Adrenal insufficiency and cardiac dysfunction in the preterm infant

Relative Adrenal Insufficiency in the Preterm Infant

Identifying relative adrenal insufficiency in the critically ill preterm neonate is not always clear-cut. Preterm infants with vasopressor-resistant shock may have persistent cardiovascular insufficiency, which can result in rapid decompensation. After attempts of resuscitation with fluids and inotropes, these infants are often found to respond to glucocorticoids. This raises the important question of how prevalent adrenal insufficiency is in the preterm population. This article reviews the development and role of the adrenal glands, defines relative adrenal insufficiency in the preterm population, discusses barriers to determining this diagnosis, and describes treatment options.

Antenatal Glucocorticoids Reduce the Incidence of Refractory Hypotension in Low Birthweight Infants during the Early Neonatal Period, but Do Not Affect It beyond This Time

OBJECTIVE

This study aimed to clarify the effect of antenatal glucocorticoids (AGs) on the incidence of refractory hypotension (RH) in very low birthweight (VLBW) infants after the first week of life.

STUDY DESIGN

We included VLBW infants born at a gestational age of <30 weeks and divided them into three groups: the complete group (born within 7 days of completing a single course [two doses] of AGs), the incomplete group (born without complete course), and the late delivery group (born at ≥8 days after a single course). We compared the incidence and period of onset of RH among the three groups.

RESULTS

A total of 115 infants were enrolled. The incidence of RH in the first week of life was significantly lower in the complete group than in the other groups. However, there was no significant difference in the incidence of RH after the first week of life among the groups.

CONCLUSION

AGs contribute to circulatory stabilization during the first week of life, but this effect does not last after 1 or 2 weeks of administration. In infants who receive AGs, physicians should consider that the risk of RH after the first week of life is not low.

Postnatal blood pressure in the preterm small for gestational age neonate

OBJECTIVE

Determine how blood pressure differs in premature infants born small for gestational age (SGA).

DESIGN

A retrospective study was conducted on inborn infants 24-32 weeks gestation. Mean arterial blood pressure (MAP) was collected and averaged every 12 h for the first 96 h of life. For each time point, the difference MAP in SGA vs. AGA infants was evaluated with t-testing. Linear mixed-effects modeling was performed to model MAP over time accounting for GA, BW, gender, and SGA status.

RESULTS

356 subjects were evaluated. 52 (14.6%) were SGA. SGA infants were smaller, more likely male, exposed to maternal hypertension, born via caesarian section, and have chronic lung disease and retinopathy of prematurity. MAP in the SGA group more closely matched the MAP of AGA babies of similar GA for the first 24 h of life. Subsequently, SGA infants had lower MAPs more closely resembling their weight-matched counterparts. Mixed modeling showed GA to be significant, p < 0.0001 while BW though still marginally significant had less of an effect, p = 0.049.

CONCLUSION

SGA infants have blood pressure that is strongly associated with GA in the first 24 hours of life, but then fails to increase at the same rate as their AGA counterparts.

The Critical Role of the Central Autonomic Nervous System in Fetal-Neonatal Transition

The objective of this article is to understand the complex role of the central autonomic nervous system in normal and complicated fetal-neonatal transition and how autonomic nervous system dysfunction can lead to brain injury. The central autonomic nervous system supports coordinated fetal transitional cardiovascular, respiratory, and endocrine responses to provide safe transition of the fetus at delivery. Fetal and maternal medical and environmental exposures can disrupt normal maturation of the autonomic nervous system in utero, cause dysfunction, and complicate fetal-neonatal transition. Brain injury may both be caused by autonomic nervous system failure and contribute directly to autonomic nervous system dysfunction in the fetus and newborn. The central autonomic nervous system has multiple roles in supporting transition of the fetus. Future studies should aim to improve real-time monitoring of fetal autonomic nervous system function and in supporting typical autonomic nervous system development even under complicated conditions.

A polymorphism in the glucocorticoid receptor gene is associated with refractory hypotension in premature infants

BACKGROUND

Glucocorticoids play an important role in endocrine control. The association of glucocorticoid receptor (GR) gene polymorphisms with altered sensitivity to glucocorticoid therapy has been reported in adults. However, there are few such reports in infants. The present study analyzed the prevalence of four GR polymorphisms in preterm infants born before 30 weeks of gestation and determined the associations between these polymorphisms and clinical outcomes in the infants.

METHODS

Totally, 41 preterm infants born at two hospitals in Fukushima were retrospectively screened for the presence of four GR gene polymorphisms, using a TaqMan single-nucleotide polymorphism genotyping assay. The effect of GR gene polymorphisms on clinical outcomes during hospitalization was evaluated. The following primary clinical outcomes were assessed: refractory hypotension in the acute phase and/or severe bronchopulmonary dysplasia, maximum dopamine and dobutamine doses administered, and total hydrocortisone dose administered in the first 48 h of life. Multivariate analysis with logistic regression was used to assess the association between clinical factors and refractory hypotension.

RESULTS

Of the four GR polymorphisms, only the BclI polymorphism was detected. The genotype distribution was as follows: C/C, 33; C/G, 8; and G/G, 0 infants. Significant differences were observed between the C/C and C/G genotypes with respect to the following variables: refractory hypotension (6% vs. 50%), dopamine dose [3.0 (2.0-4.0) vs. 4.8 (4.0-7.5) μg/kg/min], dobutamine dose [2.4 (0.0-3.6) vs. 4.0 (0-10.0) μg/kg/min], and total hydrocortisone dose administered in the first 48 h of life [2.0 (0-10.0) vs. 6.0 (0-12.0) mg/kg]. Multivariate analysis showed that the BclI genotype (C/C) was significantly less associated with refractory hypotension in the acute phase (odds ratio, 0.008; 95% confidence interval, 0.000-0.371; p = 0.013).

CONCLUSION

The incidence of refractory hypotension in infants with the C/C genotype was initially expected to be higher than that in infants with the C/G genotype. However, the results of this study were rather different from what we originally expected. The suppressive effect of antenatal steroid use on the HPA axis of the preterm infants with the BclI variant may be associated with refractory hypotension in the acute phase.

Sonographic evaluation of adrenal size in neonates (23 to 41 weeks of gestation)

Background

Fetal adrenal gland size is known to have a positive correlation with both gestational age and estimated body weight. In contrast, some clinical observations suggest that maturation of the adrenal stress response occurs after 30 weeks of gestation. In this study, adrenal gland size at birth in extremely preterm to term neonates was investigated using ultrasonography to evaluate the adrenal developmental pattern and the impact of prematurity and perinatal factors.

Methods

The area of the right adrenal gland was measured in the first 3 h of life in 350 neonates and corrected for birth weight (BW) to determine the corrected adrenal area index (cAI). The neonates were subdivided into three groups: group 1 (before 30 weeks of gestation), group 2 (30 to 36 weeks), and group 3 (after 37 weeks). Differences in the cAI among the 3 groups were compared to estimate the impact of perinatal factors.

Results

The adrenal gland size was measurable in all neonates with gestational age ranging from 23 to 41 weeks. Right adrenal gland area was highly correlated with BW (r = 0.75, p < 0.01). cAI showed a significant negative correlation with gestational age in group 1 (r = − 0.67, p < 0.01), whereas it showed no correlation with gestational age in both groups 2 and 3. As for the impact of perinatal parameters on cAI, only gestational age in group 1 and only fetal distress in group 2 were correlated with cAI. In group 3, perinatal parameters such as fetal distress and low Apgar score were correlated with cAI.

Conclusions

The present study demonstrated that the developmental pattern of fetal adrenal gland was different before and after 30 weeks of gestation, suggesting that the magnitude of adrenal stress response might mature after 30 weeks of gestation.

Should dopamine be the first line inotrope in the treatment of neonatal hypotension? Review of the evidence

AIM: To determine if dopamine is effective in treating neonatal hypotension and safe to use comparing to other inotropes.

METHODS: This is a review of evidence on inotropic treatment of neonatal hypotension. Databases searched were MEDLINE and the Cochrane Library, a total of 134 studies were identified. Only studies with high quality evidence (level 1a and b and 2a) were included. After review, only eight studies were included in the final analysis. Pooled risk ratios derived for each outcome [Mantel-Haenzel (M-H) fixed effect] with CI, as reported in the Cochrane reviews were plotted in forest plot form.

RESULTS: Eight articles met inclusion criteria, which all included treatment in preterm infants. Dopamine increased mean arterial blood pressure (BP) (n = 163; r = 0.88, 95%CI: 0.76 to 0.94) and systolic BP (n = 142; r = 0.81, 95%CI: 0.42 to 0.94) comparing to placebo. Dopamine has been shown overall to be statistically more effective in increasing BP than dobutamine (n = 251, r = 0.26, 95%CI: 0.20-0.32). However there were no differences in short term outcomes (periventricular leucomalacia, periventricular haemorrhage) and mortality between both drugs. There is no statistical evidence of dopamine being more effective than adrenaline or corticosteroids. There was no difference in morbidity and mortality outcomes when dopamine was compared to hydrocortisone (RR 1.81, 95%CI: 0.18 to 18.39) or adrenaline.

CONCLUSION: In preterms, dopamine is the most studied drug, and we suggest it could be used as first line treatment in hypotension.

[Neonatal adrenal hematoma: various modes of presentation]

Neonatal adrenal hematoma is a rare condition, most frequently caused by trauma. We report three cases of adrenal hematoma admitted to the Neonatology and Neonatal Intensive Care Unit in the A. Harouchi Children's Hospital, the Ibn Rushd University Hospital in Casablanca, Morocco, over a 2-year period from January 2011 to December 2012. The average age of these patients was 5 days. The clinical presentations were diverse; the most common manifestations were intense jaundice in one case, acute adrenal insufficiency in one case, and severe anemia in the other case. Abdominal ultrasonography was used to confirm the diagnosis and monitor adrenal hemorrhage in all the patients. Analysis of clinical, laboratory, and ultrasonography data showed a favorable prognosis in all the patients. Based on these observations, we discuss the risk factors, clinical presentations, progression and management of neonatal adrenal hemorrhage.

Corticosteroids for treating hypotension in preterm infants

BACKGROUND

Systemic hypotension is a relatively common complication of preterm birth and is associated with periventricular haemorrhage, periventricular white matter injury and adverse neurodevelopmental outcome. Corticosteroid treatment has been used as an alternative or an adjunct to conventional treatment with volume expansion and vasopressor/inotropic therapy.

OBJECTIVES

To determine the effectiveness and safety of corticosteroids used either as primary treatment of hypotension or for the treatment of refractory hypotension in preterm infants.

SEARCH METHODS

Randomized or quasi-randomised controlled trials were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2011), MEDLINE (1996 to Jan 2011), EMBASE (1974 to Jan 2011), CINAHL (1981 to 2011), reference lists of published papers and abstracts from the Pediatric Academic Societies and the European Society for Pediatric Research meetings published in Pediatric Research (1995 to 2011).

SELECTION CRITERIA

We included all randomised or quasi-randomised controlled trials investigating the effect of corticosteroid therapy in the treatment of hypotension in preterm infants (< 37 weeks gestation) less than 28 days old. Studies using corticosteroids as primary treatment were included as well as studies using corticosteroids in babies with hypotension resistant to inotropes/pressors and volume therapy. We included studies comparing oral/intravenous corticosteroids with placebo, other drugs used for providing cardiovascular support or no therapy in this review.

DATA COLLECTION AND ANALYSIS

Methodological quality of eligible studies was assessed according to the methods used for minimising selection bias, performance bias, attrition bias and detection bias. Studies that evaluated corticosteroids (1) as primary treatment for hypotension or (2) for refractory hypotension unresponsive to prior use of inotropes/pressors and volume therapy, were analysed using separate comparisons. Data were analysed using the standard methods of the Neonatal Review Group using Rev Man 5.1.2. Treatment effect was analysed using relative risk, risk reduction, number needed to treat for categorical outcomes and weighted mean difference for outcomes measured on a continuous scale, with 95% confidence intervals.

MAIN RESULTS

Four studies were included in this review enrolling a total of 123 babies. In one study, persistent hypotension was more common in hydrocortisone treated infants as compared to those who received dopamine as primary treatment for hypotension (RR 8.2, 95% CI 0.47 to 142.6; RD 0.19, 95% CI 0.01 to 0.37). In two studies comparing steroid versus placebo, persistent hypotension (defined as a continuing need for inotrope infusion) was less common in steroid treated infants as compared to controls who received placebo for refractory hypotension (RR 0.35, 95% CI 0.19 to 0.65; RD -0.47, 95% CI - 0.68 to - 0.26; NNT = 2.1, 95% CI 1.47, 3.8). There were no statistically significant effects on any other short or long-term outcome. A further two studies that have only been published in abstract form to date, may be eligible for inclusion in a future update of this review.

AUTHORS' CONCLUSIONS

Hydrocortisone may be as effective as dopamine when used as a primary treatment for hypotension. But the long term safety data on the use of hydrocortisone in this manner is unknown.Steroids are effective in treatment of refractory hypotension in preterm infants without an increase in short term adverse consequences. However, long term safety or benefit data is lacking. With long term benefit or safety data lacking steroids cannot be recommended routinely for the treatment of hypotension in preterm infants.

Adrenal hemorrhage in newborns: a retrospective study

BACKGROUND

Adrenal hemorrhage (AH) is a relatively uncommon condition in neonates. This study aimed to review the clinical, laboratory and ultrasonographic findings of AH in newborns.

METHODS

The medical records of 13 newborns with AH who had been admitted to our neonatal intensive care unit were retrospectively reviewed.

RESULTS

Of the 13 newborns with AH, 8 (62%) were term and 10 (77%) were male babies. Clinical presentations included neonatal jaundice (85%), paleness and/or flank mass (38%), discoloration of the scrotum (15%), and hypotonia/lethargy or hypotension (8%). Five newborns had anemia and four had adrenal insufficiency. Adrenal insufficiency was observed in 80% of the premature infants with AH. AH occurred on the right side in 9 patients (69%). The most predisposing cause of AH was disseminated intravascular coagulation secondary to sepsis or perinatal hypoxia in preterm infants, and large for gestational age in term infants. Ultrasonography (USG) revealed a hypoechoic mass in 7 newborns (54%), a mixed solid-liquid mass in 5 (38%), and an echogenic mass (8%) in 1. Hemorrhage disappeared within 8.6 ± 4.5 (4-16) weeks.

CONCLUSIONS

AH occurs in the newborns with unexplained jaundice. Adrenal insufficiency is more frequent in preterm than in mature infants. Abdominal USG is required to determine AH in a newborn with swelling and bluish discoloration of the scrotum. Serial USG is the best modality for monitoring AH to prevent unnecessary surgery.

Early cortisol values and long-term outcomes in extremely low birth weight infants

OBJECTIVE

Both excess and insufficient levels of glucocorticoid in extremely low birth weight (ELBW) infants have been associated with adverse hospital outcomes, whereas excess glucocorticoid exposure has been associated with long-term adverse neurodevelopment. Our objective was to evaluate the relationship between neonatal cortisol concentrations and long-term outcomes of growth and neurodevelopment.

STUDY DESIGN

As part of a multicenter randomized trial of hydrocortisone treatment for prophylaxis of relative adrenal insufficiency, cortisol concentrations were obtained at 12 to 48 h of postnatal age and at days 5 to 7 on 350 intubated ELBW infants, of whom 252 survived and returned for neurodevelopmental follow-up at 18 to 22 months corrected age. Cortisol values from each time point were divided into quartiles. Growth and neurodevelopmental outcome were compared for each quartile.

RESULT

Median cortisol value was 16.0 microg per 100 ml at baseline for all infants, and 13.1 microg per 100 ml on days 5 to 7 in the placebo group. Outcomes did not differ in each quartile between treatment and placebo groups. Low cortisol values at baseline or at days 5 to 7 were not associated with impaired growth or neurodevelopment at 18 to 22 months corrected age. High cortisol values were associated with an increase in cerebral palsy, related to the increased incidence of severe intraventricular hemorrhage (IVH) and periventricular leukomalacia.

CONCLUSION

Low cortisol concentrations were not predictive of adverse long-term outcomes. High cortisol concentrations, although predictive of short-term adverse outcomes such as IVH and periventricular leukomalacia, did not additionally predict adverse outcome. Further analysis into identifying factors that modulate cortisol concentrations shortly after birth could improve our ability to identify those infants who are most likely to benefit from treatment with hydrocortisone.

Late circulatory dysfunction and decreased cerebral blood flow volume in infants with periventricular leukomalacia

Periventricular leukomalacia is a major neuropathology in preterm infants associated with adverse motor and cognitive outcome. The cerebral blood flow volume of the internal carotid artery and the vertebral artery was measured by ultrasonography at the neck in 36 low-birth-weight infants with gestational age of 25-34 weeks in order to investigate the pathophysiology of cerebral white-matter injury: 30 infants, normal and 6 infants, diagnosed as PVL. The mean blood flow velocity and diameter of each vessel were measured at postnatal days from day 0 to day 70. The intravascular flow volume was determined by calculating the mean blood flow velocity and the cross-sectional area. The mean blood pressures were recorded and PaCO(2) was determined. The total blood flow volume was significantly lower in infants with PVL than in normal infants on days 0, 1, 21, 28, 35, 42, and 63. The mean blood pressure was significantly lower in infants with PVL than in normal infants on days 7, 14, 21, 28, and 42. We suggest that the total cerebral blood supply is decreased in cases of PVL in the few days after birth and from day 21 to day 42. The results of the present study suggest that a dip in the blood flow volume in the few days after birth might result in subsequent PVL.

Corticosteroids for treating hypotension in preterm infants

BACKGROUND

Systemic hypotension is a relatively common complication of preterm birth and is associated with periventricular haemmorhage, periventricular white matter injury and adverse neurodevelopmental outcome. Corticosteroid treatment has been used as an alternative, or an adjunct, to conventional treatment with volume expansion and vasopressor/inotropic therapy.

OBJECTIVES

To determine the effectiveness and safety of corticosteroids used either as primary treatment of hypotension or for the treatment of refractory hypotension in preterm infants.

SEARCH STRATEGY

Randomized or quasi-randomized controlled trials were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2005), MEDLINE (1996 - June 2005), EMBASE (1974 - June 2005), reference lists of published papers and abstracts from the Pediatric Academic Societies and the European Society for Pediatric Research meetings published in Pediatric Research (1995 - 2004).

SELECTION CRITERIA

We included all randomised or quasi-randomised controlled trials investigating the effect of corticosteroid therapy in the treatment of hypotension in preterm infants (< 37 weeks gestation) less than 28 days old. Studies using corticosteroids as primary treatment were included as well as studies using corticosteroids in babies with hypotension resistant to inotropes/pressors and volume therapy. We included studies comparing oral/intravenous corticosteroids with placebo, other drugs used for providing cardiovascular support or no therapy in this review.

DATA COLLECTION AND ANALYSIS

Methodological quality of eligible studies was assessed according to the methods used for minimising selection bias, performance bias, attrition bias and detection bias. Studies that evaluated corticosteroids (1) as primary treatment for hypotension or (2) for refractory hypotension unresponsive to prior use of inotropes/pressors and volume therapy, were analysed using separate comparisons. Data were analysed using the standard methods of the Neonatal Review Group using Rev Man 4.2.7. Treatment effect was analysed using relative risk, risk reduction, number needed to treat for categorical outcomes and weighted mean difference for outcomes measured on a continuous scale, with 95% confidence intervals.

MAIN RESULTS

Two studies were included in this review enrolling a total of 57 babies. In the first study, persistent hypotension was more common in hydrocortisone treated infants as compared to those who received dopamine as primary treatment for hypotension (RR 8.2, 95% CI 0.47 to 142.6; RD 0.19, 95% CI 0.01 to 0.37). In the second study, persistent hypotension (defined as a continuing need for epinephrine infusion) was less common in dexamethasone treated infants as compared to controls who received placebo for refractory hypotension (RR 0.42 , 95% CI 0.17 to 1.06; RD -0.51, 95% CI - 0.91 to - 0.12). There were no statistically significant effects on any other short or long-term outcome. It was not considered appropriate to perform a meta-analysis. A further two studies that have only been published in abstract form to date, may be eligible for inclusion in a future update of this review.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support the routine use of steroids in the treatment of primary or refractory neonatal hypotension. Hydrocortisone may be as effective as dopamine in treating primary hypotension, but there are no data regarding the long-term safety of steroids used for this indication.A single dose of dexamethasone may be effective in treating preterm infants with refractory hypotension receiving epinephrine. However, given the lack of data on long-term safety dexamethasone cannot be recommended for routine use in preterm hypotension.

Management of hypotension and low systemic blood flow in the very low birth weight neonate during the first postnatal week

Systemic hypotension during the first postnatal week is associated with increased mortality and morbidity in the very low birth weight (VLBW) neonate. Hypotension is generally defined as blood pressure below the fifth percentile of the gestational- and postnatal-age dependent blood pressure norms. Recent studies indicate that in most VLBW neonates, cerebral blood flow autoregulation is indeed lost when blood pressure reaches the fifth percentile. Treatment of the circulatory compromise should address the primary pathogenic factor(s) of the condition (hypovolemia, myocardial compromise, failure of vasoregulation or a combination of factors). Recent findings also suggest that vasopressor resistance can be treated with a brief course of low-dose hydrocortisone. However, due to the short- and potential long-term side effects of early hydrocortisone treatment, its use should be restricted to neonates with vasopressor-resistant hypotension. Finally, concomitant administration of hydrocortisone with indomethacin should be avoided due to the increased incidence of gastrointestinal perforations.

Cortisol production rates in preterm infants in relation to growth and illness: a noninvasive prospective study using gas chromatography-mass spectrometry

CONTEXT

Whereas intrauterine growth and maturation depend on low cortisol levels, an adrenal stress response postnatally is thought to be mandatory in preterm infants.

OBJECTIVE

The goal of this study was to determine cortisol production rates (CPRs) in preterm infants during early life with extreme illness and, thereafter, during extrauterine growth and maturation.

DESIGN

We describe a longitudinal observational study.

SETTING

The study was conducted at a university neonatal intensive care unit.

PATIENTS AND METHODS

Seventeen well (27.9 +/- 1.8 wk) and 44 ill (27.3 +/- 1.6 wk) preterm infants were classified by the Score for Neonatal Acute Physiology. Glucocorticoid metabolites were profiled by gas chromatography-mass spectrometry in 24-h urinary samples. Urine was collected noninvasively using cellulose nappies and extracted by hydraulic press.

RESULTS

Medians of CPRs (microg kg(-1) d(-1) mg creatinine) in ill (well) preterm infants were as follows: at d 1, 35 (40); d 2, 35 (40); d 3, 48 (53); d 5, 47 (41); wk 2, 72 (48); wk 3, 73 (37); wk 4, 54 (26). Regression analysis revealed a significant inverse influence of gestational age (P < 0.005) on the maximum of CPRs but not of severity of illness (Score for Neonatal Acute Physiology; P = 0.72). A mature adrenal response was found in only 12 of 44 (27%) ill preterm infants, who had CPRs higher than the 3-fold median of CPRs of well infants. This mature adrenal response was associated with a significantly higher incidence of cerebral bleeding: 9 of 12 (75%) vs. 8 of 32 (25%) without such a response (P = 0.003). During growth, CPRs of ill (well) preterm infants decreased: at month 2, 30 (18); month 3, 18 (22); correlation between weight gain and decrease of CPRs in ill infants between wk 4 and month 3, r = -0.48 (P = 0.027).

CONCLUSIONS

Severity of illness did not have a significant influence on CPRs in preterm infants. However, the highest CPRs were associated with a significantly higher incidence of cerebral bleeding. During growth, CPRs decreased significantly, suggesting that preterm infants have the ability to regulate cortisol production. CPRs in ill preterm infants might reflect inadequate stress reaction, but this could also reveal persistence of fetal protective mechanisms against high catabolic cortisol concentrations.

Diagnosis and treatment of neonatal hypotension outside the transitional period

The etiology and pathophysiology of the circulatory compromise are among the primary determinants of the clinical presentation of patients with neonatal shock. Therefore, in the absence of direct assessment of cardiac output and organ blood flow, the characteristic clinical presentation itself may guide the initial management of the circulatory compromise. This chapter discusses different pathophysiology-driven management approaches to a number of characteristic clinical presentations of neonatal shock. The clinical presentations discussed in detail are the hypotensive very low birth weight neonate with a hemodynamically significant patent ductus arteriosus, and the preterm or term neonate with perinatal depression, pressor/inotrope resistance and relative adrenal insufficiency, and with specific systemic inflammatory response syndrome. In the absence of information from appropriately designed, randomized clinical trials, management of neonatal shock remains based on pathophysiology and experience. Thus, as there is little evidence for the effectiveness of these management approaches to improve mortality and short-and long-term outcome, the therapeutic approaches described in this chapter should be carefully evaluated and cautiously entertained when treating a neonate with circulatory compromise.

Pathophysiology of newborn hypotension outside the transitional period

Hypotension is a common diagnosis in neonatal intensive care units. Although there are epidemiological data for normative blood pressure values in preterm and term infants, the ranges of normal blood pressure where adequate organ perfusion is ensured for different gestational and postnatal ages remain unclear. An understanding of the developmentally regulated differences in the physiology and pathophysiology of the neonatal cardiovascular system in comparison to that of mature subjects is important to formulate an appropriate treatment strategy in neonates with circulatory compromise. This article reviews the current understanding of pathophysiology of hypotension and shock in the neonate beyond the transitional period, focusing on hypovolemia, myocardial dysfunction, abnormal peripheral vasoregulation, and relative or absolute adrenal insufficiency with potentially associated down regulation of adrenergic receptors.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.

Treatment of hypotension in newborns

Systemic hypotension is a common complication of preterm birth affecting approximately one-third of very low-birthweight infants. There is considerable variation between neonatal units in the reported prevalence of hypotension, the threshold for therapeutic intervention and the nature of any cardiovascular support offered. Systemic hypotension is associated with adverse long-term neurodevelopmental outcome. The majority of preterm infants with hypotension have a normal or high left ventricular output, with low systemic vascular resistance often associated with a haemodynamically significant ductal shunt. Historically, volume expansion, dopamine and dobutamine have been the agents most commonly used to treat hypotension. Some hypotensive preterm infants have low cortisol levels, and corticosteroids are being used increasingly to prevent or treat hypotension in these babies.