Spinal Anaesthesia
An injection of anaesthetic agent, typically Diamorphine or 0.5% Heavy Marcaine, into the intrathecal space and the cerebrospinal fluid of the subarachnoid space, around the lower spinal nerves, below L2, so as to avoid piercing the spinal cord. This produces a temporary block of the sensory, motor, and autonomic nerves, which come into contact with the anaesthetic.

The sensory block gives the required analgesia, but the associated motor block causes weakness or paralysis, whilst the autonomic block causes vasodilation of blood vessels within the distribution of the block. Because of this vasodilation, blood pressure may fall, and vasoconstrictor drugs must be made available to counter this fall.

A 'spinal' is suitable for procedures below the umbilicus. Onset is a few minutes, and duration is 2-3 hours.
Injection point:
The vertebral level of the injection influences the rate of spread of the block, as does the amount of local anaesthetic injected, and the position of the patient. Injection is usually made below the 2nd Lumbar vertebra, as this is the level at which the spinal cord terminates, and there should be less risk of nerve damage from the needle below this level.
Fine bore needles are used, with "pencil" point and smallest gauge being least likely to cause post-spinal headache, which is caused by CSF leakage through the hole in the dura, made by the needle.
Total Spinal Anaesthesia
High spinal block: Local anaesthetic depression of the cervical spinal cord and brainstem, which may result from excessive spread of an intrathecal injection of local anaesthetic, or inadvertent spinal injection of an epidural dose of local anaesthetic.
Prior to the above symptoms, the patient may complain of nausea, or tingling in the fingers, which may be due to a high block at the level of T1.
Hypotension can be treated with:
Bradycardia treatment is by anticholinergics, such as Atropine, or β-adrenergic agonists, such as ephedrine.

Breathing difficulty should be managed with proper ventilation and vasopressors (eg Ephedrine).

If treatment is ineffective, the patient may have to be induced by rapid sequence, and ventilated by IPPV.