Overview
Definition:
Neonatal Abstinence Syndrome (NAS) is a constellation of signs and symptoms that occur in newborns exposed to opioids in utero, typically in the last trimester of pregnancy
It represents withdrawal from substances that have been chronically used by the mother.
Epidemiology:
The incidence of NAS has significantly increased in recent decades, correlating with the opioid epidemic
Rates vary by region and healthcare setting, with some reports indicating 1 in 20 births in the US experiencing NAS
Factors include maternal opioid use disorder, prescribed opioid use during pregnancy, and illicit opioid use.
Clinical Significance:
NAS requires prompt recognition and management to prevent complications and ensure optimal infant outcomes
Understanding scoring systems guides treatment intensity, and appropriate pharmacotherapy, such as morphine or buprenorphine, is crucial for effective withdrawal symptom control and long-term infant health.
Clinical Presentation
Symptoms:
Onset typically within 12-72 hours after birth, but can be delayed
Irritability, incessant crying, poor feeding, vomiting, diarrhea, tremors, fever, sweating, yawning, sneezing, nasal stuffiness, and seizures.
Signs:
High-pitched cry, hypertonia, increased muscle tone, exaggerated startle reflex, poor sleep, weight loss, dehydration, and excoriations on hands and knees from excessive sucking or scratching.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on maternal history of opioid use during pregnancy and characteristic signs and symptoms in the neonate
Urine toxicology for the infant and mother can confirm recent opioid exposure, but a negative screen does not rule out NAS
Scoring systems like the Finnegan Neonatal Abstinence Scoring System (Finnegan NAS) are used to quantify symptom severity.
Diagnostic Approach
History Taking:
Detailed maternal history regarding substance use (prescription and illicit opioids, benzodiazepines, other substances), timing of last use, dosage, and duration of use
Obstetric history and previous neonatal outcomes
Family history of substance use disorder.
Physical Examination:
Systematic assessment for signs of withdrawal: neurological (tremors, hyperreflexia, irritability), gastrointestinal (vomiting, diarrhea, poor feeding), autonomic (sweating, fever, nasal congestion, sneezing), and somatic (stiff posture, yawning)
Assess for dehydration and weight trend.
Investigations:
Urine toxicology screen for the neonate and mother for opioids and other substances
Meconium toxicology can detect exposure earlier in gestation
Serum electrolytes, glucose, calcium, and magnesium may be checked if seizures or metabolic disturbances are suspected
Chest X-ray if respiratory distress is present.
Differential Diagnosis:
Sepsis, meningitis, hypoxic-ischemic encephalopathy, metabolic disorders (hypoglycemia, hypocalcemia), neurological disorders, prematurity, and other drug withdrawal syndromes (e.g., benzodiazepines, barbiturates).
Management
Initial Management:
Provide a quiet, low-stimulus environment
Maintain adequate hydration and nutrition
Optimize feeding
Swaddling and positioning can help soothe the infant
Non-pharmacological interventions are the first line of management.
Medical Management:
Pharmacotherapy is initiated when withdrawal symptoms are severe and interfere with feeding, sleep, or weight gain, or when Finnegan NAS scores consistently exceed a predefined threshold (e.g., >8)
Morphine sulfate is the most common initial agent
Dosing is typically weight-based and titratable, initiated orally or IV
Buprenorphine is an alternative, particularly for prolonged withdrawal or when morphine is ineffective
it has a longer half-life and can be used once withdrawal is established
Typical starting dose for morphine: 0.1 mg/kg/dose every 4 hours
Typical starting dose for buprenorphine: 1-3 mcg/kg/dose every 12-24 hours, titratable.
Supportive Care:
Frequent monitoring of vital signs and NAS scores
Skin care to prevent excoriations
Pacifier use to reduce non-nutritive sucking
Parental involvement and education
Multidisciplinary team approach involving neonatologists, nurses, social workers, and substance abuse counselors.
Weaning Protocol:
Once stable on pharmacotherapy, a gradual tapering of medication is implemented over weeks to months, guided by NAS scores and infant tolerance
The goal is to achieve minimal symptoms and independent feeding and weight gain.
Complications
Early Complications:
Seizures, dehydration, failure to thrive, gastrointestinal issues (vomiting, diarrhea), sleep disturbances, and respiratory problems due to hyperirritability
Sleep disruption can affect neurodevelopment.
Late Complications:
Long-term neurodevelopmental effects such as attention deficits, behavioral problems, language delays, and learning disabilities have been reported in some children with history of NAS
However, the direct causality and prevalence are still subjects of ongoing research, with confounding factors like maternal factors and home environment playing a role.
Prevention Strategies:
Antenatal care and counseling for pregnant women using opioids, including opioid agonist therapy (OAT) like methadone or buprenorphine, which can significantly reduce NAS severity
Early identification of at-risk pregnancies and planning for postnatal care.
Prognosis
Factors Affecting Prognosis:
Severity of NAS, effectiveness of treatment, presence of co-occurring maternal substance use or medical conditions, quality of postnatal care, and socioeconomic factors.
Outcomes:
With appropriate management, most infants with NAS achieve good outcomes and do not experience long-term sequelae
Early and effective intervention is key
Infants with severe withdrawal or complications may require longer hospital stays.
Follow Up:
Long-term follow-up is recommended for infants with a history of NAS, focusing on developmental milestones, behavior, and academic performance
Early intervention services should be considered if developmental delays are identified.
Key Points
Exam Focus:
The Finnegan NAS scoring system is crucial
know its components and interpretation
Understand the indications for starting pharmacotherapy and the initial drug choices (morphine/buprenorphine)
Dosing and titrations are key
Recognize complications and long-term implications.
Clinical Pearls:
Always consider maternal substance use history as a primary clue
Environmental modification (quiet room, swaddling) is paramount before starting pharmacotherapy
Monitor for withdrawal symptoms for at least 24-72 hours post-birth before initiating treatment
Buprenorphine is effective for prolonged withdrawal or when morphine fails.
Common Mistakes:
Delayed diagnosis by attributing symptoms to other causes
Inadequate scoring leading to delayed or undertreated pharmacotherapy
Over-reliance on pharmacotherapy without optimizing non-pharmacological measures
Failure to consider co-morbid maternal substance use
Insufficient follow-up for potential long-term developmental issues.