Long-Term Effects of Neonatal Morphine Infusion on Pain Sensitivity: Follow-Up of a Randomized Controlled Trial

Impact of neonatal pain and opiate administration in animal models: A meta-analysis concerning pain threshold

BACKGROUND AND AIM

Neonatal intensive care treatment, including frequently performed painful procedures and administration of analgesic drugs, can have different effects on the neurodevelopment. This systematic review and meta-analysis aimed to investigate the influence of pain, opiate administration, and pre-emptive opiate administration on pain threshold in animal studies in rodents, which had a brain development corresponding to preterm and term infants.

METHODS

A systematic literature search of electronic data bases including CENTRAL (OVID), CINAHL (EBSCO), Embase.com, Medline (OVID), Web of Science, and PsycInfo (OVID) was conducted. A total of 42 studies examining the effect of pain (n = 38), opiate administration (n = 9), and opiate administration prior to a painful event (n = 5) in rodents were included in this analysis.

RESULTS

The results revealed that pain (g = 0.42, 95%CI 0.16-0.67, p = 0.001) increased pain threshold leading to hypoalgesia. Pre-emptive opiate administration had the opposite effect, lowering pain threshold, when compared to pain without prior treatment (g = -1.79, 95%CI -2.71-0.86, p = 0.0001). Differences were found in the meta regression for type of stimulus (thermal: g = 0.66, 95%CI 0.26-1.07, p = 0.001; vs. mechanical: g = 0.13, 95%CI -0.98-1.25, p = 0.81) and gestational age (b = -1.85, SE = 0.82, p = 0.027). In addition, meta regression indicated an association between higher pain thresholds and the amount of cumulative pain events (b = 0.06, SE = 0.03, p = 0.05) as well as severity of pain events (b = 0.94, SE = 0.28, p = 0.001).

CONCLUSION

Neonatal exposure to pain results in higher pain thresholds. However, caution is warranted in extrapolating these findings directly to premature infants. Further research is warranted to validate similar effects in clinical contexts and inform evidence-based practices in neonatal care.

Biomarkers for assessing pain and pain relief in the neonatal intensive care unit

Newborns admitted to the neonatal intensive care unit (NICU) regularly undergo painful procedures and may face various painful conditions such as postoperative pain. Optimal management of pain in these vulnerable preterm and term born neonates is crucial to ensure their comfort and prevent negative consequences of neonatal pain. This entails accurate and timely identification of pain, non-pharmacological pain treatment and if needed administration of analgesic therapy, evaluation of treatment effectiveness, and monitoring of adverse effects. Despite the widely recognized importance of pain management, pain assessment in neonates has thus far proven to be a challenge. As self-report, the gold standard for pain assessment, is not possible in neonates, other methods are needed. Several observational pain scales have been developed, but these often rely on snapshot and largely subjective observations and may fail to capture pain in certain conditions. Incorporation of biomarkers alongside observational pain scores holds promise in enhancing pain assessment and, by extension, optimizing pain treatment and neonatal outcomes. This review explores the possibilities of integrating biomarkers in pain assessment in the NICU.

Opioids for procedural pain in neonates

BACKGROUND

Neonates might be exposed to numerous painful procedures due to diagnostic reasons, therapeutic interventions, or surgical procedures. Options for pain management include opioids, non-pharmacological interventions, and other drugs. Morphine, fentanyl, and remifentanil are the opioids most often used in neonates. However, negative impact of opioids on the structure and function of the developing brain has been reported.

OBJECTIVES

To evaluate the benefits and harms of opioids in term or preterm neonates exposed to procedural pain, compared to placebo or no drug, non-pharmacological intervention, other analgesics or sedatives, other opioids, or the same opioid administered by a different route.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was December 2021.

SELECTION CRITERIA

We included randomized controlled trials conducted in preterm and term infants of a postmenstrual age (PMA) up to 46 weeks and 0 days exposed to procedural pain where opioids were compared to 1) placebo or no drug; 2) non-pharmacological intervention; 3) other analgesics or sedatives; 4) other opioids; or 5) the same opioid administered by a different route.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were pain assessed with validated methods and any harms. We used a fixed-effect model with risk ratio (RR) for dichotomous data and mean difference (MD) for continuous data, and their confidence intervals (CI). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 13 independent studies (enrolling 823 newborn infants): seven studies compared opioids to no treatment or placebo (the main comparison in this review), two studies to oral sweet solution or non-pharmacological intervention, and five studies (of which two were part of the same study) to other analgesics and sedatives. All studies were performed in a hospital setting. Opioids compared to placebo or no drug Compared to placebo, opioids probably reduce pain score assessed with the Premature Infant Pain Profile (PIPP)/PIPP-Revised (PIPP-R) scale during the procedure (MD -2.58, 95% CI -3.12 to -2.03; 199 participants, 3 studies; moderate-certainty evidence); may reduce Neonatal Infant Pain Scale (NIPS) during the procedure (MD -1.97, 95% CI -2.46 to -1.48; 102 participants, 2 studies; low-certainty evidence); and may result in little to no difference in pain score assessed with the Douleur Aiguë du Nouveau-né (DAN) scale one to two hours after the procedure (MD -0.20, 95% CI -2.21 to 1.81; 42 participants, 1 study; low-certainty evidence). The evidence is very uncertain about the effect of opioids on pain score assessed with the PIPP/PIPP-R scale up to 30 minutes after the procedure (MD 0.14, 95% CI -0.17 to 0.45; 123 participants, 2 studies; very low-certainty evidence) or one to two hours after the procedure (MD -0.83, 95% CI -2.42 to 0.75; 54 participants, 2 studies; very low-certainty evidence). The evidence is very uncertain about the effect of opioids on episodes of bradycardia (RR 3.19, 95% CI 0.14 to 72.69; 172 participants, 3 studies; very low-certainty evidence). Opioids may result in an increase in episodes of apnea compared to placebo (RR 3.15, 95% CI 1.08 to 9.16; 199 participants, 3 studies; low-certainty evidence): with one study reporting a concerning increase in severe apnea (RR 7.44, 95% CI 0.42 to 132.95; 31 participants, 1 study; very low-certainty). The evidence is very uncertain about the effect of opioids on episodes of hypotension (RR not estimable, risk difference 0.00, 95% CI -0.06 to 0.06; 88 participants, 2 studies; very low-certainty evidence). No studies reported parent satisfaction with care provided in the neonatal intensive care unit (NICU). Opioids compared to non-pharmacological intervention The evidence is very uncertain about the effect of opioids on pain score assessed with the Crying Requires oxygen Increased vital signs Expression Sleep (CRIES) scale during the procedure when compared to facilitated tucking (MD -4.62, 95% CI -6.38 to -2.86; 100 participants, 1 study; very low-certainty evidence) or sensorial stimulation (MD 0.32, 95% CI -1.13 to 1.77; 100 participants, 1 study; very low-certainty evidence). The other main outcomes were not reported. Opioids compared to other analgesics or sedatives The evidence is very uncertain about the effect of opioids on pain score assessed with the PIPP/PIPP-R during the procedure (MD -0.29, 95% CI -1.58 to 1.01; 124 participants, 2 studies; very low-certainty evidence); up to 30 minutes after the procedure (MD -1.10, 95% CI -2.82 to 0.62; 12 participants, 1 study; very low-certainty evidence); and one to two hours after the procedure (MD -0.17, 95% CI -2.22 to 1.88; 12 participants, 1 study; very low-certainty evidence). No studies reported any harms. The evidence is very uncertain about the effect of opioids on episodes of apnea during (RR 3.27, 95% CI 0.85 to 12.58; 124 participants, 2 studies; very low-certainty evidence) and after the procedure (RR 2.71, 95% CI 0.11 to 64.96; 124 participants, 2 studies; very low-certainty evidence) and on hypotension (RR 1.34, 95% CI 0.32 to 5.59; 204 participants, 3 studies; very low-certainty evidence). The other main outcomes were not reported. We identified no studies comparing different opioids (e.g. morphine versus fentanyl) or different routes for administration of the same opioid (e.g. morphine enterally versus morphine intravenously).

AUTHORS' CONCLUSIONS

Compared to placebo, opioids probably reduce pain score assessed with PIPP/PIPP-R scale during the procedure; may reduce NIPS during the procedure; and may result in little to no difference in DAN one to two hours after the procedure. The evidence is very uncertain about the effect of opioids on pain assessed with other pain scores or at different time points. The evidence is very uncertain about the effect of opioids on episodes of bradycardia, hypotension or severe apnea. Opioids may result in an increase in episodes of apnea. No studies reported parent satisfaction with care provided in the NICU. The evidence is very uncertain about the effect of opioids on any outcome when compared to non-pharmacological interventions or to other analgesics. We identified no studies comparing opioids to other opioids or comparing different routes of administration of the same opioid.

Opioids for procedural pain in neonates

BACKGROUND

Neonates might be exposed to numerous painful procedures due to diagnostic reasons, therapeutic interventions, or surgical procedures. Options for pain management include opioids, non-pharmacological interventions, and other drugs. Morphine, fentanyl, and remifentanil are the opioids most often used in neonates. However, negative impact of opioids on the structure and function of the developing brain has been reported.

OBJECTIVES

To evaluate the benefits and harms of opioids in term or preterm neonates exposed to procedural pain, compared to placebo or no drug, non-pharmacological intervention, other analgesics or sedatives, other opioids, or the same opioid administered by a different route.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was December 2021.

SELECTION CRITERIA

We included randomized controlled trials conducted in preterm and term infants of a postmenstrual age (PMA) up to 46 weeks and 0 days exposed to procedural pain where opioids were compared to 1) placebo or no drug; 2) non-pharmacological intervention; 3) other analgesics or sedatives; 4) other opioids; or 5) the same opioid administered by a different route.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were pain assessed with validated methods and any harms. We used a fixed-effect model with risk ratio (RR) for dichotomous data and mean difference (MD) for continuous data, and their confidence intervals (CI). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 13 independent studies (enrolling 823 newborn infants): seven studies compared opioids to no treatment or placebo (the main comparison in this review), two studies to oral sweet solution or non-pharmacological intervention, and five studies (of which two were part of the same study) to other analgesics and sedatives. All studies were performed in a hospital setting. Opioids compared to placebo or no drug Compared to placebo, opioids probably reduce pain score assessed with the Premature Infant Pain Profile (PIPP)/PIPP-Revised (PIPP-R) scale during the procedure (MD -2.58, 95% CI -3.12 to -2.03; 199 participants, 3 studies; moderate-certainty evidence); may reduce Neonatal Infant Pain Scale (NIPS) during the procedure (MD -1.97, 95% CI -2.46 to -1.48; 102 participants, 2 studies; low-certainty evidence); and may result in little to no difference in pain score assessed with the Douleur Aiguë du Nouveau-né (DAN) scale one to two hours after the procedure (MD -0.20, 95% CI -2.21 to 1.81; 42 participants, 1 study; low-certainty evidence). The evidence is very uncertain about the effect of opioids on pain score assessed with the PIPP/PIPP-R scale up to 30 minutes after the procedure (MD 0.14, 95% CI -0.17 to 0.45; 123 participants, 2 studies; very low-certainty evidence) or one to two hours after the procedure (MD -0.83, 95% CI -2.42 to 0.75; 54 participants, 2 studies; very low-certainty evidence). No studies reported any harms. The evidence is very uncertain about the effect of opioids on episodes of bradycardia (RR 3.19, 95% CI 0.14 to 72.69; 172 participants, 3 studies; very low-certainty evidence). Opioids may result in an increase in episodes of apnea compared to placebo (RR 3.15, 95% CI 1.08 to 9.16; 199 participants, 3 studies; low-certainty evidence). The evidence is very uncertain about the effect of opioids on episodes of hypotension (RR not estimable, risk difference 0.00, 95% CI -0.06 to 0.06; 88 participants, 2 studies; very low-certainty evidence). No studies reported parent satisfaction with care provided in the neonatal intensive care unit (NICU). Opioids compared to non-pharmacological intervention The evidence is very uncertain about the effect of opioids on pain score assessed with the Crying Requires oxygen Increased vital signs Expression Sleep (CRIES) scale during the procedure when compared to facilitated tucking (MD -4.62, 95% CI -6.38 to -2.86; 100 participants, 1 study; very low-certainty evidence) or sensorial stimulation (MD 0.32, 95% CI -1.13 to 1.77; 100 participants, 1 study; very low-certainty evidence). The other main outcomes were not reported. Opioids compared to other analgesics or sedatives The evidence is very uncertain about the effect of opioids on pain score assessed with the PIPP/PIPP-R during the procedure (MD -0.29, 95% CI -1.58 to 1.01; 124 participants, 2 studies; very low-certainty evidence); up to 30 minutes after the procedure (MD -1.10, 95% CI -2.82 to 0.62; 12 participants, 1 study; very low-certainty evidence); and one to two hours after the procedure (MD -0.17, 95% CI -2.22 to 1.88; 12 participants, 1 study; very low-certainty evidence). No studies reported any harms. The evidence is very uncertain about the effect of opioids on episodes of apnea during (RR 3.27, 95% CI 0.85 to 12.58; 124 participants, 2 studies; very low-certainty evidence) and after the procedure (RR 2.71, 95% CI 0.11 to 64.96; 124 participants, 2 studies; very low-certainty evidence) and on hypotension (RR 1.34, 95% CI 0.32 to 5.59; 204 participants, 3 studies; very low-certainty evidence). The other main outcomes were not reported. We identified no studies comparing different opioids (e.g. morphine versus fentanyl) or different routes for administration of the same opioid (e.g. morphine enterally versus morphine intravenously).

AUTHORS' CONCLUSIONS

Compared to placebo, opioids probably reduce pain score assessed with PIPP/PIPP-R scale during the procedure; may reduce NIPS during the procedure; and may result in little to no difference in DAN one to two hours after the procedure. The evidence is very uncertain about the effect of opioids on pain assessed with other pain scores or at different time points. No studies reported if any harms occurred. The evidence is very uncertain about the effect of opioids on episodes of bradycardia or hypotension. Opioids may result in an increase in episodes of apnea. No studies reported parent satisfaction with care provided in the NICU. The evidence is very uncertain about the effect of opioids on any outcome when compared to non-pharmacological interventions or to other analgesics. We identified no studies comparing opioids to other opioids or comparing different routes of administration of the same opioid.

Analgesia, Sedation, and Anesthesia for Neonates With Cardiac Disease

Analgesia, sedation, and anesthesia are a continuum. Diagnostic and/or therapeutic procedures in newborns often require analgesia, sedation, and/or anesthesia. Newborns, in general, and, particularly, those with heart disease, have an increased risk of serious adverse events, including mortality under anesthesia. In this section, we discuss the assessment and management of pain and discomfort during interventions, review the doses and side effects of commonly used medications, and provide recommendations for their use in newborns with heart disease. For procedures requiring deeper levels of sedation and anesthesia, airway and hemodynamic support might be necessary. Although associations of long-term deleterious neurocognitive effects of anesthetic agents have received considerable attention in both scientific and lay press, causality is not established. Nonetheless, an early multimodal, multidisciplinary approach is beneficial for safe management before, during, and after interventional procedures and surgery to avoid problems of tolerance and delirium, which can contribute to long-term cognitive dysfunction.

Frequencies, Modalities, Doses and Duration of Computerized Prescriptions for Sedative, Analgesic, Anesthetic and Paralytic Drugs in Neonates Requiring Intensive Care: A Prospective Pharmacoepidemiologic Cohort Study in 30 French NICUs From 2014 to 2020

Objectives: No consensus exists about the doses of analgesics, sedatives, anesthetics, and paralytics used in critically ill neonates. Large-scale, detailed pharmacoepidemiologic studies of prescription practices are a prerequisite to future research. This study aimed to describe the detailed prescriptions of these drug classes in neonates hospitalized in neonatal intensive care units (NICU) from computerized prescription records and to compare prescriptions by gestational age.

Materials and Methods: We included all neonates requiring intensive care in 30 French level III units from 2014 through 2020 with a computerized prescription for an analgesic, sedative, anesthetic, or paralytic agent. We described frequencies of prescription, methods of administration, concomitant drug prescriptions, and dosing regimen, and compared them across gestational ages.

Results: Among 65,555 neonates, 29,340 (44.8%) were prescribed at least one analgesic (acetaminophen in 37.2% and opioids in 17.8%), sedative (9.8%), anesthetic (8.5%), and/or paralytic agent (1%). Among preterm infants born before 28 weeks, 3,771/4,283 (88.0%) were prescribed at least one of these agents: 69.7% opioids, 41.2% sedatives, 32.5% anesthetics, and 5.8% paralytics. The most frequently prescribed agents were sufentanil (in 10.3% of neonates) and morphine (in 8.0% of neonates) for opioids, midazolam (9.3%) for sedatives, ketamine (5.7%) and propofol (3.3%) for anesthetics. In most neonates, opioids and sedatives were prescribed as continuous infusion, whereas anesthetics were prescribed as single doses. Opioids, sedatives and paralytics were mostly prescribed in association with another agent. Doses varied significantly by gestational age but within a limited range. Gestational age was inversely related to the frequency, cumulative dose and duration of prescriptions. For example, morphine prescriptions showed median (IQR) cumulative doses of 2601 (848–6750) vs. 934 (434–2679) µg/kg and median (IQR) durations of 7 (3–15) vs. 3 (2–5) days in infants born <28 vs. ≥ 37 weeks of gestation, respectively (p-value<0.001).

Conclusion: The prescriptions of analgesic, sedative, anesthetic, or paralytic agent were frequent and often combined in the NICU. Lower gestational age was associated with higher frequencies, longer durations and higher cumulative doses of these prescriptions. Dose-finding studies to determine individualized dosing regimens and studies on long-term neurodevelopmental outcome according to received cumulative doses are required.

Sedoanalgesia in neonatal units

Pain recognition and management continues to be a challenge for health professionals in Neonatal Intensive Care Units. Many of the patients are routinely exposed to repeated painful experiences with demonstrated short- and long-term consequences. Preterm babies are a vulnerable high-risk population. Despite international recommendations, pain remains poorly assessed and managed in many Neonatal Intensive Care Units. Due to there being no general protocol, there is significant variability as regards the guidelines for the approach and treatment of pain between the different Neonatal Intensive Care Units. The objective of this article is to review and assess the general principles of pain in the initial stages of development, its recognition through the use of standardised scales. It also includes its prevention and management with the combination of pharmacological and non-pharmacological measures, as well as to establish recommendations that help alleviate pain in daily clinical practice by optimising pain and stress control in the Neonatal Intensive Care Units.

Methadone effectively attenuates acute and long-term consequences of neonatal repetitive procedural pain in a rat model

BACKGROUND

Painful procedures in early life cause acute pain and can alter pain processing at a spinal level lasting into adulthood. Current methods of analgesia seem unable to prevent both acute and long-term hypersensitivity associated with neonatal pain. The current study aims to prevent acute and long-term hypersensitivity associated with neonatal procedural pain using methadone analgesia in rat pups.

METHODS

Sprague-Dawley rat pups received either methadone (1 mg/kg) or saline prior to repetitive needle pricks into the left hind paw from the day of birth (postnatal day (P)0) to P7. Control littermates received a tactile stimulus. Mechanical sensitivity was assessed during the neonatal period (P0-P7), from weaning to adulthood (3-7 weeks) and following surgical re-injury of the same dermatome in adulthood.

RESULTS

Methadone administration completely reversed acute hypersensitivity from P0 to P7. In addition, neonatal methadone analgesia prevented prolonged hypersensitivity after re-injury in adulthood, without affecting sensitivity from weaning to adulthood.

CONCLUSIONS

The current study shows that neonatal methadone analgesia can attenuate acute as well as long-term hypersensitivity associated with neonatal procedural pain in a rat model.

IMPACT

Methadone treatment attenuates acute and long-term hypersensitivity associated with neonatal pain in a rat model. Clinical effectiveness studies are urgently warranted to assess acute and long-term analgesic effectivity of methadone.

Association of Continuous Opioids and/or Midazolam During Early Mechanical Ventilation with Survival and Sensorimotor Outcomes at Age 2 Years in Premature Infants: Results from the French Prospective National EPIPAGE 2 Cohort

OBJECTIVE

To evaluate the association of early continuous infusions of opioids and/or midazolam with survival and sensorimotor outcomes at age 2 years in very premature infants who were ventilated.

STUDY DESIGN

This national observational study included premature infants born before 32 weeks of gestation intubated within 1 hour after birth and still intubated at 24 hours from the French EPIPAGE 2 cohort. Infants only treated with bolus were excluded. Treated infants received continuous opioid and/or midazolam infusion started before 7 days of life and before the first extubation. Naive infants did not receive these treatments before the first extubation, or received them after the first week of life, or never received them. This study compared treated (n = 450) vs naive (n = 472) infants by using inverse probability of treatment weighting after multiple imputation in chained equations. The primary outcomes were survival and survival without moderate or severe neuromotor or sensory impairment at age 2 years.

RESULTS

Survival at age 2 years was significantly higher in the treated group (92.5% vs 87.9%, risk difference, 4.7%; 95% CI, 0.3-9.1; P = .037), but treated and naive infants did not significantly differ for survival without moderate or severe neuromotor or sensory impairment (86.6% vs 81.3%; risk difference, 5.3%; 95% CI -0.3 to 11.0; P = .063). These results were confirmed by sensitivity analyses using 5 alternative models.

CONCLUSIONS

Continuous opioid and/or midazolam infusions in very premature infants during initial mechanical ventilation that continued past 24 hours of life were associated with improved survival without any difference in moderate or severe sensorimotor impairments at age 2 years.

Opioids for newborn infants receiving mechanical ventilation

BACKGROUND

Mechanical ventilation is a potentially painful and discomforting intervention that is widely used in neonatal intensive care. Newborn infants demonstrate increased sensitivity to pain, which may affect clinical and neurodevelopmental outcomes. The use of drugs that reduce pain might be important in improving survival and neurodevelopmental outcomes.

OBJECTIVES

To determine the benefits and harms of opioid analgesics for neonates (term or preterm) receiving mechanical ventilation compared to placebo or no drug, other opioids, or other analgesics or sedatives.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 9), in the Cochrane Library; MEDLINE via PubMed (1966 to 29 September 2020); Embase (1980 to 29 September 2020); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 29 September 2020). We searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials comparing opioids to placebo or no drug, to other opioids, or to other analgesics or sedatives in newborn infants on mechanical ventilation. We excluded cross-over trials. We included term (≥ 37 weeks' gestational age) and preterm (< 37 weeks' gestational age) newborn infants on mechanical ventilation. We included any duration of drug treatment and any dosage given continuously or as bolus; we excluded studies that gave opioids to ventilated infants for procedures.

DATA COLLECTION AND ANALYSIS

For each of the included trials, we independently extracted data (e.g. number of participants, birth weight, gestational age, types of opioids) using Cochrane Effective Practice and Organisation of Care Group (EPOC) criteria and assessed the risk of bias (e.g. adequacy of randomisation, blinding, completeness of follow-up). We evaluated treatment effects using a fixed-effect model with risk ratio (RR) for categorical data and mean difference (MD) for continuous data. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We included 23 studies (enrolling 2023 infants) published between 1992 and 2019. Fifteen studies (1632 infants) compared the use of morphine or fentanyl versus placebo or no intervention. Four studies included both term and preterm infants, and one study only term infants; all other studies included only preterm infants, with five studies including only very preterm infants. We are uncertain whether opioids have an effect on the Premature Infant Pain Profile (PIPP) Scale in the first 12 hours after infusion (MD -5.74, 95% confidence interval (CI) -6.88 to -4.59; 50 participants, 2 studies) and between 12 and 48 hours after infusion (MD -0.98, 95% CI -1.35 to -0.61; 963 participants, 3 studies) because of limitations in study design, high heterogeneity (inconsistency), and imprecision of estimates (very low-certainty evidence - GRADE). The use of morphine or fentanyl probably has little or no effect in reducing duration of mechanical ventilation (MD 0.23 days, 95% CI -0.38 to 0.83; 1259 participants, 7 studies; moderate-certainty evidence because of unclear risk of bias in most studies) and neonatal mortality (RR 1.12, 95% CI 0.80 to 1.55; 1189 participants, 5 studies; moderate-certainty evidence because of imprecision of estimates). We are uncertain whether opioids have an effect on neurodevelopmental outcomes at 18 to 24 months (RR 2.00, 95% CI 0.39 to 10.29; 78 participants, 1 study; very low-certainty evidence because of serious imprecision of the estimates and indirectness). Limited data were available for the other comparisons (i.e. two studies (54 infants) on morphine versus midazolam, three (222 infants) on morphine versus fentanyl, and one each on morphine versus diamorphine (88 infants), morphine versus remifentanil (20 infants), fentanyl versus sufentanil (20 infants), and fentanyl versus remifentanil (24 infants)). For these comparisons, no meta-analysis was conducted because outcomes were reported by one study.

AUTHORS' CONCLUSIONS

We are uncertain whether opioids have an effect on pain and neurodevelopmental outcomes at 18 to 24 months; the use of morphine or fentanyl probably has little or no effect in reducing the duration of mechanical ventilation and neonatal mortality. Data on the other comparisons planned in this review (opioids versus analgesics; opioids versus other opioids) are extremely limited and do not allow any conclusions. In the absence of firm evidence to support a routine policy, opioids should be used selectively - based on clinical judgement and evaluation of pain indicators - although pain measurement in newborns has limitations.

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.

New techniques, new challenges—The dilemma of pain management for less invasive surfactant administration?

Recent years have seen the increasing use of noninvasive respiratory support in preterm infants with the aim of minimizing the risk of mechanical ventilation and subsequent bronchopulmonary dysplasia. Respiratory distress syndrome is the most common respiratory diagnosis in preterm infants, and is best treated by administration of surfactant. Until recently, this has been performed via an endotracheal tube using premedication, which has often included opiate analgesia; subsequently, the infant has been ventilated. Avoidance of mechanical ventilation, however, does not negate the need for surfactant therapy. Less invasive surfactant administration (LISA) in spontaneously breathing infants is increasing in popularity, and appears to have beneficial effects. However, laryngoscopy is necessary, which carries adverse effects and is painful for the infant. Conventional methods of premedication for intubation tend to reduce respiratory drive, which increases the likelihood of ventilation being required. This has led to intense debate about the best strategy for providing appropriate treatment, taking into account both the respiratory needs of the infant and the need to alleviate procedural pain. Currently, clinical practice varies considerably and there is no consensus with respect to optimal management. This review seeks to summarize the benefits, risks, and challenges associated with this new approach.

Short- and long-term impact of remifentanil on thermal detection and pain thresholds after cardiac surgery: A randomised controlled trial

BACKGROUND

The clinical relevance of the suggested hyperalgesic effects of remifentanil is still unclear, especially in the long term.

OBJECTIVE

The current study evaluated the impact of remifentanil on thermal thresholds 3 days and 12 months after surgery, measured with Quantitative Sensory Testing.

DESIGN

A single-blind, randomised controlled trial.

SETTING

A tertiary care teaching hospital in The Netherlands, from 2014 to 2016.

PATIENTS

A total of 126 patients aged between 18 and 85 years, undergoing cardiothoracic surgery via sternotomy (coronary artery bypass grafts and/or valve replacement) were included. Exclusion criteria were BMI above 35 kg m, history of cardiac surgery, chronic pain conditions, neurological conditions, allergy to opioids or paracetamol, language barrier and pregnancy.

INTERVENTIONS

Patients were allocated randomly to receive intra-operatively either a continuous remifentanil infusion or intermittent intra-operative fentanyl as needed in addition to standardised anaesthesia with propofol and intermittent intravenous fentanyl at predetermined time points.

MAIN OUTCOME MEASURES

Warm and cold detection and pain thresholds 3 days and 12 months after surgery. In addition the use of remifentanil, presence of postoperative chronic pain, age, opioid consumption and pre-operative quality of life were tested as a predictor for altered pain sensitivity 12 months after surgery.

RESULTS

Both warm and cold detection, and pain thresholds, were not significantly different between the remifentanil and fentanyl groups 3 days and 12 months after surgery (P > 0.05). No significant predictors for altered pain sensitivity were identified.

CONCLUSION

Earlier reports of increased pain sensitivity 1 year after the use of remifentanil could not be confirmed in this randomised study using Quantitative Sensory Testing. This indicates that remifentanil plays a minor role in the development of chronic thoracic pain. Still, the relatively high incidence of chronic thoracic pain and its accompanying impact on quality of life remain challenging problems.

TRIAL REGISTRATION

The study was registered at EudraCT (ref: 2013-000201-23) and ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT02031016).

Somatosensory function and pain in extremely preterm young adults from the UK EPICure cohort: sex-dependent differences and impact of neonatal surgery

BACKGROUND

Surgery or multiple procedural interventions in extremely preterm neonates influence neurodevelopmental outcome and may be associated with long-term changes in somatosensory function or pain response.

METHODS

This observational study recruited extremely preterm (EP, <26 weeks' gestation; n=102, 60% female) and term-born controls (TC; n=48) aged 18-20 yr from the UK EPICure cohort. Thirty EP but no TC participants had neonatal surgery. Evaluation included: quantitative sensory testing (thenar eminence, chest wall); clinical pain history; questionnaires (intelligence quotient; pain catastrophising; anxiety); and structural brain imaging.

RESULTS

Reduced thermal threshold sensitivity in EP vs TC participants persisted at age 18-20 yr. Sex-dependent effects varied with stimulus intensity and were enhanced by neonatal surgery, with reduced threshold sensitivity in EP surgery males but increased sensitivity to prolonged noxious cold in EP surgery females (P<0.01). Sex-dependent differences in thermal sensitivity correlated with smaller amygdala volume (P<0.05) but not current intelligence quotient. While generalised decreased sensitivity encompassed mechanical and thermal modalities in EP surgery males, a mixed pattern of sensory loss and sensory gain persisted adjacent to neonatal scars in males and females. More EP participants reported moderate-severe recurrent pain (22/101 vs 4/48; χ2=0.04) and increased pain intensity correlated with higher anxiety and pain catastrophising.

CONCLUSIONS

After preterm birth and neonatal surgery, different patterns of generalised and local scar-related alterations in somatosensory function persist into early adulthood. Sex-dependent changes in generalised sensitivity may reflect central modulation by affective circuits. Early life experience and sex/gender should be considered when evaluating somatosensory function, pain experience, or future chronic pain risk.

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.

Genetic variants associated with thermal pain sensitivity in a paediatric population

Pain sensitivity is an inherited factor that varies strongly between individuals. We investigated whether genetic polymorphisms in the candidate genes COMT, OPRM1, OPRD1, TAOK3, TRPA1, TRPV1, and SCN9A are contributing to experimental pain variability between children. Our study included 136 children and adolescents (8-18 years). Cold and heat pain thresholds were determined with a Thermal Sensory Analyzer. Women and young children were significantly more sensitive to pain (P < 0.05). After correction for age, gender, reaction time, and correction for multiple testing, OPRM1 118A>G G-allele carriers (AG and GG) rated the hot stimulus as significantly less painful than did OPRM1 118A>G AA genotyped individuals (2[1-5] vs 7 [3-9], respectively; P = 0.00005). Additionally, OPRM1 118G allele carriers reached more frequently the minimum temperature limit (44% vs 17%, respectively; P = 0.003) and maximum temperature limit (52% vs 24%, respectively; P = 0.0052), indicative for lower pain sensitivity. The combined genotype, based on expected pain sensitivity, OPRM1 118AA/COMT 472 GA or AA genotyped children, was associated with lower pain thresholds (ie, higher pain sensitivity) than were the OPRM1 118GA or GG/COMT 472GG genotyped children. This is the first study reporting on genetic variants and experimental thermal pain in children and adolescents. OPRM1 rs1799971 and the combined OPRM1/COMT genotype could serve as biomarkers for pain sensitivity.

Opioids for chronic non-cancer pain in children and adolescents

BACKGROUND

Pain is a common feature of childhood and adolescence around the world, and for many young people, that pain is chronic. The World Health Organization guidelines for pharmacological treatments for children's persisting pain acknowledge that pain in children is a major public health concern of high significance in most parts of the world. While in the past, pain was largely dismissed and was frequently left untreated, views on children's pain have changed over time, and relief of pain is now seen as importantWe designed a suite of seven reviews on chronic non-cancer pain and cancer pain (looking at antidepressants, antiepileptic drugs, non-steroidal anti-inflammatory drugs, opioids, and paracetamol as priority areas) in order to review the evidence for children's pain utilising pharmacological interventions in children and adolescents.As the leading cause of morbidity in children and adolescents in the world today, chronic disease (and its associated pain) is a major health concern. Chronic pain (lasting three months or longer) can arise in the paediatric population in a variety of pathophysiological classifications: nociceptive, neuropathic, idiopathic, visceral, nerve damage pain, chronic musculoskeletal pain, and chronic abdominal pain, and other unknown reasons.Opioids are used worldwide for the treatment of pain. They bind to opioid receptors in the central nervous system (mu, kappa, delta, and sigma) and can be agonists, antagonists, mixed agonist-antagonists, or partial agonists. Opioids are generally available in healthcare settings across most high-income countries, but access may be restricted in low- and middle-income countries. For example, opioids currently available in the UK include: buprenorphine, codeine, fentanyl, hydromorphone, methadone, morphine, oxycodone, and tramadol. Opioids are used in varying doses (generally based on body weight for paediatric patients) by means of parenteral, transmucosal, transdermal, or oral administration (immediate release or modified release). To achieve adequate pain relief in children using opioids, with an acceptable grade of adverse effects, the recommended method is a lower dose gradually titrated to effect in the child.

OBJECTIVES

To assess the analgesic efficacy and adverse events of opioids used to treat chronic non-cancer pain in children and adolescents aged between birth and 17 years, in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Library, MEDLINE via Ovid, and Embase via Ovid from inception to 6 September 2016. We also searched the reference lists of retrieved studies and reviews, and searched online clinical trial registries.

SELECTION CRITERIA

Randomised controlled trials, with or without blinding, of any dose and any route, treating chronic non-cancer pain in children and adolescents, comparing opioids with placebo or an active comparator.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. We planned to use dichotomous data to calculate risk ratio and number needed to treat, using standard methods. We assessed GRADE (Grading of Recommendations Assessment, Development and Evaluation) and planned to create a 'Summary of findings' table.

MAIN RESULTS

No studies were eligible for inclusion in this review. We rated the quality of the evidence as very low. We downgraded the quality of evidence by three levels due to the lack of data reported for any outcome.

AUTHORS' CONCLUSIONS

There was no evidence from randomised controlled trials to support or refute the use of opioids to treat chronic non-cancer pain in children and adolescents. We are unable to comment about efficacy or harm from the use of opioids to treat chronic non-cancer pain in children and adolescents.We know from adult randomised controlled trials that some opioids, such as morphine and codeine, can be effective in certain chronic pain conditions.This means that no conclusions could be made about efficacy or harm in the use of opioids to treat chronic non-cancer pain in children and adolescents.

Paracetamol and morphine for infant and neonatal pain; still a long way to go?

INTRODUCTION

Pharmacologic pain management in newborns and infants is often based on limited scientific data. To close the knowledge gap, drug-related research in this population is increasingly supported by the authorities, but remains very challenging. This review summarizes the challenges of analgesic studies in newborns and infants on morphine and paracetamol (acetaminophen). Areas covered: Aspects such as the definition and multimodal character of pain are reflected to newborn infants. Specific problems addressed include defining pharmacodynamic endpoints, performing clinical trials in this population and assessing developmental changes in both pharmacokinetics and pharmacodynamics. Expert commentary: Neonatal and infant pain management research faces two major challenges: lack of clear biomarkers and very heterogeneous pharmacokinetics and pharmacodynamics of analgesics. There is a clear call for integral research addressing the multimodality of pain in this population and further developing population pharmacokinetic models towards physiology-based models.

Exposure to Early Life Pain: Long Term Consequences and Contributing Mechanisms

From an evolutionary perspective, adaptations of an organism to its early environment are essential for survival. The occurrence of early life perturbation, coincident with increased developmental plasticity, provides a unique opportunity for such adaptations to become programmed and persist throughout life. However, adaptations that are beneficial to maintaining homeostasis in one's early environment may result in extreme response strategies that confer vulnerability or dysfunction later in life. This review summarizes recent findings in human and animal studies demonstrating that early life pain results in a hypo-/hyper-sensitive phenotype in response to acute and persistent pain and stress later in life. Changes in cognition and immune function in response to early life pain have also been observed. Recent data on the neural mechanisms underlying these long-term changes are discussed, as well as potential strategies to minimize the impact of early life pain.

Sedation in Critically Ill Children with Respiratory Failure

This article discusses the rationale of sedation in respiratory failure, sedation goals, how to assess the need for sedation as well as effectiveness of interventions in critically ill children, with validated observational sedation scales. The drugs and non-pharmacological approaches used for optimal sedation in ventilated children are reviewed, and specifically the rationale for drug selection, including short- and long-term efficacy and safety aspects of the selected drugs. The specific pharmacokinetic and pharmacodynamic aspects of sedative drugs in the critically ill child and consequences for dosing are presented. Furthermore, we discuss different sedation strategies and their adverse events, such as iatrogenic withdrawal syndrome and delirium. These principles can guide clinicians in the choice of sedative drugs in pediatric respiratory failure.

The long-term impact of early life pain on adult responses to anxiety and stress: Historical perspectives and empirical evidence

Approximately 1 in 6 infants are born prematurely each year. Typically, these infants spend 25 days in the Neonatal Intensive Care Unit (NICU) where they experience 10-18 painful and inflammatory procedures each day. Remarkably, pre-emptive analgesics and/or anesthesia are administered less than 25% of the time. Unalleviated pain during the perinatal period is associated with permanent decreases in pain sensitivity, blunted cortisol responses and high rates of neuropsychiatric disorders. To date, the mechanism(s) by which these long-term changes in stress and pain behavior occur, and whether such alterations can be prevented by appropriate analgesia at the time of insult, remains unclear. Work in our lab using a rodent model of early life pain suggests that inflammatory pain experienced on the day of birth blunts adult responses to stress- and pain-provoking stimuli, and dysregulates the hypothalamic pituitary adrenal (HPA) axis in part through a permanent upregulation in central endogenous opioid tone. This review focuses on the long-term impact of neonatal inflammatory pain on adult anxiety- and stress-related responses, and underlying neuroanatomical changes in the context of endogenous pain control and the HPA axis. These two systems are in a state of exaggerated developmental plasticity early in postnatal life, and work in concert to respond to noxious or aversive stimuli. We present empirical evidence from animal and clinical studies, and discuss historical perspectives underlying the lack of analgesia/anesthetic use for early life pain in the modern NICU.