gastrointestinal endoscopy has become a routine medical procedure for diagnostic and therapeutic purposes in many diseases . as the number of cases needing an endoscopic procedure has increased ,
the incidence of various complications have also increased , making their proper management more important [ 1 - 4 ] .
air embolism is a very rare endoscopic complication that manifests with cardiopulmonary instability and neurologic symptoms .
however , because of similar symptoms , it is difficult to distinguish cerebral infarction from sedative - related complications and , owing to its rarity and the unexplained mechanism involved , physicians rarely suspect brain damage induced by air embolism .
we here report our experiences with two adult cases of cerebral air embolism after endoscopic procedures  esophageal balloon dilatation and endoscopic papillary balloon dilatation ( epbd)and their clinical outcomes .
he had undergone a total gastrectomy with d2 dissection 2 years previously for gastric cancer , and the pathologic stage was t3n0m0 .
two months after the operation , bone metastasis was found and chemotherapy was applied with s-1 ( an oral fluorouracil chemotherapeutic agent ) . on admission , he had an eastern cooperative oncology group performance status of 3 and was restricted to a liquid diet .
this procedure was performed under sedation with intravenous midazolam ( 2 mg ) and with constant vital sign monitoring .
his vital signs were stable during the procedure , and through - the - scope ballooning was performed with a cover - edge wire - guided balloon dilatation catheter ( boston scientific , cork , ireland ) under the following conditions : to 8 mm for 30 seconds with 3 atmospheric pressure , 9 mm for 60 seconds with 4 atmospheric pressure , and 10 mm for 60 seconds with 9 atmospheric pressure ( fig .
after the procedure was completed , he became unresponsive ( glasgow coma scale , 3/15 ) , hypotensive ( systolic blood pressure / diastolic blood pressure , 66/41 mm hg ) , and hypopneic ( respiratory rate , 10 breaths per minute ) .
his vital signs stabilized after o2 was supplied through a venture mask ( fio2 50% ) , and after fluid resuscitation and flumazenil injection .
however , his altered mental status was not reversed after flumazenil injection . to determine the cause of the mental change , magnetic resonance imaging ( mri ) and brain computed tomography ( ct )
the therapy was instituted at 3 atmospheric pressure for 2 hours 45 minutes , and gradual decompressed was performed for 1 hour 5 minutes .
after hyperbaric therapy , the embolism had nearly disappeared in the follow - up mri and the vital signs had stabilized .
extubation was performed 4 days after the event , and left - sided weakness remained .
twelve months after the event , he still undergoes rehabilitation treatment for left - sided hemiparesis ; however , he can ambulate with minimal assistance .
a 69-year - old man was admitted to our hospital with persistent right upper quadrant pain since 2 weeks .
abdominal ct showed distal common bile duct stones , and he underwent therapeutic endoscopic retrograde cholangiopancreatography ( ercp ) under sedation with intravenous midazolam ( 2 mg ) .
multiple filling defects were found , and epbd was performed to avoid bleeding due to pericholedochal varices .
multiple stones were removed with a hurricane balloon dilatation catheter ( boston scientific ) ( fig .
1c , d ) , and a fully covered metal stent was inserted to compress the varices .
after ercp , he became unresponsive ( glasgow coma scale , 3/15 ) and hypoxic ( spo2 , 80% ) .
he subsequently became hypotensive and bradycardic , and finally progressed into pulseless electrical cardiac arrest .
brain mri and brain ct showed multiple cerebral infarctions ( right middle , left anterior , and left posterior cerebral artery territories ) ; however , the images could not distinguish air embolism from other causes .
high fio2 therapy was provided , and low - molecular - weight heparin was used because other infarction causes could not be ruled out . after 4 days , the patient s mental status was restored and he was extubated .
he underwent rehabilitation treatment for left - sided weakness , and the neurologic deficit improved considerably .
recently , at 2 months after the event , he is able to perform normal activities of daily living .
he had undergone a total gastrectomy with d2 dissection 2 years previously for gastric cancer , and the pathologic stage was t3n0m0 .
two months after the operation , bone metastasis was found and chemotherapy was applied with s-1 ( an oral fluorouracil chemotherapeutic agent ) . on admission , he had an eastern cooperative oncology group performance status of 3 and was restricted to a liquid diet .
this procedure was performed under sedation with intravenous midazolam ( 2 mg ) and with constant vital sign monitoring .
his vital signs were stable during the procedure , and through - the - scope ballooning was performed with a cover - edge wire - guided balloon dilatation catheter ( boston scientific , cork , ireland ) under the following conditions : to 8 mm for 30 seconds with 3 atmospheric pressure , 9 mm for 60 seconds with 4 atmospheric pressure , and 10 mm for 60 seconds with 9 atmospheric pressure ( fig .
after the procedure was completed , he became unresponsive ( glasgow coma scale , 3/15 ) , hypotensive ( systolic blood pressure / diastolic blood pressure , 66/41 mm hg ) , and hypopneic ( respiratory rate , 10 breaths per minute ) .
his vital signs stabilized after o2 was supplied through a venture mask ( fio2 50% ) , and after fluid resuscitation and flumazenil injection .
however , his altered mental status was not reversed after flumazenil injection . to determine the cause of the mental change , magnetic resonance imaging ( mri ) and brain computed tomography ( ct )
the therapy was instituted at 3 atmospheric pressure for 2 hours 45 minutes , and gradual decompressed was performed for 1 hour 5 minutes .
after hyperbaric therapy , the embolism had nearly disappeared in the follow - up mri and the vital signs had stabilized .
extubation was performed 4 days after the event , and left - sided weakness remained .
twelve months after the event , he still undergoes rehabilitation treatment for left - sided hemiparesis ; however , he can ambulate with minimal assistance .
a 69-year - old man was admitted to our hospital with persistent right upper quadrant pain since 2 weeks .
abdominal ct showed distal common bile duct stones , and he underwent therapeutic endoscopic retrograde cholangiopancreatography ( ercp ) under sedation with intravenous midazolam ( 2 mg ) .
multiple filling defects were found , and epbd was performed to avoid bleeding due to pericholedochal varices .
multiple stones were removed with a hurricane balloon dilatation catheter ( boston scientific ) ( fig .
1c , d ) , and a fully covered metal stent was inserted to compress the varices .
after ercp , he became unresponsive ( glasgow coma scale , 3/15 ) and hypoxic ( spo2 , 80% ) .
he subsequently became hypotensive and bradycardic , and finally progressed into pulseless electrical cardiac arrest .
brain mri and brain ct showed multiple cerebral infarctions ( right middle , left anterior , and left posterior cerebral artery territories ) ; however , the images could not distinguish air embolism from other causes .
. high fio2 therapy was provided , and low - molecular - weight heparin was used because other infarction causes could not be ruled out . after 4 days , the patient s mental status was restored and he was extubated .
he underwent rehabilitation treatment for left - sided weakness , and the neurologic deficit improved considerably .
recently , at 2 months after the event , he is able to perform normal activities of daily living .
we here present two cases of cerebral air embolism as a rare complication of therapeutic endoscopy .
however , the first patient now has a persistent left - sided hemiparesis . in our experience , early suspicion and proper management of air embolism
can improve clinical outcomes , although cerebral infarction due to air embolism is an extremely rare and unexpected complication that can not be completely explained and typically has a poor prognosis .
, the volume of air and rate of accumulation is important in determining the morbidity and mortality after a vascular air embolism develops . a large volume ( ~5 ml / kg ) or rapid entry of gas migrating to the pulmonary circulation places strain on the right ventricle .
this situation results in diminished cardiac output that leads to cardiovascular collapse and cerebral hypoperfusion .
venous gas embolism may migrate to the systemic circulation through a shunt such as a patent foramen ovale .
however , it has been reported that a large volume of venous gas can enter the arterial circulation through transpulmonary passage of air , without cardiac defects or shunt .
the air of the venous circulation enters the arterial systemic circulation and obstructs the end artery , which is a paradoxical embolism .
this mechanism can explain the presentation of our two current patients : the air around the balloon entered through the anastomosis site or biliary tract , and the venous embolism entered the arterial circulation through a transient patent foramen ovale or transpulmonary passage . to our knowledge , there have been 21 reported cases to date of cerebral embolism complications after an endoscopic procedure , including our current cases ( table 1 ) [ 7 - 24 ] .
the cerebral embolism occurred during or after ercp in 11 of these cases , and was found during or after another therapeutic esophagogastroduodenoscopy in the remaining 10 cases .
six of the 21 reported patients had undergone major surgery , such as billroth ii operation , total gastrectomy , or whipple s operation .
in addition , the presence of a shunt was evaluated in 17 of these patients , of whom seven did not have a shunt , such as a patent foramen ovale or arteriovenous malformation , including our two present patients .
there are no standard treatments for cerebral air embolisms that occur during or after an endoscopic procedure , and some previous reports   have shown that early hyperbaric oxygen therapy has a beneficial effect .
hyperbaric oxygenation therapy may reduce air bubble size , accelerate nitrogen reabsorption , and increase the oxygen content of arterial blood , potentially reducing the ischemia .
however , the delay to treatment application has been reported to range from 3 to 48 hours . among the five previously reported patients who underwent hyperbaric oxygen therapy , two , including our first case herein , showed full or partial neurologic recovery .
the remaining 15 patients received high fio2 therapy or conservative management without hyperbaric oxygen therapy .
of these , six patients died and nine patients survived with or without a neurologic deficit . in conclusion , we here report two cases of cerebral air embolism as a rare complication of therapeutic endoscopy .
although it is difficult to make this diagnosis because it can be confused with a sedative - related problem , our patients underwent appropriate early management and achieved good outcomes .
physicians should therefore be aware of the risk of cerebral air embolism during or after endoscopic procedures in patients who show cardiopulmonary instability and neurologic symptoms .
 cerebral air embolism is an extremely rare complication of endoscopic procedure and often life threatening . 
 we present two cases of cerebral infarction due to air embolization caused by an endoscopic intervention . 
 the first case occurred during esophageal balloon dilatation for the treatment of a stricture of an anastomosis site in a 59-year - old man and the second case occurred during endoscopic papillary balloon dilatation in a 69-year - old man who had distal common bile duct stones . 
 after the procedure , cardiopulmonary instability and altered mental status were observed in both patients , and cerebral air embolism was diagnosed in both cases . 
 hyperbaric oxygen therapy was started in the first case , and high fio2 therapy was applied in the second case . 
 although this complication is rare , patient outcomes can be improved if physicians are aware of this potential complication , and immediately begin proper management . 
INTRODUCTION
CASE REPORTS
Case 1
Case 2
DISCUSSION