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September 1998
Volume 62 |
Number 9
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Neonatal Pain: The Evolution of an Idea |
Doris K. Cope, M.D., Trustee
Wood Library-Museum of Anesthesiology
The International Society for the Study of Pain defines pain
as "an unpleasant experience, sensorial and emotional, associated
with tissue damage, actual or potential, described in terms of
their damage." Since prehistoric times, the emotional component
of pain or meaning of the sensory experience of pain has been
interpreted in the cultural context of the time. This has been
particularly true for infant children who are unable to articulate
their pain.
St. Augustine, in the fifth century C.E., described pain
in the newborn as thus: "All diseases of Christians are to be
ascribed to demons, chiefly do they torment the fresh baptized,
yea even the guiltless newborn infant." The Aphorisms of Hippocrates
include the axiom, "Those who are used to bearing an accustomed
pain, even if they be weak and old, bear it more easily than the
young and strong who are unaccustomed." In caring for infants
undergoing surgical procedures, an important if not the quintessential
question an anesthesiologist must answer is, "Does a neonate feel
or experience pain?"
Until the 20th century, physicians believed that children
experienced more pain than adults. In 1656, Felix Wurtz in The
Children's Book, expressed the idea that the less mature the
infant, the greater degree of pain was experienced:
"If a new skin in old people be tender, what is it you
think in a newborn Babe? Doth a small thing pain you so much
on a finger, how painful is it then to a Child, which is tormented
all the body over, which hath but a tender new grown flesh?
If such a perfect Child is tormented so soon, what shall we
think of a Child, which stayed not in the wombe its full time?
Surely it is twice worse with him."
Pain in the mid-19th century was considered very real
in the infant. Some practitioners of the day believed that the
source of pain could be localized based on the infant's response.
This theory was debunked by J. Forsyth Meigs, M.D., in his textbook,
Practical Treatise on the Diseases of Children, published
in 1853. He describes pain in infants in the following way:
"Pain may almost always be detected by the expression
of the face. It gives to the countenance various shades of expression,
according to its degree of severity, and its permanency or recurrence
at intervals. Pain in the head is said, by Dr. M. Hall, to produce
a contracted brow, pain in the belly to occasion an elevation
in the upper lip, whilst pain in the chest is chiefly denoted
by sharpness of the nostrils. I doubt, however, whether pain
in any particular organ imparts an expression to one part of
the face rather than to another ..."
In 1898, A. Jacobi's Therapeutics of Infancy and Childhood
was published and became a standard American pediatric handbook.
In the chapter, "General Therapeutics," the author cautions against
chloroform producing superficial respirations and ether anesthesia
producing a detrimental effect on kidneys and the "respiratory
organs." He certainly was aware not only of the need for anesthetic
in the newborn, but the difficulty of accomplishing it successfully:
"The difficulty in obtaining a complete narcosis
is particularly great in the newly born. The stage of excitement
is brief, the pulse becomes frequent and the pupils contract.
However, after a short time the pulse becomes slow and the pupils
dilate. The after-effects are not so inconvenient as they often
prove in the adult; children vomit less frequently and less
profusely, and certainly with greater facility and ease than
adults. They are liable to remain under the influence of the
anaesthetic a long time after an operation has been completed.
After tracheotomies, which I never performed without chloroform
unless the children were asphyxiated by carbonic acid poisoning,
the patients are apt to sleep long and undisturbed. Thus they
require a ceaseless watching until the effect has surely passed
away. Through the opened trachea, children will become under
the influence of chloroform very easily. Five or six drops on
a sponge or on some absorbent cotton held in the mouth of the
tube by means of a pair of pincers has an almost instantaneous
effect."
When did the transition in common wisdom from infants
being perceived as hyper-analgesic to hypo-analgesic occur? One
interesting possibility is that the shift occurred at the time
of the development of experimental embryology with its applications
to development of the nervous system and the experience of pain.
This theoretical framework was reinforced by the popularization
of Darwin's theories leading to the conclusion that infants and
neonates experience little pain.
In 1872, Paul Emil Flechsig, working in a laboratory in
Leipzig, noted that the myelination of nerve fibers occurred at
different rates during development and that in the newborn baby
both myelinated and nonmyelinated fibers were present with only
myelinated fibers believed to be fully functional. The conclusion
was that, biologically, newborns were not completely "wired,"
and thus, their experience of sensory input such as pain was likewise
less than completely functional.
Also in the same year, Charles Darwin, in his work, The
Expression of Emotions in Man and Animal, adamantly refused
to believe that children's facial expressions, cries and tears,
convulsive movements, and vascular and breathing changes reflected
the sensory or emotional experience of pain, but were just reflex
actions, reinforced by habit. Indeed, he said that expressions
of pain in the select tribe including "animals, children, savages,
and the insane" could under no circumstances imply the awareness
of pain. These new scientific theories based on Darwin's theories
and the anatomical and histological data from embryology were
applied to clinical practice by surgeons and neurologists.
In the late 19th century, when Darwin expressed his views,
infant mortality was high and there were very few operations in
children. With increased pediatric surgical procedures, it was
quite common, even up until the 1950s, to perform antrotomies
in the auditory canal, paracenteses, connect spermatic-cord torsions,
or even perform abdominal surgery without any anesthesia.
In the 20th century, however, the view that neonates experienced
less pain was not strongly advanced. M. Thorek, in his textbook,
Modern Surgical Technique, published in 1938, described
his views of adequate pediatric anesthesia: "Often no anesthesia
is required. A sucker consisting of a sponge dipped in some sugar
water will often suffice to calm a baby." Learning theorists pointed
to additional proof that infants did not experience pain, including:
1) the general absence of childhood memories, 2) the conviction
that infants' tracts linking the thalamus to the cortex were not
functional and 3) experimental animal data on "thalamic" animals
showing reflex activity when exposed to noxious stimuli. The practical
consequence of these advances in science resulted in undertreatment
or no treatment of pain in infants.
However, in 1952, a French neurologist, André-Thomas,
advocated caution regarding the exact function of the myelin sheath
based on studies in young animals demonstrating that nonmyelinated
fibers could be excited.
Such entrenched theory dies hard, so that as late as 1968,
surgeons L.I. Swafford, M.D., and D. Allen, M.D., contended, "Pediatric
patients seldom need medication for the relief of pain after general
surgery. They tolerate discomfort well."
The idea of infants not experiencing pain after noxious
stimuli was still prevalent in conventional wisdom as seen in
the popular press. There was no clearer demonstration of this
than in the advice given to parents circumcising their male newborns.
In 1982, Proctor and Gamble promoted Pampers to parents by providing
Expectant Parents' Information Kits, which included the statement:
"You may be surprised to learn that circumcision will not be painful
to your baby because, at this early stage of development, the
penis does not yet have functioning pain nerve endings." Mother's
Manual, published the same year, argues against local anesthesia
for circumcision: "It swells the area to the extent of making
an unsatisfactory circumcision too likely."
Medical opinion began to change in the 1980s. Studies
in neonatal pain measured behavioral, physiologic and biochemical
responses to pain. While the behavioral changes had been explained
as simple learned reflexes, the changes in physiological parameters
and O2 saturation after endotracheal intubation were
more difficult to explain. Perhaps the most convincing studies
demonstrating the real phenomenon of neonatal pain were a series
of papers, published in the late 1980s, showing the hormonal and
metabolic responses in infants undergoing surgery that were attenuated
by general anesthesia. Since that time, numerous pain scales have
been proposed to assess pediatric pain.
Today, the concept of neonatal and pediatric pain is well-established,
and the lesson to be learned by the medical community is the need
for caution in applying experimental findings in isolated animal
proposals and philosophical theorems to clinical practice. It
is ironic to note that at one time in our medical history, a simple
unlettered parent could more accurately diagnose pain in their
infant child than the most advanced experimental scientist or
state-of-the-art philosopher.
References:
- Haggard HW. Devils, Drugs and Doctors: The Story of the Science
of Healing from Medicine-Man to Doctor. London: Heinemann, 1929:281-397.
As written by AM Unruh in her article, Voices from the past:
ancient views of pain in childhood. The Clinical Journal of
Pain. 1992; 8:248.
- Chadwick J, Mann WN. The Medical Works of Hippocrates: A
New Translation from the Original Greek Made Especially for
English Readers. Oxford: Blackwell Scientific Publications,
1950:150-60. As written by AM Unruh in her article, Voices from
the past: ancient views of pain in childhood. The Clinical Journal
of Pain. 1992; 8:248.
- Ruhrah J. Pediatrics of the Past. New York: Paul B. Hoeber,
1925. As written by AM Unruh in her article, Voices from the
past: ancient views of pain in childhood. The Clinical Journal
of Pain. 1992; 8:248.
- Meigs JF. A Practical Treatise on the Diseases of Children.
Philadelphia: Lindsay and Blackiston, 1853:23.
- Jacobi A. Therapeutics of Infancy and Childhood. Philadelphia:
J. B. Lippincott Company, 1898:82.
- Darwin C. The Expression of Emotions in Man and Animals (1st
ed. 1872), L'Expression des émotions, chez l'homme et
les animaux (1st ed Fr. trans. 1874) re-ed. from 2nd Eng. edition
1890), Verviers, Ed. Complexe (1981). As written by R Rey in
her book, History of Pain. Paris: Éditions La Découverte,
1993:314.
- André-Thomas. Ontongénèse de la vie
psycho-affective et de la douleur. Affect et Affectivité.
La Douleur et les douleurs, supervised by P Alajouanine. Paris:
Masson, 1956:55. As written by R Rey in her book, History of
Pain. Paris: Éditions La Découverte, 1993:315.
- Thorek M. Modern Surgical Technique, vol. III. Montreal:
Lippincott, 1938:2021. As written by AM Unruh in her article,
Voices from the past: ancient views of pain in childhood. The
Clinical Journal of Pain. 1992; 8:249.
- André-Thomas. Études neurologiques sur le nouveau-né
et le jeune nourrisson (Neurological Study of the Newborn and
Young Infant). Paris: Masson et Cie, 1952:1. As written by R
Rey in her book, History of Pain. Paris: Éditions La
Découverte, 1993:313.
- Swafford LI, Allen D. Pain relief in the pediatric patient.
Med Clin North Am. 1968; 52:131-136. As written by AM Unruh
in her article, Voices from the past: ancient views of pain
in childhood. The Clinical Journal of Pain. 1992; 8:249.
- Expectant Parents' Information Kit. Distributed by Pampers,
Proctor and Gamble Co., Cincinnati, OH, 1982, #241-2811:22.
- Brown WR and Kane L. Routine Circumcision: A Re-Evaluation
Mother's Manual, Feb. 1982:14.
- Marshall TA, Deeder R, Pai S, et al. Physiologic changes
associated with endotracheal intubation in preterm infants.
Crit Care Med. 1984; 12:501-503. As written by T Blauer and
D Gerstmann in their article, A simultaneous comparison of three
neonatal pain scales during common NICU procedures. The Clinical
Journal of Pain. 1998; 14:40.
- Gibbons PA, Swedlow DB. Changes in oxygen saturation during
elective tracheal intubation in infants. Anesth Analg. 1986;
65:S58. As written by T Blauer and D Gerstmann in their article,
A simultaneous comparison of three neonatal pain scales during
common NICU procedures. The Clinical Journal of Pain. 1998;
14:40.
- Anand KJS, Hickey PR. Randomized trial of high-dose sufentanil
anesthesia in neonates undergoing cardiac surgery: effects on
the metabolic stress response. Anesthesiology. 1987; 67:A502.
As written by T Blauer and D Gerstmann in their article, A simultaneous
comparison of three neonatal pain scales during common NICU
procedures. The Clinical Journal of Pain. 1998; 14:40.
- Anand KJS. Hormonal and metabolic functions of neonates and
infants undergoing surgery. Curr Opin Cardiol. 1986; 1:681-689.
As written by T Blauer and D Gerstmann in their article, A simultaneous
comparison of three neonatal pain scales during common NICU
procedures. The Clinical Journal of Pain. 1998; 14:40.
- Anand KJS, Aynsley-Green A. Measuring the severity of surgical
stress in newborn infants. J Pediatr Surg. 1988; 23:297-305.
As written by T Blauer and D Gerstmann in their article, A simultaneous
comparison of three neonatal pain scales during common NICU
procedures. The Clinical Journal of Pain. 1998; 14:40.
- Anand KJS, Sippell WG, Aynsley-Green A. A randomized trial
of fentanyl anesthesia in preterm babies undergoing surgery:
effect on the stress response. Lancet. 1987; 1:243-248. As written
by T Blauer and D Gerstmann in their article, A simultaneous
comparison of three neonatal pain scales during common NICU
procedures. The Clinical Journal of Pain. 1998; 14:40.
Doris K. Cope, M.D., is Clinical Director,
Pain Evaluation and Treatment Institute, and Professor, Clinical
Anesthesiology and Critical Care Medicine, University of Pittsburgh
School of Medicine, Pittsburgh, Pennsylvania.
E-mail the author.
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