Learning objectives

• Describe the contributing factors to high spinal anesthesia
• Apply preventative measures for high spinal anesthesia
• Describe the symptoms of high spinal anesthesia
• Manage cases of high spinal anesthesia

Definition & mechanisms

• High spinal anesthesia is a complication of central neuraxial techniques that include spinal and epidural anesthesia
• It is defined as a spread of local anesthetic affecting the spinal nerves above T4
• The effects are of variable severity depending on the maximum level that is involved but can include cardiovascular and/or respiratory compromise
• In total spinal anesthesia, there is an intracranial spread of local anesthetic resulting in loss of consciousness

Contributing factors

• Local anesthetic dose
• Positioning of patient
• Pre-existing epidural block
• Unrecognized dural puncture and intrathecal injection
• Accidental subdural block
• Accidental intradural space

Prevention

• Epidural analgesia/anesthesia:  

• • Use low concentrations of local anesthetic for labor analgesia  
  • Prior to top-up: 
    • Assess block (to guide top-up dosage)
    • Aspirate the epidural catheter with a 2 mL syringe to rule out intrathecal or intravenous placement  
  • Consider giving large volumes of local anesthetic in divided doses (clinical urgency may preclude this)

• Spinal anesthesia:  

• • Consider the level (and therefore local anesthetic dose) required for surgery  
  • Patient position: block height can be manipulated for up to 30 min when using hyperbaric (“heavy”) anesthetics – if using head down position to establish the block, remember to remove it as soon as possible 
  • Patient characteristics: consider dose reduction in short or morbidly obese patients  
  • Technique: 
    • Consider the effects of the speed of injection 
    • Avoid excessive barbotage  
  • If performing a spinal following an epidural, a dose reduction may be necessary depending on the existing level of block (reductions to 1-1.5 mL of local anesthetic have been suggested following a failed epidural top-up); there is no clear consensus on this

• Epidural and spinal anesthesia:  

• • Don’t inject during a contraction/cough/Valsalva maneuver as this can increase the cephalad spread of local anesthetic  
  • The use of the Oxford wedge is recommended to prevent the cephalad spread of local anesthetic (and to optimize airway positioning in the event of requiring general anesthesia)

Symptoms

Management

Suggested reading

• Sivanandan S., Surendran A. (2019) Management of total spinal block in obstetrics. Update in Anaesthesia, 34: 22-25.
• Reeve J. (2017) NHS Foundation trust clinical guideline: High Regional Block (including Total Spinal Anaesthesia). 

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