Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks for persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial
Anesthesia & Analgesia, 05/31/2012
Bischoff JM et al. – Ultrasound–guided lidocaine blocks of the ilioinguinal and iliohypogastric nerves, at the level of the anterior superior iliac spine, are not useful in diagnosis and management of persistent inguinal postherniorrhaphy pain.Methods
- A randomized, double–blind, placebo–controlled, crossover trial in 12 patients with severe persistent inguinal postherniorrhaphy pain, including a control group of 12 healthy controls, was performed.
- Assessments included pain ratings under standardized conditions with numerical rating scale (0–10), sensory mapping to a cool roller, and quantitative sensory testing (QST), in the groin regions, before and after each ultrasound–guided block.
- A needle approach of 1 to 2 cm superior and medial to the anterior superior iliac spine was used.
- Outcomes were changes in pain ratings, sensory mapping, and QST compared with preblock values.
- Lidocaine responders were a priori defined by a pain reduction of ≥80% after lidocaine block and ≤25% after placebo block, nonresponders by pain reduction of <80% after lidocaine block and ≤25% after placebo block, and placebo responders by pain reduction of >25% after placebo block.
- One of 12 pain patients was a lidocaine responder, 6 patients were nonresponders, and 5 patients were placebo responders.
- No consistent QST changes were observed in patients after the lidocaine block.
- In 10 of 12 healthy controls, a cool hypoesthesia area developed in the groin after the lidocaine block.
- Furthermore, QST assessments demonstrated significantly decreased suprathreshold heat pain perception in the groin after lidocaine versus placebo blocks (95% confidence interval = –3.5 to –0.5, P = 0.008).