The painful truth: A review of the clinical use of skin conductance monitoring for postoperative pain assessment

Accurate assessment of pain intensity remains a critical aspect of successful pain management. Currently, the most widely used method of assessment involves various self-report scales (Williamson & Hoggart, 2005). Self-report scales rely on a cooperative, reliable patient and therefore are of limited use with unconscious, preverbal or cognitively impaired individuals. For verbal children, there are over 30 pain scales available, each with their cognitive, social and developmental limitations (Stinson et al., 2006). In preverbal children, pain assessment relies on the use of observational scales to determine pain intensity (von Baeyer & Spagrud, 2007). Limitations of such observational scores include subjectivity, with observations easily confounded by behaviors related to fear or anxiety, and age and context specificity (procedural, postoperative, etc.). Given the numerous limitations of these observational assessments, an objective pain scale that is independent of subjective interpretation certainly sounds attractive. But is it realistic? The search for an objective measurement of pain is not new. A number of objective measures have been investigated from heart rate variability (Pomfrett, 1999) to even more sophisticated measures such as functional magnetic resonance imaging (fMRI; Wartolowska, 2011). Unfortunately, as of yet, none have been able to replace subjective self-report scales. Skin conductance monitoring has been used in a number of scientific experiments, primarily in the field of psychology (Critchley, 2002). Experiments using galvanic skin responses in order to objectively measure pain have been conducted since the 1950s (Korotkov, 1953; Nisbet et al., 1967; Pakhomov & Ivanov, 1969). A study by Savino et al. (2013) is the most recent in number of studies attempting to use the latest in skin conductance technology as an objective measure of pain. This commentary will review the clinical use of skin conductance as an objective measure of postoperative pain and discuss the current state of research as well as its limitations.