<s>[INST] context: Drug must have entered subarachnoid space and resulted in total spinal anesthesia. The occurrence of a high regional block or total spinal can be potentially catastrophic and require immediate management. They may occur following spinal or epidural anaesthesia and therefore can occur outside of the operating theatre. Both are due to the inappropriately high spread of local anaesthetic affecting spinal nerves and as such are on a continuum of severity: ? High spinal/regional block: spread of local anaesthetic affecting the spinal nerves above T4. The effects are of variable severity depending upon the maximum level that is involved, but can include cardiovascular and/or respiratory compromise. ? Total spinal: intracranial spread of local anaesthetic resulting in loss of consciousness. A total spinal can also occur following epidural anaesthesia/analgesia. As the above are different severities of the same process, they may both be referred to as high regional block. Left untreated, a high regional block can progress to a total spinal. TOTAL spinal anesthesia is a complication that follows inadveent introduction of local anesthetics into the intracranial subarachnoid space. Clinical features- Hypotension, bradycardia , respiratory depression followed by neurological symptoms. The clinical features are dependent on the level of the spinal nerves affected by the local anaesthetic. Untreated the block may ascend fuher leading to more severe features as shown below: Spinal level Area(s) affected Symptoms/signs T1-T4 Cardiac sympathetic fibres blocked Hypotension Bradycardia C6-C8 Hands and arms Paraesthesia or numbness in hands/arms Weakness of hands/arms Shoness of breath (accessory respiratory muscles affected) C3-5 Diaphragm and shoulders Shoulder weakness - respiratory compromise immenent Hypoventilation and/or desaturation Respiratory arrest Intracranial spread - Brain stem Slurred speech Sedation Loss of consciousness [/INST] question: A patient aged 28 years, was given epidural anesthesia with 15 ml of 1.5% Lignocaine with adrenaline for hernia surgery. He developed hypotension, respiratory arrest and became unconscious within 3 minutes, most probable cause will be:- | options: A: Intravascular injection of Lignocaine B: Total spinal block C: Anaphylaxis to lignocaine D: High spinal block | answer: B </s>