Pain Assessment

Pain Assessment Tools & Scales

1. Core Principles of Pain Assessment

Pain is inherently subjective, making self-reporting the gold standard of pain assessment whenever possible. However, the inability to communicate verbally does not negate the possibility that a patient is experiencing pain. Modern clinical guidelines (such as the PADIS guidelines) emphasize a hierarchical approach to pain assessment:

1. Attempt to obtain a self-report.
2. Search for potential causes of pain.
3. Observe patient behaviors.
4. Proxy reporting (family/caregivers).
5. Attempt an analgesic trial.

2. Unidimensional Self-Report Scales (Adults)

Used for alert, cognitively intact patients capable of translating their subjective pain experience into a measurable format.

Visual Analogue Scale (VAS)

• A 100 mm horizontal or vertical line anchored by word descriptors at each end (e.g., “No pain” at 0 mm and “Worst pain imaginable” at 100 mm). The patient marks a point on the line.

The score is determined by measuring the distance in millimetres from the “No pain” anchor.

• Numeric Rating Scale (NRS)

An 11-point verbal or written scale ranging from 0 (“No pain”) to 10 (“Worst pain imaginable”).

3. Paediatric and Non-Verbal Assessment Tools

Evaluating pain in populations unable to use the NRS requires validated behavioral and observational scales.

Wong-Baker FACES® Pain Rating Scale

• Children aged 3 years and older, and adults with mild cognitive impairment.
• Six cartoon faces ranging from a happy face (0 – “No hurt”) to a crying face (10 – “Hurts worst”).
• Clinical Pearl: The scale measures the patient’s internal feeling, not how the patient’s face actually looks. The provider must ask the child to point to the face that best represents how they feel inside.

FLACC Scale (Face, Legs, Activity, Cry, Consolability)

• Infants and children aged 2 months to 7 years, or cognitively impaired adults.
• An observational tool evaluating five domains:
• Face (0-2)
• Legs (0-2)
• Activity (0-2)
• Cry (0-2)
• Consolability (0-2)
• Scoring: Total score ranges from 0 to 10, mimicking the NRS.
• Evidence: The revised FLACC (r-FLACC) includes specific behavioral descriptors customized for children with severe cognitive or neurological impairment, making it highly reliable in complex pediatric wards.

4. Critical Care Assessment Tools (Mechanically Ventilated / Sedated)

The 2018 PADIS Guidelines strongly recommend the routine use of either the BPS or CPOT for critically ill adults who cannot self-report, to prevent ICU delerium.

Critical Care Protocol (Analgesia-First): Both BPS and CPOT must be utilized before and after any potentially painful procedure (e.g., turning, suctioning) to guide the “analgesia-first” sedation strategy (Devlin et al., 2018).

5. References & Guidelines 

1. ANZCA (Australian and New Zealand College of Anaesthetists). (2020). Acute Pain Management: Scientific Evidence (5th Edition). (Essential for the validation and clinical meaningfulness of NRS and VAS).
2. Devlin, J. W., Skrobik, Y., Gélinas, C., et al. (2018). Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU (PADIS Guidelines). Critical Care Medicine, 46, e825-e873. https://doi.org/10.1097/ccm.0000000000003299
3. Gélinas, C., Fillion, L., Puntillo, K. A., Viens, C., & Fortier, M. (2006). Validation of the Critical-Care Pain Observation Tool in adult patients. American Journal of Critical Care, 15(4), 420-427. (The seminal paper establishing CPOT).
4. Merkel, S. I., Voepel-Lewis, T., Shayevitz, J. R., & Malviya, S. (1997). The FLACC: a behavioral scale for scoring postoperative pain in young children. Pediatric Nursing, 23(3), 293-297. (The original validation of the FLACC scale).
5. Payen, J. F., Bru, O., Bosson, J. L., et al. (2001). Assessing pain in critically ill sedated patients by using a behavioral pain scale. Critical Care Medicine, 29(12), 2258-2263. (The foundational paper establishing the BPS).
6. Wong, D. L., & Baker, C. M. (1988). Pain in children: comparison of assessment scales. Pediatric Nursing, 14(1), 9-17. (The original validation of the Wong-Baker FACES scale).