Cognitive modification of pain: information in combination with N2O

The present study sought to discover whether information clarifying how the analgesic/sedative drug nitrous oxide (N2O) works would result in increased analgesic responses to painful stimuli when various concentrations of N2O were administered. Subjects were provided with high and low levels of information regarding the action and use of N2O as an analgesic and sedative. Absolute sensation threshold (AST), pain threshold (PTh), and pain tolerance (PTo) to tooth pulp shock were measured in microamperes during administration of each of 3 concentrations of N2O (15%, 30%, and 45%, with oxygen). Subjects rated stimulus intensity and stimulus aversiveness in response to a fixed painful stimulus, and completed questionnaires regarding the perceived efficacy of N2O and their subjective mood state throughout the session. The marked differences observed in pain reports between the high information group and the control group confirm that providing information to people receiving a drug for pain relief yields higher sensation thresholds, pain thresholds, and tolerance of pain. In addition, we observed that in the presence of N2O an equivalent fixed painful stimulus will be perceived as less painful after appropriate information is provided. These findings suggest that experimentally influencing thought processes, in combination with an analgesic, can have the effect of increasing analgesia.