Carotid Stump Research Articles

Minimizing the risks of carotid endarterectomy

In 1971 this study was undertaken to determine optimal methods and guidelines for lowering the mortality and neurologic complication rates associated with carotid endarterectomy. Of 570 carotid endarterectomies, 481 (84%) were performed under local anesthesia to provide continuous neurologic monitoring and to permit operation on the very elderly and poor-risk patient. In 418 of these procedures carotid stump pressures (CSPs) were measured with patients awake to determine the level of back pressure sufficient for brain protection during operative occlusion. Selective shunting was necessary in 40 (8%) of these cases. Of 78 patients with a CSP of 0 to 25 mm Hg, only 39 (50%) required shunting. Only one patient with a pressure >25 mm Hg (29 mm Hg) needed a shunt. The CSP/brachial blood pressure (BBP) index was calculated for 410 procedures. Of 97 patients with a CSP of 0 to 30 mm Hg, only 31 required a shunt (CSP/BBP index 0.01 to 0.18). No shunt was necessary for an index >0.18. Patients with a contralateral occlusion or severe stenosis required a shunt six times more frequently than those with unilateral disease. For 570 procedures the overall mortality rate was 0.7% and the neurologic complication rate was 0.9%. When local anesthesia was used for 481 procedures, there was only one death (0.2%). For 74 asymptomatic lesions there were no deaths or stroke. Neurologic monitoring under local anesthesia and CSPs are reliable indicators for selective shunting. Multiple-risk factors influence the outcome of carotid endarterectomy, but most can be avoided.

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.

Cerebral Perfusion and Cerebral Protection during Carotid Endarterectomy

The relative safety of carotid endarterectomy depends upon surgical expertise combined with appropriate monitoring of cerebral perfusion and the ability to intervene either surgically or pharmacologically to match cerebral perfusion to cerebral oxygen requirement. Methods of monitoring adequacy of cerebral perfusion are reviewed and include regional cerebral blood flow measurements, electroencephalographic monitoring, carotid stump pressure measurements, jugular venous oxygen partial pressure, neurological assessment and plethysmographic techniques. When cerebral perfusion is inadequate, such procedures as insertion of a temporary bypass shunt and maintenance of normocarbia may improve cerebral perfusion. Anticoagulants along with pharmacologic intervention to either increase cerebral perfusion pressure or reduce cerebral oxygen requirement may be used to preserve cerebral function.

Overall management of vascular lesions considered treatable with extracranial-intracranial bypass: part 1. Internal carotid occlusion.

From 1973 to 1979, 49 patients with internal carotid occlusion were evaluated and treated. Eighteen of 49 (37%) presented with transient ischemic attack/prolonged reversible ischemic neurological deficit, 14 of 49 (29%) presented with mild completed stroke, 13 of 49 (27%) presented with severe completed stroke, and 4 of 49 (8%) were asymptomatic. Surgical treatment consisting of extracranial-intracranial (EC-IC) bypass, internal carotid stump reconstruction and endarterectomy to open the occlusion, contralateral endarterectomy for carotid stenosis opposite the occlusion, and iatrogenic carotid occlusion with EC-IC bypass was carried out on 22 (45%) patients considered at risk for ischemia based on angiographic evidence of poor collateral circulation and potential sources of emboli. Medical treatment consisting of anticoagulants or anti-platelet aggregation agents was used in 27 (55%) patients with good collateral circulation. By 6 weeks after the initiation of treatment, 10 of 49 (20%) reached end points of new strokes and death. By an average of 3 years after treatment began, 30 of 49 (61%) reached the same end points. The results suggest that new ischemic events in the distribution of the occluded carotid artery occur infrequently if the angiographic study shows adequate collateral circulation to the ischemic territory at risk. Surgical revascularization should be reserved for patients with (a) recurrent ischemic events after the diagnosis of carotid occlusion or (b) poor collateral circulation.

Resection and reconstruction of the carotid artery in metastatic squamous cell carcinoma

Although it is uncommon to consider resection of the common and internal carotid arteries for involvement by carcinoma, nevertheless, if this is the only significant finding precluding an adequate ablative procedure, this operation is worthy of consideration. Ten procedures were performed in nine such patients; the carotid bifurcation was resected and continuity reestablished using Teflon or autogenous saphenous vein grafts. In attempting to predict the efficiency of the collateral cerebral cross-flow, arteriography, oculopneumoplethysmography and intraoperative measurement of carotid stump pressure were used in some patients. There was no operative mortality. The postoperative mortality rate was 20 percent and cerebrovascular complications occurred in 20 percent of the cases. Seven patients survived 9 months to 4 1 4 years. Teflon grafts appeared to have a higher patency rate than saphenous vein autogenous grafts. Although this series is very small, it is an evaluation of a procedure of last resort which appears worthwhile in carefully selected patients.

Cardiac Function and Hypercarbia

• In 12 patients with heart disease, hypercarbia was induced for carotid endarterectomy. Anesthesia was maintained with nitrous oxide in oxygen and methoxyflurane. In addition to intra-arterial measurements of blood pressure, cardiac output, systolic time intervals (STI), and pressure time indices (PTI) were determined in order to assess cardiovascular responses in these patients. Internal carotid stump blood pressure was measured in five patients before and after induction of hypercarbia. Mild elevation of the Paco2level affected systolic time intervals but not heart rate and blood pressure. When Paco2levels reached 56 to 65 torr, systolic but not diastolic blood pressure rose significantly, heart rate and cardiac output increased, while the shortening in the preejection period (PEP), left ventricular ejection lime (LVET), and the decrease in the PEP/LVET ratio signified increased mechanical cardiac activity. Hypercarbia caused intense sympathetic stimulation as demonstrated by twofold to threefold increases in plasma catecholamine levels. Stump blood pressure was elevated. Cardiac oxygen demand was significantly increased, while coronary filling time was shortened, as indicated by the increase in the tension time index and shortening in the diastolic time. This signified a relative myocardial underperfusion. Thus, while hypercarbia to levels of 66 to 70 torr increased internal carotid artery stump pressure, it also caused increased cardiac mechanical activity and concomitant unfavorable balance between myocardial oxygen consumption and supply. The measurement of STI and the computation of PTI provided early detection of alterations in cardiac function. (Arch Surg113:1196-1200, 1978)

Cardiac function and hypercarbia.

In 12 patients with heart disease, hypercarbia was induced for carotid endarterectomy. Anesthesia was maintained with nitrous oxide in oxygen and methoxyflurane. In addition to intra-arterial measurements of blood pressure, cardiac output, systolic time intervals (STI), and pressure time indices (PTI) were determined in order to assess cardiovascular responses in these patients. Internal carotid stump blood pressure was measured in five patients before and after induction of hypercarbia. Mild elevation of the Paco2 level affected systolic time intervals but not heart rate and blood pressure. When Paco2 levels reached 56 to 65 torr, systolic but not diastolic blood pressure rose significantly, heart rate and cardiac output increased, while the shortening in the preejection period (PEP), left ventricular ejection time (LVET), and the decrease in the PEP/LVET ratio signified increased mechanical cardiac activity. Hypercarbia caused intense sympathetic stimulation as demonstrated by twofold to threefold increases in plasma catecholamine levels. Stump blood pressure was elevated. Cardiac oxygen demand was significantly increased, while coronary filling time was shortened, as indicated by the increase in the tension time index and shortening in the diastolic time. This signified a relative myocardial underperfusion. Thus, while hypercarbia to levels of 66 to 70 torr increased internal carotid artery stump pressure, it also caused increased cardiac mechanical activity and concomitant unfavorable balance between myocardial oxygen consumption and supply. The measurement of STI and the computation of PTI provided early detection of alterations in cardiac function.

Management of trachea-innominate artery fistula

The case histories of three patients with trachea-innominate artery fistula are presented. Low tracheostomy was the etiologic factor producing the fistula in two patients. In both cases, the neck was hyperextended by placing a large roll behind the patient's shoulders and thereby elevating the trachea out of the mediastinum. In one patient a balloon cuff eroded the innominate artery. Management of these patients includes control of hemorrhage by cuff overinflation and/or by endotracheal intubation and packing of the tracheostomy site. The best surgical approach is via a right anterior thoracotomy and a separate neck incision to isolate the blood vessels involved. Median sternotomy should be avoided to prevent mediastinal infection and sternal dehiscence. Carotid stump pressures are a useful guide to determine the efficacy of innominate artery ligation. One patient was saved and is a long-term survivor.

The value of measuring intraoperative pressure in carotid endarterectomy (author's transl)

During the last 4 years 92 operations at the carotid bifurcation were performed. In almost all cases carotid stump pressure was measured. If the stump pressure was below one third of the systemic pressure endarterectomy was done with intraluminal shunt. Under these conditions neurologic symptome deteriorated 3 times, but improved after a few days. There was no hospital mortality.

Improved results with carotid endarterectomy.

Two hundred ninety patients undergoing carotid endarterectomy were reviewed. From 1968 to 1972, 188 patients had carotid endarterectomy under general anesthesia with use of a shunt and hypercarbia. Stump pressures were not recorded in this group. There were three deaths, three postoperative hemiplegias and two complications of transient limb weakness. From 1973 to 1975, 102 patients were operated on under local anesthesia with systemic Innovar and Sublimaze, normocarbia and intra-operative assessment of stump pressure. In this group there was one death, no hemiplegia, and no complications of transient limb weakness. Twenty of the 102 were shunted either on the basis of stump pressure or the loss of motor ability or consciousness on carotid clamping. Those shunted had stump pressures ranging from 10 to 70 mm Hg with a mean of 20 while those not shunted had stump pressures ranging from 20 to 85 mm Hg with a mean of 53 mm Hg. Five patients lapsed into unconsciousness despite internal carotid stump pressures of 30, 30, 34, 36 and 70 mm Hg respectively, thus requiring intraoperative shunting. This experience seriously questions the reliability of carotid stump pressure as the sole determinant to identify those patients who require intraoperative shunting. We have come full circle, back to operation under local anesthesia, since intraoperative assessment of the patient's motor ability and consciousness alone provide the only absolute criteria for assessing the need for intraoperative shunting. Since the operation can be performed with greater technical efficiency without a shunt and without the potential complications of shunting itself, it behooves the surgeon to have a reliable method of knowing when it is not required.