Echocardiographic Surveillance of Patients Undergoing Scheduled Endoscopic Retrograde Cholangiopancreatography for the Presence of Intracardiac Air Embolus

Endoscopic Retrograde Cholangiopancreatography (ERCP) is commonly used in the diagnosis and treatment of biliary and pancreatic disease. There are case reports presented in the literature demonstrating adverse and often fatal events following air embolization associated with the performance of ERCP. The frequency of air embolus is extremely rare with the exact incidence unknown. In recent years the utilization of echocardiography to evaluate individuals with hemodynamic instability has led to the discovery of intracardiac air embolus seen in those individuals that demonstrated changes in either hemodynamic parameters or capnography values. There exists proposed mechanisms for the translocation of air from the foregut to the systemic venous circulation but not one of these mechanisms has yet been validated. Some proposed mechanisms include either through intrahepatic mechanisms where air crosses from the biliary tract to hepatic venules or potentially from the foregut into the portal vein and through shunt vessels into systemic venous circulation.

The exact frequency of air embolus is likely higher than the incidence of fatal or near-fatal complications reported in the literature. Individuals that had the best outcomes were usually intubated and had capnography to demonstrate a change suggestive of air embolus prior to significant hemodynamic changes.1 As this phenomenon has not previously been well described, it is possible that other patients suffer significant air embolus with myocardial or cerebral ischemic sequelae that were not recognized because echocardiography was not used as an early tool for evaluation of hemodynamically unstable patients. It is also possible that there are a number of patients that may suffer a venous air embolus from ERCP that is sub-clinical and therefore not causing enough change in cardiac function to alter either hemodynamic parameters or capnography values. The literature suggests that if a patient does not awake following ERCP, that imaging modalities, such as echocardiography be employed for evaluation.1 Understanding the frequency of this problem or which subgroups are at risk can further aid in the diagnosis and treatment of this complication.

Transthoracic echocardiography is a highly sensitive imaging modality and if adequate imaging windows can be obtained will demonstrate the presence of intracardiac air. The risk of performing the study on the patient is zero to very low. The potential risk of inaccurate interpretation should be avoided by the use of trained individuals in the acquisition and interpretation of transthoracic echocardiographic images.

The purpose of this study is to 1) identify individuals scheduled to undergo elective ERCP as part of their plan-of-care and perform transthoracic echocardiography for surveillance of intracardiac air embolus 2) record aspects of their past medical history that may potentially contribute to increased risk of systemic venous air embolus. This evaluation has not been presented in the literature and the primary end-point of this study would be to determine the frequency at which venous air embolus associated with ERCP occurs.

All individuals that meet inclusion criteria will be approached and consented in the pre-operative area prior to the planned procedure (ERCP). Their past medical history will be reviewed with the patient and special attention placed on particular co-morbid conditions that might be related to this phenomenon including but not limited to: portal hypertension, cirrhosis, portal vein thrombosis, and recent liver biopsy. The patient will then proceed to the procedure room as planned and while the patient is placed in the left lateral decubitus position and induced under anesthesia. An echocardiography-trained anesthesiologist will perform a transthoracic echocardiogram (TTE) concurrently while the gastroenterologist is performing the ERCP. We plan on conducting serial images at least every ten to fifteen minutes throughout the ERCP and more often as needed. At the conclusion of the procedure (ERCP) if there are no significant findings on TTE the patient will be returned to the supine position and taken to the recovery room. The written record of the TTE will then be entered into the study database within a separate research chart. In the event that the TTE shows the presence of intracardiac air embolus during the procedure the member of the study group performing the TTE will notify the endoscopist and anesthesia provider of the findings if the findings are significant enough to require a change in the patient's medical care. Reference to the algorithm will be made in each case and be available online if needed. Unless a moderate to severe embolic event occurs, the findings will not be communicated to the gastroenterologist so that he is blinded to the result maintained in the research chart. The purpose of this is to keep clinically insignificant emboli from being reported in the patient's medical record.