During stage III anesthesia, which species has a tachycardia threshold of greater than 140 bpm?

During stage III anesthesia, which species has a tachycardia threshold of greater than 140 bpm?

• A. Large Dog
• B. Small Dog
• C. Cow
• D. Horse

Answer: (A)

During stage III anesthesia, heart rate is used to gauge depth and physiological stress, but the value at which tachycardia is considered significant varies by species and size. Large dogs have a relatively high cardiac reserve and greater stroke volume, so they can tolerate a higher heart rate before perfusion becomes concerning. This means a tachycardia threshold above about 140 beats per minute is reasonable for large dogs. In contrast, small dogs, cows, and horses tend to show signs of tachycardia at lower heart rates under anesthesia due to their different cardiovascular physiology and baseline rates. Therefore, the species with a tachycardia threshold greater than 140 bpm is the large dog.

During stage III anesthesia, heart rate is used to gauge depth and physiological stress, but the value at which tachycardia is considered significant varies by species and size. Large dogs have a relatively high cardiac reserve and greater stroke volume, so they can tolerate a higher heart rate before perfusion becomes concerning. This means a tachycardia threshold above about 140 beats per minute is reasonable for large dogs. In contrast, small dogs, cows, and horses tend to show signs of tachycardia at lower heart rates under anesthesia due to their different cardiovascular physiology and baseline rates. Therefore, the species with a tachycardia threshold greater than 140 bpm is the large dog.