Relation between middle cerebral artery blood flow velocity and stump pressure during carotid endarterectomy.

Abstract

Background and Purpose: Many patient monitoring techniques have been used for detecting cerebral hypoperfusion during carotid endarterectomy. We compared middle cerebral artery blood flow velocities with carotid artery stump pressures to evaluate the indications for common carotid artery cross-clamp shunting and the probable hemodynamic causes of cerebrovascular complications.Methods: Blood flow velocities were monitored with transcranial Doppler ultrasound and carotid stump pressures were measured at the time of common carotid artery cross-clamping during 97 carotid endarterectomy procedures. Stump pressures measured with the gauge zero reference at the common carotid artery level were correlated with the percentage change of velocities.Results: Middle cerebral artery blood flow velocities usually decreased upon common carotid artery cross-clamping, depending on collateral availability and the autoregulation response. The best fit of the data was to an exponential function concave to the pressure axis, with velocity as a percentage of the pre-cross-clamp value reaching zero at 15 mm Hg stump pressure (r=0.85 andp<0.001).Conclusions: There is a less critical margin of error with percentage middle cerebral artery blood flow velocity decreases than with stump pressure measurements. This relation establishes changes in middle cerebral artery blood flow velocities as a reliable parameter for judging the effects of carotid crossclamping on cerebral blood flow and providing an excellent indicator as to the necessity for shunting.

Cerebral haemodynamics in internal carotid artery trial occlusion

“…In the course of the occlusion, the VMCA gradually increased, the PtMCA continued to decline, while the U~m MCA remained stable. Spencer et al [21] interpreted a similar initial drop in ipsilateral VMCA during common carotid artery cross-clamping during carotid endarterectomy to represent the collateral availability, and the subsequent increase in VMCA to reflect the autoregulation response. Accordingly, the cerebrovascular resistance decreased progressively during the clamping.…”

“…The mere anatomical assessment of the configuration of the circle of Willis is, however, inadequate in defining this collateral capacity [3,11]. Transcranial Doppler ultrasonography (TCD) allows a non-invasive continuous beat by beat haemodynamic analysis of the collateral function [8,21] including evaluation of the individual haemodynamic status [20]. With TCD, the threshold of tolerance of ICA occlusion has been suggested to be a decrease in ipsilateral middle cerebral artery (MCA) blood velocity to 60% of pre-occlusion values [12,14,18].…”

Assessment: Transcranial Doppler ultrasonography: [RETIRED]

“…In addition, flow velocity changes during cross-clamping correlate with stump pressure measurements. 54 Reports [54][55][56] Hemodynamic changes following CEA include an improvement in MCA, ACA, and ophthalmic flow velocities, resolution of side-to-side MCA flow velocity asymmetries, and restoration of cerebrovascular vasoreactivity to CO 2 or acetazolamide challenge. 40,57,58 Microembolic signals most commonly occur during the dissection phase intraoperatively, during shunting and unclamping, during wound closure, and in the first few hours postoperatively.…”

Análise do comportamento do hemometabolismo cerebral durante endarterectomia carotídea com pinçamento transitório

“…A referida pressão é um monitor freqüentemente utilizado como indicador da qualidade da perfusão cerebral durante o pinçamento carotídeo, podendo, para alguns cirurgiões vasculares e anestesiologistas, ser um fator valorizado para indicação de colocação de shunt carotídeo intra-operatório. Entretanto, a literatura [18][19][20] apresenta controvérsias em relação a utilidade desse tipo de monitor, avaliado de maneira isolada, como um método de aferição da qualidade da perfusão cerebral durante esse tipo de procedimento cirúrgico. Os citados trabalhos justificam essa ponderação através dos seguintes pontos:…”

“…Brain perfusion pressure is a monitor often used as indicator of brain perfusion quality during carotid clamping and, according to some vascular surgeons and anesthesiologists, it may be taken into consideration for the indication of intraoperative carotid shunt. However, the literature [18][19][20] is controversial about its usefulness as a sole method to assess the quality of brain perfusion during this type of surgical procedure, based on the following assumptions:…”