A prospective observational clinical trial to assess the efficacy of perfusion index (PI) as a predictor of onset of pediatric caudal block under general anesthesia

Caudal block under general anesthesia is quite popular for pediatric lower limb surgeries as it is one technique that fits all. It is relatively easy to learn with a high mean success rate and a remarkable safety record. However, failure of the caudal block is about 4% due to abnormal anatomy, operator inexperience and wrong choice of block.

It is often very difficult to assess the quality of analgesia in children intra-operatively as most of the regional blocks are performed under general anesthesia or sedation in contrast to adults. Conventionally one waits to see the patient’s response to the surgical skin incision to make a clinical decision of working caudal block. Unsuccessful block causes a raise in HR, Blood Pressure on skin due to pain. This calls for more reliable and faster objective parameters that can confirm the efficacy of caudal block in children.

Recent advances in Pulse Oximeter technology have broadened the ability to measure more parameters such as Perfusion Index (PI). PI is a noninvasive numerical assessment of the pulsatile strength at a monitoring site providing useful information about the peripheral perfusion status of the patient. A decrease in PI can occur because of local vasoconstriction while vasodilatation results in an increase in PI in the skin at the monitoring site. Recent studies recommended that PI can be used as an early and sensitive indicator to detect the development of epidural-induced sympathectomy leading to vasodilation and increased perfusion in adults. In adult population many numbers of studies done and most of them concluded that PI is the best tool in predicting the onset and adequacy of caudal block. In children especially in Indian population, the studies that have been done are very limited. This study that mainly focusing on pediatric population might be helpful to assess whether PI can be applied to detect the onset and adequacy of caudal block under GA similar to adults. Hence in this study we tried to compare the role of PI, HR and Mean Arterial Pressure (MAP) in detecting the onset and adequacy of caudal block.