Pain accompanies man since birth. The capacity to feel physical suffering is the gift of nature created to protect human beings. On the other hand, in many cases, pain loses its original sense becoming needless anguish and then it should obviously be eliminated [1]. Pain management is particularly important in children. The studies conducted at the end of the previous century prove that pain is treated less effectively in children than in adults. This results from the lack of knowledge or management standards, negative attitudes of medical personnel, bad organization and bias concerning the use of opioids in children [2].

For more than the first half of the XXth century, it was believed that infants and children were less sensitive to pain and tolerated it better compared to adults; neonates were thought to have insufficient neurological and physiological maturity to perceive pain. The assessment of this sensation in infants and children, who cannot speak, was considered unscientific and subjective and pain relieving more traumatizing than leaving the child in pain untreated [3]. 

The pain-related issues were already addressed to in ancient times. Discussions on sensitivity to pain of infants, children and adults were then based on philosophical and physiological arguments. Moreover, the problem of pain assessment and measurements was considered. According to some authors, pain evaluation was infeasible; others claimed that pain could be assessed through meticulous observations. In those times, pain management in children was less controversial than in modern times, as children were believed to be capable of perceiving pain. According to ancient writers, children felt more pain than adults did. Such statements were based on philosophical perception of life sensations, pain in particular. Plato (IVth century B.C.) maintained that both suffering and pleasure resulted from the interactions between earth, fire, air and water contained in the body. He believed that at the beginning of life those interactions were particularly violent; therefore, for infants all sensations were painful [4].

Many civilizations thought that pain and illness were caused, fuelled or treated by supernatural forces depending on spiritual goodness or badness of man. It is unclear whether gods somehow distinguished adults and children.

In the Middle Ages, after the fall of the Roman Empire, it was believed again that pain and suffering were caused by angry gods or whims of demons. Some authors of that period maintained that infants were particularly sensitive in this respect. St. Augustine (Vth century A.D.) wrote that all illnesses of Christians were attributable to demons, who mostly inflicted suffering to the newly baptized, even innocent newborns [5]. The conviction about increased pain sensitivity of children also resulted from the recognition of immaturity of the youngest. Some ancient writers suggested that sensitivity to pain was partly determined by earlier pain experiences. Hippocrates (V/IVth century B.C.) wrote: „ those who are used to endure pain, even if weaker and older, cope with it better than the young and strong ones, who are not used to it “, i.e. more pain experience lessens sensitivity to pain [6].

Moreover, it was believed that sensitivity to pain resulted from self-evident physiological immaturity of small children. In 1656, Wurtz emphasized that infants were particularly sensitive to pain due to their immaturity. He also claimed that pre-term neonates were more sensitive to pain compared to full-term babies.

The assessment and measurements of pain in children were always difficult, as it was not known how children could express their pain being behaviourally, cognitively and linguistically immature. Until recently, it was assumed that children were not capable of proper evaluation of their pain, although Downman (1740-1809) believed that children demonstrated physiological and behavioural symptoms of pain understandable for physicians, e.g. changes in muscle tone, facial expression, or pulse rate [7].

Ancient authors stressed the role of a well-taken history, despite difficulties in gaining information from a child, which should include changes in behaviour suggestive of pain and physiological changes likely to indicate the source of pain.

Crying was most commonly considered a symptom of pain in children. The Ancients believed that crying was also the symptom of other forms of discomfort: boredom, hunger, loneliness. Moreover, crying was thought to be useful, a form of physical exercise. According to Soranus, the Greek physician (IInd century A.D.), crying was also the exercise for the respiratory and digestive systems; yet persistent crying could cause physical harm [8]. Galen (130-200 A.D.), Ferrarius (1577), and Wurtz (1656) emphasized that crying was the symptom of discomfort or pain and therefore some illness should be suspected. Crying, facial expression changes, activity and behaviour during sleep were interpreted by Ancient authors as manifestations of pain and some hints how to find its source [3].  Many centuries later, Starr (1895) [9] claimed that crying was not normal in a healthy child, except for a short-term reaction to injury. He described changes in facial appearance and sleep patterns as indicators of a potential pain source, e.g. the furrowed forehead was suggestive of headache while sharpened nostrils - of chest pain.

Before paediatrics became a separate branch of medicine, not much had been known about the sources of pain in children, which might be associated with illnesses, injuries, diagnostic procedures or treatment. Ancient authors most often mentioned pain during teething. Other paediatric problems described by them were colic and stomachache.  Unfortunately, the definition of colic had not been given then and it is not known whether their term “colic” was tantamount to ours. Avicenna described colic as the condition in which “an infant writhes and cries”[10]. The most widespread modern definition of colic explains that it involves inconsolable crying without any evident physical cause lasting for more than 3 h during the day for over 3 weeks [11].

The Ancient medicine used several methods to treat pain in children. The first one involved measures related to supernatural forces, e.g. prophecies in Ancient Egypt or amulets hung around the child’s neck. The red coral was used to support the digestion (Oestereicher, XVIth century A.D.), the tooth of a dead person (Ferrarius, 1577) or the timothy root, viper’s tooth, green jasper to ease the teething pain (Aetius, VIth century A.D.).

Furthermore, the attention was paid to milk of breast-feeding mothers; it was maintained that the beneficial substances given to mothers would be passed with milk to children. Milk imperfection was considered the potential cause of pain and diseases in children. The consumption of carminative foodstuffs, such as beans or peas, was forbidden.  

Another method of pain relief was based on remedies given directly to children – oral preparations, poultices and ointments placed over their skin or suppositories. Soranus suggested several pain remedies during teething, e.g. lard for sucking before teething. During teething, he recommended rubbing in chicken fat or rabbit brain. If pain persisted when the tooth had already erupted, he advised to wrap the neck of an infant with a wool band and various gingival poultices [8].

The most controversial method of treatment was opium for relieving the pain and for narcosis.  Opium was first mentioned in the Ebers Papyrus (1553-1550 B.C.), in which it is recommended as the remedy for crying babies : „ mix poppy capsules, faeces of a wasp from the wall, drain and give for 4 days; the pain will be immediately relieved” [3]. Opium was also recommended by Rhazes and Avicenna as the remedy for crying and sleeplessness in children [10]. Until the XVth century, the use of opium had been disputed. Bagellardus underlined that treatment of crying or sleeplessness should be started with milder agents due to sedative effects of opium. Harris was a staunched opponent of the use of opium in infants emphasizing that other agents might ease the pain if their doses were sufficient [12]. It is not known whether Bagellardus and Harris knew about addictive effects of opioids.

Apart from such means of pain treatment, ancient writers stated that comfort and safety provided to a child might be an element of pain management. Moreover, they considered the prevention of pain by avoiding injuries. Soranus advised caution during baths of neonates „ water whose temperature is optimal for an adult may be too hot for infants due to extraordinary delicacy of their bodies” [8]. Avicenna wrote, “pieces of sticks or other objects which are likely to pierce or cut the skin should be kept away from children [10].

At the beginning of the XXth century, it was still believed that crying was beneficial for the respiratory system. In 1908, Holt [13] maintained that a neonate should cry for 15-20 min every day to expand the lungs. At present, crying is regarded as a means to communicate basic needs; it does not have to be the symptom of pain. Some scientists believe that there is the developmental pattern of crying. Crying of a neonate is the physiological response to biological dangers such as hunger, pain, illness or injury whereas crying of older infants depends on their emotional status [14]. Moreover, the characteristic features of crying were also studied paying special attention to their possible use for identification of specific diseases and syndromes in children [15]. Crying and changes in behaviour that accompany it during sleep or otherwise were the basis of modern scales for pain measurements, e.g. the Children’s Hospital of Eastern Ontario Pain Scale [16].

Until recently, the prevailing opinion was that children felt pain less severely than adults and that newborns did not feel any pain. Some scientists and clinicians believed that a newborn had no or very slight pain experience hence did not feel the difference between pain and pleasure [17]. It was thought that sensitivity to pain increased with age as an acquired response to pain stimuli. The majority of the XXth century opinions about pain in children were based on the theory taking into consideration the philosophical conjecture that complete myelinization indispensable for functioning of nervous pathways was also necessary for feeling pain. Even if it was doubted that physiological immaturity was a sufficient explanation of insensitivity of children to pain, it was still maintained that children were more resistant to pain compared to adults. In his description of a surgical procedure in a child, Thorek [18] wrote, “anaesthesia is often not required. In many cases, a sponge soaked in the mixture of water and sugar is sufficient to calm a child”. According to Swafford and Allen [19], “paediatric patients rarely need drugs to relieve postoperative pain and tolerate discomfort well. A child says that he/she does not feel well, or feels queer and wants to be with his/her parents yet often this misfortune is not related to pain”.

In 1941, Mc Graw [20] assessed the reactions of children to pain caused by heel lance during blood sampling. She evaluated 75 children aged from several minutes to 4 years; in total, she had 2008 observations. The findings disclosed that the youngest patients aged several minutes to several days did not react to pain or their reaction was scattered; in older children, the reaction became more localized.  Mc Graw believed that the pain threshold to external stimuli was high in neonates and that they could not identify and localize the source of external pain stimulation. Her opinion was considered crucial and functioned in the medical circles for the next 30 years. The fact that her study was badly designed was neglected – the population was not divided into groups according to the clinical status of children. It was assumed that small children, who probably had no pain-related memory, did not need analgesia.

The theory that the capacity to remember pain is necessary to feel it was created in 1957. According to Jones, the mature nervous system is needed to feel pain sensations. An individual recognizes pain mentally yet cannot reconstruct it; moreover, repeated pain sensations do not provide resistance [21]. For years, the belief that small children do not need pain treatment due to their immature nervous system was supported by numerous studies. It should be noticed that pain interpretations resulted from fragmentary knowledge about the development of the nervous system. Many studies, which the then theories were based on, were conducted on animals and not humans.

Merskey [22] suggested that the pain perception by children was immature and that this ability was acquired with age. He believed that even if small children felt pain, their reaction was much weakly expressed than in adults. Merskey was a member of the interdisciplinary committee that put forward the first definition of pain: „ an unpleasant sensory or emotional experience associated with actual or potential tissue damage or described in terms of such damage. Noteworthy, pain is always subjective. Everybody learns it through experiences related to injuries in early life” [23]. This definition became the basis of every publication concerning pain in small children.

Textbooks concerning the development of man strengthened the belief that small children were not capable of feeling pain in the same way that adults were. Mc Graw made people believe that this additionally resulted from incompletely developed connections between the receptor part of the nervous system and higher nervous centres. In the third edition of “Human growth after birth” by Sinclair, it was maintained that:” a newborn…. can feel taste, smell but his/her feeling of pain is not fully developed”. In the sixth edition of this textbook (1998), however, it was written that it was not precisely known how well the pain sensation in children was developed; moreover, some experts believed that pain might be felt by foetuses [24].

Not all publications of those times included the thesis that small children were incapable of feeling the pain. In their review on the development of human brain, Sidman and Rakic [25] wrote that the cerebral cortex had a complete cell structure already by mid-pregnancy. It was then that pain was started to be perceived not from the perspective of cognitive development (requiring memory and learning) but as an anatomical and physiological issue. The concept assuming that pain perception depends of the degree of development has not been fully abandoned; more thought was given to the issue whether the nervous system was sufficiently developed to transmit and receive pain signals rather than whether children were capable of understanding their pain.

In the 80-ties of the XXth century, the scientists were united in believing that neonates felt pain but were incapable of understanding why they experienced such sensations. It was postulated that their guardians were obliged to insist on suitable pain management on their behalf, particularly that the studies carried out revealed that in some cases neonates requiring analgesia did not receive it because of the fear of serious adverse effects [26].

In 1980, Valman and Pearson [27] in their considerations „ What the foetus feels” explained that the foetus might hear and react to light coming from outside the uterus during the final weeks of pregnancy. They claimed that young foetuses once “touched” tended to escape, more mature ones headed towards the stimulus. Moreover, the authors stressed that foetuses should be deeply sedated during intrauterine procedures; e.g. intrauterine transfusions (to avoid escaping of the foetus from the needle). The foetal pulse accelerates during the first minute of the procedure and returns to the baseline value immediately after its completion. The above publication was the basis for understanding the physiological reactions associated with pain in the earliest period of human life. 

In later years, it was confirmed that foetuses were capable of showing they felt pain in the same way as adults. In 1982, Robinson and Gregory [28] emphasized that appropriate anaesthesia is indispensable in neonates undergoing surgical procedures. The other authors pointed to improperly administered postoperative analgesia in children: some of them did not receive any pain treatment; only 35% were administered opioids in therapeutic doses [29]. In the same years, it was demonstrated that local anaesthetics administered before circumcision reduced crying and pulse during the procedure [30]. In 1984, Owens [31] questioned the theory and definition of pain published earlier by Merskey. He stressed the importance of other methods to evaluate the severity of pain in cases when patients had limited capacity of verbal expression, e.g. heart rate measurements, determinations of blood cortisol levels and observations of behaviour, e.g. crying or face expression. 

Based on measurements of the length of crying and heart rate in 20 neonates aged 30-54 h in whom the blood was sampled from the heel the theory that neonates did not react or slightly react to procedures associated with tissue damage was rejected [32].

At present, there are no doubts that even the youngest children feel pain and each of them should be provided with proper, i.e. effective and safe treatment. A variety of methods of pain management is being tested. Amulets and prophecies are no longer used by physicians yet may still be a part of religious and cultural practices. The pain therapy in a neonate by treating a breast-feeding woman is rarely considered although the composition of milk and diets of breast-feeding mothers are still being thoroughly studied as the factors that are likely to cause colic [3]. Oral analgesics or analgesic suppositories, injections or ointments are the commonest methods of management. The use of opioids is widely disputed; the fear of causing addiction often veils their efficacy in pain relief although there is no evidence that children treated with opioids become addicts. Moreover, non-pharmacological psychological methods are widely applied: relaxation, cognitive visualization, family and group therapy, physical methods based on feedback or transcutaneous electrical nerve stimulation [3]]. The golden rule in pain management is pre-emptive analgesia involving the administration of analgesics before the exposure to pain stimuli [34].

The present knowledge about neurophysiology of pain, methods of pain treatment and prevention enables to provide the youngest patients with comfort of functioning without pain from the very first days of life; therefore, this knowledge should be most widely implemented in everyday practice.

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30.    Williamson PS, Williamson ML: Physiologic stress reduction by a local anesthetic during newborn circumcision. Pediatrics 1983; 71: 36-40.

31.    Owens ME: Pain in infancy: conceptual and methodological issues. Pain 1984; 20: 213-230.

32.    Owens ME, Todt EH: Pain in infancy: neonatal reaction to a heel lance. Pain 1984; 20: 77-86.

33.    Beyer J, DeGood DE, Ashley LC, Rusel GA: Patterns of postoperative analgesic use with adults and children following cardiac surgery. Pain 1983; 17: 71-81.

34.    Gottschalk A, Smith DS: New concepts in acute pain therapy: preemptive analgesia. Am Fam Physician 2001; 63: 1979-1984.

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Address:

*Emilia Pabis
Kliniczny Oddział Anestezjologii
i Intensywnej Terapii
DSK w Lublinie
ul. Chodźki 2, 20-093 Lublin
tel.: 0-81 718 53 91
e-mail: emiliapabis@wp.pl

Received: 28.11.2009
Accepted: 03.01.2010