Internal carotid artery pressures. A guide for use of shunt during carotid repair

Asymptomatic carotid artery stenosis

Severe asymptomatic carotid stenosis is associated with a stroke risk of approximately 2% per annum. Aggressive management of risk factors is recommended, including cessation of smoking, and treatment of hypertension, diabetes, and hypercholesterolemia. Patients should be treated with antiplatelet agents. Carotid endarterectomy (CEA) in patients with greater than or equal to 60% stenosis reduces the risk of stroke by approximately 1% per annum overall. The benefit is greatest for men and younger patients. There may be no benefit for women or for older patients. Carotid angioplasty and stenting is not recommended as an alternative to CEA until there is clinical trial evidence of efficacy in asymptomatic stenosis, except in some patients with technical contraindications to CEA. There is no evidence that patients with asymptomatic severe carotid stenosis should undergo carotid revascularization prior to other surgical procedures, including coronary bypass surgery.

Carotid stump pressure, stump pulse, and retrograde flow

In order to obtain a more comprehensive intraoperative hemodynamic profile and to predict hypoperfusion during carotid endarterectomy, stump pressure, stump pulse, and retrograde internal carotid flow were measured in 261 patients. Our results show a significant correlation between stump pressure and retrograde flow (p < 0.001), stump pressure and the presence of a stump pulse (p < 0.001), and retrograde flow and the presence of a stump pulse (p < 0.001). We also demonstrated a significant correlation between stump pressure (lower), retrograde flow (less), and the absence of a stump pulse in patients with contralateral carotid artery occlusion. There was no correlation between the indication for carotid endarterectomy and any hemodynamic measurement. The triad of stump pulse, stump pressure, and retrograde flow accurately reflects collateral blood flow when the carotid is cross-clamped. These determinations can be obtained at low cost and are easily and rapidly performed. A protocol for selective shunting in patients undergoing carotid endarterectomy with general anesthesia is suggested.

Perioperative stroke. Part I: General surgery, carotid artery disease, and carotid endarterectomy

Although stroke, defined as a focal neurological deficit lasting more than 24 hr, is uncommon in the perioperative period, its associated mortality and long-term disability are high. No large-scale data are available to identify the importance of recognized risk factors for stroke in the perioperative period. A review of the literature shows that the incidence and mechanism of its occurrence are influenced by the presence of cardiovascular disease and the type of surgery. The most common cause of perioperative stroke is embolism. In non-cardiac surgery, the incidence of perioperative stroke is higher among the elderly. Properly administered, controlled hypotension is associated with minimal risk of stroke. Cerebral vasospasm may be the cause of focal cerebral ischaemia in eclamptic patients, and the aggressive treatment of hypertension may exacerbate the neurological damage. The risk of stroke associated with carotid endarterectomy is closely related to the preoperative neurological presentation, and the experience of the surgical/anaesthetic team. Symptomatic cerebrovascular disease, acute stroke, asymptomatic carotid lesions, preoperative assessment of risk, local and general anaesthesia, cerebral protection and monitoring during carotid endarterectomy are discussed with reference to reducing the risk of perioperative stroke. Adequate monitoring and protection have minimized the risk of ischaemia from carotid clamping, and the major mechanism of stroke is embolization.

Carotid artery stump pressure: how reliable is it in predicting the need for a shunt?

Carotid artery stump pressure was measured in 84 cases of carotid endarterectomy. The operations were performed in 71 patients over a period of five years. An altered neurological status during temporary occlusion of the carotid artery, assessed with the patient under local anesthesia, was the sole criterion for shunt placement. Stump pressure (SP) was significantly higher in the 69 unshunted cases (mean of 53.3 mmHg) than the 15 shunted cases (mean of 34.2 mmHg). Shunt was required in two of 41 cases (5%) with SP of greater than 50 mmHg, eight of 36 cases (22%) with SP of 25-50 mmHg, five of seven cases (71%) with SP of less than 25 mmHg. The clinical presentation, including history of prior stroke, and the presence of contralateral disease (including complete carotid occlusion), did not influence the need for a shunt. In this series, carotid artery stump pressure has greater predictive value for shunt requirement when it is greater than 50 mmHg or less than 25 mmHg. However, monitoring the neurological status of the patient in the awake state is still the most reliable method of determining shunt requirement. In our experience, this is associated with minimal morbidity and no mortality.

Local anaesthesia in carotid surgery. A prospective study of 111 endarterectomies in 100 patients

A prospective study was carried out on 100 patients consecutively undergoing carotid endarterectomy in local anaesthesia, in order to evaluate the usefulness of clinical signs in awake patients for monitoring of cerebral function and to determine the need for internal shunt in carotid surgery. The indications for operations were transient ischemic attacks in 67 patients and major or minor stroke in 24 (16 with persistent neurologic deficit). In nine asymptomatic patients the endarterectomy was prophylactic, following detection of bruit and angiographic stenosis. Bilateral stenosis was present in 47 patients, including 13 with total occlusion of the contralateral vessel, and 60 patients had significant vertebral artery stenosis. The carotid artery was first tentatively occluded and, if this was well tolerated for 5 min, endarterectomy was done without an internal shunt. Neurologic deficit signs during the trial occlusion necessitated such shunt in 16 patients with pressure in the internal carotid stump ranging from 0 to 40 (mean 22.4) mmHg. On the other hand, 11 additional patients with stump pressure less than 35 mmHg tolerated the trial occlusion well, underwent carotid endarterectomy without internal shunt and had no deficit symptoms during or after operation. One patient died postoperatively. Hemiparesis appeared in two more patients, but resolved completely in one and gave only minor sequelae in the other. These complications were related to the preoperative condition (stroke) and the postoperative residual pressure gradient. It is concluded that trial occlusion of the carotid artery and observation of the awake patient provide reliable information on the need for an internal shunt during carotid endarterectomy.

Routine use of a shunt for carotid endarterectomy

A temporary inlying shunt used during carotid endarterectomy is the ideal method of cerebral protection. The data presented suggest that if meticulous technique is used, the potential complications of a shunt may be avoided and excellent clinical results expected. When a shunt is used properly, carotid endarterectomy may be performed in a teaching situation with a high degree of safety.

EEG surveillance as a means of extending operability in high risk carotid endarterectomy

Some patients who have transient ischemic attacks are denied operation because severe occlusive lesions in other extra-cranial arteries may be inappropriately interpreted as constituting an unacceptable surgical risk, or because the lesion is so distal as to make its removal hazardous. Failure of endarterectomy is usually due to incomplete removal of the lesion or to thrombosis upon the frayed intima. Such lesions require excellent visualization and meticulous surgical technique -- not always possible with a shunt. Among 130 consecutive carotid endarterectomies performed under general anesthesia, EEG changes consistent with cerebral ischemia appeared in only nine (7%). These patients required a shunt. In 11 patients normal EEG tracings were obtained during endarterectomy despite contralateral carotid occlusion. None of these patients had a neurological deficit. Continuous EEG monitoring is a reliable method of detecting changes in cerebral perfusion, permits a more meticulous endarterectomy in high-lying lesions without a shunt, and extends operability in high risk patients. Angiographical findings may be an unreliable predictor concerning risk of endarterectomy.

Carotid endarterectomy

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