Peripheral perfusion index does not accurately reflect hypoperfusion in healthy dogs undergoing elective ovariohysterectomy

This study evaluated the variability of the peripheral perfusion index (PI) in 22 anaesthetised female dogs undergoing elective ovariohysterectomy and examined the relationship between peripheral PI and heart rate, blood pressure, blood pH, end tidal CO2 (EtCO2), O2 saturation (SpO2), core-peripheral temperature gradient (ΔTc-p), partial pressure of CO2 (PCO2), and concentrations of glucose, cortisol, lactate and bicarbonate (HCO3−). Blood pH, lactate and glucose concentrations were determined 15, 30, 45 min into the ovariohysterectomy procedure and after extubation. Cortisol concentrations were assessed before anaesthesia and after extubation. Other variables were recorded at every 5 min throughout the ovariohysterectomy procedure. Hyperglycaemia was observed in 59% of bitches during surgery, but serum cortisol concentrations remained unchanged. Most measures of perfusion (ΔTc-p, pH, PCO2, EtCO2, SpO2) and heart rate remained unchanged throughout anaesthesia and did not correlate with peripheral PI. Mean arterial pressure increased during the ovariohysterectomy procedure, while peripheral PI decreased, resulting in negative correlations between these variables at 30 and 45 min. Lactate concentrations decreased from baseline to the time of measurement post-extubation. Peripheral PI gradually decreased during the ovariohysterectomy procedure, probably reflecting vasoconstriction induced by nociceptive stimuli. Using lactate concentrations as the reference standard for peripheral perfusion, low peripheral PI in healthy bitches undergoing ovariohysterectomy might not represent peripheral hypoperfusion.