26 - 30 Physiology SBAs for the Primary FRCA
Question 26
You are anaesthetising a 74 year old woman for a total hip replacement, and elect to perform a lumbar plexus block.
Which nerve is not likely to be affected?
- Genitofemoral nerve
- Ilioinguinal nerve
- Sciatic nerve
- Femoral nerve
- Obturator nerve
Answer
- Sciatic nerve
A lumbar plexus block targets the nerve roots from L1-5, affecting the following nerves:
- Subcostal
- Iliohypogastric
- Ilioinguinal
- Lateral cutaneous nerve of the thing
- Femoral
- Genitofemoral
- Obturator
The bigger the dose of local anaesthetic given during a lumbar plexus block, the more of these will be blocked.
The sciatic nerve originates from the lumbosacral plexus (L4-S3) and will not be affected by a lumbar plexus block.