Pain should be assessed routinely and regularly, before and after surgery, including in the recovery room, using standardized and validated and patient-appropriate scales. Static (at rest) and dynamic (e.g. when coughing or sitting) components of pain should be assessed, before and after treatment. The results of the assessments should be plotted in the patient's chart ANZCA, Chapter 2, p 34;FRENCH 4.1.2, p 404.

Assessment of pain assists in diagnosis of the cause of a patient's pain, helps to select appropriate therapy, to evaluate the therapy and assess whether it is necessary to modify it. Regular assessment of pain may lead to improved acute pain management. ANZCA Section 2.2, p 35.

While not always possible in acute pain setting, a complete pain history can help to distinguish between the different types of pain, nociceptive (somatic and visceral) vs. neuropathic pain as the likely duration of pain, management and response to analgesic strategies may vary between the different conditions ANZCA Chapter 2, Table 2.1 p 35.

Assessment in healthy adults

As pain is a subjective experience and there are no neurophysiologic or laboratory tests to measure it, self-report should be the means for assessing pain in patients who communicate freely. If used properly, self-report measures provide sensitive and consistent results. ANZCA Section 2.2, p 35 -36.

Measures for assessing pain fall under two main categories: uni-dimensionalANZCA Section 2.2.1 p 36 -38, measuring pain intensity, used mainly for acute pain and multi-dimensional, for assessing chronic and cancer-related pain. ANZCA Section 2.2.3, p 38-39.

Uni-dimensional scales include. (i) Category pain scales (CPS) use words to describe the magnitude of pain (or degree of pain relief). Common descriptors are none, mild, moderate, severe, excruciating or agonizing pain. (ii) Numerical rating scales (NRS) have both verbal and written forms. Patients rate intensity of their pain between '0' to '10'. '0' represents having 'no pain' and '10' the 'worst pain imaginable'. Most adults can rate their pain using a verbal numeric scale. It is recommended that 'no pain' is represented as '0' rather than '1'. (iii) Visual Analogue Scale (VAS), consists of a 100 mm horizontal scale with verbal anchors at both ends, the patient is asked to mark the degree of pain on this continuum. The VAS requires more concentration than the CPS or NRS, and might be unusable in up to 26% of adult patients. ANZCA Section 2.2.1 p 36 -38.

A value of 4 or higher is typically used as a threshold to guide clinical intervention ANZCA Section 2.2.1 p 37.

Uncontrolled pain should always trigger reassessment of the diagnosis and assessment whether surgical or other complications are developing, including presence of neuropathic pain and review by a specialist or Acute Pain Service personnel, if possible. ANZCA section 2.2. p 36.

Patients with special needs

As pain is identified principally through self-report, patients who have difficulty communicating, are at particular risk for under-treatment and assessment of their pain requires special attention. Those at risk include young children, people who speak a different language from the clinician's or come from a different culture, some older people; cognitively impaired or severely emotionally disturbed patients ANZCA section 2.2.4 p 39,ASA Section VI Sub-populations, 2. Geriatric, 3. Other Groups

In cognitively intact, non-communicating patients, auxiliary measures of behaviour such as restlessness, frowning and grimacing or sounds correspond reasonably well with patient self-report. However, these behaviours are not always valid indicators of pain in the non-verbal adult and can be difficult to interpret ANZCA section 11.2.3, p 402.

Elderly Self assessment scales, category or verbal rating scales, and Faces Pain Scales can be used reliably in most older patients with mild-moderate cognitive impairment and in a significant number of patients with severe impairment. A trial of different scales might be needed and patients might need more time to understand and respond to the questions. Reports of immediate pain might be accurate and valid as those of cognitively intact people. Recall of past pain might be less reliable ANZCA Chapter 11, p 401-402.

Pain assessment and therapy should be integrated into the perioperative care of elderly patients. Extensive and proactive evaluation and questioning may be necessary to overcome barriers that hinder communication regarding unrelieved pain ASA VI Sub-populations, 2. Geriatric patients.

Cognitively impaired patients are just as likely to experience pain as cognitively intact patients of the same age but the number of pain complaints and reported pain intensity decreases with increase in impairment. Cognitively impaired patients are more likely to receive less treatment of pain compared to cognitively intact patients (AUS p 405). Observations of facial expressions and sounds may be accurate measures of the presence of pain but not pain intensity in patients with advanced dementia. ANZCA chapter 11.2.3. p 400-401.

Difficulty in communicating due to cultural or language barriers These patients should be identified and may require additional interventions to assure adequate perioperative pain management ASA VI Sub-populations, 3.Other groups

Summary

There is evidence that regular assessment of pain after surgery leads to improved outcomes. Self-report should be used whenever appropriate and attempts should be made to use scales that are appropriate to the needs and capabilities of individual patients. After surgery, pain should be assessed at rest and related to movement, in or out of bed. Uncontrolled or un-expected pain requires re-assessment.

Supplementary Reading

1. The Revised Facial Scale and instructions of how to use in many languages can be found in the IASP website, under ‘Resources'.
2. Srikandarajah S, Gilron I. Systematic review of movement-evoked pain versus pain at rest in postsurgical clinical trials and meta-analyses: a fundamental distinction requiring standardized measurement. Pain. 2011 Aug; 52 (8):1734-9.