Perfusion index as a tool for acute postoperative pain assessment; In correlation with Visual Analogue Score for pain assessment

The International Association for the Study of Pain(IASP) defines pain as “As unpleasant sensory and emotional experience associated with actual or potential tissue damage , or described in terms of such damage’. Unrelieved postoperative pain can result in serious side effects that effect the respiratory system (atelectasis, retention of secretions, pneumonia), the cardiovascular system (hypertension, arrhythmias, coronary ischemia), the gastrointestinal system ( decreased bowel movement, nausea, vomiting) and the endocrinal system( increased catecholamine release). It also promotes thromboembolism by delaying mobilization. Reducing pain during surgery and preventing and managing pain postoperatively is of crucial importance in the perioperative period. The objective of pain management are to measure the severity of pain, select the appropriate analgesic and estimate the response to treatment. Pain is subjective symptom thus emotional and psychological factors may interfere with its assessment. The visual analogue score (VAS) and Numeric Rating Scale are the most common pain assessment tools used. However there are still cases of pain that remain unresolved or undertreated because the patients were unable to express themselves adequately, such as in patients with mental retardation or dementia or unconscious patients in ICUs. Perfusion index is an indirect, non invasive and continuous measure of peripheral perfusion. It is calculated by the relation between pulsatile and static blood in peripheral tissues. The changes in sympathetic nervous tone affect smooth muscle tone and can alter the level of perfusion.. Most anesthetics produce a vasodilatory effect while pain produce vasoconstriction. The PI may decrease due to increased vasomotor tone and the contraction of peripheral blood vessels when sympathetic nervous system is activated by pain. Use of adequate analgesic abolishes sympathetic stimulation and perfusion increases which may result in increased perfusion index. Few studies have been done to evaluate PI as a tool for postoperative pain assessment. So we plan to correlate PI and VAS score for pain of post operative patients to test if the perfusion index is a useful marker for objective assessment of pain management in the PACU.