Anesthesia was first used on children almost immediately after its discovery in 1846, but for newborns and infants, the story is disturbingly different. Throughout most of the twentieth century, babies routinely underwent surgery with little or no pain relief, based on the widespread medical belief that they could not truly feel pain. It was not until the mid-to-late 1980s that landmark research forced a reckoning with this assumption, and standard practice finally began to change.
Ether, Chloroform, and the Earliest Pediatric Surgery
When ether was introduced in 1846 and chloroform in 1847, surgeons quickly began using both agents on children. Before that, children undergoing surgery were simply held down by force. Most pediatric operations in the nineteenth century treated relatively minor conditions, and the new anesthetics were welcomed as a humane advance for patients of all ages.1Pediatric Anesthesia. Pediatric Anesthesia Older children and adolescents benefited from these developments much as adults did. But for the tiniest patients, especially newborns and premature infants, surgical practice took a very different path over the next century.
Why Doctors Believed Babies Did Not Feel Pain
For much of the 1900s, the medical establishment held that infants, and especially neonates, were incapable of experiencing pain in any meaningful way. This was not a fringe view. It was taught in medical schools, reflected in textbooks, and accepted across the profession. The reasoning rested on the idea that a baby’s brain and nervous system were too immature to process pain signals. Experiments dating back decades had tested infant responses to pinpricks and even electric shocks; when babies reacted, researchers generally dismissed those reactions as simple reflexes rather than evidence of conscious suffering.2PubMed. The infancy of infant pain research: the experimental origins of infant pain denial
Several cultural and intellectual currents fed into this denial. A Darwinian framing of children as developmentally “lower” beings, a mechanistic behaviorist view that discounted subjective experience in preverbal subjects, and an increasing emphasis on brain maturation as a prerequisite for pain perception all converged to produce a remarkably durable consensus. Anesthesiologists drew on these experimental findings to justify using little or no anesthesia for infant surgery well into the 1980s.2PubMed. The infancy of infant pain research: the experimental origins of infant pain denial
In practice, this meant that newborns undergoing even major operations, including open-heart surgery, might receive a muscle relaxant to keep them still and perhaps a light dose of nitrous oxide, but nothing approaching the level of pain control that an adult or even an older child would be given for the same procedure. The muscle relaxant paralyzed the baby, preventing movement and crying, which may have reinforced the impression that the infant was not distressed. It is difficult to overstate how routine this was. It was not a case of a few rogue practitioners; it was the standard of care.
The Research That Changed Everything
The turning point came in the 1980s, driven largely by the work of K.J.S. Anand, a young researcher who set out to measure what actually happened inside a baby’s body during surgery. In a landmark randomized trial, Anand studied premature infants undergoing a common heart-related procedure. One group received the standard regimen of the time: nitrous oxide plus a muscle relaxant. The other group received the same regimen with the addition of fentanyl, a powerful opioid painkiller.
The results were striking. Babies in the group without fentanyl showed massive hormonal stress responses: surges in adrenaline, noradrenaline, glucagon, cortisol, and other stress markers, along with sharp rises in blood sugar and lactate. Their bodies were reacting to the surgery with the full force of a system under extreme duress. Babies who received fentanyl had dramatically blunted stress responses. Even more telling, the babies who did not receive adequate pain relief had more circulatory and metabolic complications after surgery.3PubMed Central. Discovering Pain in Newborn Infants
A related study developed a scoring system to quantify surgical stress in newborns and confirmed that increasing severity of surgical procedures produced correspondingly greater and more prolonged hormonal and metabolic disruptions.4PubMed. Measuring the severity of surgical stress in newborn infants These were not reflexes. These were the same physiological alarm signals that adults produce when they are in pain, scaled to a tiny body. The data made it very hard to argue that babies were not suffering.
Public Outrage and Professional Reckoning
Anand’s research did not change practice overnight through the medical literature alone. It took public pressure. When the findings became widely known outside the medical community, the reaction was fierce. Media coverage turned what had been an obscure anesthesiology debate into a matter of broad public concern. Parents were horrified to learn what had been happening to their children in operating rooms, and the controversy ensured that the anesthetic needs of newborns could no longer be quietly sidelined.5PubMed Central. Historical roots of pain management in infants: A bibliometric analysis using reference publication year spectroscopy
Change came gradually through the 1990s. Research on infant pain surged, and by 2000, major professional organizations could no longer ignore the accumulated evidence. The American Academy of Pediatrics and the Canadian Paediatric Society jointly released a statement acknowledging that neonates do experience pain, laying out a physiological basis for pain assessment and management, and recommending that clinicians reduce neonatal exposure to painful stimuli and treat any necessary pain with safe, effective interventions.5PubMed Central. Historical roots of pain management in infants: A bibliometric analysis using reference publication year spectroscopy This marked the formal end of the era in which it was professionally acceptable to operate on babies without appropriate anesthesia.
What Untreated Pain Does to a Developing Body
The argument for proper neonatal anesthesia goes well beyond the immediate ethics of allowing an infant to suffer. Research has shown that early painful experiences have lasting physiological consequences. Painful insults in very young infants can produce changes in the central nervous system itself, as well as alterations in how the neuroendocrine and immune systems respond to stress later in life.6PubMed Central. Are there long-term consequences of pain in newborn or very young infants? The developing brain, in other words, is not simply unaware of pain and waiting to mature. It is actively shaped by painful experiences, sometimes in ways that persist.
Studies of preterm infants have reinforced this picture. Both preclinical and clinical research demonstrates adverse consequences of untreated pain and stress on the developing brain of premature babies.7PubMed Central. Neonatal pain control and neurologic effects of anesthetics and sedatives in preterm infants This is one reason why the 1980s research mattered so much: it was not only about humane treatment during surgery, but about protecting the infant’s long-term neurological development. The landmark studies of that decade showed that adequate anesthesia dramatically improved outcomes for pediatric surgical patients precisely by blunting these stress-hormone cascades.8PubMed Central. Pediatric Perioperative Stress Responses and Anesthesia
How Do You Measure Pain in Someone Who Cannot Speak?
One of the practical challenges that sustained the old denial was genuinely difficult: how do you assess pain in a patient who cannot report it? Adults can say where it hurts and rate their pain on a scale. Babies cannot, and this created a void that skeptics filled with the assumption of painlessness. Filling that void with actual measurement tools has been a major project since the 1990s.
Today, clinicians use a range of validated pain scales designed specifically for neonates. These tools combine behavioral cues like facial expression, crying, and body movement with physiological indicators such as heart rate and oxygen saturation. Among the most widely used is the Premature Infant Pain Profile, which has been revised (PIPP-R) and validated across different gestational ages and clinical settings.9The Clinical Journal of Pain. The Premature Infant Pain Profile-Revised (PIPP-R) The COVERS scale is another tool that incorporates six physiological and behavioral measures and has been validated for use in both premature and full-term newborns.10PubMed Central. COVERS Neonatal Pain Scale: Development and Validation
A recent review found that over a dozen internationally used neonatal pain assessment instruments are in active clinical use, each with somewhat different strengths depending on the clinical context.11PubMed Central. Neonatal pain assessment: Do we have the right tools? The proliferation of tools reflects both the seriousness with which neonatal pain is now taken and the genuine difficulty of the measurement problem. No single scale is considered perfect, and debate continues about which combinations of indicators are most reliable for different types of procedures and different populations of infants.
Modern Pediatric Anesthesia and Its Unique Challenges
Giving anesthesia to a baby is not simply a matter of scaling down an adult dose. Every organ system in a newborn is immature, and growth and development dramatically affect how drugs are absorbed, distributed, metabolized, and eliminated.12PubMed Central. Pharmacology related to paediatric anaesthesia A newborn’s liver and kidneys process medications differently than an older child’s or an adult’s, and the margin for error is smaller because the doses involved are tiny.
Research into how individual anesthetic agents behave in neonates continues to advance. Propofol, for example, one of the most commonly used general anesthetics, has elimination patterns in neonates that depend on both gestational age and how many days old the baby is after birth.13PubMed. Population pharmacokinetics of propofol in neonates and infants: Gestational and postnatal age to determine clearance maturation Getting the dose right requires understanding these maturational variables, which is why neonatal anesthesia has become an increasingly specialized field.
Regional anesthesia, where numbing drugs are delivered near specific nerves rather than putting the whole brain to sleep, has evolved rapidly for pediatric patients in recent years. Techniques that were originally described only for adults have been adapted for infants, and older methods like infant spinal anesthesia are experiencing a revival. A newer agent, 2-chloroprocaine, has gained popularity for prolonged local anesthetic infusions in neonates because it is broken down quickly without relying on the liver, reducing the risk of toxic buildup that can occur with other local anesthetics in very young patients.14PubMed. Fundamentals and innovations in regional anaesthesia for infants and children
The Newer Worry: Can Anesthesia Itself Harm the Developing Brain?
Once the medical world accepted that babies need anesthesia, a new question emerged: could the anesthetic drugs themselves cause harm to a developing brain? Animal studies in the early 2000s raised alarm by showing that common general anesthetics could trigger brain-cell death in young rodents and primates. This set off a wave of concern among parents and clinicians alike, and spurred several major clinical trials designed to answer the question in humans.
Two of the most important studies have been reassuring, at least for brief exposures. The GAS trial, a large international randomized study, compared general anesthesia to spinal anesthesia in infants undergoing hernia repair and found no difference in developmental outcomes at age two. The PANDA trial compared children who had received general anesthesia before age three with their own siblings who had not, and found no difference in neurocognitive outcomes.15PubMed Central. Is a short anesthetic exposure in children safe? Time will tell: a focused commentary of the GAS and PANDA trials These findings have eased the most acute fears, though researchers note that the studies focused on single, relatively short anesthetic exposures. Whether repeated or prolonged exposures carry risk remains an open question, and it is one of the reasons regional anesthesia techniques that can avoid putting a baby under general anesthesia entirely have attracted growing interest.14PubMed. Fundamentals and innovations in regional anaesthesia for infants and children
Pain Relief for Needles, Heel Pricks, and Minor Procedures
Surgery is not the only source of pain for babies in medical settings. Newborns in intensive care may undergo dozens of blood draws, heel lances, and injections during their stay. Managing pain for these routine but frequent procedures has become a field of its own.
One of the simplest and best-studied interventions is oral sucrose. A large Cochrane systematic review found high-quality evidence that giving a small amount of sucrose solution before a heel lance or blood draw reduced pain scores in both premature and full-term newborns. The effect was enhanced when combined with non-nutritive sucking on a pacifier dipped in the solution. Sucrose also helped with intramuscular injections, though it was not effective for circumcision. Reported side effects were minor and no different from control groups.16PubMed Central. Sucrose for analgesia in newborn infants undergoing painful procedures
The circumcision question is worth pausing on. It remains one of the most commonly performed procedures on newborns in some countries, and for a long time it was routinely done without any pain relief at all. Critics have pointed out that the pain-control methods sometimes offered for neonatal circumcision fall well short of what would be considered acceptable for the same surgery in an adult.17JAMA. Local Anesthesia for Infants Undergoing Circumcision While practice has improved, with dorsal penile nerve blocks and topical anesthetics now recommended, the history of circumcision without anesthesia is one of the starkest examples of how the belief that babies do not feel pain persisted in everyday medicine long after the broader debate had been settled.
When Do Pain Pathways Actually Develop?
The scientific question underlying the old debate was whether a fetus or newborn has the neural hardware to perceive pain. The answer has become more nuanced over time. One review has argued that neural pathways capable of transmitting pain signals via the thalamus are present as early as seven to eight weeks of gestation, and that cortical subplate pathways are in place by twelve weeks.18PubMed Central. Fetal Pain in the First Trimester If this is correct, the basic wiring for pain perception exists far earlier than was once assumed.
Not everyone agrees on the interpretation. A systematic review published in JAMA noted that no human studies have directly examined the development of the specific thalamocortical circuits associated with pain perception. The developmental age at which thalamic pain fibers reach the cortex has been inferred from studies of other thalamocortical connections, which may or may not develop on the same timeline as those involved in pain.19JAMA. Fetal Pain: A Systematic Multidisciplinary Review of the Evidence This is an area where the science remains genuinely unsettled: the anatomy suggests the wiring is in place early, but proving conscious pain experience in a fetus is methodologically very difficult.
What is no longer in serious dispute is that full-term and premature newborns feel pain. The hormonal, behavioral, and physiological evidence is overwhelming. The remaining debates concern the lower bounds of gestational age at which pain perception begins and whether subcortical processing can constitute a form of pain experience even before the cortex is fully connected. These are important questions for fetal medicine, but for postnatal care, the clinical question was answered decades ago.
A Global and Uneven History
The history of pediatric anesthesia is not the story of a single country. Pioneers from France, England, the United States, Romania, Canada, Spain, Italy, Brazil, Japan, and China all contributed to the development of the field.20Bailliere’s Best Practice & Research Clinical Anaesthesiology. The history of paediatric anaesthesia But access to modern neonatal anesthesia and pain management remains uneven worldwide. In well-resourced hospitals in high-income countries, neonates now receive sophisticated multimodal pain management tailored to their gestational age, weight, and organ maturity. In settings with fewer resources, the gap between what is known and what is practiced can still be wide. The tools exist, the evidence is clear, and the professional guidelines are in place. Translating all of that into consistent practice everywhere babies are born is the part of the story that is still being written.