Anesthesiologist and Emergency Medicine Physician Attitudes and Knowledge Regarding Etomidate for Intubation.

PURPOSE: The use of etomidate as an induction agent for critically ill patients is controversial. While its favorable hemodynamic profile is enviable, etomidate has been shown to cause transient adrenal suppression. The clinical consequences of transient adrenal suppression are poorly understood. Anecdotally, some clinicians advocate strongly for etomidate, while others feel it can cause significant harm. To better understand the current clinical environment with respect to single-dose etomidate use in critically ill patients, Canadian anesthesiologists and Canadian emergency medicine (EM) physicians were questioned regarding their opinions, knowledge, and preferences about etomidate use as an induction agent. METHODS: Invitations to participate with the electronic survey were sent to 100 Canadian EM physicians and 260 Canadian anesthesiologists. The survey had 4 general parts: demographics, familiarity with the current literature, choice of induction agent given various clinical scenarios, and opinions on the controversy. The Pearson γ2 test was used to detect whether significant differences exist between physician groups. RESULTS: Ninety three anesthesiologists and 42 EM physicians responded for response rates of 36% and 42%. There were no self-reported differences in knowledge about etomidate properties between EM physicians and anesthesiologists. There were significant differences in etomidate use between EM physicians and anesthesiologists in general rapid sequence intubation, noncritically ill patients, and those with undifferentiated hypotension. Both EM physicians and anesthesiologists describe the current etomidate controversy as significant and not adequately resolved. CONCLUSION: There is no significant difference in self-reported etomidate knowledge between anesthesiologists and EM physicians; however, significant practice pattern differences exist with EM physicians using etomidate more often. Broad agreement supports future research to investigate etomidate's impact in critically ill patients.

How we developed a comprehensive resuscitation-based simulation curriculum in emergency medicine.

Over the past decade, simulation-based education has emerged as a new and exciting adjunct to traditional bedside teaching and learning. Simulation-based education seems particularly relevant to emergency medicine training where residents have to master a very broad skill set, and may not have sufficient real clinical opportunities to achieve competence in each and every skill. In 2006, the Emergency Medicine program at Queen's University set out to enhance our core curriculum by developing and implementing a series of simulation-based teaching sessions with a focus on resuscitative care. The sessions were developed in such as way as to satisfy the four conditions associated with optimum learning and improvement of performance; appropriate difficulty of skill, repetitive practice, motivation, and immediate feedback. The content of the sessions was determined with consideration of the national training requirements set out by the Royal College of Physicians & Surgeons of Canada. Sessions were introduced in a stepwise fashion, starting with a cardiac resuscitation series based on the AHA ACLS guidelines, and leading up to a more advanced resuscitation series as staff became more adept at teaching with simulation, and as residents became more comfortable with this style of learning. The result is a longitudinal resuscitation curriculum that begins with fundamental skills of resuscitation and crisis resource management (CRM) in the first 2 years of residency and progresses through increasingly complex resuscitation cases where senior residents are expected to play a leadership role. This paper documents how we developed, implemented, and evaluated this resuscitation-based simulation curriculum for Emergency Medicine postgraduate trainees, with discussion of some of the challenges encountered.

Renin knockout rat: control of adrenal aldosterone and corticosterone synthesis in vitro and adrenal gene expression.

The classic renin-angiotensin system is partly responsible for controlling aldosterone secretion from the adrenal cortex via the peptide angiotensin II (ANG II). In addition, there is a local adrenocortical renin-angiotensin system that may be involved in the control of aldosterone synthesis in the zona glomerulosa (ZG). To characterize the long-term control of adrenal steroidogenesis, we utilized adrenal glands from renin knockout (KO) rats and compared steroidogenesis in vitro and steroidogenic enzyme expression to wild-type (WT) controls (Dahl S rat). Adrenal capsules (ZG; aldosterone production) and subcapsules [zona reticularis/fasciculata (ZFR); corticosterone production] were separately dispersed and studied in vitro. Plasma renin activity and ANG II concentrations were extremely low in the KO rats. Basal and cAMP-stimulated aldosterone production was significantly reduced in renin KO ZG cells, whereas corticosterone production was not different between WT and KO ZFR cells. As expected, adrenal renin mRNA expression was lower in the renin KO compared with the WT rat. Real-time PCR and immunohistochemical analysis showed a significant decrease in P450aldo (Cyp11b2) mRNA and protein expression in the ZG from the renin KO rat. The reduction in aldosterone synthesis in the ZG of the renin KO adrenal seems to be accounted for by a specific decrease in P450aldo and may be due to the absence of chronic stimulation of the ZG by circulating ANG II or to a reduction in locally released ANG II within the adrenal gland.

Single induction dose of etomidate versus other induction agents for endotracheal intubation in critically ill patients.

BACKGROUND: The use of etomidate for emergency airway interventions in critically ill patients is very common. In one large registry trial, etomidate was the most commonly used agent for this indication. Etomidate is known to suppress adrenal gland function, but it remains unclear whether or not this adrenal gland dysfunction affects mortality. OBJECTIVES: The primary objective was to assess, in populations of critically ill patients, whether a single induction dose of etomidate for emergency airway intervention affects mortality.The secondary objectives were to address, in populations of critically ill patients, whether a single induction dose of etomidate for emergency airway intervention affects adrenal gland function, organ dysfunction, or health services utilization (as measured by intensive care unit (ICU) length of stay (LOS), duration of mechanical ventilation, or vasopressor requirements).We repeated analyses within subgroups defined by the aetiologies of critical illness, timing of adrenal gland function measurement, and the type of comparator drug used. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; CINAHL; EMBASE; LILACS; International Pharmaceutical Abstracts; Web of Science; the Database of Abstracts of Reviews of Effects (DARE); and ISI BIOSIS Citation index(SM) on 8 February 2013. We reran the searches in August 2014. We will deal with any studies of interest when we update the review.We also searched the Scopus database of dissertations and conference proceedings and the US Food and Drug Administration Database. We handsearched major emergency medicine, critical care, and anaesthesiology journals.We handsearched the conference proceedings of major emergency medicine, anaesthesia, and critical care conferences from 1990 to current, and performed a grey literature search of the following: Current Controlled Trials; National Health Service - The National Research Register; ClinicalTrials.gov; NEAR website. SELECTION CRITERIA: We included randomized controlled trials in patients undergoing emergency endotracheal intubation for critical illness, including but not limited to trauma, stroke, myocardial infarction, arrhythmia, septic shock, hypovolaemic or haemorrhagic shock, and undifferentiated shock states. We included single (bolus) dose etomidate for emergency airway intervention compared to any other rapid-acting intravenous bolus single-dose induction agent. DATA COLLECTION AND ANALYSIS: Refinement of our initial search results by title review, and then by abstract review was carried out by three review authors. Full-text review of potential studies was based on their adherence to our inclusion and exclusion criteria. This was decided by three independent review authors. We reported the decisions regarding inclusion and exclusion in accordance with the PRISMA statement.Electronic database searching yielded 1635 potential titles, and our grey literature search yielded an additional 31 potential titles. Duplicate titles were filtered leaving 1395 titles which underwent review of their titles and abstracts by three review authors. Sixty seven titles were judged to be relevant to our review, however only eight met our inclusion criteria and seven were included in our analysis. MAIN RESULTS: We included eight studies in the review and seven in the meta-analysis. Of those seven studies, only two were judged to be at low risk of bias. Overall, no strong evidence exists that etomidate increases mortality in critically ill patients when compared to other bolus dose induction agents (odds ratio (OR) 1.17; 95% confidence interval (CI) 0.86 to 1.60, 6 studies, 772 participants, moderate quality evidence). Due to a large number of participants lost to follow-up, we performed a post hoc sensitivity analysis. This gave a similar result (OR 1.15; 95% CI 0.86 to 1.53). There was evidence that the use of etomidate in critically ill patients was associated with a positive adrenocorticotropic hormone (ACTH) stimulation test, and this difference was more pronounced at between 4 to 6 hours (OR 19.98; 95% CI 3.95 to 101.11) than after 12 hours (OR 2.37; 95% CI 1.61 to 3.47) post-dosing. Etomidate's use in critically ill patients was associated with a small increase in SOFA score, indicating a higher risk of multisystem organ failure (mean difference (MD) 0.70; 95% CI 0.01 to 1.39, 2 studies, 591 participants, high quality evidence), but this difference was not clinically meaningful. Etomidate use did not have an effect on ICU LOS (MD 1.70 days; 95% CI -2.00 to 5.40, 4 studies, 621 participants, moderate quality evidence), hospital LOS (MD 2.41 days; 95% CI -7.08 to 11.91, 3 studies, 152 participants, moderate quality evidence), duration of mechanical ventilation (MD 2.14 days; 95% CI -1.67 to 5.95, 3 studies, 621 participants, moderate quality evidence), or duration of vasopressor use (MD 1.00 day; 95% CI -0.53 to 2.53, 1 study, 469 participants). AUTHORS' CONCLUSIONS: Although we have not found conclusive evidence that etomidate increases mortality or healthcare resource utilization in critically ill patients, it does seem to increase the risk of adrenal gland dysfunction and multi-organ system dysfunction by a small amount. The clinical significance of this finding is unknown. This evidence is judged to be of moderate quality, owing mainly to significant attrition bias in some of the smaller studies, and new research may influence the outcomes of our review. The applicability of these data may be limited by the fact that 42% of the patients in our review were intubated for "being comatose", a population less likely to benefit from the haemodynamic stability inherent in etomidate use, and less at risk from its potential negative downstream effects of adrenal suppression.

Adrenocortical sensitivity to ACTH in neonatal rats: correlation of corticosterone responses and adrenal cAMP content.

A coordinated hypothalamic-pituitary-adrenal axis response is important for the survival of newborns during stress. We have previously shown that prior to postnatal day (PD) 5, neonatal rats exposed to hypoxia (one of the most common stressors effecting premature neonates) exhibit a large corticosterone response with a minimal increase in immunoassayable plasma ACTH and without a detectable increase in adrenal cAMP content (the critical second messenger). To explore the phenomenon of ACTH-stimulated steroidogenesis in the neonate, we investigated the adrenal response to exogenous ACTH in the normoxic neonatal rat. Rat pups at PD2 and PD8 were injected intraperitoneally with porcine ACTH at low, moderate, or high doses (1, 4, or 20 µg/kg body wt). Trunk blood and whole adrenal glands were collected at baseline (before injection) and 15, 30, or 60 min after the injection. ACTH stimulated corticosterone release in PD2 and PD8 pups. In PD2 pups, plasma corticosterone at baseline and during the response to ACTH injection was greater than values measured in PD8 pups, despite lower adrenal cAMP content in PD2 pups. Specifically, the low and moderate physiological ACTH doses produced a large corticosterone response in PD2 pups without a change in adrenal cAMP content. At extremely high, pharmacological levels of plasma ACTH in PD2 pups (exceeding 3,000 pg/ml), an increase in adrenal cAMP was measured. We conclude that physiological increases in plasma ACTH may stimulate adrenal steroidogenesis in PD2 pups through a non-cAMP-mediated pathway.

Effects of age on ACTH, corticosterone, glucose, insulin, and mRNA levels during intermittent hypoxia in the neonatal rat.

Apnea, the temporary cessation of respiratory airflow, is a common cause of intermittent hypoxia (IH) in premature infants. We hypothesized that IH elicits a stress response and alters glucose homeostasis in the neonatal rat. Rat pups were studied on postnatal day (PD) 2, 8, 10, 12, and 14. Pups were exposed to normoxia (control) or six cycles consisting of 30-s exposures to hypoxia (FiO2 = 3%) over a 60-min period. Blood samples were obtained at baseline, after the third cycle (~30 min), and after the sixth cycle (~60 min). Tissue samples were collected following the sixth cycle. Plasma ACTH, corticosterone, glucose, and insulin were analyzed at all ages. Hypothalamic, pituitary, and adrenal mRNA expression was evaluated by quantitative PCR in PD2, PD8, and PD12 pups. Exposure to IH elicited significant increases in plasma ACTH and corticosterone at all ages studied. The largest increase in corticosterone occurred in PD2 pups, despite only a very small increase in plasma ACTH. This ACTH-independent increase in corticosterone in PD2 pups was associated with increases in adrenal Ldlr and Star mRNA expression. Additionally, IH caused hyperglycemia and hyperinsulinemia at all ages. We conclude that IH elicits a significant pituitary-adrenal response and significantly alters glucose homeostasis. Furthermore, the quantitative and qualitative characteristics of these responses depend on developmental age.

Effects of body temperature maintenance on glucose, insulin, and corticosterone responses to acute hypoxia in the neonatal rat.

One of the biggest challenges of premature birth is acute hypoxia. Hypothermia during acute hypoxic periods may be beneficial. We hypothesized that prevention of hypothermia during neonatal hypoxia disrupts glucose homeostasis and places additional metabolic challenges on the neonate. Pups at PD2 and PD8 were exposed to 8% O2 for 3 h, during which they were allowed to either spontaneously cool or were kept isothermic. There was also a time control group that was subjected to normoxia and kept isothermic. Plasma glucose, insulin, C-peptide, corticosterone, and catecholamines were measured from samples collected at baseline, 1 h, 2 h, and 3 h. In postnatal day 2 (PD2) rats, hypoxia alone resulted in no change in plasma glucose by 1 h, an increase by 2 h, and a subsequent decrease below baseline values by 3 h. Hypoxia with isothermia in PD2 rats elicited a large increase in plasma insulin at 1 h. In PD8 rats, hypoxia with isothermia resulted in an initial increase in plasma glucose, but by 3 h, glucose had decreased significantly to below baseline levels. Hypoxia with and without isothermia elicited an increase in plasma corticosterone at both ages and an increase in plasma epinephrine in PD8 rats. We conclude that the insulin response to hypoxia in PD8 rats is associated with an increase in glucose similar to an adult; however, insulin responses to hypoxia in PD2 rats were driven by something other than glucose. Prevention of hypothermia during hypoxia further disrupts glucose homeostasis and increases metabolic challenges.

Adrenocorticotropic hormone and corticosterone responses to acute hypoxia in the neonatal rat: effects of body temperature maintenance.

The corticosterone response to acute hypoxia in neonatal rats develops in the 1st wk of life, with a shift from ACTH independence to ACTH dependence. Acute hypoxia also leads to hypothermia, which may be protective. There is little information about the endocrine effects of body temperature maintenance during periods of neonatal hypoxia. We hypothesized that prevention of hypothermia during neonatal hypoxia would augment the adrenocortical stress response. Rat pups separated from their dams were studied at postnatal days 2 and 8 (PD2 and PD8). In one group of pups, body temperature was allowed to spontaneously decrease during a 30-min prehypoxia period. Pups were then exposed to 8% O(2) for 3 h and allowed to become spontaneously hypothermic or externally warmed (via servo-controlled heat) to maintain isothermia. In another group, external warming was used to maintain isothermia during the prehypoxia period, and then hypoxia with or without isothermia was applied. Plasma ACTH and corticosterone and mRNA expression of genes for upstream proteins involved in the steroidogenic pathway were measured. Maintenance of isothermia during the prehypoxia period increased baseline plasma ACTH at both ages. Hypothermic hypoxia caused an increase in plasma corticosterone; this response was augmented by isothermia at PD2, when the response was ACTH-independent, and at PD8, when the response was ACTH-dependent. In PD8 rats, isothermia also augmented the plasma ACTH response to hypoxia. We conclude that maintenance of isothermia augments the adrenocortical response to acute hypoxia in the neonate. Prevention of hypothermia may increase the stress response during neonatal hypoxia, becoming more pronounced with increased age.

Cardiac and plasma lipid profiles in response to acute hypoxia in neonatal and young adult rats.

BACKGROUND: The physiological and biochemical responses to acute hypoxia have not been fully characterized in neonates. Fatty acids and lipids play an important role in most aspects of cardiac function. METHODS: We performed comprehensive lipid profiling analysis to survey the changes that occur in heart tissue and plasma of neonatal and young adult rats exposed to hypoxia for 2 h, and following 2 h of recovery from hypoxia. RESULTS: Cardiac and plasma concentrations of short-chain acylcarnitines, and most plasma long-chain fatty acids, were decreased in hypoxic neonates. Following recovery from hypoxia, concentrations of propionylcarnitine, palmitoylcarnitine, stearoylcarnitine were increased in neonatal hearts, while oleylcarnitine and linoleylcarnitine concentrations were increased in neonatal plasma. The concentrations of long-chain fatty acids and long-chain acylcarnitines were increased in the hearts and plasma of hypoxic young adult rats; these metabolites returned to baseline values following recovery from hypoxia. CONCLUSION: There are differential effects of acute hypoxia on cardiac and plasma lipid profiles with maturation from the neonate to the young adult rat. Changes to neonatal cardiac and plasma lipid profiles during hypoxia likely allowed for greater metabolic and physiologic flexibility and increased chances for survival. Persistent alterations in the neonatal cardiac lipid profile following recovery from hypoxia may play a role in the development of rhythm disturbances.

Point-of-care ultrasound for the detection of hydronephrosis in emergency department patients with suspected renal colic.

BACKGROUND: Point-of-care ultrasound (PoCUS) by emergency physicians for renal colic has been proposed as an alternative to computed tomography (CT) to avoid ionizing radiation exposure and shorten emergency department length of stay. Previous studies have employed experienced or credentialed ultrasonographers or required advanced ultrasound skills. We sought to measure the diagnostic accuracy of PoCUS by physicians with varied experience using a simplified binary outcome of presence or absence of hydronephrosis. Secondary outcomes include assessment as to whether the presence of hydronephrosis on PoCUS is predictive of complications, and to evaluate possible causes for the reduced diagnostic accuracy such as body mass index (BMI) and time between PoCUS and formal imaging, and scanner experience. RESULTS: 413 patients were enrolled in the study. PoCUS showed a specificity of 71.8% [95% CI 65.0, 77.9] and sensitivity of 77.1% [95% CI 70.9, 82.6]. Hydronephrosis on PoCUS was predictive of complications (relative risk 3.13; [95% CI 1.30, 7.53]). The time interval between PoCUS and formal imaging, BMI, and scanner experience did not influence the accuracy of PoCUS. CONCLUSIONS: PoCUS for hydronephrosis in suspected renal colic has moderate accuracy when performed by providers with varied experience for the binary outcome of presence or absence of hydronephrosis. Hydronephrosis on PoCUS is associated with increased rates of complications. PoCUS for hydronephrosis is limited in its utility as a stand-alone test, however this inexpensive, readily available test may be useful in conjunction with clinical course to determine which patients would benefit from formal imaging or urologic consultation. ClinicalTrials.gov Identifier NCT01323842.

Additive value of nuclear medicine shuntograms to computed tomography for suspected cerebrospinal fluid shunt obstruction in the pediatric emergency department.

OBJECTIVE: To measure the predictive value of nuclear medicine studies (cerebrospinal fluid [CSF] shuntograms) and radiographic studies (computed tomographic [CT] scans) in a cohort of children undergoing evaluation for suspected shunt obstruction in a tertiary care pediatric emergency department (ED). METHODS: A retrospective chart review was conducted on patients younger than 18 years who presented to the pediatric ED of the Children's Hospital of Western Ontario and had both CT of the head and a CSF shuntogram ordered by the attending pediatric emergency medicine physician between December 1998 and April 2003 because of suspected shunt obstruction. RESULTS: A total of 69 patients were evaluated for suspected shunt obstruction in the ED during this period with both a CT and a CSF shuntogram. Twenty-seven patients (39.1%) subsequently required corrective surgery for suspected shunt obstruction that was confirmed intraoperatively. The CT scans showed abnormalities suggestive of CSF shunt obstruction in 21 of the patients who required surgery (sensitivity, 77.8%; negative predictive value, 82.4%), whereas the CSF shuntograms showed abnormalities suggestive of CSF obstruction in 25 of the patients who required surgery (sensitivity, 92.6%; negative predictive value, 92.6%). The CT scans and the shuntograms combined revealed abnormalities suggestive of CSF shunt obstruction in 26 of the 27 patients who required surgery (sensitivity, 96.3%; negative predictive value, 97.4%). CONCLUSIONS: Over one third of pediatric ED patients evaluated with CT and CSF shuntograms required surgical management. Sensitivity was increased with CT and CSF shuntogram compared with CT alone. Prospective studies are required to assess the use of radiographic and nuclear medicine tests for the shunt evaluation in conjunction with the development of a clinical prediction rule for the pediatric emergency physician.

Microarray and real-time PCR analysis of adrenal gland gene expression in the 7-day-old rat: effects of hypoxia from birth.

We hypothesize that changes in adrenal gene expression mediate the increased plasma corticosterone and steroidogenesis in rat pups exposed to hypoxia from birth. In the current study, rat pups (with their dams) were exposed to hypoxia from birth and compared with pups from normoxic dams fed ad libitum or pair fed to match the decreased maternal food intake that occurs during hypoxia. Microarray analysis was performed, followed by verification with real-time PCR. Furthermore, the expression of selected genes involved in adrenal function was analyzed by real-time PCR, regardless of microarray results. Hypoxia increased plasma ACTH and corticosterone, while food restriction had no effect. Microarray revealed that many of the genes affected by hypoxia encode proteins that require molecular oxygen (monooxygenases, oxidoreductases, and electron transport), whereas only a few genes known to be involved in adrenal steroidogenesis were affected. Interestingly, the expression of genes involved in mitochondrial function and intermediary metabolism was increased by hypoxia. Real-time PCR detected a small but significant increase in the expression of Cyp21a1 mRNA in the hypoxic adrenal. When decreased maternal food intake was controlled for, the effects of hypoxia were more pronounced, in that real-time PCR detected significant increases in the expression of Star (244%), Cyp21a1 (208%), and Ldlr (233%). The present study revealed that increased plasma corticosterone in rat pups was due to hypoxia per se, and not as a result of decreased food intake by the hypoxic dam. Furthermore, hypoxia induced changes in gene expression that account for more productive and efficient steroidogenesis.

Plasma leptin and ghrelin in the neonatal rat: interaction of dexamethasone and hypoxia.

Ghrelin, leptin, and endogenous glucocorticoids play a role in appetite regulation, energy balance, and growth. The present study assessed the effects of dexamethasone (DEX) on these hormones, and on ACTH and pituitary proopiomelanocortin (POMC) and corticotropin-releasing hormone receptor-1 (CRHR1) mRNA expression, during a common metabolic stress - neonatal hypoxia. Newborn rats were raised in room air (21% O2) or under normobaric hypoxia (12% O2) from birth to postnatal day (PD) 7. DEX was administered on PD3 (0.5 mg/kg), PD4 (0.25 mg/kg), PD5 (0.125 mg/kg), and PD6 (0.05 mg/kg). Pups were studied on PD7 (24 h after the last dose of DEX). DEX significantly increased plasma leptin and ghrelin in normoxic pups, but only increased ghrelin in hypoxic pups. Hypoxia alone resulted in a small increase in plasma leptin. Plasma corticosterone and pituitary POMC mRNA expression were decreased 24 h following the last dose of DEX, whereas plasma ACTH and pituitary CRHR1 mRNA expression had already increased (normoxia and hypoxia). Hypoxia alone increased corticosterone, but had no effect on ACTH or pituitary POMC and CRHR1 mRNA expression. Neonatal DEX treatment, hypoxia, and the combination of both affect hormones involved in energy homeostasis. Pituitary function in the neonate was quickly restored following DEX-induced suppression of the hypothalamic-pituitary-adrenal axis. The changes in ghrelin, leptin, and corticosterone may be beneficial to the hypoxic neonate through the maintenance of appetite and shifts in intermediary metabolism.

Dexamethasone treatment in the newborn rat: fatty acid profiling of lung, brain, and serum lipids.

Dexamethasone is used as treatment for a variety of neonatal syndromes, including respiratory distress. The present study utilized the power of comprehensive lipid profiling to characterize changes in lipid metabolism in the neonatal lung and brain associated with dexamethasone treatment and also determined the interaction of dexamethasone with hypoxia. A 4-day tapering-dose regimen of dexamethasone was administered at 0800 on postnatal days 3 (0.5 mg/kg), 4 (0.25 mg/kg), 5 (0.125 mg/kg), and 6 (0.05 mg/kg). A subgroup of rats was exposed to hypoxia from birth to 7 days of age. Dexamethasone treatment elicited numerous specific changes in the lipid profile of the normoxic lung, such as increased concentrations of saturated fatty acids in the phosphatidylcholine and cholesterol ester classes. These increases were more profound in the lungs of hypoxic pups. Additional increases in cardiolipin concentrations were also measured in lungs of hypoxic pups treated with dexamethasone. We measured widespread increases in serum lipids after dexamethasone treatment, but the effects were not equivalent between normoxic and hypoxic pups. Dexamethasone treatment in hypoxic pups increased 20:4n6 and 22:6n3 concentrations in the free fatty acid class of the brain. Our results suggest that dexamethasone treatment in neonates elicits specific changes in lung lipid metabolism associated with surfactant production, independent of changes in serum lipids. These findings illustrate the benefits of dexamethasone on lung function but also raise the potential for negative effects due to hyperlipidemia and subtle changes in brain lipid metabolism.

Intermittent neonatal hypoxia elicits the upregulation of inflammatory-related genes in adult male rats through long-lasting programming effects.

The long-term effects of neonatal intermittent hypoxia (IH), an accepted model of apnea-induced hypoxia, are unclear. We have previously shown lasting "programming" effects on the HPA axis in adult rats exposed to neonatal IH. We hypothesized that neonatal rat exposure to IH will subsequently result in a heightened inflammatory state in the adult. Rat pups were exposed to normoxia (control) or six cycles of 5% IH or 10% IH over one hour daily from postnatal day 2-6. Plasma samples from blood obtained at 114 days of age were analyzed by assessing the capacity to induce transcription in a healthy peripheral blood mononuclear cell (PBMC) population and read using a high-density microarray. The analysis of plasma from adult rats previously exposed to neonatal 5% IH versus 10% IH resulted in 2579 significantly regulated genes including increased expression of Cxcl1, Cxcl2, Ccl3, Il1a, and Il1b. We conclude that neonatal exposure to intermittent hypoxia elicits a long-lasting programming effect in the adult resulting in an upregulation of inflammatory-related genes.

Metabolic consequences of hypoxia from birth and dexamethasone treatment in the neonatal rat: comprehensive hepatic lipid and fatty acid profiling.

Neonatal hypoxia is a common condition resulting from pulmonary and/or cardiac dysfunction. Dexamethasone therapy is a common treatment for many causes of neonatal distress, including hypoxia. The present study examined the effects of dexamethasone treatment on both normoxic and hypoxic neonatal rats. We performed comprehensive hepatic fatty acid/lipid profiling and evaluated changes in pertinent plasma hormones and lipids and a functional hepatic correlate, i.e. hepatic lipase activity. Rats were exposed to hypoxia from birth to 7 d of age. A 4-d tapering dose regimen of dexamethasone was administered on: postnatal day (PD)3 (0.5 mg/kg), PD4 (0.25 mg/kg), PD5 (0.125 mg/kg), and PD6 (0.05 mg/kg). The most significant finding was that dexamethasone attenuated nearly all hypoxia-induced changes in hepatic lipid profiles. Hypoxia increased the concentration of hepatic triacylglyceride and free fatty acids and, more specifically, increased a number of fatty acid metabolites within these lipid classes. Administration of dexamethasone blocked these increases. Hypoxia alone increased the plasma concentration of cholesterol and triacylglyceride, had no effect on plasma glucose, and only tended to increase plasma insulin. Dexamethasone administration to hypoxic pups resulted in an additional increase in plasma lipid concentrations, an increase in insulin, and a decrease in plasma glucose. Hypoxia and dexamethasone treatment each decreased total hepatic lipase activity. Normoxic pups treated with dexamethasone displayed increased plasma lipids and insulin. The effects of dexamethasone on hepatic function in the hypoxic neonate are dramatic and have significant implications in the assessment and treatment of metabolic dysfunction in the newborn.

Programming of the hypothalamic-pituitary-adrenal axis by neonatal intermittent hypoxia: effects on adult male ACTH and corticosterone responses are stress specific.

Intermittent hypoxia (IH) is an animal model of apnea-induced hypoxia, a common stressor in the premature neonate. Neonatal stressors may have long-term programming effects in the adult. We hypothesized that neonatal exposure to IH leads to significant changes in basal and stress-induced hypothalamic-pituitary-adrenal (HPA) axis function in the adult male rat. Rat pups were exposed to normoxia (control) or 6 approximately 30-second cycles of IH (5% or 10% inspired O2) daily on postnatal days 2-6. At approximately 100 days of age, we assessed the diurnal rhythm of plasma corticosterone and stress-induced plasma ACTH and corticosterone responses, as well as mRNA expression of pertinent genes within the HPA axis. Basal diurnal rhythm of plasma corticosterone concentrations in the adult rat were not affected by prior exposure to neonatal IH. Adults exposed to 10% IH as neonates exhibited an augmented peak ACTH response and a prolonged corticosterone response to restraint stress; however, HPA axis responses to insulin-induced hypoglycemia were not augmented in adults exposed to neonatal IH. Pituitary Pomc, Crhr1, Nr3c1, Nr3c2, Avpr1b, and Hif1a mRNA expression was decreased in adults exposed to neonatal 10% IH. Expression of pertinent hypothalamic and adrenal mRNAs was not affected by neonatal IH. We conclude that exposure to neonatal 10% IH programs the adult HPA axis to hyperrespond to acute stimuli in a stressor-specific manner.

Adrenocortical control in the neonatal rat: ACTH- and cAMP-independent corticosterone production during hypoxia.

We have previously demonstrated that the neonatal corticosterone response to acute hypoxia shifts from ACTH independence to ACTH dependence between postnatal days two (PD2) and eight (PD8). Cyclic AMP (cAMP) is the obligatory intracellular second messenger of ACTH action, and we hypothesized that corticosterone production in neonatal rats shifts from a cAMP-independent mechanism to cAMP-dependent mechanism between PD2 and PD8. Plasma ACTH and corticosterone and adrenal cAMP and cGMP responses to acute severe hypoxia (8% O2 for 5, 10, 20, 30, and 180 min) were measured in neonatal rats at PD2, PD8, and PD15. Plasma ACTH and corticosterone were measured by radioimmunoassay, and adrenal cAMP and cGMP were measured by ELISA. Plasma corticosterone-binding globulin (CBG) was measured in normoxic pups by ELISA. The largest corticosterone response was observed in PD2 pups, despite only a small increase in plasma ACTH that was not sustained. The PD2 ACTH-independent increase in corticosterone occurred with no change in adrenal cAMP or cGMP content. Plasma CBG concentration was lowest in PD2 pups. Large corticosterone responses were measured during the first 30 min of hypoxia. Differences in corticosterone responses between PD2 and PD8 pups cannot be attributed to changes in plasma protein binding capacity, and the PD2 corticosterone response is consistent with a nongenomic mechanism of action. We conclude that the sustained corticosterone response to hypoxia in PD2 pups occurs with small and transient ACTH responses and independently of increases in adrenal cAMP or cGMP.

Effect of high-dose total body irradiation on ACTH, corticosterone, and catecholamines in the rat.

Total body irradiation (TBI) or partial body irradiation is a distinct risk of accidental, wartime, or terrorist events. Total body irradiation is also used as conditioning therapy before hematopoietic stem cell transplantation. This therapy can result in injury to multiple tissues and might result in death as a result of multiorgan failure. The hypothalamic-pituitary-adrenal (HPA) axis could play a causative role in those injuries, in addition to being activated under conditions of stress. In a rat model of TBI, we have established that radiation nephropathy is a significant lethal complication, which is caused by hypertension and uremia. The current study assessed HPA axis function in rats undergoing TBI. Using a head-shielded model of TBI, we found an enhanced response to corticotropin-releasing hormone (CRH) in vitro in pituitaries from irradiated compared with nonirradiated rats at both 8 and 70 days after 10-Gy single fraction TBI. At 70, but not 8 days, plasma adrenocorticotrophic hormone (ACTH) and corticosterone levels were increased significantly in irradiated compared with nonirradiated rats. Plasma aldosterone was not affected by TBI at either time point, whereas plasma renin activity was decreased in irradiated rats at 8 days. Basal and stimulated adrenal steroid synthesis in vitro was not affected by TBI. In addition, plasma epinephrine was decreased at 70 days after TBI. The hypothalamic expression of CRH messenger RNA (mRNA) and hippocampal expression of glucocorticoid receptor mRNA were unchanged by irradiation. We conclude that the hypertension of radiation nephropathy is not aldosterone or catecholamine-dependent but that there is an abscopal activation of the HPA axis after 10 Gy TBI. This activation was attributable at least partially to enhanced pituitary ACTH production.