Ultrasound for Regional Anesthesia

Ultrasound for Regional Anesthesia Ultrasound for Regional Anesthesia
Regional Anesthesia > Introduction
General Comments
The use of ultrasound for regional anesthesia is relatively new, however interest in this application is growing rapidly. Ultrasound guided nerve blocks were first described as early as 1978, but it was not until the advent of advanced ultrasound technology in the 1990's that interest in this field grew. Published reports of ultrasound guided regional anesthesia have largely focused on brachial plexus blockade in the interscalene, supraclavicular, infraclavicular and axillary regions. Recent studies examining the efficacy of ultrasound guidance for femoral, sciatic, psoas compartment, celiac plexus and stellate ganglion blocks are promising, while ultrasound visualization of the epidural space can facilitate neuraxial blockade in children, adults and parturients.

The materials on this website describe both the techniques for single shot and continuous nerve blocks of the brachial plexus and lumbosacral plexus, as well as techniques for neuraxial blockade. Each technique is described in an easy step-by-step manner and is accompanied by a list of selected references. The goal of the materials on this website is to impart a greater understanding of ultrasound imaging for regional anesthesia to anesthesia practitioners and pain management clinicians.

Conventional peripheral nerve block techniques that are performed without visual guidance are highly dependent on surface anatomical landmarks for localization of the target nerve. It is therefore not surprising that regional anesthetic techniques are associated with a reported failure rate of up to 20% presumably because of incorrect needle and/or local anesthetic placement. Multiple trial-and-error attempts to locate the target nerve can lead to operator frustration, unwarranted patient pain, and time delay in the operating room, especially in patients with difficult anatomical landmarks.

Imaging technology such as MRI and CT scan can successfully localize neural structures. However, ultrasound is the most practical imaging tool for regional anesthesia as it is portable, relatively easy to learn, moderately priced, and does not pose any radiation risk. Ultrasound provides real time imaging guidance during a nerve block procedure.

Advantages of Ultrasound
• Reveals the nerve location and the surrounding vascular,
  muscular, bony, and visceral structures.
• Provides real-time imaging guidance during needle advancement
  allowing for purposeful needle movement and proper
  adjustments in direction and depth.
• Images the local anesthetic spread pattern during injection.
• Improves the quality of sensory block, the onset time, and the
  success rate compared to nerve stimulator techniques
  (as shown in some clinical studies).
• Reduces the number of needle attempts for nerve localization
  which may prove to reduce the risk of nerve injury.
• Differentiates extravascular injection from unintentional
  intravascular injection.
• Differentiates extraneural injection from unintentional
  intraneural injection.
Limitations of Peripheral Nerve Stimulation Techniques
• Peripheral nerve stimulation (PNS) guidance is useful only
  when a motor response is elicited.
• NS provides objective but indirect evidence of nerve location.
• Evidence of proper needle placement (i.e. motor response)
  disappears after injection of 1-2 mL of local anesthetic.
• Motor response achieved at less than 0.5 mA does not guarantee a
  successful or complete block.
• PNS does not prevent intravascular, intraneural or pleural puncture.
Ultrasound for Regional Anesthesia