Fever in young lambs: carotid denervation alters the febrile response to a small dose of bacterial pyrogen.

Experiments were done on 13 young lambs to determine if carotid denervation influences the cardiovascular and metabolic responses to i.v. administration of bacterial pyrogen [Salmonella abortus equi (SAE) 0.3 micrograms]. Each lamb was anesthetized with halothane and prepared for measurements of cardiac output, arterial and mixed venous oxygen saturations, and body core temperature. No sooner than 3 d after surgery, measurements were made during a control period and at 10-min intervals for 120 min after i.v. administration of SAE in seven carotid-intact lambs and six carotid-denervated lambs. Administration of SAE produced a short-lived fever of about 1 degrees C in the carotid-intact lambs, whereas no change in body core temperature was observed in the carotid-denervated lambs. In carotid-intact lambs, the rise in body core temperature began approximately 40 min after administration of SAE and continued for approximately 50 min. This rise in body core temperature was preceded by the onset of shivering and an increase in total body oxygen consumption. Carotid denervation produced changes in some of the cardiovascular variables during the control period (i.e. arterial oxygen content, cardiac index, heart rate, and pulmonary blood pressure); however, there were no additional significant changes in any of the metabolic or cardiovascular variables after administration of SAE. The mechanism of these unexpected findings remains to be determined.