*4.1.2 Propagation and mechanisms of action*

Dam et al. [25] documented that the block at the level of the iliac crest (L4) is spread in a thoracic paravertebral manner up to T9 and T10, as well as the approach at the level of L3 extended toward the thoracic paravertebral space.

## **4.2 Technique**

The nomenclature for defining quadratus lumborum block is based on the anatomical location of the needle tip in relation to the quadratus lumborum muscle. Thus, we have a) lateral, b) posterior, and c) anterior quadratus lumborum. All blocks must be carried out under standard security and aseptic measures [23, 26]. Patient position can be prone, lateral, or sitting depending on patient and physician preferences.

Vision through ultrasound must be direct and with hydrodissection using a curvilinear low-frequency probe since it is a deeper block. The typical length of the needle used is 80–150 mm.

The most commonly used local anesthetics are 0.2–0.5% ropivacaine or 0.1–0.25% bupivacaine. The typical volume used varies from 0.2 to 0.5 mL/kg on each side.

#### *4.2.1 Lateral or posterior quadratus lumborum block*

The needle is placed lateral to the ultrasound probe in the anterior part in a posterior direction, and it crosses the external oblique (EO), internal oblique (LE), and transverse abdominal (TA) muscle. The final position of the needle is lateral to the quadratus lumborum (QL) (**Figures 7** and **8**) [23, 26].

#### **Figure 7.**

*Lateral or posterior quadratus lumborum blocks. Transverse transducer and anteroposterior needle trajectory are shown. The external image and ultrasound images show the ultrasound probe position with a solid arrow indicating the needle trajectory for a lateral quadratus lumborum block and the dashed line indicating the needle trajectory for a posterior quadratus lumborum block approach. The red-/blue-shaded area represents the spread of the local anesthetic.*

**Figure 8.** *Quadratus lumborum block: A technical review.*

*Ultrasound-Guided Regional Analgesia for Post-Cesarean Pain DOI: http://dx.doi.org/10.5772/intechopen.101465*
