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Dear Pain Matters blog readers,
I really like this case! This is because it explores the outcome of 2 different nerve blocks done on a young cadet (‘Sue’) with complex regional pain syndrome (CRPS) in her lower right leg.
Sue’s 1st nerve block via lateral sciatic catheter resulted in improved but incomplete pain relief. This 1st nerve block had inadvertently missed a certain branch of the sciatic nerve (more later).
As such, a 2nd (i.e. replacement) nerve block via posterior sciatic catheter was required.
Fortunately for Sue, ALL of her pain due to CRPS was finally eliminated once her replacement continuous sciatic catheter was correctly placed.
Sue, a young 17-year old female US Military Academy cadet, had a right ankle sprain due to an inversion injury during training. This sprain led to severe pain that radiated upward from her ankle. Sue’s ankle was swollen and the lateral part* of her lower leg and foot was numb. Her foot’s range of motion was very limited.
Within only 1 week, Sue’s orthopaedic surgeon diagnosed early CRPS after confirming severe pain and allodynia as well as vasomotor dysfunction. After 2 weeks of unsuccessful pain medicine treatment, Sue was transferred to Walter Reed Army Medical Center (WRAMC).
By now, Sue’s right foot was red, warm and swollen while her lower right leg displayed colour changes. Her lower leg, particularly the lateral side, and the top of her foot were sensitive to light touch. She had allodynia in the L5 and S1 dermatomes.
Distribution of dermatomes including L5 and S1 dermatomes (Hancock, 2011)
After a failed lumbar sympathetic block that did nothing for her pain, Sue received a ketamine infusion (that was titrated up to the maximum dose the following day).
1st CONTINUOUS SCIATIC NERVE BLOCK VIA LATERAL SCIATIC CATHETER
When Sue was admitted to the Surgical Intensive Care Unit (ICU) for a continuous lateral sciatic catheter placement, her pain levels were 8 out of 10.
Once Sue’s sciatic nerve was located in the popliteal fossa (i.e. knee pit),* and after this nerve’s division into its tibial and common peroneal nerve branches was identified,* the continuous nerve block catheter was placed proximal* to this nerve’s division. The correct placement of this catheter was necessary to achieve a continuous lateral sciatic nerve block.
The needle was then placed next to the sciatic nerve and a single dose of 20 mL 1.5% Mepivacaine with Epinephrine was injected into the nerve sheath.
Thereafter, a continuous infusion of 0.2% Ropivacaine was commenced (10 mL per hour). Sue was also given the option of adding a patient-controlled bolus dose of 3 mL every 20 minutes.
Sue was unable to move her foot up and down shortly after the Ropivacaine infusion started.
Guess what happened next??
Within only 15 minutes, Sue’s pain levels dropped from 8 to 1 (out of 10)! Wow!!
The Ropivacaine and Ketamine infusions continued throughout the night.
The next day, Sue continued to enjoy excellent pain relief in most of her CRPS-affected lower leg, with one notable exception:
There was burning pain and allodynia on the lateral part of her lower leg, just beneath her knee.
The pain in this particular dermatome can not be blocked by the 1st block called a lateral sciatic nerve block. Instead, a different kind of sciatic nerve block was needed.
As such, the Ropivacaine infusion was stopped for 8 hours (during which time Sue’s pain levels rose to 5/10). During this time, a ‘new and improved’ continuous posterior sciatic catheter was placed. This 2nd catheter was precisely located to also target the cutaneous branch of the sciatic nerve (that had inadvertently been overlooked by the 1st catheter).
2nd CONTINUOUS SCIATIC NERVE BLOCK VIA POSTERIOR SCIATIC CATHETER
Guess what happened after the first catheter was replaced and bolus of 30 mL of 0.5% Ropivacaine was released??
Sue finally had nil pain! Nada! Zilch! Zero! Even the lateral part of her lower leg was finally pain free! OMG!
The next morning, Sue was also able to move her foot without pain.
While her Ketamine and Ropivacaine infusions continued for another 3 days, Sue continued to enjoy complete pain relief.
Despite cessation of both infusions after the 4th day, Sue remained completely pain free.
Sue had physiotherapy and was able to bear weight on her CRPS-affected ankle without pain. Her ankle joint had full range of motion.
Upon discharge, Sue returned to cadet training. Half a year later, she was still pain free and able to perform all her cadet duties. Sue also enjoyed running without pain and was training for a marathon.
This case highlights the importance of:
- Early diagnosis; and
- Timely and effective pain treatment
1. The Importance of Early Diagnosis
Specifically, the earlier a diagnosis of CRPS is made, the less pain and suffering.
Early diagnosis of CRPS is a prerequisite to timely and effective treatment thereof.
In Sue’s case, her orthopaedic surgeon (one of her guardian angels!) diagnosed CRPS within only 1 week (!) after her ankle sprain.
Think about that! Only 1 week!!
2. The Importance of Timely and Effective Pain Treatment
If treatment for CRPS (via a precision nerve block or otherwise) is both timely and effective, this can lead to rapid recovery from CRPS.
Sometimes different treatments need to be tried out before the most effective treatment protocol is found.
Here, we learned that whilst partially effective, the 1st catheter (i.e. lateral sciatic catheter) was unable to block the residual pain on the lateral side of her lower leg, just underneath her knee.
In other words, Sue’s 1st Ropivacaine infusion was not properly placed to also block the cutaneous branches of the common peroneal nerve branches that innervate the lateral area of her lower leg, just below her knee.
As such, the anaesthetist (another one of Sue’s guardian angels!) replaced the original lateral sciatic catheter with a new posterior sciatic catheter (Everett et al, 2009).
It is clear that with a dedicated, professional and caring pain management team, the chances of recovery from CRPS are greatly enhanced.
In Sue’s case, her pain due to CRPS was completely eliminated within only 1 month. As such, Sue was able to return to an active and rewarding life and career shortly after.
This is good news for everyone!
* Lateral is the side of the body or limb that is away from the middle (i.e. farther from the middle).
* A popliteal fossa (a.k.a. knee pit) is a shallow depression behind the knee joint and knee cap.
* The sciatic nerve’s division into its tibial and common peroneal nerve branches was initially identified via ultrasound guidance.
This nerve’s division was identified via neurostimulation when the replacement posterior sciatic catheter was placed.
* Proximal means closer to the centre of the body.
(1) Everett et al. A Unique Presentation of Complex Regional Pain Syndrome Type I Treated with a Continuous Sciatic Peripheral Nerve Block and Parenteral Ketamine Infusion: A Case Report. Pain Med (2009);10(6):1136-9.
(2) Hancock et al. Diagnostic accuracy of the clinical examination in identifying the level of herniation in patients with sciatica. Spine (2011);36(11):E712-E719.