Regional Anesthesia and Pain Management Flashcards

A 58-year-old patient undergoes ultrasound-guided erector spinae plane (ESP) block at the T5 level for thoracic surgery analgesia. Post-procedure, the patient develops unexpected ipsilateral lower limb weakness. Which anatomical mechanism best explains this complication?

Answer: Direct spread of local anaesthetic to the ipsilateral lumbar paravertebral space via the erector spinae fascial plane

The ESP block deposits local anaesthetic deep to the erector spinae muscle and superficial to the transverse processes. The fascial plane is continuous craniocaudally, and large-volume injections can track inferiorly to the lumbar paravertebral space, potentially blocking lumbar nerve roots and causing lower limb motor weakness. This caudal spread has been documented in cadaveric and clinical studies and is the most plausible anatomical explanation for ipsilateral limb weakness remote from the injection site.

During a stellate ganglion block using an anterior paratracheal approach at C6, the patient suddenly develops contralateral Horner's syndrome 10 minutes after an apparently successful ipsilateral block. What is the most likely explanation?

Answer: Bilateral sympathetic trunk involvement due to epidural or intrathecal spread of local anaesthetic

Contralateral Horner's syndrome following a stellate ganglion block strongly suggests epidural or intrathecal spread of local anaesthetic, as the drug tracks medially through fascial planes or through the intervertebral foramina to affect the contralateral sympathetic chain at the spinal cord level. This is a recognised, potentially serious complication requiring immediate assessment for respiratory compromise due to phrenic nerve or recurrent laryngeal nerve involvement, and in severe cases, neuraxial spread.

A patient with chronic refractory complex regional pain syndrome (CRPS) type I of the right upper limb is being considered for spinal cord stimulation (SCS). Pre-operatively, which finding would most strongly predict a POOR long-term response to SCS at the cervical level?

Answer: Failure to achieve ≥50% pain relief during a standardised trial stimulation period

The most validated predictor of poor long-term SCS outcomes is failure to achieve at least 50% pain relief during a structured trial stimulation period (typically 5–10 days). This is the internationally accepted threshold used to determine permanent implantation candidacy, and failure to reach this benchmark during the trial period is the strongest predictor of inadequate long-term benefit. While opioid use and disease duration have some influence, the trial period response remains the gold-standard selection criterion per European and international guidelines.

When performing a transversus abdominis plane (TAP) block for laparoscopic colorectal surgery, which approach provides the most reliable analgesia for the upper abdominal port sites and specimen extraction incision at the umbilical level?

Answer: Subcostal TAP block performed bilaterally

The subcostal TAP block targets the thoracoabdominal nerves (T7–T9) that innervate the upper and periumbilical abdomen by depositing local anaesthetic in the plane between the rectus abdominis and the posterior rectus sheath, lateral to the xiphoid. The classic lateral TAP block covers only T10–L1 dermatomes and misses the upper abdominal quadrants. For laparoscopic colorectal surgery where upper port sites and umbilical incisions are surgically significant, subcostal TAP provides superior dermatomal coverage and has demonstrated better analgesic outcomes in comparative studies.

A 72-year-old patient on therapeutic enoxaparin (1 mg/kg twice daily) for deep vein thrombosis requires urgent hip fracture surgery. The last dose was administered 8 hours ago. According to ESRA (European Society of Regional Anaesthesia) guidelines, what is the minimum additional waiting period before performing a spinal anaesthetic?

Answer: 16 more hours (total 24 hours from last therapeutic dose)

ESRA guidelines specify that for therapeutic (twice-daily) dose low-molecular-weight heparin (LMWH), a minimum interval of 24 hours from the last dose is required before neuraxial blockade. Since the last dose was 8 hours ago, an additional 16 hours must elapse. This is distinguished from prophylactic LMWH dosing (which requires only 12 hours). Anti-Xa level monitoring may be used as an adjunct but does not replace the mandatory time interval in ESRA's risk-stratified algorithm for therapeutic LMWH, and the threshold of <0.1 IU/mL alone is insufficient without the time criterion being met.

A patient receiving a continuous popliteal sciatic nerve block with ropivacaine 0.2% at 8 mL/hr after Achilles tendon repair develops progressive ankle and foot weakness at 36 hours that was not present at 12 hours. The infusion is running correctly. What is the most appropriate next step?

Answer: Stop the infusion and perform urgent MRI of the lumbosacral spine to exclude epidural haematoma or compressive lesion

Progressive neurological deficit developing after an initially adequate peripheral nerve block must never be attributed solely to local anaesthetic accumulation without excluding a compressive or ischaemic lesion. New or worsening motor weakness at 36 hours — beyond the expected pharmacokinetic window for block progression — warrants urgent investigation. While epidural haematoma is more classically associated with neuraxial blocks, compressive neuropathy at the popliteal fossa (haematoma, tourniquet injury, positioning injury) is a real risk. Stopping the infusion removes the confound of ongoing local anaesthetic effect and allows neurological assessment; MRI identifies any compressive lesion requiring surgical decompression. Delaying diagnosis risks permanent neurological injury.