Dr Stuart Myers

Axillary Blocks

Axillary Blocks

 
Peripheral Nerve Blockade For Hand Surgery

Uses:  
 
-  Postoperative pain relief - improved postoperative comfort

-  Reduction postoperative nausea and vomiting 

-  Lasts 8 -14 hours postoperatively   
-  Reduction intraoperative opiods                                                                                       
-  Possible reduced incidence postoperative complex regional pain syndrome (CRPS) 
 

Types:
 
- Axillary Block - in armpit (most common) +/- Catheter 
- Supraclavicular Block
 
What will you perceive from a successful block?
 
Loss of sensation and decreased ability to move your arm (the local anaesthetic affects 
both the motor and sensory nerve supply)
 
Method:
 
- The aim of the procedure is to place local anaesthetic around the major nerves supplying
 sensation to the arm and thus block sensory signals and therefore pain sensation.

- The procedure is performed prior with surgery and when still awake (although some
 medication which has relaxant and amnesic effects is given prior to commencement). 
This is done to reduce the risk of associated complications. 
 

- Most commonly involves placing a needle in the axilla (armpit) and using an ultrasound to
 identify where the nerves are. A device known as a nerve stimulator which again helps
 indentify the proximity of the needle to the nerve is also used.
 
- The nerve stimulator causes involuntary twitching of the arm and fingers. Usually 
described as a strange sensation rather than painful.
 
- Once the correct location is identified, local anaesthetic is injected under direct vision of  
the ultrasound (this helps reduce complications - see below). Injection of the local anaesthetic
 should not be painful. The aim is to instill local anaesthetic in the sheath surrounding the
 nerve, but not inject directly into the nerve. Injecting directly into a nerve is very painful
 and is more likely to result in nerve damage. You will be asked to report any severe pain 
when the injection is performed. If painful, the needle will be repositioned.
 
- As mentioned the block lasts for between 8 to 14 hours. As the block wears off, you will
 need alternate pain relief. This will be in the form of oral medication or a PCA (patient
 controlled analgesia). The PCA is attached to the drip and involves pressing a button to
 administer a dose of narcotic. It has a lockout time such that one cannot overdose whilst 
using it.
 
- Occasionally for procedures where it is perceived that you will benefit from a more prolonged
 period of nerve blockade, a catheter will be placed in the nerve sheath in order that a
 continuous infusion of local anaesthetic can be utilized.
 
- Once the block starts to wear off (usually perceived as pins and needles in the fingers), it is
 advisable to start pressing the PCA button or requesting oral analgesia. This is necessary as 
the block can wear off rapidly, resulting in a period of inadequate analgesia until the alternate
 medication starts to take effect, therefore it advisable to obtain the medication prior to
 complete reversal of the block.
 
Complications:
 
1. Nerve Damage –  occurs1/1000 to 1/10000 times the procedure is performed.
Presents as an area of sensory loss or occasionally hypersensitivity (may require medication).
 Less commonly motor weakness occurs.
Most cases of nerve damage recover within 6weeks to 3 months. Very occasionally more
 prolonged recovery or permanent damage.
 
2. Failure of block – can occur for various reasons. If this occurs alternate medication will be
 given. 
 
3.Intravascular injection – resulting in local anaesthetic toxicity – rare with techniques used.
 
4. Infection – low risk. Slightly higher risk if catheter is left the nerve sheath. (you will be 
placed on preventative antibiotics if you have a catheter)