What is the role of subarachnoid blocks in pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Subarachnoid block, also termed spinal anesthesia (SA), can be achieved with small amounts of LA (eg, 100-150 mg procaine, 50-100 mg lidocaine, 5-15 mg bupivacaine) placed into the subarachnoid space where it readily mixes with the CSF. SA produces a rapid onset of analgesia because the drug comes into direct contact with neural structures, especially nerve axons, without first traversing the epineurium and perineurium. Furthermore, SA is a relatively simple procedure when administered by experienced hands and allows better control of the degree and duration of neural blockade. LA solution can be made hyperbaric (ie, specific gravity CSF), which allows the spinal level of the block to be controlled by changing the position of the patient.

Notwithstanding, these advantages of SA have limited value when managing patients with acute pain, and SA is rarely indicated as a therapeutic tool for patients with chronic pain. SA is frequently useful as a prognostic block prior to a subarachnoid injection of a neurolytic agent or for diagnostic purposes.


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