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PubMed1982

Evidence of early structural change in the artery wall of two-kidney one-clip Goldblatt hypertensive rats.

Vascular structural changes were studied during the development of two-kidney one-clip renal hypertension. The weight of the arteries and the concentration and total amount of ribonucleic acid, deoxyribonucleic acid, alkali-soluble proteins, collagen and elastin of the vascular wall were measured. Tritiated thymidine uptake was also determined 15 and 30 days after clipping. Hypertension developed in 58% of the animals while the rest remained normotensive. A significant increase in artery weight and in the total amount of nucleic acids and proteins was found in hypertensive rats. The uptake of 3H thymidine by the arteries of hypertensive rats was significantly increased 15 days after clipping. This increment showed a significant correlation with blood pressure levels. Present data seem to indicate that the increase in vessel wall dimensions observed is partly due to an increase in the number of smooth muscle cells during the acute phase; this alteration appears to be mainly due to the rise in blood pressure.

Animals↗
PubMed1982

Decrease in sympathetic nervous system activity and attenuation in response to stress following renal denervation in the one-kidney one-clip Goldblatt hypertensive rat.

We have found that renal denervation in the one-kidney one-clip Goldblatt hypertensive rat results in an attenuation of the hypertension associated with a decrease in sympathetic nervous system activity. To test further the hypothesis that the renal nerves (afferents) contribute to the maintenance of hypertension in this model by modulating sympathetic nervous system activity, plasma norepinephrine and epinephrine changes in response to stress were compared in hypertensive sham-operated (n = 6), renal denervated (n = 6) and control (n = 7) animals. Stress was produced in conscious resting unrestrained animals by administering two brief electrical stimulations to the hindlimb. Resting plasma norepinephrine was significantly higher (P less than 0.01) in hypertensive sham-operated (420 +/- 41 pg/ml) compared to renal denervated (289 +/- 23 pg/ml) or control (296 +/- 25 pg/ml) animals. There was no difference in resting plasma epinephrine among the groups. In response to stress there were significantly greater absolute increases in plasma norepinephrine and epinephrine in hypertensive sham-operated animals compared to renal denervated and control groups, suggesting that the one-kidney one-clip rat exhibits an enhanced sympathoadrenal response to stress. The response to stress in renal denervated rats was the same as that in the control group. Taken together, these data support the concept that the renal afferent nerves modulate sympathetic nervous system activity in the one-kidney one-clip hypertensive rat.

Animals↗
PubMed1989

Changes in plasma ACE activity during the development and reversal of one-kidney, one clip hypertension in rats.

Plasma angiotensin converting enzyme (ACE) activity was studied during the development and the reversal of one-kidney, one clip (1K1C) renal hypertension in rats (RHR). Plasma ACE activity was measured in RHR 1 (n = 11), 3 (n = 8), 6 (n = 12), 14 (n = 7), and 80-120 days (n = 17) after clipping. Plasma ACE activity (nmol/min/ml) was elevated (p less than 0.05) in chronic RHR (80-120 days; mean arterial pressure, MAP: 216 +/- 9 mmHg), being 142 +/- 14 (n = 17) vs. 100 +/- 3.2 (n = 20) for normotensive control rats (MAP: 116 +/- 3 mmHg), whereas no significant differences were observed at earlier times. Overactivity of the renin-angiotensin system (RAS) was demonstrated indirectly by the reduction of MAP (greater than 15 mmHg) in response to captopril (10 mg/kg, i.v.) only during the first 3 days after clipping and in chronic severely hypertensive rats. In another experiment, ACE activity in chronic RHR was measured serially before and 1, 6 and 24 hours after unclipping. Serial measurements of plasma ACE showed a progressive decrease from 145 +/- 26 to 122 +/- 21, 24 hours after unclipping (n = 7, p less than 0.05, paired Student t-test) when MAP was reduced from 204 +/- 15 to 113 +/- 7 mmHg. There was essentially no change during 24 hours from the initial values of RHR-sham (MAP: 206 +/- 5 mmHg, ACE: 140 +/- 19, n = 8) and normal rats-sham (MAP: 115 +/- 2 mmHg, ACE: 96 +/- 3, n = 6). These data provide further evidence that chronic renal hypertension is associated with important changes in the metabolism of vasoactive peptides.

Animals↗
PubMed1990

Contrasting effects of norepinephrine and 5-hydroxytryptamine on contractility of abdominal aorta of two kidney-two clip hypertensive rats. Effects of inhibitors of arachidonic acid metabolic enzymes.

This study intends to: 1) define reactivity in vessels of two kidney-two clip (2K2C) hypertensive rats (6-11 days after clipping); 2) determine the possible involvement of prostaglandins in modulating contractile vascular responses. Cumulative dose-response curves to norepinephrine (NE), 5-hydroxytryptamine (5-HT) and potassium chloride (KCl) were elicited on helical strips of abdominal aorta both in the absence and in the presence of prostacyclin synthetase (transylcypromine, TCP, 0.25mM) or cyclooxygenase (indomethacin, IND, 0.014 mM and acetylsalicylic acid, ASA, 0.20 mM) inhibitors Vessels of hypertensive animals developed significantly less tension to NE (n = 21) but higher tension and lower ED50 in response to 5-HT (n = 9) than sham control rat vessels. Force development to KCl (n = 9) was not statistically different between hypertensive and sham vessels. Vascular responses were decreased with the inhibitors, but the contrasting effects of NE and 5-HT on clip vessels were maintained. Threshold doses of PGE2 significantly reversed the effect of IND but not that of TCP on NE responses. Threshold doses of PGI2 had no significant effect on NE and 5-HT responses under TCP. The results would indicate: 1) different functional alterations for contractions to NE and 5-HT appear to have developed in vessels of 2K2C hypertensive rats; 2) PGE2 effectively contributes to modulation of NE responses in rat aorta strips; 3) these experiments suggest that prostaglandins do not play a significant role in the altered contractility of vessels in hypertensive rats.

Animals↗
PubMed1989

Effect of ketanserin and prazosin on blood pressure and cardiovascular reactivity to vasopressor agents during the development of two kidney-two clip renal hypertension in the conscious rat.

The present experiment was performed in order to evaluate some of the actions of ketanserin, a blocking agent active at the serotonin 2 (S2) receptors. Male rats were divided into: 1. Two kidney-two clip (2K-2C) renal hypertensive: a silver clip (0.25 mm width) was placed in both renal arteries. 2. Sham-operated: a similar operation without placing the clip was performed. Blood pressure (BP), heart rate and pressor responses to tyramine, angiotensin II and norepinephrine (NE), and the hypotensive effect of prazosin (Pz) and ketanserin (Kt) were recorded in the conscious animals 8 weeks later. Results showed that Pz produced a similar decrease in BP in hypertensive and sham animals while Kt lowered BP much more in hypertensive than in normotensive rats. Prazosin abolished the pressor response to tyramine while ketanserin only diminished tyramine effect. Both hypotensive agents shifted the dose-response curve to NE to the right. Present data have shown that ketanserin and prazosin are effective hypotensive agents in 2K - 2C renovascular hypertension in the rat. They also suggest that both hypotensive compounds have an alpha 1-blocking effect, somehow they seem to have some differences in their pattern of pharmacological action.

Adrenergic alpha-Antagonists↗
PubMed2001

A brief history of aneurysm clips.

In this communication the authors outline the development of aneurysm clips from those originally used by Walter Dandy to those currently in use. The history is rich in contributions from neurosurgical pioneers and innovators. As a result, the modern neurosurgeon has a wide selection of biocompatible aneurysm clips with known closing pressure, of variable sizes and shapes, and a selection of clip applicators that do not obstruct the surgical field.

History, 20th Century↗
PubMed1975

Memory clip for intracranial aneurysm surgery. Technical note.

The authors have devised a malleable V-shaped removable clip with mechanical memory effect of shape memory. This clip is easily removed by heating part of it to 79 degrees to 107 degrees C, causing the closed clip to return to its original V shape.

Adult↗
PubMed1981

New angled fenestrated clips for fusiform vertebral artery aneurysms.

New angled fenestrated clips are introduced for surgery of certain difficult aneurysms. Their usefulness was proven in two cases of fusiform vertebral artery aneurysms. The aneurysms were obliterated, new parent arteries were reconstructed, and the inclusion of adjacent vital nerves and vessels in the clips was avoided. Technical problems associated with the application of these clips are discussed.

Aneurysm↗
PubMed1982

Fenestrated clips for unusual aneurysms of the carotid artery.

Twenty-four different kinds of fenestrated clips are introduced for the obliteration of unusual aneurysms. The clips were used for eight aneurysms of the internal carotid artery and 10 aneurysms of the vertebral artery. All but one of the aneurysms were successfully obliterated. Recommendations are made concerning the actual use of the clips.

Aged↗
PubMed1986

Fenestrated clips for internal carotid artery aneurysms. Technical note.

A new aneurysm clip has been developed specifically for internal carotid artery (ICA) aneurysms. This fenestrated clip's occluding blades deviate laterally, since the majority of ICA aneurysms protrude posterolateral to the parent artery. The clip was applied safely in seven recent patients with ICA aneurysms.

Carotid Artery Diseases↗
PubMed1989

Regrowth of aneurysm sacs from residual neck following aneurysm clipping.

It is recognized that incomplete treatment of an aneurysm may result in recurrent hemorrhage with serious or fatal consequences. For this reason, patients treated at the authors' institution in whom a large portion of the aneurysm neck or sac remained after application of a clip or ligature have been subjected to reoperation. However, 1- to 2-mm residual necks seen in postoperative angiography have been thought to pose little risk. Some cases of aneurysms recurring from a narrow residual neck after clipping have been reported, and a few instances of recurrent aneurysm have been described after apparently complete occlusion of the neck (as observed angiographically or in the surgeon's judgment). In recent years, a surprising number of cases have been presented in which this seemingly unimportant remnant of the neck dilated over a long period to become a dangerous aneurysm. This finding stresses the importance of complete aneurysm occlusion and of postoperative angiography for the recognition of a residual aneurysm neck. This should be important not only in aneurysm clipping but also in the endovascular treatment of intracranial aneurysms with detachable balloons.

Adolescent↗
PubMed1990

A new intracranial Silastic encircling clip for hemostasis. Technical note.

A new encircling clip made of a silicone tube has been designed for treating accidentally injured cerebral vessels. No special holders are necessary. This clip can be tailored depending on the shape of the injured vessel. The clip is a simple and effective tool for achieving complete hemostasis.

Cerebral Arteries↗
PubMed1997

Endovascular treatment of cerebral aneurysms following incomplete clipping.

The authors report their experience using electrolytically detachable coils for the treatment of residual cerebral aneurysms following incomplete surgical clipping. Eight patients were treated for six anterior and two posterior circulation aneurysm remnants. All patients were referred for endovascular treatment by experienced cerebrovascular neurosurgeons at the authors' institution. Patients underwent follow-up angiography immediately after endovascular treatment. In seven of the eight patients, additional follow-up angiographic studies were obtained at periods ranging from 7 weeks to 2 years posttreatment. The latest follow-up angiograms demonstrated that six of the eight aneurysm remnants were 100% occluded, with near-complete occlusion of the other two aneurysm remnants. There was no permanent neurological or non-neurological morbidity or mortality associated with the treatment. There was no incidence of aneurysm hemorrhage during or after treatment. Endovascular treatment of cerebral aneurysm remnants following prior surgical clipping can be accomplished with acceptable morbidity and mortality rates. Endovascular coil occlusion can play an important adjunctive role in the treatment of those aneurysms that have been incompletely obliterated by surgical clipping.

Adult↗
PubMed2001

Combined surgical and endovascular techniques of flow alteration to treat fusiform and complex wide-necked intracranial aneurysms that are unsuitable for clipping or coil embolization.

OBJECT: Certain intracranial aneurysms, because of their fusiform or complex wide-necked structure, giant size, or involvement with critical perforating or branch vessels. are unamenable to direct surgical clipping or endovascular coil treatment. Management of such lesions requires alternative or novel treatment strategies. Proximal and distal occlusion (trapping) is the most effective strategy. In lesions that cannot be trapped, alteration in blood flow to the "inflow zone," the site most vulnerable to aneurysm growth and rupture, is used. METHODS: From 1991 to 1999 the combined neurosurgical-neuroendovascular team at the Massachusetts General Hospital (MGH) managed 48 intracranial aneurysms that could not be clipped or occluded. Intracavernous internal carotid artery aneurysms were excluded from this analysis. By applying a previously described aneurysm rupture risk classification system (MGH Grades 0-5) based on the age of the patient, aneurysm size, Hunt and Hess grade, Fisher grade, and whether the aneurysm was a giant lesion located in the posterior circulation, the authors found that a significant number of patients were at moderate risk (MGH Grade 2; 31.3% of patients) and at high risk (MGH Grades 3 or 4; 22.9%) for treatment-related morbidity. The lesions were treated using a variety of strategies--surgical, endovascular, or a combination of modalities. Aneurysms that could not be trapped or occluded were treated using a paradigm of flow alteration, with flow redirected from either native collateral networks or from a surgically performed vascular bypass. Overall clinical outcomes were determined using the Glasgow Outcome Scale (GOS). A GOS score of 5 or 4 was achieved in 77.1%, a GOS score of 3 or 2 in 8.3%, and death (GOS 1) occurred in 14.6% of the patients. Procedure-related complications occurred in 27.1% of cases; the major morbidity rate was 6.3% and the mortality rate was 10.4%. Three patients experienced aneurysmal hemorrhage posttreatment; in two patients this event proved to be fatal. Aneurysms with MGH Grades 0, 1, 2, 3, and 4 were associated with favorable outcomes (GOS scores of 5 or 4) in 100%, 92.8%, 71.4%, 50%, and 0% of instances, respectively. CONCLUSIONS: Despite a high incidence of transient complications, intracranial aneurysms that cannot be clipped or occluded require alternative surgical and endovascular treatment strategies. In those aneurysms that cannot safely be trapped or occluded, one approach is the treatment strategy of flow alteration.

Adolescent↗
PubMed2002

Endoscope-assisted clipping of a superior hypophyseal artery aneurysm without removal of the anterior clinoid process. Case report.

A 47-year-old man presented with a superior hypophyseal artery aneurysm and an ipsilateral posterior communicating artery aneurysm. Both lesions were successfully clipped without removal of the anterior clinoid process or retraction of the optic nerve by using endoscopic guidance. The endoscope was introduced into the prechiasmatic cistern and provided a clear visual field around the aneurysm that could not be seen via the operating microscope. The endoscope was useful in the identification of the medially projecting lesion and the small perforating branches of the ophthalmic segment of the internal carotid artery. A fenestrated clip could be introduced around the neck of the aneurysm and placed in the best position under endoscopic guidance. Endoscopy-assisted clipping is potentially a very useful procedure for aneurysm surgery.

Aneurysm↗
PubMed2002

Cerebral oxygen and microdialysis monitoring during aneurysm surgery: effects of blood pressure, cerebrospinal fluid drainage, and temporary clipping on infarction.

OBJECT: The aim of this study was to investigate potential episodes of cerebral ischemia during surgery for large and complicated aneurysms, by examining the effects of arterial temporary clipping and the impact of confounding variables such as blood pressure and cerebrospinal fluid (CSF) drainage. METHODS: Brain tissue PO2, PCO2, and pH, as well as temperature and extracellular glucose, lactate, pyruvate, and glutamate were monitored in 46 patients by using multiparameter sensors and microdialysis. Baseline data showed that brain tissue PO2 decreased significantly, below a mean arterial pressure (MAP) threshold of 70 mm Hg. Further evidence of its relationship with cerebral perfusion pressure was shown by an increase in mean brain tissue PO2 after drainage of CSF from the basal cisterns (Wilcoxon test, p < 0.01). Temporary clipping was required in 31 patients, with a mean total duration of 14 minutes (range 3-52 minutes), causing brain tissue PO2 to decrease and brain tissue PCO2 to increase (Wilcoxon test, p < 0.01). In patients in whom no subsequent infarction developed in the monitored region, brain tissue PO2 fell to 11 mm Hg (95% confidence interval 8-14 mm Hg). A brain tissue PO2 level below 8 mm Hg for 30 minutes was associated with infarction in any region (p < 0.05 according to the Fisher exact test); other parameters were not predictive of infarction. Intermittent occlusions of less than 30 minutes in total had little effect on extracellular chemistry. Large glutamate increases were only seen in two patients, in both of whom brain tissue PO2 during occlusion was continuously lower than 8 mm Hg for longer than 38 minutes. CONCLUSIONS: The brain tissue PO2 decreases with hypotension, and, when it is below 8 mm Hg for longer than 30 minutes during temporary clipping, it is associated with increasing extracellular glutamate levels and cerebral infarction.

Adult↗
PubMed2003

Outcomes after cerebral aneurysm clip occlusion in the United States: the need for evidence-based hospital referral.

OBJECT: In an age of multimodality and multidisciplinary treatment of cerebral aneurysms, patient outcomes have improved significantly. For a number of complex surgical procedures, hospitals with high case volumes yield superior outcomes. The effect of hospital volume on the mortality rate after emergency and elective cerebral aneurysm clip occlusion in a nationally representative sample of patients is unknown. METHODS: Using clinical data derived from the Nationwide Inpatient Sample for the years from 1995 through 1999, 12,023 patients who underwent clip occlusion of a cerebral aneurysm (International Classification of Diseases, Ninth Revision, Clinical Modification code 3951) were included. Patient age, comorbid conditions, nature of admission, and diagnosis of subarachnoid hemorrhage were abstracted. Hospital case volume was grouped into quartiles. Unadjusted and case-mix adjusted analyses were performed. The mean patient age was 53.2 +/- 13.5 years. The overall crude postoperative mortality rates for emergency and elective aneurysm clip occlusion were 12.2 and 6.6%, respectively. Very low volume hospitals demonstrated higher mortality rates than very high volume hospitals for both emergency (14.7 compared with 8.9%, p < 0.001) and elective (9.4 compared with 4.5%, p < 0.001) aneurysm surgery. Patient-specific predictors of death in the multivariate model were renal disease (odds ratio [OR] 3.32, p < 0.042); age (> 60 years, OR 2.36, p < 0.001; 51-60 years, OR 1.63, p < 0.001; 40-50 years, OR 1.25, p = 0.047); chronic obstructive pulmonary disease (present, OR 1.52, p < 0.001); and nature of admission (emergency, OR 1.18, p = 0.03). Provider-specific predictors of death included very low volume (OR 1.59, p < 0.001); low-volume (OR 1.37, p = 0.001); and high-volume (OR 1.45, p < 0.001) hospitals compared with very high volume hospitals. CONCLUSIONS: A significant volume-outcome effect exists for surgical treatment of cerebral aneurysms in the US. Factors influencing this effect should be investigated to guide future healthcare policy and evidence-based referral. Whenever possible, healthcare practitioners should refer patients to centers in which superior outcomes are consistently demonstrated.

Adult↗
PubMed2004

Intentional partial coil occlusion followed by delayed clip application to wide-necked middle cerebral artery aneurysms in patients presenting with severe vasospasm. Report of two cases.

The treatment of ruptured cerebral aneurysms in patients presenting with vasospasm remains a particular challenge. The authors treated two patients harboring Hunt and Hess Grade 1 subarachnoid hemorrhages from middle cerebral artery (MCA) aneurysms associated with severe local angiographically demonstrated yet asymptomatic vasospasm on presentation. Because both aneurysms had wide necks and were located at the MCA bifurcation, they were believed to be anatomically suitable for microsurgical clip application. Severe M, vasospasm was believed to be a relative contraindication to open surgery, however. An intentionally staged endovascular and microsurgical treatment strategy was planned in each patient. Partial coil occlusion of the aneurysmal dome was performed to prevent the lesion from rebleeding and was followed by balloon angioplasty of the spastic vessel. Early treatment of the severe spasm appeared to prevent significant delayed neurological ischemic deficit. Following resolution of the vasospasm, definitive clipping of the aneurysms was performed on Day 13 post embolization. One patient had a good clinical recovery and was discharged without neurological deficit. The other patient's hospital course was complicated by the occurrence of a postoperative posterior temporal infarct requiring partial temporal lobectomy, although she eventually had a good recovery with only a small visual field deficit. Based on data obtained in these two patients, one can infer that ruptured wide-necked MCA aneurysms associated with severe local vasospasm may best be treated using a staged combined treatment plan. Delayed clip application might be performed more safely 4 to 6 weeks postocclusion, or later, than at 2 weeks.

Adult↗