Precerebral Haemodynamics in Brain Tamponade - Part 2: Experimental studies

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Abstract
A reverberating flow pattern in the internal carotid artery (ICA) was demonstrated in patients with brain tamponade. This flow pattern has characteristic counterbalanced forward and backward components with no net flow in each cardiac cycle. Flow reverberations may be due to the Windkessel function of the cerebral arterial system in this condition of extremely high intracranial pressure. In an ideal Windkessel flow is proportional to the inlet pressure time derivative and the compliance is the constant factor. Conversely, the inlet pressure is proportional to flow integrated with respect to time. Comparisons of curve pattern obtained by such calculations and clinical records from patients show a remarkable similarity. Compliance apparently is the main determining factor when reverberating flow is present. The occurrence of a phase displacement of ICA with respect to simultaneous distal common carotid artery blood pressure supports this assumption. Temporary test occlusions of the ICA at the dural level did not produce reverberating flow in the proximal ICA. When reverberating flow is operative in brain tamponade the major effective compliance is probably confined to the intracranial compartment. Intracranial pressure pulsations persisted after the arrest of cerebral blood flow. ICA flow reverberations in brain tamponade apparently are dissipated into the brain vessels.