Critical limb ischemia (CLI) is associated with severe pain that is a therapeutic challenge whit therapeutic limits for the use of conventional analgesics medications. ultrasound-guided continuous sciatic block (CCBN) is strategy effective and safe to consider in this patients.

This prospective descriptive exploratory cohort study evaluates CCBN as a effective therapeutic tools for patients whit (CLI)

Critical limb ischemia is the final stage of peripheral vascular disease identified by resting pain greater than 2 weeks with ulcers or gangrene in 1 or both extremities. Pain relief is a therapeutic challenge due to its severity, which significantly affects the quality of life, and the comorbidities that occur frequently in these patients, which limits the use of analgesics medications. Regional techniques can play an important role as they are safe and effective in analgesic management . Within these we find the ultrasound guided continuous sciatic block as a strategy to consider in the periods of exacerbation of pain, as a bridge to a palliative or resolutive management.

Prospective descriptive exploratory cohort study.

Patients with a diagnosis of critical ischemia of the lower limb with severe pain and side effects of opioids will be included. A continuous ultrasound-guided sciatic nerve block with longitudinal approach will be performed, with no anti-aggregation or anticoagulation suspension, continuing with an infusion of Bupivacaine 0.1%

The primary outcome will be numerical pain rating scale (NPrs) and secondary outcome Pinprick test, catheter duration, opioid consumption reduction and side effects to it.

Inclusion Criteria:

• Patients with a diagnosis of critical ischemia of the lower limb with severe pain and side effects of opioids

Exclusion Criteria:

• Under 18 years old

Patients with a diagnosis of critical ischemia of the lower limb with severe pain and side effects of opioids over 18 years old who accept the interventional technique