• Bonnie J Gatson, Fernando L Garcia-Pereira, Michelle James, Shelia Carrera-Justiz, and Daniel D Lewis.
• Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA.
• Vet Anaesth Analg. 2016 Nov 1; 43 (6): 662-669.

ObjectivesTo evaluate perfusion index (PI) as a determinant of regional nerve block success following sciatic nerve blockade with bupivacaine in dogs undergoing stifle surgery.Study DesignProspective clinical trial.AnimalsTen adult dogs, aged 5.6 ± 2.6 years and weighing 36.9 ± 16.8 kg, undergoing a tibial plateau leveling osteotomy.MethodsDogs were premedicated with acepromazine (0.03 mg kg-1 ) and hydromorphone (0.1 mg kg-1 ) intramuscularly, and anesthetized with propofol (up to 4 mg kg-1 ) intravenously and isoflurane in oxygen. An ultrasound-guided femoral and sciatic (F+S) nerve block was performed on the surgical limb with bupivacaine (0.75%), 0.2 mL kg-1 at the femoral site and 0.3 mL kg-1 at the sciatic site, with a maximum volume of 10 mL per site. Physiological variables were recorded every 5 minutes throughout anesthesia. A pulse co-oximeter probe was placed between the third and fourth digits of both pelvic limbs, and the PI was recorded 5 minutes before infiltration with bupivacaine, immediately afterwards, and every 5 minutes for 30 minutes. Motor nerve conduction velocity (MNCV) of the sciatic nerve was performed on the surgical limb 5 minutes before and 20 minutes after bupivacaine administration to confirm nerve block.ResultsThe PI of the surgical limb was significantly greater than the contralateral pelvic limb at 10 minutes (p = 0.03) and 15 minutes (p < 0.01) after F+S nerve blockade. The MNCV performed after sciatic nerve blockade revealed a functional motor blockade for all dogs. There were no significant changes in physiological variables.Conclusions And Clinical RelevanceThe PI provided a reliable indication of successful sciatic nerve blockade in the clinical patients in this study. No increase in the PI by 15 minutes after bupivacaine administration around the sciatic nerve could indicate partial or total failure of anesthetic blockade.© 2016 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

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