When you prick me do I not cry?

A fascinating study in the Lancet this week has suggested that a very commonly used and simple analgesic in newborn infants may not actually be preventing them from experiencing pain. The study’s authors suggest that this medicine should no longer be used routinely in newborn infants. A headline in the Guardian reads “Newborn babies should not be given sugar as pain relief”. But there are scientific, philosophical and ethical reasons why this conclusion, though possibly correct, is premature.

It used to be thought that newborn infants, like animals, did not experience pain. Yes, they cried when you pricked them, but this was merely reflex, and they did not have the necessary central processing to actually experience pain as we do. Part of this doubt lies in a formidable philosophical problem, how can we know what another being is experiencing if they can’t tell us (and perhaps even if they do tell us). Even up until the mid 1980s it was common for infants to be given no pain relief whatsoever during surgery, including open heart surgery. But in the last two decades there has been a major rethink of attitudes towards neonatal pain. The rethink was based on evidence that painful experiences in newborn infants had long-term adverse effects on brain development, and that providing analgesia (for example during surgery) improved outcome.

One extremely simple, pain relief option that is very specific to newborn infants is sucrose. Giving a small dose of sugary water to newborn infants shortly before a painful procedure like an injection or heel-prick appeared to reduce infants’ response to the pain. Using careful techniques, video-recording infants’ faces and making sure that the person who assessed the video didn’t know whether or not the infant had been given sucrose, a large number of randomized studies (more than 40) have shown that infants are less overtly distressed if they have been given sucrose compared to placebo. Infants treated with sucrose also have smaller changes in their heart rate (their heart doesn’t beat as fast), breathing rate and oxygen levels.

What was different about the new study, conducted by scientists in Oxford and London, is that as well as recording infants’ facial response to a heel prick, the researchers also measured electrical activity in the brain, and in the muscles of the leg. What they showed was that the spike of brain electrical activity that accompanies a painful stimulus was not affected by sucrose. The sugar-treated infants outwardly responded less, but they had just as big a spike in EEG activity when they had a heel prick as infants treated with water. The researchers concluded that sucrose changed the response to pain in these infants but not the experience of pain.

There are scientific questions that have been raised about the new research. In an accompanying editorial in the Lancet scientists from the US have suggested that the area of brain activity measured in the study was too small, measured for too short a period, and in too few infants. They argue that a much larger sample of infants would need to be studied to rule out an important effect on brain activity.

There are also philosophical questions. The most important of these is what we take as evidence of pain experience in newborn infants. What the study highlights is that an analgesic can work at multiple different points in the pain pathway. If I were to give you a dose of suxamethonium and then cut your skin with a scalpel, you would not cry or flinch. But that is not because this drug prevents the pain of cutting the skin. Instead it is a very effective paralytic agent that stops you from moving in response to pain, though your experience of it would be undiminished. Likewise it is possible that the reason that sucrose appears to work in newborn infants is that it prevents the pain signals in the brain from manifesting as a cry or as a heart rate response. It would be a very bad thing if we thought that we were treating newborns’ pain, but actually they were suffering just as much and couldn’t show it. Because we cannot ask newborn infants whether they feel the heel prick or not we have to be guided by indirect evidence. Which piece of evidence we take as corresponding to the experience of pain is only partly answerable by science. Should we believe the EEG or the infant’s facial response? There is a danger that we give the former more weight because it is more objective, more quantifiable, involves fancy equipment. But our confidence in this technology may be misplaced.

And then there are ethical questions. Should we, as the authors of the study suggest, stop using sucrose routinely because it may not actually be effective in relieving pain. The study authors point to the possibility of long term side effects of sucrose on babies brains. There haven’t been good, careful studies looking at the long term effects of sucrose. It is possible that sucrose, particularly if given repeatedly to very small infants, may have long term side effects, and it is possible, as this study suggests, that it doesn't actually work to relieve the experience of pain. But there is very good evidence that repeated painful procedures (which are, regretfully, both common and necessary in the care of sick newborn infants) do have a negative impact on brain development and outcome. There is considerable evidence that infants treated with sucrose appear to experience less pain. If we were to stop using sucrose routinely there is also a risk of harm to newborn infants, and at present that risk is much greater than the risk of continuing to administer sucrose.

New neuroscientific techniques offer the possibility of understanding pain pathways and the effects of analgesics to a much greater extent that previously possible. They may, in time, show us that interventions for pain that we thought were effective are not actually effective, or that patients who we thought were not in pain, are actually experiencing pain. But we must not be seduced by the new technology into ignoring the cries of infants. At least not yet.

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2 Responses to When you prick me do I not cry?

  • Dominic,

    An excellent post. And I was absolutely shocked to learn this:
    “Even up until the mid 1980s it was common for infants to be given no pain relief whatsoever during surgery, including open heart surgery.”
    The sense of moral outrage I felt was the most intense in a long while. Whether this was instinctual or a proper response I do not yet know.

    One of the things that always struck me as very odd is the prevailing assumption, as you’ve mentioned it, that unless something has “the necessary central processing to actually experience pain as we do,” it does not thereby feel pain. In my experience this kind of argument had the peculiar structure of staring from a “Not like us” premise to “Not at all” conclusion.

    The question that I always raised whenever I encountered this line of reasoning was: Well, firstly, why should there be just one kind of pain, ie the one we feel with our sophisticated neurological structures, and, second, why should it be the only one that matters? Not surprisingly, I think, these questions were never really answered to any degree of satisfaction even though they are at the heart of the position of people like the monstrous surgeons mentioned in your posting.

  • Peter Wicks says:

    Dmitri this is perhaps a bit off the topic of the post itself but I’m interested in the sentence “Whether this was instinctual or a proper response I do not yet know.”

    How are you defining “proper response” here? Put another way, what criteria, in your view, should we use in determining when a moral gut reaction should be considered as a reliable guide to taking a moral position, and when it should be ignored?

    My own position is that there is no one right answer to this question, and that morality at some level always involves a degree of choice. In particular we could choose to follow our gut reactions as they arise, without any attempt at logical processing or consistency, or we could go to the other extreme and try to construct a purely logical framework for determining our moral positions. I believe that some kind of compromise is necessary, but what precisely? This issue seems to me to lie at the heart of any discussion of ethics, and I would definitely welcome more explicit discussion of it. (There have been a few posts addressing the issue, but mostly they have seeedm to take the – in my opinion untenable – line that morality is either absolute or “flimflam”.)


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