Ambient Heat and Nerve Agent Antidotes: Effects on Soldier Performance with the Usariem Performance Inventory

The tactical significance of chemical weapons in future warfare demands that nerve agent antidotes be available for troops exposed to chemical attack. Since future combat operations will likely occur in desert and tropical areas, chemical attacks in such areas could lead to situations involving the use of nerve agent antidotes by troops during exposure to hot weather conditions. This study assessed, both independently and in combination, the effects of heat exposure (95°F, 60%RH) and US Army standard dosages of nerve agent antidotes (2 mg atropine and 600 mg 2-PAM chloride) on the performance of a variety of tasks selected from the USARIEM Performance Inventory (UPI). The UPI tasks selected for inclusion assessed sensory functioning, perceptual-cognitive functioning, sensorimotor skill, subjective reactions, and M16 rifle marksmanship. Fifteen soldier volunteers were first trained to asymptotic performance on the UPI task battery. Then, over a period of four test days, they completed a counterbalanced schedule of the drug/no drug and heat/no heat conditions while outfitted in the Battle Dress Uniform. On each test day, the tests from the UPI were administered once during each of the three 2-hour test cycles. Compared to the placebo condition, a single dose of nerve agent antidote significantly impaired soldier performance such that visual reaction time was 5 to 11% slower, gross body mobility was 12% poorer, rifle marksmanship (pop-up targets) was 3% less accurate, and verbal reasoning was 6% slower. Compared to the 70°F condition, the 95°F ambient condition significantly impaired soldier performance such that arm-hand steadiness was 10% poorer, manual dexterity was 2% poorer, and rifle marksmanship (tightness of shot group) was 13% less accurate. Nerve agent antidote and ambient heat did not interact to further impair soldier performance.