Introduction

Ultrasound-guided nerve blocks in emergency care are an expanding area of interest and research.

While traditional “blind” or landmark-based nerve blocks (such as radial, median, and ulnar blocks performed at the wrist using anatomic landmarks) are frequently performed in emergency care settings,^1,2 the use of ultrasound to perform real-time injection of an anesthetic agent around a target nerve is a newer application in the emergency department (ED). Ultrasound guidance for abdominal wall,³ sciatic,⁴ tibial,⁵ sural,⁶ intercostal,⁷ brachial plexus,⁸ and forearm nerve blocks has been shown to be efficacious in emergency care settings.⁹ Ultrasound guidance is also used with increasing frequency in the pediatric population.¹⁰ This article will focus on performing ultrasound-guided radial, median, and ulnar nerve blocks, together termed the “forearm nerve blocks.”

For background, a review of the basic motor and sensory functions of the radial, median, and ulnar nerves and the appropriate clinical examination to test their function is helpful (Table 1).

Indications in Emergency Practice

Forearm nerve blocks provide excellent anesthesia of the hand. Based on the sensory innervation described above, forearm nerve blocks are useful in cases of fractures, lacerations, or deep space infections of the hand. Unfortunately, the forearm nerve blocks described in this article do not provide anesthesia to the distal forearm or wrist and should not be performed for injuries affecting these areas.

Patient Selection

Appropriate ED patient selection for regional anesthesia procedures is important. The following is a brief list of exclusion criteria for this type of procedure:

• Patient unable to give consent (altered mental status, language barrier, seems unable to return to the ED if a complication from the nerve block occurred).
• Pre-existing nerve injury, numbness, tingling or weakness in the affected extremity.
• Injuries requiring urgent consultation or serial neurological examinations during admission (we recommend the ED provider communicate with the consultant before all blocks, since the sensory – and in some cases motor – exam will be altered).

Procedure

Position the patient with the affected extremity held palm-up and resting comfortably on a table or other hard surface. Place the ultrasound machine in line with the practitioner’s line of sight such that the practitioner has an unobstructed view of the ultrasound screen.