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Cerebral haemodynamics during proximal aortic cross-clamping
P Aadahl1, O D Saether, R Stenseth
1Department of Anaesthesiology, Trondheim University Clinic, Norway.
Insights
Thoracic aortic cross-clamping significantly increases cerebral blood flow and intracranial pressure in pigs. These effects, including enhanced internal carotid artery flow, reverse upon clamp release, suggesting protective mechanisms for the brain.
Area of Science:
- Cardiovascular Physiology
- Cerebrovascular Regulation
- Surgical Hemodynamics
Background:
- Understanding cerebral blood flow (CBF) dynamics during aortic procedures is crucial for preventing neurological complications.
- Thoracic aortic cross-clamping (XC) can alter systemic and cerebral hemodynamics.
- The impact of aortic XC on cerebral microcirculation and intracranial pressure (ICP) requires detailed investigation.
Purpose of the Study:
- To investigate the effects of thoracic aortic cross-clamping (XC) on cerebral blood flow, microcirculation, and intracranial pressure (ICP) in a porcine model.
- To analyze hemodynamic changes in the internal carotid artery (ICA) and middle cerebral artery (MCA) during aortic XC.
- To evaluate the immediate post-XC recovery of cerebral parameters.
Main Methods:
- Utilized electromagnetic flowmetry for ICA blood flow measurement.
- Employed laser Doppler technique to assess cerebral microcirculation.
- Measured ICP using a fiber optic pressure monitoring catheter.
- Recorded MCA blood flow velocity with transcranial Doppler.
- Determined cardiac output via thermodilution.
- Performed aortic XC distal to the left subclavian artery for 30 minutes in pigs.
Main Results:
- Aortic XC led to a significant 191% increase in ICA blood flow (p<0.05).
- Mean and maximal MCA blood flow velocity increased by 125% (p<0.01).
- ICP rose by 163% (p<0.05), and cerebral flux increased by 23% (p<0.05).
- All measured parameters returned to baseline levels within minutes after XC release.
Conclusions:
- Thoracic aortic XC induces a substantial increase in cerebral blood flow and ICP in pigs, correlated with increased cardiac output.
- These findings support the hypothesis that enhanced blood flow to the anterior spinal artery may mitigate neurological damage after proximal aortic XC.
- The observed hemodynamic responses highlight the brain's compensatory mechanisms during aortic manipulation.
Abstract:
This study was carried out to examine cerebral blood flow, including the microcirculation and intracranial pressure during cross-clamping (XC) of the thoracic aorta in pigs. Blood flow in the internal carotid artery was measured by electromagnetic flowmetry. Cerebral microcirculation was studied by the laser Doppler technique, and intracranial pressure measured by applying a fibre optic pressure monitoring catheter in the same craniotomy. Maximal and mean blood flow velocity of the middle cerebral artery was recorded using a transcranial Doppler and cardiac output measured by thermodilution. The thoracic aorta was cross-clamped distal to the left subclavian artery for 30 min. During aortic XC the internal carotid artery blood flow increased 191% (p less than 0.05). Simultaneously mean and maximal blood flow velocity of the middle cerebral artery both increased 125% (p less than 0.01). Intracranial pressure increased 163% (p less than 0.05), and there was an increase in cerebral flux of 23% (p less than 0.05). Within the first minutes following the release of XC, all values decreased to preocclusive values. In conclusion, we observed a significant increase in cerebral blood flow during XC of the thoracic aorta. This is in accordance with the finding of a simultaneous increase in cardiac output. These haemodynamic changes support the theory that an increased blood flow via the proximal feeding system to the anterior spinal artery might be important in avoiding neurological sequelae following proximal aortic XC.
