Sudden infant death syndrome in infants of substance-abusing mothers

Perinatal and neonatal issues of substance abuse

Substance abuse during pregnancy can be teratogenic for the fetus and can cause decreased growth parameters in the newborn infant. Short-term and long-term neurobehavioral problems have been documented also in babies born to substance-abusing mothers. The problem of substance abuse during pregnancy and its effects on the fetus is unique in medicine in that it is 100% preventable. Physicians will need to take an active role in leading society to take action in preventing substance abuse during pregnancy, and emphasis on this action should occur long before the woman becomes pregnant. Until medical schools and residency programs take responsibility for teaching the importance of preventing substance abuse and of identifying the substance-abuser, drug and alcohol use will continue to exact its tragic toll on future generations.

Cocaine babies: a result of multiple teratogenic influences

The history of cocaine use is reviewed. Cocaine teratogenesis has only recently been studied, and initial human studies had serious methodological flaws. These flaws included ascertainment bias, publication bias (studies finding cocaine effects have been more likely to be presented or published), and overemphasis on the perinatal period. Comparison with alcohol teratogenesis shows that alcohol is a more potent teratogen, which, however, produces major and specific effects (fetal alcohol syndrome) in less than 10% of offspring with heavy alcohol exposure during pregnancy. Nonspecific minor congenital anomalies or fetal alcohol effects are seen in a larger number. Personal experience with two groups of children exposed to cocaine in utero is reviewed. Insurance patients gained weight, took vitamins, and generally, their children did well in spite of cocaine use. Indigent patients were usually unmarried and often "street people," probably used more cocaine, generally used other drugs as well, often did not gain weight during pregnancy, and were much more likely to have children with problems. Surveys show that most cocaine users also use alcohol, often simultaneously. Those who use both agents are more likely to have troubled backgrounds and antisocial behavior and to drop out of treatment programs than those who use only alcohol. Cocaethylene or ethylbenzoylecgonine is formed in the liver when cocaine and alcohol are simultaneously ingested. It is a potent stimulant and dopamine uptake blocker that is more toxic to myocardial cells than is cocaine. Good nutrition is now known to be very important in preventing congenital anomalies and fetal death. A multihit model of neurologic handicap, which stresses the importance of a good postnatal environment, is briefly outlined.(ABSTRACT TRUNCATED AT 250 WORDS)

Prenatal cocaine exposure alters postnatal hypoxic arousal responses and hypercarbic ventilatory responses but not pneumocardiograms in prenatally cocaine-exposed term infants

To test the hypothesis that respiratory control is altered in cocaine-exposed infants, we evaluated the hypoxic arousal response and the ventilatory response to carbon dioxide (CO2) in 18 term newborn infants prenatally exposed to cocaine and in 10 healthy, term newborn infants within the first week of life. Three infants could not be tested for the hypoxic arousal response because of low baseline oxygen saturation, and data from these infants were excluded from analysis. Twelve hour overnight pneumocardiograms were performed on all infants. Results show that 60% (9/15) of the prenatally cocaine-exposed infants had an abnormal hypoxic arousal response and 87% (13/15) had abnormal hypercarbic ventilatory response. Only 6% (1/15) of the prenatally cocaine-exposed infants demonstrated any abnormality on pneumocardiogram. In contrast, all control infants (10/10) were aroused by the hypoxic challenge and 80% (8/10) had normal ventilatory response to CO2. No abnormalities were found in the assessment of the overnight pneumocardiogram in the control infants. For the cocaine-exposed infants, test abnormalities were not correlated with a concurrent positive urine toxicology for cocaine, suggesting that the injury occurs early in development. These findings support the hypothesis that infants prenatally exposed to cocaine demonstrate abnormalities of respiratory control.

Methadone treatment during pregnancy

Methadone maintenance has been used for decades to treat opioid-dependent pregnant women. The outcomes of pregnancies thus treated are vastly improved over the outcomes of pregnancies complicated by street drug use. Despite its long history of successful use during pregnancy, little is known about the long-term effects of methadone on the fetus and the newborn. Studies done in animals suggest there may be subtle effects on brain and behavior. Only recently have other treatments for opioid dependency during pregnancy been investigated. There is increasing evidence that altering the traditional methadone maintenance protocols may be beneficial, and that tapered withdrawal can be safely achieved under some circumstances.

Hypoxia after prenatal cocaine attenuates striatal dopamine and neurotrophic activity

We have previously shown that newborn rabbits exposed to cocaine prenatally have an altered cardiorespiratory response to hypoxia. We report the effect of postnatal hypoxia on brain DA and neurotrophic activity in New Zealand White rabbit pups (n = 41) born to cocaine-exposed does (30 mg/kg/day SC from days 7-15 of a 32-day gestation = COCaine) and control does (sterile H2O = VEHicle). Four to 6-day-old pups were exposed to 20 min of room air (0.21 fractional inspired oxygen tension, FIO2). One third of each group was then exposed to 20 min of either 0.15 (moderate hypoxia) or 0.08 (severe hypoxia) FIO2. Immediately following hypoxic challenge the pups were sacrificed. Striatal tissue extracts were subsequently assessed for DA and striatal trophic activity by monitoring the number of neuron specific enolase immunoreactive (NSEir) cells in mesencephalic culture following incubation with striatal extracts. Increasing the severity of hypoxia increased DA content (p < 0.005), but reduced DA activity (p < 0.0001) and trophic activity (p < 0.001). Cocaine exposure reduced striatal DA (p < 0.005) as well as NSEir (p < 0.001) in all conditions relative to vehicle-treated controls. These data suggest that prenatal cocaine exposure enhances the vulnerability of the DA system to the stress of hypoxia, possibly through alterations in neurotrophic activity.

Incidence of sudden infant death syndrome in infants with sickle cell trait

The significantly higher incidence of both sickle cell trait (SCT) and sudden infant death syndrome (SIDS) in the black population suggests that SCT and SIDS may be epidemiologically related. To study this possibility, we identified, for the period of February 1990 to February 1992, all infants with SCT born in Los Angeles County whose disease was diagnosed through the California Newborn Screening Program. We matched these infants with all confirmed cases of SIDS in Los Angeles County from February 1990 to March 1993. Three cases of SCT among 589 infants confirmed to have had SIDS were identified. The incidence of SIDS was 1.25/1000 live births for the general population versus 0.58/1000 cases for the SCT group. This finding remained unchanged when rates were adjusted for ethnicity. We conclude that infants born with SCT are not at increased risk of dying of SIDS.

Sleeping position for infants and cot death in The Netherlands 1985-91

Until the early 1970s the traditional sleeping position for Dutch infants was not prone. After a much publicised lecture in October 1987 on the possible relation between sleeping prone and cot death, the fairly new habit of placing infants prone is being replaced by more traditional positions. The decrease in the prevalence of the prone sleeping position has been documented in six studies. Since 1987 the incidence of registered cot deaths has decreased from 1.04/1000 live births in 1986 to 0.44 in 1991; the real decrease of sudden unexpected death in infancy, however, is greater.

Apnea spells, sudden death, and the role of the apnea monitor

SIDS is the most common cause of death between the ages of 1 week and 1 year. It affects 1 out of every 500 to 600 live births. The etiology of SIDS is unknown. There are no tests currently available to predict the infant who will die from SIDS prior to death. SIDS cannot be prevented. Many infants experience serious apneic spells, however, that require diagnostic evaluation and treatment. Even if the treatment of these infants does not have a large impact on the SIDS rate for the general population, thorough diagnostic evaluations and appropriate use of home apnea-bradycardia monitoring is indicated for this population and may reduce their risk of morbidity or mortality.

Effect of cocaine in early gestation. Physiologic responses to hypoxia in newborn rabbits

To investigate the effect of prenatal cocaine on the physiologic responses to hypoxia, we evaluated ventilation, oxyhemoglobin saturation, and pulse rate at 0.21 FIO2 (baseline) and in response to 20-min exposure to either 0.15 or 0.08 FIO2 on Days 4 to 6 of life in 31 unanesthetized New Zealand white rabbit pups born to cocaine-exposed (30 mg/kg/day of subcutaneous cocaine HCl injection from Days 7 to 15 of a 32-day gestation) or free-fed (injection of sterile water) does. We found that baseline ventilation (measured by dual-sidearm pneumotachograph from the plethysmograph), SaO2 (measured by pulse oximeter), and pulse rate did not differ significantly between cocaine-exposed and free-fed pups. At 0.15 FIO2, cocaine-exposed pups had increased VI (p < 0.0005), VT (p < 0.0005), and VT/TI (p < 0.0005) compared with free-fed pups, but no significant difference in f, TI, TE, TI/TT, SaO2, or pulse rate. At 0.08 FIO2, cocaine-exposed pups had increased VI (p = 0.001), VT/TI (p = 0.021), and TE (p = 0.023) compared with free-fed pups, due primarily to the effects in the first 10 min of hypoxic exposure. However, differences in group response were less apparent than at 0.15 FIO2, with a sustained ventilatory response on prolonged exposure to 0.08 FIO2 among free-fed pups but not cocaine-exposed pups. Further, SaO2 (p < 0.0005) and pulse rate (p = 0.012) were significantly lower among cocaine-exposed pups compared with free-fed pups, particularly after 10-min exposure to 0.08 FIO2 when VI was equivalent.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of maternal substance abuse to subsequent sudden infant death syndrome in offspring

To assess the possible relationship between maternal drug use during pregnancy and subsequent sudden infant death syndrome (SIDS), we identified 1760 cases of SIDS from a population of more than 1.2 million infants (1.45/1000) born in New York City between 1979 and 1989. The SIDS rate in drug-exposed infants was 5.83 per 1000 infants, compared with 1.39 per 1000 infants who were not drug exposed. With control for known associated high-risk variables, the risk ratio for SIDS in each individual drug group (methadone, 3.6; heroin, 2.3; methadone and heroin, 3.2; cocaine, 1.6; cocaine and methadone or heroin, 1.1) was higher than in the non-drug-exposed group. Higher rates of SIDS were found in infants exposed to opiates alone than in cocaine-exposed infants, but increasing rates of SIDS in cocaine-exposed infants toward the end of the decade suggested that "crack" cocaine may be linked to these increasing rates. Declines in the overall rate of SIDS during the decade were observed for both the drug-exposed (11.28 to 4.09 per 1000) and the nonexposed groups (1.70 to 1.05 per 1000). Differences in rates of SIDS between major racial-ethnic groups in nonexposed infants were not apparent if the mothers used drugs during pregnancy. Seasonal variation and distribution of ages at time of SIDS death did not differ between the drug-exposed group and the nonexposed group, suggesting that drug-associated SIDS may provide clues as to the cause or causes of SIDS.

Cocaine and development: mechanisms of fetal toxicity and neonatal consequences of prenatal cocaine exposure

As cocaine use during pregnancy has become increasingly recognized, there also has been increased concern about the toxic and teratogenic properties of cocaine on the fetus. A significant literature exists describing the adverse fetal and neonatal outcomes associated with in utero cocaine exposure. However, specific causality by cocaine on outcome in the human is difficult to ascertain because of multiple confounding variables associated with substance abuse including social factors and polydrug use as well as difficulty in confirming timing, dose and frequency of cocaine exposure. Most literature suggests that prenatal cocaine exposure is associated with developmental risk to the fetus. What is currently unknown is the extent of risk, the additive and/or synergistic factors contributing to cocaine's toxicity and the reversibility of the injury. In this paper we review the pharmacologic properties of cocaine as related to a model of mechanisms for developmental injury secondary to cocaine exposure and the published literature on the adverse fetal and neonatal outcomes associated with cocaine use during pregnancy. Specific attention has been focused on the structural, neurobehavioral and respiratory control teratogenesis.

Responses to hypoxia and hypercapnia in infants of substance-abusing mothers

Because infants of substance-abusing mothers (ISAM) have an increased risk of sudden infant death syndrome and have abnormal sleeping ventilatory patterns, we studied the effects of mild hypoxia during quiet sleep on ventilatory pattern, heart rate, and arousal in 23 healthy ISAM (mean +/- SEM: 9.0 +/- 0.49 weeks of age) and 15 healthy, similarly aged, control infants. Hypercapnic challenges were performed in six ISAM and eight control subjects. Hypoxic arousal responses were elicited by rapidly decreasing inspired oxygen tension to 80 mm Hg for 3 minutes or until arousal occurred. Failure to arouse to hypoxia occurred in the majority of infants in both groups. All infants had a fall in end-tidal carbon dioxide tension during hypoxia, suggesting that each had a hypoxic ventilatory response. However, the fall in end-tidal carbon dioxide tension was significantly less in the ISAM (mean +/- SEM: -4.0 +/- 0.3 vs -8.0 +/- 1.0 mm Hg), suggesting blunted ventilatory responses to hypoxia. Periodic breathing occurred during 9.5% of hypoxic challenges in control infants compared with 37% in ISAM (p = 0.056). Heart rates were significantly higher in the ISAM before, during, and after hypoxic challenges. Hypercapnic challenges (inspired carbon dioxide tension of 60 mm Hg for a maximum of 3 minutes) resulted in arousal in all infants; however, ISAM required a significantly longer exposure to hypercapnia before arousal (mean +/- SEM; 116 +/- 7.8 vs 79 +/- 13.9 seconds; p < 0.02). We conclude that ISAM have an impaired repertoire of protective responses to hypoxia and hypercapnia during sleep, and that this may play a role in their increased risk for sudden infant death syndrome.

Reappraisal of the SIDS enigma: an epidemiological and clinicopathological approach

The possibility that most cases of sudden infant death syndrome (SIDS) are caused by a transmissible agent is explored. A hypothesis of causation is developed using pathological and epidemiological data and our microbiological findings. The nature and distribution of vascular damage together with the consistent finding of liquid blood, in addition to the epidemiological features of SIDS, form the basis of the hypothesis that a bacterial toxin is a likely single cause of most cases of the syndrome. Future research ideas and a new definition of SIDS are proposed.

Control of breathing in babies of narcotic- and cocaine-abusing mothers

To learn if chemoreceptor control of breathing is abnormal in babies whose mothers took narcotics, cocaine, or both drugs during pregnancy, we performed hypoxia and hypercapnia challenges on 28 babies (greater than or equal to 36 weeks gestation). Six babies were exposed to narcotics, six to cocaine, nine to both drugs, and seven babies were controls. Studies were done at 3 and 8 weeks and 3 and 5 months of age. Gestational ages were similar, but birth weight was lower in the cocaine group. Respiratory rate was higher in both groups of cocaine-exposed babies at 3 weeks. End-tidal partial pressure of CO2 (PCO2) was decreased and partial pressure of O2 (PO2) increased at 3 and 8 weeks in babies exposed to narcotics plus cocaine. At 3 weeks, babies exposed to narcotics plus cocaine had a shift to the left in CO2 response with a normal slope; at 8 weeks, both intercept and slope were decreased. Responses to hypoxia were similar among the four groups. Babies exposed to narcotics plus cocaine before birth have abnormalities in control of breathing in the first months after birth.

Effect of prenatal cocaine on respiration, heart rate, and sudden infant death syndrome

We studied 114 neonates by pneumocardiogram recordings in order to examine the effects of cocaine with and without opiate exposure on neonatal respiration, heart rate, apparent life threatening events (ALTE), and sudden infant death syndrome (SIDS). In full-term infants exposed to cocaine without opiates we found increased longest apnea duration and more episodes of bradycardia, but decreased periodic breathing and average heart rate than in control full-term infants. Term infants prenatally exposed to cocaine with opiates also had less periodic breathing. Preterm infants exposed to cocaine with and without opiates had decreased apnea density and periodic breathing compared with preterm controls. Discriminant analysis to determine whether perinatal asphyxia or exposure to other drugs could predict cardiorespiratory abnormalities showed no consistent relationship. In 72 of 114 infants available for follow-up, no ALTE occurred but two were lost to SIDS. Our data support the hypothesis that prenatal cocaine exposure may perturb, albeit subtly, the maturation of respiratory control, resulting in disruption of postnatal respiration.