Chapter 37

### I. Intensive and convalescent care

1. Definitions

1. Neonatal abstinence syndrome (NAS), also known as neonatal drug withdrawal or neonatal passive addiction, is defined as a group of clinical signs in a neonate resulting from prolonged exposure to illicit or prescribed drugs.

2. Drug withdrawal: NAS signs and symptoms worsen as drug levels in the infant decrease, due to physical dependence.

3. Drug toxicity: Signs and symptoms improve with drug elimination.

2. Incidence

1. NAS is more common in infants born to opioid-dependent women than in infants born to women dependent on other drugs or alcohol.

2. It is estimated that 60% to 90% of infants born to substance using mothers will develop signs of NAS, and of these, 50% to 75% will require treatment.

3. Pathophysiology

1. Presentation of NAS depends on several maternal and infant factors, such as dosages, most recent use, placental transfer, and metabolism.

2. Prolonged drug use causes physical dependence. Abrupt discontinuation results in excessive release of noradrenaline, producing the autonomic, behavioral, and GI signs characteristic of NAS.

3. Transient signs of acute toxicity may be seen immediately postdelivery, whereas withdrawal signs may be delayed as the drug is metabolized and cleared by the infant.

4. Iatrogenic NAS may result from use of narcotics for prolonged mechanical ventilation, surgeries, and extracorporeal membrane oxygenation (ECMO).

4. Risk factors

Common drugs that cause NAS

The most common drugs that cause NAS include opioids, central nervous system (CNS) depressants, CNS stimulants, hallucinogens, and selective serotonin reuptake inhibitors (Table 37-1).

1. Opioids

1. Natural, endogenous, or synthetic opioids produce analgesia by binding opioid receptors in the CNS, peripheral nervous system, and gastrointestinal (GI) system and inhibiting noradrenaline release.

2. Opioids cause sedation, euphoria, respiratory depression, and decreased GI motility.

3. Neonates exposed to opioids in utero show signs of withdrawal 55% to 99% of the time.

• Heroin (diacetylmorphine)

A short-acting opioid agonist that typically produces withdrawal symptoms in the first 24 hours of life. Babies born to heroin-addicted mothers have marked decrease in RDS in premature infants. Heroin may cause enzyme induction and increases in surfactant production. There is also a decrease incidence of neonatal jaundice, because heroin accelerates bilirubin conjugation. Recent findings of heroin use have indicated that quinine is often mixed with heroin prior to use. Quinine has been shown to cause hemolytic anemia.

A pure opioid agonist has withdrawal signs that are delayed for several days after birth up to a month due to its long half-life. Up to 80% of neonates show moderate to severe withdrawal signs. Doses greater than 20 mg daily will cause NAS in >95% of infants. However, the dose that is usually needed to control maternal craving is 40 to 60 mg. Symptoms in neonates are less severe if the dose of maternal methadone is decreased to less than 20 mg a minimum of 4 weeks prior to delivery. Since abrupt change in maternal doses are contraindicated due to fetal harm, most mothers are unable to be weaned off during pregnancy, and use in the third trimester will ...

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