Recurrent cyanotic episodes with severe arterial hypoxaemia and intrapulmonary shunting: a mechanism for sudden death

Prominent Intrapulmonary Shunt Vessels and Altered Lung Development in Infants With Sudden Unexplained Infant Death

The purpose of this study was to evaluate intrapulmonary arteriovenous shunts in patients with and without sudden unexplained infant death. We identified open intrapulmonary bronchopulmonary anastomoses as potential pathways for right-to-left shunt in a subset of infants with sudden unexplained infant death.

Does iron therapy have a place in the management of all breath-holding spells?

BACKGROUND

Aim of this study was to analyze the effect of iron therapy in children with breath-holding spells, irrespective of their hemoglobin level.

METHOD

All of the children were evaluated in terms of age, sex, age at onset of the attack, attack frequency, type of breath-holding spell, family pedigree, laboratory values. All enrolled patients were given iron at the dose of 4 mg/kg/day as a single daily dose for 3 months. Patients were called for follow-up appointments 1 and 3 months after the initiation of treatment to record the frequency and severity of spells.

RESULTS

The mean age of the patients was 12.50 ± 9.51 months. Patients were divided into two groups according to the hemoglobin level. The frequency of anemia in children with spells was recorded as 27%. Out of 100 patients treated with iron, 43% showed complete remission at the end of 1 month. At the end of the 3 months, percentage of complete responders increased to 80%. After three-month of iron treatment, 96.2% of the anemic and 73.97% of the non-anemic patients were spell-free. Eight children had mild adverse effects after iron therapy that did not require dose modification.

CONCLUSIONS

This study confirmed that iron therapy reduces spell frequency regardless of anemia in all breath-holding spells. A three-month empiric iron therapy should be offered to all children with spells.

Assessment of both serum S-100B protein and neuropeptide-Y levels in childhood breath-holding spells

OBJECTIVE

Breath-holding spells are common paroxysmal events in children. Although the spells have a benign prognosis in the long term, they may be complicated by loss of consciousness, tonic-clonic movements, and occasionally seizures. Hence, this study aimed to measure the levels of serum S-100B proteins and neuropeptide-Y in the blood of children who experience breath-holding spells.

METHODS

The study groups consisted of 45 patients (13 females, 32 males) with breath-holding spells and a control group of 32 healthy individuals (12 females, 20 males). The serum S-100B levels were measured using commercially available ELISA kits. The neuropeptide-Y levels in the serum were measured with RayBio® Human/Mouse/Rat Neuropeptide Y ELISA kits.

RESULTS

The mean serum S-100B protein level of the breath-holding spells group was 56.38 ± 13.26 pg/mL, and of the control group, 48.53 ± 16.77 pg/mL. The mean neuropeptide-Y level was 62.29 ± 13.89 pg/mL in the breath-holding spells group and 58.24 ± 12.30 pg/mL in the control group. There were significant differences between the groups with respect to serum S-100B protein levels (p = 0.025), while there was no statistically significant difference in neuropeptide-Y levels between the breath-holding spells group and the control group (p = 0.192).

CONCLUSIONS

The findings of this study suggest that frequent and lengthy breath-holding may lead to the development of neuronal metabolic dysfunction or neuronal damage which is most likely related to hypoxia. In light of these findings, future studies should be conducted using biochemical and radiological imaging techniques to support these results.

Laughter is not always funny: breath-holding spells in familial dysautonomia

Familial dysautonomia (FD) is a genetic disease characterized by primary autonomic dysfunction including parasympathetic hypersensitivity. Breath-holding spells (BHS) are believed to be caused by autonomic dysregulation mediated via the vagus nerve and increased in patients with a family history of BHS. Details and understanding of its pathophysiology are lacking. In this retrospective study of patients with FD, the incidence of BHS was higher at 53.3%, compared with previous studies in normal children. Laughter as a precipitating factor for BHS has not been previously reported in FD and occurred in 10% of patients in this study. Lower lung volumes, chronic lung disease, chronic CO2 retention, and inadequate autonomic compensation occur in those with FD leading to a higher incidence and severity of BHS when crying or laughing. Thus, FD may be a good model for understanding manifestations of the autonomic nervous system dysfunction and contribute to our knowledge of BHS mechanisms.

Diverse presentation of breath holding spells: two case reports with literature review

Breath holding spells are a common and dramatic form of syncope and anoxic seizure in infancy. They are usually triggered by an emotional stimuli or minor trauma. Based on the color change, they are classified into 3 types, cyanotic, pallid, and mixed. Pallid breath holding spells result from exaggerated, vagally-mediated cardiac inhibition, whereas the more common, cyanotic breathholding spells are of more complex pathogenesis which is not completely understood. A detailed and accurate history is the mainstay of diagnosis. An EKG should be strongly considered to rule out long QT syndrome. Spontaneous resolution of breath-holding spells is usually seen, without any adverse developmental and intellectual sequelae. Rare cases of status epilepticus, prolonged asystole, and sudden death have been reported. Reassurance and education is the mainstay of therapy. Occasionally, pharmacologic intervention with iron, piracetam; atropine may be of benefit. Here we present 2 cases, one of each, pallid and cyanotic breath holding spells.

Glycopyrrolate and theophylline for the treatment of severe pallid breath-holding spells

Severe pallid breath-holding spells (BHSs) are based on parasympathetic hyperactivity, leading to cardiac asystole, pallor, brain ischemia, loss of consciousness, and reflex anoxic seizures. In recent years, an increasing number of patients with severe pallid BHSs have been successfully treated with pacemaker implantation. We present the case of a 13-month-old girl suffering from repeated severe pallid BHSs, causing asystole, loss of consciousness, and generalized anoxic seizures. She underwent treatment with oral glycopyrrolate, an anticholinergic drug, and an oral retard preparation of theophylline. The aim of the treatment was to decrease cardiac inhibition with glycopyrrolate and to bring about a positive chronotropic effect with theophylline. In our case, the combined therapy was effective in suppressing syncope and reflex anoxic seizures associated with BHSs This avoided the need for ventricular pacemaker implantation.

Sudden death in Lesch-Nyhan disease

To increase awareness of sudden and unexpected death in Lesch-Nyhan disease (LND) and to explore its potential causes, we report the anteceding clinical features and laboratory evaluations of five males with LND who ultimately experienced sudden and unexpected death, along with three additional males who suffered serious respiratory events during life. The ages of patients ranged from 2 to 45 years. The cause of sudden death in LND appears to have a respiratory rather than a cardiogenic basis. All cases cannot be linked readily with a single respiratory process. Instead, different respiratory processes appear to operate in different cases. These may include aspiration, laryngospasm, central apnea, cyanotic breath-holding spells, and high cervical spine damage. Better recognition of these processes will help to guide appropriate workup and management that could include chest imaging, endoscopy of the airways, polysomnography, electroencephalogram, and brain and/or spine imaging.

Pathogenesis of apparent life-threatening events in infants with esophageal atresia

Many infants with a repaired esophageal atresia (EA) undergo fundoplication, aortopexy, or glossopexy because the mechanisms most responsible for airway obstruction and/or apparent life-threatening event (AO/ALTE) syndrome are considered to be gastroesophageal reflux (GER), tracheal compression (TC), or obstructive apnea, respectively. In the present study, we investigated whether these mechanisms are independent or interrelated. We developed a database of 120 consecutive patients with EA treated by the senior author between 1967-2002. We studied the clinical manifestations of patients with a cervical esophagostomy and/or blind lower esophageal stump, which ruled out TC and/or proximal esophageal GER as a mechanism for AO/ALTE. Of 25 neonates who underwent section/ligation of lower tracheo-esophageal fistula and/or feeding gastrostomy, 10 critically ill neonates died. Of 15 survivors, 9 infants had a feeding gastrostomy without an esophagostomy. Of these, 6 infants presented one or more episodes of AO, and 8 presented ALTE with or without AO. Subsequently, 5 of the 9 infants underwent an esophagostomy. Eventually, 11 infants had a feeding gastrostomy with an esophagostomy. Of the latter, 5 infants presented one or more episodes of AO, and 6 presented ALTE without AO. In conclusion, oral feeding, proximal esophageal GER, and TC are not essential for AO/ALTE syndrome to occur. They are probably factors which offer evidence of an underlying problem with control of upper airway patency.

Idiopathic apparent life-threatening event in Northern Israel

OBJECTIVE

To note whether the incidence of idiopathic apparent life-threatening event (IALTE) has decreased since 1993 in parallel to the decline in the incidence of sudden unexpected death in infancy (SUDI) 2. To compare their epidemiological profile to infants with acute unrelated illness.

METHODS

The discharge diagnoses of each infant investigated for apparent life-threatening event or apnea in the five major hospitals in Northern Israel were reviewed over the period 1991-2000. Infants with identified aetiology or apnea only were excluded. Each infant was matched with two other infants admitted for an acute respiratory illness unrelated to apnea. IALTE rates were compared to the national rates of SUDI.

RESULTS

Two hundred and forty-three infants were diagnosed with IALTE. No evidence for a decline in incidence was noted over the period of the study, while a consistent decline in the incidence of SUDI was observed. Only few differences in the epidemiological profile were noted between the study and the comparison group, that is, increased rate of prematurity and first-born infants.

CONCLUSIONS

(i) The two conditions probably do not share a common aetiology in the majority of cases; and (ii) the epidemiological profile of IALTE is predominantly similar to that of infants hospitalized for respiratory illness.

Apparent life-threatening event: a review

An "apparent life-threatening event" (ALTE) refers to an episode that is of concern to the caregiver and is associated with a combination of apnea, color change, change in tone, choking, or gagging. Although the natural history of ALTE is most often benign, there is a risk for subsequent morbidity and mortality. The provider must stabilize the infant as needed, obtain key history, identify and address any underlying causes, educate the caregivers, and provide a safe disposition. This article summarizes the body of literature concerning ALTE, with specific attention to the diagnosis and management of these cases.

Cyanotic breath-holding spell: a life-threatening complication after radical resection of a cervicomedullary ganglioglioma

Cyanotic breath-holding spell is a benign and self-limiting disease of young children but occasionally associated with sudden, unexpected death. The authors report a rare case in a 2-year-old girl with a severe form that started after radical resection of a cervicomedullary ganglioglioma. She was admitted to our hospital because of delayed and unstable gait. Since magnetic resonance imaging showed a cervicomedullary tumor, she underwent a radical resection and histology showed the tumor to be a ganglioglioma. Postoperatively, the function of the lower cranial nerves and cerebellum deteriorated and hemiparesis on the left became apparent, but she returned to the preoperative state in a few months. In addition, mild sleep apnea (Ondine curse) and severe cyanotic breath-holding spells occurred. The former responded to medication but the latter failed and continued several times per day with a rapid onset and progression of hypoxemia, loss of consciousness, sweating and opisthotonos. Five months after the operation, the patient returned home with a portable oxygen saturation monitor equipped with an alarm. This case indicates that cyanotic breath-holding spell, as well as sleep apnea, is critical during the early postoperative period. This is the first report observing that such spells may occur as a complication of radical resection of a cervicomedullary tumor.

Paroxysmal cough injury, vascular rupture and‘shaken baby syndrome’

It is widely assumed that subdural and retinal haemorrhage in infants can only result from traumatic rupture of vulnerable blood vessels. An alternative aetiology, that of vascular rupture resulting from excessive intraluminal pressure, is presented in three disease conditions. (1) Perlman et al., studying premature neonates requiring mechanical ventilation for respiratory distress syndrome, observed "cough-like" fluctuations in oesophageal pressure greater than 18 cms H2O, whose timing matched fluctuations in anterior cerebral artery flow. When 14 out of 24 neonates were paralysed (to prevent abdominal muscle activity) intraventricular haemorrhage developed in all 10 controls but in only one of the paralysed group during paralysis. (2) New analysis of pressure data extracted from a previous study of prolonged expiratory apnoea showed alveolar collapse induced 100 mmHg intrathoracic cough pressure surges. Superior vena cava pressures up to 50 mmHg were implied, and radial artery systolic pressures over 180 mmHg recorded. (3) Bordetella pertussis bacteria attach to cilia in the airways, but do not invade the underlying tissue. The irritation causes the powerful coughing paroxysms of whooping cough. Brain haemorrhages and retinal detachment have been observed to result from the high intravascular pressures produced. The data suggest that any source of intense airway irritation not easily removed (laryngeal infection, inhalation of regurgitated feed, fluff, smoke etc.) could induce similar bleeding, a paroxysmal cough injury (PCI). Additional objective evidence of inflicted trauma is necessary to distinguish between 'shaken baby syndrome' and PCI.

The effects of flight and altitude

Increasing numbers of infants and children journey by aeroplane, or travel to high altitude destinations, for example, on holiday or as part of a population migration. Most are healthy, although increasingly children may be transported by aeroplane or helicopter specifically to obtain treatment for severe illness or injury. It is therefore useful to review the effects of altitude, and their relevance to children who undertake flights or travel to, or at high altitudes, particularly those with acute and chronic medical conditions.

Viruses and sudden infant death

Viral respiratory infections are the most likely trigger for sudden infant death syndrome (SIDS). SIDS cases commonly have evidence of respiratory tract inflammation, a preceding history of symptoms of minor illness and occur in winter peaks coinciding with respiratory viral epidemics. Respiratory infections are a common cause for infants presenting with sudden events, involving apnoea and hypoxaemia and there are physiological mechanisms by which infants may develop sudden and severe, potentially life-threatening hypoxaemia. The rate of SIDS has fallen in the last 15 years. This is probably more to do with the reasons for the fall in deaths from respiratory causes rather than changes in sleeping position. Further falls in SIDS death rates may occur with reductions in cigarette smoking, encouragement of breastfeeding and minimising the potential for young infants to acquire respiratory infections. Early identification and recognition of life-threatening features of infections may further minimise the risks of sudden death.

A pacemaker for asystole in breath-holding spells

Two cases of young children with frequent severe breath-holding spells complicated by prolonged asystole and seizures are reported. A ventricular pacemaker was implanted in each child, and both have subsequently remained free of syncope, although they continue to exhibit breath-holding behaviour.

Apparent life threatening events in infants presenting to an emergency department

OBJECTIVE

To describe the aetiology and outcome of apparent life threatening events (ALTE) presenting to an emergency department (ED), and to assess the value of an initial investigation protocol.

DESIGN

A 12 month prospective study of infants under 1 year of age who presented to a children's hospital ED after an ALTE. A standardised history sheet and initial investigation protocol were used. All infants were admitted to hospital and followed up at six months.

RESULTS

There were 65 infants recruited, median age 7 weeks. None had died at the time of writing. Diagnoses included gastro-oesophageal reflux n=17 (26%), pertussis, n=6 (9%), seizures, n=6 (9%), urinary tract infection (5), factitious illness (2), brain tumour, atrial tachycardia, persistent ductus arteriosus and opioid related apnoea. No diagnosis was reached in 15 cases (23%). Fifty seven (88%) had only one admission to hospital for ALTE. More serious diagnoses were associated with a presentation age over 2 months, abnormal initial clinical examination, and recurrent ALTE.

CONCLUSIONS

ALTEs presenting to the ED may remain as a single, unexplained event or be attributable to numerous causes, ranging from minor to serious. Knowledge of the commoner causes and factors associated with higher risk could result in a more targeted approach, improving the decision making process and benefiting both infants and parents.

Acetazolamide treatment for infantile central sleep apnea

Central sleep apnea is a common respiratory pattern in healthy neonates. Nevertheless, frequent central sleep apnea associated with drops in oxygen saturation may contribute to infantile morbidity. Recently, low-dose acetazolamide was shown to reduce symptomatic central sleep apnea in adults. We treated 12 infants, median conceptional age 42 weeks (range, 40-44 weeks), with central sleep apnea. In all cases, the central apnea index was >40/h total sleeping time (apnea > or = 3 sec). The cumulative duration of drops in oxygen saturation below 90% was more than 3 min/h total sleeping time. All individuals received acetazolamide 7 mg/kg/day (orally, divided in three doses) for 11 weeks. Polysomnography was begun 10 hours before the first dose and continued for 10 hours after the third dose. Polysomnography was repeated after 6 weeks of treatment and 1 week after acetazolamide therapy was discontinued. Comparison of the respiratory patterns before and after treatment (10-hour recording after the third dose) showed a decrease in the median central apnea index from 74/h (range, 42-152/h) to 13/h (range, 6-49/h). The median of the cumulative duration of drops in oxygen saturation below 90% decreased from 3.6 min/h (range, 3.1-9.2 min/h) to 0.07 min/h (range, 0-0.5 min/h). Basal oxygen saturation increased from 95 (92-97%) to 98% (96-99%). This improvement was maintained in the final polysomnography (12 weeks after therapy was begun and 1 week after completion of the 11-week course). No adverse effects were noted. We conclude that low-dose acetazolamide treatment may be useful for the treatment of central infantile sleep apnea associated with hypoxemia.

Rapid eye movement sleep in breath holders

One-night polysomnography was performed on seven subjects suffering from breath-holding spells, including one whose death was suggested to be a consequence of a breath-holding spell. The fatal case showed no rapid eye movements (REMs) during REM sleep, although he exhibited REMs during wakefulness. The average numbers of both REMs and bursts of REMs in REM sleep in the other six breath holders were significantly lower than those in age-matched controls. The breath holders showed no airway obstruction, desaturation, or sleep fragmentation. Since the rapid ocular activity in REM sleep is generated in the brain stem, we hypothesized that a functional brainstem disturbance is involved in the occurrence of breath-holding spells.

Covert video recordings of life-threatening child abuse: lessons for child protection

OBJECTIVE

To describe historic markers and clinical observations of life-threatening child abuse as diagnosed using covert video surveillance (CVS).

DESIGN

A descriptive, retrospective, partially controlled case study.

SETTING

Two hospitals (in London and North Staffordshire, UK) receiving referrals for the investigation of apparent life-threatening events (ALTE), with the availability of CVS.

PATIENTS

A total of 39 children (age range at CVS, 2 to 44 months; median, 9 months) in whom hospital CVS was used to investigate suspicions of induced illness. Thirty-six were referred for investigation of ALTE, one with suspected epilepsy, one with failure to thrive, and one with suspected strangulation. A control group consisted of 46 children with recurrent ALTE proven on physiologic recordings to be attributable to a natural medical cause (9 attributable to epileptic seizures, and 37 attributable to respiratory problems).

INTERVENTION

Collection of historic details from medical, social service, and police records; interagency collaboration in planning, investigations, and management; development and use of CVS as a clinical tool in the investigation of patients in whom there was suspicion of induced illness.

OUTCOME

Confirmation of attempted suffocation or other child abuse from CVS.

RESULTS

CVS revealed abuse in 33 of 39 suspected cases, with documentation of intentional suffocation observed in 30 patients. Poisonings (with disinfectant or anticonvulsant), a deliberate fracture, and other emotional and physical abuse were also identified under surveillance. The first ALTE occurred at a median age corrected for the expected date of delivery of 3.6 months in the CVS patients and of 0.3 months in controls. Three CVS patients and 27 of the control children (including 20 at <32 weeks' gestation) were born prematurely. Bleeding from the nose and/or mouth was reported in 11 of the 38 patients with ALTE undergoing CVS but in none of the 46 controls. Four patients who had been subjected to recurrent suffocation before CVS had permanent neurologic deficits and/or required anticonvulsant therapy for epileptic seizures resulting from hypoxic cerebral injury. The 39 patients undergoing CVS had 41 siblings, 12 of whom had previously died suddenly and unexpectedly. Eleven of the deaths had been classified as sudden infant death syndrome but after CVS, four parents admitted to suffocating eight of these siblings. One additional sibling who had died suddenly with rotavirus gastroenteritis was reinvestigated after CVS of her sister revealed poisoning, and death was found to be caused by deliberate salt poisoning. Other signs of abuse were documented in the medical, social, and police records of an additional 15 of the siblings. In the 52 siblings of the 46 controls, 2 had died: one from hypoplastic left heart at 5 days and the other suddenly and unexpectedly (classified as sudden infant death syndrome) at 7 weeks. Twenty-three of the abusive parents were diagnosed by a psychiatrist as having personality disorders.

CONCLUSIONS

Induced illness is a severe form of abuse that may cause death or permanent neurologic impairment. It may be accompanied by other severe forms of abuse, may result in behavioral disorders, and may be accompanied by immeasurable suffering. Detection of this abuse requires careful history-taking; thorough examination of the health, social, and police records; and close and focused collaboration between hospital and community child health professionals, child psychiatrists, social workers, and police officers. CVS may help investigate suspicions and ensure that children are protected from additional abuse. When parents have failed to acknowledge that they have deceived health professionals, partnership with them in seeking to protect their children may be neither safe nor effective.

Hypoxemic events in spontaneously breathing premature infants: etiologic basis

Studies of severe hypoxemic events, defined as an arterial oxygen saturation < 80% greater than 4 s in spontaneously breathing infants, have been limited. The purpose of our study was to examine the distribution of respiratory events that lead to a fall in oximetrically measured oxygen saturation by using breathing patterns, heart rate, and validated pulse oximetry analysis. A total of 161 hypoxemic events were detected in 18 of 30 premature infants studied. Using an inductive plethysmographic based monitor, a total of 460 h of cardiorespiratory monitor recordings were analyzed. Hypoxemic events were categorized as being the direct result of apnea (duration longer than 15 s) or pauses (duration 4-14 s) with either unchanged or lower end-expiratory lung volumes compared with the preevent breaths. The breaths in the preevent period were analyzed for volume, timing, and thoracoabdominal coordination indices. Forty of the 161 events (25%) were associated with apnea of which 80% (31/40) had a mixed/obstructive basis. Ninety-four of the 161 severe hypoxemic events (58%) were associated with pauses with unchanged end-expiratory lung volume. Twenty-two of the 161 events (14%) showed pauses with lower end-expiratory lung volume. There were 5/161 events (3%) with severe hypoxemia in which no pause was observed. Comparison of the preevent periods in each category showed significant differences for only percent tidal volume from initial calibration and arterial oxygen saturation. Sixty-two percent (100/161) of severe hypoxemic events were preceded by hypopneic values of percent tidal volume. Seventy-five percent (40/161) of these hypoxemic events and their etiology would have gone undetected using respiratory monitoring from impedance pneumograms and ECGs. The varied basis for these events underscores the importance of analyzing detailed respiratory wave forms along with movement-free signal of arterial oxygen saturation and ECG, to formulate appropriate intervention strategies.

Abnormalities in surfactant in sudden infant death syndrome as a postmortem marker and possible test of risk

OBJECTIVE

To determine whether physical abnormalities in lung surfactant, particularly inversion of the hysteresis between surface tension and surface area, are an effective postmortem marker for sudden infant death syndrome (SIDS).

METHODOLOGY

Bronchoalveolar lavage (BAL) was employed to obtain lung rinsings from 55 infants under 24 months of age at autopsy, comprising 34 index cases and 21 controls. Folch reagent was used to extract the lipoid content which was then applied at two surface concentrations, fixed and BAL-determined (BALD), to the pool of a Langmuir trough in which surface tension (gamma) was measured continuously by the Wilhelmy method as surface area (A) was cycled.

RESULTS

The gamma:A loops from SIDS samples were inverted relative to controls (i.e. they were hysteresis reversed, this inversion being quantified by an empirical surface tension: area reversal (STAR) score). There was a wide scatter of STAR scores, but a critical value was found which offered a significant (P = 0.017) separation of SIDS cases from controls for a fixed surface concentration and a highly significant separation (P = 1.0 x 10(-4)) for BALD surface concentrations. Differences in the yields of phospholipid and proteolipid, or their correlation to STAR scores, did not reach statistical significance.

CONCLUSIONS

Inversion of the gamma :A loops (i.e. hysteresis inversion) would appear to offer a better postmortem marker of SIDS than any reported previously, the procedure having potential for development as a prospective test indicating the risk of this disease.

Treatment of apneustic respiratory disturbance with a serotonin-receptor agonist

Apneusis is a disturbance of respiratory rhythm characterized by severely prolonged inspiratory effort. It may occur after damage to the respiratory network within the lower brain stem and pons from an overdose of central nervous system depressants, blockade of glutamate receptors, asphyxia, hypoxia, or ischemia. Experimental studies conducted on laboratory mammals, such as anesthetized cats and rats, suggest that apneusis results mostly from depression of glutamatergic synaptic processes that are necessary for activation of inhibitory mechanisms that terminate inspiration. The impairment of synaptic transmission leads to prolonged inspiratory efforts and apneustic discharges of brainstem respiratory neurons. Apneustic patterns can be consistently converted to normal by administration of serotonin type 1A (5-HT1A) receptor agonists. This observation encouraged a treatment of severe apneusis with buspirone, an agonist for 5-HT1A receptors, in a child after neurosurgery for an astrocytoma in the pons and medulla oblongata. Oral administration of buspirone produced a prompt and highly effective remission of apneusis without side effects. Treatment with 5-HT1A agonists, therefore, might offer a novel and effective pharmacotherapy against apneustic disturbances of breathing.

Recurrent apparent life-threatening event relieved by glossopexy

An infant with repaired esophageal atresia presented with several apparent life-threatening events (ALTEs). He had upper airway instability, gastroesophageal reflux (GER), and tracheomalacia. Oxygen breathing test results showed a modest increase in arterial Po2 consistent with the development of an intrapulmonary shunt from absorption collapse of some hypoventilated areas of the lung. Glossopexy was followed by improvement in upper airway stability, normal oxygen test, and disappearance of ALTE. These findings support the concept that upper airway instability, obstructive apnea, lower airway instability, absorption collapse, massive intrapulmonary shunt, and ALTE are the result of a cascade reaction. The authors conclude that infants with ALTE associated with obstructive apnea and O2 shunting require glossopexy to reduce the risk of sudden death.

Home monitoring of infants at increased risk of sudden death

Home apnoea and cardiorespiratory monitors are commonly used in the UK, the rest of Europe and USA in infants at increased risk of 'sudden infant death'. The efficacy of apnoea and cardiorespiratory monitors remains unknown. The use of transcutaneous oxygen monitoring is presented as an alternative method of home monitoring. Recommendations are proposed regarding nursing practice and the future of home monitoring in infants at increased risk of sudden death.

Respiratory responses to rapid-onset, repetitive vs. continuous hypoxia in piglets

Repeated, frequent hypoxic exposures may precede Sudden Infant Death. This study assessed whether such hypoxic modality, vs. continuous hypoxia, compromised compensatory cardiorespiratory responses. Following aseptic, chronic instrumentation, 10 to 20 day-old, unsedated piglets underwent measurements of arterial O2 saturation, pH and gas tensions, respiration, heart rate, physical activity, O2 consumption and rectal temperature on several experimental days. The piglets were exposed to 21 min of either 10% or 6% O2 in N2, each comprising either seven, 3-min exposures alternating with 3-min intervals in 21% O2 balance N2, or 7 consecutive hypoxic exposures. Responses to 6% hypoxia were greater than those to 10% hypoxia. In 10% hypoxia, responses to repetitive vs. continuous exposure differed only in PaCO2. In 6% hypoxia, repetitive vs. continuous exposure resulted in lower respiratory frequency (p < 0.05) and in lower ventilation equivalent (p = 0.07) despite higher activity levels. Thus, the mode of hypoxic exposure determines the extent of the respiratory response: Severe, repetitive hypoxia mitigates protective respiratory responses when compared to equivalent, but sustained hypoxia.

Temporal relationship between pauses in nasal airflow and desaturation in preterm infants

Physiological recordings were undertaken to study the temporal relationship between apnea, defined as pauses in nasal airflow (PNA), and desaturation in preterm infants. Seventeen infants with a history of apnea of prematurity were studied on 21 occasions. Median (range) birthweight was 1,180 g (575-2,475) and gestation was 30 weeks (26-33). Median age at time of study was 10 days (range, 2-52). Arterial beat to beat oxygen saturation (SaO(2)), photoplethysmographic waveform, electrocardiogram, abdominal and ribcage breathing movements, and nasal airflow were recorded. Falls in SaO(2) > or = 3% occurring during or after a PNA > or = 4 seconds were recorded. Episodes of periodic breathing were excluded from this analysis. Four hundred and sixteen episodes of PNA and desaturation were analyzed. Application of a definition of "outliers" for non-parametric data suggested an association when the desaturation occurred up to 7.20 seconds after the end of the PNA for infants nursed in air. For infants on oxygen treatment, a temporal association was suggested when desaturation occurred up to 9.76 seconds after the end of PNA.

Breath-holding spells

Two particularly common, and frequently frightening, forms of syncope and anoxic seizure in early childhood are pallid and cyanotic breath-holding spells. Pallid breath-holding spells result from exuberant vagally-mediated cardiac inhibition. Cyanotic breath-holding spells are of more complex pathogenesis, involving an interplay among hyperventilation, Valsalva maneuver, expiratory apnea, and intrinsic pulmonary mechanisms. The history is the mainstay of diagnosis; videotape documentation may be possible. Performance of an electrocardiogram to evaluate for prolonged QT syndrome should be strongly considered. In patients with pallid breath-holding spells, a characteristic sequence of changes may be documented on an electroencephalogram with ocular compression, if this study is performed. Spontaneous resolution of breath-holding spell, without sequelae, is anticipated. Reassurance is the mainstay of therapy. Occasionally, pharmacologic intervention may be of benefit.

Pulmonary Neuroendocrine Cells and Lung Development

Pulmonary neuroendocrine cells produce bioactive peptides such as gastrin-releasing peptide (GRP) at high levels in developing fetal lung. The role of GRP and other peptides in promoting branching morphogenesis, cell proliferation, and cell differentiation during lung organogenesis is reviewed. Possible roles for bioactive peptides derived from these cells in the pathophysiology of perinatal lung disorders are discussed.

Mechanisms for episodes of hypoxemia in preterm infants undergoing mechanical ventilation

OBJECTIVE

To ascertain possible mechanisms implicated in the development of transient episodes of hypoxemia (oxygen saturation < 85%) frequently observed in preterm infants undergoing mechanical ventilation, even after the acute phase of respiratory failure has passed.

STUDY DESIGN

Tidal flow, airway and esophageal pressure, and oxygen saturation were continuously recorded in 10 infants (mean +/- SD, birth weight 733 +/- 149 gm, gestational age 25.5 +/- 2.2 weeks, age 26.3 +/- 11.9 days) who had repeated episodes of hypoxemia without any evident cause. Measurements of minute ventilation (VE) inspiratory compliance (Ci), and inspiratory resistance (Ri) were compared before and during episodes of hypoxemia.

RESULTS

All episodes of hypoxemia were preceded by an active exhalation that produced a mean decrease in end-expiratory lung volume of 6.4 +/- 2.8 ml/kg. The reduction in lung volume was immediately followed by a sudden decrease in tidal flow and volume, despite continuation of mechanical ventilation at the same rate and peak pressure. The resulting hypoventilation was associated with a drop in Ci to approximately one half and an increase in Ri to more than double the baseline values. Approximately 30 seconds after the beginning of hypoventilation, the arterial oxygen saturation reached a hypoxemic level (oxygen saturation < 85%)>

CONCLUSION

Most hypoxemic episodes were triggered by an expiratory effort that produced a large decrease in lung volume. This reduction in lung volume probably leads to closure of small airways and the development of intrapulmonary shunts, which would explain the rapid development of hypoxemia.

A novel role for surfactant in the lung with implications for the sudden infant death syndrome

Feedback from mechanoreceptors in the lungs to the brainstem has long been known to be vital for control of rhythmogenesis during normal breathing. Action potentials transmitted via the vagi are shown to display an irreversible relationship with respect to lung area (A), i.e. hysteresis, which closely resembles the hysteresis in surface tension (gamma) versus A for normal surfactant which coats that surface. Since lung recoil is largely determined by surface tension for resting tidal volumes, this will dominate the stretch of mechanoreceptors. Hence, it is postulated that, through the Hering-Breuer reflex, surfactant largely determines afferent neural feedback, explaining the above similarity in clockwise hysteresis loops. Thus the ability of normal surfactant to impart normal clockwise gamma: A hysteresis is seen as a desirable property enabling the brainstem to differentiate between the inspiratory and expiratory phases of the breathing cycle at the same lung volume. It is further hypothesized that the very abnormal surfactant found recently in some infants with prolonged expiratory apnoea by displaying anti-clockwise gamma: A loops would render afferent neural feedback to the brainstem highly confusing and could cause prolonged expiratory apnoea. This concept is discussed as a possible cause of sleep apnoea, recurrent cyanotic episodes and the Sudden Infant Death Syndrome (SIDS).

Apparent life-threatening event: a neurologic perspective

Of 46 infants who were investigated for apparent life-threatening events, central nervous system disorders were diagnosed in seven (15%). Convulsive disorders, intraventricular hemorrhage and hydrocephalus, absent corpus callosum, and development deficits were found. In four of the seven, no neurologic deficit was suspected before the event. Electroencephalographic studies (overnight in two) would have identified the disorder in all four. Electroencephalography is therefore a recommended routine procedure in investigation of apparent life-threatening events. Central nervous system disorders should be routinely ruled out in cases of apparent life-threatening event, even in the absence of clinical clues.

Surfactant abnormalities in ALTE and SIDS

Abnormalities in the relative concentrations of the components of surfactant have been implicated in prolonged expiratory apnoea (PEA) and sudden infant death syndrome (SIDS). Controversy has, however, surrounded these findings, as they may be secondary to terminal life events. In this study the physical properties of surfactant were measured in children with recurrent apparent life threatening events (ALTEs), PEA, and SIDS. Bronchial lavage samples were obtained from 21 children with recurrent ALTEs, two SIDS victims, and 26 control patients. Lipid components were immediately elutriated from these samples with liquid chloroform. The physical properties of the extracted surfactant were studied on a Langmuir trough in which the area (A) of the monolayer was cycled continuously as the surface tension (gamma) was measured by the Wilhelmy method using a platinum 'flag'. The investigators performing these tests were unaware of the clinical diagnosis. Twenty one of 23 patients displayed abnormal physical properties while seven of 26 controls displayed similar abnormalities. These abnormalities were partially inverted hysteresis (figure of eight) loops and inverted (anticlockwise) loops that also generally exhibited less hysteresis. Of the 26 controls 20 exhibited a wide hysteresis pattern that cycled in a normal (clockwise) direction. These differences were significantly different. It is concluded that children with recurrent ALTEs have definable abnormalities in the physical properties of surfactant and that these findings may provide a sensitive means of identifying those at risk of recurrent ALTEs and SIDS.

Abnormal hypoxemia after life-threatening events in infants born before term

This study aimed to determine whether preterm infants who have a history of apparent life-threatening events (ALTE) have abnormalities in oxygenation and, if so, whether the ALTE would stop with oxygen therapy. We assessed 92 patients (median gestational age at birth, 32 weeks (range, 24 to 36 weeks); median birth weight, 1840 gm (650 to 3500 gm)) who had had a single (n = 20) or recurrent ALTE. Median postnatal age at referral was 3.2 months (0.5 to 44.7 months). All had been considered otherwise free of symptoms and adequately oxygenated in air at the time of discharge from their neonatal unit, before the ALTE. Fifty-two patients had received mouth-to-mouth resuscitation, and 40 vigorous stimulation. Ninety-one patients underwent 8- to 12-hour recordings of arterial oxygen saturation, the plethysmographic waveforms from the oximeter, breathing movements, and electrocardiograms. These recordings were compared with previously published data from 110 "healthy" preterm infants made at around 6 weeks after discharge from hospital. Compared with these data, 49 recordings (54%) were normal, 19 showed abnormal hypoxemic episodes, 6 had abnormally low baseline arterial oxygen saturation (< 95%), and 17 had both. In 31 of 33 patients, ALTE stopped or were reduced in frequency or severity after additional inspired oxygen (0.1 to 1.0 L/min via nasal cannulas) was given. Oxygen was given for a median duration of 3.9 months (range, 0.8 to 17.2 months). Persistent events in the remaining two patients were subsequently found to be due to intentional suffocation in one and epileptic seizures in the other. Monitoring of transcutaneous oxygen tension at home was undertaken in 84 patients. To date, this has been discontinued in 81 after a median duration of 7.3 months (0.3 to 18.9 months). We conclude that recognition and treatment of abnormalities in episodic or baseline hypoxemia may reduce the risk of further ALTE in previously preterm infants.

Inverse relationship between beta-endorphin immunoreactivity in cerebrospinal fluid and nucleus tractus solitarius in sudden infant death

In nucleus tractus solitarius (NTS) beta-endorphin (BEND) induces bradycardia and respiratory depression which have been reported to precede death in sudden infant death (SID). Of SID victims, 50% have elevated levels of beta-endorphin immunoreactivity (BENDI) in the cerebrospinal fluid (CSF), and 50% had undetectable levels. We therefore investigated the relationship of BENDI in the CSF to BENDI levels in the NTS area. This study included SID victims (CSF from n = 47, brain stem from n = 16), borderline SID victims (CSF and brain stem from n = 2), sudden death in childhood (CSF and brain stem from n = 1), and controls (CSF from n = 32, brain stem from n = 11). BEND in CSF and NTS area, after extraction, was measured by radioimmunoassay. High performance liquid chromatography was used for closer identification of BENDI. We found that the SID victims divided into two subpopulations, one having a relatively high BENDI level in CSF and one having no detectable level (P < 0.01). Furthermore, an inverse relationship was found between BENDI level in CSF and BENDI level in NTS area in the SID victims (P < 0.05). We conclude that increased BENDI level in CSF is associated with low BENDI level in the NTS area in 50% of SID victims. The low BENDI level in the NTS area may be due to increased release of BEND.

Why is there an increased risk for sudden infant death in prone sleeping? Fear paralysis and atrial stretch reflexes implicated?

A number of recent reports have indicated a higher risk of sudden infant death syndrome (SIDS) in the prone sleeping position, compared with the supine position. However, the biological mechanisms for this increased risk have not been established. For this report, two biological explanations are proposed, each of which may be influenced by altered sleeping position in such a way that they may create conditions for increased triggering of SIDS.

Pathophysiology and treatment of bronchopulmonary dysplasia. Current issues

Although much has been learned about BPD in the 25 years since its initial description, BPD remains a significant complication of prematurity. Substantial advances into the understanding of its pathophysiology and pathogenesis have been made and are reflected in new therapeutic interventions. Much current research is directed towards the role of prevention, exploring new approaches for accelerating lung maturation with combined maternal steroid and thyrotropin releasing hormone (TRH) therapy, surfactant replacement therapy, high frequency oscillatory ventilation, antioxidant administration, manipulation of endogenous antioxidants, and other pharmacologic strategies to minimize lung injury. The impact of other technologies, such as synchronized intermittent mandatory ventilation, perfluorocarbon (liquid) ventilation, and perhaps inhaled nitric oxide therapy may become additional parts of the clinical regimen for some cases of severe neonatal respiratory failure. Less information is available on mechanisms which can hasten lung healing. Ongoing studies of inflammatory products, growth factors, and cytokines may lead to new therapies which will favorably influence the fibroproliferative phase of disease. In the meantime, the medical and social impact of BPD continues to remain a significant problem not only during infancy but also throughout life. Mildred Stahlman, MD, recently wrote that (a)s sanguine as the future looks for surfactant therapy, it may leave us with more very low-birth weight infants who survive, whose potential for normal pulmonary growth and development is unknown, and whose very immature organ systems, besides the lung, are still susceptible to metabolic, neurologic, and other problems. As more survivors are reaching young adulthood, respiratory and neurodevelopmental complications persist. Thus, as advances in the care of the premature newborn with respiratory distress have dramatically improved survival, the management of chronic lung disease and related problems remains a continuing challenge.

Elevated beta-endorphin immunoreactivity in the cerebrospinal fluid in victims of sudden infant death correlates with hypoxanthine in vitreous humour

Beta-endorphin (BEND) may induce respiratory depression. Elevated levels of beta-endorphin immunoreactivity (BENDI) in the CSF are found in children with apnoea and in about 50% of sudden infant death (SID) victims. Premortal hypoxia in SID victims has been indicated by elevated hypoxanthine (HX) levels in the vitreous humour (VH). In this study we correlated BENDI in CSF with HX in VH in SID victims (n = 19) and controls (n = 18). BEND in CSF was measured by RIA, and HPLC was used for identification of BENDI. HX in VH was measured by HPLC. All the SID victims had elevated levels of HX in VH. The BENDI in CSF divided the SID victims into two subpopulations (P < 0.01); one with undetectable levels (< 4.3 fmol/ml) (n = 10) and one with high levels (160-400 fmol/ml) (n = 9). In the SID subpopulation with high levels of BENDI in CSF, we found a correlation between BENDI in CSF and HX in VH (r = 0.92). Control infants who died a stressful death, such as during heart operations (n = 2), had high levels of BENDI in CSF and low levels of HX in VH. Controls who died of infections (n = 11) had low levels of BENDI in CSF and elevated levels of HX in VH. Because hypoxia in itself does not increase BENDI in CSF, increased BENDI in CSF is probably not secondary to hypoxia but may be of aetiological significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic nervous system function in severe breath-holding spells

This study attempted to determine noninvasively whether a dysregulation of autonomic nervous system reflexes exists in children with severe cyanotic breath-holding spells (BHS). This was a cross-sectional study performed in the neurophysiology laboratory at a tertiary care hospital. Patients, 18 months of age and older taken from a referral population of children with severe cyanotic BHS and normal controls, were studied. Fourteen children with cyanotic BHS and 12 controls were evaluated. Several noninvasive measures of parasympathetic and sympathetic reflex functions were assessed and statistically analyzed using analysis of variance and covariance, and Fisher's exact tests. The cyanotic BHS group had a significantly greater increase in pulse rate at 15 s of standing after rising from the supine position (P < .06), with a trend toward a concomitant higher mean arterial pressure (P < .09). After adjusting for age, sex, and mean supine systolic and diastolic blood pressures, breath-holders had a greater decrease in diastolic blood pressure (P < .02) without an increase in systolic blood pressure after standing from the supine position. Breath-holders also had significantly abnormal 30:15 R-R interval ratios compared with controls (P < .002). These results support the hypothesis that children with cyanotic BHS have underlying autonomic nervous system dysregulation. This dysregulation may contribute to the pathophysiology of severe BHS in these children.

Pulmonary artery pressure changes in the very low birthweight infant developing chronic lung disease

Pulmonary artery pressure may be estimated non-invasively in the premature newborn infant because of its negative correlation with the time to peak velocity:right ventricular ejection time (TPV:RVET) ratio calculated from the pulmonary artery Doppler waveform. We studied 54 very low birthweight infants on days 1, 2, 3, 7, 14, 21, and 28 after birth. Thirty four infants developed chronic lung disease (CLD). Twenty did not and acted as controls. After correcting the TPV:RVET ratio for heart rate (TPV:RVET(c)), during the first 14 days the TPV:RVET(c) ratio rose progressively in both groups suggesting a fall in pulmonary artery pressure. This occurred at a significantly slower rate in the CLD group. From days 14 to 28 there was a significant fall in the ratio in the CLD group only, suggesting an increase in pulmonary artery pressure. Using CLD as the end point, a TPV:RVET(c) ratio < 0.54 on day 7 had a predictive value of 78% (sensitivity 73%, specificity 65%). This rose to a predictive value of 97% (sensitivity 88%, specificity 95%) on day 28. The non-invasive assessment of pulmonary artery pressure may be useful in the early clinical management of the very low birthweight infant at risk of developing CLD.

Abnormal pulmonary bombesin immunoreactive cells in Wilson-Mikity syndrome (pulmonary dysmaturity) and bronchopulmonary dysplasia

Wilson-Mikity syndrome (WMS) is a disorder of uncertain origin. It is sometimes considered a variant of bronchopulmonary dysplasia (BPD), but it lacks the characteristic microscopic stigmata of destruction and fibrosis caused by the barotrauma and oxygen toxicity of ventilator support. Conventional clinical and autopsy studies of WMS have failed to identify the underlying pathophysiology. This study evaluated bombesin-containing pulmonary neuroendocrine (PNE) cells in eight WMS cases, seven cases of BPD, and five controls, using the immunoperoxidase technique. The PNE cells were quantified by established morphometric techniques. The percentage of airways containing PNE cells in WMS (mean, 85.56%) was similar to that in the controls (mean, 82.6%) but significantly greater than that in BPD (mean, 21.28%) (p < .001). Measurement of intraepithelial PNE cell cytoplasm within the bombesin-immunopositive airways demonstrated apparent PNE cell hyperplasia in both WMS and BPD. Prominent numbers of PNE cells were also present in the respiratory bronchioles and alveolar units in WMS. The increased PNE cells in WMS may reflect chronic hypoxia from hypoventilation and or autonomic dysfunction. The profile in BPD may reflect a similar pathophysiology but complicated by ventilator-induced injury to airway epithelium.

Diagnosis and management after life threatening events in infants and young children who received cardiopulmonary resuscitation

OBJECTIVE

To determine the mechanisms and thereby appropriate management for apparent life threatening events treated with cardiopulmonary resuscitation in infants and young children.

DESIGN

Prospective clinical and physiological study.

SETTING

Royal Brompton Hospital or in patients' homes, or both.

SUBJECTS

157 Patients referred at median age 2.8 months (range 1 week to 96 months), 111 (71%) had recurrent events, 44 were born preterm, 19 were siblings of infants who had died suddenly and unexpectedly, and 18 were over 12 months old.

INTERVENTIONS

Multichannel physiological recordings, including oxygenation, in hospital (n = 150) and at home (n = 61). Additional recordings with electroencephalogram, video, or other respiratory measures were used to confirm diagnoses. Management involved monitoring of oxygen at home, additional inspired oxygen, anticonvulsant treatment, or child protection procedures.

MAIN OUTCOME MEASURES

Abnormalities on recordings compared to published normal data and their correlation with clinical events; sudden death.

RESULTS

53 of 150 patients had abnormalities of oxygenation on hospital recordings, 28 of whom had an accompanying clinical event. Home recordings produced physiological data from 34 of 61 patients during subsequent clinical events. Final diagnoses were reached in 77 patients: deliberate suffocation by a parent (18), hypoxaemia induced by epileptic seizure (10), fabricated history and data (Munchausen syndrome by proxy; seven), acute hypoxaemia of probable respiratory origin (40), and changes in peripheral perfusion and skin colour without hypoxaemia (two). Four patients died: three suddenly and unexpectedly (none on home oxygen monitors) and one from pneumonia.

CONCLUSIONS

Identification of mechanisms is essential to the appropriate management of infants with apparent life threatening events.

Oxygen saturation and breathing patterns in preterm infants with cyanotic episodes

The pathophysiology of cyanotic/apnoeic episodes in preterm infants was investigated using overnight tape recordings of beat-to-beat arterial oxygen saturation (SaO2), plethysmographic waveforms from the oximeter, breathing movements and nasal airflow. Recordings were made in 16 preterm infants with recurrent cyanotic episodes of unknown cause that had received stimulation or resuscitation, and 15 preterm controls, matched for birth weight, post-conceptional and postnatal age. The recordings were analysed for baseline SaO2, the number of hypoxaemic episodes (SaO2 < or = 80% for > or = 4 s) and the breathing patterns associated with each episode. There was a significant difference in the total number of hypoxaemic episodes between patients and controls (520 versus 100; p < 0.01), but no difference was found for mean baseline SaO2 (98.6 versus 99.0%; p > 0.05). The mean duration of each hypoxaemic episode in the patients was 9.5 s compared with 5.8 s in the controls (p < 0.01). Although most hypoxaemic episodes (62 and 76%) were associated with pauses in breathing movements, a proportion (8 and 18%, respectively) occurred despite continuous airflow and breathing movements in both patients (6 of 16) and preterm controls (2 of 15). The rate of decrease in SaO2 was significantly more rapid during these latter hypoxaemic episodes than during episodes associated with isolated apnoeic pauses (8.5 versus 3.2% per second, p = 0.02). Preterm infants with cyanotic episodes have increased numbers of clinically unapparent hypoxaemic episodes, some of which have continued ventilation and rapid desaturation. The pathogenesis of these episodes warrants further investigation.