Reply to Letter: False positive absent somatosensory evoked potentials in cardiac arrest with therapeutic hypothermia.

The reviewer commented that the level of noise on the cortical races was so high that the recording should not lead to any conlusions. We appreciate the reviewer’s comments, but suggest that erhaps the reviewer did not examine the figure legend closely and pply the stated calibrations to the traces. The channel derivation onsisting of the midline frontal to parietal cortex contralateral to he side of stimulation are standard for this clinical application and re traces 2 and 6 from the top in Fig. 1; the calibrations for those races are 0.7 V per division which is twice the display magnificaion of the subcortical channels (traces 3 and 7). Thus, one would xpect more baseline “noise” in those traces. We chose to use this egree of display magnification in order to optimally demonstrate hat there were no waveforms present. The actual peak-peak ambint noise levels in those traces is less than 0.1 microvolts, which s an excellent ambient artifact level in clinical SEP practice. The 19 mean amplitude (baseline to peak) in 50 normal subjects was .0 V (minimum value 0.1),1 and the P22 mean amplitude (N19 eak to P22 peak) was 2.2 V (minimum 0.5), the latter exceedng the peak-to-peak ambient noise levels here by a factor of 5, o that it would have been easily visible. In trace 6 there is a possile negative deflection at 19–22 ms, followed by a possible positive eflection at 22–25 ms; the latter amplitude is about 0.1 V, well elow the lowest value of 0.5 V seen in normal subjects. Thus, the bsence of any reliable waveforms identifiable as N19/P22 here is linically significant to a high degree. The reviewer might have felt