Pain in babies, and whether babies feel pain, has been a subject of debate within the medical profession for centuries. Prior to the late nineteenth century it was generally considered that babies hurt more easily than adults."The immaturity of the nervous system affecting mostly inhibitors filters; a whole body of evidence now suggests that the pain would be increased, potentiated by reducing the segmental spinal cord controls." Dr Daniel Annequin, 1999 in french : L'immaturité du système nerveux touche plus particulièrement les filtres inhibiteurs; tout un faisceau d'arguments suggère maintenant que la douleur serait augmentée, potentialisée par la diminution de ces contrôles segmentaires médullaires. Into the 1980s, it was widely believed by medical professionals that babies could not feel pain, with medical procedures such as surgeries being regularly performed without anesthesia. It was only in the last quarter of the 20th century that scientific techniques finally established babies definitely do experience pain – probably more than adults – and developed reliable means of assessing and of treating it.
Effects There are a number of metabolic and homeostatic changes which result from untreated pain, including an increased requirement for oxygen, accompanied by a reduction in the efficiency of gas exchange in the lungs. This combination can lead to inadequate oxygen supply, resulting in potential hypoxemia. In addition, a rise in stomach acidity accompanies the stress reaction precipitated by pain, and there is a risk of aspirating this into the lungs, further endangering lung integrity and tissue oxygenation. In cases of acute, persistent pain, the metabolism becomes predominantly catabolic, causing reduced efficiency of the immune system and a breakdown of proteins caused by the action of the stress hormones. In combination, healing of damaged or infected tissue may be impaired, and morbidity and mortality increased.
The neuropsychological effect on the bonding between mother and child, on later contact with health professionals, and on personal and social psychological well-being is difficult to quantify. Research suggests that babies exposed to pain in the neonatal period have more difficulty in these areas. Professionals working in the field of neonatal pain have speculated that adolescent aggression and self-destructive behaviour, including suicide, may, in some cases, be attributed to the long-term effects of untreated neonatal pain.
Pathophysiology The present understanding of pain in babies is largely due to the recognition that the fetal and newborn unmyelinated nerve fibres are capable of relaying information, albeit slower than would be the case with myelinated fibres. At birth a baby has developed the neural pathways for nociception and for experiencing pain, but the pain responses are an immature version of that of an adult. There are a number of differences in both nerve structure and in the quality and extent of nerve response which are considered to be pertinent to understanding neonatal pain.
The nerves of young babies respond more readily to noxious stimuli, with a lower threshold to stimulation, than those of adults. A baby's threshold for sensitization is also substantially decreased, whilst the process involves a much larger area of sensitization with each trauma. The neural pathways that descend from the brain to the spinal cord are not well developed in the newborn, resulting in the ability of the central nervous system to inhibit nociception being more limited than in the adult.Howard RF. Developmental Factors and Acute Pain in Children. in Pain 2005 – An Updated Review: Refresher Course Syllabus, ed. Justins DM. IASP Press, Seattle, 2005.
There are also indication that the neonate's nervous system may be much more active than that of an adult, in terms of transforming its connections and central nerve pathways in response to stimuli. The ongoing process of neural pathway development, involving both structural and chemical changes of the nervous system, have been shown to be affected by pain events, both in the short term and potentially into adult life.
Diagnosis Some of the signs of pain in babies are obvious, requiring no special equipment or training. The baby is crying and irritable when awake, develops a disturbed sleep pattern, feeds poorly, and shows a fearful, distrustful reaction towards caregivers.
The classical International Association for the Study of Pain definition of pain This often-quoted definition was first formulated by an IASP Subcommittee on Taxonomy: It is derived from Harold Merskey's 1964 definition: "An unpleasant experience that we primarily associate with tissue damage or describe in terms of tissue damage or both." as a subjective, emotional experience that is described in terms of tissue damage, depends on the patient being able to self-report pain, which is little use in diagnosing and treating pain in babies. More significant are non-verbal responses, of which there are two kinds: gross physical movements and physiological response measurements. The former are simple direct observation, while the latter requires specific equipment to monitor blood pressure and stress hormone levels.
The cry response is increasingly important, as researchers are now able to differentiate between different kinds of cry: classed as "hungry", "angry", and "fearful or in pain".Koeslag J. The Human Lifecycle, Part 19. Development Of Communication. Division of Medical Physiology, Department of Biomedical Sciences, University of Stellenbosch. Online version Interpretation is difficult, however, depending on the sensitivity of the listener, and varies significantly between observers.
Studies have sought additional, visible and easily definable indicators of pain and in particular the high level of pain detected in babies when hungry, compared to pain levels in further developed children. Combinations of crying with facial expressions, posture and movements, aided by physiological measurements, have been tested and found to be reliable indicators. A number of such observational scales have been published and verified Even with noticeable responses from an infant, the underlying problem may be hidden. Due to the inability to speak or the side effects of the illness, it may be difficult to receive a proper diagnosis, causing infant diagnosis to be one of the hardest to do in the medical field.
An emerging method of measuring pain and stress in non-verbal infants is skin conductance measurement. Changes in skin conductance occur when the sympathetic nervous system is activated in response to pain and stress. The two major advantages of skin conductance measurement as an indicator of pain are its objectivity and the possibility of continuous monitoring.
Children and Infants' Postoperative Pain Scale The Children and Infants Postoperative Pain Scale (ChIPPS) is often used in the assessment of hospitalised babies. The scale requires no special measurements, and is therefore applicable across a wide range of circumstances.
Described in 2000 by Buttner and Finke, the scale uses a measurement of five items, each rated as 0, 1, or 2 based on the following parameters:
Item Score 0 Score 1 Score 2 CryingNoneMoaningScreaming Facial expressionRelaxed smilingWry mouthGrimacing Posture of the trunkNeutralVariableRear up Posture of the legsNeutralKickingTightened Motor restlessnessNoneModerateRestless
Total score indicates how the baby should be managed according to the scale: 0–3 No requirement for treating pain, 4–10 Progressively greater need for analgesia.
All observations, both movement and physiological, tend to decrease when pain is persistent, thus rendering the scale unreliable in acute or prolonged cases. In addition, hyperalgesia and allodynia, occur more quickly and more extensively in babies than in adults. Day to day changes in the response to a specific injury may therefore become unpredictable and variable.
Treatment Where the baby is to undergo some form of planned procedure, health professionals will take steps to reduce pain to a minimum, though in some circumstances it may be not be possible to remove all pain.
In case of illness, accident and post operative pain, a graded sequence of treatment is becoming established as standard practice. Research is making it easier and simpler to provide the necessary care, with a clearer understanding of the risks and possible side effects.
Measures not involving medication
Comforting Touching, holding, stroking, keeping warm, talking and singing/music are ways in which adults have been comforting babies since the start of human history. This way of managing pain is shared with other primates, where the actions are performed both by female and male adults. Children who are able to verbalise pain report it to be an ineffective strategy and this is assumed to also be true of babies.
While the pain of a procedure may or may not be affected, the fear is visibly reduced. This works to ameliorate the negative effects of fear in health care situations. It is, therefore, considered good practice to involve parents or care-givers directly, having them present and in contact with the baby whenever possible before a minor painful procedure, such as the drawing of blood, or prior to giving a local anaesthetic injection.
Oral stimulation Breastfeeding, the use of a pacifier and the administration of sugar orally has been proven to reduce the signs of pain in babies. Electroencephalographic changes are reduced by sugar, but the mechanism for this remains unknown; it does not seem to be endorphin mediated. As in comforting, it is unknown whether the physical pain is reduced, or whether it is the level of anxiety which is affected. However, the reduction in pain behaviour is assumed to be accompanied by a reduction in pain-related disorders, both immediate and longer term.
Oral sugar Sugar taken orally reduces the total crying time but not the duration of the first cry in newborns undergoing a painful procedure (a single lancing of the heel). It does not moderate the effect of pain on heart rate and a recent single study found that sugar did not significantly affect pain-related electrical activity in the brains of newborns one second after the heel lance procedure. Sweet oral liquid moderately reduces the incidence and duration of crying caused by immunization injection in children between one and twelve months of age.
Sensorial saturation Sensorial saturation follows a "3Ts" rule: using touch, taste and talk to distract the baby and antagonize pain. It is based on the competition of various gentle stimuli with pain transmission to the central nervous system: the so-called gate control theory of pain (proposed by Patrick David Wall and Ronald Melzack in 1965). In babies treated with sensorial saturation, a reduction in crying time and pain score were noted with respect to a control group and with respect to groups in which only oral sugar, only sucking, or a combination of the two was used. The "3Ts" stimuli (touch, talk, and taste) given throughout the painful procedure increase the well-known analgesic effect of oral sugar. Sensorial saturation has been included in several international guidelines for analgesia.http://studentmidwives.co.uk/pages/essays/006/heel%20prick%20for%20sms.doc .
Other techniques Other "old fashioned" techniques are being tested with some success. "Facilitated tucking", swaddling and "kangaroo care" have been shown to reduce the response of babies to painful or distressful circumstances, while a comprehensive technique of nursing, called "developmental care", has been developed for managing pre-term infants.
Measures involving medication
Local anaesthetics