BACKGROUND: Transcranial Dopplersonography (TCD) has become an effective method for detection of embolic events during cardio-pulmonary bypass (CPB). To study possible causes of brain injury caused by the CPB-pump during infant cardiac surgery, embolic signals obtained from the MCA of the patient and from the arterial limb of a CPB-pump were studied.

PATIENTS & METHODS: The MCA and the arterial limb of the CPB-pump were monitored in 5 cases with 2 MHz multi-range probes (DWL, Multi Dop X-4): all events were recorded and analysed later on in sequence. Embolic events were discriminated from artefacts using high resolution FFT analysis differentiating amplitude and transit time. Multirange processing allowed the detection of embolic movement.

RESULTS: Table 19 showers of embolic signals were registrated during injection of drugs into the arterial limb of the pump indicating the presence of air-microbubbles. None of the these showers were detected by the bubble sensor of the CPB-pump.

Table 1
Full size table

CONCLUSION: Multirange processing allows to differentiate between real embolic events and artefacts. Common bubble sensors of CPB-pumps are not sensitive enough to detect showers of embolic events (air-bubbles), which might aggravate neurologic sequelae associated with CPB.

Supported by the Austrian Research Foundation (FWF-Nr-9342) & DWL Instruments, Germany