A 6-year-old child is scheduled for elective tonsillectomy under general anesthesia. The anesthesiologist is deciding between desflurane and sevoflurane for inhalational induction. Which property best distinguishes desflurane from sevoflurane and influences the choice of induction agent in this case?

Explanation

## Desflurane vs. Sevoflurane: The Airway Irritation Distinction ### Clinical Context: Pediatric Inhalational Induction **Key Point:** Desflurane is highly pungent and irritating to the airway, making it unsuitable for inhalational induction in children. Sevoflurane is the agent of choice for gas induction in pediatric patients because of its smooth, non-irritating properties. ### Comparative Properties Table | Property | Desflurane | Sevoflurane | | --- | --- | --- | | **Airway irritation** | High (very pungent) | Low (non-irritating) | | **Suitable for inhalational induction** | No | Yes | | **MAC** | 6.0% | 2.0% | | **Blood:gas solubility** | 0.42 | 0.65 | | **Emergence time** | Fastest | Fast | | **Hepatic metabolism** | ~0.02% | ~3–5% | | **Clinical use in pediatrics** | Maintenance only | Induction and maintenance | **High-Yield:** Desflurane's extreme pungency (6% MAC, lowest blood:gas solubility) causes coughing, laryngospasm, and airway obstruction during inhalational induction. It is reserved for maintenance after IV or sevoflurane induction. ### Why Desflurane Cannot Be Used for Induction 1. **Airway irritation mechanism:** Desflurane's high pungency stimulates airway sensory receptors, triggering protective reflexes. 2. **Clinical consequences:** Coughing, breath-holding, laryngospasm, increased intracranial pressure (ICP), and increased heart rate and blood pressure. 3. **Pediatric risk:** Children are more prone to airway complications; desflurane induction risks failed induction and emergency complications. **Clinical Pearl:** In pediatric anesthesia, the standard approach is sevoflurane inhalational induction followed by IV access and maintenance with either sevoflurane or desflurane. Desflurane is never used for induction in children. ### Addressing the Distractors - **Option 0 (lower MAC, faster emergence):** Desflurane does have a higher MAC (6.0% vs 2.0%) and faster emergence, but these properties do not explain why it cannot be used for induction. The airway irritation is the limiting factor. - **Option 1 (non-irritating, suitable for induction):** This describes sevoflurane, not desflurane. Desflurane is the opposite — highly irritating and unsuitable for induction. - **Option 3 (minimal hepatic metabolism):** While desflurane undergoes less metabolism (~0.02%) than sevoflurane (~3–5%), this difference is not clinically significant and does not influence the choice of induction agent. Both are safe in terms of metabolite production. **Mnemonic:** **D**esflurane is **D**ifficult for induction (pungent); **S**evoflurane is **S**mooth for induction (non-irritating).