Case of the Month #2: Acute pain assessment in a child

Published: 10/02/2021


Pain assessment is an essential part of pain management. Whenever healthcare professionals use tools to assess pain, it is important these tools are standardised within each hospital, to ensure staff are confident and competent in delivering them consistently.  In children, as with adults, the ideal assessment tool involves self-reporting. Simple unidimensional pain scales typically evaluate pain intensity however the choice of tool depends on the child’s age and cognitive development. This is to ensure the child can both understand how to use the assessment tool and also is able to express their pain experience.  

It is recognised that in the postoperative setting unidimensional pain assessment tools should not be used in isolation, rather in conjunction with an assessment of functional impairment (both self-assessed by the child and observed by parents and carers) alongside analgesic requirements. As with adults, ideally other domains of pain should be assessed such as the location and nature, psychological factors involved in the pain experience such as coping, emotional distress and family feedback.   

For an 8-year-old child being cared for on a general medical or surgical ward, who has no developmental delay or cognitive impairment, self-report tools are the recommended method for them to express the intensity of the pain they are experiencing.  Numerical skills develop between 7- and 10-years-old, with children becoming able to place things in ascending and descending order.  Furthermore at this age they have started to develop the literacy skills that allow them to interpret anchors on scales such as “worst pain”.  Scales that are reliable and valid for acute pain assessment in children include the Pieces of Hurt tool, Faces Pain Scale Revised (FPS-R), Oucher pain scale photographic and numeric scale, Wong-Baker FACES Pain Rating Scale, Visual Analogue Scale (VAS), Colour Analogue Scale (CAS) and Numerical Rating Scale (NRS-11)1.   

Appropriate self-assessment appropriate tools for an 8-year-old include the NRS-11, CAS, FPS-R and VAS.  The NRS-11, FPS-R and CAS in a recent systematic review and quality assessment study were strongly recommended for use in assessment of pain intensity in acute pain, and weakly recommended for postoperative pain intensity assessment, alongside the VAS1. The authors of this systematic review did write that this could increase to strong recommendations should future studies explore the reliability of these measures in postoperative pain.  These scales are described briefly below. 

Numerical Rating Scale (NRS-11) 

This tool commonly measures pain intensity with a number chosen between 0 and 10 from a scale where 0 anchored as no pain or hurt and 10 anchored as the worst pain or hurt you can imagine.  It has been validated across a variety of paediatric settings including to evaluate postoperative pain and can come in different formats including verbal and electronic scales. 

Coloured Analogue Scale (CAS) 

This is a modification of the 10cm horizontal VAS and is a 10cm “ruler” which starts off at 0cm as narrow and white and becomes wider and redder (to become deep red at the 10cm end).  It was designed to allow children to concretely identify variations in pain intensity, a “mechanical VAS” where a slider is moved along the length of the CAS indicating how much pain a child has.  On the reverse side is a 0-10 numerical scale to determine the number of the scale the child has moved the slider to.  This tool has mostly been validated in English and is strongly recommended to evaluate acute pain intensity in children over 8-years-old1

Faces Pain Scale Revised (FPS-R) 

This tool is composed of 6 faces that range from “no pain” to very much pain.  Children are asked to point to the face that shows how much they hurt.  Often when given a choice, in general children prefer faces scales. Again, although mostly validated in English it is strongly recommended to evaluate acute pain intensity in children over 8-years-old1

Visual analogue scale (VAS) 

This tool has a similar format in children to that used in adults.  A 100mm line or rule scale is anchored with either 0-10 or 0-100mm.  Children are asked to mark a line along its length to represent pain intensity, with 0 representing “no pain” and 100 representing “worst pain”.  This is weakly recommended for acute or postoperative pain assessment in children over 8-years-old.   

For children in paediatric intensive care, assessment of pain ideally should use self-reporting tools if the child is able to complete them, however in certain circumstances this is not possible and here the most appropriate scales are observational and behavioural scales.  In the paediatric intensive care environment recommended tools are either the COMFORT scale or the COMFORT B scale. 

The COMFORT scale was developed by Ambuel in 1992 initially for ventilated children.  It looked at 6 behavioural (alertness, calmness, muscle tone, movement, facial tension and respiratory response) and two physiological variables (hear rate and mean arterial pressure compared to baseline), each of which is scored out of five response categories, giving a total score of between 8 and 402.  It is thought to be useful to evaluate pain in children aged from newborn to adolescents who are being cared for in the Paediatric Intensive Care Unit3.  This scale was further developed into:

COMFORT-B (COMFORT behavioural) scale

A number of researchers, including van Dijk and colleagues realised that excluding the two physiological variables in the COMFORT scale did not lead to loss of information4. Furthermore for non-ventilated children, respiratory response is substituted by “crying” as a variable.  Again there are five response categories leading to a score between 3 and 30.