THE CASE FOR REBREATHING CIRCUITS FOR VERY SMALL ANIMALS

The objections to using adult circle systems on very small patients include increased resistance to breathing, mechanical dead space, and slow equilibration times. These objections warrant consideration before assuming that nonrebreathing systems have an inherent advantage for patients between 3 and 10 kg. The cost of anesthesia and the time taken to establish a desired anesthetic level are as important in determining which system to use for small animal patients. Based on the current evidence, it is acceptable to use adult circle rebreathing systems on healthy patients as small as 3 kg.