Pathophysiology of Hyponatremia in Preterm Infants with Relative Adrenal Insufficiency after the Early Neonatal Period

OBJECTIVE

 Preterm infants often develop relative adrenal insufficiency (RAI) not only within the early neonatal period but also beyond this period. RAI is commonly accompanied by hyponatremia, but the pathogenesis of hyponatremia with RAI has not been clarified. This study aimed to investigate the pathophysiology of hyponatremia in infants with RAI.

STUDY DESIGN

 This is a single-centered retrospective cohort study. Preterm infants born at <30 weeks of gestation or birth weight <1,000 g were enrolled. They were divided into the RAI group and the non-RAI group. The data of serum and urine examination, the amount of sodium intake, and fractional excretion of sodium (FENa) were compared between the two groups. In the RAI group, data before and after the administration of hydrocortisone were also compared.

RESULTS

 Sixteen infants in the RAI group and 35 infants in the non-RAI group were included in the analysis. In the RAI group, hyponatremia was common and preceded other clinical symptoms, such as oliguria and decreased blood pressure, therefore, hyponatremia with RAI was not likely to be caused by dilution due to oliguria. There was no difference in the FENa between the two groups (adjusted for postconceptional age at examination), therefore, it is not likely that hyponatremia with RAI was mainly caused by excessive renal sodium loss. Since sodium intake was rather higher in the RAI group than in the non-RAI group, it is unlikely that insufficient sodium supplementation was the cause of RAI. Hyponatremia with RAI was considered to be likely caused by vascular hyperpermeability.

CONCLUSION

 Hyponatremia is a common symptom among preterm infants with RAI and its pathogenesis can be vascular hyperpermeability.

KEY POINTS

· The pathogenesis of hyponatremia with RAI can be vascular hyperpermeability.. · Hyponatremia is common among preterm infants with RAI.. · Hyponatremia with RAI preceded other clinical symptoms..

Post-natal steroid exposure in very low birthweight neonates and associations with acute kidney injury

OBJECTIVE

The relationship between adrenal insufficiency (AI), post-natal steroids (PNS) and neonatal acute kidney injury (AKI) remains understudied. We investigated associations between PNS and AKI in very low birthweight (VLBW) neonates, hypothesizing PNS is associated with reduced AKI.

STUDY DESIGN

We conducted a single-center retrospective review of VLBW infants comparing those with and without PNS exposure. Associations between PNS exposure and AKI were evaluated using generalized linear mixed-modeling adjusted for confounders.

RESULT

Of 567 neonates, 97 (17.1%) were exposed to PNS and 130 (22.9%) experienced AKI. Infants with PNS had lower gestational age, birthweight, Apgar scores, and experienced more AI versus those without PNS (all p < 0.05). PNS was associated with AKI (aRR 1.72, 95% CI 1.09-2.72) though hydrocortisone alone was not.

CONCLUSION

PNS exposure, but not hydrocortisone alone, is associated with increased AKI in VLBW neonates. Further analysis is needed to investigate the role of AI and AKI.

Acute effect of hydrocortisone for respiratory deterioration in preterm infants: Oxygenation, ventilation, vital signs, and electrolytes

BACKGROUND

Preterm infants with severe bronchopulmonary dysplasia require rescue therapy with glucocorticoids, and hydrocortisone is increasingly replacing dexamethasone. The standard for rescue therapy is unclear.

AIM

To quantify the short-term effects of respiratory rescue hydrocortisone of 4 mg/kg/day for 3 days.

STUDY DESIGN

Retrospective single-center study.

SUBJECTS

Ventilator-dependent infants born at <28 weeks of gestation with an increased oxygen demand to maintain the target oxygen saturation at 88% to 95% >1 week after birth.

OUTCOME MEASURES

Ventilator settings, SpO₂/FiO₂ ratio, heart rate, and blood parameters within 24 h before and 228 h after starting hydrocortisone.

RESULTS

Twenty-five infants (median gestational age, 25.1 weeks) received hydrocortisone at a median age of 16 days. The median pre-therapy SpO₂/FiO₂ was 297 (interquartile range, 265-320) and began to rise after 12 h of administration, reaching 307 (interquartile range, 278-335). The increase in SpO₂/FiO₂ peaked from the third day to 3 days after therapy (median range, 341-356). SpO₂/FiO₂ decreased thereafter and remained unchanged from 6 and 7 days after therapy (median range, 304-314). The pCO₂ level (median range, 49-53 mmHg) did not change significantly. The heart rate significantly decreased from -4 to -6 beats/min from the first day to 1 day after therapy. Systolic blood pressure increased by a median of 4 to 8 mmHg after therapy. Blood electrolytes and glucose were similar after therapy.

CONCLUSION

Rescue hydrocortisone administration improved oxygenation without particular adverse effects at the stage of respiratory deterioration in preterm infants.

Clinical risk factors for the development of late-onset circulatory collapse in premature infants

BACKGROUND

Very low birth weight (VLBW) infants may be at risk for late-onset circulatory collapse (LCC) where otherwise stable infants develop hypotension resistant to vasoactive agents. The risk factors for LCC development are poorly defined, and it has been theorized that it may be in part due to withdrawal from exogenous prenatal steroids. The goal of this study was to define the clinical characteristics of LCC and investigate its association with antenatal steroid administration.

METHODS

This is a retrospective cohort study of infants born ≤1500 g. LCC was retrospectively diagnosed in infants requiring glucocorticoids for circulatory instability at >1 week of life. Demographic and clinical characteristics were compared between groups using Mann-Whitney test.

RESULTS

Three hundred and ten infants were included; 19 (6.1%) developed LCC. Infants with LCC were born at a median 4.6 weeks' lower gestation, 509 g lower birth weight than those without LCC. There was no difference in antenatal steroid delivery between the groups.

CONCLUSIONS

LCC occurs in a distinct subset of VLBW infants, suggesting the need for monitoring in this high-risk population. Antenatal steroids did not significantly increase the risk of LCC development in this study.

IMPACT

Late-onset circulatory collapse (LCC) is a life-threatening clinical entity occurring in around 6% in VLBW infants and is likely underdiagnosed in the United States. Targeting specific demographic characteristics such as birth weight (<1000 g) and gestational age at birth (<26 weeks) may allow for early identification of high-risk infants, allowing close monitoring and prompt treatment of LCC. No significant association was found between antenatal steroid administration and LCC development, suggesting that the theoretical risks of antenatal steroids on the fetal HPA axis does not outweigh the benefits of antenatal steroids in fetal lung maturity. To date, no studies characterizing LCC have originated outside of Asia. Therefore, providing a description of LCC in a U.S.-based cohort will provide insight into both its prevalence and presentation to inform clinicians about this potentially devastating disorder and foster early diagnosis and treatment. This study validates LCC characteristics and prevalence previously outlined by Asian studies in a single-center U.S.-based cohort while also identifying potential risk factors for LCC development. This manuscript will provide education for U.S. physicians about the risk factors and clinical presentation of LCC to facilitate early diagnosis and treatment, potentially decreasing neonatal mortality. With prompt recognition and treatment of LCC, infants may have decreased exposure to vasoactive medications that have significant systemic effects.

Organ blood flow in response to infusion of arginine vasopressin in premature fetal sheep

BACKGROUND

Arginine vasopressin (AVP) infusion has been shown to be a useful strategy for the management of systemic perfusion failure in premature infants. Our objective was to determine the characteristics of the blood flow redistribution induced by AVP infusion in premature fetal sheep.

METHODS

Nine sheep fetuses at 99 to 113 days of gestation were continuously infused with AVP. Measurement of blood flow to individual fetal organs was performed using a colored microsphere technique, with measurements performed at 30 min before and 90 min after the initiation of AVP infusions.

RESULTS

The AVP infusion significantly increased blood flow to the medulla oblongata (P < 0.05), and significantly decreased flow to the adrenal glands (from 492.0 ± 239.6 to 364.9 ± 143.3 mL/min/100 g, P < 0.05) and heart (from 592.6 ± 184.5 to 435.6 ± 137.4 mL/min/100 g, P < 0.05). The infusion significantly increased the vascular resistance in adrenal glands, kidneys, ileum, colon, heart, and cerebellum. In the brain, except for the cerebellum, no significant increase in resistance was identified.

CONCLUSIONS

There was no significant response to AVP infusion in cerebral blood flow in mid-gestation fetal sheep. Our observations suggest that, under AVP stimulation, the blood flow to the adrenal glands and myocardium might be decreased due to an increase in vascular resistance.

Late-onset glucocorticoid-responsive circulatory collapse in premature infants

Late-onset glucocorticoid-responsive circulatory collapse (LGCC) in infants is characterized by sudden onset of hypotension and/or oliguria, which is resistant to volume expanders and inotropes but responds rapidly to intravenous glucocorticoids. LGCC occurs after the first week of life mainly in relatively stable very low birth weight (VLBW) infants. In Japan, the incidence of LGCC is reported to be 8%. Relative adrenal insufficiency (AI) is considered the most likely cause of LGCC, but its detailed pathophysiology remains unclear. Intrinsic and extrinsic factors may affect the pathophysiological mechanism. LGCC should be recognized as one of the high-risk complications in VLBW infants and managed promptly and properly, because if it is not, it may cause life-long neurological problems. To diagnose relative AI, an accurate evaluation of adrenal function is necessary; however, the interpretation of basal serum cortisol levels is difficult in preterm infants after 7 days of life. To recognize LGCC, it is recommended that blood pressure and urine volume be carefully monitored, even outside of the transitional period. If no underlying causes are documented or volume expansion and inotropic support fail, intravenous hydrocortisone should be initiated, and an additional dose of hydrocortisone is required when the response is inadequate. There are few reports to verify or characterize LGCC and this phenomenon has not been recognized worldwide to date. This review summarizes the current knowledge about LGCC in premature infants and evaluates the most significant new findings regarding its pathophysiology, treatment, and prognosis.

Neonatal factors related to center variation in the incidence of late-onset circulatory collapse in extremely preterm infants

BACKGROUND

Although late-onset circulatory collapse (LCC) is widely recognized in Japan, its etiology and the reason for center variation in its incidence remain unclear. This study's objectives were to identify the perinatal and neonatal factors related to LCC and to estimate the factors related to the center variation in the incidence of LCC.

METHODS

Extremely preterm infants born between 2008 and 2012 who were registered in the database of the Neonatal Research Network, Japan were retrospectively analyzed. LCC was defined as a clinical diagnosis of LCC and the administration of steroids. We first identified the factors that were significantly related to LCC. We then examined the cause of the center variation in the incidence of LCC, using the standardized incidence ratios (SIRs) of LCC and individual factors.

RESULTS

The factors significantly associated with LCC included low gestational age (odds ratio [OR]: 1.13), small for date (OR: 1.43), male sex (OR: 1.26), antenatal steroid use (OR: 1.19), respiratory distress syndrome (OR: 1.25), chronic lung disease at 36 weeks (OR: 1.16), periventricular leukomalacia (PVL) (OR: 2.57), necrotizing enterocolitis (OR: 0.59), retinopathy of prematurity (ROP) (OR: 1.73), high-frequency oscillating ventilation (HFOV) use (OR: 1.31), parenteral nutrition (OR: 1.38), and red blood cell (RBC) transfusion (OR: 1.94). The SIR of LCC ranged from 0.05 to 2.94, and was positively correlated with SIRs of PVL, ROP, HFOV use and RBC transfusion.

CONCLUSION

PVL, ROP, HFOV use and RBC transfusion were found to be correlated with the center variation in the incidence of LCC.

Late-onset transient adrenal insufficiency in preterm twins with twin-to-twin transfusion syndrome: A case report

RATIONALE

Late-onset transient adrenal insufficiency with circulatory collapse is a rare condition that occurs in preterm infants. Although the incidence of late-onset transient adrenal insufficiency in preterm infants has been reported in Japan, reports from Western countries are lacking. In addition, no study has investigated the effect of twin-to-twin transfusion syndrome (TTTS) in monozygotic twins.

PATIENT CONCERNS

A pair of extremely low birth weight twins presented with TTTS.

DIAGNOSES

Both twins developed late-onset adrenal insufficiency with oliguria, hypotension, hyponatremia, and pulmonary edema at a postnatal age of 24 days and 51 days, respectively.

INTERVENTION

Temporary administration of intravenous hydrocortisone was initiated.

OUTCOMES

Their symptoms improved dramatically and they survived the event without any neurologic sequelae after 3 years of follow-up.

LESSONS

Late-onset circulatory collapse may occur, especially in extremely preterm infants, even at 2 months after birth. Hydrocortisone therapy is an effective treatment to rescue circulatory collapse caused by adrenal insufficiency in preterm infants and may not affect long-term neuromotor and cognitive outcomes.

Assessment of neonatal adrenal size using high resolution 2D ultrasound and its correlation with birth demographics and clinical outcomes

OBJECTIVE

Assessment of adrenal function in a sick neonate remains a challenge in spite of major advances in neonatal care. We used 2D ultrasound of adrenal glands to assess maturity of adrenal glands in extremely preterm infants and sick term and near term infants.

STUDY DESIGN

We collected demographics details of 99 mother-infants pairs (24-41 weeks) and obtained 2D ultrasound scans of adrenal glands in first week of life to measure adrenal volume, fetal zone size, and adrenal to kidney ratios. Relationship between adrenal measurements, antenatal factors, and postnatal outcomes were studied.

RESULTS

We reported normative adrenal gland volume data during gestation from 80 appropriate for gestational age (AGA) infants. In a binary analysis, adrenal size was significantly related to gender, race, intrauterine growth restriction (IUGR), maternal chorioamnionitis, and maternal hypertension. Linear regression analysis showed that fetal zone is significantly related to not only gestational age but also chorioamnionitis and later development of intraventricular hemorrhage (IVH). Adrenal volume likewise is also related to gestational age, preeclampsia, and IVH.

CONCLUSIONS

Antenatal maternal factors and uterine environment affects adrenal growth and development thus postnatal high resolution 2D US scan of adrenal glands can provide useful information to predict outcomes. This information can complement hormone and adrenocorticotrophic hormone (ACTH) stimulation assays.

Late-onset circulatory collapse of prematurity

Late-onset circulatory collapse (LCC) is a refractory hypotension occurring after the early neonatal period (>day 7), in very low-birthweight infants. Typically, infants stabilized within the early neonatal period develop sudden onset of circulatory collapse after the early neonatal period. The underlying pathophysiology of LCC is considered to be relative adrenal insufficiency, which is well known in Japan, but is not widely accepted in North America or Europe. The current increase in LCC in Japan suggests that the principal trigger is related to recent trends in neonatal medicine and/or newly introduced treatments for preterm infants, but the pathophysiology has not been fully elucidated. In this review, based on current knowledge regarding LCC, the pathophysiology is discussed.

Brain ultrasonographic findings of late-onset circulatory dysfunction due to adrenal insufficiency in preterm infants

Purpose:

The aim of this study was to characterize the brain ultrasonographic findings of late-onset circulatory dysfunction (LCD) due to adrenal insufficiency (AI) in preterm infants.

Methods:

Among the 257 preterm infants born at <33 weeks of gestation between December 2009 and February 2014 at our institution, 35 preterm infants were diagnosed with AI. Brain ultrasonographic findings were retrospectively analyzed before and after LCD in 14 preterm infants, after exclusion of the other 21 infants with AI due to the following causes: death (n=2), early AI (n=5), sepsis (n=1), and patent ductus arteriosus (n=13).

Results:

Fourteen of 257 infants (5.4%) were diagnosed with LCD due to AI. The age at LCD was a median of 18.5 days (range, 9 to 32 days). The last ultrasonographic findings before LCD occurred showed grade 1 periventricular echogenicity (PVE) in all 14 patients and germinal matrix hemorrhage (GMH) with focal cystic change in one patient. Ultrasonographic findings after LCD demonstrated no significant change in grade 1 PVE and no new lesions in eight (57%), grade 1 PVE with newly appearing GMH in three (21%), and increased PVE in three (21%) infants. Five infants (36%) showed new development (n=4) or increased size (n=1) of GMH. Two of three infants (14%) with increased PVE developed cystic periventricular leukomalacia (PVL) and rapid progression to macrocystic encephalomalacia.

Conclusion:

LCD due to AI may be associated with the late development of GMH, increased PVE after LCD, and cystic PVL with rapid progression to macrocystic encephalomalacia.