Routine Shunting Research Articles

Selective shunting with EEG monitoring is safer than routine shunting for carotid endarterectomy

The purpose of this study was to identify whether EEG is an adequate method of monitoring cerebral perfusion during carotid endarterectomy and of determining the need for use of an indwelling shunt. A retrospective review of 305 carotid endarterectomies comparing the results of routinely shunted patients with patients selectively shunted based on EEG monitoring, was carried out. Of the carotid endarterectomies, 92 (30%) were routinely shunted and 213 (70%) were selectively shunted. In the selectively shunted group, 34 (16%) subsequently required shunting. The major stroke rate in the routinely shunted group was 4.4% ((4) cases) and in the selectively shunted group was 0.5% ((1) stroke). Three of the four major strokes in the routinely shunted group were embolic in origin and one was caused by acute thrombosis. The only major stroke in the selectively shunted group was from intracerebral hemorrhage. In conclusion EEG monitoring is a safe and reliable method to determine the need for shunting during carotid endarterectomy. Routine non-selective use of a shunt may increase the risk of perioperative stroke from arterial injury and associated thromboembolism.

The fate of residual defects following carotid endarterectomy detected by early postoperative duplex ultrasound

The purpose of this study is to evaluate the results of color-flow duplex ultrasound (CFD) soon after carotid endarterectomy (CEA) to determine the incidence of residual abnormalities and their effect on subsequent outcome and management. We reviewed 318 consecutive CEAs performed over a 48 month-period. Of these, 206 were followed up with CFD, 195 prior to discharge and 11 at first follow-up (within 9 weeks). Patients (43) followed up with only oculoplethysmography (OPG) or those with no OPG or CFD (69) were excluded from the study. All CEAs were performed under general anesthesia with routine shunting and patch angioplasty. Twelve of the 206 studies (5.8%) were abnormal. Two patients with an abnormal CFD sustained perioperative stroke, both of whom had distal intimal lesions of > 60% diameter stenosis by velocity criteria. Four patients had > 60% stenosis and were reoperated upon to correct technical errors. The remaining 6 patients are asymptomatic. Four had residual lesions of < 60% stenosis, three of which have returned to normal on subsequent CFD. Two residual lesions had > 60% stenosis; one returned to normal by CFD and the other remains abnormal at 10 months. In the group of 192 normal postoperative CFD studies, there were no strokes, deaths, or redo procedures (0%, 95% confidence interval 0% to 1.54%) compared with a combined 50% rate (6 of 12) of either stroke (2 of 12) or redo procedure (4 of 12) when the postoperative CFD was abnormal (95% confidence interval 22.3% to 77.7%, P < 0.0001). During the study period the CEA stroke rate was 0.9% (3 of 318), with a combined stroke-mortality rate of 1.3% (4 of 318). Early postoperative CFD identified residual abnormalities in 5.8% of carotid endarterectomies despite a low overall stroke mortality rate. One half of these abnormalities resulted in stroke or required operative correction. Colorflow duplex ultrasound is useful in identifying residual abnormalities following CEA and should be considered for intraoperative use.

Low-Pressure Hydrocephalic State and Viscoelastic Alterations in the Brain

Most shunt-dependent hydrocephalic patients present with predictable symptoms of headache and mental status changes when their cerebrospinal fluid shunts malfunction. Their intracranial pressure (ICP) is usually high, and they usually respond to routine shunt revision. This report describes 12 shunted patients who were admitted with the full-blown hydrocephalic syndrome but with low to low-normal ICP. All 12 patients had been maintained previously on medium-pressure shunts. Their symptoms included headache, lethargy, obtundation, and cranial neuropathies. At peak symptoms, their ventricular sizes were large (ventricular/biparietal ratio of 0.35 to 0.45) in six and massive (ventricular/biparietal ratio > 0.45) in six and their ICPs ranged from 2.2 to 6.6 mm Hg, with a mean of 4.4 +/- 1.3 mm Hg (+/- standard deviation), i.e., below or well within the pressure range of their shunts. The pressure volume index of three patients at peak symptoms ranged from 39.2 to 48.5 ml, with a mean of 43.9 +/- 4.6 ml, which represents a 190% increase from the predicted normal value. Seven patients failed to improve with multiple shunt revisions, including the use of low-pressure valves. In 11 patients, symptoms and ventriculomegaly were not reversed except with prolonged external ventricular drainage at subzero pressures (mean external ventricular drainage nadir pressure of -5.7 +/- 3.6 mm Hg, for a mean period of 22.2 days). During external ventricular drainage treatment, symptoms correlated only with ventricular size and not with ICP. All 11 were subsequently treated successfully with a new medium- or low-pressure shunt. One patient was treated successfully with prolonged shunt pumping. We postulate that: 1) the development of this low-pressure hydrocephalic state is related to alteration of the viscoelastic modulus of the brain, secondary to expulsion of extracellular water from the brain parenchyma, and to structural changes in brain tissues due to prolonged overstretching; 2) certain patients are susceptible to developing low-pressure hydrocephalic state because of an innate low brain elasticity due to bioatrophic changes; 3) low-pressure hydrocephalic state symptoms are due not to pressure changes but to brain tissue distortion and cortical ischemia secondary to severe ventricular distortion and elevated radial compressive stresses within the brain; and 4) treatment must be directed toward allowing the entry of water into the brain parenchyma and the restoration of baseline brain viscoelasticity.

Comment on routine shunting

We have used most of the modalities of cerebral protection mentioned in this symposium, and are well aware of all the data. We finally settled on general anaesthesia and routine shunting for all carotid endarterectomies, using a No. 8 or No. 10 Fr straight plastic catheter about 9cm long. We have had no technical problems and only one instance in which the shunt clotted in about 3000 operations done over the last 25 years by our group. In a personal series of 707 operations, operative mortality was 0.42%, mostly cardiac, the incidence of severe deficits was 0.56% and that of mild deficits 1%, a total of 1.56%. The advantages of a shunt are: simple, quick, safe, always available, effective, allows for no-haste surgery, which is especially important when training residents and fellows, and acts as a stent for closure. This is of special importance in complicated lesions and when patch angioplasty is required. The majority of the practicing clinical vascular surgeons present at meetings in the U.S. use a shunt routinely. Finally, in the U.S.A. the legal implications of shunting versus non-shunting are very important. The disadvantages of the shunt are in practice minimal.

Shunt Lengthening: A Descriptive Review

Shunt lengthening is a neurosurgical procedure unique to the pediatric patient. It is considered to be a minor operation to the professional, but means another hospitalization to parents of children who have often times already had many hospitalizations. A review of 27 children who underwent routine shunt lengthening revealed that none developed the most common complication of infection following this operation. After questioning parents about their need for information on shunt lengthening, a fact sheet explaining the procedure was written. As a result of our findings and need to be more cost efficient while safely caring for patients, we have been successful in changing nursing management of these children.

Intraoperative Electroencephalographic Monitoring During Carotid Surgery with Routine Shunting

Fifty-nine patients undergoing sixty-four carotid reconstructions with routine intraluminal shunting had intraoperative electroencephalographic monitoring. The onset of rhythm or amplitude disturbances was demonstrated in 14 patients during exposure of the carotid artery, and in 24 patients during initial carotid clamping. Disturbances were seen in 15 patients during the period of intraluminal shunting and increased momentarily during the second clamping period. During closure of the surgical wound, all abnormalities disappeared except in one patient who ultimately developed a neurologic deficit upon awakening. Although patients who maintained normal electroencephalographic readings had higher carotid stump pressure (59 mm) than those who did not (42 mm), individual values were scattered. Intraoperative monitoring during carotid surgery with routine shunting has little usefulness.

Carotid Endarterectomy: Experience at a Community Hospital

One hundred and nineteen consecutive carotid endarterectomies (CEAs) performed on 86 patients have been reviewed. Thirty-three patients had bilateral CEAs. The indications were: (1) asymptomatic stenosis or ulceration (29%); (2) transient ischemic attack and amaurosis fugax (58%); and (3) reversible is chemic neurologic deficit and stroke (13%). Sixty percent of patients were shunted and 40% were not. There were 1 postoperative death in the first group and 2 strokes in each group. The overall stroke and death rates were 3.4% and 0.8% respectively. Eighty-eight percent and 83% of patients were alive and stroke free respectively during the forty-two-month follow-up period. The authors conclude that (1) CEA can be safely performed at a community hospital and (2) routine shunting or no shunting does not affect the patient's outcome.

Recurrent stenosis by duplex scan following carotid endarterectomy.

Between June 1984 and January 1986, 155 carotid endarterectomies were performed with routine shunting. Serial duplex scanning was performed during an 18-month period on 124 vessels. The results of this duplex scan review revealed the following data: A normal scan was obtained in 87/124 (70.1%). Recurrent stenosis was identified in 35/124 (28.1%), and an occluded vessel was identified in 2/124 (1.6%). Of the total recurrent stenosis group, recurrent stenosis was graded mild in 22/124 (17.7%), moderate in 7/124 (5.6%), and severe in 6/124 (4.8%). Of the 35 vessels with recurrent stenosis by duplex scanning, 22/35 (62.8%) were in female patients, and 13/35 (37.2%) were in male patients. Of the vessels with severe recurrent stenosis, 5/6 (83%) were in female patients. Recurrent stenosis following carotid endarterectomy is more common than appreciated clinically, and female patients in particular may be more prone to recurrent stenosis.

Carotid endarterectomy in patients with territorial transient ischemic attacks

Results are presented of a retrospective analysis of 651 carotid endarterectomies in 605 patients with carotid territorial transient ischemic attacks (TIAs). All operations were performed by the same surgeon in a community hospital from 1963 to 1986. Arteriographic findings consisted of carotid stenosis of 50% or greater in 88.5% of patients and stenosis less than 50% and/or an ulcerated plaque in the remaining 11.5%. Medical risk factors were detected in 92% of patients; hypertension, peripheral vascular disease, and coronary atherosclerosis were most prevalent. All operative procedures were conducted with the patients under general anesthesia, routine shunting, and arterial closure without a patch. The perioperative stroke rate was 1.5% (10 patients); the mortality rate was 0.8% (three deaths from myocardial infarction and two from stroke) for a combined stroke and mortality rate of 2.0% (13 of 605 patients). Follow-up (mean 61.8 months) was possible in 570 (96%) of the patients surviving operation without a perioperative stroke. The cumulative probability of late stroke (i.e., cerebral infarct ipsilateral to the operated artery) was 2.5% at 5 years and 8.1% at 10 years. When the perioperative stroke-mortality rate (2.0%) is combined with the data for late ipsilateral stroke, the 5- and 10-year probabilities of ipsilateral stroke were 4.5% and 9.9%, respectively (mean 1% per year for 10-year period). Coronary atherosclerosis accounted for 43% of late deaths and 16% of strokes. The perioperative stroke-mortality rate of 2.0% in this group of patients falls within the acceptable range for carotid endarterectomy in patients with TIA. Moreover, long-term results of this study underscore the efficacy of carotid endarterectomy in decreasing the incidence of ipsilateral stroke in patients with carotid territorial TIAs.

Routine electroencephalographic (EEG) monitoring during carotid endarterectomy.

Controversy continues concerning the advisability of routine shunting, no shunting, or selective shunting during carotid endarterectomy. Because of its reflection of the physiologic state of the end organ, the authors chose routine 18 lead EEG monitoring as a guide to selective shunting and as an indication of adequate shunt function during all carotid endarterectomies performed from December 1977 through July 1982. In that period, 200 patients underwent 219 endarterectomies under general anesthesia and EEG monitoring. Ischemic EEG changes at the time of carotid cross clamping suggested the need for intraluminal shunts in 16% of patients. Insertion of shunts restored the EEG pattern to normal in all instances, although in two patients, adjustment of the shunt was required to maintain this results. EEG changes requiring shunting occurred in 10% of patients with unilateral disease, in 27% of patients with bilateral disease, and in 42% of patients with unilateral stenosis and contralateral occlusion. Twenty-seven patients had small fixed neurologic deficits before operation. Surgery was not delayed in these individuals who demonstrated no increased requirement for shunts and no new postoperative neurologic deficits. In the group of 150 endarterectomies performed as separate procedures, there was one (0.7%) fixed neurologic deficit after operation, one transient deficit (0.7%), and one death (0.7%). Sixty-nine endarterectomies were performed simultaneously with open heart surgery and were associated with one fixed neurologic deficit (1.4%) and two transient deficits (2.9%). All four deaths in this group were attributable to the cardiac surgical procedures. These results indicate that selective shunting based on EEG monitoring permits the safe performance of carotid endarterectomy, even in patients considered to be at high risk for postoperative neurologic deficit.

Seventeen-year experience with routine shunting in carotid artery surgery.

AbstractSafety of carotid artery surgery depends on proper case selection, meticulous surgical technique, and appropriate protection of the brain during carotid artery cross‐clamping. Various methods have been devised to determine the adequacy of collateral circulation, none of which has been proven practical and totally reliable. Attempts at increasing cerebral perfusion to the ischemic portion of the brain by induced hypertension, hypercarbia, and hypocarbia have been ineffective.The purpose of this presentation is to report our experience with routine intraluminal shunting in carotid artery surgery during the past 17 years. Advantages of routine shunting include maintenance of regional cerebral blood flow at the preclamping level and the elimination of any need for monitoring and haste during surgery. Insertion of the tube, properly done, does not injure the arterial wall and should not cause embolization. The presence of the tube within the arterial lumen does not interfere with exposure of the atheroma, yet it facilitates repair of the incision and prevents stricture by faulty suturing technique. Results of carotid artery surgery measured by the incidence of stroke are compared between shunted and nonshunted series. A review of the literature confirms our impression that shunting reverses ischemic changes detected by EEG and regional cerebral blood flow determinations. The usefulness of shunting in the surgical management of internal carotid aneurysm, kinked carotid artery, carotid body tumor, and carotid‐subclavian bypass graft is also described.

Complications of carotid endarterectomy and their prevention.

AbstractMortality and morbidity associated with carotid endarterectomy may be minimized by proper selection of patients and proper operative and postoperative management. Complications include cardiac and airway problems related to anesthesia, infection, hematoma, nerve pareses, parotitis, arterial disruption, false aneurysms, and carotid‐cavernous fistula. The most serious complication is the occurrence of neurologic deficits as a result of cerebral emboli or ischemia. Emboli are due to excessive manipulation of the artery, while ischemia results from hypotension, intracerebral thrombosis, or inadequate cerebral protection. Adequacy of collateral blood flow during carotid clamping is determined by temporary occlusion under local anesthesia, measurement of internal carotid artery stump pressure, or EEG monitoring. The most reliable method of cerebral protection is a temporary inlying shunt. Selective shunting is used if the patient is intolerant of temporary clamping, if stump pressure is below 55 mm Hg, or if EEG changes occur. For maximum safety, the author suggests routine shunting and general anesthesia. Operative mortality for patients experiencing transient ischemic attacks should be less than 1% and operation‐related neurologic deficits no more than 2%. Meticulous attention to technical details is obligatory. Hypotension should be avoided during and after operation to avert thrombosis, and excessive hypertension postoperatively must be treated promptly to avoid cerebral hemorrhage and edema. Operation is contraindicated on patients with acute profound and progressing strokes.

Conversion of multilocular hydrocephalus to unilocular. Case report.

✓ A patient with postinflammatory hydrocephalus had a multiloculated, lateral ventricular system that was treated by a routine shunting procedure after the multiloculated system had been converted into a uniloculated system by direct intraventricular surgery.