Cerebral blood flow during cardiopulmonary bypass in man: effect of arterial filtration
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Insights
Cardiac surgery alters cerebral blood flow, causing hyperperfusion during extracorporeal circulation. Arterial filters reduce blood flow but do not prevent this effect or impact cerebral autoregulation.
Area of Science:
- Neurology
- Cardiovascular Surgery
- Medical Engineering
Background:
- Cardiac surgery often involves extracorporeal circulation, which can affect cerebral blood flow.
- Maintaining adequate cerebral perfusion is critical during and after cardiac procedures.
Purpose of the Study:
- To investigate the impact of arterial filtration on cerebral blood flow during cardiac surgery.
- To assess changes in cerebral blood flow and autoregulation with and without arterial filters.
Main Methods:
- Cerebral blood flow was measured using xenon-133 in 39 patients undergoing cardiac surgery.
- Patients were divided into groups with 20-micron, 40-micron arterial filters, or no arterial filtration.
- Coronary suction lines had a 40-micron filter in all patients.
Main Results:
- Significant changes in cerebral blood flow were observed during extracorporeal circulation (p < 0.0001).
- Cerebral blood flow increased significantly during hypothermic extracorporeal circulation and rewarming, indicating hyperperfusion.
- Arterial filters reduced cerebral blood flow but did not abolish hyperaemia; cerebral autoregulation remained unaffected.
Conclusions:
- Extracorporeal circulation during cardiac surgery leads to significant cerebral hyperperfusion.
- Arterial filtration can reduce but not eliminate this hyperperfusion.
- Cerebral autoregulation is preserved despite the use of arterial filters and observed hyperperfusion.
Abstract:
Cerebral blood flow was recorded in 39 patients undergoing cardiac surgery by intraarterial injection of xenon 133. There were three subgroups of patients: 10 patients had a 20 micron arterial filter (Johnson) and 11 a 40 micron filter (Pall), and 18 had no arterial filtration. All patients had a 40 micron (Pall) filter in the coronary suction line. Significant changes in cerebral blood flow occurred during extracorporeal circulation (p less than 0.0001). For all patients cerebral blood flow increased from a resting prebypass level of 30 to 46 and 57 ml/100 g a minute during initial and stable hypothermic extracorporeal circulation respectively. Both measurements were obtained at 26 degrees C and the recordings were made on average 12 and 55 minutes after the extracorporeal circulation was started. During rewarming cerebral blood flow increased to 64, 53, 41, and 36 ml/g a minute at 31 degrees, 33 degrees, 35 degrees, and 37 degrees C respectively, and when measured four and 16 minutes on average after bypass it was 44 and 41 ml/100 g a minute. This general brain hyperperfusion was noticed in all patients with a high enough mean blood pressure to produce hyperaemia. Interposing 20 and 40 micron arterial filters reduced cerebral blood flow but did not prevent this hyperaemia. The cerebral autoregulation, which maintains a constant cerebral blood flow within wide limits of perfusion pressures, was not affected by arterial filtration. The lower limit of blood pressure at which a further reduction in blood pressure was followed by a reduction in cerebral blood flow was around 60 mm Hg in all three groups.
