascertain that allocation to the comparison groups was concealed. The sample sizes of the three trials were very small with 12 (Malone 1991), 19 (Singh 2002) and 40 infants enrolled (Hu 1999). The intervention and the outcomes assessments could not be blinded to the clinical staff in two trials (Hu 1999; Malone 1991). In one study (Malone 1991), glucose and insulin, compared to cation-exchange resin, caused a reduction in all cause mortality that was of borderline statistical significance: RR 0.18 (95% CI 0.03, 1.15); RD -0.66 (95% CI -1.09, -0.22); NNTB 2 (95% CI 1, 5)]. In the study of Hu (Hu 1999), the incidence of intraventricular haemorrhage > grade 2 was significantly reduced [RR 0.30 (95% CI; 0.10, 0.93); RD -0.35 (95% CI; -0.62, -0.08); NNTB 3 (95% CI; 2, 13). Albuterol inhalation vs. saline inhalation changed serum K+ from baseline at 4 hours [WMD -0.69 mmol/L (95% CI; -0.87, -0.51)] and at 8 hours [WMD -0.59 mmol/L (95% CI; -0.78, -0.40)] after initiation of treatment. No differences were noted in mortality or other clinical outcomes (Singh 2002). No serious side effects were noted with either the combination of insulin and glucose or albuterol inhalation. Other interventions that we listed in our objectives have not been studied to date.

AUTHORS' CONCLUSIONS

In view of the limited information from small studies of uncertain quality, no firm recommendations for clinical practice can be made. It appears that the combination of insulin and glucose is preferred over treatment with rectal cation-resin for hyperkalaemia in preterm infants. Both the combination of insulin and glucose and albuterol inhalation deserve further study. The two interventions could possibly be tested against each other. The effectiveness of other potentially effective interventions for non-oliguric hyperkalaemia (diuretics, exchange transfusion, peritoneal dialysis and calcium) have not been tested in randomized controlled trials.

[Metabolism of potassium in preterm infants]

During the first days of life, hyperkalemia can affect 30 to 60% of very low birth weight infants free of acute renal insufficiency (i.e. nonoliguric hyperkalemia). The place of the kidney in the regulation of the potassium homeostasis of VLBW remains badly specified.

OBJECTIVE

To evaluate the rate and the mechanisms of hyperkalemia in infants born at less than 32 weeks' gestation.

METHODS

A prospective study was conducted in 33 preterm infants (BW=1289+/-382 g; GA=28.8+/-1.7 weeks). Fifteen consecutive 8-hour urine collections were performed for each infant from the 8th hour of life (495 periods). A plasma sample was obtained at the end of each urine collection. Sodium, potassium and creatinine were measured in urine and blood samples as often as possible.

RESULTS

Plasma potassium concentrations varied significantly over the 15 successive periods with an initial value (P1) of 4.55+/-0.80 mmol/l, a peak on P3 (4.94+/-0.81 mmol/l) and the lowest value on P13 (3.88+/-0.42 mmol/l). Hyperkalemia (plasma potassium>6.0 mmol/l) was observed in 4 infants (12%) and in 1.2% of the periods. The cumulative potassium balance (output-input) was negative over the first 7 periods (-1.97 mmol/kg), and afterwards became positive (from P8 to P15:+1.57 mmol/kg). Over the first 3 days, plasma potassium concentrations were positively correlated (p<0.01) with urinary excretion of potassium, clearance of potassium, fractional excretion of potassium, and negatively with endogenous creatinine clearance.

CONCLUSION

In the first days of life, very low birth weight infants present an increase in kalemia associated with a negative potassium balance indicating a intracellular to extracellular potassium shift rather than a lower renal potassium excretion.

Effects of maternally administered drugs on the fetal and neonatal kidney

The number of pregnant women and women of childbearing age who are receiving drugs is increasing. A variety of drugs are prescribed for either complications of pregnancy or maternal diseases that existed prior to the pregnancy. Such drugs cross the placental barrier, enter the fetal circulation and potentially alter fetal development, particularly the development of the kidneys. Increased incidences of intrauterine growth retardation and adverse renal effects have been reported. The fetus and the newborn infant may thus experience renal failure, varying from transient oligohydramnios to severe neonatal renal insufficiency leading to death. Such adverse effects may particularly occur when fetuses are exposed to NSAIDs, ACE inhibitors and specific angiotensin II receptor type 1 antagonists. In addition to functional adverse effects, in utero exposure to drugs may affect renal structure itself and produce renal congenital abnormalities, including cystic dysplasia, tubular dysgenesis, ischaemic damage and a reduced nephron number. Experimental studies raise the question of potential long-term adverse effects, including renal dysfunction and arterial hypertension in adulthood. Although neonatal data for many drugs are reassuring, such findings stress the importance of long-term follow-up of infants exposed in utero to certain drugs that have been administered to the mother.

Glucocorticoid responsiveness in developing human intestine: possible role in prevention of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a major inflammatory disease of the premature human intestine that can be prevented by glucocorticoids if given prenatally before the 34th wk of gestation. This observation suggests that a finite period of steroid responsiveness exists as has been demonstrated in animal models. Human intestinal xenografts were used to determine whether a glucocorticoid responsive period exists in the developing human intestine. Developmental responsiveness was measured by lactase activity and inflammatory responsiveness by IL-8, IL-6, and monocyte chemotactic protein-1 (MCP-1) induction after an endogenous (IL-1 beta) or exogenous (LPS) proinflammatory stimulus, respectively. Functional development of ileal xenografts were monitored for 30 wk posttransplantation, and the lactase activity recapitulated that predicted by in utero development. Cortisone acetate accelerated the ontogeny of lactase at 20 wk (immature) but the effect was lost by 30 wk (mature) posttransplant. Concomitant with accelerated maturation, the IL-8 response to both IL-1 beta and LPS was significantly dampened (from 6- to 3-fold) by glucocorticoid pretreatment in the immature but not mature xenografts. The induction of IL-8 was reflected at the level of IL-8 mRNA, suggesting transcriptional regulation. The excessive activation of IL-8 in the immature gut was mediated by a prolonged activation of ERK and p38 kinases and nuclear translocation of NF-kappa B due to low levels of I kappa B. Steroid pretreatment in immature intestine dampens activation of all three signaling pathways in response to proinflammatory stimuli. Therefore, accelerating intestinal maturation by glucocorticoids within the responsive period by accelerating functional and inflammatory maturation may provide an effective preventive therapy for NEC.

Renal potassium handling in healthy and sick newborns

Growing infants must maintain a state of positive K+ balance, a task accomplished, in large part, by the kidney. The distal nephron is uniquely adapted to retain total body K+ early in life. The magnitude and direction of net K+ transport in the cortical collecting duct (CCD), the segment responsible for the final renal regulation of K+ balance in the adult, reflect the balance of opposing fluxes of K+ secretion and K+ absorption. Evidence now indicates that the low capacity of the neonatal CCD for K+ secretion is due, at least in part, to a relative paucity of conducting K+ channels in the urinary membrane. A relative excess of K+ absorption in this nephron segment may further reduce net urinary K+ secretion. Under conditions prevailing in vivo, the balance of fluxes in the CCD likely contributes to the relative K+ retention characteristic of the neonatal kidney.

Hypernatraemia induced by sodium polystyrene sulphonate (Kayexalate) in two extremely low birth weight newborns

Hyperkalaemia is a life-threatening electrolyte disorder that can occur in the first week of life in almost 50% of preterm infants with a birth weight less than 1000 g [extremely low birth weight (ELBW)]. Serum potassium values higher than 7 mmol x l-1 are associated with cardiac arrhythmias and an increased incidence of intraventricular haemorrhage and periventricular leucomalacia. Therapeutic options to treat this dangerous imbalance comprise calcium gluconate, insulin plus glucose, albuterol/salbutamol inhalation. Administration of cation-exchange resin such as sodium polystyrene sulphonate (Kayexalate) is effective in lowering plasma potassium, although complications following oral or rectal administration are reported in newborns. We describe two ELBW infants affected by hyperkalaemia, treated with Kayexalate, who developed serious hypernatraemia, that has never been reported before in preterm infants.

Hereditary disorders of potassium homeostasis

There has been a dramatic recent increase in the understanding of the renal epithelial transport systems with the identification, cloning and characterization of a large number of membrane transport proteins. The aim of this chapter is to integrate this body of knowledge with the understanding of the clinical disorders that accompany gain, loss or dysregulation of function of these transport systems. The specific focus is on the best-defined human clinical syndromes in which there are derangements in potassium (K(+)) homeostasis. The focus is on inherited syndromes, rather than on acquired syndromes due to tubular transport defects, and the therapeutic approaches address chronic derangements of K(+) homeostasis rather than acute interventions directed at life-threatening hyperkalaemia.

Antenatal steroid treatment prevents severe hyperkalemia in very low-birthweight infants

BACKGROUND

Hyperkalemia is seen quite often in very low-birthweight (VLBW) infants and concentrations sometimes become high enough to cause cardiac arrhythmia. The purpose of the present study was to identify factors that increase serum concentrations of potassium in VLBW infants.

METHODS

Retrospective comparative analysis was performed on 140 VLBW infants who had been admitted to the Toho University Perinatal Center between January 1993 and December 1999 and needed mechanical ventilation for respiratory distress. Serum concentrations of potassium at 24 and 48 h of age were compared in two groups of infants, those whose mothers did and did not receive antenatal steroid treatment. Risk factors for severe hyperkalemia were analyzed by multiple linear regression models and Pearson's partial correlation analysis.

RESULTS

Antenatal steroid treatment reduced serum potassium concentrations significantly at 24 and 48 h, as well as the incidence of cardiac arrhythmia and necessity for glucose insulin treatment for severe hyperkalemia. Multiple linear regression showed the serum potassium concentration at 24 h of age was associated with antenatal steroid hormone treatment, 24 h fluid intake volume, serum sodium concentrations at 24 h, gestational weeks and sampling site. Serum concentration of potassium at 48 h of age was associated with blood urea nitrogen, gestational week, serum sodium concentration at 48 h of age and fluid intake between 24 and 48 h of age. Urine output volume and serum creatinine concentrations were not correlated with potassium concentrations at either age.

CONCLUSION

Antenatal steroid hormone treatment can reduce early hyperkalemia in VLBW infants and also the incidence of cardiac arrhythmia and the use of glucose insulin treatment.

New perspectives on nutrition enhance outcomes for premature infants

Significant advances have occurred during the past 20 years in the understanding of the complex relationships of the environment, the developing gut-associated immune system, the bacterial flora, the barrier functions of the gut, and the effects of nutrient intake. These advances have produced a profoundly different way of interpreting the nutritional requirements for normal growth and development of premature infants throughout their entire life.

Antenatal treatment with corticosteroids for preterm neonates: impact on the incidence of respiratory distress syndrome and intra-hospital mortality

CONTEXT

Although the benefits of antenatal corticosteroids have been widely demonstrated in other countries, there are few studies among Brazilian newborn infants.

OBJECTIVE

To evaluate the effectiveness of antenatal corticosteroids on the incidence of respiratory distress syndrome and intra-hospital mortality among neonates with a gestational age of less than 34 weeks.

TYPE OF STUDY

Cross-sectional.

SETTING

A tertiary-care hospital.

PARTICIPANTS

Neonates exposed to any dose of antenatal corticosteroids for fetal maturation up to 7 days before delivery, and newborns paired by sex, birth weight, gestational age and time of birth that were not exposed to antenatal corticosteroids. The sample obtained consisted of 205 exposed newborns, 205 non-exposed and 39 newborns exposed to antenatal corticosteroids for whom it was not possible to find an unexposed pair.

PROCEDURES

Analysis of maternal and newborn records.

MAIN MEASUREMENTS

The primary clinical outcomes for the two groups were compared: the incidence of respiratory distress syndrome and intra-hospital mortality; as well as secondary outcomes related to neonatal morbidity.

RESULTS

Antenatal corticosteroids reduced the occurrence of respiratory distress syndrome (OR: 0.33; 95% CI: 0.21-0.51) and the protective effect persisted when adjusted for weight, gestational age and the presence of asphyxia (adjusted OR: 0.27; 95% CI: 0.17-0.43). The protective effect could also be detected through the reduction in the need for and number of doses of exogenous surfactant utilized and the number of days of mechanical ventilation needed for the newborns exposed to antenatal corticosteroids. Their use also reduced the occurrence of intra-hospital deaths (OR: 0.51: 95% CI: 0.38-0.82). However, when adjusted for weight, gestational age, presence of prenatal asphyxia, respiratory distress syndrome, necrotizing enterocolitis and use of mechanical ventilation, the antenatal corticosteroids did not maintain the protective effect in relation to death. With regard to other outcomes, antenatal corticosteroids reduced the incidence of intraventricular hemorrhage grades III and IV (OR: 0.28; 95% CI: 0.10-0.77).

CONCLUSIONS

Antenatal corticosteroids were effective in the reduction of morbidity and mortality among premature newborns in the population studied, and therefore their use should be stimulated within our environment.

Association of antenatal and postnatal dexamethasone exposure with outcomes in extremely low birth weight neonates

BACKGROUND

Recent studies of preterm neonates have indicated that antenatal dexamethasone (ADX) may have adverse effects on cranial ultrasound findings at the time of hospital discharge, including periventricular leukomalacia. Furthermore, both ADX and postnatal dexamethasone (PDX) may have adverse effects on subsequent neurodevelopmental outcome.

OBJECTIVES

1) To assess the effects of ADX exposure on cranial ultrasound findings at the time of hospital discharge and 2) to evaluate the individual effects of ADX and/or PDX exposure on subsequent neurodevelopmental outcome in extremely low birth weight (ELBW) neonates in whom confounding risk factors known to influence outcome were controlled.

METHODS

One hundred seventy-three ELBW (< or =1000 g) neonates were studied using a prospectively collected database and hospital and clinic records. Study patients were assigned to 1 of 4 groups according to dexamethasone exposure: group I, no dexamethasone exposure; group II, ADX exposure to hasten fetal lung maturity; group III, PDX exposure for chronic lung disease; group IV, both ADX and PDX exposure. The 4 groups were compared using multinomial logistic regression or analysis of covariance to control for confounding variables. Primary outcome variables were cranial ultrasound findings at hospital discharge and results of developmental testing at 18 to 22 months' corrected age (Bayley Scales of Infant Development).

RESULTS

Cranial ultrasound results as well as Bayley Scales of Infant Development scores were similar in groups I and II and in groups III and IV. The likelihood of abnormal cranial ultrasound studies and lower scores on neurodevelopmental testing was greater in groups III and IV versus groups I and II. In this study, ADX did not seem to increase the risk of periventricular leukomalacia.

CONCLUSIONS

ADX exposure is not associated with an increase in abnormal cranial ultrasound findings in ELBW neonates. PDX exposure, but not ADX exposure, is associated with worse neurodevelopmental outcome in this population. These results are supportive of the recent statement by the American Academy of Pediatrics (Committee on Fetus and Newborn) and the Canadian Paediatric Society (Fetus and Newborn Committee) and emphasize that PDX should be used with caution in ELBW neonates.

Renal genetic disorders related to K+ and Mg2+

The recent knowledge of the renal epithelial transport systems has exploded with the identification, cloning, and characterization of a large number of membrane transport proteins. The fundamental aspects of these transporters are beginning to emerge at the molecular level and are summarized in the accompanying contributions in this volume of the Annual Review of Physiology. The aim of my review is to integrate this body of knowledge with the understanding of the clinical disorders of human mineral homeostasis that accompany gain, loss, or dysregulation of function of these transport systems. The specific focus is on the best defined human clinical syndromes in which there are derangements in K(+) and Mg(2+) homeostasis.