Phrenic nerve stimulation at the bedside in children; equipment and validation

There is evidence that early diagnosis of postoperative phrenic nerve damage may improve outcome, by allowing early surgical treatment, in children following cardiac surgery. This has prompted the development of a simple method for measuring phrenic nerve latency at the bedside in children. We have evaluated the reproducibility of measurements made with this system in 11 children (4 months to 13 yrs) admitted for routine surgery or cardiac catheterizations, and have assessed the various components of variability inherent in the measurement of phrenic nerve latency. The overall variability of the phrenic nerve latency with this technique (95% confidence interval) is approximately +/- 1 ms, and differences greater than this between measurements are likely to reflect a real change in phrenic nerve function. Our results indicate that the bedside technique should be a useful method of the objective assessment of phrenic nerve function in children recovering from cardiac surgery.