In general, almost all the side effects seen with spinal anaesthesia are due to the nerve blockade itself and not to the drug used. This effects include hypotension, bradycardia and postdural puncture headache.
High or Total Spinal Blockade: Severe adverse reactions following spinal anaesthesia are rare but may occur in connection with extensive (total) spinal blockade. Total spinal blockade will result in cardiovascular and respiratory depression. The cardiovascular depression is caused by an extensive sympathetic blockade which may result in profound hypotension and bradycardia or even cardiac arrest. Ventilatory depression is caused by blockade of the innervation of the respiratory muscles, including the diaphragm.
Neurological Reactions: Neurological damage is rare, though recognised, consequence of regional and particularly spinal anaesthesia. It may be due to several causes eg, direct injury to the spinal cord or spinal nerves, anterior spinal artery syndrome, injection of an irritant substance, injection of a nonsterile solution or the development of a space occupying lesion (haematoma or abscess) within the spinal canal. These may result in localised areas of paraesthesia or anaesthesia, motor weakness, loss of sphincter control of paraplegia. Occasionally, these are permanent. Neurological complications of this type have been reported with all local anaesthetics used for spinal anaesthesia.
Allergic Reactions: Allergy to amide-type local anaesthetics is very rare but may be present as allergic dermatitis, bronchospasm or anaphylaxis.
Acute Systemic Toxicity: Like all local anaesthetic drugs, bupivacaine may have acute toxic effects on the central nervous and cardiovascular systems, if given in high doses. The 1st manifestation of CNS toxicity is drowsiness merging into unconsciousness and respiratory arrest. The cardiovascular reaction is depression and may be characterised by hypotension, myocardial depression, bradycardia and possibly cardiac arrest. In view of the low dosage employed, systemic adverse reactions are rarely associated with spinal anaesthesia, but may occur after accidental intravascular injection. Systemic adverse reactions are characterised by numbness of the tongue, lightheadedness, dizziness and tremors, followed by convulsions and cardiovascular disorders.