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PubMed1982

Baroreflex sensitivity changes during the reversal of Goldblatt two-kidney one-clip hypertension in rats.

The time-course of changes in baroreceptor reflex sensitivity during the reversal of Goldblatt two-kidney one-clip hypertension was studied in male Wistar rats. Groups of animals were studied before and 1, 3, 7, 14 and 25 days after removal of a left renal artery clip of 0.18 mm internal diameter. Normotensive rats of comparable ages were included as controls. Baroreflex sensitivity increased from 0.299 +/- 0.072 ms/mmHg (n = 8) in 25 day hypertensive rats to 0.657 +/- 0.155 and 0.786 +/- 0.093 ms/mmHg (n = 8) in 1 day and 3 day declipped animals respectively. Baroreflex sensitivity in the 1 day declipped rats was inversely related to the level of blood pressure. Baroreflex sensitivity is restored early when renovascular hypertension is reversed. This is unlikely to be due solely to regression of structural vascular adaptation.

Animals↗
PubMedDate not supplied

Role of renin-angiotensin and sympathetic nervous systems in the chronic phase of two-kidney, one-clip hypertension in rats.

The purpose of the present study was to examine the role of the renin-angiotensin and the sympathetic nervous systems during the chronic phase (greater than 16 weeks) of two-kidney, one-clip hypertension in conscious unrestrained rats. During this phase, the mean arterial pressure (MAP) (p less than 0.001) and plasma angiotensin II (31.9 +/- 1.5 to 125.8 +/- 19.9 pg/ml, p less than 0.005) were significantly increased as compared to normotensive group. Converting enzyme inhibition by captopril produced a significant decrease of MAP (181.2 +/- 8.2 to 140.0 +/- 5.5 mmHg, p less than 0.001). This hypotensive response was similar when aprotinin (a Kallikrein inhibitor) and captopril were infused simultaneously. Alpha 1-adrenergic receptor blockade by phenoxybenzamine (POB) significantly decreased but did not normalize MAP (179.8 +/- 12.4 to 135.8 +/- 10.4 mmHg, p less than 0.001). However, when infused after POB, captopril induced a further decrease of MAP to 86.7 +/- 9.4 mmHg (p less than 0.001). This MAP level was not different from that found in normotensive rats after infusion of the two drugs (83.2 +/- 5.3 mmHg). These results suggest that both the renin-angiotensin system and the sympathetic nervous system, by activating peripheral alpha 1-adrenergic receptors, maintain the high blood pressure during the chronic phase (greater than 16 weeks) of two-kidney, one-clip hypertension in conscious rats.

Angiotensin II↗
PubMed1990

Thiazide diuretic receptors in spontaneously hypertensive rats and 2-kidney 1-clip hypertensive rats.

Thiazide diuretic receptor density was assessed in kidneys from spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats by measuring hydroflumethiazide-displaceable 3H-metolazone binding to renal membranes in vitro. Renal thiazide receptor density was not significantly different in 4 week old SHR and WKY rats, but was significantly increased by 20%-40% in 14-49 week old SHRs compared to WKY rats. Affinity of receptors for 3H-metolazone did not differ between SHRs and WKY rats at any age. In WKY rats with 2 kidney-1 clip (2K-1C) hypertension, thiazide receptor density was not significantly different in either clipped or unclipped kidneys from sham-operated controls. Thus, increased renal thiazide receptor density occurs in SHRs along with the development of hypertension and does not appear to be secondary to increased renal perfusion pressure. This increase may reflect altered hormonal or ionic input to the distal tubule and may contribute to elevated sodium reabsorption in this segment in the SHR.

Animals↗
PubMed1991

Role of baroreceptor resetting in the tachycardia observed during the onset of one-kidney, one clip hypertension.

A previous study from our laboratory demonstrated the occurrence of transient tachycardia during the onset of one-kidney, one clip (1K1C) hypertension in conscious rats. In the present study, using electroneurographic recordings in anesthetized rats, we investigated the time course of baroreceptor resetting at the onset (3, 7, 14 and 21 days) of 1K-1C hypertension. No significant difference between the diastolic pressure and the systolic threshold pressure for baroreceptor activation was detected in normotensive control rats and hypertensive rats 3, 7, 14 and 21 days after clipping. These data indicate that the baroreceptors were completely reset to the hypertensive levels during the periods studied. The data also suggest that baroreceptor resetting may play a facilitating role in the onset of tachycardia and the development of 1K1C hypertension in the conscious animal model.

Animals↗
PubMed2005

Combined surgical and endovascular treatment of a recurrent A3-A3 junction aneurysm unsuitable for stand-alone clip ligation or coil occlusion. Technical note.

Recurrent aneurysms of the anterior circulation that are distal to the anterior communicating artery (ACoA) but proximal to the callosomarginal-pericallosal bifurcation can pose a treatment challenge. The authors present one such case, in which the patient was treated with pericallosal artery-pericallosal artery (PerA-PerA) side-to-side bypass, followed by endovascular obliteration of the proximal A2 parent vessel. This patient, in whom an ACoA aneurysm had been treated with clip ligation 5 years previously, presented with a new, mid-A2, right-sided aneurysm with the outflow artery arising from the dome of the lesion. The treatment plan included two steps: an interhemispheric transcallosal approach for PerA-PerA side-to-side anastomosis; and endovascular coil embolization of the right A2 branch feeding the aneurysm. Postprocedure angiography demonstrated no ipsilateral aneurysm filling and excellent bilateral distal outflow from the anterior cerebral artery (ACA). The use of PerA-PerA side-to-side bypass for the treatment of an ACA aneurysm, followed by parent vessel occlusion, offers an elegant solution for the treatment of A2 aneurysms that are not amenable to stand-alone clip ligation or coil occlusion. Such combined methods are invaluable in the management of complex cerebral aneurysms.

Cerebral Arteries↗
PubMed2006

The transition from hunterian ligation to intracranial aneurysm clips: a historical perspective.

The description of cerebral aneurysms dates back to antiquity. Little was known, however, about the pathological mechanisms of aneurysm formation and treatment options for this disease until 200 years ago. The modern era of aneurysm treatment began with the hunterian ligation of the proximal artery, followed by clip and coil occlusion. In this article, the authors describe the transition from conservative therapy to internal carotid artery (ICA) ligation and gradual occlusion of the ICA to the direct placement of clips on aneurysms. The driving forces and rationale behind each major advancement are summarized, and the authors attempt to predict what these innovations mean for the future of intracranial aneurysm management.

History, 20th Century↗
PubMed1976

Comparative study of the pressure of various aneurysm clips.

Comparative study of the pressure and the resistance to slippage of several aneurysm clips was done. Knowledge of the physical characteristics of various clips, such as the pressure, maximum opening angle, and width and thickness of the blade is essential for their proper use.

Animals↗
PubMed1977

Stereotaxic clipping of arterial aneurysms and arteriovenous malformations.

In carefully selected cases of arterial aneurysms and deep-seated arteriovenous malformations (AVM), when direct attack may be dangerous or impossible, the authors advocate stereotaxic clipping. A special device and technique for its application are described. The instrument is introduced through a trephine opening and clipping is monitored by angiography. Successful results have been obtained in 10 operations performed on eight patients, three of whom had arterial aneurysms (two internal carotid and one anterior cerebral-anterior communicating) and five with AVM's.

Adolescent↗
PubMed1982

Failure of a Heifetz aneurysm clip.

A 16-year-old girl died from an acute subarachnoid hemorrhage following the fracture of a blade of a Heifetz aneurysm clip. The clip was manufactured from 17-7PH steel, which on metallurgical testing was found to be highly sensitive to intergranular corrosion. The fracture mechanism was stress corrosion, brought on by the combination of a stress load, an electrolytic environment, and a susceptible steel.

Adolescent↗
PubMed1984

Characteristics and use of ultra-long aneurysm clips.

Ultra-long aneurysm clips, 21 to 40 mm in length, are described, and their characteristics and application delineated. These clips have been used in 30 procedures for various kinds of aneurysms. They are useful not only for wide-necked and giant aneurysms but also for deeply located aneurysms such as those on the vertebrobasilar artery.

Adult↗
PubMed1985

Implications of nimodipine prophylaxis of cerebral vasospasm on anesthetic management during intracranial aneurysm clipping.

Nimodipine, a calcium entry blocking agent similar in structure to nifedipine but with selective cerebrovascular dilating effects, has potential use in the therapy and prevention of cerebral vasospasm after intracranial hemorrhage. The authors summarize the effects of calcium entry blockers, review the pharmacology of nimodipine, and discuss both the known and possible interactions of oral nimodipine with physical and pharmacological interventions that neuroanesthesiologists employ for patients with cerebral vasospasm during craniotomy for aneurysm clipping. In a series of 26 patients undergoing aneurysm clipping, the authors found that intraoperative blood pressure tended to be reduced by nimodipine. Although the number of patients was limited by the fact that they were enrolled in a multi-center nimodipine aneurysm study and thus had to meet the criteria for that study, it is concluded that prophylaxis of cerebral vasospasm with nimodipine in patients with ruptured intracranial aneurysm results only in a favorable tendency toward lower systemic blood pressure during craniotomy.

Anesthesia↗
PubMed1986

Clip-grafts in microvascular decompression of the posterior fossa. Technical note.

A method is described for the protection of the trigeminal root from recurrent vascular irritation or compression after posterior fossa microvascular decompression. A vascular clip-graft, using a Sundt clip of suitable size, is applied to the sensory root of the trigeminal nerve. The technique has proven safe and effective in a series of nine patients followed for up to 28 months.

Aged↗
PubMed1988

Symptomatic arterial luminal narrowing presenting months after subarachnoid hemorrhage and aneurysm clipping.

The authors describe three cases of clinical cerebral ischemia associated with angiographic evidence of cerebral arterial luminal narrowing presenting 7, 14, and 52 weeks after subarachnoid hemorrhage (SAH) and aneurysm clipping. Delayed vasospasm, in its usual time setting 1 or 2 weeks after hemorrhage, did not occur symptomatically in these patients. No evidence for aneurysm clip migration or rebleed was present. All patients responded favorably to volume expansion and elevation of blood pressure. This unusual occurrence of a very delayed vasospasm may further the understanding of the vasospastic process. The symptomatic onset of arterial luminal narrowing months after SAH may suggest that a proliferative vasculopathy more accurately explains the observed vessel narrowing, rather than conventional active constriction of vascular smooth muscle.

Adult↗
PubMed1989

Evolution of the crossed-action intracranial aneurysm clip. Technical note.

The helical coiled-spring aneurysm clip with crossed legs evolved from clips designed by Mayfield and Scoville. The problems encountered during its development stimulated an evaluation of metals used in neurosurgery, the creation of implant standards, and the use of metals with greater strength and tissue compatibility; these metals later proved to be safe during magnetic resonance imaging.

Intracranial Aneurysm↗
PubMed1992

Rebleeding from vertebral artery dissection after proximal clipping. Case report.

The authors present the case of a patient with vertebral artery dissection that rebled after being treated by proximal clipping. This is the second report of such a case. The results indicated that proximal clipping is not free from the risk of rebleeding, and a better alternative surgical technique should always be sought when treating vertebral artery dissections.

Adult↗
PubMed1994

Direct clipping of basilar trunk aneurysms using temporary balloon occlusion.

In the surgical treatment of basilar trunk aneurysms, there is still considerable technical difficulty in gaining both proximal artery control and a sufficient operative field. The authors describe their experience in five patients with basilar trunk aneurysms treated using temporary balloon occlusion and intraoperative digital subtraction angiography. With the patient under general anesthesia, a heparinized angiography catheter was guided into the dominant vertebral artery by means of the Seldinger technique. A silicone balloon catheter was introduced coaxially through the angiography catheter to the basilar artery just proximal to the aneurysm. The balloon was inflated tentatively to evaluate the appropriate inflation volume, then the balloon catheter was withdrawn back into the angiography catheter to prevent thrombus formation. After exposure of the aneurysm, the occlusion balloon was advanced again and inflated temporarily within the basilar artery to prevent premature rupture and to facilitate dissection of the aneurysm. The mean duration of temporary balloon occlusion was 22 minutes. There were no patients with postoperative deficits attributable to the temporary occlusion. The results of aneurysm clip placement were confirmed by intraoperative digital subtraction angiography immediately after clipping. No patient suffered from distal embolism or other complications related to vessel catheterization. From this experience, it is concluded that this intraoperative endovascular technique can contribute to the success of surgery for complex cerebral aneurysms, particularly for basilar trunk aneurysms in which proximal vascular control is difficult.

Adult↗