Thursday September 2 2010
Babies have a heel prick test before they are eight days old
“Newborn babies should not be given sugar as pain relief,” read the headline in The Guardian. The newspaper said the routine use of tiny amounts of sugar before minor medical procedures is common practice but “it does not work and may damage their brains”.
Current medical guidelines recommend that babies swallow sucrose (sugar) solution before minor hospital procedures, such as the newborn heel prick blood test, as sugar solution is safe and effective at reducing pain they will feel.
The conclusions of this small study (44 babies analysed from 59 recruited for the study) directly challenge existing medical practice, with the finding that sugar did not reduce pain measured by looking at brain activity in response to a heel prick. Previous studies had all looked for a change in the baby's facial expression to know when the baby was in pain, rather than looking directly at brain activity. This method of measuring pain in babies may be more objective than interpretations of facial expressions, but more research is needed to prove this.
The study itself did not find that using sugar was associated with any ‘damage to newborn brains’, instead it explained that pain itself may affect a developing brain. If the lack of effect of sugar is confirmed in larger studies, then it can no longer be thought of as an effective pain relief drug for small babies.
Where did the story come from?
The study was carried out by a researcher from the Nuffield Department of Anaesthetics at the University of Oxford, along with colleagues from University College London and Great Ormond Street Hospital for Children all in the UK. The study was supported by the Medical Research Council and published in the peer-reviewed medical journal The Lancet.
Several other newspapers including the Mail and the Mirror also covered this story and reported it fairly. They focused on the fact that pain may cause short or long-term adverse effects on the development of the infant brain and suggested that if sugar is merely a distraction, then hugs or breastfeeding may work just as well.
What kind of research was this?
All babies have a heel prick blood test before they are eight days old to test for a variety of conditions. Currently, it is recommended that babies swallow sucrose (sugar) solution before the test to reduce any pain they may feel. Previous studies, including a systematic review of 44 studies, have suggested that sugar solution is safe and effective for reducing pain from minor hospital procedures.
In this double-blind, randomised controlled trial, the researchers wanted to find out if the sugar solution was actually reducing pain in the babies. The researchers explain that trials of pain relief in small babies are a challenge as the usual ways of reporting pain in clinical trials, such as asking for a description of the pain or using pain relief charts, cannot be used in babies. Usually in studies with babies, an observational pain score (premature infant pain profile - PIPP) is used. This combines video recordings made of the babies facial expressions (grimacing), as well as behavioural and physiological measures, such as oxygen use.
This study used an electroencephalography (EEG) cap to measure the electrical activity in the brain in response to pain as well as the usual PIPP response. The researchers monitored the brain activity of the babies during the heel prick test to look for a particular pattern of pain-specific brain activity, to see if the sugar solution caused a reduction in the pain response.
Care was taken to ensure no one involved in the study knew which babies had received which intervention.
What did the research involve?
The researchers carried out their study from February 2009 to March 2010. The participants were all healthy newborn infants born at 37-43 weeks of pregnancy and were less than eight days old when tested.
The researchers excluded babies from the study if they showed signs of tissue damage on the lower limbs, had previous surgery, serious illness or were born to diabetic mothers or opioid users. The babies were randomly assigned to receive either 0.5mL of 24% of sucrose solution or an equivalent volume of sterile water on the tongue.
A non-painful control stimulus was used first in all babies. The heel prick device was placed on the heel but the blade did not puncture the skin. The solution was then placed on the tongue two minutes before the actual heel prick took place.
Recording electrodes were positioned on the scalp to record the EEG, using the EEG cap. The researchers also used videos to record the behaviour and the facial expressions of the infants along with heart rate and oxygen levels in the blood and reflex movements of the limbs during the heel prick.
The researchers analysed the results on 20 out of 29 from the sucrose group and 24 out of 30 allocated to the sterile water group. The dropouts were mainly due to technical failure of the EEG, for example because of excessive movement. Only one parent withdrew consent in the sterile water group.
What were the basic results?
The measure of brain activity after the painful heel prick did not differ significantly between infants who received sucrose: mean 0.1 (95% Confidence Interval [CI] 0.04 to 0.16) compared with those who received sterile water: mean 0.08 (95% CI 0.04 to 0.12) p=0.46.
The PIPP score, a combined measure of heart rate, oxygen levels and facial expression (grimacing) scored from the video, was significantly lower in infants given sucrose compared with those given sterile water. Furthermore, significantly more infants had no change in facial expression after sucrose administration; 7 of 20 given sterile water (35%) compared with none of 24 given sucrose (p<0.0001).
How did the researchers interpret the results?
The researchers say that oral sucrose does not significantly affect activity in neonatal brain or spinal cord pain circuits, and therefore might not be an effective pain reliever.
They say that the ability of sucrose to reduce the PIPP scores observed in newborn infants after a painful event should not be interpreted as pain relief.
This study has used objective measures of pain in a small sample of infants and used careful blinding and randomisation to reduce bias. There are a few limitations due to the study size, but the conclusions are likely to challenge the currently held belief that sugar is an effective treatment for the pain of minor procedures in infants. The limitations mentioned by the researchers were:
- The small sample size of 44 infants analysed, which could mean that this study was not powered to observe subtle effects that sucrose might have on the brain processes used for pain.
- A measure of pain in infants is necessarily indirect (because they cannot describe the sensation), and so even though the electrophysiological measures reported in this study are more objective it is not clear that they are measuring the conscious pain experience of the newborn infant.
- The significant reduction of PIPP scores with sucrose confirm the results of the systematic review that looked at this as their main outcome.
- The drop out of 15 infants (25% of those recruited) may have affected the reliability of the results.
The study itself had not identified harms associated with the use of sugar and it is an extrapolation to suggest that the use of sucrose for newborn pain relief ‘may damage their brains’. This may be particularly alarming for parents or doctors to read and is not a finding of this study. There is growing evidence that some newborns’ experience of pain may have lasting adverse effects on their neurodevelopment but to state this in a way that suggests that a study has shown that using sugar causes damage to newborn brains is unhelpful.
The researchers suggest that this single-centre trial should be repeated in a larger sample of infants, and that the new EEG measurement method should be used to test the effect of other known pharmacological analgesic drugs, such as morphine. This seems like sensible advice.