An unusual cause of refractory hypoxaemia after hiatus hernia surgery: a case report of platypnoea-orthodeoxia syndrome.

Abstract

Background: Platypnoea-orthodeoxia syndrome (POS) is a clinical manifestation that arises from an underlying pathological process, most commonly a right-to-left intracardiac shunt such as a patent foramen ovale (PFO). The precise incidence of platypnoea-orthodeoxia syndrome remains undefined; nevertheless, it is widely regarded as an exceedingly rare clinical entity, particularly within the postoperative context. Its occurrence following upper gastrointestinal surgery is even more uncommon, with only a few cases scarcely reported in the literature. We describe an unusual case of POS following laparoscopic repair of a large type IV hiatus hernia with gastric volvulus reduction, highlighting the role of thoracoabdominal anatomical shifts in precipitating this syndrome.

Case presentation: A 74-year-old man with a history of obstructive sleep apnoea and a longstanding giant type IV hiatus hernia underwent laparoscopic gastric volvulus reduction, hernia repair, and gastropexy. Postoperatively, he developed profound hypoxaemia, initially attributed to atelectasis. However, during intensive care unit admission, his SpO₂ was observed to drop dramatically in the upright position and improve in the supine position. Arterial blood gas analysis confirmed positional hypoxaemia consistent with POS. Transthoracic echocardiography with bubble contrast demonstrated a previously silent patent foramen ovale exhibiting significant right-to-left shunting, accompanied by marked left atrial dilatation, while right atrial and ventricular pressures remained within normal limits. Additionally, a CT pulmonary angiogram demonstrated a small pulmonary embolism in the right upper lobe with associated bilateral atelectasis. After initial stabilisation with anticoagulation and physiotherapy, the patient was discharged with outpatient plans for a transcatheter PFO closure. Three months later, he re-presented with hypoxaemic respiratory failure and cyanosis. Repeat imaging demonstrated marked worsening of the right-to-left shunt, necessitating urgent transcatheter PFO closure, which was successfully performed. The patient made a full recovery and was discharged on room air.

Conclusions: This case illustrates the potential for thoracoabdominal surgeries, such as hiatus hernia repairs with extensive mediastinal dissection, to unmask intracardiac shunts by altering venous return and cardiac geometry. It underscores the importance of considering POS in patients with unexplained postoperative or positional hypoxaemia. Early orthostatic oximetry and targeted imaging are critical for timely identification of the syndrome. A high index of suspicion for this rare but treatable condition is crucial, as prompt recognition and timely intervention have the potential to prevent diagnostic delays, reduce morbidity, and markedly improve perioperative outcomes in patients with otherwise unexplained refractory hypoxaemia.