Failed Spinal Anesthesia: Possible Causes and Management

Primary Dosing Issue

The American Society of Anesthesiologists recommends a minimum dose of 7.5-10.5 mg (1.5-2.1 mL) of 0.5% hyperbaric bupivacaine for cesarean section, with standard practice using 10-15 mg (2-3 mL) to achieve a T4 sensory level 1

Incorrect identification of the subarachnoid space can result in an epidural block with the intended spinal dose, leading to inadequate sensory level and preserved motor function, as suggested by the American Society of Regional Anesthesia and Pain Medicine 2
The European Society of Anaesthesiology recommends careful placement of the spinal needle to avoid catheter or needle malposition, which can affect the trajectory of the spinal needle and lead to failed spinal anesthesia 3

The American Heart Association recommends against administering a repeat full spinal dose without careful consideration, as it carries a 1 in 4367 risk of high or total spinal block requiring cardiovascular and respiratory support 2, 4
The American Society of Anesthesiologists recommends monitoring block height every 5 minutes until no further extension is observed before declaring failure 1, 2

The European Society of Anaesthesiology suggests considering incremental epidural dosing through the CSE catheter if properly positioned and tested, as an alternative to repeat spinal dosing 3
The American Society of Anesthesiologists recommends providing supplemental analgesia with intravenous opioids and anxiolytics while preparing for alternative anesthesia, and offering conversion to general anesthesia if the block cannot be extended adequately 1