Effects of Cyclopropane on Canine Cerebral Blood Flow and Metabolism: Modification by Catecholamine Suppression

The effects of 5, 13, 20, and 30 per cent cyclopropane, alone and with either reserpine or spinal anesthesia, on cerebral blood flow (CBF) and metabolic rate for oxygen (CMRO2) were investigated in three groups of nine dogs each. With cyclopropane alone, CBF increased abruptly in eight of nine dogs as the concetration was increased, while CMRO2 changed insignificantly. After pretreatment with reserpine, CBF decreased significantly with 13 per cent cyclopropane, but at higher concentrations increased abruptly in four of nine dogs. CMRO2 decreased with 13 per cent cyclopropane and remained decreased at the higher concentrations. During spinal anesthesia, CBF and CMRO2 decreased significantly with increases in cyclopropane. In a single dog, during spinal anesthesia and 20 per cent cyclopropane, CBF and CMRO2 increased during intravenous infusions of both epinephrine (0.1 and 0.25 μ/kg/min) and norepinephrine (0.25 μ/kg/min). The authors conclude that the unusual and variable effects of increasing concentrations of cyclopropane on CBF and CMRO2 are secondary to the increases in circulating catecholamine levels resulting from the sympathoadrenal stimulatory effects of this anesthetic.