Question
| A. |
It is a direct myocardial depressant |
| B. |
Emergence phenomenon are more likely if anticholinergic premedication is used |
| C. |
It may induce cardiac dysarythmias in patients receiving tricyclic antidepressants |
| D. |
Has no effect on intracranial pressure |
|
Correct Answer » D Explanation |
 |
Ketamine is a phencyclidine derivative that produces dissociative anesthesia. It provides profound analgesia, amnesia, and sedation while preserving airway reflexes and spontaneous respiration. Its unique cardiovascular and central nervous system effects make it an important anesthetic agent in specific clinical situations.
Explanation of the Correct Answer
Option D. Has no effect on intracranial pressure – Correct (False statement)
- Ketamine can increase intracranial pressure (ICP) by increasing cerebral blood flow and cerebral metabolic activity.
- Therefore, it was traditionally avoided in patients with raised ICP.
- Although recent evidence suggests ketamine may be used safely in selected neurocritical care patients with controlled ventilation, it is incorrect to state that ketamine has no effect on intracranial pressure.
- Hence, this is the false statement and the correct answer.
Why the Other Options are Correct
Option A. It is a direct myocardial depressant
- True.
- Ketamine has a direct negative inotropic effect on the myocardium.
- In healthy individuals, this effect is usually masked by its potent sympathomimetic action, resulting in increased heart rate, blood pressure, and cardiac output.
- In patients with depleted catecholamine stores (e.g., prolonged shock or severe sepsis), the direct myocardial depressant effect may become clinically significant.
Option B. Emergence phenomena are more likely if anticholinergic premedication is used
- True.
- Ketamine may cause emergence reactions, including vivid dreams, hallucinations, and agitation.
- Anticholinergic drugs, particularly atropine, may increase the incidence of these phenomena.
- Premedication with benzodiazepines (e.g., midazolam) reduces the risk.
Option C. It may induce cardiac dysrhythmias in patients receiving tricyclic antidepressants
- True.
- Ketamine has sympathomimetic properties and increases circulating catecholamines.
- Patients taking tricyclic antidepressants (TCAs) have enhanced sympathetic responses, increasing the risk of hypertension and cardiac dysrhythmias.
