Scientists gauge pain in premature babies

Apr 6 2006

Scientists at UCL (University College London) have measured responses to pain in the brains of premature babies and have shown that they are likely to experience ‘true’ pain rather than simply displaying reflex reactions.

The paper, published in The Journal of Neuroscience, illustrates that routine care procedures for premature babies, such as heel-lancing for blood tests, can cause pain in premature infants. This study, undertaken on infants in the neonatal unit at the Elizabeth Garrett Anderson and Obstetric Hospital, is the first direct scientific measure of pain in premature babies.

Professor Maria Fitzgerald, UCL Department of Anatomy and Developmental Biology, who led the team, said: “The uncertainties regarding pain management in preterm infants have been increasingly highlighted in recent years and there is a lack of basic information about effective methods of pain control in the youngest patients. As a result, while considerable effort is made to provide clinical pain-control in babies undergoing invasive procedures, this remains suboptimal in many units.

Until now, there has been limited information about pain in premature babies because measuring pain in pre-verbal children is difficult. While previous research shows that even the youngest newborn infants are capable of displaying behavioural, physiological and metabolic signs of pain and distress, the measures are all indirect and could be dismissed as bodily reflex reactions, rather than measures of true pain experience.”

Brain scans taken while babies were having blood tests registered a surge of blood and oxygen in the sensory area in babies’ brains, which indicates that the pain was processed in the higher levels of the brain. The somatosensory cortex is involved in processing sensations from the body surface and is known to be linked to pain sensation in adults.

The results were found using near-infrared spectroscopy, which - like fMRI scans - works by measuring blood levels and oxygenation in the brain. During clinical care work, essential for ensuring a premature baby’s stability, eighteen babies aged between 25 and 45 weeks from conception were studied. Scientists registered the brain activity in the babies at the moments before, during and after nurses performed routine blood tests using a heel lance.

Professor Fitzgerald added: “The importance of this is clear. The UK has the highest rate of low birth-weight babies in Western Europe; 12% all babies born need some level of special care at birth (~ 80,000 per annum) and 2.5% need neonatal intensive care (~ 17,000 per annum). Estimates show that in intensive care each baby is subjected to an average of 14 procedures per day, many of which are considered by clinical staff to be painful, such as heel lancing for blood tests and inserting chest tubes. Furthermore there is evidence that these repeated painful procedures are a significant stressor and lead to increased sensitivity to other non-painful procedures. Since pain information is transmitted to the preterm infant cortex from 25 weeks there is the potential for pain experience to influence brain development from a very early age as the brain is highly malleable at this stage of development.”

The study was funded by the Wellcome Trust London Pain Consortium and the UCLH Special Trustees.

Key facts (from the premature baby charity: Bliss)

• There are approximately 255 units in the UK offering neonatal intensive care, high dependency or special care.
• Only 20 per cent of hospital units specializing in neonatal care in the UK have a procedure for managing pain in premature babies.
• Premature baby: Born before 37 weeks
  • Moderately premature baby: Born between 35 and 37 weeks
  • Very premature baby: Born between 29 and 34 weeks
  • Extremely premature baby: Born between 24 and 28 weeks
  • Low birthweight baby: Weighs less than 2,500g (5.5 lbs)
  • Very low birthweight baby: Weighs less than 1,500gms (3.0 lbs)
• The UK has the highest rate of low birthweight babies in Western Europe. Source: Birth Counts, statistics of pregnancy and childbirth Volume 2
• NHS hospital deliveries in England by birthweight (2003-4) - singletons: Number of births between 1,000 gms - 2,499 gms: 39,000
• NHS hospital deliveries in England by gestation (2003-4) - singletons: Estimated Number of births from 22 to 36 weeks: 42,500
• Babies born at 25 weeks have a 50 per cent chance of survival.