Update on sudden infant death syndrome

Apneic response to fentanyl in adult rats: Role of laryngeal afferents

Intravenous (systemic) bolus injection of fentanyl (FNT) reportedly induces an immediate vagal-mediated apnea; however, the precise origin of vagal afferents responsible for this apnea remains unknown. We tested whether intralaryngeal (local) application of FNT would also trigger an apnea and whether the apneic response to both local and systemic administration of FNT was laryngeal afferent-mediated. Cardiorespiratory responses to FNT were recorded in anesthetized male adult rats with and without bilateral sectioning of the superior laryngeal nerve (SLNx) or peri-SLN capsaicin treatment (SLNcap) to block local C-fiber signal conduction. Opioid mu-receptor (MOR)-immunoreactivity was detected in laryngeal C- and myelinated neurons. We found that local and systemic administration of FNT elicited an immediate apnea. SLNx, rather than SLNcap, abolished the apneic response to local FNT application though MORs were abundantly expressed in both laryngeal C- and myelinated neurons. Importantly, SLNx failed to affect the apneic response to systemic FNT administration. These results lead to the conclusion that laryngeal afferents' MORs are responsible for the apneic response to local, but not systemic, administration of FNT.

Peripheral Neuroplasticity of Respiratory Chemoreflexes, Induced by Prenatal Nicotinic Exposure: Implication for SIDS

Sudden Infant Death Syndrome (SIDS) occurs during sleep in seemingly healthy infants. Maternal cigarette smoking and hypoxemia during sleep are assumed to be the major causal factors. Depressed hypoxic ventilatory response (dHVR) is observed in infants with high risk of SIDS, and apneas (lethal ventilatory arrest) appear during the fatal episode of SIDS. Disturbance of the respiratory center has been proposed to be involved, but the pathogenesis of SIDS is still not fully understood. Peripherally, the carotid body is critical to generate HVR, and bronchopulmonary and superior laryngeal C-fibers (PCFs and SLCFs) are important for triggering central apneas; however, their roles in the pathogenesis of SIDS have not been explored until recently. There are three lines of recently accumulated evidence to show the disorders of peripheral sensory afferent-mediated respiratory chemoreflexes in rat pups with prenatal nicotinic exposure (a SIDS model) in which acute severe hypoxia leads to dHVR followed by lethal apneas. (1) The carotid body-mediated HVR is suppressed with a reduction of the number and sensitivity of glomus cells. (2) PCF-mediated apneic response is largely prolonged via increased PCF density, pulmonary IL-1β and serotonin (5-hydroxytryptamine, 5-HT) release, along with the enhanced expression of TRPV1, NK₁R, IL1RI and 5-HT₃R in pulmonary C-neurons to strengthen these neural responses to capsaicin, a selective stimulant to C-fibers. (3) SLCF-mediated apnea and capsaicin-induced currents in superior laryngeal C-neurons are augmented by upregulation of TRPV1 expression in these neurons. These results, along with hypoxic sensitization/stimulation of PCFs, gain insight into the mechanisms of prenatal nicotinic exposure-induced peripheral neuroplasticity responsible for dHVR and long-lasting apnea during hypoxia in rat pups. Therefore, in addition to the disturbance in the respiratory center, the disorders of peripheral sensory afferent-mediated chemoreflexes may also be involved in respiratory failure and death denoted in SIDS victims.

Prenatal nicotinic exposure prolongs superior laryngeal C-fiber-mediated apnea and bradycardia through enhancing neuronal TRPV1 expression and excitation

Maternal cigarette smoke, including prenatal nicotinic exposure (PNE), is responsible for sudden infant death syndrome (SIDS). The fatal events of SIDS are characterized by severe bradycardia and life-threatening apneas. Although activation of transient receptor potential vanilloid 1 (TRPV1) of superior laryngeal C fibers (SLCFs) could induce bradycardia and apnea and has been implicated in SIDS pathogenesis, how PNE affects the SLCF-mediated cardiorespiratory responses remains unexplored. Here, we tested the hypothesis that PNE would aggravate the SLCF-mediated apnea and bradycardia via up-regulating TRPV1 expression and excitation of laryngeal C neurons in the nodose/jugular (N/J) ganglia. To this end, we compared the following outcomes between control and PNE rat pups at postnatal days 11-14: 1) the cardiorespiratory responses to intralaryngeal application of capsaicin (10 µg/ml, 50 µl), a selective stimulant for TRPV1 receptors, in anesthetized preparation; 2) immunoreactivity and mRNA of TRPV1 receptors of laryngeal sensory C neurons in the N/J ganglia retrogradely traced by 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate; and 3) TRPV1 currents and electrophysiological characteristics of these neurons by using whole-cell patch-clamp technique in vitro Our results showed that PNE markedly prolonged the apneic response and exacerbated the bradycardic response to intralaryngeal perfusion of capsaicin, which was associated with up-regulation of TRPV1 expression in laryngeal C neurons. In addition, PNE increased the TRPV1 currents, depressed the slow delayed rectifier potassium currents, and increased the resting membrane potential of these neurons. Our results suggest that PNE is capable of aggravating the SLCF-mediated apnea and bradycardia through TRPV1 sensitization and neuronal excitation, which may contribute to the pathogenesis of SIDS.-Gao, X., Zhao, L., Zhuang, J., Zang, N., Xu, F. Prenatal nicotinic exposure prolongs superior laryngeal C-fiber-mediated apnea and bradycardia through enhancing neuronal TRPV1 expression and excitation.

Effects of Framing Health Messages in Terms of Benefits to Loved Ones or Others: An Experimental Study

Many health officials believe the future of public health is in prevention of infectious diseases like pandemic influenza. Vaccine promotion is becoming an increasingly important area for health communication researchers. One strategy health promoters can consider is to emphasize that getting vaccinated protects not only the self, but also loved ones, and unknown others to whom the disease could be spread. The set of experiments described here tested whether such a strategy (called "benefit-target framing") could prove useful in promoting vaccine intentions. In two experiments, subjects from an online panel were randomized to receive a vaccination message focused on the benefits either to the self, to loved ones, or to society as a whole. Outcome measures included intentions to receive the vaccine and intentions to seek more information (n = 495). Results from two virtually identical studies were pooled to maximize power. Results suggest that messages framed in terms of benefits to society were more successful than those focused on the self, but messages focused on loved ones were not different from either of the others. Possible explanations for the findings, and implications for future research, are discussed.

Prevalence of Positional Plagiocephaly in Teens Born after the “Back to Sleep” Campaign

Objectives. To determine the prevalence of positional plagiocephaly and brachycephaly in teenagers born after the “Back to Sleep” campaign but before orthotic helmet treatment became widely available and to provide long-term outcomes data on those children with plagiocephaly who were not treated with remolding therapy.

Study Design. Cross-sectional analysis.

Setting. Local high schools in the Minneapolis–St Paul Metro area.

Subjects and Methods. Subjects were selected if they attended participating high schools and were born after the Back to Sleep campaign began. Skull measurements, including transcranial diameter, length, and width, were taken. Overall facial appearance was inspected for any apparent abnormal characteristics. Cranial vault asymmetry and cephalic index were calculated for each participant. Plagiocephaly was diagnosed if cranial vault asymmetry was >1 cm. Brachycephaly was diagnosed if the cephalic index was >0.90.

Results. There were 1045 participants, ranging from 12 to 17 years old, with an average age of 15.7 years. The prevalence of plagiocephaly was 1.1%. The prevalence of brachycephaly was 1.0%. The overall prevalence of a deformational cranial abnormality was 2.0%. Of those who met diagnostic criteria of plagiocephaly or brachycephaly, 38.1% were noted to have abnormal facial characteristics.

Conclusions. The prevalence of plagiocephaly and brachycephaly in teenagers is significantly lower than the 20% to 48% prevalence found in infants in previous studies, suggesting most children will outgrow the condition without intervention. Additional studies are needed to determine which patients might benefit from treatment and which will likely have resolution without intervention, since treating all infants who meet criteria results in significant overtreatment.

Presentation andSurvival of Prehospital Apparent Sudden Infant Death Syndrome

BACKGROUND

Prehospital providers are often involved in the resuscitation of apparent sudden infant death syndrome (SIDS) victims; however, data are few on the presentation and outcome of these patients.

OBJECTIVES

To describe the presentation and determine the survival rate of infants who have an unwitnessed, prehospital arrest consistent with SIDS (apparent SIDS), and to compare the presentation of infants with a final diagnosis of SIDS with those who presented as apparent SIDS but had a different final diagnosis.

METHODS

This was a secondary analysis of data from a controlled trial whose methodology has been previously described. The setting was two large, urban emergency medical services (EMS) systems of Los Angeles and Orange Counties, California. The population included 113 apparent SIDS victims from the original interventional study who had a prehospital, unwitnessed arrest consistent with SIDS, defined by the scenario of an infant aged =12 months being placed to sleep and later found in full arrest (pulseless and apneic). Data collected included ethnicity, gender, arrest etiology, signs of death (lividity, rigor mortis), prehospital interventions, return of spontaneous circulation (ROSC), arrest rhythm, code 3 transport (lights and sirens), and survival to hospital discharge.

RESULTS

One hundred ten of 113 apparent SIDS patients had survival data; 0 of 110 (95% CI 0% to 3.3%) survived, although ROSC was achieved in 5%; for three patients data on survival were missing. Arrest rhythms were determined in 94% of the subjects: asystole 87%, pulseless electrical activity (PEA) 8%, and ventricular fibrillation 4%. Only 50 of 113 (44%) of the EMS records documented code 3 transport; the remainder of the records were ambiguous. SIDS was the final coroner's diagnosis for 79 of 113 (70%) of the cases. Other causes of death in these apparent SIDS victims included respiratory causes (12%), asphyxiation (3%), abuse (2%), congenital heart disease (2%), sepsis (2%), other (4%), and unknown (5%). Apparent SIDS victims with a final diagnosis of SIDS were more likely to show signs of death (27/79, 34% vs. 5/34, 15%, p = 0.035) and were less likely to have a rhythm of PEA (4/77, 5% vs. 5/31, 16%, p = 0.08), although the latter result was not statistically significant.

CONCLUSIONS

Apparent SIDS victims have a dismal prognosis; all infants presenting with apparent SIDS died, even the 30% whose final diagnosis was not SIDS. Given that there were no survivors, new prehospital policies are needed governing the use of lights and sirens, resuscitation decisions including termination of resuscitation, provision of grief support to families, and incident stress debriefing for prehospital personnel.

Genes regulating the serotonin metabolic pathway in the brain stem and their role in the etiopathogenesis of the sudden infant death syndrome

Genotypes and allelic frequencies of TPH2, 5-HTTLPR, the 5-HTT (SLC6A4) intron 2 variable-number tandem repeat (VNTR) region, and the MAOA VNTR region were determined in brain-stem samples of 20 "genuine" SIDS cases and compared with results obtained from 150 healthy controls. The SNP G1463A responsible for 80% functionality loss of TPH2 (tryptophan hydroxylase 2) was not detected, neither in SIDS infants nor in the controls. In contrast, a strict relation was found between the 5-HTTLPR genotype and its allelic frequencies with SIDS cases. The L/L genotype and the long allele (L) of the promoter region of the serotonin transporter were significantly associated (likelihood ratio (LR) test, p<0.001) with the syndrome (L/L, 60% SIDS vs 14% controls; L, 80% SIDS vs 42.6% controls). Polymorphisms of the intron 2 VNTR of the same gene showed a trend for significant differences between genotypes 10/10 and 12/12 (LR test, p=0.068), with the L-12 haplotype being almost twofold in SIDS (44.5%) with respect to controls (23.4%). Differences were even higher considering the genotype combination L/L-12/12 (20% SIDS vs 2.6%), and variations among categories were statistically highly significant (p<0.001). Although additional differences were observed in the frequency of the MAOA (monoamine oxidase A) VNTR genotype 3R/3R between SIDS and controls (respectively 15% vs 26%), the results were not supported by statistical significance. Molecular polymorphisms are discussed considering their functional role in regulating serotonin synthesis (TPH2), neuronal reuptake (5-HTTLPR and 5-HTT intron 2), and catabolism (MAOA) in the nervous system of Italian SIDS infants. Comparisons are made with previous data obtained in different ethnic groups.

Forensic Lung Pathology

Sudden and unexpected natural deaths and nonnatural deaths may result from various pulmonary conditions. Additionally, several nonpulmonary conditions of forensic significance may be complicated by the development of respiratory lesions. Certain situations with pulmonary pathology are particularly likely to be critically scrutinized and may form the basis of allegations of medical negligence, other personal injury liability, or wrongful death.1

Cardiac potassium channel dysfunction in sudden infant death syndrome

Life-threatening arrhythmias have been suspected as one cause of the sudden infant death syndrome (SIDS), and this hypothesis is supported by the observation that mutations in arrhythmia susceptibility genes occur in 5-10% of cases. However, the functional consequences of cardiac potassium channel gene mutations associated with SIDS and how these alleles might mechanistically predispose to sudden death are unknown. To address these questions, we studied four missense KCNH2 (encoding HERG) variants, one compound KCNH2 genotype, and a missense KCNQ1 mutation all previously identified in Norwegian SIDS cases. Three of the six variants exhibited functional impairments while three were biophysically similar to wild-type channels (KCNH2 variants V279M, R885C, and S1040G). When co-expressed with WT-HERG, R273Q and K897T/R954C generated currents resembling the rapid component of the cardiac delayed rectifier current (I(Kr)) but with significantly diminished amplitude. Action potential modeling demonstrated that this level of functional impairment was sufficient to evoke increased action potential duration and pause-dependent early afterdepolarizations. By contrast, KCNQ1-I274V causes a gain-of-function in I(Ks) characterized by increased current density, faster activation, and slower deactivation leading to accumulation of instantaneous current upon repeated stimulation. Action potential simulations using a Markov model of heterozygous I274V-I(Ks) incorporated into the Luo-Rudy (LRd) ventricular cell model demonstrated marked rate-dependent shortening of action potential duration predicting a short QT phenotype. Our results indicate that certain potassium channel mutations associated with SIDS confer overt functional defects consistent with either LQTS or SQTS, and further emphasize the role of congenital arrhythmia susceptibility in this syndrome.

Preconception care between pregnancies: the content of internatal care

For more than two decades, prenatal care has been a cornerstone of our nation's strategy for improving pregnancy outcomes. In recent years, however, a growing recognition of the limits of prenatal care and the importance of maternal health before pregnancy has drawn increasing attention to preconception and internatal care. Internatal care refers to a package of healthcare and ancillary services provided to a woman and her family from the birth of one child to the birth of her next child. For healthy mothers, internatal care offers an opportunity for wellness promotion between pregnancies. For high-risk mothers, internatal care provides strategies for risk reduction before their next pregnancy. In this paper we begin to define the contents of internatal care. The core components of internatal care consist of risk assessment, health promotion, clinical and psychosocial interventions. We identified several priority areas, such as FINDS (family violence, infections, nutrition, depression, and stress) for risk assessment or BBEEFF (breastfeeding, back-to-sleep, exercise, exposures, family planning and folate) for health promotion. Women with chronic health conditions such as hypertension, diabetes, or weight problems should receive on-going care per clinical guidelines for their evaluation, treatment, and follow-up during the internatal period. For women with prior adverse outcomes such as preterm delivery, we propose an internatal care model based on known etiologic pathways, with the goal of preventing recurrence by addressing these biobehavioral pathways prior to the next pregnancy. We suggest enhancing service integration for women and families, including possibly care coordination and home visitation for selected high-risk women. The primary aim of this paper is to start a dialogue on the content of internatal care.

Co-sleeping, an ancient practice: issues of the past and present, and possibilities for the future

Co-sleeping-infants sharing the mother's sleep space-has prevailed throughout human evolution, and continued over the centuries of western civilization despite controversy and blame of co-sleeping mothers for the deaths of their infants. By the past century, "crib death" was recognized, later identified as Sudden Infant Death Syndrome (SIDS), and generally found to occur more frequently during bed sharing. Pediatricians warned parents of the dangers of SIDS and other risks of bed sharing, and the frequency of bed sharing decreased markedly over the years. However, during recent decades, bed sharing began to increase, though major issues were raised, including: whether bed sharing actually exacerbates or is protective against the occurrence of SIDS, whether the practice facilitates breast feeding, whether bed sharing is beneficial for an infant's development, and other concerns. Dissention may soon be diminished by use of a crib which opens at the mother's bed-side and is becoming a popular approach to mother-and-infant closeness through the night.

Demystifying Sudden Unexplained Death in Epilepsy?Are We Close?

The cause of sudden unexplained death in epilepsy (SUDEP) is still elusive, despite multiple studies over the past few decades. This review assesses recent progress in the understanding of risk factors (situations that predispose patients to SUDEP) and terminal events (events immediately associated with death) that potentially contribute to SUDEP. Recent studies strongly support a close relationship between seizure episodes (especially generalized convulsions) and SUDEP. The lethal nature of some seizure-induced cardiorespiratory events has been documented fortuitously in rare patient cases, and these events have been consistently reproduced in SUDEP animal models. Nonetheless, SUDEP likely does not have a single cause, and risk factors identified thus far may vary in importance among persons with epilepsy. In the absence of a complete understanding of the pathophysiologic mechanisms underlying SUDEP, potential preventive measures for high-risk patients are offered for consideration. Seizure control is most important for reducing SUDEP risk. Circumstantial data suggest that heightened supervision of patients with frequent seizures may be beneficial. Relatively simple interventions may be sufficient to interrupt potentially lethal events such as periictal suffocation or apnea. However, application of these preventive measures to all epilepsy patients has not been proven to substantially reduce the rate of SUDEP. Additional clinical and laboratory investigations are needed to identify and confirm pathogenic factors and preventive measures.

Recent national trends in sudden, unexpected infant deaths: more evidence supporting a change in classification or reporting

The recent US decline in sudden infant death syndrome (SIDS) rates may be explained by a shift in how these deaths are classified or reported. To examine this hypothesis, the authors compared cause-specific mortality rates for SIDS, other sudden, unexpected infant deaths, and cause unknown/unspecified, and they evaluated trends in the age and month of death for these causes using 1989-2001 US linked birth/death certificate data. Reported deaths in state and national data were compared to assess underreporting or overreporting. SIDS rates declined significantly from 1989-1991 to 1995-1998, while deaths reported as cause unknown/unspecified and other sudden, unexpected infant deaths, such as accidental suffocation and strangulation in bed (ASSB), remained stable. From 1999-2001, the decline in SIDS rates was offset by increasing rates of cause unknown/unspecified and ASSB. Changes in the cause-specific age at death and month of death distributions suggest that cases once reported as SIDS are now being reported as ASSB and cause unknown/unspecified. Most of the decline in SIDS rates since 1999 is likely due to increased reporting of cause unknown/unspecified and ASSB. Standardizing data collection at death scenes and improving the reporting of cause of death on death certificates should improve national vital records data and enhance prevention efforts.

Infection and food: a factor in sudden infant death syndrome?

Despite the identification of risk factors for sudden infant death syndrome (SIDS) and decreased SIDS rates in many countries, there is still no coherent, widely accepted, mechanistic explanation for SIDS. As an extension of our work on the infectious aetiology of SIDS, we have explored the prediction that infectious agents might reach susceptible infants and babies, via particular sources of food. In this ecological study, we demonstrated significant correlations between SIDS rates and exposure to meat from some sources, and we propose that more detailed studies be carried out.