The success of peripheral nerve blocks is usually assessed by sensory and motor function. But this method is subjective, time consuming and cannot be done in patients under deep sedation or otherwise unable to provide feedback. Various objective methods like thermographic temperature measurement, laser doppler perfusion imaging and skin electrical resistance have been developed. These methods depend on evaluation of sympathetic block and consequent physiological changes such as vasodilation, change in blood flow and skin temperature . However, most of these objective methods require sophisticated and expensive equipment.

Perfusion index (PI) is a simple, objective and non-invasive method for evaluation of the success of central neuraxial and peripheral nerve blocks. It has been shown to be useful measure to evaluate various peripheral nerve blocks. It is calculated by dividing the ratio of arterial blood flow (pulsatile) to venous, capillary, and tissue blood flow (non-pulsatile blood flow) and is shown as a percentage or absolute value. Perfusion index has been shown to help clinicians predict illness severity and early adverse respiratory outcomes in neonates, predict low superior vena cava flow in very low birth weight infants, provide an early indicator of sympathectomy after epidural anesthesia, and improve detection of critical congenital heart disease in newborn. As very few studies are available in literature for PI as an indicator for evaluating the success of peripheral nerve blocks. In present study we planned to evaluate the perfusion index as the predictor of successful block in patients undergoing upper limb surgeries under ultrasound guided infraclavicular block.

This study will include 60 patients of either sex planning to undergo upper limb surgeries under ultrasound-guided infraclavicular nerve block. After local anesthetic injection, sensory and motor block success will be assessed and perfusion index will be recorded at baseline and at every 2 minutes till 10 minutes and every 5 minutes thereafter till 30 min. The PI ratio will be calculated as the PI after 10 min divided by the PI at the baseline. The observation obtained will be tabulated and analyzed using appropriate statistical method.