Effects of electroanesthesia and a phenothiazine tranquilizer on thermoregulation in the sheep

The effects of giving propiopromazine alone and of electroanesthesia-propiopromazine treatment on thermoregulation (body temperature regulation) were studied in 3 sheep at ambient temperatures of 5, 25, and 35 C. Measures of thermoregulation during a 120-minute treatment and 120-treatment recovery period included rectal temperature, respiratory frequency, respiratory evaporative heat loss, metabolic heat production, multiple skin temperatures, and shivering. During cold exposure (5 C), both the propiopromazine administration and the electroanesthesia-propiopromazine treatment resulted in hypothermia which was attributed to increased peripheral and respiratory heat losses, a transient inhibition of shivering thermogenesis, and a reduction in metabolic heat production. At 35 C ambient temperature, both resulted in hyperthermia caused principally by a reduction in respiratory evaporative heat loss. The effects of electroanesthesia-propiopromazine treatment on thermoregulation appeared to be additive at both the cold (5 C) and the hot (35 C) environments, in that simultaneous administration resulted in a more profound thermoregulatory impairment. Nevertheless, shifts in body temperature during electroanesthesia are partly attributable to phenothiazine premedication.