Internal carotid artery back pressure to determine shunt requirement

Abstract

During the early experience with carotid endarterectomy, performed under local anesthesia, it was noted that there was a small percentage of patients who would develop a prompt neurologic deficit when the carotid artery was clamped in preparation for arteriotomy and endarterectomy. This occurred in approximately 10 % of patients, and the deficit could be promptly reversed with the placement of an internal shunt. It was generally assumed that this small but identifiable group of patients had inadequate collateral circulation in the distribution of the clamped artery. Therefore, collaterals were insufficient to provide for blood flow during the carotid endarterectomy. It was further assumed that to continue the operation without the use of an internal shunt would inevitably result in ischemic brain damage and probable cerebral infarction in the affected hemisphere. While it is easy to identify the patient who needs a shunt under local anesthesia, this was not so under general anesthesia. Since there was an increasing trend to perform this operation under general anesthesia, the surgeons at that time were left with little choice but to do all carotid endarterectomies with an internal shunt. A shunt was regarded as being an additional step in the operation. At best it was a cumbersome inconvenience. At worst it was a source of additional risk from arterial injury or from cerebral embolization with either air bubbles or atheromatous debris. Attempts were made to identify the small but finite percentage of patients who would require a shunt. Selective shunting could be used in those patients with inadequate collateral blood flow in order to protect them from ischemic brain damage during clamping.