High-Frequency Jet Ventilation Versus Spontaneous Respiration for Percutaneous Cryoablation of Lung Tumors: Comparison of Adverse Events and Procedural Efficiency.

BACKGROUND. High-frequency jet ventilation (HFJV) facilitates accurate probe placement in percutaneous ablation of lung tumors but may increase risk for adverse events, including systemic air embolism. OBJECTIVE. The purpose of this study was to compare major adverse events and procedural efficiency of percutaneous lung ablation with HFJV under general anesthesia to spontaneous respiration (SR) under moderate sedation. METHODS. This retrospective study included consecutive adults who underwent CT-guided percutaneous cryoablation of one or more lung tumors with HFJV or SR between January 1, 2017, and May 31, 2023. We compared major adverse events (Common Terminology Criteria for Adverse Events grade ≥ 3) within 30 days postprocedure and hospital length of stay (HLOS) of 2 days or more using logistic regression analysis. We compared procedure time, room time, CT guidance acquisition time, CT guidance radiation dose, total radiation dose, and pneumothorax using generalized estimating equations. RESULTS. Overall, 139 patients (85 women, 54 men; median age, 68 years) with 310 lung tumors (82% metastases) underwent 208 cryoablations (HFJV, n = 129; SR, n = 79). HFJV showed greater rates than SR for the treatment of multiple tumors per session (43% vs 19%, respectively; p = .02) and tumors in a nonperipheral location (48% vs 24%, p < .001). Major adverse event rate was 8% for HFJV and 5% for SR (p = .46). No systemic air embolism occurred. HLOS was 2 days or more in 17% of sessions and did not differ significantly between HFJV and SR (p = .64), including after adjusting for probe number per session, chronic obstructive pulmonary disease, and operator experience (p = .53). Ventilation modalities showed no significant difference in procedure time, CT guidance acquisition time, CT guidance radiation dose, or total radiation dose (all p > .05). Room time was longer for HFJV than SR (median, 154 vs 127 minutes, p < .001). For HFJV, the median anesthesia time was 136 minutes. Ventilation modalities did not differ in the frequencies of pneumothorax or pneumothorax requiring chest tube placement (both p > .05). CONCLUSION. HFJV appears to be as safe as SR but had longer room times. HFJV can be used in complex cases without significantly impacting HLOS of 2 days or more, procedure time, or radiation exposure. CLINICAL IMPACT. Selection of the ventilation modality during percutaneous lung ablation should be based on patient characteristics and anticipated procedural requirements as well as operator preference.

CO2 delivery techniques in mini-sternotomy surgery and neurological events: a multicentric study.

BACKGROUND: The impact of air bubbles into the cerebral circulation after open heart surgery has been a topic of discussion since the introduction of the heart-lung machine. The aim of the study was to evaluate whether the use of a dedicated commercial sponge diffuser is better than a custom-made narrow section cannula or the absence of CO2 in preventing neurological events after aortic valve replacement via J mini-sternotomy. METHODS: Three cohorts of J-shaped mini-sternotomy performed at three different centers were prospectively compared: CO2 supplied via sponge diffuser, CO2 supplied via cannula, and no CO2 supply. Propensity matching was used to obtain comparable groups. The primary endpoints were postoperative stroke, transitory ischemic attack, convulsions, and dizziness. Secondary endpoints were 30-day mortality, duration of mechanical ventilation, and intensive care unit length of stay. RESULTS: 275 patients were enrolled in the study. After propensity matching, the sponge diffuser cohort had a significantly lower duration of mechanical ventilation (P < 0.001) and 30-day mortality (P = 0.05) when compared to the cannula cohort and the no-CO2 cohort, a lower incidence of all neurological events (P = 0.03) and dizziness (P = 0.05) when compare to the no-CO2 cohort, and a lower intensive care unit length of stay when compared to the cannula cohort (P = 0.001). CONCLUSIONS: The sponge diffuser used to deliver the CO2 into the surgical field during aortic valve replacement via J mini-sternotomy has been demonstrated to guarantee better neurological outcomes compared to a custom-made narrow section cannula or the absence of CO2.

Middle cerebral artery hypodense dot sign in iatrogenic air embolism.

Air embolism is a rare cause of stroke, usually associated with medical procedures, with gastrointestinal endoscopy rarely implicated. Here, we present a case of a patient who experienced cerebral air embolism post-gastroscopy, presenting with aphasia and right hemiparesis due to left M2 occlusion with spontaneous and complete recovery. CT scan revealed a hypodense defect in the left Sylvian fissure, representing a "hypodense dot sign" suggestive of an air embolism. The hypodense MCA sign, previously described in fat embolism cases, could also indicate air embolism, supporting prompt diagnosis and proper intervention.

Changes in lung mechanics and ventilation-perfusion match: comparison of pulmonary air- and thromboembolism in rats.

BACKGROUND: Pulmonary air embolism (AE) and thromboembolism lead to severe ventilation-perfusion defects. The spatial distribution of pulmonary perfusion dysfunctions differs substantially in the two pulmonary embolism pathologies, and the effects on respiratory mechanics, gas exchange, and ventilation-perfusion match have not been compared within a study. Therefore, we compared changes in indices reflecting airway and respiratory tissue mechanics, gas exchange, and capnography when pulmonary embolism was induced by venous injection of air as a model of gas embolism or by clamping the main pulmonary artery to mimic severe thromboembolism. METHODS: Anesthetized and mechanically ventilated rats (n = 9) were measured under baseline conditions after inducing pulmonary AE by injecting 0.1 mL air into the femoral vein and after occluding the left pulmonary artery (LPAO). Changes in mechanical parameters were assessed by forced oscillations to measure airway resistance, lung tissue damping, and elastance. The arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were determined by blood gas analyses. Gas exchange indices were also assessed by measuring end-tidal CO2 concentration (ETCO2), shape factors, and dead space parameters by volumetric capnography. RESULTS: In the presence of a uniform decrease in ETCO2 in the two embolism models, marked elevations in the bronchial tone and compromised lung tissue mechanics were noted after LPAO, whereas AE did not affect lung mechanics. Conversely, only AE deteriorated PaO2, and PaCO2, while LPAO did not affect these outcomes. Neither AE nor LPAO caused changes in the anatomical or physiological dead space, while both embolism models resulted in elevated alveolar dead space indices incorporating intrapulmonary shunting. CONCLUSIONS: Our findings indicate that severe focal hypocapnia following LPAO triggers bronchoconstriction redirecting airflow to well-perfused lung areas, thereby maintaining normal oxygenation, and the CO2 elimination ability of the lungs. However, hypocapnia in diffuse pulmonary perfusion after AE may not reach the threshold level to induce lung mechanical changes; thus, the compensatory mechanisms to match ventilation to perfusion are activated less effectively.

Air Embolism-Induced Ischemic Stroke Following Orthognathic Surgery in a Patient With Goldenhar Syndrome.

Goldenhar syndrome, a rare congenital anomaly, manifests as craniofacial malformations often necessitating intricate surgical interventions. These procedures, though crucial, can expose patients to diverse postoperative complications, including hemorrhage or infection. A noteworthy complication is stroke, potentially linked to air embolism or local surgical trauma. We highlight a case of a male patient, aged 20 years, who experienced a significant postoperative complication of an ischemic stroke, theorized to be due to an air embolism, after undergoing orthognathic procedures for Goldenhar syndrome. The patient was subjected to LeFort I maxillary osteotomy, bilateral sagittal split ramus osteotomy of the mandible, and anterior iliac crest bone grafting to the right maxilla. He suffered an acute ischemic stroke in the left thalamus post-surgery, theorized to stem from an air embolism. Advanced imaging demonstrated air pockets within the cavernous sinus, a rare and concerning finding suggestive of potential air embolism. This case underscores the intricate challenges in treating Goldenhar syndrome patients and the rare but significant risk of stroke due to air embolism or surgical trauma. Limited literature on managing air embolism complications specific to Goldenhar syndrome surgeries exists. Generally, management includes immediate recognition, positional adjustments, air aspiration via central venous catheters, hyperbaric oxygen therapy, hemodynamic support, and high-flow oxygen administration to expedite air resorption. Our patient was conservatively managed post-surgery, and at a 3-month neurology follow-up, he showed significant improvement with only residual right arm weakness. It emphasizes the imperative of a comprehensive, multidisciplinary approach.

Flow field around bubbles on formation of air embolism in small vessels.

An air embolism is induced by intravascular bubbles that block the blood flow in vessels, which causes a high risk of pulmonary hypertension and myocardial and cerebral infarction. However, it is still unclear how a moving bubble is stopped in the blood flow to form an air embolism in small vessels. In this work, microfluidic experiments, in vivo and in vitro, are performed in small vessels, where bubbles are seen to deform and stop gradually in the flow. A clot is always found to originate at the tail of a moving bubble, which is attributed to the special flow field around the bubble. As the clot grows, it breaks the lubrication film between the bubble and the channel wall; thus, the friction force is increased to stop the bubble. This study illustrates the stopping process of elongated bubbles in small vessels and brings insight into the formation of air embolism.

The safety and utility of the semi-sitting position for clipping of posterior circulation aneurysms.

BACKGROUND: The semi-sitting position offers advantages for surgeries in the posterior cranial fossa. However, data on its safety and effectiveness for clipping aneurysms in the posterior cerebral circulation are limited. This retrospective cohort study evaluates the safety and effectiveness of using the semi-sitting position for these surgeries. METHODS: We conducted a retrospective study of 17 patients with posterior cerebral circulation aneurysms who underwent surgical clipping in the semi-sitting position in the Department of Neurosurgery at Hannover Medical School over a 10-year period. RESULTS: The mean age at surgery was 62 years (range, 31 to 75). Fourteen patients were admitted with subarachnoid hemorrhage and 3 patients had incidental aneurysmas. Fifteen patients had PICA aneurysms, and two had aneurysms of the vertebral artery and the superior cerebellar artery, respectively. The median diameter of the aneurysms was 5 mm (range 3-17 mm). Intraoperative venous air embolism (VAE) occurred in 4 patients, without affecting the surgical or clinical course. VAE was associated with a mild decrease of EtCO2 levels in 3 patients and in 2 patients a decrease of blood pressure occurred which was managed effectively. Surgical procedures proceeded as planned in all instances. There were no complications secondary to VAE. Two patients died secondary to respiratory problems (not related to VAE), and one patient was lost to follow-up. Eleven of fourteen patients were partially or completely independent (Barthel index between 60 and 100) at a median follow-up duration of 13.5 months (range, 3-103 months). CONCLUSION: The semi-sitting position is a safe and effective technique for the surgical clipping of aneurysms in the posterior cerebral circulation. The incidence of VAE is comparable to that seen in tumor surgery. However, it is crucial for the surgical and anesthesiological team to be familiar with potential complications and to react immediately in case of an occurrence of VAE.

Pulmonary abscess combined with pulmonary vein thrombosis and stroke: A case report.

BACKGROUND: Although most stroke patients have underlying vascular risk factors, it is important to consider infectious causes of stroke in young adults without traditional risk factors or patients with cryptogenic stroke. Pulmonary vein thrombosis and air embolism can potentially cause cerebral infarction. However, the association between infection and pulmonary vein thrombosis or air embolism is often overlooked. In this case, we present a rare infectious cause of stroke and air embolism involving a pulmonary abscess and pulmonary vein thrombosis. CASE PRESENTATION: A 37-year-old male patient initially presented with right-sided pneumonia. During treatment at a local hospital, he developed headaches and left limb weakness. Subsequently, he was transferred to our hospital due to septic shock. Neurological evaluations revealed multiple brain foci and thrombosis in the right superior pulmonary vein. Following treatment with broad-spectrum antibiotics and anticoagulants, the patient's clinical symptoms and inflammatory markers showed improvement. However, a computed tomography scan revealed the formation of a pulmonary abscess, and the patient experienced coma and epilepsy after severe coughing with massive hemoptysis. Multiple air embolisms were observed in the brain computed tomography. Eventually, the patient's family chose to discharge him from the hospital. CONCLUSIONS: This case highlights the rare and complex etiologies of stroke associated with infection in a young patient. Early detection, diagnosis, and appropriate treatment of infected systemic embolism in young patients are crucial to prevent serious complications.

Cerebral air embolism caused by aspiration pneumonia: A case report.

Herein, we report a rare case of arterial cerebral air embolism (aCAE), that was probably caused by aspiration pneumonia. An 84-year-old-male presented with sudden loss of consciousness. Computed tomography (CT) of the head revealed air shadows along the sulcus of the right frontal and left posterior lobes. The abdominothoracic CT revealed aspiration pneumonia in the right upper lung with cavity formation. His clinical symptoms lessened after the administration of an antiepileptic. Because there was no prior history of any medical treatment, the patient was diagnosed with a noniatrogenic aCAE. Furthermore, in the absence of a right-to-left shunt, we determined that the air embolization was caused by the aspiration pneumonia. aCAE is a rare disease that can lead to miserable conditions. Most of causes aCAE are iatrogenic. However, a few cases of noniatrogenic aCAE have been reported. Some reports have suggested an associated between iatrogenic aCAE and raised intrathoracic pressure, which could lead to air entry into the pulmonary vein via the damaged alveolar wall. Even in noniatrogenic aCAEs, a sudden increase in intrathoracic pressure may cause airflow via the alveolar wall into the pulmonary veins, resulting in aCAE.

[Venous air embolism following removal of central venous catheters: A case report].

Air embolism is a rare but dreaded complication of medical or surgical procedures with significant mortality. An abnormal air-to-blood pressure gradient and communication between the vein and atmosphere can lead to the venous air embolism. Here, we presented a rare case of venous air embolism just after the removal of the central venous catheters. A 59-year-old female was admitted to Peking University International Hospital suffering from neuromyelitis optica spectrum disorder. After 5 rounds of immunosorbent therapy, her hemodialysis catheter was removed. Five hours later, she suddenly experienced shortness of breath, dizziness, weakness of the lower extremities, transient loss of consciousness and seizures. Ultrasound showed a small amount of gas in the right internal jugular vein and brain CT showed scattered air accumulation in part of venous blood ducts and bilateral cavernous sinuses, which was diagnosed as air embolism. High-flow oxygen inhalation, compression of the right neck extubation site, head down and feet up left decubitus position, intravenous fluid therapy were used. The patient gradually improved and returned to normal activities after one week. To sum up, air embolism is a rare, but serious and life-threatening complication after central catheters removal. Clinicians need to be alerted and take appropriate preventive measures.

Cerebral Arterial and Venous Air Embolism Following Removal of Percutaneous Sheath Introducer.

Cerebral air embolism after removal of central venous catheter (CVC) is a rare complication but can lead to fatal outcomes. We report a rare case of both cerebral venous and arterial embolism occurring in a patient with underlying scleroderma-related interstitial lung disease (SSc-ILD) and pulmonary hypertension following removal of percutaneous introducer sheath for pulmonary artery catheterization. We discuss the mechanisms, pathophysiology, management and prevention of cerebral air embolism.

Fatal cardiac air embolism after CT-guided percutaneous needle lung biopsy: medical complication or medical malpractice?

Computed tomography (CT)-guided percutaneous needle biopsy of the lung is a well-recognized and relatively safe diagnostic procedure for suspicious lung masses. Systemic air embolism (SAE) is a rare complication of transthoracic percutaneous lung biopsies. Herein, we present a case of an 81-year-old man who underwent CT-guided percutaneous needle biopsy of a suspicious nodule in the lower lobe of the right lung. Shortly after the procedure, the patient coughed up blood which prompted repeat CT imaging. He was found to have a massive cardiac air embolism. The patient became unresponsive and, despite resuscitation efforts, was pronounced dead. The pathophysiology, risk factors, clinical features, radiological evidence, and autopsy findings associated with SAE are discussed, which may, in light of the current literature, assist with the dilemma between assessing procedural complications and medical liability. Given the instances of SAE in the setting of long operative procedures despite careful technical execution, providing accurate and in-depth information, including procedure-related risks, even the rarest but potentially fatal ones, is recommended for informed consent to reduce medicolegal litigation issues.

Commentary on "Fatal cardiac air embolism after CT-guided percutaneous needle lung biopsy: medical complication or medical malpractice?"

To differentiate between medical malpractice and expected, but rare, medical complication in a medicolegal autopsy context is often difficult. Such an assessment requires knowledge about the clinical practice associated with the procedure at hand, and that findings of the autopsy, including medical relevant information such as patient chart, radiological imaging, and statements from witnesses about the medical procedure itself, provides evidence that substantiate either conclusion. In a case report published in the journal such an assessment is discussed by presenting findings and circumstances surrounding the death of a patient during a percutaneous needle lung biopsy procedure. The authors conclude that the death was not due to medical malpractice. However, in this commentary it is highlighted that the reasoning behind the conclusion needs to be further substantiated.

Air embolism during unsuccessful transcatheter closure of secundum atrial septal defect in a patient with an undetected left-sided inferior vena cava.

A 46-year-old man with a history of secundum atrial septal defect and interstitial lung disease was admitted to the hospital for a planned transcatheter closure of the atrial septal defect. Following multiple failed attempts to place a right femoral vein catheter, the procedure was aborted. Another attempt was made to the left femoral vein, but that attempt was complicated by an unfamiliar resistance. Even though resistance was met during insertion, the catheter was further inserted until a position in the inferior vena cava above the liver was obtained at fluoroscopy. Simultaneously, the patient became unresponsive. The procedure was immediately aborted and the atrial septal defect closure was not completed. Air embolism to the heart and brain was detected using echocardiography and computed tomography. The patient died 15 days after the procedure. Death was attributed to severe cerebral edema due to air embolism. The autopsy revealed a left-sided inferior vena cava. This case report demonstrates that unexpected congenital vascular anomalies complicating a routine transcatheter closure of the atrial septal defect can result in a fatal outcome.

Experimental Model of Cerebral Arterial Air Embolism in Conscious Rats.

In this work, an optimal air supply mode was selected to create a model of cerebral arterial air embolism (CAAE) on conscious male Sprague-Dawley rats (n=49). The efficacy of the selected model (administration of 100 µl/kg of air at a rate of 10 µl/min with an infusion pump) was determined by changes in serum biochemical parameters (cholesterol, alkaline phosphatase, inorganic phosphates, AST, and triglycerides), impaired motor functions in the Rotarod test, and visual assessment of the ischemic foci (staining of frontal sections with 1% triphenyltetrazolium chloride solution) at different terms after AAE. The model of AAE created by us confirmed impairment of coordination and motor function in conscious animals and reproduced the lethal consequences of this condition. The obtained results can serve as the basis for drug testing and the development of new approaches to the treatment of ischemic stroke.

Modeling of Cerebral Ischemic Stroke in Conscious Rats via Arterial Air Embolization.

The etiological factor of cerebral ischemia in the vast majority of cases is vascular embolism. In the present study we investigated embolism caused by atmospheric air bubbles injected into the internal carotid artery of conscious rats. Immediately after embolism modeling, behavioral abnormalities were observed in the animals, and after 24 h, foci of brain damage were detected. The death of animals was observed within 5 days after embolism. The proposed experimental model of cerebral ischemia in conscious rats is more relevant and better corresponds to real conditions than the model on narcotized animals and allows to perform physiological tests immediately after modeling.

Investigation of Experimental Endovascular Air Embolisms Using a New Model for the Generation and Detection of Highly Calibrated Micro Air Bubbles.

BACKGROUND: Air embolism (AE), especially when affecting the brain, is an underrated and potentially life-threatening complication in various endovascular interventions. This study aims to investigate experimental AEs using a new model to generate micro air bubbles (MAB), to assess the impact of a catheter on these MAB, and to demonstrate the applicability of this model in vivo. MATERIALS AND METHODS: Micro air bubbles were created using a system based on microfluidic channels. The MAB were detected and analyzed automatically. Micro air bubbles, with a target size of 85 µm, were generated and injected through a microcatheter. The MAB diameters proximal and distal to the catheter were assessed and compared. In a subsequent in vivo application, 2000 MAB were injected into the aorta (at the aortic valve) and into the common carotid artery (CCA) of a rat, respectively, using a microcatheter, resembling AE occurring during cardiovascular interventions. RESULTS: Micro air bubbles with a highly calibrated size could be successfully generated (median: 85.5 µm, SD 1.9 µm). After passage of the microcatheter, the MAB were similar in diameter (median: 86.6 µm) but at a lower number (60.1% of the injected MAB) and a substantially higher scattering of diameters (SD 29.6 µm). In vivo injection of MAB into the aorta resulted in cerebral microinfarctions in both hemispheres, whereas injection into the CCA caused exclusively ipsilateral microinfarctions. CONCLUSION: Using this new AE model, MAB can be generated precisely and reproducibly, resulting in cerebral microinfarctions. This model is feasible for further studies on the pathophysiology and prevention of AE in cardiovascular procedures.

Eliminating transseptal sheath exchange for pulsed field ablation procedures using a direct over-the-needle transseptal access with the Faradrive sheath.

AIMS: Pulsed field ablation (PFA) for pulmonary vein isolation (PVI) combines the benefits of high procedural efficacy and safety. Transseptal puncture (TSP) to obtain left atrial (LA) access during PVI remains an important source of complications during LA procedures. For PFA procedures, TSP is generally performed using a standard transseptal sheath that is then exchanged over the wire for a dedicated PFA sheath, which might be a potential source for air embolism. We aimed to prospectively evaluate the feasibility and safety of a simplified workflow using the PFA sheath (Faradrive, Boston Scientific) directly for TSP. METHODS AND RESULTS: We prospectively enrolled 100 patients undergoing PVI using PFA at two centres. TSP was performed using the PFA sheath and a standard 98 cm transseptal needle under fluoroscopic guidance. TSP via the PFA sheath was successfully performed in all patients and no complications occurred. The median time from the first groin puncture to the completed LA access was 12 min (IQR 8-16 min). CONCLUSION: An over-the-needle TSP directly with the PFA sheath proved feasible and safe in our study. This simplified workflow has the potential to reduce the risk of air embolism, to shorten procedure time, and to reduce cost.

Early hyperbaric oxygen therapy is associated with favorable outcome in patients with iatrogenic cerebral arterial gas embolism: systematic review and individual patient data meta-analysis of observational studies.

BACKGROUND: Iatrogenic cerebral arterial gas embolism (CAGE) caused by invasive medical procedures may be treated with hyperbaric oxygen therapy (HBOT). Previous studies suggested that initiation of HBOT within 6-8 h is associated with higher probability of favorable outcome, when compared to time-to-HBOT beyond 8 h. We performed a group level and individual patient level meta-analysis of observational studies, to evaluate the relationship between time-to-HBOT and outcome after iatrogenic CAGE. METHODS: We systematically searched for studies reporting on time-to-HBOT and outcome in patients with iatrogenic CAGE. On group level, we meta-analyzed the differences between median time-to-HBOT in patients with favorable versus unfavorable outcome. On individual patient level, we analyzed the relationship between time-to-HBOT and probability of favorable outcome in a generalized linear mixed effects model. RESULTS: Group level meta-analysis (ten studies, 263 patients) shows that patients with favorable outcome were treated with HBOT 2.4 h (95% CI 0.6-9.7) earlier than patients with unfavorable outcome. The generalized linear mixed effects model (eight studies, 126 patients) shows a significant relationship between time-to-HBOT and probability of favorable outcome (p = 0.013) that remains significant after correcting for severity of manifestations (p = 0.041). Probability of favorable outcome decreases from approximately 65% when HBOT is started immediately, to 30% when HBOT is delayed for 15 h. CONCLUSIONS: Increased time-to-HBOT is associated with decreased probability of favorable outcome in iatrogenic CAGE. This suggests that early initiation of HBOT in iatrogenic CAGE is of vital importance.

Pneumocephalus; a rare cause of coma.

We report the case of an 84-years old female patient who developed cerebral air embolism in association with the indwelling hemodialysis central venous catheter. Pneumocephalus, even though rare, should be included in the differential diagnosis of acute manifestation of neurologic deficits, especially in association with central venous access, surgical interventions or trauma, and requests prompt management. Brain computed tomography scanning remains the investigation of choice.