Ensuring safe journey of QL catheter: Problem rectified!

To the Editor,

Course of a catheter placed in quadratus lumborum plane (QLP) after an ultrasound (US)-guided transmuscular quadratus lumborum block (TMQLB) is not always predictable.[1] The catheters either gets coiled or penetrates the anterior thoracolumbar fascia (ATLF). The ATLF is a very tight fascia and offers a very high resistance. Moreover, the compliance of QLP space is low. We noticed that the catheter buckles, coils, or penetrates with the bevel perpendicular to the ATLF. To overcome this situation, we conducted a pilot study in five American Society of Anesthesiologists-physical status (ASA-PS) I--II undergoing open nephrolithotomy.

Standard general anesthesia was administered in all five patients: 0.03 mg midazolam, 1.5 μg fentanyl, and 2--2.5 mg propofol, intravenously (IV). Tracheal intubation was done after achieving neuromuscular blockade with 1 mg/kg atracurium IV. In the lateral position with Shamrock technique, the quadratus lumborum (QLM), Psoas Major (PMm), and erector spinae (ESM) muscles were identified. Under strict asepsis (chlorhexidine solution and sterile draping), an 18 G Tuohy needle was inserted under US guidance using a curvilinear probe with an in plane approach. The bevel of the needle was kept upward and perpendicular to the QLM fibers [Figure 1a]. The bevel was then rotated to 90° from its initial position with the bevel facing cephalad and parallel to the QLM fibers [Figure 1b]. After identification of tip of epidural needle in the ATLF, the space was injected with 10 ml 0.375% ropivacaine after negative aspiration. The catheter was inserted with bevel parallel to the QLM fibers. We observed that the catheter insertion was smooth without resistance, without any evidence of coiling on USG [Figure 1c]. Another 10 ml 0.375% ropivacaine was injected through the catheter and was visualized in ATLF.

Figure 1

(a) Figure shows conventional method were bevel of Tuohy needle is facing upwards. (b) Figure shows rotation of needle by 90° due to which bevel is now facing upward. (c) Figure shows showing presence of catheter in quadratus lumborum plane after an US-guided transmuscular quadratus lumborum plane block. The catheter is parallel to quadratus lumborum muscle fibers without any twists or coil

Studies have shown that ideal location of the tip of the catheter is observed in only 40% patients. Ease of insertion and length of catheter inserted does not predict final position of the catheter.[2] Coiling, knotting of catheters are frequent problem dependant on the length of insertion of catheters.[3] Whether the coil anchors the catheter or is a predisposition to knotting is debatable. The suggested length of the catheter in the perineural sheath is 3--5 cm.[4] The placement and final destination of the catheter depends on the tightness of the sheath around the nerve or the plexus. The compliance of the femoral or interscalene sheath would be different from a fascia iliaca sheath. The compliance can differ from one fascial compartment to the other. QLP is a tight compartment with low compliance offering increased resistance as opposed to fascia iliaca compartment (FIC).

Regardless of the needle tip position on US, if the bevel facing is cephalad the catheter in high compliant FIC will take its own course. This would not be probably the same situation in low compliant high resistance QLP. The most time-consuming procedure is to determine the tip of catheter and locate the spread of local anesthetic (LA) in the compartment. US-guided non-stylleted catheters placed parallel to the nerve tend to coil, deviate, and loop after 7 cm insertion.[5]

In our series, we choose to rotate the bevel of the Tuohy needle parallel to the long axis of the QLM fibers. The catheter was positioned under the ATLF in all five cases, observed intraoperatively. The spread of the LA was also traced in the longitudinal axis, with the probe placed parallel to QLM fibers. In this axis, the catheter could be traced with the LA spilling out of it.

To conclude, we suggest that during catheter placements after TMQLB, the bevel should be rotated through 90°. This is for appropriate positioning of the needle, identifying the catheter, correct spread of the LA after a bolus and continuous infusion.

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Conflicts of interest

There are no conflicts of interest.