PAIN ASSESSMENT Pain is internal, subjective experience. Cannot be directly observed by others or measured by use of physiologic markers or bioassays. The assessment of pain therefore relies largely upon the use of self-report.

Pain Assessment Tools should be: Valid Reliable Ability to communicate

Types of self-report pain scales Verbal Rating Scales (VRS) Numerical Rating Scales (NRS) Visual Analog Scales (VAS)

VRS Consists of a series of adjectives or phrases. Ordered from least intense to most intense. Should span a maximus possible range of the pain experience(e.g. from no pain to extremly intense pain)

VRS

VRS The strength of the VRS include Simplicity Ease of administration Face validity More compliance in elderly Good reliability( consistency over short periods of time) Good validity ( good correlation with other measures and pain behaviors)

VRS Weaknesses VRS assumes equal intervals between adjectives Patient must be familiar with all words used, and able to find one accurately VRS is being used less often in pain outcome research

Numerical Rating Scale(NRS)

VAS Consists of a line, often 10 cm, with verbal anchors at either end Horizontal line is usually preferred VAS has often be recommended as the measure of choice for assessment of pain intensity VAS correlates with pain behaviors and VAS score do show ratio-level scoring properties.

VAS

VAS Limitations Difficult to administer to patients with motor problems Using a ruler making additional possible sources of bias or error Assessment

McGill pain Questionnaires(MPQ) Among the most widely used measures of pain MPQ is multidimensional measure of pain quality Three dimensions of the experience of pain: Sensory-discriminative Affective-motivational Cognitive-evaluative In addition the MPQ contains a Present Pain Intensity VRS (PPI) ordered from mild to excruciating. The PPI along with a VAS are also included

McGill Pain Questionnaire(MPQ)

Additional consideration Differentiating types of pain MPQ may differentiate between neuropathic and nociceptive pain PainDETECT assessment system LANSS Leeds Assessment of Neuropathic Symptoms and Signs NPQ Neuropathic Pain Questionnaire Daily Diaries are gradually becoming the standard of assessing pain related symptoms in order to minimize memory biases(one or more per day often for 1-2 weeks)

Behavioral Observation Pain is private and subjective experience. People in pain may communicate their discomfort by vocalization, facial expression, body posture, and actions. These verbal and nonverbal behaviors have been termed pain behaviors. Pain related facial expression coding system have been developed (upper lip raising, mouth opening, eye closure)

Experimental Pain Assessment Administration of standardized noxious stimulation under controlled conditions constitutes an important sub-discipline within the field of pain Thermal, mechanical, electrical, chemical, ischemic stimulation are used to induce pain. Typical parameters that are measured include pain threshold, pain tolerance, and rating of suprathreshold noxious stimuli using an NRS,VAS, or VRS.

Challenges in Special populations Children Behavioral pain rating scales for infants have been developed. An example one of the more commonly used measures is Neonatal Infant Pain Scale (NIPS) which codes the presence and intensity of six pain related behaviors: facial expression, crying, breathing, arm movement, leg movement, and arousal state. FACES scale do not require language Oucher scale do not require language Pain thermometers (vertical NRS)

Challenges in special populations Elderly Elderly make more errors in MPQ (report less pain) Recent finding suggest that a VRS produces the fewest failure response among samples of cognitively intact and cognitively impaired elderly subjects while a VAS produces the largest number. More recent research suggest that the use of behavioral pain indicators may be preferable as among with cognitive impairments.

Biases in pain measurement Clinical judgment of a patient’s pain related symptoms are likely to drive diagnostic and treatment-planning decisions. Inaccurate assessment of pain can lead to improper management, unnecessary suffering, and delay in recovery whereas overestimation of pain can lead to overtreatment, and potentially to adverse iatrogenic consequences. Underestimation of pain is common in healthcare providers and undertreatment of patient’s pain is common.