Bedside ultrasound for early diagnosis and follow-up of postoperative negative pressure pulmonary oedema: case reports and literature review

Dear Editor,
Negative pressure pulmonary oedema (NPPE) is considered an uncommon postoperative complication but a highly serious condition in patients undergoing surgery under general anaes­thesia [1, 2]. Usually it occurs during the extubation or postoperative period. However, in general the outcomes are satisfactory with a total recovery within the first 24-48 hours, but there are more severe cases of NPPE that may be life-threatening [3]. In anaesthesiology and critical care, the main cause of NPPE is related directly to laryngospams during the extubation after removal of the laryngeal mask [4]. Despite the fact that the fatality rate in those presenting this pathology is unknown, an early diagnosis and adequate follow-up delineate the patient prognosis.
In the era of ultrasound, patient safety has been the main reason to develop important advances in this area; in particular, the application of this tool to critically ill patients has become a fast guide instrument for multiple procedures in the least invasive way. In our medical centre it has been decided to implement the ultrasound as a technique for tracing NPPE. Herein we report two cases of NPPE in which ultrasound was used to diagnose this condition and assess the therapeutic response during the stay in the intensive care unit (ICU). Our aim is to educate on the use of this tool in the practice of anaesthesiologists and critical care physicians when it comes to diagnosis and follow-up of patients with NPPE.

CASE 1

In a 34-year-old male patient, without any important past medical history, who was scheduled for varicocelectomy under general anaesthesia with laryngeal mask, anaesthesia was induced with remifentanil and propofol, and maintenance with isoflurane and remifentanil. Surgery lasted 45 minutes with no intraoperative anaesthetic or surgical complications. During the removal of the mask, the patient presented laryngospasm and oxygen desaturation of 61% that required management with positive pressure ventilation recovering an oxygen saturation of 98%. The patient was transferred to the URPA awake but could not sustain an oxygen saturation greater than 90% with a facial mask, so noninvasive mechanical ventilation was indicated. On arrival to the ICU an ultrasound scan was performed, showing B lines in all four quadrants (Figure 1) according to the BLUE protocol, and appropriate cardiovascular function with collapsibility of the inferior vena cava based on the FOCUS...


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