Which of the following is the PRIMARY mechanism by which volatile anesthetics cause intraoperative hypotension?

Explanation

## Volatile Anesthetic-Induced Hypotension ### Mechanism of Blood Pressure Reduction **Key Point:** Volatile anesthetics (sevoflurane, isoflurane, desflurane) cause dose-dependent hypotension through TWO concurrent effects: 1. **Direct myocardial depression** — reduced contractility and stroke volume 2. **Peripheral vasodilation** — decreased systemic vascular resistance (SVR) ### Comparative Effects by Agent | Agent | Myocardial Depression | Vasodilation | Net BP Effect | |-------|----------------------|--------------|---------------| | Isoflurane | Moderate | Marked | Significant ↓ | | Sevoflurane | Mild–Moderate | Moderate | Moderate ↓ | | Desflurane | Moderate | Marked | Significant ↓ | | Nitrous oxide | Minimal | Minimal | Minimal ↓ | ### Why Baroreceptor Reflex Is NOT Impaired **Clinical Pearl:** Volatile anesthetics do NOT block the baroreceptor reflex; in fact, the reflex is **blunted but still present**. This is why patients may show a compensatory tachycardia at lighter planes of anesthesia — the reflex attempts to maintain cardiac output despite reduced SVR and contractility. ### High-Yield Summary **Mnemonic: VAPE** — **V**olatile anesthetics cause **A**ltered **P**erfusion via **E**xcess vasodilation + myocardial depression. **Key Point:** The hypotension is DOSE-DEPENDENT; increasing MAC (minimum alveolar concentration) worsens both myocardial depression and vasodilation.