A 62-year-old woman is still not awake 6 hours after clipping of a cerebral aneurysm for a Grade 1 Sub-Arachnoid Haemorrhage. List the potential causes and outline your management strategy.
Potential causes of delayed awakening early after surgical clipping of a SAH include specific neurological causes (rebleeding, cerebral infarction/ischaemia [including intra- operative technical problems, hypotension]; too early for vasospasm), metabolic causes (including hypothermia, hypo- or hyper-natraemia and hypo- or hyper-glycaemia, hyper- or hyper-capnia) and pharmacological causes (including prolonged effects of sedatives [relative or absolute] and muscle relaxants [not reversed or prolonged/excessive effects: including suxamethonium apnoea].
Management strategy requires exclusion of treatable causes prioritised according to their urgency. Early consultation with the treating neuro-surgical team is critical. Clinical history and examination reveal details of drugs used (including amounts and timing of doses), temperature, ventilation, haemodynamics, and identifies specific surgical issues/problems. Specific investigations that should be considered range from bedside (eg. nerve stimulator to assess residual neuromuscular blockade, or BIS monitor to assess EEG) and simple blood tests (eg. blood gases [oxygenation and exclude significant abnormalities in ventilation], electrolytes [especially Na] and glucose), to more complex and invasive (eg. repeat head CT [to exclude re-bleed, ischaemia] or angiography). These latter investigations would be organised in concert with the treating neuro-surgical team.
The approach to this unconscious patient is going to be vary similar to the generic Approach to the unconscious patient in the ICU except you will have some strong suspicions.
Let us recall the broad list of differentials for unconsciousness, and select from it only those which can be sensibly applied in this instance:
With focal neurological signs
Without focal neurological signs
Endocrine and metabolic causes:
The remaining causes:
- Use of long-acting sedatives (eg. thiopentone) in theatre
- Delayed drug metabolism post-operatively
- Hypothermia and delayed rewarming postoperatively
- Metabolic abnormalities (glucose, CO2)
- Cerebral infarction
- Contusions due to retraction
- Re-bleeding from the aneurysm
- Non-convulsive status epilepticus
Approach to management
- Ensure the ABCs are stable:
- Collect routine bloods and correct the correctable metabolic abnormalities
- Inform the neurosurgeon
- Ask the anaesthetist regarding the specifics of the operation
- Get a CT brain
- Consider an EEG
- Avoid sedatives and muscle relaxants