How Well Do Clinical Pain Assessment Tools Reflect Pain in Infants?
Rebeccah Slater1*, Anne Cantarella2, Linda Franck3, Judith Meek2, Maria Fitzgerald1 1 Department of Anatomy and Developmental Biology, University College London, London, United Kingdom, 2 Neonatal Intensive Care Unit, Elizabeth Garrett Anderson and Obstetric Hospital, London, United Kingdom, 3 Centre for Nursing and Allied Health Professions Research, Institute of Child Health, University College London, London, United Kingdom
Background
Pain in infancy is poorly understood, and medical staff often have difficulty assessing whether an infant is in pain. Current pain assessment tools rely on behavioural and physiological measures, such as change in facial expression, which may not accurately reflect pain experience. Our ability to measure cortical pain responses in young infants gives us the first opportunity to evaluate pain assessment tools with respect to the sensory input and establish whether the resultant pain scores reflect cortical pain processing.
Methods and Findings
Cortical haemodynamic activity was measured in infants, aged 25-43 wk postmenstrual, using near-infrared spectroscopy following a clinically required heel lance and compared to the magnitude of the premature infant pain profile (PIPP) score in the same infant to the same stimulus (n = 12, 33 test occasions). Overall, there was good correlation between the PIPP score and the level of cortical activity (regression coefficient = 0.72, 95% confidence interval [CI] limits 0.32-1.11, p = 0.001; correlation coefficient = 0.57). Of the different PIPP components, facial expression correlated best with cortical activity (regression coefficient = 1.26, 95% CI limits 0.84-1.67, p < 0.0001; correlation coefficient = 0.74) (n = 12, 33 test occasions). Cortical pain responses were still recorded in some infants who did not display a change in facial expression.
Conclusions
While painful stimulation generally evokes parallel cortical and behavioural responses in infants, pain may be processed at the cortical level without producing detectable behavioural changes. As a result, an infant with a low pain score based on behavioural assessment tools alone may not be pain free.
Funding:
This study was funded by The Wellcome Trust, The Medical Research Council, and SPARKS. The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing interests:
The authors have declared that no competing interests exist.
Academic Editor:
A. David Edwards, Imperial College London, United Kingdom Citation: Slater R, Cantarella A, Franck L, Meek J, Fitzgerald M (2008) How Well Do Clinical Pain Assessment Tools Reflect Pain in Infants? PLoS Med 5(6): e129 doi:10.1371/journal.pmed.0050129
Received: September 24, 2007; Accepted: May 2, 2008; Published: June 24, 2008
Copyright:
© 2008 Slater et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abbreviations:
CI, confidence interval; HbT, total haemoglobin concentration; NIRS, near-infrared spectroscopy; PIPP, premature infant pain profile; PMA, postmenstrual age
* To whom correspondence should be addressed. E-mail: r.slater@ucl.ac.uk
