Britner Benoit1, Ruth Martin-Misener1, Aaron Newman1, Margot Latimer1, Marsha Campbell-Yeo1
Background: Studies reporting on outcomes of pain exposure have focused on preterm infants undergoing repeated procedures. No synthesis of outcomes of early pain exposure in full term infants has been conducted.
Aim: To conduct a systematic review and meta-analysis examining both immediate and long term consequences of early pain exposure in full term infants.
Methods: Systematic search of key electronic databases conducted to October 2015. Data were extracted and summarized narratively and quantitatively using random-effects meta-analyses. Risk of bias was scored using Cochrane risk of bias assessment tools.
Results: Of the 2049 abstracts screened, 17 were retained. All reported on the impact of previous pain on later pain response with follow-up periods ranging from 24 hours to 16 years. Six reported on infant later pain response following surgery, (n = 309), nine following acute procedures (n = 570), and two following burns (n = 70). All but three studies reported that early pain was associated with altered later pain response, with thirteen reporting heightened and one reporting reduced later pain. Two studies reported on the effectiveness of analgesic interventions in preventing pain hypersensitivity and found no effect. Heterogeneity limited meta-analysis of studies. Data from two studies reporting on pain response during venepuncture following repeated heel lancing were combined and showed no difference in visual analogue scale (VAS) score in centimeters (n = 255, MD = 3.73, 95% CI = -2.35 to 9.80) or cry duration in seconds (n = 254; MD = 20.88, 95% CI = -9.92 to 51.68). Studies generally had low to moderate risk of bias.
Conclusions: Full term infants exposed to early pain may be vulnerable to pain hypersensitivity. Consistent reporting is needed to allow for more inclusive meta-analyses. Research examining optimal analgesic interventions to prevent adverse outcomes and the impact of pain on other neurodevelopmental outcomes is warranted.