Show the perfusion index value showing the success of the block (CUT-OFF) in the axillary blocks made with ultrasound

Objective: In order to evaluate the adequacy of a successful block after peripheral nerve block, studies on Perfusion Index (PI) measured by pulse oximetry technology have been carried out recently. In this study; We aimed to find the perfusion index value, which indicates the success of the block (cut-off) in axillary blocks performed with ultrasonography. Method: Fifty patients between the ages of 18 and 65 years, who were in the ASA 1-2 group, undergoing hand, wrist and forearm surgery, were included in the study. Before the axillary block was applied to the patients, the PI value was measured from the extremity to be blocked and the healthy extremity. 3 minutes after the axillary block was applied to the patients, sensory block was evaluated with the Pin-Prick test and motor block was evaluated with the Modified Bromaga Scale. The minutes when sensory and motor block occurred were recorded and the PI value at these moments was recorded. In addition, the patient's peripheral oxygen saturation (SpO2), heart rate, non-invasive arterial pressure (NIAB) and PI values ​​measured from both extremities were recorded at 5, 10 and 20 minutes. Results: Perfusion index values ​​indicating that the block was successful (cut-off) in axillary blocks: Pin-Prick test was positive in patients on average 8.4 ± 2.4 minutes. The average PI value for which the Pin-Prick test was positive was 7.41 ± 2.54, and the cut off value of the sensory block PI ratio was determined as 1.7 times. The point at which the PI value of 1.7 times the basal PI value is reached in the patient indicates that the sensory block has developed. The modified Bromage scale reached a score of 2 in 7.6 ± 2.3 minutes on average. The average PI value for which the Modified Bromage Scale score is 2 is 7.27 ± 2.69. Modified Bromage Scale-2 PI ratio cut off value was determined as 1.7 times. Modified Bromage scale becomes-2 at the point where the PI value is 1.7 times the basal PI value in the patient. The Modified Bromage Scale reached a score of 3 in an average of 12.6 ± 4.2 minutes. The mean PI value for which the Modified Bromage Scale score is 3 is 9.56 ± 6.97. The cut off value of the motor block PI ratio was determined as 1.9 times. The point at which the PI value 1.9 times the basal PI value is reached in the patient indicates that the motor block has developed. Conclusion: In the axillary block performed under US guideline, 0.7% increase in PI value compared to the baseline value for sensory block and 0.9 increase in motor block was found as the cut-off value, which indicates successful block.