Conformability and Efficacy of the Zenith Spiral Z Leg Compared with the Zenith Flex Leg in Endovascular Abdominal Aortic Aneurysm Repair.

BACKGROUND: The aim of this study is to compare the outcome of endovascular abdominal aortic aneurysm repair (EVAR) using the Zenith® Spiral Z abdominal aortic aneurysm iliac leg (ZSLE) versus the Zenith® Flex abdominal aortic aneurysm iliac leg (TFLE). METHODS: Patients undergoing EVAR using TFLE or ZSLE between October 2009 and December 2017 were retrospectively reviewed. Clinical end points were freedom from limb-related complications and change in arterial tortuosity indexes. Limb-related complication was defined as limb stenosis or occlusion, stent kink, stent disconnection, and type 1b endoleak. Tortuosity indexes were measured on the preoperative and postoperative computed tomography and compared. RESULTS: A total of 56 patients (11 female, average age 78.5 ± 5.5 years), 111 limbs, were enrolled. One patient was treated using aortouni-iliac device. TFLE was deployed in 43 limbs (22 patients) and ZSLE in 68 limbs (34 patients). Average follow-up was 43.6 ± 27.6 months. During follow-up, 8 limb-related complications occurred in the TFLE group and 2 in the ZSLE group. Freedom from limb-related complications at 3 years was 84.4% in the TFLE group and 96.1% in the ZSLE group (P = 0.039). There was no statistically significant difference between the TFLE and the ZSLE group in the aortoiliac tortuosity change (TFLE versus ZSLE -6.1 ± 5.8 vs. -4.9 ± 6.4, P = 0.324). However, there was significance in the iliac tortuosity change (-7.4 ± 11.7 vs. -3.0 ± 7.9, P = 0.022). CONCLUSIONS: Spiral Z leg showed less occurrence of limb-related complications and less iliac artery tortuosity index change compared to Zenith Flex leg. The spiral Z leg provided better conformability as a stent-graft limb.

Association Between Optic Nerve Head Blood Flow Measured Using Laser Speckle Flowgraphy and Radial Arterial Pressure During Aortic Arch Surgery.

OBJECTIVE: This study was designed to investigate the association between ocular blood flow measured using laser speckle flowgraphy (LSFG) and radial arterial pressure during aortic arch surgery. DESIGN: A prospective study. SETTING: A single university hospital. PARTICIPANTS: This study included 24 patients undergoing aortic arch surgery with cardiopulmonary bypass (CPB) using antegrade selective cerebral perfusion (SCP). INTERVENTIONS: Measurement of optic nerve head blood flow using LSFG and radial arterial pressure via a catheter in the radial artery METHODS AND MAIN RESULTS: Antegrade SCP was managed with 24℃ and 40-to-60 mmHg at the right radial artery, which usually corresponds to a flow rate of 10 mL/kg/min. Optic nerve head blood flow using LSFG and radial arterial blood pressure were evaluated simultaneously at the right side and recorded at the following 4 points: after the induction of anesthesia (phase 1), after the beginning of CPB (phase 2), after the beginning of antegrade SCP (phase 3), and after cessation of CPB (phase 4). A moderate positive correlation between %change of mean blur rate in the optic nerve head measured using LSFG and %change of radial mean arterial pressure was identified (r = 0.604, p < 0.001). Bland-Altman analysis showed that the bias (mean difference) was -1.2% (95% limits of agreement -47.4% to 45.0%), indicating good agreement between %changes of the values recorded using the 2 measurements. CONCLUSIONS: Intraoperative monitoring of optic nerve head blood flow using LSFG can be used as an additional cerebral perfusion parameter during aortic arch surgery with CPB using antegrade SCP.

Ocular Blood Flow Measured Using Laser Speckle Flowgraphy During Aortic Arch Surgery With Antegrade Selective Cerebral Perfusion.

OBJECTIVE: The objective of this study was to evaluate the validity of ocular blood flow measured using laser speckle flowgraphy (LSFG) for the assessment of cerebral perfusion during aortic arch surgery. DESIGN: A prospective study. SETTING: A single university hospital. PARTICIPANTS: The study included 17 patients undergoing aortic arch surgery with cardiopulmonary bypass (CPB) using antegrade selective cerebral perfusion (ASCP). INTERVENTIONS: Measurement of ocular blood flow using LSFG. MEASUREMENTS AND MAIN RESULTS: Measurement of ocular perfusion that is supplied mainly from the ophthalmic artery might be useful as an indicator of cerebral blood flow because the ophthalmic artery is the first branch of the internal carotid artery. Recently, LSFG has been developed for noncontact estimation of ocular perfusion using the laser speckle phenomenon. In this study, the LSFG system was used to measure blood flow in the optic nerve head during aortic arch surgery with CPB using ASCP. The blood flow in the optic nerve head during ASCP was statistically significantly reduced by 40.6% compared with the baseline value after anesthetic induction. CONCLUSIONS: Ocular blood flow measured using LSFG showed favorable validity for assessment of cerebral perfusion during aortic arch surgery with ASCP.

Experimental use of crosslinked gelatin glue for arterial hemostasis in cardiovascular surgery.

BACKGROUND: Anastomotic needle hole bleeding is a frequently encountered problem in cardiovascular surgeries. OBJECTIVE: To examine the feasibility of crosslinked gelatin glue as an anastomotic needle hole sealant in comparison with fibrin glue. METHODS: The in vitro burst water pressures were measured for gelatin and fibrin glue sealed needle holes of expanded polytetrafluoroethylene (ePTFE) or collagen coated woven polyester grafts. For in vivo investigations, abdominal aorta-ePTFE graft anastomoses of heparinized beagle dogs were sealed by gelatin or fibrin glue and hemostatic efficacy was judged. The implanted sites were re-examined 4 weeks postoperatively. RESULTS: The in vitro burst water pressures of gelatin glue sealed needle holes of both grafts were higher than those sealed by fibrin glue. For in vivo canine studies, hemostasis was successful for all gelatin glue applied suture lines, but not two out of three fibrin glue treated sites when 3-0 polypropylene suture was employed. Although adhesions of surrounding tissues were intense for all sites 4 weeks postoperatively, inflammation was more severe for the fibrin glue group compared to those of gelatin glue. CONCLUSIONS: Gelatin glue was found to be an effective and safe sealant for accomplishing hemostasis of anastomotic needle holes of vascular grafts.

Clinical outcomes of thoracic endovascular aneurysm repair using commercially available fenestrated stent graft (Najuta endograft).

OBJECTIVE: Thoracic endovascular aneurysm repair (TEVAR) for the aortic arch aneurysm is challenging because of its curved anatomic configuration and the presence of the supra-aortic branches. The Najuta fenestrated endograft (Kawasumi Laboratories, Inc, Tokyo, Japan) was developed to treat aortic arch diseases, offering maximal proximal landing length while preserving the blood flow to the supra-aortic branches. We evaluated the perioperative and midterm outcomes of this fenestrated endograft. METHODS: Between July 2007 and July 2013, 32 patients were treated with the Najuta endograft at three vascular centers. The mean age of the patients was 74.5 ± 9.8 years (23 patients were men). Technical success, complication, overall survival rate, freedom from aneurysm-related death, secondary intervention, aneurysm enlargement, device migration, and patency of supra-aortic branches were investigated retrospectively. RESULTS: The median follow-up period was 2.5 years (range, 0.2-6.2 years). Seventy-one supra-aortic vessels (30 brachiocephalic arteries, 31 left common carotid arteries, 10 left subclavian arteries) were planned to be preserved with fenestrations. Technical success rate was 91% (29 of 32; three type I endoleaks were seen), and five perioperative complications (two Stanford A dissections, one cerebral infarction, one celiac artery obstruction, one spinal cord ischemia) were recognized. Perioperative death was not observed. Overall survival rate and rate of freedom from aneurysm-related death at 3 years were 67% and 97%, respectively. The rate of freedom from secondary intervention and the rate of freedom from aneurysm enlargement at 3 years were 84% and 85%, respectively. Device migration was not observed. There were two branch (left carotid artery and left subclavian artery) occlusions at 2 weeks after TEVAR due to the endograft's infolding. No other branch occlusion was seen in this follow-up period. As a result, the patency rate of the supra-aortic branch was 97% at 3 years. CONCLUSIONS: The perioperative and 3-year outcomes of TEVAR using the Najuta precurved, fenestrated endograft demonstrated high freedom from aneurysm enlargement and patency rates of the supra-aortic branches.

Gelatin sealing sheet for arterial hemostasis and anti-adhesion in vascular surgery: a dog model study.

BACKGROUND: The bilayer gelatin sealing sheet was developed as a safe, effective, easy-to-handle and low-cost hemostatic agent. OBJECTIVE: To examine the feasibility of gelatin sealing sheets using a canine arterial hemorrhage model. METHODS: In vivo degradation of gelatin sealing sheets was examined by implanting subcutaneously in rats. For the hemostatic and anti-adhesion efficacy investigations, femoral arteries of dogs were pricked with syringe needle to make a small hole and a gelatin (i.e. experimental group) or fibrin glue sealing sheet (i.e. control group) was applied on the hole to stop bleeding (n=8). After discontinuation of the bleeding, the skin incisions were closed and re-examined 4 weeks postoperatively. RESULTS: From the degradation study, 4 h thermally treated gelatin sheet which degraded within 3 weeks in vivo was chosen for the further hemostatic study. In all cases of gelatin and fibrin glue sealing sheets, bleeding from the needle hole on canine femoral arteries was effectively stopped. Postoperative adhesions and inflammation at the site in the experimental group were significantly less than those in the control group (P<0.01 for adhesion scores). CONCLUSIONS: The gelatin sealing sheet was found to be as effective as the fibrin glue sealing sheet as a surgical hemostatic agent, and more effective in preventing postoperative adhesions.

Aortic valve replacement in a patient with left ventricular noncompaction.

Left ventricular noncompaction is a rare cardiac pathology that results from an arrest in endomyocardial development in early embryogenesis. With great advances in imaging modalities, this pathological entity has been noted not only in the pediatric population but also in adults. Herein we report the case of a 62-year-old woman who successfully underwent aortic valve replacement for aortic regurgitation complicated by left ventricular noncompaction.

[An operative case of a chronic traumatic thoracic aortic aneurysm 16 years after a jet skiing crash; report of a case].

Injury of the thoracic aorta following a major blunt trauma to the chest occurs most frequently at the aortic isthmus and more than 80% of such patients die within 1st 30 minutes. However, less than 5% of patients survive and later develop chronic thoracic aortic aneurysm (TAA). Usually, most cases of chronic traumatic TAA have no symptoms for a long time after an accident. We report a case of successful repair for a chronic traumatic TAA 16 years after a jet skiing crash. A 37-year-old woman complained of left chest pain, back pain, and cough. A computed tomography showed a descending TAA, which was 5 cm in a maximum diameter. The final diagnosis was chronic traumatic TAA. Thoracic endovascular aortic repair (TEVAR) or graft replacement was considered as an operative procedure. We performed graft replacement to avoid complications of TEVAR, considering her small external iliac arteries.

A decade of outcomes and predictors of sac enlargement after endovascular abdominal aortic aneurysm repair using zenith endografts in a Japanese population.

PURPOSE: To present 10-year outcomes and risk factors for sac enlargement after endovascular aneurysm repair (EVAR) using the Zenith AAA Endovascular Graft (Cook, Inc, Bloomington, Indiana) in a Japanese population. MATERIAL AND METHODS: During the period 1999-2011, 127 patients underwent elective EVAR using Zenith endografts at a single institution. A retrospective investigation looked at initial rates of technical success and complications, 10-year rate of freedom from all-cause and aneurysm-related mortality, freedom from secondary intervention and sac enlargement, and risk factors for second intervention and sac enlargement. RESULTS: The median age of the patients was 78 years, and the median follow-up time was 43 months. The initial technical success rate was 98.4% (125 of 127 patients). Major adverse events occurred in 7 of 127 (5.5%) patients. Rates of freedom from all-cause and aneurysm-related mortality at 1, 3, 5, and 10 years were 95%, 87%, 77%, and 39% (all-cause mortality) and 100%, 100%, 99%, and 93% (aneurysm-related mortality). Rates of freedom from secondary intervention at 1, 3, 5, and 10 years were 97%, 91%, 88%, and 70%. Rates of primary freedom from sac enlargement at 1, 3, 5, and 10 years were 99%, 87%, 75%, and 67%. Multivariate analysis revealed aneurysm sac diameter as an independent risk factor for a secondary intervention. Preoperative sac diameter combined with an angulated short (AS) proximal neck was a risk factor for sac enlargement. CONCLUSIONS: The 10-year results of EVAR using Zenith endografts in a Japanese population were comparable to results from Western countries. Larger aneurysms and AS neck were predictors of sac enlargement after EVAR.

Technical tips and procedural steps in endovascular aortic aneurysm repair with concomitant recanalization of iliac artery occlusions.

PURPOSE: The goal of this paper is to describe our technical strategy and procedural steps for endovascular aneurysm repair (EVAR) when performed with concomitant recanalization of the iliac artery occlusion. MATERIALS AND METHODS: Three octogenarians having abdominal aortic aneurysm (AAA)/common iliac artery aneurysms (CIAA) with unilateral external iliac artery (EIA) occlusion underwent EVAR with recanalization of the occluded iliac arteries. Crossing the iliac artery occlusions was attempted in a retrograde approach using a 0.035 inch-hydrophilic guidewire. After passage of a guidewire, predilation was performed using 6mm balloon. Then a 12-Fr sheath was advanced via the occluded EIA for contralateral iliac limb delivery. Internal iliac artery embolization was subsequently performed as needed. A self-expanding stent was then placed in the occluded EIA after EVAR. RESULTS: Recanalization of the EIA occlusion, followed by stentgraft delivery through the occlusion and EVAR, was successfully performed in all three patients. Penetration of the occluded EIA was successfully achieved only by retrograde approach in two patients, and by bidirectional approach in the other patient. No perioperative complication or death occurred. Postoperative CT showed no type I or III endoleaks in the aneurysms and patent iliac arteries in all patients. CONCLUSIONS: Total endovascular repairs were successfully performed for three patients with AAA and concomitant unilateral EIA occlusions. The proposed steps described in this report might reduce the complication rate and enhance the technical success rate associated with this procedure.

Catheter-based bailout techniques for an interrupted deployment of the excluder endograft due to broken deployment string.

In this report we describe catheter-based bailout techniques for when the distal end of the ipsilateral leg of an Excluder endograft has remained undeployed due to a broken deployment string. We attempted to advance a percutaneous transluminal angioplasty (PTA) balloon into an undeployed leg via the brachial artery, but were unable to do so. The delivery catheter was then pulled out through the undeployed leg while the main body was supported by a dilated touch-up balloon to prevent stent graft migration, which subsequently enabled insertion of the balloon via the ipsilateral femoral artery. Complete deployment was accomplished by balloon dilation. Although this is situation is extremely rare, it should be recognized and catheter-based strategies should be known for dealing with this complication.

Isolated dissecting aneurysm of the brachiocephalic artery associated with contained rupture.

A 79-year-old man with no history of trauma complained of a sudden onset of headache and backache. Computed tomography showed an isolated dissecting aneurysm 4 cm in diameter associated with contained rupture at the takeoff region of the brachiocephalic artery. Surgery was performed on an emergent basis. The proximal aortic arch was successfully replaced using antegrade selective cerebral perfusion. The patient was easily weaned from cardiopulmonary bypass and recovered uneventfully.

Assessment of intraoperative motor evoked potentials for predicting postoperative paraplegia in thoracic and thoracoabdominal aortic aneurysm repair.

PURPOSE: Monitoring motor evoked potentials (MEPs) has been recognized as a highly reliable method to detect intraoperative spinal cord ischemia (SCI) in aortic repair. However, the data regarding the sensitivity and specificity of MEPs for predicting postoperative paraplegia are limited. We retrospectively assessed the value of intraoperative MEP amplitudes for predicting postoperative paraplegia. METHODS: The medical records of 44 patients were reviewed. A train-of-five stimulation was delivered to C3-C4, and MEPs were recorded from the abductor pollicis brevis and the tibialis anterior muscles. The cutoff point for detecting SCI was set at 75% decrease of the baseline MEP. Receiver operating characteristic curves were applied at various cutoff points. RESULTS: Three patients (6.8%) had postoperative paraplegia. The minimum MEP during surgery had 100% sensitivity and 64.9% specificity in predicting paraplegia, and the MEP at the end of surgery had 66.7% sensitivity and 78.0% specificity in predicting paraplegia: only 1 patient, who had borderline paraplegia (right monoparesis), showed a false-negative result. Receiver operating characteristic curves indicated that adequate cutoff points for the minimum MEP during surgery and for the MEP amplitude at the end of surgery were a 75-90% decrease and a 64-75% decrease of the baseline MEP, respectively. CONCLUSION: Monitoring MEPs had relatively high sensitivity and acceptable specificity, with the cutoff point set at 75% decrease of the baseline MEP, for predicting paraplegia and paraparesis. Because of the small sample in our study, further investigations would be necessary to investigate an adequate cutoff point that could predict postoperative paraplegia.

Initial experience of branched endovascular graft for abdominal aortic aneurysm with complex anatomy of proximal neck: planning and technical considerations.

The purpose of this report was to demonstrate initial Japanese cases of abdominal aortic aneurysm (AAA) with complex anatomy of proximal neck treated using a Zenith fenestrated endograft with branched endovascular technique and to describe the device's design and technical considerations. Planning and sizing of endografts were performed using high-resolution computed tomography on a three-dimensional workstation. Branched endograft technique combined with reinforced fenestrated device and balloon-expandable stent graft was used in two patients because of challenging morphology for the fenestrated device with a bare stent. Successful exclusion of the aneurysm sac was achieved in both patients with antegrade perfusion in incorporated visceral vessels. Endovascular repair using a fenestrated device with graft material incorporating the visceral arteries is feasible. The combination of the reinforced fenestration and the balloon-expandable stent graft can provide an adequate sealing effect for the compromised anatomy. Initial and midterm results are reported with further follow-up and patient accrual.

[Current status and future of TEVAR for descending thoracic aortic aneurysm].

As a new option for treatment of thoracic aortic aneurysm, thoracic endovascular aneurysm repair (TEVAR) has become more popular recently in Japan, because TEVAR is less invasive and TAG and Tallent are approved as a commercially available device for descending thoracic aorta The results of TEVAR showed more favorable compared to open surgery. Incidence of paraplegia after TEVAR is lower than that of open surgery. However we performed spinal cord drainage to avoid paraplegia in patients with history of the aortic aneurysm repair or long segmental coverage with stent graft. It has higher risk of injury to the iliac artery compared to EVAR, and in patients with small iliac artery and/or severe calcified artery, iliac conduit should be made before TEVAR. To expand the indication of TEAVR and to obtain better outcome, team approach with borderless and improvement of devices should be required. TEAVR will become more predominant and safer treatment in the future.

Accuracy of centerline of flow measurement for sizing of the Zenith AAA endovascular graft and predictive factor for risk of inadequate sizing.

The purpose of this study was to evaluate the accuracy of centerline of flow (CLF) measurement for precise sizing of the Zenith AAA endovascular graft (Zenith) and to identify predictive factors of risk of inadequate endograft sizing. We analyzed 42 consecutive patients treated using the Zenith with pre- and postoperative multidetector CT between 2001 and 2007. Endograft sizing was retrospectively performed using CLF on a three-dimensional workstation. The following parameters were investigated: (a) change in distance from lowest renal artery to hypogastric artery between CLF on preoperative CT (CLFp) and CLF of graft path on postoperative CT (CLFg); (b) supposed success rate of adequate endograft length selection; and (c) predictive factors for significant alteration (>10 mm) between CLFp and CLFg. Median change in distance from lowest renal artery to hypogastric artery was 4 mm. CLFg was >10 mm shorter than CLFp in 10 of 84 limbs (12%). Multivariate analysis demonstrated tortuosity index (TI) of infrarenal abdominal aorta (p = 0.019), aneurysm diameter (p = 0.035), and ipsilateral side of the main body insertion (p = 0.042) as predictive factors of significant alteration between CLFp and CLFg. Adequate endograft length selection was achieved in 39 of 42 cases (93%). All three inadequate endograft length selections were associated with tortuous aorta (TI > 20 mm). In conclusion, distance calculations based on CLF measurement provided accurate length selection of the Zenith in the majority of cases. TI, aneurysm diameter, and ipsilateral side were predictive factors for significant alteration. The CLF and aortic measurements including the TI may allow for improved sizing for Zenith placements.

Impact of 3-dimensional-computed tomography workstation for precise planning of endovascular aneurysm repair.

BACKGROUND: Compared with open surgery, imaging is considered to be important for planning and device selection of endovascular aneurysm repair (EVAR). The present study evaluated the usefulness of a 3-dimensional (3D)-computed tomography (CT) workstation in planning EVAR. METHODS AND RESULTS: A prospective study was conducted in 8 patients who underwent EVAR using Zenith endograft between February and August 2007. Endograft size and optimized deployment projection were decided using a 3D-CT workstation. The primary endpoint was defined as successful deployment of a same size endograft as preoperatively selected without type I or III endoleak or inadvertent arterial occlusion. The following parameters were investigated: (a) incidence of use of an alternative endograft; (b) prevalence of type I or III endoleak; and (c) distance from lowest renal artery to tip of graft. Successful deployment of endograft was achieved in all 8 patients. Use of alternative endograft or type I or III endoleak was not detected in 8 patients. Distance from the lowest renal artery to the tip of the graft was 2.8mm. CONCLUSIONS: Assessment using a 3D-CT workstation appears to allow accurate endograft selection and precise deployment of the Zenith endograft without type I or III endoleak, even in institutes with a small number of patients.

Midterm outcomes of endovascular repair with the zenith endovascular graft: does the ipsilateral limb level of the main body of the graft affect outcome?

PURPOSE: To clarify whether the ipsilateral limb level of the main body of the graft above or below the aortic bifurcation affects midterm outcomes of endovascular abdominal aortic aneurysm repair (EVAR) with the Zenith abdominal aortic aneurysm endovascular graft. MATERIALS AND METHODS: The authors analyzed 70 consecutive patients treated with the Zenith endograft between 1999 and 2006 with a retrospective review of prospectively collected clinical and imaging data. Patients were divided into two groups--those in whom the ipsilateral limb of the main body was placed above the aortic bifurcation (group A, n = 34) and those in whom the ipsilateral limb of the main body was placed below the aortic bifurcation (group B, n = 36). The frequency of sac enlargement, late type I or III endoleak, and secondary intervention and freedom from major adverse events associated with an aneurysm were compared. RESULTS: The median follow-up was 38 months (range, 1-84 months). The frequency of sac enlargement was 12% (four of 34 patients) in group A and 8% (three of 36 patients, P = .94) in group B. The frequency of late type I or III endoleak was 9% (three of 34 patients) in group A and 6% (two of 36 patients, P = .95) in group B. The frequency of secondary intervention was 15% (five of 34 patients) in group A and 6% (two of 36 patients, P = .38) in group B. Rate of freedom from major adverse events at 60-month follow-up was 62% in group A and 80% in group B (P = .54). CONCLUSIONS: Placement of the ipsilateral limb of the main body above the aortic bifurcation should be considered as one option in patients with an inadequate iliac anatomy at this time. Further follow-up and accumulation of patients will help clarify outcomes with regard to differences in ipsilateral limb level.

Deteriorating consumptive coagulopathy with type III endoleak following endovascular repair for abdominal aortic aneurysm associated with liver cirrhosis.

PURPOSE: To report a case of deteriorating consumptive coagulopathy with type III endoleak following endovascular aneurysm repair (EVAR) of the abdominal aorta associated with liver cirrhosis. CASE REPORT: A 72-year-old man with liver cirrhosis developed type III endoleak following EVAR. Spontaneous intramuscular hematoma developed due to deteriorating consumptive coagulopathy induced by type III endoleak and liver dysfunction. Although additional EVAR was performed at 52 months after primary EVAR, the patient died due to multiorgan failure and multifocal hematoma of the muscles and subserosa. CONCLUSION: EVAR for patients with liver dysfunction and coagulopathy should be considered with great caution. We suggest that prompt and adequate treatment using an endovascular technique or surgical repair should be performed for patients with liver dysfunction, coagulopathy, and turbulent endoleak, even if the coagulopathies are worse compared to before EVAR.

[Surgical repair of a large isolated internal iliac artery aneurysm presenting with acute renal failure. A case report].

A 71-year-old man was suffering from a large right internal iliac artery aneurysm (rt. IIAA) associated with acute renal failure secondary to bilateral hydronephrosis. Immediately after admission, we performed resection of the rt. IIAA and right common iliac artery-external iliac artery bypass. Postoperative recovery was uneventful and renal function improved. We should consider that a large isolated IIAA may uncommonly cause acute renal failure secondary to hydronephrosis. Expeditious surgical intervention may provide a complete recovery from acute renal failure.