Perfusion Index of Dogs Subjected to Pharmacologically-Induced Peripheral Vasoconstriction and Vasodilation

Abstract

This study assessed the variability of peripheral perfusion index (PPI) of 12 healthy male dogs under general anesthesia. Subjects were induced to anesthesia and maintained with propofol alone, with no premedication, and were allowed to breathe spontaneously. Each dog underwent three experimental treatments: saline solution (SAL), norepinephrine (NOR) and sodium nitroprusside (NIT), in randomized order. Mean stabilization times under each treatment were 24 ± 3 minutes (SAL), 33 ± 6 minutes (NOR) and 37 ± 5 minutes (NIT). Variables were recorded at 5-minute intervals and comprised: heart rate, mean arterial pressure, PI measured at the tongue and prepuce, peripheral oxyhemoglobin saturation, end-tidal carbon dioxide, and esophageal temperature. The cardiac index was measured at the end of each treatment using Doppler echocardiography. No significant differences were observed in PPI between measurement sites (tongue and prepuce), although a strong correlation was found between sites for the NOR group (r = 0.7143). The cardiac index (mL/kg/min) differed between groups NIT (240 ± 96) and NOR (150 ± 59) but showed no significant differences compared to SAL (169 ± 72). Group NOR exhibited marked tachypnea, and myoclonus was observed in 50% of dogs and were associated with the use of propofol and norepinephrine. The PPI varied between sites, thus limiting the definition of reliable intervals for this variable. In conclusion, norepinephrine and sodium nitroprusside did not significantly impact peripheral perfusion of healthy dogs, possibly due to the physiological compensatory capacity of these individuals.

Keywords: nitroprusside, norepinephrine, peripheral perfusion, oximetry