An evaluation of nitrous oxide analgesia during transcutaneous pacing.

Transcutaneous cardiac pacing (TCP) is a promising prehospital intervention, but there are little data available regarding protocols to improve patient tolerance to TCP. A 50:50 nitrous oxide:oxygen analgesic mixture also is a commonly employed prehospital intervention. In this randomized, prospective study, we compared the discomfort experienced by 18 healthy subjects when paced in two trials at the capture threshold: one following breathing of a 50:50 nitrous oxide:oxygen mixture; and the second only breathing room air. Discomfort was rated on an analog scale from 1 (minimal discomfort) to 10 (severe pain). Of the 18 subjects, 15 (83%) reported that nitrous oxide improved the tolerance to pacing at capture threshold. The median pain scores at capture threshold in the nitrous oxide and room air group were 3.8 and 5.0 respectively (P less than .05). Nine of the subjects tolerated TCP for the maximum allotted time of 30 seconds in each trial; six tolerated TCP for a longer time period in the nitrous oxide trial; three tolerated TCP longer in the room air trial. These data suggest that inhalation of 50:50 nitrous oxide:oxygen mixture may improve tolerance to TCP in the conscious patient.