What is the purpose of a MAC-sparing effect in CRIs?

• A. To reduce cardiovascular and respiratory depression
• B. To increase MAC
• C. To prolong recovery
• D. To enhance analgesia only

Answer: (A)

MAC-sparing means using a CRI of adjunct drugs to lower the amount of volatile anesthetic needed to achieve surgical immobility. By reducing the required concentration of inhaled agent, you cut its dose-dependent effects on the heart and lungs, leading to better cardiovascular stability and ventilation during anesthesia. In practice, agents given continuously (like opioids, lidocaine, dexmedetomidine, or ketamine) can achieve this sparing. This isn’t about increasing the inhaled anesthetic concentration, nor is it solely about analgesia; while analgesia can be enhanced, the main goal is safer anesthesia by reducing cardiovascular and respiratory depression. Recovery may be facilitated because less volatile agent is used, but the central idea is lowering the inhaled dose to minimize depressant effects.