Background

Protamine has a more difficult side-effect profile. Circulatory collapse has been reported as a result of acute pulmonary artery spasm caused by complement cascade activation by large heparin–protamine complexes.

Case presentation

A 79-year-old male underwent endovascular aneurysm repair 11 years ago for a ruptured abdominal aortic aneurysm. A saccular aneurysm (maximum diameter: 57 mm) appeared at the proximal end of the stent graft. Thoracoabdominal aortic replacement was performed under partial cardiopulmonary bypass. The cardiopulmonary bypass was removed, and 15 min after protamine initiation, circulatory collapse emerged with pulmonary hypertension. Extracorporeal membrane oxygenation was then initiated. Unfortunately, the patient developed coagulopathy, followed by severe pulmonary hemorrhage occurred, leading to death.

Conclusion

Pulmonary artery spasm should always be considered as a differential diagnosis for hypotension after protamine administration, and prompt intervention is crucial.