Original Article

ECC Sources of Gaseous Microemboli

Surgical Clinic A, University Hosp1tal, Research Department, Zürich, Switzerland

^* Direct communications to: D. Demierre, Chirurgische Klinik A, Forschungsabteilung FL 42, Universitätsspital Zürich, Rämistrasse 100, CH-8091 Zürich, Switzerland

Abstract

We have tried to locate sources of gaseous microemboli during the ECC using a newly developed ultrasonic detector. The detector was calibrated with filters of known pore size and the recorder setting was kept constant at all times. We studied, at the oxygenator, the effect of low and high fill volume, refilling with or without air into the cardiotomy line, mechanical disturbance, rewarming and high p0₂. Arterial line filters were examined for their capacity to retain microemboli.

All bubble oxygenators tested released microemboli, especially at low fill volume when operated at high blood flows. Any mechanical interference (shock) either to the oxygenator or the filter will cause massive release of microemboli. This was also seen during fast rewarming of the blood, fast refilling of the oxygenator and high p0₂. Slow rewarming of the blood as well as slow refilling of the oxygenator, even with air in the cardiotomy line, did not cause any excessive microemboli. All filters tested retained microemboli to a great extent. Membrane oxygenators demonstrated no measurable microbubble formation at normal flows or with mechanical interference (shock) to the unit.

Microemboli detection during ECC has helped to trace various sources of gaseous microemboli which could be avoided using better perfusion techniques. Arterial line filters do reduce the amount and the size of gaseous microemboli during ECC.