The animal use protocol was reviewed and approved by the University of California Irvine Institutional Animal Care and Use Committee. New Zealand white rabbits (3.5 to 4.5 kg) were divided into two groups, control () and sulfanegen sodium treatment () group. Animals were anesthetized with an intramuscular injection of a ratio of ketamine HCl (, Ketaject, Phoenix Pharmaceutical Inc., St. Joseph, MI): Xylazine (, Anased, Lloyd Laboratories, Shenandoah, IA) at a dose of , using a 23-gauge -in. needle. After the intramuscular injection, a 23-gauge 1-in. catheter was placed in the animals’ marginal ear vein to administer continuous IV anesthesia. Torbugesic-SA (butorphanol tartrate, Fort Dodge Animal Health, Fort Dodge, IA), 0.1 to , was given subcutaneously and then the animals were intubated with a 3.0 mm cuffed endotracheal tube secured by a gauze tie and were mechanically ventilated (dual phase control respirator, model 32A4BEPM-5R, Harvard Apparatus, Chicago, IL) at a respiratory rate of , a tidal volume of 50 cc, and of 100%. A pulse oximeter (Biox 3700 Pulse Oximeter, Ohmeda, Boulder, CO) with a probe placed on the tongue was used to measure and heart rate. Femoral venous and arterial lines were placed to provide central venous and arterial access. Blood gas sampling, CN infusion and continuous blood pressure monitoring were accomplished via these lines. Both control and treatment groups were administered 10 mg of NaCN in 60 cc normal saline, infused intravenously at a rate of for 60 min. After NaCN infusion stopped, the treatment group was administered 0.05 mmol of sulfanegen sodium (5 ml) IV while the control group received 5 ml of saline and animals were monitored for an additional 90 min during recovery (Fig. 1). A CWNIRS probe (1.65-cm source detector separation) was placed on the forehead, and another probe (0.95-cm source detector separation) was placed on the right foreleg muscle. Changes in [OHb] and [RHb] during CN infusion and recovery were simultaneously measured from both brain region and foreleg muscles every second and were compared to each other.