Effects of anesthesia on the spontaneous activity of the microvasculature.

The effects of pentobarbital, alpha-chloralose, alphaxalone-alphadolone, diethyl ether and chloralose-urethane anesthesia on microvascular vasomotion were studied in the hamster skin fold window preparation. All these agents paralyzed vasomotion in the arterioles causing an initial vasodilation, where diameters were above the control-unanesthetized mean values (UMD) for a period of 5-60 min and returned to UMD, and lower, after periods up to 90 min depending on the type of anesthetic. During chloralose-urethane anesthesia vasodilation lasted until the end of observation (90 min). The responses were quantitatively different as a function of vessel type, being more pronounced in the smaller terminal arterioles. Vasomotion did not recover at the end of anesthesia, when the animals awoke, and the vessels tended to remain inert for periods up to 10-20 min, at which time the activity was reestablished with the same control fundamental frequency. Small veins and venules did not exhibit vasomotion and showed various reactions that were characteristic for each anesthetic and vessel type, where vasodilation was the prevalent feature during pentobarbital anesthesia while diethyl ether had the opposite effect. Venular microvessels recovered control diameters 10-20 min after awakening.