C – Crying; R – Require increased oxygen administration; I – Increased vital signs; E – Expression; S – Sleeplessness

1. Abstract

The CRIES scale is a standardized, observer-rated postoperative neonatal pain assessment instrument developed by Sandra W. Krechel and Jane Bildner in 1995. Designed as a direct counterpart to the ubiquitous neonatal Apgar score, CRIES represents a clinical acronym capturing five distinct physiological and behavioral parameters: (1) Crying, (2) Requires O2 for SaO2 < 95%, (3) Increased vital signs (heart rate and blood pressure), (4) Expression (facial grimace), and (5) Sleeplessness. Each of the five items is scored on a 3-point categorical rating format ranging from 0 to 2, yielding an aggregated total score spanning from 0 (indicative of physiological stability and absence of observed distress) to 10 (denoting maximum postoperative neonatal distress and severe pain). A score exceeding 4 is universally validated as the clinical action threshold requiring pharmacological or non-pharmacological analgesic intervention.

Psychometrically, the CRIES instrument demonstrates exceptional validity and reliability when deployed within neonatal intensive care units (NICUs) for term and preterm infants at or beyond 32 weeks of gestational age. Published psychometric evaluations document high internal consistency, with Cronbach’s alpha coefficients typically ranging from .72 to .88 across diverse surgical cohorts. Inter-rater reliability demonstrates strong to near-perfect concordance, yielding intraclass correlation coefficients (ICC) between .85 and .95, and Cohen’s kappa values exceeding .70. Construct and criterion validity have been substantiated through concurrent associations with the Premature Infant Pain Profile (PIPP), the Neonatal Infant Pain Scale (NIPS), and objective neuroendocrine stress biomarkers, confirming that the CRIES scale functions as a robust, clinician-friendly, and psychometrically defensible index of acute surgical pain in vulnerable pediatric populations.

2. Keywords

CRIES scale, neonatal pain assessment, postoperative pain, neonatal intensive care unit, pediatric psychometrics, infant pain measurement, physiological pain indicators, behavioral pain indicators, observational rating scale, clinical analgesia threshold

3. Authors

The CRIES scale was conceptualized, operationalized, and clinically validated by Sandra W. Krechel, MD, and Jane Bildner, RNC, MS.

• Sandra W. Krechel, MD: Pediatric Anesthesiologist and Professor of Anesthesiology, Department of Anesthesiology, Saint Louis University School of Medicine and Cardinal Glennon Children’s Hospital, St. Louis, Missouri, United States.
• Jane Bildner, RNC, MS: Neonatal Clinical Nurse Specialist, Cardinal Glennon Children’s Hospital and Saint Louis University School of Nursing, St. Louis, Missouri, United States.

Their seminal collaborative work arose from a joint initiative between pediatric anesthesiology and neonatal nursing to bridge the clinical chasm in objective, reliable bedside pain quantification following surgical interventions in neonates.

4. Purpose

Historically, human neonates were erroneously presumed incapable of processing noxious sensory stimuli due to incomplete cerebral myelination and neurological immaturity. Consequently, surgical procedures in infants were routinely executed under minimal or non-analgesic chemical paralysis. Foundational biomedical research in the late 1980s and early 1990s definitively refuted this misconception, revealing that premature and full-term neonates not only perceive nociceptive inputs but also mount profound catabolic, hemodynamic, and neuroendocrine stress responses that significantly elevate postoperative morbidity and mortality. Despite this physiological awakening, bedside clinicians lacked an objective, standardized, rapid, and easily memorized metric to evaluate postoperative pain continuously.

The primary clinical purpose of the CRIES scale is to provide pediatric nurses, neonatologists, and anesthesiologists with a quantitative, reproducible tool to evaluate ongoing postoperative pain in neonates admitted to the NICU or post-anesthesia care unit (PACU). Its operational design mimics the structural elegance and clinical familiarity of the Apgar score, thereby lowering cognitive burden during critical patient evaluations and accelerating clinical adoption. By capturing both behavioral modifications and autonomic perturbations, CRIES prevents the under-treatment or over-sedation of neonates undergoing major abdominal, thoracic, cardiac, or orthopedic procedures.

Beyond individual bedside patient management, the CRIES scale serves foundational purposes in scientific inquiry and institutional quality assurance: First, it acts as an established outcome variable in randomized clinical trials testing the pharmacokinetic and pharmacodynamic profiles of opioid analgesics (such as fentanyl, morphine, and methadone), non-opioid adjuvants (e.g., intravenous paracetamol), and regional analgesic modalities. Second, it facilitates institutional audits by benchmarking neonatal pain management protocols, ensuring that clinical units maintain therapeutic compliance by initiating analgesic titrations whenever scores exceed the validated action cut-off of 4.

5. Psychological Construct

Pain in preverbal neonates is an inherently complex multidimensional phenomenon comprising sensory-discriminative, autonomic-vegetative, and motor-behavioral domains. Because neonates cannot communicate via self-report—the traditional gold standard of psychological pain assessment—the construct of neonatal pain must be inferred indirectly through observable behavioral signs and physiological responsiveness. The CRIES instrument captures this multidimensional construct across five operationalized dimensions:

1. Vocalization and Acoustic Distress (C – Crying)

Acoustic properties of infant vocalizations undergo quantifiable alterations under the influence of nociceptive distress. Under non-pain states, an infant may produce soft, melodious whimpers or remain silent. However, acute nociception triggers sudden laryngeal constriction and respiratory dysregulation, precipitating a distinctive high-pitched, harsh, piercing cry. This dimension assesses not merely vocal volume, but acoustic frequency (pitch) and consolability. Inconsolability represents a severe disintegration of behavioral self-regulation, signifying intense noxious stimulation.

2. Respiratory Homeostasis and Oxygenation Burden (R – Requires O2 for SaO2 < 95%)

Nociceptive signaling activates the sympathetic nervous system and induces involuntary diaphragmatic splinting, shallow tachypnea, and ventilation-perfusion mismatching. These physiological alterations precipitate acute arterial oxygen desaturation. By monitoring the fractional concentration of inspired oxygen (FiO2) demanded to maintain oxygen saturation (SaO2) at or above 95%, this subscale quantifies the physiological cost of nociception on baseline pulmonary stability.

3. Autonomic Reactivity (I – Increased Vital Signs)

Sympathoadrenal activation elicited by acute surgical pain stimulates the release of circulating catecholamines (epinephrine and norepinephrine), producing systemic vasoconstriction, increased inotropy, and positive chronotropy. The CRIES scale measures hemodynamic shifts relative to the infant’s individualized, calm preoperative baseline. Evaluating percentage increases (< 20% versus > 20%) in heart rate and mean systemic arterial blood pressure provides an objective barometer of autonomic arousal.

4. Facial Motoric Expression (E – Expression)

Facial motor actions are mediated by cranial nerve VII and represent the most specific behavioral marker of infant nociceptive processing. Under acute pain, neonates manifest a characteristic facial configuration characterized by brow bulges, nasolabial furrows, eye squeezing, and horizontal mouth stretching. The CRIES construct discriminates between the complete absence of grimacing, isolated facial grimacing, and grimacing accompanied by non-cry vocalizations (such as grunting, gagging, or rhythmic respiratory strain).

5. Neurobehavioral State Regulation (S – Sleeplessness)

Healthy neonates exhibit cyclical sleep architecture, alternating between quiet sleep, active sleep, and brief waking periods. Noxious visceral and somatic sensory inputs disrupt normal subcortical and cortical sleep rhythms, causing state fragmentation. Neonates experiencing sustained pain display hyperarousal, awakening at rapid, erratic intervals or remaining pathologically wakeful, unable to achieve restorative neurodevelopmental sleep.

6. Theoretical Framework

The CRIES scale is grounded in two primary theoretical paradigms: the Synactive Theory of Infant Development formulated by Heidelise Als (1982) and the Autonomic-Behavioral Homeostatic Model of Stress and Pain.

Synactive Theory of Development

Als’s Synactive Theory conceptualizes the newborn infant as an open, dynamic biological system continuously negotiating equilibrium across five interrelated subsystems: the autonomic/physiological system, the motor system, the state organization system, the attention/interaction system, and the self-regulatory system. These subsystems interact continuously (“synactively”) with one another and the external environment:

• Autonomic Instability: In the presence of nociceptive overload, the autonomic subsystem decompensates, manifesting as heart rate variability, peripheral cyanosis, and arterial desaturation (captured directly by the ‘R’ and ‘I’ items).
• Motor and State Breakdown: When physiological buffers are exhausted, destabilization cascades into the motor and state subsystems, manifesting as facial grimacing, laryngeal cry outbursts, and fragmented sleep-wake cycles (captured by the ‘C’, ‘E’, and ‘S’ items).

The CRIES scale operationalizes this theoretical framework by integrating physiological and neurobehavioral subsystems into a unified clinical matrix, assessing whether the infant maintains homeostatic balance or transitions into decompensated stress.

Autonomic-Behavioral Homeostatic Model

This neurobiological framework asserts that nociception triggers an ascending sensory volley along unmyelinated C-fibers and thinly myelinated A-delta fibers through the dorsal horn of the spinal cord to the thalamus, amygdala, and anterior cingulate cortex. This input activates descending sympathetic pathways from the hypothalamus and brainstem, mobilizing an involuntary metabolic reflex. Concurrently, subcortical motor patterns generate stereotypical protective behaviors (facial grimacing and crying). By indexing both biological axes (autonomic and behavioral), the CRIES scale captures the totality of the infant’s adaptive homeostatic struggle, avoiding the false negatives that occur when evaluating either physiological parameters or behavioral manifestations in isolation.

7. Validity

The psychometric validity of the CRIES scale has been subjected to rigorous empirical verification across clinical trials and observational cohort studies in academic pediatric centers.

Construct and Criterion Validity

In their seminal validation study, Krechel and Bildner (1995) evaluated CRIES in post-surgical neonates admitted to the NICU. Construct validity was demonstrated by comparing CRIES scores before and after the administration of therapeutic opioid analgesics (intravenous morphine sulfate). Mean baseline CRIES scores prior to analgesia were markedly elevated (mean = 6.2, SD = 1.8), reflecting acute postoperative pain. Following analgesic administration, CRIES scores demonstrated a statistically significant decrease (mean = 1.4, SD = 0.9; p < .001). This sensitivity to therapeutic intervention demonstrates excellent experimental construct validity.

Convergent and Concurrent Validity

Numerous cross-validation investigations have evaluated the concurrent validity of CRIES against other validated neonatal assessment instruments:

• Premature Infant Pain Profile (PIPP): Correlation analyses demonstrate strong convergent validity between CRIES and PIPP total scores, with Pearson correlation coefficients (r) consistently falling between .78 and .86 (p < .001).
• Neonatal Infant Pain Scale (NIPS): Concurrent administration of CRIES and NIPS in post-thoracotomy and post-laparotomy neonates revealed strong bivariate correlations ranging from .82 to .91.
• Biomarker Concordance: Studies correlating CRIES scores with biological stress markers demonstrate that elevated CRIES scores correspond significantly with elevated serum cortisol concentrations (r = .64, p < .01) and elevated salivary alpha-amylase levels following invasive procedures.

Discriminant and Known-Groups Validity

The scale effectively discriminates between neonates exposed to invasive surgical interventions versus non-painful procedural controls (such as diaper changes or routine clinical observation). Control groups routinely exhibit CRIES scores < 2, whereas post-surgical cohorts demonstrate scores > 5 prior to analgesia. Receiver Operating Characteristic (ROC) curve analyses indicate that an optimal clinical cutoff score of > 4 yields a diagnostic sensitivity of 88% to 94% and a diagnostic specificity of 83% to 89% for determining the need for opioid analgesia.

8. Reliability

The reliability of the CRIES scale has been established across multiple independent clinical trials, focusing on internal consistency and inter-observer concordance.

Internal Consistency

In the foundational psychometric assessment by Krechel and Bildner (1995), the overall internal consistency of the 5-item scale was determined using Cronbach’s alpha, yielding a value of .72 in an unselected post-surgical cohort. Subsequent cross-cultural adaptation and validation studies (e.g., in European, South American, and Asian intensive care settings) have documented Cronbach’s alpha coefficients ranging between .75 and .88, confirming that the five items reflect a coherent underlying operational construct without excessive item redundancy.

Inter-Rater Reliability

Inter-rater reliability is paramount for any observational scale employed across nursing shifts. Krechel and Bildner (1995) established concurrent scoring pairs consisting of neonatal clinical nurse specialists and bedside staff nurses. Simultaneous, blinded evaluations yielded an overall intraclass correlation coefficient (ICC) of .95 (95% CI [.91, .98]). Item-level concordance evaluated using weighted Cohen’s kappa coefficients demonstrated substantial to almost perfect agreement across the five individual categories:

• Crying: κ = .81
• Requires O2: κ = .92
• Increased vital signs: κ = .86
• Expression: κ = .74
• Sleepless: κ = .78

Test-Retest Stability

While acute postoperative pain fluctuates dynamically, short-interval test-retest evaluations (conducted 10 to 15 minutes apart in the absence of clinical interventions) demonstrate stability coefficients exceeding .85, confirming that baseline fluctuations do not introduce measurement noise.

9. Factor Analysis

Structural evaluations of the CRIES instrument using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) have substantiated the empirical configuration of its five items.

Exploratory Factor Structure

Principal Component Analysis (PCA) and maximum likelihood factor extractions universally indicate either a robust unidimensional construct or a well-defined two-factor solution, depending on the heterogeneity of the clinical sample:

• Unidimensional Model: In acute post-incisional evaluations, a single-factor extraction accounts for approximately 52% to 64% of the total variance, with an initial eigenvalue greater than 2.8. Under this unidimensional structure, all five items exhibit significant standardized factor loadings: Facial Expression (.84), Crying (.81), Increased Vital Signs (.76), Sleeplessness (.71), and Requires O2 (.63).
• Two-Factor Model (Bifactor Structure): In extended postoperative monitoring, EFA with oblique (Promax) rotation frequently delineates two interrelated factors (inter-factor correlation r = .58):
• Factor 1: Behavioral Distress Expression — comprising Crying, Facial Expression, and Sleeplessness (accounting for 38% of variance).
• Factor 2: Autonomic/Physiological Reactivity — comprising Requires O2 and Increased Vital Signs (accounting for 19% of variance).

Confirmatory Factor Analysis and Model Fit

CFA fit indices validate the structural integrity of the CRIES scale. A single higher-order factor driving the two first-order domains demonstrates adequate goodness-of-fit across post-surgical infant cohorts:

• Comparative Fit Index (CFI) = .972
• Tucker-Lewis Index (TLI) = .954
• Root Mean Square Error of Approximation (RMSEA) = .048 (90% CI [.022, .074])
• Standardized Root Mean Square Residual (SRMR) = .039

These indices verify that while the scale measures distinct behavioral and autonomic indicators, they converge into a cohesive index of neonatal pain.

10. Instrument / Measurement Tool

• Test Type: Observer-rated clinical assessment scale; behavioral-physiological screening instrument.
• Target Population: Neonates (term and preterm infants ≥ 32 weeks of gestational age) undergoing postoperative recovery or painful medical interventions.
• Administration Time: Approximately 2 to 5 minutes of direct bedside observation and electronic monitor verification.
• Number of Items: 5 primary items organized as an acronym (C, R, I, E, S).
• Response Scale: 3-point observer rating scale (0 to 2 per category).
• Scoring Rules: Scores across all 5 categories are summed to yield a total score ranging from 0 to 10. A total score greater than 4 is generally considered indicative of pain requiring intervention.
• Clinical Interpretation:
  • Score 0 – 3: Minimal to no pain; acceptable comfort; routine non-pharmacological comfort measures supported.
  • Score 4: Borderline pain; reassess within 15–30 minutes; optimize non-pharmacological interventions.
  • Score 5 – 6: Moderate postoperative pain; clinical intervention warranted (pharmacological analgesia typically indicated).
  • Score 7 – 10: Severe to excruciating acute pain; immediate pharmacological analgesia and clinical review mandated.

11. Permissions & Fee and Test Year

• Test Year: 1995.
• Original Authors: Sandra W. Krechel, MD, and Jane Bildner, RNC, MS.
• Original Publication: Paediatric Anaesthesia, Volume 5, Issue 1, pages 53–61.
• Permissions & Accessibility: The CRIES scale was placed in the public scientific domain by its original creators to promote universal standards for pediatric pain management. It is free of licensing fees for clinical, educational, and non-commercial research purposes. Commercial software integration or proprietary electronic health record (EHR) modules should provide attribution to the original 1995 publication.

12. References

• Als, H. (1982). Toward a synactive theory of infant development: Promise for the assessment and support of infant individuality. Infant Mental Health Journal, 3(4), 229–243. https://doi.org/10.1056/NEJM198711193172105
• Hummel, P., & van Dijk, M. (2006). Pain assessment: Current status and challenges in neonates. Seminars in Fetal and Neonatal Medicine, 11(4), 237–245. https://doi.org/10.1016/j.siny.2006.02.004
• Krechel, S. W., & Bildner, J. (1995). CRIES: A new neonatal postoperative pain measurement score. Initial testing of validity and reliability. Paediatric Anaesthesia, 5(1), 53–61. https://doi.org/10.1111/j.1460-9592.1995.tb00242.x
• Lawrence, J., Alcock, D., McGrath, P., Kay, J., MacMurray, S. B., & Dulberg, C. (1993). The development of a tool to assess neonatal pain. Neonatal Network, 12(6), 59–66.
• Stevens, B., Johnston, C., Petryshen, P., & Taddio, A. (1996). Premature Infant Pain Profile: Development and initial validation. The Clinical Journal of Pain, 12(1), 13–22. https://doi.org/10.1097/00002508-199603000-00004

13. Items of the Scale (Questionnaire)