Echo Detection of Endoscopic Retrograde Cholangiopancreatography (ERCP) 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.

One of the key components of this evaluation is determining whether the presence of an air
embolus has occurred and if so, has it had a negative effect on the function of the
subject's cardiovascular system. Our proposed evaluation of the myocardium using
transthoracic echocardiography includes evaluation of the left ventricle, right ventricle
and pulmonary artery pressures. In the event there is hemodynamic instability as a result of
impaired function of the right or left ventricle, an evaluation including measurements of
the following parameters will assist in determination of the problem:

1. Right ventricular function, specifically tricuspid annular plane systolic excursion
(TAPSE and the presence of hemodynamic changes.

2. Left ventricular function, specifically diastolic function, systolic function and
myocardial performance index.

3. Pulmonary artery systolic pressure, via evaluation of the tricuspid regurgitant jet
maximum velocity using the modified Bernoulli equation.

4. Presence of a new right-to-left intracardiac shunt or bowing of the intraatrial septum
from right-to-left indicating a new increase in the right atrial pressure.

5. Significant changes in hemodynamic status that would indicate that the subject does not
have effective filling and ejection of the left ventricle to support a perfusing blood
pressure. This may manifest as hypotension and/or tachyarrhythmias on standard
intraoperative monitoring.

As this protocol evaluates the frequency and degree of air embolization into the systemic
venous system during the performance of endoscopic retrograde cholangiopancreatography
(ERCP), the following four subgroups have been identified to help define the identification
and treatment of subjects enrolled into IRB 238-11. Each category has a) criteria for the
visual quantification of the air seen and b) the cardiac function and hemodynamic changes
seen and finally c) the planned intervention if needed:

1. No air embolism:

1. No visualized air emboli during the procedure.

2. Subjects have no hemodynamic or myocardial changes attributable to the occurrence
of venous air embolus.

3. No changes would be made to the standard care of this research subject as a result
of the absence of findings. Findings will be entered into the research chart.

2. Small air embolism:

1. A small, but identifiable quantity of air visualized that does not form a large
collection and does not obscure visualization of the far-field.

2. Subjects have no changes in myocardial function and maintenance of hemodynamics.

3. The subject would then undergo follow-up evaluation by a member of the study group
at the conclusion of their normal post-op recovery period. No additional time
would be required for evaluation and documentation of hemodynamic stability and
follow-up echocardiography findings would be recorded in the research chart.

3. Moderate air embolism :

1. Identifiable intracardiac air within the heart that obscures the far-field due to
its size but does not cause a sharp demarcation at the blood/gas interface.

2. Subjects have documented impairment of myocardial function and/or hemodynamics
compared to baseline but do not require emergency resuscitation to correct.

3. The subject would remain in the left lateral decubitus ("safe position" for
individuals with suspected or confirmed venous air embolism) for four hours.
Laboratory tests including cardiac enzymes may be obtained and a member of the
study team will re-evaluate with transthoracic echocardiography. If baseline
function and hemodynamics return, the subject concludes their recovery period as
per normal circumstance for ERCP. In the event the subject has persistent
intracardiac air, impaired myocardial function or hemodynamic instability, it
would be recommended that the subject stay for observation with telemetry
monitoring and further evaluation as needed.

4. Large air embolism:

1. Identifiable intracardiac air which collects into a large enough bubble to cause
sharp demarcation at the blood/gas interface and obscures the far-field.

2. Left and/or right ventricular failure with hemodynamic collapse.

3. The subject would require emergency resuscitation and ACLS protocol in addition to
placement of invasive monitors for evaluation. Attempts to extract intracardiac
air using central venous catheter will be made and as needed intubation with
transfer to the ICU for further monitoring. Consultation for hyperbaric oxygen
therapy would be pursued and all measures would be taken to recover hemodynamic
function.

Inclusion Criteria:

- Subject is undergoing ERCP as part of their medical care

- Subject will be of age 19 or older

Exclusion Criteria:

- Subject positioning for the ERCP is prone, thereby inhibiting the performance of the
TTE

- Subject intolerance of the pressure of the TTE probe

- Subject body habitus interferes with obtaining adequate images to assess for
intra-cardiac air