Paper I
Question
Compare Inhalational and intravenous general anesthetics (4+4)
Answer
| Feature | Inhalational anesthetics | IV anesthetics |
|---|---|---|
| Examples | Halothane, Isoflurane, Sevoflurane, Nitrous oxide | Thiopental, Propofol, Ketamine, Etomidate |
| Onset | Slower (depends on alveolar concentration/blood-gas partition coefficient) | Very rapid — within one arm-brain circulation time |
| Use | Maintenance of anesthesia, titratable depth throughout a long procedure | Induction of anesthesia; some (propofol) also used for maintenance/sedation |
| Control of depth | Easily titratable by adjusting inspired concentration | Less easily titratable once given as a bolus |
| Recovery | Depends on redistribution/elimination via lungs — generally smooth, agent-dependent | Rapid recovery from a single dose (redistribution-dependent) but can accumulate with repeated dosing |
| Equipment | Requires anesthesia delivery apparatus/vaporizer | Simple IV administration, no special apparatus |
| Airway/respiratory effects | Direct respiratory depression, airway irritability (older agents) | Marked respiratory depression/apnea on induction (especially thiopental, propofol) |
| Analgesic property | Nitrous oxide has analgesic property; volatile agents largely do not | Ketamine uniquely provides analgesia; most others (propofol, thiopental) have none |
Overall: IV agents are preferred for smooth, rapid induction; inhalational agents are preferred for maintaining a controllable depth of anesthesia over the course of surgery — the two are typically used together (IV induction, inhalational maintenance) rather than as alternatives.