High or total spinal block
- Crisis
Sometimes the numbing medicine of a spinal or epidural spreads too high and weakens the breathing and the heart; the team supports both until it wears off.
What it is
A high neuraxial block is a spinal or epidural block that spreads further up the spinal cord than intended; a total spinal block reaches the cervical segments and the brainstem. It follows an unusually large spread of a spinal injection (high-placed injection, patient position, pregnancy, a hyperbaric drug in a head-down patient), a spinal given soon after a failed epidural, or an epidural dose that enters the cerebrospinal fluid because the needle or catheter crossed the dura or migrated. As the block climbs, it blocks the cardiac sympathetic fibres from the upper thoracic segments, causing bradycardia and profound hypotension; then the hands and arms weaken, the patient struggles to breathe and speak as the phrenic nerve roots are reached, and finally consciousness is lost with apnoea and dilated pupils. The block itself wears off with time, so treatment is supportive: oxygen, ventilation and intubation when breathing fails, and aggressive treatment of the circulation. With prompt recognition the outcome is good; delay leads to hypoxic cardiac arrest.
How to recognise it
- A block level rising faster or higher than expected after a spinal or an epidural top-up.
- Sudden hypotension and bradycardia, often with nausea, anxiety or a feeling of being unable to breathe.
- Tingling or weakness in the hands and arms, then a weak cough and a whispering voice.
- Difficulty swallowing and breathing, falling saturation, then apnoea.
- Loss of consciousness and dilated pupils when the drug reaches the brainstem: a total spinal.
Why it happens
- Local anaesthetic spreads within the cerebrospinal fluid beyond the intended segments, carried by volume, baricity and position.
- An epidural dose given into the cerebrospinal fluid by a catheter that has crossed the dura acts like a very large spinal.
- Block of the upper thoracic segments removes cardiac sympathetic drive, so heart rate and contractility fall while venous pooling lowers preload.
- Spread to the cervical roots that form the phrenic nerve weakens the diaphragm; spread to the brainstem stops breathing and consciousness.
- Pregnancy raises the risk because of a smaller epidural space, engorged epidural veins and aortocaval compression.
What to do at once
- Stop any injection and call for help — no more drug should go in, and the team will need several hands.
- Reassure the patient and give high-flow oxygen by mask — fear is real, and early oxygen protects against hypoxaemia.
- Support breathing with a bag and mask if it is weak — the diaphragm may fail before the patient loses consciousness.
- Intubate when breathing fails or airway reflexes are lost — this protects the lungs and allows controlled ventilation.
- Give anaesthesia or sedation once the airway is secured — the patient may be paralysed yet fully aware.
- Treat hypotension with fluids and vasopressors, adding adrenaline if severe — the circulation fails from lost sympathetic tone.
- Treat bradycardia with an anticholinergic, or adrenaline if severe — the block has removed the cardiac accelerator fibres.
- Raise the legs and, in pregnancy, displace the uterus to the left — this improves venous return to the heart.
- If cardiac arrest occurs, start advanced life support with early adrenaline — and in late pregnancy prepare for prompt delivery.
How high the block has reached and what it causes
| Segments reached | What the team sees |
|---|---|
| Mid-thoracic | Hypotension from vasodilation; nausea |
| Upper thoracic | Bradycardia and worse hypotension from loss of cardiac sympathetic fibres |
| Lower cervical | Tingling and weakness of the hands and arms, weak cough |
| Upper cervical | Diaphragm weakness: breathlessness, whispering voice, then apnoea |
| Brainstem | Loss of consciousness, dilated pupils, cardiovascular collapse: total spinal |
Costly mistakes
- Mistaking early hand weakness or a weak voice for anxiety and not checking the block level.
- Giving a large epidural top-up in one go, or without aspirating the catheter first.
- Tilting the patient steeply head-down after a hyperbaric spinal, which can carry the drug higher.
- Intubating and ventilating without giving anaesthesia, leaving an awake, paralysed patient.
- Treating bradycardia late: in a high block it can progress abruptly to asystole.
Next step
- Keep ventilating and supporting the circulation until the block regresses; this may take several hours.
- Call a senior anaesthetist at once; in obstetrics, involve the obstetric and neonatal teams and monitor the fetus.
- Decide with the team whether surgery continues under general anaesthesia once the patient is stable.
- Extubate only when the block has receded, breathing is strong and the patient obeys commands; observe in recovery or intensive care.
- Explain the event to the patient, document the drug, route and level reached, and review how the catheter or injection caused it.
Test yourself
Think of the answer, then tap the question to see it.
What are the early warning signs that a spinal or epidural block is spreading too high?
Hypotension and bradycardia, tingling or weakness in the hands and arms, a sense of breathlessness, a weak cough and a whispering voice.
Why does a high neuraxial block cause bradycardia?
It blocks the cardiac sympathetic (accelerator) fibres from the upper thoracic segments, leaving vagal tone unopposed.
After intubating a patient with a total spinal block, what must not be forgotten?
Anaesthesia or sedation: the patient may be fully paralysed by the block but still conscious and aware.
How is an epidural top-up given to reduce the risk of an unrecognised intrathecal injection?
After aspirating the catheter, in small increments, watching for a rapid rise in block level, low blood pressure or weakness before giving more.
Elsewhere in DurgiPedia
Connections
Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.
Sources: Spinal Anesthesia (StatPearls (NCBI Bookshelf), 2022); Epidural Anesthesia (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.