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Venous Cannula Obstruction by Embolus During Cardiopulmonary Bypass

Cardiothoracic Surgical Unit Royal Adelaide Hospital Adelaide, South Australia, Australia
For reprint information contact: Ashutosh A Hardikar, MCh Tel: 61 8 8222 5296 Fax: 61 8 8222 5962 email: a_hardikar{at}hotmail.com Cardiothoracic Surgical Unit, Royal Adelaide Hospital, Level 4, East Wing, North Terrace, Adelaide, SA 5000, Australia.

	Abstract

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During a routine mitral valve repair with coronary revascularization in a 65-year-old man, venous return was suddenly interrupted. The venous cannula was rapidly removed, revealing a large thrombus obstructing its lumen. Prompt recognition of the problem and replacement of the venous cannula resulted in uneventful recovery of the patient.

	Introduction

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The conduct of cardiopulmonary bypass (CPB) for the purpose of extracorporeal circulation during open heart surgery is usually uneventful. Sudden impairment of venous drainage from the right side of the heart is usually attributable to airlocks, malposition of a venous cannula, or kinks.¹ Rarely, pulmonary artery balloon catheters have been reported to obstruct the venous return.^2,3

	Case Report

TOP Abstract Introduction Case Report Discussion References

 
A 65-year-old man presented with moderate mitral regurgitation and two-vessel coronary artery disease. His preoperative echocardiogram had not shown any intracardiac clots or tumor. He had no systemic illness or malignancy and no history of any kind of thromboembolic episode. During surgery, monitoring lines consisted of a right radial artery line and a central venous line. Heparin in a dose of 3 mg•kg^–1 was given. The first activated clotting time reading was 426 seconds. Cannulation for institution of CPB included a 5.5-mm ascending aortic cannula and a 36/51 F two-stage venous return cannula (Cardio Research Lab, Sydney, NSW, Australia) inserted through the right atrial appendage. Our practice is to use standard CPB with moderate hypothermia and antegrade sanguineous cardioplegia. The mitral valve repair was performed first using a 31-mm Duran annuloplasty ring (model H 60814 S.N. D 46375; Medtronic Inc., Minneapolis, MN, USA). The valve was tested and found to be competent. Subsequently, reversed saphenous vein grafting was undertaken on the left anterior descending artery and the first diagonal artery. On completion of the first distal anastomosis, sudden distension of the right heart was noted, and the perfusionist informed us of severe sudden impairment of venous return. A quick check revealed no airlocks, kinks, or cannula malposition. A decision to change the venous cannula was taken and it was replaced within 2 minutes of noticing the problem. The first venous cannula was found to be obstructed with a 3.5 x 1.5 cm wide cylindrical thrombus. The thrombus was in one piece and laminated. The activated clotting time was rechecked and found to be 499 seconds. The second distal anastomosis and the proximal anastomoses were completed and the patient was weaned off CPB uneventfully. The right atrium was then palpated internally through the right atrial appendage. No evidence of any intraatrial lesion was detected. An echocardiogram was performed in the intensive care unit, which failed to show any intracardiac lesion. A Doppler study also failed to show any evidence of deep venous thrombosis. There was no evidence of pulmonary embolism or heparin-induced thrombocytopenia, even after repeated tests. Histopathology of the clot showed it to be an old organized clot without any kind of tumor. The patient was well at follow-up after 3 months.

	Discussion

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Reduced venous drainage is a common problem during CPB, often due to reduced venous pressure, obstruction, or excess resistance in the venous cannulae or venous lines.¹ On the other hand, a sudden reduction of venous return causing right heart distension is a catastrophic event that needs to be urgently corrected. Air locks are by far the most common cause of this problem. In cases such as this where the left atrium was opened with a two-stage venous cannula, any small opening into the right atrium could cause air to enter the venous circuit resulting in an air lock. However, there was no air in the venous tubing in this case. Kinking of the venous cannula can suddenly occlude venous return, more so when the heart or the cannula is being manipulated. In this case, grafting was being performed on the anterior aspect of the heart, not involving much displacement. Malpositioning of the cannula into the right ventricle or perforation of the inferior vena cava could be other rare causes. A few case reports mention similar catastrophes occurring due to a pulmonary artery balloon catheter that obstructed the venous cannula.^2,3 The treatment of the problem remains in replacing the venous cannula. A similar case has been reported in which the embolus was palpable as a soft spongy mass in the inferior vena cava; the problem was solved by cannulating both cavae separately.⁴

There is a possibility that intraoperative transesophageal echocardiography could have helped to suggest the diagnosis and would have also indicated any other intracardiac problems. However, the usefulness of transesophageal echocardiography is lost during CPB when the cardiac chambers are empty and clear definition of intracardiac structures is difficult.⁵ Probably, a deep venous thrombus from the legs or pelvis was dislodged after heparinization and somehow got into the basket of the two-stage venous cannula, nearly occluding it. We would like to highlight the importance of constant alertness and awareness of the problem as well as timely intervention. The patient's temperature was 28.4°C at the time of the event, which gave us a greater margin of safety than normothermia.

	Acknowledgments

 
We would like to thank our Chief Perfusionist, Nicholas James, for his help during the case and for providing the relevant details.

	References

TOP Abstract Introduction Case Report Discussion References

 

1. Hessel EA. Cardiopulmonary bypass: circuitry and cannulation techniques. In: Gravlee GP, Davis RF, Utley JR, editors. Cardiopulmonary bypass — principles and practice. Baltimore: Williams & Wilkins, 1993:63.

2. Gilbert TB, Scherlis ML, Fiocco M, Lowinger TA. Pulmonary artery catheter migration causing venous cannula obstruction during cardiopulmonary bypass. Anesthesiology 1995;82:596–7.[Medline]

3. Oyarzun JR, Donahoo JS, McCormick JR, Herman S. Venous cannula obstruction by Swan-Ganz catheter during cardiopulmonary bypass. Ann Thorac Surg 1996;62: 266–7.[Abstract/Free Full Text]

4. Lee ME. Near misses in cardiac surgery. Stoneham: Butterworth, 1992:57–8.

5. Davis RF, Dobbs JL, Casson H. Conduct and monitoring of cardiopulmonary bypass. In: Gravlee GP, Davis RF, Utley JR, editors. Cardiopulmonary bypass — principles and practice. Baltimore: Williams & Wilkins, 1993: 590–1.

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Ashutosh A Hardikar John Stubberfield Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hardikar, A. A Articles by Craddock, D. R Search for Related Content PubMed Articles by Hardikar, A. A Articles by Craddock, D. R Related Collections Extracorporeal circulation