Phrenic nerve conduction studies in acute organophosphate poisoning

Phrenic nerve conduction studies were performed within 48 h of admission an d subsequently in 29 patients (14 of whom required mechanical ventilation) with acute organophosphate (OP) poisoning. The mean (+/-SD) amplitude of th e diaphragmatic compound muscle action potential (CMAP) in patients requiri ng mechanical ventilation (119.09 +/- 173.85 mu V) was significantly lower than in those not requiring mechanical ventilation (461.63 +/- 138.69 mu V) (P < 0.0001). Diaphragmatic CMAP amplitudes in ventilated patients increas ed with time during the course of hospitalization and were normal in 5 (36% ) patients and only mildly reduced in another 6 (43%) patients prior to dis continuation of mechanical ventilation, which was undertaken 4-18 days (mea n 7 +/- 3 days) after poisoning. Eleven patients (79%) were successfully we aned from mechanical ventilation at the first attempt, In the 3 (21%) remai ning patients, mechanical ventilation had to be reestablished because of we aning failure. The mean (+/-SD) diaphragmatic CMAP amplitude, prior to disc ontinuation of ventilatory assistance, was 242.6 +/- 94.1 mu V in these 3 p atients. After ventilatory discontinuation, it fell to 95.5 +/- 105.8 mu V. Thus, reduced diaphragmatic CMAP amplitudes correlate with the need for me chanical ventilation in acute OP poisoning. (C) 2000 John Wiley & Sons, Inc .