Date of Award

Summer 2014

Degree Type


Degree Name

Master of Science (MS)


Veterinary Clinical Science

First Advisor

Jeff C. Ko

Committee Chair

Jeff C. Ko

Committee Member 1

George E. Moore

Committee Member 2

Ann B. Weil


Plethysmographic Variability Index (PVI) is a derivative index of pulse oximetry that allows evaluating an individual's intravascular volume status. Perfusion Index (PI) represents the strength of pulse signal at the anatomic site of measurement from which PVI is calculated using changes in PI over respiratory cycles. Plethysmographic Variability Index has been used to detect hypovolemia and predict fluid responsiveness in mechanically ventilated human patients however, fewer studies are available in spontaneously breathing patients. The use of PVI has not been explored extensively in dogs so far. The goals of this study were to establish a common range for PVI and assess relationship of the PVI, PI and various clinical variables in the anesthetized spontaneously breathing dogs. Values of PVI and PI derived from Masimo pulse oximetry were obtained at 5, 10, 15 and 20 minutes after anesthetic induction but before surgical stimulation together with cardiorespiratory variables that included heart rate, blood pressures (systolic, mean and diastolic blood pressures), respiratory rate and hemoglobin saturation of oxygen (SpO2) in 73 dogs with ASA 1-3 status admitted to the Purdue Teaching Hospital.^ Other clinical variables like body temperature, anesthetic protocol used, pre-induction packed cell volume (PCV) and total protein (TP) values, recumbency positions (sternal, lateral or dorsal recumbency) and rate of crystalloid fluids administration (5 vs 10 ml/kg/hr) were also obtained. Data were analysed using non-parametric Spearman's rho coefficient and Kruskal Wallis one-way ANOVA by ranks to assess temporal relationship of PVI with all the clinical variables and with significant level set at P<0.05. A common range of PVI was 5-43% with a median 18%. There was no significant correlation found between PVI and PI. Plethysmographic Variability Index positively correlated with the systolic blood pressure (rs=0.25; P<0.001), mean blood pressure (rs=0.26; P<0.001), diastolic blood pressure (rs=0.36; P<0.001) and body temperature (rs=0.166; P=0.004). The other cardiorespiratory variables, recumbency positions, rate of crystalloid fluid administration, pre-operative PCV and TP values had no relationship with PVI. Premedication containing dexmedetomidine resulted in higher PVI (Kruskal-Wallis Test; P=0.001) and lower PI values (Kruskal-Wallis Test; P=0.004) and the opposite was true with protocols that contained acepromazine. It was concluded that while evaluating PVI for fluid response in the anesthetized dogs, various clinical factors should be taken into consideration.