A 58-year-old woman with severe osteoarthritis of the knee is scheduled for total knee arthroplasty under general anesthesia with a femoral nerve block for postoperative pain control. During the block procedure using ultrasound guidance, the needle is advanced medial to the femoral artery and a 'pop' is felt as the needle penetrates the fascia iliaca. After injecting 25 mL of 0.5% bupivacaine, the patient develops sudden onset of severe lower abdominal pain, hypotension (BP 85/50), and tachycardia (HR 118). What is the most likely complication and the immediate next step?

Explanation

## Femoral Artery Puncture During Fascia Iliaca Block ### Clinical Presentation The combination of: - Severe lower abdominal pain (not localized to the leg) - Hemodynamic instability (hypotension, tachycardia) - Timing immediately after needle advancement and injection ...indicates **retroperitoneal hemorrhage from femoral artery puncture**, not simple compartment syndrome. ### Anatomical Context ```mermaid flowchart TD A[Fascia Iliaca Block Needle]:::action --> B{Needle depth/direction?}:::decision B -->|Medial to artery| C[Risk: Femoral artery puncture]:::urgent B -->|Lateral to artery| D[Safe: Fascia iliaca space]:::outcome C --> E[Retroperitoneal hemorrhage]:::urgent E --> F[Severe pain + hemodynamic collapse]:::urgent D --> F2[Successful block, no vascular injury]:::outcome ``` ### Why This Is Femoral Artery Injury **Key Point:** Retroperitoneal hemorrhage from femoral artery puncture presents with **severe lower abdominal pain** (not leg pain), **hemodynamic instability**, and **rapid deterioration**. The bleeding is contained within the retroperitoneal space, compressing organs and causing shock. **Clinical Pearl:** The femoral artery lies medial to the femoral nerve. If the needle is advanced medial to the artery (as stated in the vignette), direct arterial puncture is likely. The "pop" sensation suggests penetration of fascia, but the artery was already breached. ### Immediate Management 1. **Stop the injection immediately** — do not inject more local anesthetic 2. **Establish large-bore IV access** — two 18-gauge lines minimum 3. **Type and cross-match** — prepare for massive transfusion protocol 4. **Apply direct manual pressure** — over the femoral artery at the groin (above the inguinal ligament) to tamponade bleeding 5. **Notify vascular surgery urgently** — this is a surgical emergency 6. **Fluid resuscitation** — balanced crystalloid/colloid, but **do not over-resuscitate** (permissive hypotension until surgical control) 7. **Prepare for emergency angiography or surgical exploration** — CT angiography if hemodynamically stable enough; otherwise straight to OR **High-Yield:** In a hemodynamically unstable patient with retroperitoneal hemorrhage from femoral artery puncture, **do not delay for imaging** — go directly to the operating room for vascular repair or angiographic intervention. ### Why Other Options Are Wrong **Psoas compartment hematoma** (option 3) would cause localized leg swelling and pain, not severe abdominal pain or shock. Tranexamic acid alone is insufficient for arterial bleeding. **Intraperitoneal injection** (option 2) would cause peritonitis over hours to days, not immediate hemodynamic collapse. Abdominal pain would be diffuse and accompanied by peritoneal signs, not acute shock. **Epidural injection** (option 4) is anatomically impossible during a fascia iliaca block and would not cause acute abdominal pain or shock. [cite:Hadzic Textbook of Regional Anesthesia and Acute Pain Management Ch 18]