Intercostal Nerve Block with Ultrasound

Abstract

The intercostal nerves provide sensory and motor innervation for much of the back, trunk, and abdominal wall. Each intercostal nerve travels within a neurovascular bundle made up of an intercostal nerve, artery, and vein. This bundle runs along the costal groove at the inferior edge of its accompanying rib. The intercostal nerve lies inferior to both vessels within the neurovascular bundle. The proximity of the nerve to the vessels accounts for the high uptake of local anesthetic into the blood.

Each intercostal nerve originates from the spinal nerve root at the vertebral level of the rib it travels with. Spinal nerves divide into dorsal and ventral branches, with the ventral branches continuing anterolaterally to become the intercostal nerves. The intercostal nerve briefly travels between the parietal pleura and innermost intercostal muscle before continuing anterolaterally between the internal and innermost intercostal muscles. As the intercostal nerve travels towards the midaxillary line the lateral cutaneous branch splits off—traversing the internal and external intercostal muscles and dividing into an anterior and posterior branch which supply the lateral trunk. As the intercostal nerve travels anteriorly it forms another branch called the anterior cutaneous branch that divides into the medial and lateral branches which supply the anterior trunk and abdomen.

Intercostal nerve blocks are indicated as primary or adjunct pain management intervention for patients with rib fractures or chest wall and upper abdominal pain. Indications include thoracic surgery incisional pain, post-thoracotomy pain, herpes zoster or post herpetic neuralgia, postmastectomy pain, and cholecystectomy. Contraindications are patient refusal, active infection over the injection site, and occasionally coagulation disorders.

Complications arise due to the proximity of the intercostal nerves to the lung and intercostal vasculature. These include pneumothorax, hemothorax, local anesthetic systemic toxicity, and even risk of spinal blockade (Chaudhri et al., Ann Thorac Surg 88(1):283–284, 2009; Shanti et al., J Trauma 51(3):536–539, 2001).

Intercostal nerve blocks can be performed with a landmark technique or under ultrasound or fluoroscopic guidance. Though efficacy and complication rates are similar between ultrasound and fluoroscopic guidance, ultrasound carries the advantage of better visualization of vascular structures, real time visualization of the pleura, and avoids the need for contrast or radiation exposure (Elkhashab and Wang, Curr Pain Headache Rep 25(10):67, 2021).