From the Guidelines
Lidocaine in the subarachnoid space can cause severe complications, including permanent nerve damage and neurotoxicity.
Complications of Lidocaine in the Subarachnoid Space
- Neurological complications: The use of lidocaine in the subarachnoid space has been associated with neurological complications, including cauda equina syndrome and permanent nerve damage 1.
- High- and total-spinal blocks: Inadvertent administration of an epidural dose of local anaesthetic via an intrathecal catheter can result in high- or total-spinal blocks, hypotension, and even respiratory or cardiac arrest 1.
- Risk of dosing errors: The risk of dosing errors during intrathecal catheter use highlights the importance of clear labelling of catheters, good communication, and handover between healthcare professionals 1.
- Monitoring and management: The anaesthetist needs to be vigilant in monitoring the patient for signs of developing a high block, and management should include supporting the circulation with vasopressors and fluids, supplemental oxygen, and tracheal intubation and ventilation if necessary 1.
Key Considerations
- Test dosing: The ideal test dose to exclude a misplaced catheter has yet to be identified, but a dose of 10 mg bupivacaine (or equivalent) may allow recognition of an intrathecal catheter while minimising the risk of high- or total-spinal anaesthesia 1.
- Catheter aspiration: Catheter aspiration is not entirely reliable in determining catheter position, and failure to aspirate CSF does not exclude positioning within the subarachnoid space 1.
- Slow and incremental dosing: Slow and incremental dosing must always be used when giving any top-up to minimise the risk of high- or total-spinal anaesthesia 1.
From the FDA Drug Label
In the practice of caudal or lumbar epidural block, occasional unintentional penetration of the subarachnoid space by the catheter may occur. Subsequent adverse effects may depend partially on the amount of drug administered subdurally These may include spinal block of varying magnitude (including total spinal block), hypotension secondary to spinal block, loss of bladder and bowel control, and loss of perineal sensation and sexual function Persistent motor, sensory and/or autonomic (sphincter control) deficit of some lower spinal segments with slow recovery (several months) or incomplete recovery have been reported in rare instances when caudal or lumbar epidural block has been attempted.
Underventilation or apnea due to unintentional subarachnoid injection of local anesthetic solution may produce these same signs and also lead to cardiac arrest if ventilatory support is not instituted
The complications of lidocaine in the subarachnoid space include:
- Spinal block of varying magnitude, including total spinal block
- Hypotension secondary to spinal block
- Loss of bladder and bowel control
- Loss of perineal sensation and sexual function
- Persistent motor, sensory, and/or autonomic deficit of some lower spinal segments with slow recovery or incomplete recovery
- Underventilation or apnea, which can lead to cardiac arrest if ventilatory support is not instituted 2 2
From the Research
Complications of Lidocaine in the Subarachnoid Space
- The subarachnoid administration of lidocaine has been associated with various neurological complications, including cauda equina syndrome and transitory neurological symptoms 3.
- Cauda equina syndrome is mainly associated with continuous subarachnoid anesthesia through microcatheters, while transitory neurological symptoms are associated with single injections 3.
- The incidence of transitory neurological symptoms is higher with lidocaine compared to other local anesthetics 3.
- The underlying mechanism of these complications is unclear, but possible factors include the neurotoxicity of lidocaine itself or the malpositioning of the paravertebral musculature due to extreme relaxation 3.
- Other factors that can contribute to neuropathy include arthroscopy and lithotomy positions, early ambulation, and the use of small-gauge needles or pencil-point needles 3.
Specific Complications
- Focal myelomalacia and syrinx formation can occur as complications of lumbar spinal anesthesia due to accidental injection of lidocaine into the substance of the spinal cord 4.
- Severe sharp and shooting pain in both lower limbs, as well as sensory and motor deficits, can occur as a result of these complications 4.
- Carbamazepine and gabapentin may be effective in providing symptomatic relief of pain associated with these complications 4.
Neurotoxicity
- The neurotoxicity of lidocaine and other local anesthetics has been evaluated in animal studies, with results suggesting that no local anesthetic or solution is more neurotoxic than another when injected in large volumes into the subarachnoid space 5.
- However, case reports have described prolonged neurologic deficit after accidental spinal anesthesia with large volumes of local anesthetics, including lidocaine 5.
Fatal Complications
- Accidental subarachnoid injection of lidocaine and other local anesthetics can be fatal, with reported cases of cardiac and respiratory arrest 6.
- Toxicological analysis can help establish the cause of death in such cases, with detection of lidocaine and other local anesthetics in blood, cerebrospinal fluid, and urine 6.