Physiological correlates of painful stimulation in preterm infants

Clin J Pain. 1993 Jun;9(2):88-93. doi: 10.1097/00002508-199306000-00003.


Objective: The study investigates the physiological responses of preterm infants to procedures that are routinely performed in intensive care nurseries. Changes in heart rate, respiration rate, and oxygen saturation were examined as indicators of the level of discomfort experienced by the infant during the procedures.

Design: Clinical descriptive. Systematic observations of the infants were conducted during periods of rest as well as during routine interventions.

Setting: All observations were recorded from monitored preterm infants in the intensive care units of two urban hospitals.

Patients: Thirty-five preterm infants 24-30 weeks gestational age and weighing < 2,000 g at birth. Data were collected from all infants in the units who met the weight criterion.

Interventions: The researchers observed the infants while the intensive care nursery staff were performing routine care procedures. Observations were made during procedures that adults would consider to be painful, such as injection, heel stick, tape removal, and squeezing of the heel to induce blood flow after heel stick, as well as nonpainful procedures, such as handling, temperature taking, alcohol swabbing, patting, taping a tube, feeding, and placing a pacifier.

Main outcome measures: Heart rate, respiration rate, and oxygen saturation were recorded from infant monitors. Mean values of the three measures during procedures were compared with mean values before and after procedures.

Results: Significant differences (p < 0.001) were found among pre-, peri-, and post-procedures for all three outcome measures. Heart rate and respiration rate means were significantly (p < 0.001) higher during procedures that adults consider to be painful than in those regarded as nonpainful. Oxygen saturation was lower (p < 0.001) for painful procedures than for nonpainful procedures. Gender and infant size comparisons yielded inconclusive results.

Conclusion: The outcome measures appear to be reliable indices of preterm infant responses to painful stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Body Weight / physiology
  • Female
  • Heart Rate / physiology
  • Humans
  • Infant, Newborn
  • Infant, Premature / physiology*
  • Intensive Care Units, Neonatal
  • Male
  • Oxygen / blood
  • Pain / physiopathology*
  • Physical Stimulation
  • Posture
  • Respiration / physiology
  • Sex Characteristics


  • Oxygen