Systematic review and meta-analysis suggest that varying prevalence of non-acute pain in critically ill infants may be due to different definitions

Aim Our aim was to quantify the prevalence of non-acute pain in critically ill infants and to identify how non-acute pain was described, defined and assessed. Methods This systematic review and meta-analysis used multiple electronic databases to search for papers published in any language to March 2018: 2029 papers were identified, and 68 full texts were screened. Studies reporting the prevalence of non-acute pain in infants younger than 2 years and admitted to critical care units were included. The extracted data included the use of non-acute pain descriptions, definitions and pain assessment tools. Results We included 11 studies published between 2002 and 2018 that comprised 1204 infants from Europe, the USA, Canada and India. They were prospective observational (n = 7) and retrospective observational (n = 1) studies and randomised controlled trials (n = 3). The prevalence of non-acute pain was 0%-76% (median 11%). Various pain assessment tools were used, and only two could be pooled. This gave a pooled prevalence of 3.7%-39.8%. A number of different descriptors were used for non-acute pain, and all of these were poorly defined. Conclusion The prevalence of non-acute pain in infants admitted to critical care units varied considerably. This could have been because all the studies used different definitions of non-acute pain.