Hoarseness of Voice and Discomfort in the Throat Observed After Quadratus Lumborum Block
Transmuscular quadratus lumborum block (TQLB) is a regional anesthesia technique known for providing effective visceral analgesia by blocking sympathetic fibers through the spread of local anesthetic into the thoracic paravertebral spaces. While TQLB is generally considered safer than conventional analgesic methods, there have been no prior reports of hoarseness associated with this procedure. This article presents two cases of hoarseness and throat discomfort following TQLB, explores potential mechanisms, and discusses the clinical implications of these findings.
Case 1 involved a 42-year-old man who presented with acute lower back pain and inguinal pain, rated at 7 on the numeric rating scale (NRS). TQLB was performed bilaterally at the L4 level using 20 mL of 0.375% ropivacaine with epinephrine in a 1:200,000 ratio. The procedure was conducted under real-time ultrasound guidance, employing the shamrock approach to identify the quadratus lumborum muscle, psoas muscle, and erector spinae muscle. The needle was inserted in a posterolateral to anteromedial direction, targeting the junction of the quadratus lumborum muscle, psoas muscle, and transverse process. Following the block, the patient’s back pain improved significantly, with the NRS score decreasing from 7 to 1. However, the patient developed hoarseness and reported a persistent discomfort in the throat, described as a sensation of needing to clear his throat. He did not experience dyspnea, difficulty coughing, or diaphragmatic paralysis, as confirmed by ultrasound. Additionally, there were no signs of miosis, ptosis, facial edema, or hypotension. The patient also noted an unusual “swollen feeling” in his left arm, although no sensory or motor blockade was observed. The hoarseness resolved spontaneously within 4 hours without intervention.
Case 2 involved a 40-year-old woman with acute low back pain who underwent bilateral TQLB at the L4 level using the same anesthetic mixture. Approximately 1 hour post-injection, the patient reported abnormal sensations and itching in the left T4-L2 and right T11-L1 dermatomes. Three hours after the procedure, she developed mild hoarseness and a sensation of a foreign body in her throat, similar to the symptoms described in Case 1. No diaphragmatic paralysis, miosis, or ptosis was observed. The discomfort resolved completely 2 hours after its onset, without any specific treatment.
Hoarseness following a nerve block is rare, particularly when the block is administered outside the cervical region, as it is typically associated with blockade of the recurrent laryngeal nerve. In these cases, however, hoarseness and throat discomfort occurred following TQLB performed at the lumbar level. The mechanism underlying these symptoms is likely related to the cephalad spread of the local anesthetic into the thoracic paravertebral space, which has been documented in previous studies. The deep fascia, through which the injectate spreads, has dynamic properties that facilitate the active transport of the anesthetic via a pumping mechanism driven by muscle tendons.
Two potential explanations for the observed symptoms are proposed. First, the local anesthetic may induce temporary vocal cord edema due to its spread to the thoracic paravertebral space. Second, the anesthetic may block the recurrent laryngeal nerve, leading to hoarseness. The first explanation appears more plausible, as the symptoms are consistent with temporary congestion or edema of the vocal cords. Anatomically, the blood supply to the vocal cords and laryngeal mucosa is derived from the superior laryngeal artery and the cricothyroid branch of the superior thyroid artery. These mucosal vessels are innervated by postganglionic sympathetic fibers originating from the superior cervical sympathetic ganglion, which, in turn, receives preganglionic fibers from the T1-T2 levels of the spinal cord. When the injectate from TQLB spreads to the thoracic paravertebral space, it may block the sympathetic fibers in this region, leading to vasodilation of the laryngeal vessels. This vasodilation can cause congestion and edema of the laryngeal mucosa, resulting in temporary hoarseness.
The cases presented here highlight a previously unreported complication of TQLB and underscore the importance of understanding the anatomical and physiological mechanisms underlying regional anesthesia techniques. While the symptoms were transient and resolved without intervention, they warrant further investigation to determine their prevalence and to develop strategies for prevention. Future studies should focus on the detailed anatomical pathways through which the injectate spreads and the potential for sympathetic blockade to induce laryngeal symptoms.
In conclusion, hoarseness and throat discomfort following TQLB are rare but noteworthy complications that may result from the cephalad spread of local anesthetic into the thoracic paravertebral space. The proposed mechanism involves sympathetic blockade leading to vocal cord edema, although further research is needed to confirm this hypothesis. Clinicians should be aware of this potential complication and monitor patients accordingly. Understanding the mechanisms underlying these symptoms will enhance the safety and efficacy of TQLB and other regional anesthesia techniques.
doi.org/10.1097/CM9.0000000000001352
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