Giving an infant candy - does it work?

Motivation: In pediatrics clerkship, I have come across babies who just howl after blood draws, and one of the techniques we use is coating their pacifier with a sweet liquid.  I guess the theory is that sugar makes babies happy and must therefore counteract the pain.  But, does the sugar work?  Or, should we provide babies with analgesics instead?

Turns out that this topic has been extensively studied in newborns (with 44 RCTs!) stemming from concerns about initial pain experience on subsequent neurodevelopment, and based on subjective behavioral changes, sugar pacifies babies.  But, recent evidence suggests that neonates are perhaps too immature to link pain experience and behavior reliably.  So, does sugar really help?

Paper: Oral Sucrose as an Analgesic Drug for Procedural Pain in Newborn Infants: A Randomised Controlled Trial.  Slater, R., Cornellisen, L., et. al. Lancet, 2010 (376): 1225-1232.  http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)61303-7/abstract?rss=yes#

Method: At the University College Hospital in London, 59 full-term healthy neonates were randomized to either 0.5 mL 24% sucrose solution or 0.5  mL sterile water before receiving a heel-stick.  Before the babies received the heel-stick, they were subjected to a control non-painful stimulus by just touching the blunt end of the lancet to their heels.  The cortical response to both the control and noxious stimuli was recorded via an EEG.  The primary outcome was difference in pain-specific EEG activity in response to treatment with sugar.  Secondary outcomes were observation of facial expression and physiological changes.  Both parents and clinicians were entirely blinded to the identity of the administered solution.

Results: Because of technical difficulties of performing EEG on squirming babies and other measurement barriers, the sucrose group ultimately had 20 neonates and the control group had 24 neonates.  The two groups were not substantially different in baseline characteristics after the dropout.

There was no difference in cortical pain-specific EEG changes between the sucrose group and control group. Physiologically, there were no differences in heart rate or oxygen saturation.  However, based on facial expression, babies who received sucrose were less likely to alter facial expression to pain (35% in the sucrose group did not show any facial changes to heel-stick while all babies in the control group had facial changes like crying).

Conclusion: After this study, my conclusion is that we really don't know what babies are feeling.  The key fact that we want to understand is the subjective experience of pain in babies.  Since neonates do not talk, there is no definite gold standard.  Previously, the facial expression was used as a measure of the subjective experience.  This paper challenges that viewpoint.  There are two alternative explanations for the paper's results.  One is that the EEG is simply measuring nonciceptive input to the brain, and the facial expression is showing how the baby is processing that input.  From this perspective, relying on the baby's facial expression makes more sense.  Alternatively, the sucrose may be reflexively changing the baby's facial expression, but the pain is felt in equal intensity in the cortex.  From this viewpoint, relying on the EEG cortical response makes more sense.  Right now, I think that the only way to separate these alternative explanations is to do longer term studies to see which pain response is more closely linked with aberrant neurodevelopment.