Inhalational agents are critical for the maintenance of general anaesthesia. Potency is measured by Minimum Alveolar Concentration (MAC), defined as the concentration that prevents movement in 50% of patients in response to painful stimuli.
Clinical Profiles of Common Agents
| Agent | Key Clinical Profile |
|---|---|
| N2O | Low potency; possesses analgesic properties; carries risks of diffusion hypoxia and expansion of air-filled spaces. |
| Halothane | Associated with “Halothane hepatitis” and cardiac sensitization to catecholamines. |
| Enflurane | Associated with seizure-like EEG changes; now largely obsolete. |
| Isoflurane | Stable with a pungent odor; causes coronary vasodilation, posing a “coronary steal” risk. |
| Desflurane | Rapid onset/offset due to low solubility; pungent (causes airway irritation); associated with sympathetic surge. |
| Sevoflurane | Fast-acting and non-irritating; excellent for pediatric inhalational induction. |
High-Yield Clinical Pearls
- Malignant Hyperthermia (MH): All halogenated volatile agents are potential triggers for MH, a hypermetabolic state managed with dantrolene.
- Blood-Gas Solubility: Agents with lower solubility, such as Desflurane and Sevoflurane, result in a faster wash-in and wash-out.
- Nitrous Oxide (N2O) Contraindications: It is contraindicated in patients with bowel obstruction, pneumothorax, or middle ear surgery because it diffuses rapidly into air-filled spaces.
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