Thorac Cardiovasc Surg 2004; 52
DOI: 10.1055/s-2004-816807

Detection of gaseous microemboli during extracorporeal circulation

MK Fritz 1, K Klak 1, A Wiebalck 2, T Fleindl 1, D Buchwald 1, AM Laczkovics 1
  • 1Department of Cardiac and Thoracic Surgery
  • 2Department of Anaesthesiology, Intensive Care- and Pain Therapy, Bergmannsheil, Ruhr-University Bochum, Germany

Objectives: Air embolism is one of the most dangerous complications during extracorporeal circulation (ECC). Modern heart-lung-machines (HLM) have integrated safety features to avoid air embolisation. The aim of this pilot study was to identify possible sources of gaseous microemboli (GME) and to look for factors influencing number and volume of GMEs.

Material and Methods: 45 consecutive adults were included. All underwent cardiac operations using ECC. The microbubble activity in the ECC was recorded. GMEs were measured with a two-channel ultrasonic bubble counter. One sensor was placed before the oxygenator; a second either behind the oxygenator, behind the arterial filter or behind the dynamic bubble trap (DBT).

Results: As anticipated, the highest number of GMEs was found during mitral valve-, followed by aortic valve operations and CABG procedures (mean: 231.000, 175.000, 140.000). Whenever ultrasonic activity was detected, GMEs could be correlated with certain events. The most frequent reasons were cardiotomy suction (64% of all operations), air in the venous line (51%) and drug bolus administration (42%). Table: Mean activity In the open system, complete de-airing of the venous line decreased the volume of GMEs significantly (p=0,029), but not the number of GMEs. In the closed system, complete de-airing of the venous line results in both, a reduction of GMEs and of microbubble volume (p=0,001; p=0,008).

n

open system

n

closed system

p

before oxygenator

15

139.980

14

14.751

<0,019

after oxygenator

14

50.465

7

15.689

n.s.

after arterial filter

9

19.684

7

3959

n.s.

after DBT

7

9.888

1

4005

n.s.

Table: Mean activity

Conclusions: Microbubbles were generated during each operation using the HLM. Although the meaning of microbubbles for the neurological outcome is not known, surgeons should be familiar with both, the possible sources of GMEs and the techniques that can reduce the number of microbubbles generated in the extracorporeal circulation.