Psoas compartment block (PCB) in children: Part II - generation of an institutional learning curve with a new technique1

Abstract

Literature concerning institutional learning processes for anesthesia procedures in pediatric anesthesia is rare. Until recently only small series of psoas compartment blocks (PCB) in children have been reported. We report on a series of 100 consecutive blocks using new landmarks and the institutional learning process. In 100 consecutive children (5.9-106 kg) PCB was performed using a nerve stimulator. In the lateral position, the needle was inserted between the medial 2/3 and the lateral 1/3 on a line from the spinous process of L4 to the posterior superior iliac spine. Residents unfamiliar with PCB were instructed by one single staff member without manual intervention. Failure was defined as a bloody tap, more than one skin perforation with the needle or relinquishing the procedure to senior staff. To evaluate the institutional learning process the cumulative sum (CUSUM) statistical technique was used. CUSUM analysis was performed using an acceptable failure rate of 10%. A learning curve using a bootstrap technique and a least square fit model was also used. Although all blocks were clinically successful, only in 64% was a single attempt sufficient. In 16% vascular puncture occurred. Surprisingly the CUSUM analysis showed a clear institutional learning phenomenon. Applying a strict definition for a successful block, more than 100 PCB in an institution may be necessary. Using the generated learning curve, for a success rate of 70% a case load of at least 55 attempts is required. Although the described new technique had a very high success rate with a low complication rate, PCB in children is not easily implemented into clinical practice when strict criteria of success were used, despite a well-controlled environment. Training programs could use CUSUM to track the progress of their institutional learning in order to guarantee adequate experience.