Hyperbaric oxygen therapy for massive arterial air embolism during cardiac operations

Spontaneous Air Embolism Following Contrast Injection: A Diagnostic Challenge in a Post-COVID-19 Patient

A 72-year-old male with a complex medical history, including chronic obstructive pulmonary disease (COPD), hypertension, atrial fibrillation, and a recent COVID-19 infection, presented to the emergency department with shortness of breath and chest pain. Physical examination revealed stable vital signs but notable bilateral decreased air entry and diffuse wheezing. A computed tomography angiogram (CTA) of the chest confirmed a small to moderate volume of air embolism within the main pulmonary artery and right ventricle, with no evidence of pulmonary embolism. The air embolism was suspected to have been introduced during a contrast injection for the CT scan, as no other iatrogenic factors, recent invasive procedures, or history of lung trauma were present. Initial management included repositioning the patient to a supine position and administering 100% oxygen, which was critical in stabilizing his condition. Despite the ongoing symptoms of shortness of breath, the patient's condition improved with supportive care focused on managing COPD exacerbation. Spontaneous air embolism without decompression sickness or prior instrumentation is exceptionally rare, particularly in a post-COVID-19 patient, making this case notable. It highlights the critical need for prompt recognition, thorough evaluation, and appropriate management of air embolism in complex medical scenarios to prevent life-threatening complications. This case also underscores the importance of considering iatrogenic causes, such as contrast injection, in the differential diagnosis, especially following recent imaging studies.

Chinese expert consensus on cone-beam CT-guided diagnosis, localization and treatment for pulmonary nodules

Cone-beam computed tomography (CBCT) system can provide real-time 3D images and fluoroscopy images of the region of interest during the operation. Some systems can even offer augmented fluoroscopy and puncture guidance. The use of CBCT for interventional pulmonary procedures has grown significantly in recent years, and numerous clinical studies have confirmed the technology's efficacy and safety in the diagnosis, localization, and treatment of pulmonary nodules. In order to optimize and standardize the technical specifications of CBCT and guide its application in clinical practice, the consensus statement has been organized and written in a collaborative effort by the Professional Committee on Interventional Pulmonology of China Association for Promotion of Health Science and Technology.

Preventive Hyperbaric Oxygen Therapy for Asymptomatic Left Ventricular Air During CT-Guided Lung Needle Biopsy

Lung needle biopsy can cause air to enter the vessels due to the traffic between the vessels and the trachea. Hyperbaric oxygen therapy (HBOT) according to the U.S. Navy Treatment Table (USNTT) 6 or 6A protocol is used for arterial gas embolism (AGE). However, no treatment or HBOT protocol for asymptomatic intra-arterial air has been established. Here we report two cases of asymptomatic intra-arterial air during lung needle biopsy that were preventively treated with HBOT according to the USNTT 5 protocol. In case 1, a 72-year-old man with malignant lymphoma in remission underwent computed tomography (CT)-guided lung needle biopsy of a nodule in his right lung. During the biopsy, the patient developed a cough, followed by chest pain and dyspnea. Chest CT revealed a right pneumothorax and air in the left ventricle and aorta. The patient did not present with symptoms suggestive of AGE. After thoracic drainage, 4.5 hours after onset, the patient underwent HBOT according to the USNTT 5 protocol. After one session in the hyperbaric chamber, follow-up whole-body CT showed disappearance of intravascular air. In case 2, a 69-year-old man with chronic obstructive pulmonary disease underwent CT-guided lung needle biopsy of a nodule in his right lung. Post-examination CT showed intravascular air in the aorta, pulmonary artery and vein, and left ventricle. However, the patient had no symptoms. One hour after onset, the patient underwent HBOT according to the USNTT 5 protocol. A whole-body CT the next day confirmed the disappearance of intravascular air. Both patients were discharged without sequelae. HBOT is an effective treatment to flush out intra-arterial air and inhibit the expression of adhesion molecules. Asymptomatic intra-arterial air may be adequately treated with HBOT according to a short protocol such as USNTT 5.

Stroke and Mechanical Circulatory Support in Adults

PURPOSE OF THE REVIEW

Short-term and durable mechanical circulatory support (MCS) devices represent life-saving interventions for patients with cardiogenic shock and end-stage heart failure. This review will cover the epidemiology, risk factors, and treatment of stroke in this patient population.

RECENT FINDINGS

Short-term devices such as intra-aortic balloon pump, Impella, TandemHeart, and Venoatrial Extracorporal Membrane Oxygenation, as well as durable continuous-flow left ventricular assist devices (LVADs), improve cardiac output and blood flow to the vital organs. However, MCS use is associated with high rates of complications, including ischemic and hemorrhagic strokes which carry a high risk for death and disability. Improvements in MCS technology have reduced but not eliminated the risk of stroke. Mitigation strategies focus on careful management of anti-thrombotic therapies. While data on therapeutic options for stroke are limited, several case series reported favorable outcomes with thrombectomy for ischemic stroke patients with large vessel occlusions, as well as with reversal of anticoagulation for those with hemorrhagic stroke. Stroke in patients treated with MCS is associated with high morbidity and mortality. Preventive strategies are targeted based on the specific form of MCS. Improvements in the design of the newest generation device have reduced the risk of ischemic stroke, though hemorrhagic stroke remains a serious complication.

Iatrogenic air embolism: pathoanatomy, thromboinflammation, endotheliopathy, and therapies

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

Air Medical Transport of a 12-Year-Old Girl With Cerebral Gas Embolism Due to Helium Inhalation

This case report describes the initial care and transport considerations of a pediatric patient who suffered from cerebral gas embolism sustained after inhalation of helium from a pressurized tank. The patient demonstrated neurologic symptoms necessitating hyperbaric oxygen therapy and required fixed wing air transport across a mountain range from a rural community hospital to a tertiary center for the treatment. We review the pathophysiology of cerebral gas embolism and strategies for transporting patients with cerebral gas embolism and other trapped gas.

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.

Clinical Characteristics, Imaging Findings, and Outcomes of Cerebral Air Embolism

BACKGROUND

Arterial cerebral air embolism (CAE) is an uncommon but potentially catastrophic event. Patients can present with focal neurologic deficits, seizures, or coma. They may be treated with hyperbaric oxygen therapy. We review the causes, radiographic and clinical characteristics, and outcomes of patients with CAE.

METHODS

We performed a retrospective chart review via an existing institutional database at Mayo Clinic to identify patients with arterial CAE. Demographic data, clinical characteristics, and diagnostic studies were extracted and classified on predefined criteria of diagnostic confidence, and descriptive and univariate analysis was completed.

RESULTS

Fifteen patients met criteria for inclusion in our study. Most presented with focal deficits (80%) and/or coma (53%). Seven patients (47%) had seizures, including status epilepticus in one (7%). Five presented with increased muscle tone at the time of the event (33%). Computed tomography (CT) imaging was insensitive for the detection of CAE, only identifying free air in 4 of 13 who underwent this study. When obtained, magnetic resonance imaging typically showed multifocal areas of restricted diffusion. Six patients (40%) were treated with hyperbaric oxygen therapy. Age, Glasgow Coma Scale score at nadir, and use of hyperbaric oxygen therapy were not associated with functional outcome at 1 year in our cohort. Twenty-six percent of patients had a modified Rankin scale score of 0 one year after the event, and functional improvement over time was common after discharge.

CONCLUSIONS

A high index of clinical suspicion is needed to identify patients with CAE because of low sensitivity of free air on CT imaging and nonspecific clinical presentation. Acute alteration of consciousness, seizures, and focal signs occur frequently. Because improvement over time is possible even among patients with severe presentation, early prognostication should be approached with caution.

Bronchovenous Fistula During Adult Cardiac Surgery: A Case Report

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Bronchovenous fistula (BVF) associated with adult cardiac surgery is a rarely reported life-threatening condition. We present a 75-year-old woman who developed a BVF during cardiac surgery. Dense adhesion in the pleural and pericardial cavities was noted. Restrictive pulmonary pathology required high airway pressure. Transesophageal echocardiography and hemoglobin measurement were helpful for the timely diagnosis of BVF, which was controlled by transection of the right upper pulmonary vein where a vent catheter had been inserted. Injuries around the cannulated site presumably initiated the BVF, which was worsened by high-pressure ventilation. Therefore, cannulation site might be a risk factor for BVF.

To Take One's Breath Away: Echocardiography-Guided Aspiration of an Air Embolism During a MitraClip Procedure

An air embolism (AE) is a rare but dreaded complication during endovascular procedures. Current guidance recommends hyperbaric oxygen therapy and aspiration for the management of a venous AE. However, the management of an arterial AE is much less described. We report a case of a 79-year-old man with symptomatic mitral regurgitation who underwent a MitraClip procedure. During the intervention, a massive AE was detected in the ascending aorta on transesophageal echocardiography. The AE was successfully aspirated while the patient remained hemodynamically stable. This report demonstrates the efficacy of an arterial AE’s aspiration with a real-time echocardiography recording of the technique.

2020 Clinical Practice Guideline for Percutaneous Transthoracic Needle Biopsy of Pulmonary Lesions: A Consensus Statement and Recommendations of the Korean Society of Thoracic Radiology

Percutaneous transthoracic needle biopsy (PTNB) is one of the essential diagnostic procedures for pulmonary lesions. Its role is increasing in the era of CT screening for lung cancer and precision medicine. The Korean Society of Thoracic Radiology developed the first evidence-based clinical guideline for PTNB in Korea by adapting pre-existing guidelines. The guideline provides 39 recommendations for the following four main domains of 12 key questions: the indications for PTNB, pre-procedural evaluation, procedural technique of PTNB and its accuracy, and management of post-biopsy complications. We hope that these recommendations can improve the diagnostic accuracy and safety of PTNB in clinical practice and promote standardization of the procedure nationwide.

Arterial Gas Emboli Secondary to Portal Venous Gas Diagnosed With Point-of-Care Ultrasound: Case Report and Literature Review

BACKGROUND

Portal venous gas (PVG) is a rarely observed clinical finding generally associated with intestinal ischemia. The proper clinical response to the finding of PVG depends somewhat on the setting in which it is observed. Here we describe a case in which extensive arterial gas emboli (AGE) were encountered during point-of-care ultrasound (POCUS) and subsequent computed tomography (CT) identified PVG secondary to gastric wall ischemia as the likely source.

CASE REPORT

A 69-year-old woman with history of metastatic colon cancer presented to the emergency department (ED) with altered mental status. On arrival, she was hypotensive, hypothermic, cachectic, and with abdominal distension. POCUS was performed to evaluate the source of the patient's hypotension, revealing the presence of PVG, as well as gas bubbles in all four chambers of the heart and the aorta. CT scan revealed gastric wall ischemia and confirmed the presence of significant air emboli throughout the portal venous system. Given the overall poor prognosis, the decision was made to forego further chemotherapy or surgery and the patient died later that week while under hospice care. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: AGE can occur in the setting of PVG. This may cause multi-organ failure by disrupting blood flow to organs, especially in patients with circulatory dysfunction, such as shock. Depending on the setting in which it is diagnosed, early detection of PVG may expedite earlier assessments of a patient's negative prognosis or initiation of attempted life-saving treatment. In this case report, we show that POCUS can be used to obtain an expedited diagnosis in a critically ill patient.

Effective handling of substantial arterial air embolization during extracorporeal perfusion

This report highlights the need for a coordinated approach to substantial arterial air embolization, considering the high risk of neurologic injury. Appropriate management may involve systemic hypothermia, hyperoxia, and retrograde cerebral perfusion.

Perioperative Cerebral Ischaemia in Cardiac Surgery and BIS

A 46-year-old woman was monitored by bispectral index monitoring (BIS) during redo aortic and mitral valve replacement. On release of the aortic cross clamp there was a sudden, severe, unexplained, and sustained fall in the BIS value. Postoperatively, a CT scan was consistent with multiple ischaemic lesions. The lesions were presumed to be due to air embolism. This case suggests that a sudden unexplained and persistent fall in BIS may indicate cerebral ischaemia.

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Delayed hyperbaric oxygen therapy for air emboli after open heart surgery: case report and review of a success story

Background

The current case describes a rare diagnosis of iatrogenic air emboli after elective cardiopulmonary bypass that was successfully treated with delayed hyperbaric oxygen therapy, with good clinical evolution in spite of rare complications.

Case presentation

A 35 years old male was admitted to the intensive care unit (ICU) for post-operative management after being placed on cardiopulmonary bypass (CPB) for an elective ventricular septal defect closure and aortic valvuloplasty. The patient initially presented with pathologically late awakening and was extubated 17 h after admission. Neurologic clinical status after extubation showed global aphasia, mental slowness and spatio-temporal disorientation. The injected cerebral CT scan was normal; the EEG was inconclusive (it showed metabolic encephalopathy without epileptic activity); and the cerebral MRI done 48 h after surgery showed multiple small subcortical acute ischemic lesions, mainly on the left fronto- parieto- temporo-occipital lobes. He was taken for hyperbaric oxygen therapy (HOT) over 54 h after cardiac surgery. The first session ended abruptly after 20 min when the patient suffered a generalised tonico-clonic seizure, necessitating a moderately rapid decompression, airway management, and antiepileptic treatment. In total, the patient received 7 HOT sessions over 6 days. He demonstrated full neurological recovery at 4 weeks and GOS (Glasgow Outcome Scale) of 5 out of 5 even after a long delay in initial management. Convulsions are a rare complication of HOT either due to reperfusion syndrome or hyperoxic toxicity and can be managed. Prior imaging by MRI or tympanic paracentesis (myringotomy) should not add further delay of treatment.

Conclusion

HOT should be initiated upon late awakening and/or neurologic symptoms after CPB heart surgery, after exclusion of formal counter-indications, even if the delay exceeds 48 h.

Hyperbaric oxygen does not improve cerebral function when started 2 or 4 hours after cerebral arterial gas embolism in swine

OBJECTIVE

Hyperbaric oxygenation is the accepted treatment for cerebral arterial gas embolism. Although earlier start of hyperbaric oxygenation is associated with better outcome, it is unknown how much delay can be tolerated before start of hyperbaric oxygenation. This study investigates the effect of hyperbaric oxygenation on cerebral function in swine when initiated 2 or 4 hours after cerebral arterial gas embolism.

DESIGN

Prospective interventional animal study.

SETTING

Surgical laboratory and hyperbaric chamber.

SUBJECTS

Twenty-two Landrace pigs.

INTERVENTIONS

Under general anesthesia, probes to measure intracranial pressure, brain oxygen tension (PbtO2), and brain microdialysis, and electrodes for electroencephalography were placed. The electroencephalogram (quantified using temporal brain symmetry index) was suppressed during 1 hour by repeated injection of air boluses through a catheter placed in the right ascending pharyngeal artery. Hyperbaric oxygenation was administered using U.S. Navy Treatment Table 6 after 2- or 4-hour delay. Control animals were maintained on an inspiratory oxygen fraction of 0.4.

MEASUREMENTS AND MAIN RESULTS

Intracranial pressure increased to a mean maximum of 19 mm Hg (SD, 4.5 mm Hg) due to the embolization procedure. Hyperbaric oxygenation significantly increased PbtO2 in both groups treated with hyperbaric oxygenation (mean maximum PbtO2, 390 torr; SD, 177 torr). There were no significant differences between groups with regard to temporal brain symmetry index (control vs 2-hr delay, p = 0.078; control vs 4-hr delay, p = 0.150), intracranial pressure, and microdialysis values.

CONCLUSIONS

We did not observe an effect of hyperbaric oxygenation on cerebral function after a delay of 2 or 4 hours. The injury caused in our model could be too severe for a single session of hyperbaric oxygenation to be effective. Our study should not change current hyperbaric oxygenation strategies for cerebral arterial gas embolism, but further research is necessary to elucidate our results. Whether less severe injury benefits from hyperbaric oxygenation should be investigated in models using smaller amounts of air and clinical outcome measures.

Hyperbaric Oxygen Therapy in the Treatment of Post Cardiac Surgical Strokes – a Case Series and Review of the Literature

Strokes remain an uncommon but significant complication of cardiac surgery. Cerebral air embolism is the likely aetiology in the majority of cases. Hyperbaric oxygen therapy is the recognised treatment for cerebral air embolism associated with compressed air (SCUBA) diving accidents and is therefore also the standard of care for iatrogenic causes of air embolism. It follows that there is a logic in treating post-cardiac surgical stroke patients with hyperbaric oxygen.

The aim of this retrospective review was to examine the outcomes of 12 such patients treated in the Christchurch Hospital hyperbaric unit and to appraise the evidence base for the use of hyperbaric oxygen therapy in this setting.

Despite delays of up to 48 hours following surgery before the institution of hyperbaric oxygen therapy, 10 of the 12 patients made a full neurological recovery or were left with mild residual symptoms, with nine returning to their previous level of care. One patient remained hemiplegic and there was one early neurological death.

There is a paucity of prospective data in this area, but based on sound pathophysiological principles and clinical experience, we believe that patients suffering a stroke following open cardiac surgery should be considered for hyperbaric oxygen therapy.

[Paradoxal gazous embolism in hepatic trauma. Contribution of hyperbaric oxygenotherapy]

A young man was admitted for a polytraumatism associating head trauma and blunt abdominal trauma with hepatic injury. He was managed with a damage control surgery with a perihepatic packing. During the second look surgery, he developed a paradoxal gazous embolism by air aspiration in the sus-hepatic vein. This has never been described before in such traumatism. The patient presented a respiratory distress, a circulatory shock due to right infarction and an intracranial hypertension with bilateral mydriasis. He was immediately treated by hyperbaric oxygenotherapy. The evolution was good and he recovered without sequelae.

Paradoxical air embolism successfully treated with hyperbaric oxygen

The use of the central venous catheter may be complicated by air embolism when central venous pressure is subatmospheric and the catheter is open to the surrounding air. Paradoxical air embolus occurs when the gas bubbles are able to traverse a right to left shunt, gaining access to the systemic arterial circulation causing ischemic symptoms in end organs. In this article, a case of a patient with an unknown patent foramen ovale through which air entered the arterial circulation resulting in obtundation and stroke after inadvertent manipulation of a Hickman catheter is presented. The physiology, clinical manifestations, and management strategies are also discussed.

Arterial gas embolism: a review of cases at Prince of Wales Hospital, Sydney, 1996 to 2006

Arterial gas embolism may occur as a complication of diving or certain medical procedures. Although relatively rare, the consequences may be disastrous. Recent articles in the critical care literature suggest the non-hyperbaric medical community may not be aware of the role for hyperbaric oxygen therapy in non-diving related gas embolism. This review is part of an Australian appraisal of experience in the management of arterial gas embolism over the last 10 years. We identified all patients referred to Prince of Wales Hospital Department of Diving and Hyperbaric Medicine with a diagnosis of arterial gas embolism from 1996 to 2006. Twenty-six patient records met our selection criteria, eight iatrogenic and 18 diving related. All patients were treated initially with a 280 kPa compression schedule. At discharge six patients were left with residual symptoms. Four were left with minor symptoms that did not significantly impact quality of life. Two remained severely affected with major neurological injury. Both had non-diving-related arterial gas embolism. There was a good outcome in the majority of patients who presented with arterial gas embolism and were treated with compression.

Pulmonary arteriovenous malformation causing massive haemoptysis and complicated by coronary air embolism

We report the case of a 20-year-old man with possible Osler-Rendu-Weber syndrome (hereditary haemorrhagic telangiectasia) who developed an episode of massive haemoptysis from a bleeding pulmonary arteriovenous malformation in the left lower lobe of his lung. During the acute haemorrhage, he also appeared to suffer a coronary air embolism, possibly due to introduction of air into the bleeding arteriovenous malformation during intermittent positive pressure ventilation through the endotracheal tube. His electrocardiogram showed extensive ST elevation (>2 mm) in the inferolateral leads associated with raised troponin I and creatine kinase levels. These changes resolved within thirty minutes. The pulmonary arteriovenous malformation was successfully treated with a combination of alcohol injection and coil embolization.

Massive cerebral arterial air embolism following arterial catheterization

Microscopic cerebral arterial air embolism (CAAE) has been described in many patients undergoing cardiac surgery as well as other invasive diagnostic and therapeutic procedures. However, massive CAAE is rare. We report a 42-year-old woman who initially presented with thalamic and basal ganglia hemorrhages. Shortly after a radial arterial catheter was inserted, the patient suffered a generalized seizure and CT demonstrated intra-arterial air in bilateral cerebral hemispheres.

Effects of hyperbaric treatment in cerebral air embolism on intracranial pressure, brain oxygenation, and brain glucose metabolism in the pig*

OBJECTIVE

To evaluate the effects of hyperbaric oxygen treatment after cerebral air embolism on intracranial pressure, brain oxygenation, brain glucose/lactate metabolism, and electroencephalograph.

DESIGN

Prospective animal study.

SETTING

Hyperbaric chamber.

SUBJECTS

Eleven Landrace/Yorkshire pigs.

INTERVENTIONS

In 11 anesthetized pigs, intracranial pressure and brain oxygenation were measured with microsensor technology, brain glucose/lactate by microdialysis, and electroencephalograph by conventional methods. After injection of air into the internal carotid artery, animals were treated immediately (at 3 mins; t = 3) or at 60 mins (t = 60) with U.S. Navy Treatment Table 6 for 4.48 hrs.

RESULTS

At the end of hyperbaric oxygen treatment, intracranial pressure in the t = 60 group (39 +/- 8 mm Hg) was significantly higher than in the t = 3 group (27 +/- 6 mm Hg), brain oxygenation values for group t = 3 and t = 60 were 66 +/- 14 and 52 +/- 15 mm Hg, respectively (no significant difference from baseline), and there were no pathologic scores in the visually assessed electroencephalograph. However, there was a significant decrease in brain glucose and a significant increase in brain lactate in both groups at the end of the 5-hr study period.

CONCLUSIONS

Hyperbaric oxygen treatment initiated at both 3 and 60 mins after embolization decreased the deleterious effects of cerebral air embolism on intracranial pressure and brain metabolism. Therefore, this model appears suitable to test the application of hyperbaric oxygen treatment with a delay >60 mins after embolization, as is often the case in the clinical situation.

Venous oxygen embolism produced by injection of hydrogen peroxide into an enterocutaneous fistula

We report a venous oxygen embolism that occurred in a 66-yr-old man after 60 mL of 3% hydrogen peroxide was injected into a perianal fistula intraoperatively to locate its internal opening. The diagnosis was made after detecting hypoxemia, decreased end-tidal carbon dioxide tension, systemic hypotension, increased central venous pressure, and a new heart murmur. The patient recovered quickly and had no long-term sequelae. Oxygen embolism is a potentially fatal complication that can develop when hydrogen peroxide is used near venous spaces, and clinicians should be aware of the potential dangers when using this seemingly innocuous chemical.

Gas embolism: pathophysiology and treatment

Based on a literature search, an overview is presented of the pathophysiology of venous and arterial gas embolism in the experimental and clinical environment, as well as the relevance and aims of diagnostics and treatment of gas embolism. The review starts with a few historical observations and then addresses venous air embolism by discussing pulmonary vascular filtration, entrapment, and the clinical occurrence of venous air emboli. The section on arterial gas embolism deals with the main mechanisms involved, coronary and cerebral air embolism (CAE), and the effects of bubbles on the blood-brain barrier. The diagnosis of CAE uses various techniques including ultrasound, perioperative monitoring, computed tomography, brain magnetic resonance imaging and other modalities. The section on therapy starts by addressing the primary treatment goals and the roles of adequate oxygenation and ventilation. Then the rationale for hyperbaric oxygen as a therapy for CAE based on its physiological mode of action is discussed, as well as some aspects of adjuvant drug therapy. A few animal studies are presented, which emphasize the importance of the timing of therapy, and the outcome of patients with air embolism (including clinical patients, divers and submariners) is described.

Cerebral and coronary air embolism: an intradepartmental suicide attempt

Uncooperative but alert on arrival, a 21-year-old suicidal man was found suddenly unconscious with agonal respirations 2 h into his Emergency Department evaluation. Initially admitted for ingesting multiple pills and self-inflicting a deep wrist laceration, the patient now had a Glasgow Coma Scale score of 3, a dense left-sided hemiplegia, and an electrocardiogram suggestive of acute myocardial infarction. This constellation of physical findings, together with an echocardiogram revealing bi-ventricular gas artifact, led to a diagnosis of coronary and cerebral air emboli. The patient was urgently resuscitated and then underwent hyperbaric oxygen therapy. Subsequent examination confirmed a full recovery. This article details this unprecedented case, as well as clinically relevant aspects of air embolism.