Cardiovascular effects of hydrocortisone in preterm infants with pressor-resistant hypotension

Glucocorticoid exposure in preterm babies predicts saliva cortisol response to immunization at 4 months

Preterm babies are exposed to multiple stressors and this may have long-term effects. In particular, high levels of endogenous cortisol might have a programming effect on the hypothalamic-pituitary-adrenal axis as may administered glucocorticoids. In this study, we aimed to test the hypothesis that the level of endogenous and exogenous glucocorticoid exposure during the neonatal period predicts the saliva cortisol response to immunization at 4 mo of age. We followed 45 babies born below 32 wk gestation. We showed that their concentration of plasma cortisol during the first 4 wk was 358, 314, 231, and 195 nmol/L cortisol, respectively (geometric mean). This is four to seven times higher than fetal levels at the same gestational age range. We used routine immunization at 4 mo and 12 mo as a stressor and measured the change in saliva cortisol as the stress response. Mean circulating cortisol in the first 4 wk predicted the cortisol response at 4 but not at 12 mo. Path analysis showed that birthweight for gestational age, therapeutic antenatal steroids, and therapeutic postnatal steroids also contributed to the magnitude of the saliva cortisol response at 4 mo. This provides evidence that the magnitude of glucocorticoid exposure, both endogenous and exogenous, may have an effect on later stress responses.

Hemodynamic effects of rescue protocol hydrocortisone in neonates with low cardiac output syndrome after cardiac surgery

OBJECTIVE

To assess the hemodynamic effects and safety of hydrocortisone in neonates with low cardiac output syndrome requiring high levels of inotropic support and fluid resuscitation after cardiac surgery.

DESIGN

Retrospective chart review.

SETTING

Fifteen-bed pediatric cardiovascular intensive care unit.

PATIENTS

Twelve neonates with low cardiac output syndrome after cardiac surgery to whom hydrocortisone was administered according to one of two dosing regimens (100 mg/[m.day] for 2 days, 50 mg/[m.day] for 2 days, and 25 mg/[m.day] for 1 day or 100 mg/[m.day] for 1 day, 50 mg/[m.day] for 2 days, and 25 mg/[m.day] for 2 days) were identified from the Department of Pharmacy database between September 2002 and January 2004.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The mean and systolic blood pressure increased significantly 3 hrs after hydrocortisone treatment from the values preceding hydrocortisone administration. The mean blood pressure increased from 44.0+/-3.0 to 55.4+/-2.3 mm Hg (p=.01) and the systolic blood pressure increased from 64.2+/-4.7 to 78.3+/-3.4 mm Hg (p=.04). Comparable beneficial changes were also seen in the heart rate, which decreased from 168.3+/-4.6 to 148.3+/-5.6 beats/min (p=.004) after 24 hrs of hydrocortisone administration and remained at this level during the 72 hrs of follow-up. Significant weaning of epinephrine infusions was possible, from a mean dose of 0.16 to 0.06 microg/(kg.min) (p=.008), within 24 hrs after the initiation of steroid administration, and this reduction was not offset by increases in other inotropic agents. hydrocortisone administration caused nonsignificant increases in mean blood glucose concentration (from 116.2+/-20.6 to 156.0+/-25.6 mg/dL; p=.64), mean white blood cell count (from 16.6+/-1.6 to 18.9+/-2.6 x 10 U/L; p=.35), and sodium level (from 144.7+/-1.3 to 145.3+/-1.3 mmol/L; p=.51). Ten of the 12 patients (83.3%) survived.

CONCLUSION

Most of the hemodynamically compromised neonates who were unresponsive to high doses of inotropic agents and fluid resuscitation after heart surgery responded to hydrocortisone with improvement of hemodynamic parameters and a decrease in inotropic requirements.

Dexamethasone inhibits maturation and alters function of monocyte-derived dendritic cells from cord blood

Critically ill infants are treated with dexamethasone (Dx) and other glucocorticoids to reduce inflammation and to promote lung and cardiac function. The neonatal immune system is immature, so neonatal dendritic cells (DCs) might be especially sensitive to glucocorticoid-mediated immunosuppression. To test this, we compared Dx treatment of monocyte-derived DCs from cord (CB) and adult blood (AB). Dx decreased CD1a levels on both AB and CB DCs. CB-treated cells also exhibited decreased expression of CD83 and increased expression of CD14, alterations not observed in AB DCs. Characteristic immature endocytic activity was sustained and enhanced in Dx-treated CB DCs, whereas AB DCs matured normally. Maintenance of endocytosis corresponded with CD14 expression. Dx markedly increased CB DC IL-10, a T cell helper 2 (Th2)-preferential cytokine, while reducing IL-12, a counterbalancing Th1 cytokine. AB DCs were also affected, but increases in IL-10 and decreases in IL-12 were more modest. Dx treatment also inhibited DC-induced T cell proliferation, but CB DCs were inhibited more. In short, neonatal DCs seemed to be especially sensitive to the immunosuppressive effects of Dx as indicated by altered phenotype, endocytic function, ability to stimulate T cells, and cytokine shift favoring Th2. These alterations in DC function are consistent with an increased risk for certain infections and atopic diseases.

Cardiovascular support for low birth weight infants and cerebral hemodynamics: a randomized, blinded, clinical trial

BACKGROUND

Maintaining adequate organ blood flow is the target of vasopressor treatment, but the impact of these measures on cerebral perfusion has not yet been evaluated systematically in a randomized, blinded, clinical trial.

OBJECTIVES

To explore the effects on brain hemodynamics of 2 different inotropic agents used to treat systemic hypotension among low birth weight (LBW) infants.

DESIGN AND METHODS

Newborns of <1501 g birth weight or <32 weeks' gestational age, with a mean blood pressure (MBP) lower than gestational age in the first 24 hours of life, were assigned randomly to receive dopamine (DP) (2.5, 5, 7.5, or 10 microg/kg per minute; n = 28) or epinephrine (EP) (0.125, 0.250, 0.375, or 0.5 microg/kg per minute; n = 32), at doses that were increased in a stepwise manner every 20 minutes until the optimal MBP (MBP-OP) was attained and maintained.

OUTCOME MEASURES

Continuous monitoring of quantitative changes in cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, cerebral intravascular oxygenation (HbD) (the difference between oxyhemoglobin and deoxyhemoglobin), and cerebral blood volume (CBV) were assessed with near-infrared spectroscopy. MBP, heart rate, transcutaneous Pco2 and Po2, and peripheral oxygen saturation were recorded continuously and analyzed at baseline, 20 minutes after each dose increase (T1, T2, T3, and T4) until MBP-OP was reached, and then every 20 minutes up to 1 hour of stable MBP-OP.

RESULTS

Fifty-nine infants were considered for analysis. Patients did not differ in birth weight or gestational age (1008 +/- 286 g and 28.3 +/- 2.3 weeks, respectively, in the DP group and 944 +/- 281 g and 27.7 +/- 2.4 weeks in the EP group). Studies were performed at a mean age of 5.3 +/- 3.7 hours of life (range: 2-16 hours). MBP-OP was attained for 96.3% of patients with DP and 93.7% with EP (responders). For those patients, MBP, heart rate, CBV, and HbD increased from baseline throughout the study period, with no differences between groups except for a higher heart rate with EP. Changes in MBP were correlated significantly with changes in HbD. Dose escalation of drugs produced no differences between groups in the behavior of the variables, except for a greater heart rate with EP from 20 minutes after dose 2 (T2) onward. Drug-induced changes in cerebral hemodynamics varied with gestational age; the EP-induced increase in CBV was greater among less mature patients (<28 weeks), whereas the DP-induced increase in CBV was greater among patients of > or =28 weeks.

CONCLUSIONS

Among hypotensive LBW infants, cardiovascular support with low/moderate-dose DP or low-dose EP increased cerebral perfusion, as indicated by the increase in both CBV and HbD. Low-dose EP was as effective as low/moderate-dose DP in increasing MBP among LBW infants.

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.

Diagnosis and treatment of preterm transitional circulatory compromise

AIM

To determine the evidence for detection and treatment of low systemic and organ blood flow in preterm infants in the first day after birth.

REVIEW

Preterm infants are at risk of low systemic blood flow (SBF) in the first day, with almost all infants who develop low flows doing so by 12 h of age. Risk factors for low SBF include low gestational age, ventilation with higher mean airway pressures, large diameter ductus arteriosus, higher calculated systemic vascular resistance and poor myocardial contractility. Blood pressure and clinical signs such as capillary refill times do not accurately detect infants with low SBF, and result in delayed treatment when treatment is targeted at hypotension. Echocardiography in the first hours (including ventricular outputs and superior vena caval flow) is required to detect infants with low flows. Although dobutamine is better at increasing SBF and dopamine better at increasing blood pressure, neither has been shown to improve mortality or longer-term outcomes. Nearly 40% of infants with low SBF fail to respond to inotropes. Volume expansion should not be used routinely in preterm infants. In infants with refractory hypotension, adrenaline and corticosteroids should be considered. Further trials of echocardiographically directed cardiovascular treatments are required.

Morphine, hypotension, and adverse outcomes among preterm neonates: who's to blame? Secondary results from the NEOPAIN trial

OBJECTIVES

Hypotension occurs commonly among preterm neonates, but its cause and consequences remain unclear. Secondary data analyses from the NEOPAIN trial identified the clinical factors associated with hypotension and examined the contributions of morphine treatment or hypotension to severe intraventricular hemorrhage (IVH) (grades 3 and 4), any IVH (grades 1-4), or death.

METHODS

In the NEOPAIN trial, 898 ventilated neonates between 23 and 32 weeks of gestation were enrolled, with equal numbers randomized to receive masked morphine or placebo infusions. Additional doses of open-label morphine were administered as necessary by medical staff members. IVH was diagnosed with centralized readings of early and late cranial ultrasonograms. Hypotension was assessed before study drug infusion, during the loading dose, and at 24 and 72 hours during study drug infusion. Logistic regression analyses with stepdown elimination identified the predictor factors associated with the hypotension, severe IVH, any IVH, or death outcomes at each time point.

RESULTS

Hypotension was associated with 23 to 26 weeks of gestation, morphine infusions, severity of illness, additional morphine doses, and prior hypotension. Severe IVH was associated with shorter gestation, higher Clinical Risk Index for Babies scores, no prenatal steroids, pulmonary hemorrhage, hypotension before the loading dose, and morphine doses before intubation and at 25 to 72 hours. Neonatal deaths were associated with 23 to 26 weeks of gestation, higher Clinical Risk Index for Babies scores, pulmonary hemorrhage, patent ductus arteriosus, thrombocytopenia, and hypotension before the loading dose. Morphine infusions were not a significant factor in logistic models for severe IVH, any IVH, or death.

CONCLUSIONS

Preemptive morphine infusions, additional morphine, and lower gestational age were associated with hypotension among preterm neonates. Severe IVH, any IVH, and death were associated with preexisting hypotension, but morphine therapy did not contribute to these outcomes. Morphine infusions, although they cause hypotension, can be used safely for most preterm neonates but should be used cautiously for 23- to 26-week neonates and those with preexisting hypotension.

Inotrope, lusitrope, and pressor use in neonates

Successful management of neonatal shock is driven by the etiology and pathophysiology of the cardiovascular compromise. In the clinical practice, however, we only have a limited ability to recognize the etiology of the condition (hypovolemia, myocardial dysfunction or abnormal vasoregulation). Therefore, management is based on administration of fluid boluses and vasoactive medications according to personal preference rather than to the underlying pathophysiology. In addition, although management strategies aimed at improving systemic blood pressure may have been associated with a decrease in mortality in critically ill neonates, there are no prospective data on the effect of these management strategies on morbidity, especially on long-term neurodevelopmental outcome. This paper briefly reviews some of the more frequently encountered clinical presentations of neonatal shock and describes the developmentally regulated cardiovascular responses to the pathophysiology-driven management strategies used in these clinical presentations in the critically ill preterm and term neonate.

A randomized-controlled trial of prophylactic hydrocortisone supplementation for the prevention of hypotension in extremely low birth weight infants

OBJECTIVE

Extremely low birth weight (ELBW) infants are at risk for hypotension. Abnormal adrenal function may play a role in the pathogenesis of hypotension, and therefore, the administration of hydrocortisone (HC) may be an effective treatment for hypotension in some infants. However, the efficacy of prophylactic HC to prevent the use of vasopressors for a defined hypotensive state has not been studied. We conducted a randomized-controlled trial to determine the potential role on adrenal insufficiency in early neonatal hypotension and to determine the effectiveness of prophylactic HC in reducing treatment of hypotension in ELBW infants.

STUDY DESIGN

Infants were assigned to receive either HC or placebo within the first 3 hours of life. Therapy was continued for 5 days. The presence of hypotension was based on an operational definition and treatment with vasopressors (VP) was standardized based on an a priori protocol.

RESULTS

A total of 34 patients were enrolled. Baseline characteristics were similar between groups. Of the HC group 25% received VP at 24 hours of age compared to 44% of the placebo group. On day of life 2, only 7% of the HC group received VP compared to 39% of the placebo group (p<0.05).

CONCLUSION

Prophylactic treatment with HC reduces the incidence of hypotension, defined by treatment with VP, among ELBW infants during the first 2 days of life. However, the mounting evidence that prophylactic administration of glucocorticoids in the first days of life is harmful to ELBW infants makes HC prophylaxis unwise until the efficacy of treatment relative to safety can be clearly established.

Prevalence of low cortisol values in term and near-term infants with vasopressor-resistant hypotension

OBJECTIVE

To determine the prevalence of low cortisol values and to evaluate clinical responses to hydrocortisone in ill term and near-term newborns.

STUDY DESIGN

Retrospective cohort study including infants >or=35 weeks gestational age who were mechanically ventilated, received vasopressor therapy, and had a cortisol concentration obtained for evaluation of vasopressor-resistant hypotension. In those infants treated with hydrocortisone, physiologic responses were evaluated and correlated with cortisol values (<15 vs >or=15 microg/dl).

RESULTS

A total of 32 infants had cortisol values obtained; 18 (56%) were <15 microg/dl. In all, 21 infants were treated with hydrocortisone of whom 13 had cortisol values <15 microg/dl. These 13 infants showed decreased heart rate, dopamine support and fluid bolus requirements after treatment, compared to infants with values >or=15 microg/dl (n=8).

CONCLUSIONS

A significant number of hypotensive, mechanically ventilated infants have evidence of inadequate adrenal function. Hydrocortisone therapy resulted in hemodynamic stabilization in this population.

Corticothérapie post-natale chez le prématuré : bénéfices et risques

This review examines the risk/benefit ratio of postnatal steroid treatment in preterm infants and correlates epidemiological data with special emphasis on experimental evidence concening the impact of steroid on brain development. With all regimens, steroid treatment consistently reduced the need for assisted ventilation at 28 days of postnatal age or at term. However, neither oxygen at term nor neonatal mortality has been decreased by this treatment. Conversely, respiratory benefits should be weighed against several adverse effects: hyperglycemia, hypertension, gastrointestinal bleeding or perforation, increased risk of cerebral palsy. The impact of dexamethasone on brain development and risk factors of white matter damage could be involved in the association between postnatal steroid treatment and neurological impairment in treated infants. Injectable preparations of dexamethasone contain sulphiting preservatives which could account for the alterations in neuronal maturation observed in animal models. Early use of dexamethasone should especially be avoided for postnatal steroid treatment in premature infants. Other glucocorticoids as alternatives to dexamethasone need to be evaluated in appropriate and large controlled trials with long term follow up.

Dexamethasone selectively inhibits differentiation of cord blood stem cell derived-dendritic cell (DC) precursors into immature DCs

Perinatal dexamethasone (Dx) alters the immune system leading to increased infections and developmental abnormalities. Dendritic cells (DCs) derived from cord-blood monocytes are especially Dx sensitive and we sought to determine the effects of Dx on cord-blood CD34+-DCs. Distinct stages of cord-blood CD34+-DC development were delineated: pre-DC, immature, and mature DCs. Dx added during development of pre-DCs did not suppress precursor number, or translocate the glucocorticoid receptor (GcR) from the cytoplasm to the nucleus. However, Dx added during pre-DCs differentiation into immature DCs, prompted GcR translocation to the nucleus, enhanced DC apoptosis, suppressed differentiation to CD1a+ cells, inhibited expression of CD86, reduced subsequent CD83 expression, maintained DC endocytic activity, suppressed IL-6 secretion, enhanced IL-10 secretion, and reduced DC-mediated T cell stimulation. Dx added during the maturation stage caused less dramatic effects. Thus, Dx stalled maturation, selectively induced apoptosis of developing DCs and the sensitivity peaked during pre-DCs differentiation into immature DCs.

Evidence for developmental hypopituitarism in ill preterm infants

OBJECTIVE

The relationship between the concentrations of cortisol and T4 with outcome in the preterm infants has not been well studied.

STUDY DESIGN

Mean cortisol (days 2, 4, and 6) and T4 values were correlated to gestational age, illness, and outcome in 210 infants using ANOVA.

RESULTS

Cortisol significantly decreased and T4 increased across gestational age. For both hormones, higher values were found in infants on low ventilatory settings. Combined lower cortisol (mean < 5 microg/dl (138 nmol/l)) and T4 concentrations (<4 microg/dl) were found in 20/210 (9.5%) infants; 11/20 in a high-acuity group (22% of total) including 48% (12/25) of the deaths. Lower cortisol values were found in infants who died (p<0.005) in contrast to a lack of relationship with T4.

CONCLUSIONS

Lower cortisol values in infants who died are consistent with the role for cortisol in survival. Combined lower cortisol and T4 concentrations in infants who failed to improve clinical status may suggest that these hormones are markers of a poor physiological state. In contrast, we suggest that these results reflect a developmental hypopituitarism, a necessary role for cortisone and T4 in successful early neonatal transition. Treatment of hypothyroidism in the setting of coexistent low cortisol concentrations (central dysfunction of the hypothalamic-pituitary axes) is known to precipitate cortisol crisis in older populations. Therefore, we caution against treatment of low neonatal thyroid concentrations until more is known about the relationship between cortisol and T4 preterm infant population.

Postnatal glucocorticoid exposure alters the adult phenotype

We examined the effect of six doses of dexamethasone (Dex) administered daily (2–7 days of age) to postnatal rats on body weight gain, food and water intake, peripheral hormonal/metabolic milieu, and hypothalamic neuropeptides that regulate food intake. We observed a Dex-induced acute (3 days of age) suppression of endogenous corticosterone and an increase in circulating leptin concentrations that were associated with a decrease in body weight in males and females. Followup during the suckling, postsuckling, and adult stages (7–120 days of age) revealed hypoleptinemia in males and females, and hypoinsulinemia, a relative increase in the glucose-to-insulin ratio, and a larger increase in skeletal muscle glucose transporter (GLUT 4) concentrations predominantly in the males, reflective of a catabolic state associated with a persistent decrease in body weight gain. The increase in the glucose-to-insulin ratio and hyperglycemia was associated with an increase in water intake. In addition, the changes in the hormonal/metabolic milieu were associated with an increase in hypothalamic neuropeptide Y content in males and females during the suckling phase, which persisted only in the 120-day-old female with a transient postnatal decline in α-melanocyte-stimulating hormone and corticotropin-releasing factor. This increase in neuropeptide Y (NPY) during the suckling phase in males and females was associated with a subsequent increase in adult food intake that outweighed the demands of body weight gain. In contrast to the adult hypothalamic findings, cerebral ventricular dilatation was more prominent in adult males. We conclude that postnatal Dex treatment causes permanent sex-specific changes in the adult phenotype, setting the stage for future development of diabetes (increased glucose:insulin ratio), obesity (increased NPY and food intake), and neurological impairment (loss of cerebral volume).

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.

Neonatal blood pressure regulation

Hypertension is often viewed solely as a disease of the adult. However, early indicators of hypertension are frequently observed in young children and neonates. Having an adequate appreciation of the normal range of infant blood pressure is critical for the appropriate management of the conditions associated with elevated or abnormally low blood pressure. In healthy neonates, systolic blood pressure increases rapidly during the first 6 weeks of life with the most rapid rise observed during the first 5 days. A similar pattern is observed for diastolic pressures. The observed increases in blood pressure are positively correlated with birth weight and both gestational and postnatal age. The incidence of hypertension in the neonate has been reported to range from 0.2% to 2.6% and is frequently an indicator of other renal or cardiovascular abnormalities. Systemic hypotension is reported in 24% to 45% of very low birth weight infants and is frequently caused by hypovolemia. The regulation of blood pressure is complex and the mechanisms involved remain to be fully elucidated. The results of several investigations into the molecular mechanism(s) of hypertension are considered.

Adrenocortical function and dysfunction in the fetus and neonate

Under normal circumstances, the fetus is exposed to very low concentrations of cortisol until late in gestation. Perturbations of the intra-uterine environment resulting in fetal exposure to increased cortisol may have consequences not only in infancy, but also into adult life. In the postnatal period, developmental immaturity and/or the effects of critical illness on adrenal function may result in insufficient cortisol production to maintain homeostasis in the face of acute stress or illness, a situation that has been labelled 'relative adrenal insufficiency' in other acutely ill populations. The definition of inadequate adrenal function in the newborn and its possible relationship to adverse outcomes in both premature and term infants are only beginning to be characterized.

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.

Hypotension in the very low birthweight infant: the old, the new, and the uncertain

Hypotension occurs in up to 20% of very low birthweight infants, usually in the first 48 hours after birth. Its importance lies in its possible causal link with brain injury. Its management is controversial.

The mismatch between evidence and practice. Common therapies in search of evidence

Many therapies in neonatology persist without supportive evidence: some common therapies may actually be harmful. Evidence-based medicine is the "conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients". The best available evidence, however, is not always sound or valid evidence. Sometimes, when faced with a collection of reports that do not constitute good evidence, attempts to choose the best evidence become pointless; in this case, a statement of no good evidence is preferable. There is a continuing problem with the place of usual practice in the hierarchy of evidence; usual practice generates experience with a particular practice but no reliable information regarding how the practice compares with alternative strategies. Although clinical and institutional inertia combined with a litigious practice environment tend to uphold current practice, the field of neonatology is ripe with examples of established therapies that were subsequently shown to be harmful. It is important to focus on important long-term outcomes and as much on the possibility of harm as on the chance of benefit, especially for new therapies, before they become routine practice. In the face of inadequate evidence, it is particularly important to avoid the temptation to institute treatment guidelines that inhibit further research. Patients are better served by guidelines that recommend only strategies that are supported by strong evidence and recommend further research when the evidence is inadequate.

Metabolic effects of infection and postnatal steroids

Optimal development of the newborn depends on rapid accretion of substrate in the neonatal period, particularly in the premature infant. Steroids and infection not only induce catabolism, but associated endogenous responses reprioritize crucial substrate to restore homeostasis. The result is a protein/energy deficit and concomitant delay in growth and development. Innovative feeding strategies and novel therapies are needed to reduce the impact of catabolism in this population.

Development of the hypothalamic-pituitary-adrenal axis in the fetus and preterm infant

The development of the hypothalamic-pituitary-adrenal (HPA) axis in the human fetus is a complex process. The feto-placental unit may be responsible for important maturational processes in vital organ systems in the fetus. A late gestational cortisol surge may be important in fetal maturation, particularly maturation of the lungs. Several striking differences exist between the function of the HPA axis in the fetus and in adults, such as a relative deficiency of 3beta-hydroxysteroid dehydrogenase in the fetal adrenal cortex. With the transition from intrauterine to extra-uterine life several changes occur in the function of the HPA axis. In infants born before term, the function of the HPA axis may still be immature at both the central and adrenal level. This immaturity of the HPA axis may be important in the development of neonatal morbidity. The present review describes the development of the HPA axis in the fetus and in preterm infants and discusses the possible role of HPA immaturity in the development of neonatal morbidity.

Impaired urinary cortisol excretion and early cardiopulmonary dysfunction in immature baboons

Early adrenal insufficiency is associated with cardiopulmonary dysfunction in immature infants. Isolated cortisol levels and ACTH stimulation testing may not adequately show ontogeny of postnatal cortisol secretion nor identify at risk infants. Our objectives were 1) to determine postnatal urinary cortisol excretion rate (UCER) from birth to 14 d in immature baboons and 2) to evaluate the relation between UCER and cardiac performance. UCER was assessed via 6-h blocked urine collections from birth to 336 h of age in twenty-one 125-d gestation (term = 185 d) baboons. Urinary cortisol was measured by RIA. Cardiopulmonary parameters were averaged over the same time periods as urine collection. Serial two-dimensional echocardiograms were performed. After 24-h age, a subgroup (n = 8) received up to four doses (0.5-1.0 mg/kg each) of hydrocortisone for refractory hypotension. UCER significantly increased from 0 to 6 h through 66 to 72 h age for non-cortisol-treated infants. Significantly reduced UCER patterns between birth and 24 h were found for animals subsequently requiring cortisol treatment. Cortisol-treated infants had lower mean blood pressure, worse metabolic acidosis, increased fluid needs, and impaired left ventricular function between 12 and 48 h of age. No group differences were found in gas exchange or ventilator support. We conclude that adrenal cortisol secretion significantly improves over the initial 72 h of life in the 125-d immature baboon. Failure to increase UCER after 12-24 h of life correlated with poor cardiovascular function that improved with hydrocortisone therapy. Adrenal hypofunction in the immature baboon is similar to the very preterm human and could serve as a model for future postnatal investigations.

The hypothalamic pituitary axis in the fetus and newborn

Glucocorticoid receptor activation in the fetal lung triggers maturation necessary for extra-uterine life. Antenatal treatment with betamethasone and dexamethasone has lowered severity of respiratory distress in very low birth weight infants, and dexamethasone given postnatally has resulted in short-term improvement in chronic lung disease. Recently, however, surfactant therapy has diminished the differential benefit of antenatal glucocorticoid treatment, and it has been difficult to show that postnatal dexamethasone therapy improves survival. Treated infants may have reduced weight gain, adrenal suppression, increased incidence of intestinal perforation and infection, and long-term developmental and metabolic problems. Recent data suggest that the fetal hypothalamic/pituitary/adrenal axis is active early and is precisely structured for an intricate sequence of specifically fetal developmental events, which may be deranged by dexamethasone therapy. We consider data suggesting that persistence of the fetal pattern in some premature infants constitutes adrenal insufficiency, and that therapy at stress replacement doses with less potent glucocorticoids might avoid side effects seen with traditional regimens.