Ketamine is contraindicated in?
**Core Concept**
Ketamine is a medication used for starting and maintaining anesthesia, as well as for sedation in procedures. It works by inhibiting NMDA receptors in the brain, which are involved in the modulation of pain perception and emotional responses. Ketamine's mechanism of action is complex and multi-faceted, but its ability to disrupt NMDA receptor function is key to its anesthetic properties.
**Why the Correct Answer is Right**
Ketamine's contraindications are largely related to its potential to increase blood pressure, heart rate, and intracranial pressure. It is also known to cause hallucinations and other psychoactive effects, which can be problematic in certain patient populations. One of the most significant contraindications for ketamine is **severe hypertension**, as it can exacerbate existing cardiovascular disease and lead to cardiovascular complications. Additionally, ketamine can increase intracranial pressure, making it a relative contraindication in patients with head injuries or increased intracranial pressure.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a contraindication for ketamine. While ketamine can cause respiratory depression, it is not a primary contraindication.
**Option B:** This option is not a contraindication for ketamine. While ketamine can cause increased heart rate and blood pressure, it is not a contraindication in patients with a history of hyperthyroidism.
**Option C:** This option is not a contraindication for ketamine. While ketamine can cause increased intracranial pressure, it is not a contraindication in patients with a history of epilepsy.
**Clinical Pearl / High-Yield Fact**
Ketamine's potential to increase intracranial pressure and exacerbate cardiovascular disease makes it a relative contraindication in patients with head injuries or severe hypertension. It is essential to carefully evaluate the risks and benefits of ketamine use in these patients.
**Correct Answer: C. Severe hypertension.**