A patient was admitted epidural anaesthesia with 15 ml of 1.5%. Lignocaine with adrenaline for hernia surgery. He devoled hypotension and respiratory depression within 3 minutes after administration of block. The most common cause would be –
Hypotension and respiratory depression after epidural anesthesia suggest high spinal anesthesia.
High spinal anesthesia, i.e. spinal anesthesia ascending into the cervical levels, can occur following attempted epidural / caudal anesthesia if there is inadverent intrathecal injection. High spinal anesthesia causes severe hypotension, bradycardia, and respiratory insufficiency.

Causes of high spinal anesthesia :

Administration of excessive dose during spinal anesthesia,
Unusual sensitivity or spread of local anesthetic,
Failure to reduce standard dose in selected patients (elderly, pregnant, obese or very short),
Inadverent intrathecal injection during epidural anesthesia.
Allergy to drug administered
Systemic toxicity to drug administered
Patient got vasovagal shock
Drug has entered the subarachnoid space