The relationship between age and morphine infusion rate in children

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Jonathan Taylor1, Andrew Liley, Brian J Anderson

  • 1Department of Anaesthesia, Starship Children's Hospital, Auckland, New Zealand.

Paediatric Anaesthesia
|July 12, 2012
PubMed

Insights

This study analyzed intravenous morphine infusion doses in children, finding that optimal dosing increases with age but shows significant variability. Initial infusion rates are suggested based on age groups to manage pediatric pain effectively.

Area of Science:

  • Pediatric pharmacology
  • Pain management
  • Pharmacokinetics

Background:

  • Intravenous morphine is commonly used for pediatric pain management.
  • Understanding the relationship between morphine dose and age is crucial for safe and effective analgesia in children.
  • Previous studies have not fully characterized age-specific morphine infusion rates in diverse pediatric populations.

Purpose of the Study:

  • To characterize the relationship between intravenous morphine infusion dose and age in pediatric patients.
  • To establish age-based guidelines for initiating morphine infusions in children.
  • To investigate the variability in morphine dosing across different pediatric age groups.

Main Methods:

  • Retrospective audit of 886 children receiving continuous intravenous morphine infusions over 24 months.
  • Inclusion of patients undergoing surgical, medical, and oncological treatments.
  • Application of nonlinear mixed effects models to analyze the relationship between age and infusion rate.

Main Results:

  • Morphine dose increased with age, starting at 9.97 μg·kg⁻¹·h⁻¹ in neonates and reaching a mean final rate of 22.5 μg·kg⁻¹·h⁻¹ in teenagers.
  • The Hill equation with an exponential of 1.5 best described the age-related changes in morphine infusion rates.
  • Significant variability in dosing was observed, increasing with age, with a maturation half-life of 20 months.

Conclusions:

  • Steady-state morphine infusions in children do not directly mirror pharmacokinetic clearance maturation.
  • Recommended initial infusion rates: 10 μg·kg⁻¹·h⁻¹ for neonates, 15 μg·kg⁻¹·h⁻¹ for toddlers, and 25 μg·kg⁻¹·h⁻¹ for children over 5 years.
  • Subsequent morphine titration should be guided by pain scores, adjuvant use, and adverse effects due to high variability.
Abstract

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