Pharmacoepidemiology of opiate use in the neonatal ICU: Increasing cumulative doses and iatrogenic opiate withdrawal

Institutional and Regional Variation in Opioid Prescribing for Hospitalized Infants in the US

Importance

High-risk infants, defined as newborns with substantial neonatal-perinatal morbidities, often undergo multiple procedures and require prolonged intubation, resulting in extended opioid exposure that is associated with poor outcomes. Understanding variation in opioid prescribing can inform quality improvement and best-practice initiatives.

Objective

To examine regional and institutional variation in opioid prescribing, including short- and long-acting agents, in high-risk hospitalized infants.

Design, Setting, and Participants

This retrospective cohort study assessed high-risk infants younger than 1 year from January 1, 2016, to December 31, 2022, at 47 children's hospitals participating in the Pediatric Health Information System (PHIS). The cohort was stratified by US Census region (Northeast, South, Midwest, and West). Variation in cumulative days of opioid exposure and methadone treatment was examined among institutions using a hierarchical generalized linear model. High-risk infants were identified by International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes for congenital heart disease surgery, medical and surgical necrotizing enterocolitis, extremely low birth weight, very low birth weight, hypoxemic ischemic encephalopathy, extracorporeal membrane oxygenation, and other abdominal surgery. Infants with neonatal opioid withdrawal syndrome, in utero substance exposure, or malignant tumors were excluded.

Exposure

Any opioid exposure and methadone treatment.

Main Outcomes and Measures

Regional and institutional variations in opioid exposure.

Results

Overall, 132 658 high-risk infants were identified (median [IQR] gestational age, 34 [28-38] weeks; 54.5% male). Prematurity occurred in 30.3%, and 55.3% underwent surgery. During hospitalization, 76.5% of high-risk infants were exposed to opioids and 7.9% received methadone. Median (IQR) length of any opioid exposure was 5 (2-12) cumulative days, and median (IQR) length of methadone treatment was 19 (7-46) cumulative days. There was significant hospital-level variation in opioid and methadone exposure and cumulative days of exposure within each US region. The computed intraclass correlation coefficient estimated that 16% of the variability in overall opioid prescribing and 20% of the variability in methadone treatment was attributed to the individual hospital.

Conclusions and Relevance

In this retrospective cohort study of high-risk hospitalized infants, institution-level variation in overall opioid exposure and methadone treatment persisted across the US. These findings highlight the need for standardization of opioid prescribing in this vulnerable population.

Neonatal opioid toxicity: opioid withdrawal (abstinence) syndrome with emphasis on pharmacogenomics and respiratory depression

The increasing use of opioids in pregnant women has led to an alarming rise in the number of cases of neonates with drug-induced withdrawal symptoms known as neonatal opioid withdrawal syndrome (NOWS). NOWS is a toxic heterogeneous condition with many neurologic, autonomic, and gastrointestinal symptoms including poor feeding, irritability, tachycardia, hypertension, respiratory defects, tremors, hyperthermia, and weight loss. Paradoxically, for the management of NOWS, low doses of morphine, methadone, or buprenorphine are administered. NOWS is a polygenic disorder supported by studies of genomic variation in opioid-related genes. Single-nucleotide polymorphisms (SNPs) in CYP2B6 are associated with variations in NOWS infant responses to methadone and SNPs in the OPRM1, ABCB1, and COMT genes are associated with need for treatment and length of hospital stay. Epigenetic gene changes showing higher methylation levels in infants and mothers have been associated with more pharmacologic treatment in the case of newborns, and for mothers, longer infant hospital stays. Respiratory disturbances associated with NOWS are not well characterized. Little is known about the effects of opioids on developing neonatal respiratory control and respiratory distress (RD), a potential problem for survival of the neonate. In a rat model to test the effect of maternal opioids on the developing respiratory network and neonatal breathing, maternal-derived methadone increased apneas and lessened RD in neonates at postnatal (P) days P0 and P1. From P3, breathing normalized with age suggesting reorganization of respiratory rhythm-generating circuits at a time when the preBötC becomes the dominant inspiratory rhythm generator. In medullary slices containing the preBötC, maternal opioid treatment plus exposure to exogenous opioids showed respiratory activity was maintained in younger but not older neonates. Thus, maternal opioids blunt centrally controlled respiratory frequency responses to exogenous opioids in an age-dependent manner. In the absence of maternal opioid treatment, exogenous opioids abolished burst frequencies at all ages. Prenatal opioid exposure in children stunts growth rate and development while studies of behavior and cognitive ability reveal poor performances. In adults, high rates of attention deficit disorder, hyperactivity, substance abuse, and poor performances in intelligence and memory tests have been reported.

Opioid and Methadone Use for Infants With Surgically Treated Necrotizing Enterocolitis

Importance

Necrotizing enterocolitis (NEC) requiring surgical intervention is the most common reason for surgical procedures in preterm neonates. Opioids are used to manage postoperative pain, with some infants requiring methadone to treat physiologic opioid dependence or wean from nonmethadone opioid treatment during recovery.

Objective

To describe postoperative opioid use and methadone treatment for infants with surgically treated NEC and evaluate postoperative outcomes.

Design, Setting, and Participants

A cohort study of infants with surgically treated NEC admitted from January 1, 2013, to December 31, 2022, to 48 Children's Hospital Association hospitals contributing data to the Pediatric Health Information System (PHIS) was performed. Infants who received methadone preoperatively, were aged 14 days or less at the time of the operation, had a congenital heart disease-related operation, or died within 90 days of the operation were excluded. Mixed-effects multivariable logistic regression was used to evaluate thresholds for duration of opioid use after the operation associated with methadone treatment and clinical outcomes associated with methadone use were enumerated.

Exposure

Postoperative administration of nonmethadone opioids.

Main Outcomes and Measures

Methadone use and postoperative length of stay, ventilator days, and total parenteral nutrition (TPN) days.

Results

Of the 2037 infants with surgically treated NEC identified, the median birth weight was 920 (IQR, 700.0-1479.5) g; 1204 were male (59.1%), 911 were White (44.7%), and 343 were Hispanic (16.8%). Infants received nonmethadone opioids for a median of 15 (IQR, 6-30) days after the operation and 231 received methadone (11.3%). The median first day of methadone use was postoperative day 18 (IQR, days 9-64) and continued for 28 days (IQR, 14-73). Compared with infants who received nonmethadone opioids for 1 to 5 days, infants receiving 16 to 21 days of opioids were most likely to receive methadone treatment (odds ratio, 11.45; 95% CI, 6.31-20.77). Methadone use was associated with 21.41 (95% CI, 10.81-32.02) more days of postoperative length of stay, 10.80 (95% CI, 3.63-17.98) more ventilator days, and 16.21 (95% CI, 6.34-26.10) more TPN days.

Conclusions and Relevance

In this cohort study of infants with surgically treated NEC, prolonged use of nonmethadone opioids after the operation was associated with an increased likelihood of methadone treatment and increased postoperative length of stay, ventilation, and TPN use. Optimizing postoperative pain management for infants requiring an operation may decrease the need for methadone treatment and improve health care use.

Maternal and iatrogenic neonatal opioid withdrawal syndrome: Differences and similarities in recognition, management, and consequences

Opioids are potent analgesics used to manage pain in both young and old, but the increased use in the pregnant population has significant individual and societal implications. Infants dependent on opioids, either through maternal or iatrogenic exposure, undergo neonatal opioid withdrawal syndrome (NOWS), where they may experience withdrawal symptoms ranging from mild to severe. We present a detailed and original review of NOWS caused by maternal opioid exposure (mNOWS) and iatrogenic opioid intake (iNOWS). While these two entities have been assessed entirely separately, recognition and treatment of the clinical manifestations of NOWS overlap. Neonatal risk factors such as age, genetic predisposition, drug type, and clinical factors like type of opioid, cumulative dose of opioid exposure, and disease status affect the incidence of both mNOWS and iNOWS, as well as their severity. Recognition of withdrawal is dependent on clinical assessment of symptoms, and the use of clinical assessment tools designed to determine the need for pharmacotherapy. Treatment of NOWS relies on a combination of non-pharmacological therapies and pharmacological options. Long-term consequences of opioids and NOWS continue to generate controversy, with some evidence of anatomic brain changes, but conflicting animal and human clinical evidence of significant cognitive or behavioral impacts on school-age children. We highlight the current knowledge on clinically relevant recognition, treatment, and consequences of NOWS, and identify new advances in clinical management of the neonate. This review brings a unique clinical perspective and critically analyzes gaps between the clinical problem and our preclinical understanding of NOWS.

Characterization of the intergenerational impact of in utero and postnatal oxycodone exposure

Prescription opioid abuse during and after pregnancy is a rising public health concern. While earlier studies have documented that offspring exposed to opioids in utero have impaired neurodevelopment, a significant knowledge gap remains in comparing the overall development between offspring exposed in utero and postnatally. Adding a layer of complexity is the role of heredity in the overall development of these exposed offspring. To fill in these important knowledge gaps, the current study uses a preclinical rat model mimicking oxycodone (oxy) exposure in utero (IUO) and postnatally (PNO) to investigate comparative and intergenerational effects in the two different treatment groups. While significant phenotypic attributes were observed with the two treatments and across the two generations, RNA sequencing revealed alterations in the expression of key synaptic genes in the two exposed groups in both generations. RNA sequencing and post validation of genes using RT-PCR highlighted the differential expression of several neuropeptides associated with the hypocretin system, a system recently implicated in addiction. Further, behavior studies revealed anxiety-like behaviors and social deficits that persisted even in the subsequent generations in the two treatment groups. To summarize, our study for the first time reveals a new line of investigation on the potential risks associated with oxy use during and after pregnancy, specifically the disruption of neurodevelopment and intergenerational impact on behavior.

Brain-Derived Extracellular Vesicle microRNA Signatures Associated with In Utero and Postnatal Oxycodone Exposure

Oxycodone (oxy) is a semi-synthetic opioid commonly used as a pain medication that is also a widely abused prescription drug. While very limited studies have examined the effect of in utero oxy (IUO) exposure on neurodevelopment, a significant gap in knowledge is the effect of IUO compared with postnatal oxy (PNO) exposure on synaptogenesis—a key process in the formation of synapses during brain development—in the exposed offspring. One relatively unexplored form of cell–cell communication associated with brain development in response to IUO and PNO exposure are extracellular vesicles (EVs). EVs are membrane-bound vesicles that serve as carriers of cargo, such as microRNAs (miRNAs). Using RNA-Seq analysis, we identified distinct brain-derived extracellular vesicle (BDEs) miRNA signatures associated with IUO and PNO exposure, including their gene targets, regulating key functional pathways associated with brain development to be more impacted in the IUO offspring. Further treatment of primary 14-day in vitro (DIV) neurons with IUO BDEs caused a significant reduction in spine density compared to treatment with BDEs from PNO and saline groups. In summary, our studies identified for the first time, key BDE miRNA signatures in IUO- and PNO-exposed offspring, which could impact their brain development as well as synaptic function.

Continuous intravenous to oral morphine switch in very premature ventilated infants: A retrospective study on efficacy, efficiency, and tolerability

Background

Continuous intravenous (IV) morphine is commonly used in ventilated neonates. Oral route is theoretically feasible but data on oral morphine in ventilated premature infants are lacking.

Objective

To assess the efficacy, efficiency, and tolerability of a continuous intravenous to oral morphine switch protocol.

Design

Retrospective study.

Setting

Single level III center's neonatal intensive care unit.

Patients

Ventilated premature infants hospitalized in the NICU in 2016 and 2017, receiving continuous IV morphine with an expected ventilation course of at least 72 more hours. We excluded patients treated for withdrawal syndrome or palliative care.

Interventions

Continuous IV to oral morphine switch with the same initial cumulated daily dose.

Main outcome measures

Pain scores (ComfortNeo scale) and morphine doses were analyzed over time using Friedman's test in the 24 hours preceding and the 48 hours following the oral switch. Adverse effects attributable to opioids were collected.

Results

Seventeen infants were included with a median [IQR] gestational age at birth of 25.9 [24.6‐26.9] weeks and a median postnatal age at oral switch of 30 [22‐36] days. One patient's intravenous treatment had to be resumed because of a high ComfortNeo score. All others remained on oral morphine. No significant change over time was observed for ComfortNeo scores (P = .15). Median [IQR] doses were 13.5 [10‐20] µg/kg/h in the IV period and significantly increased to 15 [10‐25] µg/kg/h in the oral period (P = .009). No short‐term respiratory, digestive, or urinary adverse event was observed. After a median [IQR] duration of 13 [4‐20] days of oral morphine treatment, 11 (65%) patients showed signs of withdrawal. Upon hospital discharge, 16 infants (94%) had bronchopulmonary dysplasia and none had severe cerebral abnormality on brain imaging.

Conclusion

Oral morphine might be useful in ventilated neonates in the NICU but deserves further studies and additional safety assessment.

Epidural and Spinal Anesthesia for Newborn Surgery

Neuraxial (spinal and epidural) anesthesia has become commonplace in the care of neonates undergoing surgical procedures. These techniques afford many benefits, and, when properly performed, are extremely safe. This article reviews the benefits, risks, and applications of neuraxial anesthesia in neonates.

Evaluation of Postnatal Sedation in Full-Term Infants

Prolonged sedation in infants leads to a high incidence of physical dependence. We inquired: (1) "How long does it take to develop physical dependence to sedation in previously naïve full-term infants without known history of neurologic impairment?" and (2) "What is the relationship between length of sedation to length of weaning and hospital stay?". The retrospective study included full-term patients over a period of one year that were <1 year of age and received opioids and benzodiazepines >72 hours. Quantification of fentanyl, morphine, and midazolam were compared among three time periods: <5 days, 5-30 days, and >30 days using t-test or one-way analysis of variance. Identified full-term infants were categorized into surgical (14/44) or medical (10/44) groups, while those with neurological involvement (20/44) were excluded. Physical dependence in full-term infants occurred following sedation ≥5 days. Infants with surgical disease received escalating doses of morphine and midazolam when administered >30 days. A positive association between length of sedation and weaning period was found for both respiratory (p < 0.01) and surgical disease (p = 0.012) groups, while length of sedation is related to hospital stay for the respiratory (p < 0.01) but not the surgical disease group (p = 0.1). Future pharmacological directions should lead to standardized sedation protocols and evaluate patient neurocognitive outcomes.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Reduced Sufentanil Doses are Effective for Postoperative Analgesia After Ductal Closure in Extremely Premature Infants: A 10 Years Retrospective Cohort Study

OBJECTIVES

The objective of the study was to assess the efficacy of reduced sufentanil doses for postoperative analgesia following surgical ductal closure in extremely premature infants.

METHODS

This was a retrospective, single-center, cohort study comparing 2 sufentanil dosing regimens used between 2001 and 2010 and included all infants born at <28 weeks of gestation with surgical ductal closure. Sufentanil doses were reduced in 2007 as a standard of care. Time was divided into 3 epochs to distinguish the effects of practice changes over time from the effects of sufentanil dose change: epoch 1 (2001 to 2004), epoch 2 (May 2005 to 2007), and epoch 3 (June 2007 to 2010).

RESULTS

A total of 109 of 114 eligible infants were analyzed (mean [±SD], gestational age: 25.1 [±1.1] wk; mean [±SD], birth weight: 756 [±144] g). Median sufentanil doses were significantly higher during epochs 1 and 2 (0.1 to 0.2 µg/kg/h) than during epoch 3 (0.03 to 0.04 µg/kg/h) (P<0.0001). EDIN (Echelle de Douleur et d'Inconfort du Nouveau-né) pain scores were mostly ≤4 throughout the study period and their changes over time were not contemporaneous with the reduction in sufentanil doses; they were lower during epoch 1 versus epochs 2 and 3 (P<0.0001) and comparable between epochs 2 and 3. Midazolam doses and paracetamol use were not higher during epoch 3 as compared with epochs 1 and 2. No difference in opioid-related adverse events was observed between the 3 epochs.

CONCLUSION

Our study supports the use of low continuous intravenous sufentanil doses, consistent with morphine doses currently recommended in this population.

Differences in Pediatric Pain Management by Unit Types

PURPOSE

The purpose of this study was to determine differences in pediatric pain management by unit type in hospitals across the United States. The aims were to (a) compare unit-type rates of assessment, intervention, and reassessment (AIR), and (b) describe differences in assessment tools and intervention use by unit type.

DESIGN

The study used a cross-sectional design. A secondary analysis of 2013 data from the National Database of Nursing Quality Indicators (NDNQI®) pain AIR cycle indicator was conducted. The sample included 984 pediatric units in 390 hospitals.

METHODS

Data were gathered via retrospective chart review on the pain assessment tool used, presence of pain, interventions, and reassessment. Descriptive statistics and the Kruskal-Wallis one-way analysis of variance test were conducted. Post-hoc analyses included the Wilcoxon-rank sum test with Bonferroni correction.

FINDINGS

Across all units the mean unit-level percentage of patients assessed for pain was 99.6%. Of those patients assessed, surgical units had the highest average unit-level percentage of patients with pain, while Level 4 neonatal intensive care units (NICUs) had the lowest. The most commonly used assessment tool among all units was the Faces, Legs, Activity, Crying, and Consolability (FLACC) Scale. The Neonatal Pain, Agitation, and Sedation Scale (N-PASS) and Neonatal Infant Pain Scale (NIPS) specifically developed for infants were more commonly used across NICU unit types. The mean unit-level percentage of patients with pain receiving an intervention was 89.4%, and reassessment was 83.6%. Overall, pharmacologic methods were the most common pain intervention, while music was the least common.

CONCLUSIONS

Assessments were performed routinely, yet interventions and reassessments were not. Pain AIR cycle completion varied by unit type. Pain was also widely present across many unit types, and pharmacologic methods were most frequently used.

CLINICAL RELEVANCE

Frontline nurses are instrumental to pain management and have the ability to improve patient care and outcomes by effectively managing pain. A comprehensive understanding of it provides valuable insight into improving our practice to produce the best outcomes for pediatric patients.