Which injection( drug) is contraindicated in head injury regarding pain
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Morphine is contraindicated in head injury for pain relief.
Why?
The mechanism is well-explained in Lippincott Illustrated Reviews: Pharmacology:
"Because of respiratory depression and carbon dioxide retention, cerebral vessels dilate and increase cerebrospinal fluid (CSF) pressure. Morphine is usually contraindicated in individuals with head trauma or severe brain injury."
Key reasons morphine is dangerous in head injury:
| Mechanism | Consequence |
|---|---|
| Respiratory depression | ↑ PaCO₂ (hypercapnia) |
| Hypercapnia → cerebral vasodilation | ↑ Intracranial pressure (ICP) |
| ↑ ICP | Worsens brain herniation risk |
| Miosis (pupil constriction) | Masks neurological assessment (pupillary reflex monitoring becomes unreliable) |
| Sedation/CNS depression | Impairs accurate GCS scoring and neuro monitoring |
| Nausea & vomiting | Increases ICP further (Valsalva effect) |
In summary:
Morphine (and opioids in general) are contraindicated in head injury primarily because:
- They cause CO₂ retention → cerebral vasodilation → raised ICP
- They mask neurological signs critical for monitoring (pupil size, GCS)
For analgesia in head injury patients when necessary, fentanyl is sometimes preferred over morphine (shorter acting, less histamine release, more titratable), but even then it is used with great caution.
- Lippincott Illustrated Reviews: Pharmacology, p. 712
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