Differentiation of Two Types of Pain by Anesthetics

Abstract

The pain thresholds, to a cutaneous thermal stimulus and to a tibial pressure stimulus were measured before, during, and after the administration of nitrous oxide (25-30% in oxygen), halothane (0.5%) and sodium thiopental (100-150 mg in 10 minutes). The thermal pain and the tibial pressure pain thresholds rose with nitrous oxide and halothane. The thermal pain threshold rose with sodium thiopental but simultaneously the tibial pressure pain threshold fell. It is deduced that the sensations produced by these two stimuli are neurologically different and that the known differences between the actions of barbiturates and inhalational anesthetic drugs on presynaptic inhibition in the spinal cord can account for this differentiation.