he had a left ventricular ejection fraction of 42% and regional wall motion abnormalities compatible with multi - vessel territories .
coronary angiography findings revealed total occlusion at the proximal left anterior descending artery ( lad ) , 50 - 75% stenosis at the mid to distal left circumflex artery , and 90% stenosis at the mid right coronary artery ( rca ) .
cardiac surgery was performed through a median sternotomy , and the heart was displaced using a deep pericardial retraction suture , gauze swab , and tissue stabilizer . after confirming the lack of atheroma burden in the ascending aorta by epiaortic ultrasound examination , the left radial artery was connected to the ascending aorta . after completing the lad grafting using the left internal thoracic artery ,
the patient was in the trendelenburg position , and norepinephrine was infused at a dose of 0.15 g / kg / min . after stabilizer application , there was a temporary deterioration in the patient 's hemodynamic status , which was stabilized without the aid of incremental doses of norepinephrine dosage .
after opening the anastomotic site at the om branch , the surgeon informed us the patient was bleeding from the arteriotomy site despite placement of a proximal snare .
the co2 blower was more aggressively used to aid grafting at a flow rate of 3 - 5 l / min .
bleeding was replaced by colloid solution , and all hemodynamic variables were stable : systemic blood pressure 121/58 mmhg , heart rate 59 beats / min , pulmonary arterial pressure 24/11 mmhg , cardiac index 2.6 l / min / m and mixed venous oxygen saturation 82% . approximately 5 minutes after the commencement of grafting , the surgeon decided to insert an intracoronary shunt for better visualization .
suddenly , the patient 's systemic blood pressure decreased to 64/56 mmhg despite increasing the norepinephrine dose from 0.05 g / kg / min to 0.30 g / kg / min .
the pulmonary arterial pressure increased to 34/20 mmhg , and the mixed venous oxygen saturation decreased to 66% .
vasopressin 0.6 iu was quickly administered intravenously , and the transesophageal echocardiography ( tee ) revealed a massive gas floating at the orifice of the rca ( fig .
although the patient remained in normal sinus rhythm , complete heart block occurred within minutes , and ventricular pacing was commenced . over the next several minutes , ventricular fibrillation developed ; despite aggressive treatment , including defibrillation , epinephrine , and direct manual cardiac massage , adequate circulation could not be restored , and cardiac massage was continued . upon preparing for emergent conversion to cardiopulmonary bypass ( cpb ) , epinephrine
300 g was injected directly to the aortic root by the surgeon using a 26-gauge needle .
subsequently , manual cardiac massage was continued for several cycles , and spontaneous recovery of unspecified cardiac rhythm was observed .
then the patient 's systemic mean arterial pressure gradually rose from 38 to 103 mmhg , and recovery of normal sinus rhythm and contractile performance followed immediately .
the remaining grafts were performed successfully without conversion to cpb , and no sign of bleeding was observed at the puncture site in the aorta .
the patient had an unremarkable postoperative course without neurologic deficits and was discharged 10 days after the surgery .
despite using a proximal coronary snare , this method of hemostasis can be incomplete in the presence of severe atheroma or calcification , causing bleeding through the arteriotomy site .
cardiac displacement invariably causes hemodynamic deterioration , and when the diastolic systemic blood pressure decreases below the pressure generated by the co2 gas blower , gas may migrate in a retrograde fashion to the aortic root . even in the presence of a proximal snare
, the proximal coronary lumen may not be completely obstructed due to the presence of calcified atheroma , as evidenced by continued bleeding from the arteriotomy site after application of the snare . as the rca ostium is in the highest position of the sinus of valsalva
, gaseous materials would be prone to migrate into the rca , causing embolic infarction .
a minor gas embolism may pass unnoticed or be overcome with supportive measures to aid emboli clearance .
however , in the case of a massive embolism with the possible introduction of room air due to venturi effect , hemodynamic collapse can occur and may require aggressive treatment , such as cardiopulmonary resuscitation ( cpr ) with aspiration of the air by direct puncture of the aortic root .
it may even require emergent conversion to cpb , which is known to be associated with increased morbidity and mortality .
therefore , when bleeding from the arteriotomy site persists despite the use of a proximal snare or intracoronary shunt , anesthesiologists should be aware of the possibility of a gas embolism and advise the surgical team to stop or limit the use of the co2 blower .
when a gas embolism results in hemodynamic deterioration , supportive measures should be immediately undertaken to increase the coronary perfusion pressure and facilitate emboli clearance .
gas embolism should also be confirmed with tee , and a pacemaker should be at hand given that complete heart block due to atrioventricular nodal ischemia may occur in the case of an embolism involving the rca .
finally , in the case of failure of supportive measures such as drug administration to the venous side , direct aortic injection of the drugs can be attemped before initiating cpb . in coronary artery bypass graft surgery
, direct cardiac massage may not be aggressively and effectively performed due to the fear of disrupting the previously grafted conduits , limiting the drug delivery from the venous side to the systemic circulation .
prior to the 1960s , intracardiac injection of medications was used blindly or directly , but this approach was abandoned due to the devastating complication of lacerating the epicardial coronary arteries and cardiac tamponade .
however , direct injection to the aortic root following a sternotomy appears to be feasible and may be life - saving , as severe right ventricular dysfunction may limit systemic drug delivery injected through the venous side despite the performance of direct cardiac massage . in the current case , intra - aortic injection of epinephrine may have resulted in a more effective increase in the systemic vascular resistance , thereby increasing the coronary perfusion pressure and thus facilitating emboli clearance . in conclusion , in the rare case of a gas embolism occurring during opcab occurs , the potential for catastrophic results necessitates immediate and appropriate managements including supportive measures , needle aspiration of gas , and cpr with direct cardiac massage . in refractory cases , while considering emergent conversion to cpb , direct injection of drugs to the aortic root can be attempted before initiating cpb .
this may be a simple , relatively safe , and life - saving approach for the management of a gas embolism during opcab because a sternotomy has already been conducted .
 although compressed gas ( co2 ) blowers have been used safely to aid accurate grafting during off - pump coronary bypass surgery , hemodynamic collapse due to gas embolism into the right coronary artery may occur . 
 supportive measures to facilitate gas clearance by increasing the coronary perfusion pressure have been reported to be successful in restoring hemodynamic stability . however , right ventricular dysfunction and atrioventricular nodal ischemia may hinder effective systemic delivery of the vasoactive medications , even when performing resuscitative measures such as direct cardiac massage . 
 we herein report a case of cardiac arrest that was caused by a right coronary gas embolism and that could not be restored by cardiac resuscitation . 
 when supportive measures fail , direct aortic injection of epinephrine to increase the coronary perfusion pressure can be attempted before initiating cardiopulmonary bypass , and this approach may be life - saving in situations that limit systemic drug delivery from the venous side despite the performance of direct cardiac massage . 
Case Report
Discussion