Year : 2014  |  Volume : 17  |  Issue : 3  |  Page : 229--231

"Air embolism during fontan operation"


Madan Mohan Maddali1, Eapen Thomas2, Mohd M Malik1,  
1 Department of Anaesthesia, Royal Hospital, Muscat, Oman
2 Department of Paediatric Cardiology, Royal Hospital, Muscat, Oman

Correspondence Address:
Madan Mohan Maddali
Department of Anaesthesia, Royal Hospital, P.O. Box 1331, P.C.: 111, Seeb, Muscat
Oman

Abstract

In patients with a right to left intracardiac shunt, air embolism results in an obligatory systemic embolization. Nonembolization of entrained air is described in a child with a single ventricle physiology who had earlier undergone bidirectional Glenn shunt construction and Damus-Kaye-Stansel anastomosis. The air entrainment was detected by intra-operative transesophageal echocardiography. The combined effect of a «DQ»diving bell«DQ» phenomenon and mild aortic valve regurgitation are suggested as the reasons for the confinement of air into the ventricle preventing catastrophic systemic embolization.



How to cite this article:
Maddali MM, Thomas E, Malik MM. "Air embolism during fontan operation".Ann Card Anaesth 2014;17:229-231


How to cite this URL:
Maddali MM, Thomas E, Malik MM. "Air embolism during fontan operation". Ann Card Anaesth [serial online] 2014 [cited 2020 Feb 19 ];17:229-231
Available from: http://www.annals.in/text.asp?2014/17/3/229/135874


Full Text

 INTRODUCTION



In patients with single ventricle physiology, air entry into the heart chambers would result in obligatory systemic embolization. This report draws attention to the importance of intra-operative transesophageal echocardiography (TEE) in the early detection of air entrainment in a child undergoing Fontan operation with a prior bidirectional Glenn (BDG) shunt and a Damus-Kaye-Stansel (DKS) connection. As the child did not exhibit any postoperative neurological consequences, a speculation is made that in addition to the maneuvers that were adopted to manage the inadvertent air entry, a "diving bell" phenomenon and a mildly regurgitant aortic valve helped confinement of the air in the heart chambers and prevented massive systemic embolization.

 CASE REPORTS



An 8-year-old boy with a double inlet left ventricle, hypoplastic right ventricle, transposition of great arteries and coarctation of aorta underwent coarctation repair and pulmonary artery banding at 7 days of age. The child underwent a BDG shunt and DKS connection at 4 years of age. During this admission, the child was scheduled for an extracardiac Fontan.

General anesthesia was administered uneventfully. Intra-operative monitoring included electrocardiography, pulse oximetry (SpO 2 ), end tidal carbon dioxide (EtCO 2 ), arterial (right radial), central venous (left femoral vein), and Glenn pressures (right internal jugular vein). In addition, a TEE probe (Philips iE33 Ultrasound System, KPI Ultrasound, CA 92507 with S7-3t Pediatric TEE transducer) was inserted for intra-operative monitoring.

The right femoral vessels were exposed before sternotomy for the eventuality of a femoro-femoral bypass. Prior to sternotomy the DKS connection with a mildly regurgitant aortic valve was assessed and no air was detected in the cardiac chambers. During sternotomy, which was being performed with scissors, a large amount of air was detected in the cardiac chambers by TEE. The child developed hypotension and bradycardia [Table 1] with ischemic changes on the electrocardiogram. The surgeon was informed of air entrainment and a deep Trendelenburg position was achieved. Immediately, the surgical site was packed with saline soaked dressing and skin was approximated to prevent further entrainment of air. Hemodynamic parameters were stabilized rapidly with adrenaline infusion. The child was administered 100% oxygen and fluids were administered through a lower limb vein for elevating the cardiac filling pressures and maintaining the cardiac output. Femoro-femoral bypass was instituted in about 5 min and deep hypothermic circulatory arrest was planned. At a nasopharyngeal temperature of 23°C the heart fibrillated and it was decided to arrest the circulation. For cerebral protection the head was packed in ice. As per our institutional protocol, methylprednisolone (30 mg/kg), thiopentone (10 mg/kg), and furosemide (1 mg/kg) were administered into the cardiopulmonary bypass (CPB) circuit prior to circulatory arrest. Sternotomy was completed and a small tear in right atrial wall was closed [Figure 1]. Innominate vein was cannulated and complete CPB was established after 6 min of circulatory arrest. While rewarming to normothermia the extracardiac Fontan procedure with a conduit was completed. The child was separated from CPB with milrinone infusion (0.5 μ/kg/min). The total CPB and aortic clamp times were 180 and 40 min, respectively. After completion of the Fontan surgery, the child was transferred to intensive care unit and was ventilated electively. As the child was hemodynamically stable and neurologically intact, trachea was extubated after 6 h of mechanical ventilation. The child remained stable and was discharged home on the 10 th postoperative day after a complete neurological assessment of mental status, motor function, coordination, reflexes, and sensory system and lastly cranial nerves, and all the neurological examinations were found normal.{Figure 1}{Table 1}

 DISCUSSION



The DKS operation is performed to relieve systemic ventricular outflow tract obstruction in a functionally univentricular heart. The procedure involves division of the main pulmonary artery and its connection to the ascending aorta. [1] The pulmonary circulation is re-established by a BDG shunt followed by a completion Fontan procedure in suitable cases as was the case in this child. During BDG shunt, the superior vena cava (SVC) is anastomosed to the right pulmonary artery with the oversewing of the proximal SVC such that the venous blood from the head and upper limbs will pass directly to the lungs, bypassing the ventricle. [2] During Fontan procedure the inferior venal caval return is also directed to the pulmonary artery making it a total cavopulmonary shunt. The massive air entry into the chambers of the heart occurred when the child was taken up for this final procedure. The incidence of massive air embolism in adult cardiac bypass procedures is between 0.003% and 0.007% with 50% having adverse outcomes. [3] Children are less prone to venous air embolism than adults, but they are more susceptible to the adverse effects of embolization, especially when intracardiac right-to-left shunt exists. [4] The common causes of systemic air embolism during cardiac surgery include air entrainment through venous infusion lines finding its way into the systemic circulation across intracardiac communications, inadvertent injury of pulmonary vein and/or left atrium, during cannulation of pulmonary vein for venting of the left heart, during sternotomy in cardiac redo operations, and inadvertent pumping of air from extracorporeal circuit during CPB, etc. It is suggested that air embolism during sternotomy occurs through the sternal veins splayed open; concomitant decrease in the central venous pressures due to mechanical deflation of the lungs and sucking effect of ventricular relaxation favors air entrainment into the chambers of the heart. [4] Direct injury to any low pressure major vessel or cardiac chambers also favors rapid and massive air entrainment, and air entrainment in the present patient occurred through the opening in the common atrium. Normally, the air entrained into the venous system is sucked into the right ventricle during its relaxation and ejected into the pulmonary artery during ventricular systole. The cardiac anatomy of this child dictated that any air entrained in the right atrium would result in obligatory systemic embolization. However, despite confirmed presence of the massive amount of air in the cardiac chambers as detected by TEE, the child escaped any neurological sequelae.

The entrained air is expected to deposit in the apical area of the single ventricle in the steep Trendelenburg position. It should have been ejected into the systemic circulation during ventricular systole. Why the air did not embolize into the systemic circulation? We believe, possibly "diving bell" phenomenon prevented systemic air embolization. The "diving bell" phenomenon describes: When the open end of a cup-shaped or bell-shaped chamber filled with air is immersed in liquid, the upward pressure of the liquid compress and entrap the air at the apex of the chamber. During steep Trendlenberg position, the ventricular apex of the heart became the highest point of the heart and perhaps, due to "diving bell" phenomenon, the air remained entrapped at the apex of the heart without massive systemic dispersion. Moreover, the development of myocardial ischemia caused hypotension, myocardial dysfunction and ineffective systolic ejections, which seemingly could not eject out the entrapped air. Further, the air-bubbles that were dislodged, circulated back into the ventricle through the mildly regurgitant aortic valve [Figure 2]. The large DKS anastomosis may also have helped keeping air in the root and funneled it into the right coronary artery as the air was detected in the right coronary artery by TEE.{Figure 2}

Yeh et al., used retrograde cerebral perfusion, brief hypothermic circulatory arrest and advanced neurological monitoring for the management of cerebral air embolism during the creation of a fenestration after a Fontan procedure. [5] In the present patient, the initiation of femoro-femoral CPB took about 5 min and considerable time elapsed by the time innominate vein was cannulated after completion of sternotomy. As we could not detect further air entrainment once the surgical site was packed, the role of retrograde cerebral perfusion was considered to be of limited value and was omitted.

 CONCLUSION



In patients with large right to left intracardiac shunts, any air entrained in the venous system would result in obligatory systemic embolization. Intra-operative TEE is a valuable tool in the early detection of air embolism during cardiac surgery. In an unfortunate event of air embolism during redo sternotomy, institution of femoro-femoral CPB with the maintenance of good perfusion pressures, and steep Trendelenburg position could trap the air in the ventricles and help preventing systemic air embolization.

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