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.

Transesophageal echocardiography detection of air embolism during endoscopic surgery and validity of hyperbaric oxygen therapy: Case report.

INTRODUCTION: Air embolism has the potential to be serious and fatal. In this paper, we report 3 cases of air embolism associated with endoscopic medical procedures in which the patients were treated with hyperbaric oxygen immediately after diagnosis by transesophageal echocardiography. In addition, we systematically review the risk factors for air embolism, clinical presentation, treatment, and the importance of early hyperbaric oxygen therapy efficacy after recognition of air embolism. PATIENT CONCERNS: We present 3 patients with varying degrees of air embolism during endoscopic procedures, one of which was fatal, with large amounts of gas visible in the right and left heart chambers and pulmonary artery, 1 showing right heart enlargement with increased pulmonary artery pressure and tricuspid regurgitation, and 1 showing only a small amount of gas images in the heart chambers. DIAGNOSES: Based on ETCO2 and transesophageal echocardiography (TEE), diagnoses of air embolism were made. INTERVENTIONS: The patients received symptomatic supportive therapy including CPR, 100% O2 ventilation, cerebral protection, hyperbaric oxygen therapy and rehabilitation. OUTCOMES: Air embolism can causes respiratory, circulatory and neurological dysfunction. After aggressive treatment, one of the 3 patients died, 1 had permanent visual impairment, and 1 recovered completely without comorbidities. CONCLUSIONS: While it is common for small amounts of air/air bubbles to enter the circulatory system during endoscopic procedures, life-threatening air embolism is rare. Air embolism can lead to serious consequences, including respiratory, circulatory, and neurological impairment. Therefore, early recognition of severe air embolism and prompt hyperbaric oxygen therapy are essential to avoid its serious complications.

Hemodialysis Emergencies: Core Curriculum 2021.

Since maintenance hemodialysis (HD) first became available in the United States in 1962, there has been tremendous growth in the population of patients with kidney failure. HD has become a routine treatment carried out in outpatient clinics, hospitals, nursing facilities, and in patients' homes. Although it is a complex procedure, HD is quite safe. Serious complications are uncommon due to the use of modern HD machines and water treatment systems as well as the development of strict protocols to monitor various aspects of the HD treatment. The practicing nephrologist must be knowledgeable about life-threatening complications that can occur during HD and be able to recognize, manage, and prevent them. This installment in the AJKD Core Curriculum in Nephrology reviews the pathogenesis, management, and prevention of 9 HD emergencies. The HD emergencies covered include dialyzer reactions, dialysis disequilibrium syndrome, uremic/dialysis-associated pericarditis, air embolism, venous needle dislodgement, vascular access hemorrhage, hemolysis, dialysis water contamination, and arrhythmia episodes.

Enhancing vigilance for cerebral air embolism after pneumonectomy: a case report.

BACKGROUND: Vascular air embolism (VAE) is a rare but important complication that has not been paid enough attention to in the medical process such as surgery and anesthesia. CASE PRESENTATION: We report for the first time that a 54-year-old male patient with central lung cancer developed severe complications of CAE after right pneumonectomy. After targeted first-aid measures such as assisted breathing, mannitol dehydration and antibiotic treatment, the patient gradually improved. The patient became conscious at discharge after 25 days of treatment but left limb was left with nerve injury symptoms. CONCLUSION: We analyzed the possible causes of CAE in this case, and the findings from this report would be highly useful as a reference to clinicians.

A case of a critically injured diver with multiorgan failure and severe pulmonary overinflation syndrome in a resource-limited setting.

A diver practicing controlled emergency ascent training on the island of Guam suffered bilateral pneumothorax, pneumomediastinum, coronary arterial gas embolism, and developed multiple organ dysfunction syndrome. Due to limitations of available resources he was medically managed in the intensive care unit until he could be transferred to University of California San Diego for definitive management. We provide an account of our management of the patient, the pathophysiology of injury as well as a review of the safety of recreational diving skills training, current standards of practice and potential pitfalls when considering proper management of a critically injured diver.

On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean.

Decompression sickness (DCS) was first diagnosed in marine turtles in 2014. After capture in net fisheries, animals typically start showing clinical evidence of DCS hours after being hauled on-board, often dying if untreated. These turtles are normally immediately released without any understanding of subsequent clinical problems or outcome. The objectives of this study were to describe early occurrence and severity of gaseous embolism (GE) and DCS in marine turtles after incidental capture in trawl gear, and to provide estimates of on-board and post-release mortality. Twenty-eight marine turtles were examined on-board fishing vessels. All 20 turtles assessed by ultrasound and/or post-mortem examination developed GE, independent of season, depth and duration of trawl and ascent speed. Gas emboli were obvious by ultrasound within 15 minutes after surfacing and worsened over the course of 2 hours. Blood data were consistent with extreme lactic acidosis, reduced glomerular filtration, and stress. Twelve of 28 (43%) animals died on-board, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days. This is the first empirically-based estimate of on-board and post-release mortality of bycaught marine turtles that has until now been unaccounted for in trawl fisheries not equipped with turtle excluder devices.

Cardiac-Neurovascular Adverse Effects Responsible to Contrast Transcranial Doppler: A Case Report.

Introduction and Case Presentation: A 44-year-old female patient suffered migraines and underwent contrast-enhanced transcranial Doppler (c-TCD). During the rapid injection of contrast agent, she suffered chest tightness, palpitation, decreased consciousness, perimouth numbness, and headache, respectively. Meanwhile, "curtain" pattern of air embolic signals lasted up to 115 seconds in her decreased right middle cerebral artery accompanied with arrhythmia. The microair embolic signals lasted as long as 340 seconds. The patient's symptoms were relieved in 30 minutes. The aforementioned symptoms and signs occurred, lasted, then disappeared coinciding in time with changes of microbubbles. The woman was later found to have ventricular septal defect. Discussion: The adverse effects to cardiac-neurovascular system of c-TCD are reported for the first time, which arouse attention to safety of the procedure.

Cerebral Air Embolism after Esophagogastroduodenoscopy: Insight on Pathophysiology, Epidemiology, Prevention and Treatment.

BACKGROUND: Air embolism is an extremely rare complication that can follow gastrointestinal endoscopy. The most accepted treatment of cerebral air embolism (CAE) is hyperbaric oxygen (HBO). Limited evidence suggests that lidocaine may have a neuroprotective effect. The exact mechanism does not appear to be well elucidated. METHODS: We conducted a literature search using multiple combinations of keywords from PubMed and Ovid Medline databases according to the PRISMA guidelines. We included articles with cases of air embolism caused by an esophagogastroduodenoscopy (EGD). We excluded cases related to other procedures e.g. colonoscopy, endoscopic retrograde cholangiopancreatography, cholangioscopy, Kasai procedure, bronchoscopy, laparoscopy or thoracoscopy. We were able to identify 30 cases of CAE associated with EGD. We included our experience in treating one patient with CAE after elective EGD. RESULTS: Given the results of our literature search and this patient's characteristics, we chose to treat our patient with HBO and lidocaine infusion. Our case series consists of 31 patients of post EGD CAE, the mean age was 63.7 ± 11.14 years, 38.7% of the patients were women (n = 12). 38.7% of the cases underwent esophageal dilatation (n = 12), while 19.35% had EGD biopsy (n = 6), 9.6% had variceal ligation (n = 3), and 3.22% had variceal banding (n = 1). In 20 out of 31 cases, echocardiography has been documented, 20% of those patients (n = 4) had patent foramen ovale. HBO was used in treatment of 48% of cases (n = 15), among the included patients, 61% survived (n = 19). Our patient showed significant neurological improvement. CONCLUSIONS: Despite the rare incidence of CAE during or after EGD, physicians should be aware of this potential complication. In patients who develop sudden acute neurological symptoms, early diagnosis and intervention may prevent devastating neurological injury and death. The most accepted emergent treatment for CAE includes HBO, consideration of lidocaine, and work-up of source of the air embolism.

Distribution of Air Embolization During TEVAR Depends on Landing Zone: Insights From a Pulsatile Flow Model.

Purpose: To analyze the distribution of air bubbles in the supra-aortic vessels during thoracic stent-graft deployment in zones 2 and 3 in an aortic flow model. Materials and Methods: Ten identical, investigational, tubular, thoracic stent-grafts were deployed in a glass aortic flow model with a type I arch: 5 in zone 2 and 5 in zone 3. A pulsatile pump generated a flow of 5 L/min with systolic and diastolic pressures (±5%) of 105 and 70 mm Hg, respectively. The flow rates (±5%) were 300 mL/min in the subclavian arteries, 220 mL/min in the vertebral arteries, and 400 mL/min in the common carotid arteries (CCAs). The total amounts of air released in each supra-aortic branch and in the aorta were recorded. Results: The mean amounts of air measured were 0.82±0.23 mL in the zone-2 group and 0.94±0.28 mL in the zone-3 group (p=0.49). In the zone-2 group compared with zone 3, the amounts of released air were greater in the right subclavian artery (0.07±0.02 vs 0.02±0.02 mL, p<0.01) and right CCA (0.30±0.8 vs 0.18±07 mL, p=0.04). There were no differences between the groups concerning the mean amounts of air measured in the right vertebral and all left-side supra-aortic branches. The amount of air released in the descending aorta was significantly higher in the zone-3 group vs the zone-2 group (0.48±0.12 vs 0.13±0.08 mL, p<0.01). Small bubbles were observed continuously during deployment, whereas large bubbles appeared more commonly during deployment of the proximal stent-graft end and after proximal release of the stent-graft. Conclusion: Air is released into all supra-aortic branches and the descending aorta during deployment of tubular thoracic stent-grafts in zones 2 and 3 in an aortic flow model. Higher amounts of air were observed in right-side supra-aortic branches during deployment in zone 2, whereas significantly greater amounts of air were observed in the descending aorta during deployment in zone 3.

The relationship between end-expired carbon dioxide tension and severity of venous air embolism during sitting neurosurgical procedures - A contemporary analysis.

STUDY OBJECTIVE: Determine if changes in expired carbon dioxide tension correlate with the severity of venous air embolism (VAE) associated hemodynamic changes in humans. DESIGN: Retrospective case series. SETTING: A single academic medical center with high-volume neurosurgical practice. PATIENTS: One hundred forty seven adult patients having neurosurgical procedures performed with general anesthesia in the sitting position who experienced venous air embolism. INTERVENTIONS: Identification of documentation of venous air embolism by either precordial Doppler sonography or transesophageal echocardiography. MEASUREMENT: Retrospective determination of changes in end-expired carbon dioxide (EECO2) changes associated with venous air embolism. MAIN RESULTS: Greater absolute and relative decreases in end-expired carbon dioxide tension were associated with greater hemodynamic manifestations of venous air embolism. However, based on receiver operating characteristic curve analysis, the absolute and relative changes in EECO2 have moderate utility for predicting the severity of hemodynamic consequences of venous air embolism as area under the curve for absolute and relative carbon dioxide tensions were 0.7654 and 0.7263, respectively. CONCLUSIONS: Greater magnitude of decreases in EECO2 is associated with hemodynamically-significant VAE in mechanically-ventilated patients. However, the magnitude of changes may have limited utility to diagnose VAE or exclude the diagnosis of VAE in patients with unexplained intraoperative hypotension.

Inspiratory and expiratory resistance cause right-to-left bubble passage through the foramen ovale.

A patent foramen ovale (PFO) is linked to increased risk of decompression illness in divers. One theory is that venous gas emboli crossing the PFO can be minimized by avoiding lifting, straining and Valsalva maneuvers. Alternatively, we hypothesized that mild increases in external inspiratory and expiratory resistance, similar to that provided by a SCUBA regulator, recruit the PFO. Nine healthy adults with a Valsalva-proven PFO completed three randomized trials (inspiratory, expiratory, and combined external loading) with six levels of increasing external resistance (2-20 cmH2 O/L/sec). An agitated saline contrast echocardiogram was performed at each level to determine foramen ovale patency. Contrary to our hypothesis, there was no relationship between the number of subjects recruiting their PFO and the level of external resistance. In fact, at least 50% of participants recruited their PFO during 14 of 18 trials and there was no difference between the combined inspiratory, expiratory, or combined external resistance trials (P > 0.05). We further examined the relationship between PFO recruitment and intrathoracic pressure, estimated from esophageal pressure. Esophageal pressure was not different between participants with and without a recruited PFO. Intrasubject variability was the most important predictor of PFO patency, suggesting that some individuals are more likely to recruit their PFO in the face of even mild external resistance. Right-to-left bubble passage through the PFO occurs in conditions that are physiologically relevant to divers. Transthoracic echocardiography with mild external breathing resistance may be a tool to identify divers that are at risk of PFO-related decompression illness.

Variability in circulating gas emboli after a same scuba diving exposure.

PURPOSE: A reduction in ambient pressure or decompression from scuba diving can result in ultrasound-detectable venous gas emboli (VGE). These environmental exposures carry a risk of decompression sickness (DCS) which is mitigated by adherence to decompression schedules; however, bubbles are routinely observed for dives well within these limits and significant inter-personal variability in DCS risk exists. Here, we assess the variability and evolution of VGE for 2 h post-dive using echocardiography, following a standardized pool dive in calm warm conditions. METHODS: 14 divers performed either one or two (with a 24 h interval) standardized scuba dives to 33 mfw (400 kPa) for 20 min of immersion time at NEMO 33 in Brussels, Belgium. Measurements were performed at 21, 56, 91 and 126 min post-dive: bubbles were counted for all 68 echocardiography recordings and the average over ten consecutive cardiac cycles taken as the bubble score. RESULTS: Significant inter-personal variability was demonstrated despite all divers following the same protocol in controlled pool conditions: in the detection or not of VGE, in the peak VGE score, as well as time to VGE peak. In addition, intra-personal differences in 2/3 of the consecutive day dives were seen (lower VGE counts or faster clearance). CONCLUSIONS: Since VGE evolution post-dive varies between people, more work is clearly needed to isolate contributing factors. In this respect, going toward a more continuous evaluation, or developing new means to detect decompression stress markers, may offer the ability to better assess dynamic correlations to other physiological parameters.

The HYSTER study: the effect of intracervically administered terlipressin versus placebo on the number of gaseous emboli and fluid intravasation during hysteroscopic surgery: study protocol for a randomized controlled clinical trial.

BACKGROUND: Transcervical resection of myoma or endometrium is a safe, hysteroscopic, minimally invasive procedure. However, intravasation of distension fluid is a common phenomenon during these procedures. In a previous study we observed venous gas emboli in almost every patient. The severity of hysteroscopic-derived embolization has been shown to be correlated to the amount of intravasation. In addition, paradoxical gas embolism, which is potentially dangerous, was observed in several patients. Studies have shown a reduction of intravasation by using intracervically administered vasopressin during hysteroscopy. We think that its analog, terlipressin, should have the same effect. In our previous research we observed more gaseous emboli as intravasation increased. Whether or not the insertion of intracervically administered terlipressin leads to a lower incidence and severity of gas embolism is unknown. We hypothesize that intracervically administered terlipressin leads to a reduction of intravasation with a lower incidence and severity of gas embolism. Terlipressin may be of benefit during hysteroscopic surgery. METHODS/DESIGN: Forty-eight patients (ASA 1 or 2) scheduled for transcervical resection of large, types 1-2 myoma or extensive endometrium resection will be included. In a double-blind fashion patients will be randomized 1:1 according to surgical treatment using either intracervically administered terlipressin or placebo. Transesophageal echocardiography will be used to observe and record embolic events. A pre- and post-procedure venous blood sample will be taken to calculate intravasation based on hemodilution. Our primary endpoint will be how terlipressin influences the severity of embolic events. Secondary endpoints include the effect of terlipressin on the amount of intravasation and on hemodynamic parameters. DISCUSSION: If terlipressin does indeed reduce the number of gaseous emboli and intravasation occurring during hysteroscopic surgery, it would be a simple method to minimize potential adverse events. It also allows for prolonged operating time before the threshold of intravasation is reached, thereby reducing the need for a second operation. TRIAL REGISTRATION: Nederlands Trial Register (Dutch Trial Register), ID: NTR5577 . Registered retrospectively on 18 December 2015.

Seesawing end-tidal carbon dioxide: portent of critical carbon dioxide embolism in retroperitoneoscopy.

An abrupt increase in end-tidal CO2 (EtCO2; from 35 to 58 mm Hg) followed by a sudden fall (to 18 mm Hg) was noted during retroperitoneoscopic adrenalectomy under general anaesthesia in a 23-year-old patient with adrenal hyperplasia. This was accompanied by hypotension (systolic blood pressure of 60 mm Hg), desaturation (88% SpO2) and ST depression (3.5 mm). The patient was resuscitated with fluids and vasopressor drugs and about 4 mL of air was aspirated through the central venous catheter, confirming the diagnosis of an intraoperative gas embolism. Later, a rent in the adrenal vein extending into the inferior vena cava was discovered and sutured. The blood pressure, EtCO2, ST segment and pulse oximetry returned to normal after 15 min. This case demonstrates that gas embolism may transpire during retroperitoneoscopic adrenalectomy and an acute rise followed by a sharp fall in EtCO2 should alert the anaesthesiologist to this rare but potentially fatal complication.

Cardiac Air Embolism in Neonates: A Hemodynamic Perspective.

Cardiac air embolism should be suspected in any neonate with acute unexplained cardiovascular collapse or worsening oxygenation. We present here five cases that presented with the above symptoms. A comprehensive evaluation including targeted neonatal echocardiography and near-infrared spectroscopy helped confirm the diagnosis and assess the hemodynamic state. Management was supportive including left lateral positioning, chest compressions, and cardiovascular medications to treat pulmonary hypertension and systemic hypotension.

Medical Management and Risk Reduction of the Cardiovascular Effects of Underwater Diving.

Undersea diving is a sport and commercial industry. Knowledge of potential problems began with Caisson disease or "the bends", first identified with compressed air in the construction of tunnels under rivers in the 19th century. Subsequently, there was the commercially used old-fashioned diving helmet attached to a suit, with compressed air pumped down from the surface. Breathhold diving, with no supplementary source of air or other breathing mixture, is also a sport as well as a commercial fishing tool in some parts of the world. There has been an evolution to self-contained underwater breathing apparatus (SCUBA) diving with major involvement as a recreational sport but also of major commercial importance. Knowledge of the physiology and cardiovascular plus other medical problems associated with the various forms of diving have evolved extensively. The major medical catastrophes of SCUBA diving are air embolism and decompression sickness (DCS). Understanding of the essential referral to a hyperbaric recompression chamber for these problems is critical, as well as immediate measures until that recompression is achieved. These include the administration of 100% oxygen and rehydration with intravenous normal saline. Undersea diving continues to expand, especially as a sport, and a basic understanding of the associated preventive and emergency medicine will decrease complications and save lives.