Stump Pressure Research Articles

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.

Bypass Blood Flow during Carotid Endarterectomy

The relationship of bypass shunt blood flow to arterial pressure and stump pressure was studied in 12 informed patients undergoing carotid endarterectomy. These patients were anesthetized with halothane plus nitrous oxide. Systemic arterial blood pressure was measured with a radial artery catheter, and stump pressure as well as distal shunt pressure (carotid pressure distal to the shunt) were measured with a 25-gauge needle inserted cephalad to the bypass shunt. From the pressure drop across the bypass shunt, blood viscosity, geometry of the bypass tubing and the use of Poiseullie's law, the shunt blood flow can be calculated. The calculated shunt flow shows a close correlation with the difference between arterial pressure and stump pressure (r = 0.91) as well as with the slope of arterial pressure increase following carotid occlusion (r = 0.82); but it is poorly correlated with the stump pressure. Administration of 100 ml low molecular weight dextran solution does not improve the shunt blood flow, whereas 500 ml low molecular weight dextran significantly decreases blood viscosity. The patency of the carotid artery as assessed by angiogram does not give a proper indication of the need for a bypass shunt. The shunt flow as well as the need of such a shunt might be predicted by the use of the difference of arterial pressure and stump pressure. If the slope of arterial pressure increases rapidly following carotid occlusion, it can also be used to determine the necessity of such a shunt.

Oculopneumoplethysmography: its relationship to intraoperative cerebrovascular hemodynamics.

The oculopneumoplethysmography (OPPG) test has been proposed as an effective method to identify significant carotid artery stenoses. To evaluate the clinical relevance of OPPG testing performed without carotid compression, the results of the preoperative OPPG studies, intraoperative pressure gradient measurements, and intraoperative "stump" pressure determinations were correlated retrospectively with the severity of the carotid lesions. Patients with positive OPPG test results had a mean pressure gradient of 44 mm Hg, whereas those patients with negative results had a mean gradient of 20 mm Hg. Of the patients with true-positive OPPG test results, 94% (29/31) had lesions causing at least 70% diameter reduction. However, overall accuracy of OPPG testing in this series was only 63% (33/52), as 81% (17/21) of the patients with false-negative OPPG test results also had tight lesions. Without carotid compression, OPPG testing was not useful in predicting intraoperative stump pressure. The OPPG test reflects a balance between the severity of the carotid stenosis and the adequacy of compensatory collateral flow. A positive OPPG test result is reliable in identifying those patients at greatest risk from their carotid arterial lesion. Although a negative OPPG test result does not exclude a tight stenosis, it does provide information with regard to its hemodynamic significance.

Hemodynamic aspects of cerebral arteriovenous malformations.

Local hemodynamics were studied in 16 patients undergoing total extirpation of cerebral arteriovenous malformation (AVM). Directional Doppler technique was used for the registration of blood velocities in vessels feeding and draining the AVM. Calculated flow in single feeding arteries ranged from 3 to 550 ml/min (average, 180 ml/min). An estimation of total AVM flow was possible in nine patients, and ranged from 150 to more than 900 ml/min (average, 490 ml/min). Pressure recordings were made from feeding arteries at their entrance to the AVM. This pressure was well below the systemic arterial blood pressure in all cases, and ranged from 40 to 77 mm Hg (average, 56 mm Hg). On temporary occlusion, this stump pressure instantly rose to from 55 to 95 mm Hg (average, 76 mm Hg). Draining vein pressure before occlusion ranged from 8 to 23 mm Hg (average, 15 mm Hg), and fell to zero in all patients when the AVM was occluded. These data and other clinical observations are discussed with regard to adjacent brain-tissue perfusion, and with special emphasis on the circulatory breakthrough that can follow the occlusion of these high-capacity shunts.

Stump pressure: an unreliable guide for shunting during carotid endarterectomy.

A correlative analysis was made between the neurological status of the awake patient and the internal carotid artery stump pressure in 125 consecutive patients undergoing carotid endarterectomy. There was no mortality in this series. Twenty-four patients lost consciousness immediately after carotid cross-clamping, even though stump pressures were above 50 mm Hg in more than one third of the cases. The majority (80.8%) of the patients tolerated cross-clamping (stump pressures were between 20 and 90 mm Hg). This study demonstrated the variability of cerebral tolerance relative to absolute stump pressure guidelines, such as 25 or 50 mm Hg; reliance on these values to determine the need for intraoperative shunting could lead to stroke at operation. Our experience also showed that assessment of the awake but tranquil patient continues to be the safest and most reliable guide to selective shunting during carotid endarterectomy.

Failure of carotid stump pressures. Its incidence as a predictor for a temporary shunt during carotid endarterectomy.

A total of 289 carotid endarterectomies were performed in 204 patients. A decision to place a temporary shunt during carotid endarterectomy in this series was made entirely on the basis of intraoperative EEG monitoring. Retrospectively, the correlation between stump pressures and the results of intraoperative EEG monitoring in each case was determined. Evidence of ischemia developed in 6% of the total series on intraoperative EEG monitoring despite a stump pressure of greater than 50 mm Hg. The degree of disagreement between stump pressure and EEG varied according to clinical category in this series. In those endarterectomies performed for completed stroke, all cases requiring shunting had stump pressures less than 50 mm Hg. In those cases performed for symptoms of vertebral basilar insufficiency, however, 77% of the cases requiring an intraoperative shunt had stump pressures greater than 50 mm Hg. A review of the complication rate in the various study groups indicates that the use of intraoperative EEG is a safe indicator of cerebral ischemia during carotid endarterectomy regardless of stump pressure.

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)

Division of the left renal vein: Guidelines and consequences

Ligation and division of the left renal vein is a reasonably safe procedure in selected patients when exposure of the perirenal aorta is crucial. This manipulation is possible because of extensive venous collateralization from the left kidney in man. Measurement of the venous stump pressure before ligation is recommended to assess the degree of collateralization, and the upper limit within which the vein may be divided safely is probably in the neighborhood of 60 cm of water. Reanastomosis of the vein is not necessary for preservation of renal function, although transient left renal dysfunction may occur. Examination of the urine and careful monitoring of renal function should be routine in the postoperative period. Intravenous urography and left spermatic venography later in the postoperative course can indicate the ultimate degree of function of the left kidney and the pathways of venous collateralization. Preservation of normal function and venous architecture at the renal hilum should be the rule.

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.

Results of carotid endarterectomy for vertebrobasilar insufficiency: an evaluation over ten years.

A review was performed of 114 patients with symptoms of vertebrobasilar insufficiency (VBI) alone, or in combination with carotid territory transient ischemic attacks or carotid territory completed stroke (cCS) with follow-up extending to ten years. The most frequent symptoms of VBI were visual changes (50%), dizziness (31%), and syncope (30%). Patients with symptoms of VBI and arteriographic evidence of intracranial disease, regardless of stump pressure, are at high risk for cerebral ischemia during endarterectomy. At late follow-up, ranging from one to ten years, 63% of the patients were alive; 88% were asymptomatic. Causes of death were mainly cardiac (44%) and stroke (36%), but patients with symptoms of VBI and cCS died earlier and from a second cerebrovascular accident. When a correct preoperative diagnosis was established, carotid endarterectomy produced relief of symptoms in 90% of the 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 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.

Inferior mesenteric artery stump pressure: a reliable index for safe IMA ligation during abdominal aortic aneurysmectomy.

Fifty-two patients undergoing nonemergent abdominal aortic aneurysmectomy were prospectively studied to determine when the inferior mesenteric artery (IMA) could be ligated without subsequent development of ischemic colitis. Cannulation of the severed distal IMA for blood pressure measurement (IMA stump pressure) before and after aortic reconstruction was attempted in all and possible in 39 individuals. In 13 the IMA was thrombosed precluding pressure measurement. Prereconstruction and postreconstruction mean IMA stump and systemic arterial blood pressure measurements were computed and mean IMA/systemic pressure ratios were calculated. All patients underwent postoperative colonoscopy. One patient developed postoperative ischemic colitis. Her postreconstruction ratio was 0.37 and her postreconstruction mean IMA blood pressure was 33 mmHg, the only individual with a ratio and pressure less than 0.40 and 40 mmHg, respectively. Internal iliac arterial pulsations could not be restored in two patients. Although postresection indices were less than preresection indices in both, postresection indices were greater than 0.40 and 40 mmHg. In this study, if the IMA was thrombosed or if postresection pressures and ratios measured greater than 40 mmHg and 0.40 respectively, ischemic colitis did not develop following abdominal aortic aneurysmectomy. This simple test may prove useful in identifying patients at risk for developing postoperative ischemic colitis or if IMA revascularization is required.

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.

Carotid endarterectomy: is an indwelling shunt necessary?

Three hundred and four consecutive endarterectomies were performed with general anesthesia and without a temporary indwelling shunt. Eight patients (2.6%) awoke from anesthesia with a new neurological deficit. Eight additional patients later developed neurological symptoms, suggesting that the absence of a shunt did not contribute to their complication. Of these 16 patients, two (0.6%) died, nine (3.0%) had a temporary neurological deficit, and five (1.6%) had a permanent neurological deficit. A prolonged occlusion time, a stump pressure of less than 50 mm Hg, or the presence of additional carotid lesions did not show a significant statistical relationship to postoperative neurological deficit.

Simultaneous Bilateral Carotid Endarterectomies

Twelve patients with bilateral symptomatic lesions of internal carotid arteries have had bilateral carotid endarterectomy at single operations without complications. These were patients up to age 80 who had prior mycardial infarction, stroke with recovery, and hemispheric and nonhemispheric episodes. Neurologist's clearance and three- or four-vessel intracranial-extracranial angiography preceded all operations, which were performed with the patient under general anesthesia. Stump pressure measurements were the principal guideline of adequacy of collateral flow and predictor of safe outcome. The safety of this concept of bilateral operations during one anesthesia can eliminate uncertainties of sequence and timing, obviate delay and indecision, and avoid the hazards of a second anesthetic-operative experience.

Internal carotid artery stump pressure and cerebral blood flow during carotid endarterectomy: modification by halothane, enflurane, and innovar.

Carotid endarterectomy requires temporary surgical occlusion of the involved carotid artery. During occlusion, the minimally acceptable (critical) internal carotid artery stump pressure is reported to be 50 torr, whereas for regional cerebral blood flow (rCBF), a critical range is reported to be 18-24 ml/100 g/min. During 90 carotid endarterectomies, rCBF and stump pressure were measured and the EEG continuously monitored. A positive correlation between rCBF and stump pressure (i.e., when both were either above or below their respective critical values) was observed in only 58 per cent of the cases. In 28 per cent stump pressures of less than 50 torr were observed despite rCBF's above 24 ml/100 g/min and normal EEG's. In 8 per cent stump pressures were more than 50 torr but rCBF's were less than 18 ml/100 g/min and EEG changes of ischemia were commonly observed. In the remaining 6 per cent rCBF's were marginal (18-24 ml/100 g/min) while stump pressures were more than 50 torr and EEG changes were not observed. The relationship between stump pressure and rCBF was influenced by the anesthetic. In the absence of transient ischemia during occlusion (that is, rCBF greater than 18 ml/100 g/min), halothane and enflurane anesthesia were associated with significantly higher rCBF's and lower stump pressures than was neuroleptanesthesia. Pre-occlusion and post-occlusion rCBF measurements also demonstrated cerebral vasodilation by halothane and enflurane (halothane greater than enflurane) and vasoconstriction by neuroleptanesthesia. It is concluded that stump pressure is an unreliable index of CBF during carotid occlusion and that its relationship to CBF is considerably influenced by the anesthetic.

Carotid endarterectomy: Is a shunt necessary?

Seventy-seven carotid endarterectomies performed on fifty-nine patients, using induced systemic hypertension during carotid artery clamping, were reviewed. The risk of cerebral ischemia is reduced to a minimum by this technic. The measurement of the internal carotid artery stump pressure is an excellent guideline for the need of additional brain protection. An internal shunt is rarely necessary. Thromboembolic phenomena contributed to the major neurologic complications encountered(two deaths and one stroke). Extreme gentleness and careful surgical technic cannot be overemphasized.

Regional cerebral blood flow measured by the gamma camera after direct injection of 133Xe into the distal stump of the occluded middle cerebral artery.

Regional cerebral blood flow (rCBF) was measured after intracarotid injection of 133Xe concurrently with measurements of local cerebral blood flow (LCBF) after injection of 133Xe directly into the distal stump of the occluded middle cerebral artery (MCA) by the use of the gamma camera after producing experimental ischemia in baboons by occluding the MCA. Regional MCA stump pressure (rMCAP) was also measured. Regions of ischemia assessed by intracarotid injection of 133Xe correlated well with the territory of infarct defined by injection of 133Xe into the distal MCA stump. Flow values in ischemic regions obtained by direct injection of 133Xe into the MCA were 15% to 20% lower than those obtained by intracarotid injection of 133Xe. Possible explanations for these differences are discussed. During induced hypertension autoregulation in ischemic areas was abolished and paradoxical responses of LCBF and rMCAP to changes in arterial carbon dioxide tension (PaCO2) were confirmed.