Pharmacological Causes
- Residual anaesthetic agents/opioids
- Residual Neuromuscular blockade
- Drug interactions (e.g., with anticonvulsants or sedatives)
2. Metabolic causes
- Hypoglycaemia or hyperglycaemia
- Electrolyte imbalances
- Hyponatremia (especially in posterior fossa surgery, due to SIADH or cerebral salt wasting)
- Hypernatremia
- Hypocalcaemia, hypomagnesemia
- Hypoxia or hypercapnia
- Hypothermia
- Acid-base disturbances
3. Neurological Causes
- Intracranial haemorrhage
- Cerebral infarction/oedema
- Raised intracranial pressure
- Seizures / non-convulsive status epilepticus
- Cerebral gas embolism
- Hydrocephalus or tension pneumocephalus
4. Surgical Complications
- Venous air embolism
- Tension pneumocephalus (Especially after craniotomy with air entry, classic “Mount Fuji sign” on CT)
- Inadequate brainstem perfusion or injury
- More common in posterior fossa surgery
5. Cardiorespiratory Complications
- Intraoperative hypotension / hypoperfusion
- Pulmonary embolism or fat embolism
- Arrythmia
