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Background and Aims Since its introduction, intercostal cryoanalgesia in NUSS surgery for pectus excavatum repair has gained popularity for its benefits in long-term pain control, shorter hospital stays, and reduced opioid use in pediatric patients. However, potential risks for pediatric patients require further attention. This study aims to shed light on a significant but underreported complication: massive pleural effusion secondary to intercostal cryoablation.

Methods Our case involves a 13-year-old patient who underwent percutaneous cryotherapy on the intercostal spaces from T7 to L3 bilaterally, 72 hours before surgery. This involved two cycles of freezing at -70°C for 2 minutes, with a 30-second thawing period for each space. The patient then underwent surgery with an additional spinal erector block. The postoperative course was smooth, and after 7 days he was discharged.

Results Three weeks after, the patient returned to the hospital with a mild fever and shortness of breath. Examination revealed a right-sided pleural effusion of 11 cm with atelectasis in the middle and lower lobes. Thoracoscopy and drainage were performed, leading to recovery and discharge 10 days later. Biochemical analysis indicated an inflammatory exudate.

Conclusions Although direct-vision cryoanalgesia has a documented 50% rate of pleural effusions/pneumothorax, there is less information on the percutaneous approach. This method, regardless of the mode of application, appears to cause soft tissue injury near the probe, potentially leading to fluid accumulation and symptomatic effusions. To reduce risks, cryoanalgesia protocols should be optimized, ensuring proper freezing and thawing times, considering one-lung ventilation, employing direct-vision techniques when possible, and maintaining careful follow-up by anesthesiologists.