Dr. Gray, and before him Dr. Marhofer et al. , described essentially two spatial relations of the nerve stimulator needle to the ultrasound beam for ultrasound-guided nerve blocks1,2:

  1. Perpendicular to the ultrasound plane (SAX OOP and LAX OOP)

  2. Parallel to the ultrasound plane (SAX IP and LAX IP)

    Although both approaches keep the needle orthogonal to the ultrasound beam, we and others use a third orientation, especially for ultrasound-guided supraclavicular blocks:

  3. In line with the ultrasound beam (SAX UB and LAX UB)

We advance the needle perpendicular to the skin in the direction of and in line with the ultrasound beam, i.e. , at right angle to both above approaches. In real time, we can see the needle penetrate the various tissue planes like a drill. We accept the critique that we may not continuously visualize the needle tip, but from the markings on the needle, we know its depth at all times. Because the depth of the target structure is also exactly shown on ultrasound, we can be sure not to reach structures beyond it. When it comes to supraclavicular nerve blocks, for example, we are therefore sure not to puncture the pleura, because the nerve bundle of the brachial plexus runs lateral and superficial to artery and pleura, both being visualized.

In particular, because we are going to use three-dimensional ultrasound for needle guidance in the future also in regional anesthesia, we should discuss and use the third dimension.

University of Medicine and Dentistry of New Jersey, Newark, New Jersey. michael@andreae.org

Gray AT,: Ultrasound-guided regional anesthesia: Current state of the art. Anesthesiology 2006; 104:368–73
Marhofer P, Greher M, Kapral S: Ultrasound guidance in regional anaesthesia. Br J Anaesth 2005; 94:7–17