Relief of discomfort during acute
myocardial ischemia is usually accomplished with a
narcotic analgesic. Because these medications may cause unpleasant symptoms and exert a possibly adverse hemodynamic effect, the availability of alternative
analgesic medication would be advantageous.
Nitrous oxide is a commonly used potent
analgesic gas.
Nitrous oxide has been used to relieve ischemic discomfort during
myocardial infarction. The current study was undertaken to corroborate that data in a randomized, blinded, cross-over study and to begin to explore a mechanism for the
analgesic effect. Twelve patients with typical ischemic chest discomfort and a suspected
myocardial infarction were included in the study. Each patient received a 30-minute inhalation treatment of 30%
nitrous oxide/70%
oxygen and 30 minutes of 30% room air/70%
oxygen. Patients were blinded to their treatment and were randomized to receive
nitrous oxide first, then room air, or vice versa. A semiquantitative assessment of the severity of chest discomfort was made before, during, and at the conclusion of each treatment together with a measurement of plasma
beta-endorphin levels using a venous blood sample. Eleven of the 12 patients reported a significant reduction in the intensity of their chest discomfort during the
nitrous oxide inhalation, but none had
pain relief during the control period.
Beta-endorphin levels fell to a greater extent during the inhalation of
nitrous oxide than during the control period (51% versus 26%; P less than .05). No significant adverse effects were noted and most patients slept during the
nitrous oxide inhalation. It is concluded that
nitrous oxide anesthesia is a superior method of
pain relief in patients with
ischemic heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)