Overview

It is no coincidence that the resurgence in regional anesthesia parallels the incorporation of ultrasound into these procedures.  For any regional procedure to be successful, several things must occur; (1) accurate identification of the nerves to be blocked, (2) appropriate placement of the needle near the identified nerve, (3) and proper distribution of local anesthetic around the nerve.  Traditional methods reliant on landmark techniques, nerve stimulation, and paresthesia cannot meet all three of these requirements, however ultrasound can.  In recent years, numerous studies have been published demonstrating the efficacy of ultrasound-guided regional anesthesia (UGRA) over methods currently deemed the gold standard.  A meta-analysis of randomized controlled trials conducted by Abrahams et al. showed that the data from ultrasound groups consistently showed higher success rates, shorter procedure and onset times, and longer block duration when compared to traditional methods.  In a review of nineteen studies, McCartney et al suggested that ultrasound provides significant benefits for patients undergoing brachial plexus blocks when comparing UGRA to other nerve location methods.  Despite the mounting level of evidence supporting UGRA, ultrasound itself is not a guarantee of increased block success.  The major limitation of US is that it is user dependent, with varying levels skill and success from provider to provider.  While many authors have proposed training recommendations to improve US skills, no formal training standards currently exist, and the level of expertise varies from practice to practice.  For the anesthetist new to UGRA, it is desirable to pick a specific block and master the technique, rather than performing a wide array of blocks that vary in difficulty.  The femoral block is a good place to start because it is relatively superficial and provides the practitioner with good anatomical landmarks that are readily identifiable.

A solid foundation in anatomy is a prerequisite for performing any regional anesthetic.  This cannot be overstated.  While US allows us to “look” beneath the skin and see anatomical structures in real-time, images are not always as definitive as those seen in reference materials, often lulling the practitioner into a false sense of security.  Depending on the size and location of a root, trunk, division, cord, or branch, they may appear as tendons or small arteries, leading to incomplete blocks or complications such as inadvertent vascular punctures and intra-neural injections.  Additionally, the use of US does not preclude the provider from adhering to the established guidelines set forth in current regional anesthesia practice.  This includes verifying the right patient and procedure, placing the patient on oxygen and standard monitoring prior to sedation, properly prepping and draping the patient, confirming proper needle placement, and aspirating prior to each incremental injection of local anesthetic.   As with any anesthetic procedure, each patient will present with a slight variation of the “standard” image.  Only performing numerous studies on a regular basis will lead to greater proficiency.

The choice of UGRA is determined by numerous factors such as patient comorbidities, suitability of the technique for the proposed surgery, provider comfort in performing the block, as well the mental status of the patient.  UGRA has many indications, these include:

  • Primary anesthetic
  • Pain Management
  • History of severe PONV or risk of MH
  • Patient is too ill for general anesthesia
  • Physician preference

There are some instances where under no circumstances should regional anesthesia be considered.  These are known as absolute contraindications.

  • Patient refusal
  • Local infection at the site of the proposed block
  • Active bleeding an anticoagulated patient
  • Proven allergy to a local anesthetic

Most contraindications to regional anesthesia are relative.  The provider must determine the risk vs. benefit prior to proposing any procedure.  Below are situations to consider:

  • Respiratory compromise
  • Inability to cooperate/understand procedure
  • An anesthetized patient (adult population)
  • Bleeding diathesis secondary to an anticoagulant or genetic defect
  • Bloodstream infection
  • Preexisting peripheral neuropathy

References

Abrahams MS, Aziz MF, Fu RF, Horn JL. Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Br J Anesth. 2009; 102: 408-417.

McCartney C J, Lin L, Shastri, U. Evidence basis for the use of ultrasound for upper-extremity blocks. Reg Anesth Pain Med. 2010; 35(Suppl 2): S10-5.

Feller-Kopman D. Ultrasound-guided internal jugular access: A proposed standardized approach and implications for training and practice. Chest. 2007; 132(1), 302-309.

Emergency ultrasound guidelines. Approved by the ACEP board of directors, June 1, 2001.  Available at http://acep.org/NR/rdonlyres/8024079E-28E8-4875-93E6-6867EA705A2A/0/ultrasound_guidelines.pdf.  Accessed December 22, 2008.

Sites BD, Chan VW, Neal J. et al. The american society of regional anesthesia and pain medicine and the european society of regional anesthesia and pain therapy joint committee recommendations for education and training in ultrasound-guided regional anesthesia. Reg Anesth Pain Med. 2009; 34: 40-46.

Griffin J, Nicholls B. Ultrasound in regional anaesthesia. Anaesthesia. 2010; 65 (Suppl 1): S1-12.

Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology. 4th ed. New York, NY: Lang Medical Books/McGraw-Hill; 2006: 325-328.

 

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