The relationship between age and morphine infusion rate in children

Pharmacokinetic Pharmacodynamic Modelling Contributions to Improve Paediatric Anaesthesia Practice

The use of pharmacokinetic-pharmacodynamic models has improved anaesthesia practice in children through a better understanding of dose-concentration-response relationships, developmental pharmacokinetic changes, quantification of drug interactions and insights into how covariates (e.g., age, size, organ dysfunction, pharmacogenomics) impact drug prescription. Simulation using information from these models has enabled the prediction and learning of beneficial and adverse effects and decision-making around clinical scenarios. Covariate information, including the use of allometric size scaling, age and consideration of fat mass, has reduced population parameter variability. The target concentration approach has rationalised dose calculation. Paediatric pharmacokinetic-pharmacodynamic insights have led to better drug delivery systems for total intravenous anaesthesia and an expectation about drug offset when delivery is stopped. Understanding concentration-dependent adverse effects have tempered dose regimens. Quantification of drug interactions has improved the understanding of the effects of drug combinations. Repurposed drugs (e.g., antiviral drugs used for COVID-19) within the community can have important effects on drugs used in paediatric anaesthesia, and the use of simulation educates about these drug vagaries.

The Society for Pediatric Anesthesia recommendations for the use of opioids in children during the perioperative period

Opioids have long held a prominent role in the management of perioperative pain in adults and children. Published reports concerning the appropriate, and inappropriate, use of these medications in pediatric patients have appeared in various publications over the last 50 years. For this document, the Society for Pediatric Anesthesia appointed a taskforce to evaluate the available literature and formulate recommendations with respect to the most salient aspects of perioperative opioid administration in children. The recommendations are graded based on the strength of the available evidence, with consensus of the experts applied for those issues where evidence is not available. The goal of the recommendations was to address the most important issues concerning opioid administration to children after surgery, including appropriate assessment of pain, monitoring of patients on opioid therapy, opioid dosing considerations, side effects of opioid treatment, strategies for opioid delivery, and assessment of analgesic efficacy. Regular updates are planned with a re-release of guidelines every 2 years.

Difficulties with assessment and management of an infant's distress in the postoperative period: Optimising opportunities for interdisciplinary information-sharing

OBJECTIVES

The importance of accurate paediatric patient assessment is well established but under-utilised in managing postoperative medication regimens.

METHODS

Data for this case report were collected through observations of clinical practice, conduct of interviews, and retrieval of information from the medical record. This case report involving a hospitalised 1-year-old boy demonstrates the difficulties associated with assessing and managing postoperative distress, including pain and other clinical conditions related to the surgical procedure.

RESULTS

Postoperatively, there were difficulties in managing pain and an episode of over-sedation, occasioning opiate reversal with naloxone. In addition, he had decreasing oxygen saturation and increased work of breathing. X-ray showed changes consistent with either atelectasis or aspiration, and he was commenced on antibiotics. The patient experienced respiratory distress and required intervention from the medical emergency team.

CONCLUSION

This case demonstrated the importance of comprehensive assessment and careful consideration of alternative causes of an infant's distress using the results of assessment tools to aid decision-making. Communication moderates effective patient care, and more favourable outcomes could be achieved by optimising interdisciplinary information-sharing.

Oral morphine dosing predictions based on single dose in healthy children undergoing surgery

BACKGROUND

Oral morphine has been proposed as an effective and safe alternative to codeine for after-discharge pain in children following surgery but there are few data guiding an optimum safe oral dose.

AIMS

The aim of this study was to characterize the absorption pharmacokinetics of enteral morphine in order to simulate time-concentration profiles in children given common oral morphine dose regimens.

METHODS

Children (2-6 years, n = 34) undergoing elective surgery and requiring opioid analgesia were randomized to receive preoperative oral morphine (100 mcg·kg^-1 , 200 mcg·kg^-1 , 300 mcg·kg^-1 ). Blood sampling for morphine assay was performed at 30, 60, 90, 120, 180, and 240 min. Morphine serum concentrations were determined by liquid chromatography-mass spectroscopy and pharmacokinetic parameters were calculated using nonlinear mixed effects models. Current data were pooled with published time-concentration profiles from children (n = 1059, age 23 weeks postmenstrual age - 3 years) administered intravenous morphine, to determine oral bioavailability (F), absorption lag time (T_LAG ), and absorption half-time (T_ABS ). These parameter estimates were used to predict concentrations in children given oral morphine (100, 200, 300, 400, 500 mcg·kg^-1 ) at different dosing intervals (3, 4, 5, 6, 8, 12 h).

RESULTS

The oral morphine formulation had F 0.298 (CV 36.5%), T_LAG 0.45 (CV 63.6%) h and T_ABS 0.71 (CV 55%) h. A single-dose morphine 100 mcg·kg^-1 achieved a mean C_MAX 10 mcg·l^-1 . Repeat 4-hourly dosing achieved mean steady-state concentration 13-18 mcg·l^-1 ; concentrations associated with good analgesia after intravenous administration. Serum concentration variability was large ranging from 5 to 55 mcg·l^-1 at steady state.

CONCLUSIONS

Oral morphine 200 mcg·kg^-1 then 100 mcg·kg^-1 4 h or 150 mcg·kg^-1 6 h achieves mean concentrations associated with analgesia. There was high serum concentration variability suggesting that respiration may be compromised in some children given these doses.

A retrospective study of sedation and analgesic requirements of pediatric patients on extracorporeal membrane oxygenation (ECMO) from a single-center experience

INTRODUCTION

The purpose of this study is to describe the sedative and analgesic requirements identifying factors associated with medication escalation in neonates and children supported on ECMO.

METHOD

Observational retrospective cohort study in a tertiary pediatric intensive care unit from June 2009 to June 2013.

RESULTS

One hundred and sixty patients were included in the study. Fentanyl and midazolam were the first line agents used while on ECMO. Higher opiate requirements were associated with younger age (p=0.01), thoracic cannulation (p=0.002), the use of dexmedetomidine (p=0.007) and prolonged use of muscle relaxants (p=0.03). Higher benzodiazepine requirements were associated with younger age (p=0.01), respiratory failure (p=0.02) and the use of second line agents (p=0.002). One third of the patients required second line agents as adjuvants for comfort without a decrease in opiate and/or benzodiazepine requirements.

CONCLUSIONS

Providing comfort to subpopulations of pediatric ECMO patients seems to be more challenging. The use of second line agents did not improve comfort in our cohort. Prospective studies are required to optimize analgesia and sedation management in children on ECMO.

Clinical pharmacology of analgosedatives in neonates: ways to improve their safe and effective use

OBJECTIVES

To propose approaches tailored to the specific needs of neonates, such as structured product development programmes, with the ultimate goal to improve the safe and effective use of analgosedatives in these fragile patients.

KEY FINDINGS

The feasibility and relevance of a structured product development programme in neonates (optimal study design based on preliminary data; model development; internal, external and prospective evaluation; an individualized dosing regimen; long-term safety; pharmacogenetics) are illustrated for the use of morphine. Based on changes in clinical practices, similar development plans are in progress for short-acting analgosedatives such as propofol, but are in need of tailored pharmacodynamic tools to assess and quantify effects. Furthermore, for drugs like paracetamol where there is already sufficient clinical pharmacology knowledge, attention needs to be given to long-term safety aspects. Finally, new covariates such as pharmacogenetics might further improve neonatal pain management, but clearly need to be integrated with other well-established covariates like age or weight.

SUMMARY

Product development programmes for analgosedatives in neonates are needed. These programmes should be tailored to their specific needs (short-acting sedation, pain relief), should include long-term safety and should incorporate the exploration of newer covariates like pharmacogenetics.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 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; alcohol and drugs of abuse; 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.

Neonatal pain

Effective management of procedural and postoperative pain in neonates is required to minimize acute physiological and behavioral distress and may also improve acute and long-term outcomes. Painful stimuli activate nociceptive pathways, from the periphery to the cortex, in neonates and behavioral responses form the basis for validated pain assessment tools. However, there is an increasing awareness of the need to not only reduce acute behavioral responses to pain in neonates, but also to protect the developing nervous system from persistent sensitization of pain pathways and potential damaging effects of altered neural activity on central nervous system development. Analgesic requirements are influenced by age-related changes in both pharmacokinetic and pharmacodynamic response, and increasing data are available to guide safe and effective dosing with opioids and paracetamol. Regional analgesic techniques provide effective perioperative analgesia, but higher complication rates in neonates emphasize the importance of monitoring and choice of the most appropriate drug and dose. There have been significant improvements in the understanding and management of neonatal pain, but additional research evidence will further reduce the need to extrapolate data from older age groups. Translation into improved clinical care will continue to depend on an integrated approach to implementation that encompasses assessment and titration against individual response, education and training, and audit and feedback.

Opioid-sparing effects of perioperative paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs) in children

BACKGROUND AND OBJECTIVES

Perioperative pain in children can be effectively managed with systemic opioids, but addition of paracetamol or nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce opioid requirements and potentially improve analgesia and/or reduce adverse effects.

METHODS

A systematic literature search was conducted to identify trials evaluating postoperative opioid requirements in children and comparing NSAID and/or paracetamol with placebo. Studies were stratified according to design: continuous availability of intravenous opioid (PCA/NCA) vs intermittent 'as needed' bolus; and single vs multiple dose paracetamol/NSAIDs. Primary outcome data were extracted, and the percentage decrease in mean opioid consumption was calculated for statistically significant reductions compared with placebo. Secondary outcomes included differences in pain intensity, adverse effects (sedation, respiratory depression, postoperative nausea and vomiting, pruritus, urinary retention, bleeding), and patient/parent satisfaction.

RESULTS

Thirty-one randomized controlled studies, with 48 active treatment arms compared with placebo, were included. Significant opioid sparing was reported in 38 of 48 active treatment arms, across 21 of the 31 studies. Benefit was most consistently reported when multiple doses of study drug were administered, and 24 h PCA or NCA opioid requirements were assessed. The proportion of positive studies was less with paracetamol, but was influenced by dose and route of administration. Despite availability of opioid for titration, a reduction in pain intensity by NSAIDs and/or paracetamol was reported in 16 of 29 studies. Evidence for clinically significant reductions in opioid-related adverse effects was less robust.

CONCLUSION

This systematic review supports addition of NSAIDs and/or paracetamol to systemic opioid for perioperative pain management in children.