22.1 Neurocritical Care: Subarachnoid Haemorrhage, Stroke, Status Epilepticus and Acute Neuromuscular Failure

22.1 Neurocritical Care: Subarachnoid Haemorrhage, Stroke, Status Epilepticus and Acute Neuromuscular Failure

General Principles

The aims of neurocritical care are to prevent secondary brain injury and to treat the primary cause. Secondary insults include hypoxaemia, hypotension, hypercapnia or excessive hypocapnia, hyperthermia, hypo- and hyperglycaemia, seizures and raised intracranial pressure. The principles of intracranial pressure management are covered in the neurophysiology and neuroanaesthesia sections.

Aneurysmal Subarachnoid Haemorrhage (SAH)

Presentation and Grading

Sudden severe ("thunderclap") headache, neck stiffness, vomiting, reduced consciousness and focal signs. Diagnosis: non-contrast CT (very sensitive in the first 6 hours), lumbar puncture for xanthochromia if CT is negative after 6 hours, and CT angiography to identify the aneurysm.

Early Management

• Secure the airway if GCS is 8 or less; avoid hypoxaemia and hypercapnia.
• Control blood pressure before the aneurysm is secured (commonly systolic below about 160 mmHg), balancing rebleeding risk against cerebral perfusion.
• Nimodipine 60 mg orally (or enterally) every 4 hours for 21 days reduces poor outcomes; intravenous nimodipine causes more hypotension.
• Secure the aneurysm early (ideally within 24-72 hours) by endovascular coiling or surgical clipping. The ISAT trial showed better 1-year independence with coiling for suitable aneurysms.
• Antifibrinolytics are not routinely recommended (the ULTRA trial showed no improvement in outcome).

Complications

The old "triple-H" therapy (hypertension, hypervolaemia, haemodilution) has been abandoned; prophylactic hypervolaemia causes complications without benefit.

Acute Stroke

Ischaemic Stroke

• Thrombolysis: alteplase 0.9 mg/kg (10% bolus, rest over 1 hour, maximum 90 mg) or tenecteplase within 4.5 hours of onset after CT excludes haemorrhage; selected patients with unknown onset may be treated using advanced imaging.
• Mechanical thrombectomy for proximal anterior circulation large-vessel occlusion, within 6 hours and up to 24 hours in selected patients with salvageable tissue on imaging.
• Blood pressure: keep below 185/110 mmHg before thrombolysis and below 180/105 mmHg for 24 hours afterwards.
• Anaesthesia for thrombectomy: conscious sedation or general anaesthesia are both acceptable; avoid hypotension and delays.
• Malignant middle cerebral artery infarction: decompressive hemicraniectomy within 48 hours reduces mortality in selected patients under about 60 years.

Intracerebral Haemorrhage

• Rapid blood pressure lowering to a systolic target of about 140 mmHg (avoiding falls below about 110-120 mmHg) is considered safe.
• Reverse anticoagulation promptly: prothrombin complex concentrate and vitamin K for warfarin, idarucizumab for dabigatran, andexanet alfa or prothrombin complex concentrate for factor Xa inhibitors.
• Platelet transfusion is not beneficial for patients on antiplatelet drugs who are not having surgery (PATCH trial).

Status Epilepticus

Convulsive status epilepticus is now defined as seizure activity lasting 5 minutes or more (time point t1), or recurrent seizures without recovery; long-term consequences become likely after about 30 minutes (t2).

0-5 min    ABC, oxygen, glucose check (give glucose if low; thiamine first if alcohol misuse)
5-20 min   FIRST LINE - benzodiazepine:
           lorazepam 4 mg IV (repeat once), or diazepam 10 mg IV,
           or midazolam 10 mg buccal/IM if no IV access
20-40 min  SECOND LINE - one of:
           levetiracetam 60 mg/kg (max 4,500 mg), sodium valproate 40 mg/kg (max 3,000 mg),
           or fosphenytoin/phenytoin 20 mg/kg PE (ESETT: similar efficacy)
40-60 min  REFRACTORY - general anaesthesia with propofol, midazolam or thiopental;
           intubate, ventilate, continuous EEG to confirm seizure suppression

• Avoid valproate in women of childbearing potential where possible and in liver disease; phenytoin needs ECG monitoring (arrhythmias, hypotension) and causes tissue injury if extravasated.
• Non-convulsive status may follow; continuous EEG is needed in patients who do not wake.
• Look for causes: drug withdrawal, hypoglycaemia, hyponatraemia, infection, alcohol, eclampsia, structural lesions.

Acute Spinal Cord Injury

• Immobilise appropriately, and use manual in-line stabilisation during intubation; videolaryngoscopy reduces cervical movement.
• Maintain mean arterial pressure of about 85-90 mmHg for the first 5-7 days in some guidelines to support cord perfusion; treat neurogenic shock with fluids, vasopressors and atropine for bradycardia.
• High-dose methylprednisolone is no longer recommended routinely.
• Suxamethonium is safe only in the first 24-48 hours after injury.
• Lesions at C3-C5 affect diaphragmatic function and often need ventilation.

Acute Neuromuscular Respiratory Failure

Guillain-Barré Syndrome

• Ascending weakness, areflexia and autonomic instability, often after infection (for example Campylobacter).
• Intravenous immunoglobulin (0.4 g/kg/day for 5 days) or plasma exchange are equally effective; corticosteroids are not.
• About 20-30% need mechanical ventilation.

Myasthenic Crisis

Respiratory failure from myasthenia gravis, often triggered by infection, surgery or drugs (aminoglycosides, magnesium, fluoroquinolones). Treat with ventilatory support, plasma exchange or immunoglobulin, and corticosteroids, and temporarily withhold anticholinesterases in ventilated patients to reduce secretions.

Criteria for Ventilation (the "20/30/40 rule")

Other indications include bulbar dysfunction with aspiration risk, a rising $P_a\text{CO}_2$ or a rapid decline. Oxygen saturation and blood gases are late markers in neuromuscular failure, so serial vital capacity is essential.