Successful use of extracorporeal membrane oxygenation in a patient with catastrophic air embolism: A case report

INTRODUCTION

The computed tomography (CT)-guided cryotherapy was indicated for patients unsuitable for surgery (including those with poor pulmonary function, advanced age, or comorbidities (for example, cardiac conditions) that make them high-risk surgical candidates) and small, localized lesions, particularly effective for small peripheral non-small cell lung cancers or ground-glass opacities suspected of being early adenocarcinomas.^[1,2] According to a national study from Japan mainly for CT-guided biopsy, pneumothorax was the most common complication and occurred for 35% of cases. Moreover, other complications include air embolism (0.061%), tumor seeding (0.061%), tension pneumothorax (0.10%), severe pulmonary hemorrhage or hemoptysis (0.061%), hemothorax (0.092%), and others, including heart arrest, shock, and respiratory arrest (0.26%).^[3] Iatrogenic vascular air embolism is rare but is associated with significant morbidity and mortality during a chest surgery. Due to the air embolism being mostly asymptomatic and usually undiagnosed and unreported, the real incidence may be greater and should be kept in mind when undergoing invasive procedures.^[4] The incidence has been reported from 0.02% to 0.4%.^[5-7] The actual rate is estimated to be approximately 3.8%, including some cases presenting asymptomatic and not diagnosed.^[8] If the systemic air embolism happened, the mortality rate was about 26%.^[9] Due to its high morbidity and mortality, the operator should keep this complication in mind and activate immediate rescue if possible. We report a case of a massive air embolism occurring during CT-guided cryotherapy under general anesthesia.

CASE REPORT

A 58-year-old non-smoking woman was found to have a 1.1 cm ground-glass nodule (GGN) at the anterior right lower lobe (RLL), two small 0.5–0.55 cm GGN at the anterior and medial right upper lobe (RUL), and two small GGN < 0.5 cm at the left upper lung (LUL) and left lower lobe (LLL) in 2020. The patient underwent thoracoscopic wedge resection of the right RUL and RLL, followed by extended lymph node dissection. Postoperative histology confirmed adenocarcinoma in situ and minimally invasive adenocarcinoma, with clear surgical margins. The patient was regularly followed up for other two small GGN with subsequent imaging studies in 4 years.

In 2024, routine follow-up CT revealed two GGO nodules in the LUL and LLL without change. In her worry, the patient opted for cryotherapy. A CT-guided cryotherapy procedure was performed in a hybrid operating room. The patient was positioned in the right lateral decubitus position under general anesthesia. Airway management was secured with an endotracheal tube, and bilateral lung ventilation was maintained. The procedure involved percutaneous insertion of a cryotherapy needle under CT guidance. Two 17 French gauge needles with a diameter of 1.47 mm were utilized for the ablation. Imaging guidance ensured accurate targeting of the pulmonary lesions before cryoablation. However, after the needles were placed in target for 3 minutes, the patient developed bradycardia and soon became pulseless with ventricular tachycardia (VT). The needles were removed immediately and cardiopulmonary resuscitation (CPR) was initiated in the supine position. After 2 times defibrillation shocks at 200 joules, the patient successfully restored spontaneous circulation. Reviewing her CT images, air-fluid levels were unexpectedly detected within the left ventricle, descending aorta, and intercostal artery [Figures 1 and 2].

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Figure 1:

A 58-year-old female presenting with left 2 ground-glass nodules for 4 years undergoing real-time computed tomography-guided cryotherapy. After two 17 French gauge needles were inserted for 3 min, the patient developed pulseless ventricular tachycardia and the air-fluid level was unexpectedly detected within the left ventricle (red arrow).

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Figure 2:

A 58-year-old female presenting with left 2 ground-glass nodules for 4 years undergoing real-time computed tomography-guided cryotherapy. After two 17 French gauge needles were inserted for 3 min, the patient developed pulseless ventricular tachycardia and the air-fluid levels were unexpectedly detected within the left ventricle (red arrow), descending aorta (blue arrow), and intercostal artery (green arrow).

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Trendelenburg positioning and 100% oxygen were implemented immediately. Given the significant hemodynamic instability and the presence of air embolism within the arterial system, the cardiovascular surgery team was consulted, and veno-arterial extracorporeal membrane oxygenation (ECMO) was urgently initiated in 1 h. ECMO cannulation was performed through the right common femoral artery and right common femoral vein, and distal perfusion was established through the right superficial femoral artery.

Upon Surgical Intensive Care Unit admission, the patient’s vital signs were relatively stable, with a pulse rate of 66 beats/min and blood pressure of 102/59 mmHg. The laboratory data revealed elevated troponin-I and the echocardiography indicated left ventricle global hypokinesis and akinesis of the anteroapical wall with ejection fraction 18%. The patient experienced 3 episodes of seizure on the 1^st day.

We prescribed anticonvulsants immediately. Over the next 2 days, the patient’s condition progressively improved, and her consciousness returned to baseline. Hemodynamic stability was achieved, and the ECMO was successfully weaned off and removed on postoperative day 5. The patient was extubated on post-operative day 7, after confirming adequate respiratory function. Neurological examinations did not have remarkable findings. Given her stable condition, the patient was discharged. At discharge, there were no residual neurological or cardiopulmonary deficits. The following echocardiography after discharge 1 month indicated preserved wall motion of left ventricle and right ventricle with ejection fraction returned to 60%. The patient was advised to follow up in the outpatient department for further evaluation and continued surveillance of her pulmonary nodules.

DISCUSSION

Air embolism is a rare but potentially fatal complication during pulmonary interventions, including cryotherapy and CT-guided procedures. Some case reports revealed that air embolism in the left atrium, ventricle, or even descending aorta may be sometimes asymptomatic.^[10,11] However, in our case, the air embolism over the left ventricle, descending aorta, and intercostal artery caused the fatal pulseless VT and required immediate CPR and defibrillation. The severity of the symptoms depends on the volume and rate of air introduced into the vascular system,^[4,12,13] the location where the air embolism occurs and where the air migrates to,^[4] gas type,^[13] patient position,^[12,14,15] patient respiratory status,^[11,16-19] inflammatory response,^[4,20] and so on. According to the previous research, the fatal volume of venous air embolism is estimated between 200 and 300 mL or 3–5 mL/kg entrained at a rate of 100 mL/s in humans.^[13,18] The clinical manifestations differ based on the anatomical location of the embolus and whether it involves the right or left side of the circulatory system, including respiratory distress (dyspnea, wheezing, and tachypnea), cardiovascular compromise (chest pain, hypotension, mill wheel murmur), neurological deficits (altered mental status, dizziness, focal deficits), and peripheral signs (superficial crepitus, livedo reticularis).^[21]

Due to the unpredictable and this rare complication, the risk factors had been listed in several report, for example, lesion at lower lobe,^[14,22] the lesion location above the level of the left atrium,^[11,14,23] prone position,^[20,23] head-up position,^[4] intubation anesthesia,^[23] patient’s condition (for example, coughing or straining,^[23] under positive pressure ventilation,^{[16,20,23,24]} etc.) subsolid lesions,^[14,25] and the presence of pneumothorax or hemorrhage.^[14,23] The pressure between the pulmonary and the vascular system, the inflammation status, and the types of anesthesia seem to be significant factors contributing to air embolism. Back to our patient, the risk factors are the lesion above the level of the left atrium, lower lung lobe, intubation anesthesia, and positive end-expiratory pressure ventilation.

Various mechanisms have been discussed in several papers. Most air emboli are iatrogenic, which occur during medical or surgical procedures.^[18] The fundamental mechanism for air to enter the vascular system requires two conditions: A direct channel between the air source and a blood vessel and a sufficient pressure gradient that allows air to pass through the vessel wall into the lumen.^[13,21] The source of air embolism can be distinguished into the arterial system and the venous system.^[18]

Arterial air embolism typically results from gas entering the pulmonary veins or directly entering the systemic arterial circulation. Even a small amount of air in the arterial circulation can have devastating outcomes.^[18] As for the specific mechanism, there are 4 main pathways of air entry: (1) Direct passage from pulmonary arteries to pulmonary veins, (2) unintentional creation of bronchopulmonary venous fistula by operator, (3) unintentional creation of alveolo-pulmonary venous fistula by operator, (4) direct passage of air through needle when operator does not close the needle.^[4,18,23] In our case, because the ends of the needle for cryotherapy were both closed, the bronchopulmonary venous fistula seemed to be the reasonable pathway for air entry. With the intubation anesthesia and positive end-expiratory pressure ventilation, the air was largely introduced into the arterial system. Air in the systemic circulation consequently induces ischemic changes due to obstruction of the blood flow, vasospasm, as well as thrombi formation.^[17] In our case, the air over the arterial system involved the left ventricle, descending aorta, and intercostal artery. The elevated cardiac enzyme and the left ventricle global hypokinesis, akinesis with reduced ejection fraction indicated the suspected obstruction of coronary artery and the injury of myocardium. The substantial accumulation of air within the left cardiac chambers may account for the sudden compromise in myocardial pump function.

In our case, the air embolism led to VT and required immediate CPR and defibrillation. The use of veno-arterial ECMO was crucial in stabilizing the patient and allowing for the safe removal of the embolus, as well as maintaining systemic perfusion during the critical period. The traditional treatment included supplying 100% oxygen, steroid administration, drugs to reduce platelet adhesion, anticonvulsant therapy, and mechanical interventions, such as placing the patient in the Trendelenburg and left lateral decubitus positions.^{[17,18,24,26]}

Given that gas bubbles lack sufficient buoyancy to oppose arterial blood flow, these interventions are more appropriately applied in the management of venous and right ventricular air embolisms.^[10] As for the arterial system, hyperbaric oxygen therapy (HBO) is widely recognized as the definitive treatment for arterial air embolism.^[4,12,18,21] The early HBO (within the first 4–6 h, and best within 3 h) has considered to be the highest likelihood of success and may improve prognosis.^[24] Although early HBO offers the greatest chance of success, its use remains indicated even if considerable time has elapsed since the initial incident.^[18] However, due to the patient’s unstable hemodynamic status and conscious change status on postoperative day 3, it was hard to facilitate HBO therapy. Thus, the immediate use of veno-arterial ECMO was initiated after the diagnosis of massive air embolism in the arterial system. ECMO has been implemented as a rescue therapy to provide cardiopulmonary support and adequate gas exchange or perfusion in patients with persistent cardiovascular collapse unresponsive to CPR, particularly when basic therapy is unavailable.^[25,27] The study by Ahn et al.^[25] demonstrated that pulmonary vein injury during CT-guided transthoracic needle biopsy is a significant risk factor for air embolism, with ECMO effectively used in severe cases, leading to survival without neurological sequelae. The case report by Kuo et al.^[28] described a 59-year-old woman who developed venous air embolism during pars plana vitrectomy, resulting in acute hypoxemic respiratory failure. Veno-venous ECMO was initiated promptly, stabilizing her hemodynamic condition, and she recovered without neurological deficits. The evidence supporting its value is limited to small case series, and its role is not well established. Stegmann et al.^[29] demonstrated that injecting 0.02 mL/kg of air into the LAD coronary artery in 74 mongrel dogs resulted in a 28% mortality rate (12/43) without extracorporeal circulation (ECC), while 0% mortality was observed with ECC. The ECC significantly reduced myocardial damage, shortened rewarming time (5.4 min vs. 8.7 min), and improved survival outcomes. The animal experiment demonstrated a better prognosis with the ECMO intervention. Some advanced intervention includes aspiration,^[12,13,21] single lung ventilation,^[10,26] and so on, which are all limited to small case reports.

CONCLUSION

This case demonstrates the effective management of a severe intraoperative complication using advanced resuscitative techniques, including ECMO. The patient’s recovery without neurological sequelae further emphasizes the importance of timely intervention and multidisciplinary collaboration in managing complex intraoperative events. Continued follow-up is necessary to monitor the long-term outcomes of the patient’s pulmonary condition and neurological outcome.