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PubMed1986

Vascular renin-angiotensin system in two-kidney, one clip hypertensive rats.

The possible role of the renin-angiotensin system in the maintenance of hypertension in two-kidney, one clip hypertensive rats was studied. Plasma renin activity rose rapidly and markedly in association with the elevation of blood pressure and then decreased gradually, although blood pressure remained high. Renin activity in the lung, aorta, and mesenteric artery also increased with the development of hypertension and then decreased in a way similar to that of plasma renin activity at the chronic stage of hypertension. Plasma angiotensin converting enzyme activity did not change significantly until 16 weeks after unilateral renal artery clipping, whereas vascular angiotensin converting enzyme activity significantly increased at the chronic, but not the acute, stage of hypertension. In chronically renal hypertensive rats, 1-sarcosine, 8-isoleucine angiotensin II or enalapril, an angiotensin converting enzyme inhibitor, lowered the blood pressure and enalapril also lowered the angiotensin converting enzyme activity of vascular tissues. The constrictor effect of angiotensin I was greater in isolated arteries from chronically hypertensive rats than in those from age-matched normotensive rats. These results suggest that the vascular renin-angiotensin system plays an important role in the maintenance of two-kidney, one clip hypertension. Elevated vascular angiotensin converting enzyme activity appears to increase local production of angiotensin II, which results in vasoconstriction by acting directly and indirectly through adrenergic nerves on vascular smooth muscle.

Angiotensin II↗
PubMed1990

Baroreflex control of renal sympathetic nerve activity is potentiated at early phase of two-kidney, one-clip Goldblatt hypertension in conscious rabbits.

Conscious normotensive and two-kidney, one-clip Goldblatt hypertensive rabbits were studied to determine the sensitivity of the arterial baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate. The relations of the mean arterial pressure-RSNA and mean arterial pressure-heart rate were examined over a wide range of blood pressures produced by infusions of phenylephrine and nitroglycerin. The maximum slope obtained by logistic function analysis was considered to represent the baroreflex sensitivity. In the early hypertensive group (n = 8; mean arterial pressure +/- SEM, 88 +/- 2 mm Hg) on day 5 after renal clip application, the maximum slope of the mean arterial pressure-RSNA relation was -11.3 +/- 1.2, which was significantly greater than that of the sham normotensive group (-6.9 +/- 0.3, p less than 0.05). The maximum slope (-4.3 +/- 0.2) of the mean arterial pressure-RSNA relation in the late hypertensive group (n = 8; mean arterial pressure, 96 +/- 3 mm Hg) on day 21 after renal clipping was significantly smaller than that of another sham group (-7.2 +/- 0.2, p less than 0.05). In contrast to these changes in the baroreflex control of RSNA, the control of heart rate was attenuated according to the magnitude of mean arterial pressure. To elucidate the mechanisms underlying the potentiated baroreflex, the effects of endogenous neuropeptides were investigated. First, plasma concentrations of angiotensin II and arginine vasopressin that are known to affect the baroreflex were determined. Plasma concentrations of vasopressin (3.1 +/- 0.6 pg/ml) as well as of angiotensin II (34 +/- 7 pg/ml) were increased in the early hypertensive group, and the plasma vasopressin returned to a similar level to the sham group in the late hypertensive group (1.3 +/- 0.4 pg/ml). Second, to study endogenous effects of these neuropeptides on the baroreflex, the maximum slopes of the baroreflex curves during infusions of antagonists for the peptides were determined in the early hypertensive group. The maximum slope of mean arterial pressure-RSNA during intravertebral arterial [Sar1, Ala8]-angiotensin II (-16.4 +/- 1.5) was significantly greater (p less than 0.05), whereas the maximum slope during intravertebral arterial infusion of d(CH2)5Tyr(Me)arginine vasopressin (-4.7 +/- 0.5) was significantly smaller (p less than 0.05) than that during vehicle infusion (-11.3 +/- 1.2).(ABSTRACT TRUNCATED AT 400 WORDS)

Angiotensin II↗
PubMed2001

Angiotensin II AT(1A) receptor antisense lowers blood pressure in acute 2-kidney, 1-clip hypertension.

To test the effectiveness of antisense oligonucleotides targeted to the angiotensin type 1A (AT(1A)) receptor mRNA on blood pressure reduction, the 2-kidney, 1-clip (2K1C) Goldblatt model of hypertension was studied in the acute phase of hypertension, when the peripheral renin-angiotensin system is overactive. A single injection of AT(1A) receptor antisense oligodeoxynucleotides significantly reduced systolic blood pressure for a period of 8 days in 2K1C rats after clipping, from 157.5+/-5 mm Hg on day 7 to 141.3+/-3.0 mm Hg on day 15 after clipping (P<0.01). The AT(1A) receptor antisense oligonucleotide labeled with fluorescein shows that the antisense oligonucleotide at 24 hours was taken up into aorta, mesenteric artery, liver, kidney glomeruli, and medulla, remaining up to 6 days. The AT(1A) receptor number in fmol/g tissue was significantly decreased after AT(1A) receptor antisense oligonucleotide treatment in the dorsal aorta, mesenteric artery, renal cortex, and renal medulla (P<0.05) compared with that of the AT(1A) receptor-scrambled antisense oligonucleotide control-treated group. The data clearly demonstrate a prolonged antihypertensive effect of AT(1A) receptor antisense oligonucleotide in the 2K1C renovascular model of hypertension when it is administered intravenously in a single low dose (0.33 mg/kg(-1)). It also shows that the AT(1A) receptor antisense oligonucleotide is actively taken up by AT(1A) target tissues and that there is a significant decrease in receptor density. We conclude that in the acute phase of 2K1C hypertension, antisense to AT(1A) receptor decreases AT(1A) receptor density, which attenuates the vascular vasoconstrictive effects of high plasma angiotensin II levels and in the kidney elicits natriuresis. The decrease in renal AT(1A) receptor density may also lead to sodium loss and reduction of extracellular volume.

Acute Disease↗
PubMed1982

Decrease in peripheral sympathetic nervous system activity following renal denervation or unclipping in the one-kidney one-clip Goldblatt hypertensive rat.

Increased sympathetic nervous system activity has been demonstrated in established one-kidney one-clip hypertension in the rat. We have found that renal denervation in this model results in an attenuation of hypertension, unassociated with alterations in sodium or water balance or renin activity. To determine whether the depressor effect of renal denervation is associated with changes in peripheral sympathetic nervous system activity, sham operation (n = 12), renal denervation (n = 13), or unclipping (n = 13) was carried out 2 wk after the onset of one-kidney one-clip hypertension. Normotensive unine-phrectomized age- and sex-matched rats were used as controls (n = 14). Renal denervation resulted in a significant decrease in systolic blood pressure (201+/-7 to 151+/-6 mm Hg), while unclipping lowered systolic blood pressure to normotensive levels (130+/-6 mm Hg). 8 d after operation plasma norepinephrine and mean arterial pressure before and after ganglionic blockade with 30 mg/kg hexamethonium bromide were measured in conscious, unrestrained, resting animals, as indices of peripheral sympathetic nervous system activity. Plasma norepinephrine was significantly higher in hypertensive sham-operated rats (422+/-42 pg/ml) compared with normotensive controls (282+/-25 pg/ml) (P < 0.01). Both renal denervation and unclipping restored plasma norepinephrine to normal levels (273+/-22 and 294+/-24 pg/ml, respectively). Ganglionic blockade in hypertensive sham-operated animals resulted in a significantly greater decrease in mean arterial pressure than occurred in renal denervated, unclipped, or control rats. The data suggest that the depressor effect of renal denervation or unclipping in the one-kidney one-clip hypertensive rat is associated with a decrease in peripheral sympathetic nervous system activity.

Animals↗
PubMed1987

Skin clips are contraindicated when there is nickel allergy.

Four patients are described who developed generalized dermatitis following surgical wound closure with disposable skin clips. In 3 of them a vesicular palmar eczema was a prominent feature. They were found to have contact allergy to nickel, a component of the clips. If skin clips are to be used to close a surgical wound, it should be established that the patient is not allergic to nickel.

Adult↗
PubMed2002

Partially clipped intracranial aneurysm obliterated with combined stent and coil implantation.

PURPOSE: To report a case of endovascular stent placement to assist stable coil deployment in a symptomatic, wide-necked, partially clipped aneurysm. CASE REPORT: A 48-year-old woman presented for endovascular treatment of a symptomatic posterior communicating artery aneurysm remnant that was surgically clipped 10 years ago. A 3.5-mm x 12-mm balloon-expandable stent was placed across the aneurysm orifice followed by complete obliteration of the remnant with coils implanted through the stent mesh. Digital subtraction angiography documented continued patency of the arterial lumen and complete obliteration of the aneurysm at 11 months. CONCLUSIONS: Partial aneurysm clipping may assist or complicate secondary interventional procedures and interfere with correct visualization of the neck. Stent placement obviates the need for the balloon-assist method of coil embolization for wide-necked aneurysm remnants, acting as a mechanical barrier to hold the coils in a very unfavorable anatomy.

Angiography, Digital Subtraction↗
PubMed2001

Aneurysmal SAH: cognitive outcome and structural damage after clipping or coiling.

BACKGROUND: Aneurysmal subarachnoid hemorrhage (SAH) and surgical clipping of intracranial aneurysms are associated with substantial morbidity and mortality. OBJECTIVE: To compare cognitive outcome and structural damage in patients with aneurysmal SAH treated with surgical clipping or endovascular coiling. METHODS: Forty case-matched pairs of patients with aneurysmal SAH treated by surgical clipping or endovascular coiling were prospectively assessed by use of a battery of cognitive tests. Twenty-three case-matched pairs underwent MRI 1 year after the procedure. Matching was based on grade of SAH on admission, location of aneurysm, age, and premorbid IQ. RESULTS: Both groups were impaired in all cognitive domains when compared with age-matched healthy control subjects. Comparison of cognitive outcome between the two groups indicated an overall trend toward a poorer cognitive outcome in the surgical group, which achieved significance in four tests. MRI showed focal encephalomalacia exclusively in the surgical group. This group also had a significantly higher incidence of single or multiple small infarcts within the vascular territory of the aneurysm, but both groups had similar incidence of large infarcts and global ischemic damage. CONCLUSION: Endovascular treatment may cause less structural brain damage than surgery and have a more favorable cognitive outcome. However, cognitive outcome appears to be dictated primarily by the complications of SAH.

Cognition↗
PubMed1993

Emergent aneurysm clipping without angiography in the moribund patient with intracerebral hemorrhage: the use of infusion computed tomography scans.

The authors report their experience with 25 patients (mean age, 44.3 +/- 12.1 years) with an intracerebral hematoma (ICH) from a ruptured aneurysm who were emergently operated on without angiography. Instead, preoperative high-resolution infusion computed tomography (CT) scans were used to identify the aneurysm causing the hemorrhage. In all patients, the preoperative Glasgow Coma Scale score was < 5 and brain stem compression was evident. ICH was present in the frontal or temporal lobe and was often associated with intraventricular hemorrhage (n = 17) and significant (> 1 cm) midline shift (n = 18). Infusion CT scans correctly identified the aneurysm in all patients (middle cerebral artery, 18; posterior communicating artery, 2; carotid bifurcation, 3; anterior communicating artery, 2). Partial evacuation of the hematoma guided by infusion CT scan was usually required first to clip the aneurysm definitively using standard microvascular techniques. Intraoperative rupture occurred twice, and temporary clips were used on four occasions. Lobectomy (n = 8), decompressive craniotomy (n = 15), and ventriculostomy (n = 8) were required to control cerebral swelling. All patients underwent postoperative angiography to confirm aneurysm obliteration. Eleven unruptured aneurysms were subsequently identified. Nine had been predicted by infusion scan. Twelve patients survived, eight of whom were only moderately disabled and were independent at 6-months' follow-up. Of the 13 patients who died, all except one died within 4 days of admission. The authors conclude that although angiographic verification before aneurysm surgery is preferable, in the moribund patient with intracerebral hemorrhage, infusion CT scanning provides sufficient information concerning vascular anatomy to allow rational emergency craniotomy and aneurysm clipping.

Adult↗
PubMed1994

Intraoperative assessment of aneurysm clip placement by intravenous fluorescein angiography.

Clip occlusion of intracranial aneurysms can be difficult, and intraoperative misadventures are still fairly frequent. Many complications are caused by improper clip placement. Intraoperative conventional arteriography is time consuming and requires expensive image-intensifying equipment. As an alternative, we have found that the bolus intravenous administration of fluorescein produces the necessary intra-arterial dye concentration for the direct visualization of the perforating medium and large arteries in proximity to a clipped aneurysm. The technique is straightforward, requiring little additional operating time and an inexpensive set of disposable optical filters. No adverse reactions to fluorescein have been observed.

Cerebral Angiography↗
PubMed2006

The expanded endonasal approach for an endoscopic transnasal clipping and aneurysmorrhaphy of a large vertebral artery aneurysm: technical case report.

OBJECTIVE: Aneurysms of the vertebral artery are rare, comprising less than 5% of all aneurysms. They can present with subarachnoid hemorrhage, medullary compression, and cranial neuropathies. In consideration of their surrounding regional anatomy, they present a formidable surgical challenge to the neurosurgeon using traditional techniques. Recent advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions. CLINICAL PRESENTATION: We present a case of a large vertebral artery aneurysm causing mass effect on the medulla. Initial treatment consisted of endovascular trapping of the aneurysm; however, because of concerns that the remaining aneurysm and intraluminal thrombus was causing mass effect and continued brainstem compression, a decompressive procedure was required. INTERVENTION: After the endovascular trapping, the patient underwent a completely endoscopic transnasal surgical clipping and aneurysmorrhaphy. After exposure of the aneurysm, distal and proximal clips were applied transnasal, and the aneurysmorrhaphy completed using suction and ultrasonic aspiration. CONCLUSION: In consideration of their surrounding regional anatomy, aneurysms of the vertebral artery present a formidable surgical challenge to the neurosurgeon. Although endovascular techniques have proven to be extremely valuable for the treatment of these lesions, they are limited when patients have significant mass effect with brainstem compression or cranial neuropathy. Advances in endoscopic transnasal surgery have provided an additional approach for the treatment of these difficult lesions. This case report represents, to our knowledge, the first literature report of a transnasal endoscopic aneurysm clipping and thrombectomy.

Atlanto-Occipital Joint↗
PubMed1991

Changes in sodium-22 turnover and total body potassium in two-kidney, one-clip renovascular hypertension.

Changes in sodium-22 turnover and total body potassium (TBK) were studied during acute (within 2 weeks after clipping) and chronic (12-14 weeks after clipping) phases in two-kidney, one-clip (2k, 1c) hypertensive rabbits by using a whole body counter. Sodium-22 injected intravenously was eliminated more rapidly in hypertensive rabbits than in controls. The biological half-life (BHL) of sodium-22 was shorter in hypertensive rabbits during both acute (p less than 0.05) and chronic phases (p less than 0.001). A significant negative correlation was obtained between the BHL of sodium-22 and blood pressure (r = -0.588, p less than 0.05) in hypertensive rabbits. TBK decreased significantly at the chronic phase in hypertensive rabbits (p less than 0.05), while TBK showed no significant change in controls. Serum sodium and potassium did not change during the observation period. Increased plasma aldosterone concentration was observed during the acute phase in hypertensive rabbits. These results suggested that sodium retention was not a major factor in the acute and chronic phases of 2k, 1c hypertension in rabbits and that pressure natriuresis could explain, at least in part, the lack of sodium retention. Furthermore, there appears to be a derangement in the intracellular potassium metabolism which may be associated with the maintenance rather than the development of hypertension.

Aldosterone↗
PubMed1998

Role of nitric oxide in the evolution of renal ischemia in two-kidney, one-clip renovascular hypertension.

To clarify the role of nitric oxide (NO) in the pathogenesis of renovascular hypertension, we examined the effects of long-term oral administration of either the precursor substrate L-arginine or the NO synthesis inhibitor Nomega-nitro-L-arginine (L-NA) on systemic and renal hemodynamics in dogs with chronic two-kidney, one-clip (2K-1C) renovascular hypertension. Furthermore, the importance of NO in maintaining kidney function in chronic renal ischemia was evaluated. Chronic inhibition of NO production aggravated the rise in blood pressure (L-NA 117.7+/-6.8 vs. control 107.2 3.3 mmHg, p < 0.05 on day 1) and stimulated marked bradycardia (L-NA 84.9+/-3.2 vs. control 94.6+/-2.6 beats/min, p < 0.05 on day 1). These changes were associated with significant reductions in renal plasma flow (RPF, L-NA 0.03+/-0.02 vs. control 0.85+/-0.20 ml/min/kg, p < 0.01) and glomerular filtration rate (GFR, L-NA 0.02+/-0.01 vs. 0.22+/-0.05 ml/min/kg, p < 0.01) in the ischemic kidney. In contrast, in the contralateral non-clipped kidney, chronic inhibition of NO production induced a significant reduction in RPF with no significant change in GFR. Oral administration of L-arginine had no effect on the magnitude of hypertension. L-arginine significantly improved RPF (2.76+/-0.49 ml/min/kg) and GFR (0.61+/-0.08 ml/min/kg) in the ischemic kidney, whereas the elevation of RPF and GFR in the non-clipped kidney was not significant. Unilateral renal artery occlusion in these hypertensive dogs resulted in diffuse atrophic tubulointerstitial changes in the ischemic kidney. These changes were markedly aggravated by NO synthesis inhibition. On the other hand, L-arginine treatment significantly protected against the morphological changes of renal ischemia. These data show that NO plays a key role in the maintenance of renal function during the evolution of hypertension induced by chronic renal ischemia. In addition, these data demonstrate that renovascular hypertension is associated with a compensatory increase in the vasodilator function of the vascular endothelium.

Animals↗
PubMed2006

Clipping or coiling of ruptured cerebral aneurysms and shunt-dependent hydrocephalus.

BACKGROUND: Hydrocephalus may develop either early in the course of aneurysmal subarachnoid hemorrhage (SAH) or after the first 2 weeks. Because the amount of SAH is a predictor of hydrocephalus, the two available aneurysmal treatments, clipping or coiling, may lead to differences in the need for cerebrospinal fluid (CSF) diversion, as only surgery permits clot removal. METHODS: Hospital and University Hospitals Consortium (UHC) databases were used to retrieve data on all patients admitted to our hospital with aneurysmal SAH during the last 4 years. The incidence of permanent ventricular shunt (VS) according to treatment modality used was evaluated. RESULTS: One hundred eighty-eight patients were admitted with aneurysmal SAH. Coiling was performed on 48 (26%) and clipping on 135 (73.8%) patients. Fifty-six (31%) patients required CSF diversion. External ventricular drain was placed in 30 (22.2%) clipped and 13 (27.1%) coiled patients ( p = 0.5 ), and VS in 6 patients of the two treatment groups (4.4 versus 12.5%, respectively; p = 0.08). Patients requiring VS had longer UHC-expected hospital length of stay (LOS), as well as observed ICU and hospital LOS, compared to patients with temporary or no CSF diversion (24 +/- 14 versus 15 +/- 8, 20.5 +/- 9 versus 11 +/- 7, and 30 +/- 13 versus 16 +/- 11 days, respectively; p <or= 0.01). In a logistic regression model, VS was independently associated with rebleeding, external ventricular drain placement, coiling, and UHC-expected LOS (odds ratios, 95% confidence interval 12.1, 2.3 - 62.6, 6.9, 1.6 - 30, 6.25, 1.3 - 29, and 1.1, 1.02 - 1.14, respectively). CONCLUSIONS: One-third of patients admitted with aneurysmal SAH require temporary or permanent CSF diversion. Permanent shunting was found to be associated with coiling in our patient population.

Adult↗
PubMed2003

Interrupted coalescent nitinol clip versus continuous suture coronary anastomosis: a comparative endothelial function study.

BACKGROUND: A new penetrating stapled anastomotic system using nitinol microclips (Coalescent Surgical U-Clip) has been developed to facilitate the construction of compliant interrupted sutures for minimally invasive and robotic surgery as well as for conventional procedures. The purpose of this study was to determine the effect of nitinol U-Clips used for coronary anastomosis in the development of endothelial dysfunction, compared with conventional running sutures. METHODS: In a porcine model, both internal thoracic arteries were harvested, and the heart was removed. In a Krebs solution, 2 anastomoses were realized ex vivo between internal thoracic arteries and the left anterior descending artery. One was carried out with 12 Coalescent microclips, and the other used conventional running 7-0 polypropylene suture material (Prolene). Coronary rings on the anastomotic sites were then placed in organ chambers filled with oxygenated Krebs solution. Vascular reactivity studies were performed in standard organ chamber experiments. After the contraction of the coronary arteries in response to prostaglandin F2alpha, the endothelium-dependent relaxation response to bradykinin was studied. The other coronary arteries served as controls. RESULTS: There was no statistically significant difference among the groups (P >.05) in the amplitude of the contraction response to KCl and prostaglandin F2alpha. There were no statistically significant differences in endothelium-dependent relaxation response to bradykinin between the nitinol microclip group and controls, between the suture group and controls, and between the nitinol microclip and suture groups. CONCLUSIONS: Coalescent nitinol U-Clips used as anastomotic devices do not induce an endothelial dysfunction and allow a compliant anastomosis under satisfactory conditions.

Alloys↗
PubMed2000

Impaired renal blood flow autoregulation in two-kidney, one-clip hypertensive rats is caused by enhanced activity of nitric oxide.

Increases in renal perfusion pressure will induce shear stress-mediated nitric oxide (NO) release, which could oppose autoregulation of renal blood flow (RBF). Although cardiac, cerebral, and mesenteric autoregulation is enhanced during nitric oxide (NO) synthesis inhibition, this has not been reported for renal autoregulation of blood flow. In the present study, the lower limit and efficiency of RBF autoregulation (as assessed by the degree of compensation) were studied before and during NO inhibition in normotensive Sprague Dawley rats (control; n = 9) and in the non-clipped kidney of two-kidney, one-clip Goldblatt hypertensive animals (2K1C; n = 9; 3 wk; 0.25-mm silver clip). In both groups, renal autoregulation curves were obtained before and during infusion of N(G) -nitro-L-arginine (L-NNA) (bolus 1.5 mg/kg intravenously, infusion 10 microg/kg per min intravenously), using a transit-time flow probe around the left renal artery. In control rats, mean arterial pressure (MAP) increased, RBF decreased, and renal vascular resistance (RVR) increased in response to L-NNA infusion. The lower limit of autoregulation in control animals did not significantly change during L-NNA infusion (78 +/- 3 to 70 +/- 2 mmHg). The degree of compensation in these rats slightly increased during L-NNA infusion, however, this was only significant below 90 mmHg. The 2K1C rats had elevated MAP under baseline conditions. L-NNA infusion resulted in a decrease in RBF and an increase in MAP and RVR. During L-NNA infusion, RVR in 2K1C rats greatly exceeded RVR in control rats. A significant decrease was observed in the lower limit of autoregulation from 85 +/- 3 to 72 +/- 5 mmHg (P < 0.05). In the contralateral kidney of 2K1C rats, the degree of compensation was lower than in control rats under baseline conditions. L-NNA infusion resulted in significantly higher degrees of compensation compared to baseline. In conclusion, the contralateral kidney displayed a high NO dependency, as RBF greatly decreased and RVR dramatically increased in response to L-NNA infusion. The contralateral kidney of 2K1C rats exhibited impaired RBF autoregulation, which was improved by NO inhibition, as judged from a decrease in the lower limit of autoregulation and an increase in the degree of compensation. This study indicates that perfusion pressure-dependent NO release can oppose autoregulation in the kidney. However, the enhanced influence of NO on pressure-dependent RBF may facilitate the preservation of renal function in the nonclipped kidney of 2K1C rats.

Analysis of Variance↗
PubMed2002

Female sterilisations with Filshie clips: what is the risk failure? A retrospective survey of 30,000 applications.

OBJECTIVE: To assess the failure rate of Filshie clip sterilisations in Victoria, Australia. DESIGN: Retrospective study between 1994 and 1998. SETTING: All specialist gynaecologists practising in the state of Victoria, Australia. INTERVENTIONS: Questionnaires (up to three) followed by telephone calls if necessary. MAIN OUTCOME MEASURES: A response rate of 276/277 (99.6%) was obtained. All pregnancies were recorded. RESULTS: Seventy-three failures were notified from an estimated 30,000 Filshie clip sterilisations carried out in the study period. CONCLUSIONS: The estimated failure rate of Filshie clip sterilisations in the state of Victoria carried out by specialist gynaecologists was between 2 and 3 per 1000 sterilisation operations.

Constriction↗
PubMed1988

Regional blood flows and resistances in conscious one-kidney, one-clip renovascular hypertensive rats.

Three regional blood flows were measured in one-kidney, one-clip renovascular hypertensive (one-kidney hypertensive) rats with chronically implanted electromagnetic flow probe. One-kidney hypertensive rats showed about 30% greater superior mesenteric flow, about 20% greater hindquarter flow at the terminal aorta, and an almost unchanged renal flow at the clipped renal artery when compared with control rats, but the sum of the mean values of these three regional blood flows in one-kidney hypertensive rats was almost the same as that of control rats. One-kidney hypertensive rats had a higher peripheral resistance in all the investigated vascular areas. The increase in peripheral resistance of the renal area including the clipped and removed arteries was greater than that in peripheral resistance of the superior mesenteric area or hindquarter area. These findings suggest that the remaining renal area which failed to compensate for the flow deprived by uni-nephrectomy plays a role in the etiology of this kind of hypertension.

Animals↗
PubMed2004

Safety and MRI artifact evaluation at 1.5 T of metallic mounting sheath of a marking clip inadvertently deployed at stereotactic biopsy.

OBJECTIVE: The purpose of our study was to assess the MRI risk factors for the patient after an unusual case of inadvertent deployment of the mounting sheath of a metallic clip used at stereotactic breast biopsy. MATERIALS AND METHODS: We evaluated the materials for ferromagnetic properties, heating, and artifacts. RESULTS: Our analysis showed significant deflection and prominent susceptibility artifacts of the sheath at 1.5 T, although the clip itself showed no deflection and only minimal artifact. Our study shows that a device and its delivery apparatus may have significantly different ferromagnetic properties. CONCLUSION: In case of inadvertent deployment of the sheath, a delay of 6-8 weeks before MRI is recommended as a conservative approach to ensure tissue ingrowth and to minimize the chance of harm to the patient. In the case of metallic clips used for breast biopsy, caution is warranted when a portion of the device unintended for placement is introduced into the breast.

Artifacts↗