Objective—To compare the time to desaturation in healthy dogs that breathed oxygen or room air for 3 minutes before induction of anesthesia.
Animals—20 healthy dogs.
Procedures—Dogs were sedated with morphine and acepromazine maleate. Dogs received a 3-minute treatment of room air or oxygen (100 mL/kg/min) via face mask. Arterial blood samples were collected before and after treatment to determine PaCO2, PaO2, pH, and SaO2; propofol (6 mg/kg, IV) was injected during a 7-second period, and the dogs were intubated. A lingual pulse oximeter probe was placed. Dogs remained disconnected from the breathing circuit until SpO2 equaled 90% (desaturation point) and then connected and ventilated until the SpO2 was ≥ 97%. Arterial blood samples were collected and SpO2 was recorded every 30 seconds for 4 minutes and then every minute until the desaturation point. Times to first breath and the desaturation point were recorded. Data were collected at 0, 5, 30, 60, 90, 120, and 150 seconds.
Results—Mean ± SEM time to desaturation differed significantly between dogs treated with room air (69.6 ± 10.6 seconds) and oxygen (297.8 ± 42.0 seconds). Lowest mean PaO2 and SaO2 when dogs were breathing room air were 62 ± 6.3 mm Hg and 82.3 ± 4%, respectively, at 30 seconds.
Conclusions and Clinical Relevance—Preoxygenation for 3 minutes increased the time to desaturation in healthy dogs sedated with acepromazine and morphine in which anesthesia was induced with propofol.