Something Is Growing Inside: An Unusual Adverse Effect of Paravertebral Block

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To the Editor:
Thoracic paravertebral blockade (TPVB) is often used in situations where a patient has unilateral thoracic pain with blockade focused at the nerve roots, and it has been effectively used for traumatic rib fractures. We present an unusual adverse effect of a unilateral thoracic paravertebral block that is easily treated but may alarm the patient and nursing staff.
A 58-year-old healthy man sustained 2 left-sided rib fractures at the 9th and 10th ribs during an altercation. Pain was treated with an ultrasound-guided TPVB, transverse in-plane approach, performed at T9–10 paravertebral space with placement of catheter that was bolused and basally infused with 0.25% bupivacaine. The patient had instantaneous pain relief.
That same night, the trauma team and anesthesiologist on call were alerted by a floor nurse who had noticed that the patient's abdomen was bulging on the left side as if “something was growing inside” (Fig. 1). On assessment, it was noted that the abdomen was protruding on the left side, which alarmed the patient, but no pain was reported. An abdominal binder was prescribed, and the patient did well for the rest of his hospitalization.
Thoracic paravertebral blockade is an established treatment modality for treatment of pain caused by rib fracture with less risk of complications than a thoracic epidural.1,2 The incidences of failure and complications for TPVB are cited to be between 6.8% and 10%, and 2.6% and 5%, respectively.3 These include hypotension (4.6%), vascular puncture (3.8%), epidural spread, inadvertent pleural puncture (1.1%), and pneumothorax (0.5%).4 Our patient experienced none of the reported complications but instead had unilateral relaxation of abdominal muscles.
To our knowledge, this unusual adverse effect related to TPVB has never been reported in the literature, although there exists 1 case report of a “flank bulge” related to a transversus abdominis block.5 The abdominal muscles are innervated by intercostal nerves 7 to 11, subcostal nerves, and iliohypogastric and ilioinguinal nerves; a TPVB at T9–10 could easily relax these muscles, leading to a “flank bulge.” While alarming to the patient and the nursing staff, it is indeed a sign that the block is working well, and it would be prudent to educate patients and staff on how this occurs to prevent unnecessary alarm.
The patient has given permission to report this case for educational purposes, including the use of the electronic media.

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