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The relationship between age and morphine infusion rate in children
Author(s) -
Taylor Jonathan,
Liley Andrew,
Anderson Brian J.
Publication year - 2013
Publication title -
pediatric anesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.704
H-Index - 82
eISSN - 1460-9592
pISSN - 1155-5645
DOI - 10.1111/j.1460-9592.2012.03917.x
Subject(s) - medicine , morphine , dosing , anesthesia , retrospective cohort study , population , pediatrics , surgery , environmental health
Summary Aim: We performed a retrospective audit of intravenous morphine infusion administered to children in an effort to characterize the relationship between dose and age. Methods: A retrospective audit of morphine infusions was reviewed for a 24‐months period and included all children who received continuous intravenous nurse‐controlled morphine infusions and patient‐controlled analgesia; a population undergoing acute and elective surgical procedures, as well as medical and oncological treatments. The relationship between age and infusion rate was investigated using nonlinear mixed effects models. Results: There were 886 children whose data were acceptable for review. Morphine dose increased with age from 9.97 (CV 28%) μg·kg −1 per h in neonates. The Hill equation with an exponential of 1.5 best described these changes. Morphine rate reached 90% of its mean final rate of 22.5 (CV 167%) μg·kg −1 per h, observed in teenagers, at approximately 5 years of age. There was considerable uncertainty of this age–morphine rate profile, and the maturation half‐life of this profile was 20 months of age (CV 632%). An increase in dosing variability was observed with increasing age. Conclusions: Morphine infusions at steady‐state did not mirror clearance maturation in children nursed in our hospital. We suggest that initial infusion rates in children are started at 10 μg·kg −1 per h in neonates, 15 μg·kg −1 per h in toddlers and 25 μg·kg −1 per h in children above the age of 5 years. The large variability associated with infusion rates means that subsequent infusion rates will depend on feedback from pain scores, adjuvant medications and adverse effects.