Related Experiment Videos
Cerebral perfusion during major cardiac surgery in children
T Lundar1, H Lindberg, K F Lindegaard
1Department of Surgery, Rikshospitalet, Oslo, Norway.
Insights
During cardiac surgery, cerebral blood flow (CBF) monitoring in children showed reduced middle cerebral artery (MCA) velocities during cardiopulmonary bypass (CPB). This reduced flow met metabolic demands at low temperatures, indicating cerebral autoregulation was inactive.
Area of Science:
- Pediatric Cardiac Surgery
- Neuroscience
- Cardiovascular Physiology
Background:
- Major cardiac surgery requires cardiopulmonary bypass (CPB), necessitating careful monitoring of cerebral circulation.
- Understanding cerebral perfusion during CPB in pediatric patients is crucial for optimizing surgical outcomes.
Purpose of the Study:
- To investigate cerebral blood flow (CBF) dynamics in children during CPB using advanced monitoring techniques.
- To assess the adequacy of cerebral perfusion and the status of cerebral autoregulation at low temperatures during CPB.
Main Methods:
- Continuous monitoring of arterial blood pressure (BP), central venous pressure (CVP), cerebral electrical activity (cerebral function monitor - CFM), and middle cerebral artery (MCA) flow velocity (transcranial Doppler - TCD).
- Measurements were taken in six children undergoing major cardiac surgery with CPB at 20°C.
Main Results:
- Introduction of CPB caused rapid drops in BP and MCA velocities.
- During steady-state CPB at 20°C, MCA flow velocities were reduced (45%-105% of pre-bypass values) at cerebral perfusion pressures (CPP) of 14-26 mmHg.
- MCA flow velocities varied passively with CPP changes, indicating a lack of cerebral autoregulation.
Conclusions:
- Reduced cerebral perfusion during pediatric CPB at 20°C appears sufficient for metabolic demands at that temperature.
- Cerebral autoregulation is not operative under these conditions, unlike in adults.
- Transcranial Doppler is a valuable tool for optimizing CPB techniques for cerebral circulation.
Abstract:
Six children undergoing major cardiac surgery had extensive cerebral monitoring during cardiopulmonary bypass (CPB). The monitoring included continuous recording of arterial blood pressure (BP), central venous pressure (CVP), cerebral electrical activity by a cerebral function monitor (CFM), and middle cerebral artery (MCA) flow velocity by the transcranial pulsed Doppler (TCD) technique. Introduction of the precooled blood containing priming solution resulted in rapid fall in BP as well as MCA velocities in these children at the start of CPB. During steady-state CPB at 20 degrees C, MCA flow velocities were reduced in five of six children, range 45%-105% of pre-bypass value. These flow velocity values were recorded at cerebral perfusion pressures (CPP = BP - CVP) in the range of 14-26 mmHg. This reduced cerebral perfusion during steady-state CPB appears to be more than sufficient to meet the cerebral metabolic demands at the particular temperature. The reduced cerebral perfusion is in contrast to the enhanced perfusion found in adults during moderately hypothermic (28 degrees-30 degrees C) low-flow, low-pressure CPB previously reported. It was presumably due to the reduced temperature, reduced perfusion pressure, and less hemodilution. During periods of constant temperature, hematocrit, and partial pressure of carbon dioxide (PaCO2), MCA flow velocities varied passively with changes in CPP, demonstrating that cerebral autoregulation was not operative. Transcranial Doppler appears to be a suitable tool for investigating CPB techniques optimal with respect to cerebral circulation.