PRESENTER: Thank you for the opportunity to discuss our technique of intercostal nerve cryotherapy during the Nuss procedure for pectus excavatum. Sensory and motor innervation of the chest wall is provided by the intercostal nerves. These nerves classically reside in the costal groove on the inferior border of the rib. The nerve courses between the innermost intercostal muscle and the internal intercostal muscle.

The majority of the sensation of the chest wall occurs via the lateral cutaneous branch and the anterior cutaneous branch of the intercostal nerve. The lateral cutaneous branch divides into the anterior and posterior branches that innervate the lateral chest wall. The anterior branch is the terminal branch of the intercostal nerve in the anterior chest.

To effectively manage postoperative pain after the Nuss procedure, both nerves should be treated by positioning the cryotherapy probe posterior to the takeoff of the lateral cutaneous branch. As depicted in the drawing, the lateral cutaneous nerve branches between the innermost and internal intercostal muscles. Thus, we aim to position the cryotherapy probe at the origin of the innermost intercostal muscle. It is important to position the probe at least 4 centimeters from the thoracic ganglia so as not to damage the structure.

Once the bilateral incisions for the thoracic strut placement have been made, we perform thoracoscopy. A second port is placed low in the chest, under thoracoscopic guidance, to provide visualization during the cryotherapy procedure. The cryotherapy probe is passed directly through the chest wall. The probe is then used to count the appropriate ribs and improve exposure within the thoracic cavity.

The mesh portion of the probe is not insulated. And frostbite of the skin can occur. Thus, the probe should be wrapped with gauze and the skin retracted for protection from freezing.

The innermost intercostal muscle is easily visualized and acts as an excellent landmark for freezing. The manufacturer recommends treating the level of the thoracic strut with two levels above and two levels below. In our practice, we routinely treat levels thoracic rib three through thoracic rib seven bilaterally, regardless of the bar position.

Once the third rib is identified, the probe is pushed with a bit of force under the costal groove at the posterior margin of the innermost intercostal muscle. The free cycle is then initiated. Each level is treated at minus 40 to minus 80 degrees Celsius for between 60 and 120 seconds, depending on the patient's size and surgeon preference.

The probe should not be moved until thawed, as permanent injury to the nerve may result. And pneumothorax can result from touching the lung while the probe is freezing. We routinely use a double-lumen endotracheal tube and intrathoracic gas insufflation to manage the lung. Additional instruments for retraction or tilting the patient to cause the lung to fall away from the probe can be used in difficult cases.

We then perform intercostal nerve blocks with either 0.25% bupivacaine with epinephrine or liposomal bupivacaine per surgeon choice. During our initial experience, we perform the blocks through the chest wall. Now we use a long laparoscopic aspiration needle that allows us to accurately inject the medication under thoracoscopic guidance.

While the cryotherapy procedure has increased the operative time, we have seen a marked reduction in postoperative length of stay and narcotic use. Nearly 50% of our patients do not use narcotics once leaving the PACU without increased pain scores. Sensation returns to normal around two to three months postoperatively.

Important points of the cryotherapy procedure include avoid touching the lung with a cold probe to prevent a pneumothorax. We accomplish this with a double-lumen endotracheal tube, gas insufflation of the chest, patient positioning, and rarely, add an extra retracting instrument.

One should position the probe at least 4 centimeters from the thoracic ganglia. Do not freeze above rib three, to avoid a Horner's syndrome. And do not freeze below rib eight, to avoid abdominal wall weakness. And while the position of the intercostal neurovascular bundle can vary in the intercostal space, we always position the probe at the costal ridge.

We routinely treat levels three to seven bilaterally with good results. This strategy has also worked well with double bar placements. Other centers have tailored the treatment levels to the bar position.

We are more commonly treating for 60 seconds as compared to 120 seconds. The treatment time depends on patient size, with patients larger than 60 kilograms being treated for 120 seconds. The probe temp should not be colder than minus 80 degrees Celsius, to reduce the risk of permanent damage to the nerve.

Additionally, the probe should not be moved during the freeze cycle, to prevent damage to the nerve. While the treatment effect is immediate, it may take 12 to 24 hours for the patient to be fully numb. Thus, we routinely perform intercostal nerve blocks with a laparoscopic needle aspirator, which has improved the accuracy of our injections.

We are keeping a registry of all patients treated with cryotherapy to assess for chronic postsurgical pain. While this complication is reported after cryotherapy in adults, current literature suggests it is very rare in adolescents. Thank you for your attention and the opportunity to present this technique. Please reach out to Dr. Wilder or Dr. Potter with questions or comments.