High central neuraxial block
Can occur with deliberate or accidental injection of local anaesthetic drugs into the subarachnoid space. Symptoms are — in sequence — hypotension and bradycardia, difficulty breathing, paralysis of the arms, impaired consciousness, apnoea and unconsciousness. Progression through this sequence can be slow or fast.
Consider reduced dose of hypnotic drug to avoid further hypotension. A full induction dose will not be necessary if the patient's consciousness is already impaired.
Neuromuscular blockade may not be necessary for tracheal intubation if the patient is unconscious, paralysed and apnoeic.
Bradycardia:
Atropine: 0.6–1.2 mg
Glycopyrrolate: 0.2–0.4 mg
Hypotension:
Metaraminol: 1–2 mg boluses repeated
Phenylephrine: 50–100 µg boluses repeated or by infusion
Ephedrine: 6–12 mg boluses repeated up to max 30 mg (tachyphylaxis limits further usefulness)
Cardiac arrest → 2-1
Hypotension → 2-4
Bradycardia → 2-6
Local anaesthetic toxicity → 3-10