The relationship between current intensity for nerve stimulation and success of peripheral nerve blocks performed in pediatric patients under general anesthesia.

Background: We evaluated the relationship between the lowest current amperage used to obtain a motor response, the success rate and the incidence of neurological complications with peripheral nerve blocks (PNB) in pediatric patients under general anesthesia.

Methods: We reviewed the regional anesthesia database at The Children's Hospital of Philadelphia and included all pediatric patients who received a single-injection PNB under general anesthesia with the aid of a peripheral nerve stimulator between October 2002 and July 2006. Data analyzed included age, sex, type of block, stimulation threshold, presence of sensory and motor blockade, and neurological complications.

Results: Six-hundred sixty patients received a PNB during the study period. The average age of the patients was 13.8 yr (range = 2-18 yr). All the blocks were performed using a current ranging between 0.2 and 1 (median = 0.5 mA, interquartile range: 0.45-0.55 mA). The overall success rate was 96%. There was no difference in success rate between blocks performed using a stimulation threshold of < or =0.5 or >0.5 mA (96.3% vs 95.9%; P = 0.793). There was no correlation between the success rate and sex, type of block performed or intensity of current used. Two patients reported prolonged nerve blockade of the great toe and dorsum of the foot after a sciatic nerve block, which lasted for 72 h. No long-term sequelae were noted in our patients.

Conclusion: In this study, a similar PNB success rate was observed with both a low (*0.5 mA) and a high stimulation threshold (>0.5 mA). Therefore, it may not be necessary to perform needle manipulations to achieve a low stimulation threshold (< or =0.5 mA), as this may increase the risk of intraneural injection.