Risk of renal failure after major angiography

Contrast Induced Acute Kidney Injury and Direct Cytotoxicity of Iodinated Radiocontrast Media on Renal Proximal Tubule Cells

The administration of intravenous iodinated radiocontrast media (RCM) to visualize internal structures during diagnostic procedures has increased exponentially since their first use in 1928. A serious side effect of RCM exposure is contrast-induced acute kidney injury (CI-AKI), which is defined as an abrupt and prolonged decline in renal function occurring 48-72 hours after injection. Multiple attempts have been made to decrease the toxicity of RCM by altering ionic strength and osmolarity, yet there is little evidence to substantiate that a specific RCM is superior in avoiding CI-AKI. RCM-associated kidney dysfunction is largely attributed to alterations in renal hemodynamics, specifically renal vasoconstriction; however, numerous studies indicate direct cytotoxicity as a source of epithelial damage. Exposure of in vitro renal proximal tubule cells to RCM has been shown to affect proximal tubule epithelium in the following manner: 1) changes to cellular morphology in the form of vacuolization; 2) increased production of reactive oxygen species, resulting in oxidative stress; 3) mitochondrial dysfunction, resulting in decreased efficiency of the electron transport chain and ATP production; 4) perturbation of the protein folding capacity of the endoplasmic reticulum (ER) (activating the unfolded protein response and inducing ER stress); and 5) decreased activity of cell survival kinases. The present review focuses on the direct cytotoxicity of RCM on proximal tubule cells in the absence of in vivo complications, such as alterations in renal hemodynamics or cytokine influence.

Pre-Transplant Left Ventricular Geometry and Major Adverse Cardiovascular Events After Kidney Transplantation

Background

Preventing major adverse cardiovascular events (MACE) after kidney transplantation motivates pre-transplant cardiac evaluation that includes two-dimensional transthoracic echocardiography (TTE). The relationship of relative wall thickness (RWT) to left ventricular mass index (LVMI) in predicting post-transplant MACE is unclear.

Material/Methods

In this multi-ethnic Canadian single-center cohort study, we identified 1063 adults undergoing pre-transplant TTE within 1 year pre-transplant and with minimum 6 months of post-kidney transplant follow-up for MACE, defined as a composite of coronary revascularization, myocardial infarction, stroke, and cardiac death. Left ventricular hypertrophy (LVH, >131 g/m² in men and >100 g/m² in women) and increased RWT (>0.45) were a priori used to define normal (no LVH, normal RWT), concentric remodeling (no LVH, increased RWT), eccentric hypertrophy (LVH, normal RWT), and concentric hypertrophy (LVH, increased RWT).

Results

There were 134 MACE over 3577 patient-years of post-transplant follow-up. Both LVH (HR 1.58, p=0.022) and high RWT (HR 1.44, p=0.041) predicted MACE in multivariate survival regression analysis independently of common pre-transplant MACE risk factors. Concentric remodeling, concentric hypertrophy, and eccentric hypertrophy all increased the risk for MACE (4.44, 5.05, and 5.55 events per 100 patient-years, respectively) versus normal echocardiography (2.71 events per 100 patient-years, all p<0.05 for difference). In Cox interactive regression analysis, LVMI and RWT were independently associated with MACE (p=0.015, p=0.025) and significantly interacted (p=0.008).

Conclusions

LV geometric parameters beyond LVH alone can assist post-transplant prognostication in kidney transplant candidates.

Safety and Feasibility of Carotid Artery Stenting with Dual-Echo Technique to Minimize Iodinated Contrast Dose

BACKGROUND

The aim of this study was to evaluate the safety and feasibility of carotid artery stenting (CAS) employing dual-ultrasound technique and administering a minimal contrast agent in patients with renal insufficiency.

METHODS

Between September 2009 and July 2013, 63 consecutive patients underwent CAS at our institution: dual-echo carotid artery stenting (DECAS) in 7 patients with renal insufficiency and standard carotid artery stenting (STCAS) in the remaining 56 patients. Periprocedural adverse events and outcomes were compared between the 2 groups.

RESULTS

Technical success was achieved in all cases. The 3 procedure-related complications were 1 case of transient hemiparesis in the DECAS group and 1 transient and 1 permanent case of hemiparesis in the STCAS group. The rate of positive diffusion-weighted-imaging lesions did not differ significantly between the 2 groups (28.6% versus 12.5%, P = .26). A significantly smaller volume of contrast was used in DECAS (15 versus 163 mL, P < .01). The change in creatinine level remained stable after CAS and did not differ between the 2 groups (.02 versus .03 mg/dL, P = .96).

CONCLUSIONS

DECAS is safe and feasible for patients with pre-existing renal insufficiency and can provide an alternative for patients with carotid stenosis and renal insufficiency.

Carbon Dioxide in Vascular Imaging and Intervention

Angiography with iodinated contrast agents is bound up with the risks of contrast-induced nephrotoxicity and hypersensitivity, which led to the idea of using carbon dioxide (CO2) gas as a negative contrast medium to eliminate these drawbacks. During the last decade, refinements and experiences have proved carbon dioxide digital subtraction angiography (CO2-DSA) to be an accurate, safe, and clinically promising vascular imaging modality, with the advantages of no hypersensitivity and no nephrotoxicity as well as minimal patient discomfort. In this article, we have reviewed the history, physical and chemical aspects, techniques, and pathophysiologic changes with the use of CO2-DSA as well as some clinical trials. Applications of CO2 gas in vascular interventions and other imagings, and the advantages and limitations of using CO2 gas in DSA are also discussed.

Preprocedural evaluation and endovascular treatment of iliofemoral artery disease without contrast media for patients with pre-existing renal insufficiency

BACKGROUND

Generally, both the preprocedural evaluation and endovascular therapy (EVT) for lower limb arteries require contrast media that is harmful for patients with chronic renal insufficiency. In the present study these procedures were performed without using nephrotoxic contrast media in patients with preexisting renal insufficiency and iliofemoral artery disease.

METHODS AND RESULTS

The 36 consecutive patients with chronic renal insufficiency underwent preprocedural evaluation with duplex examination, magnetic resonance angiography (MRA) without contrast media, and plain computed tomography (CT). A total of 51 lesions were treated using intravascular ultrasound (IVUS) without contrast media. The overall technical success was 100% without any complications. Pre- and postprocedural ankle-brachial indices changed from 0.59 ± 0.23 to 0.92 ± 0.14. The mean serum creatinine concentration before and after treatment, and 3 months after treatment did not change (2.1 ± 1.4, 2.0 ± 1.4, and 2.1 ± 1.6 mg/dl, respectively). The overall 3-month survival rate and limb salvage rate was 100%.

CONCLUSIONS

EVT comprising duplex, MRA, and CT for preprocedural evaluation and IVUS-guided procedure is feasible and may avoid intra-arterial contrast injection in selected patients deemed at high risk for renal failure from nephrotoxic contrast material.

Intravenous contrast medium administration and scan timing at CT: considerations and approaches

The continuing advances in computed tomographic (CT) technology in the past decades have provided ongoing opportunities to improve CT image quality and clinical practice and discover new clinical CT imaging applications. New CT technology, however, has introduced new challenges in clinical radiology practice. One of the challenges is with intravenous contrast medium administration and scan timing. In this article, contrast medium pharmacokinetics and patient, contrast medium, and CT scanning factors associated with contrast enhancement and scan timing are presented and discussed. Published data from clinical studies of contrast medium and physiology are reviewed and interpreted. Computer simulation data are analyzed to provide an in-depth analysis of various factors associated with contrast enhancement and scan timing. On the basis of basic principles and analysis of the factors, clinical considerations and modifications to protocol design that are necessary to optimize contrast enhancement for common clinical CT applications are proposed.

Preventing acute decrease in renal function induced by coronary angiography (PRECORD): a prospective randomized trial

BACKGROUND

Infusion of saline attenuates the decrease in renal function induced by radiographic contrast agents among patients with chronic renal insufficiency.

AIM

The Preventing Renal alteration in Coronary Disease (PRECORD) trial was a randomized trial to assess the effect on renal function of saline infusion during and after coronary angiography in 201 patients without severe chronic renal insufficiency (serum creatinine<140micromol/L).

METHODS

All patients received standard oral hydration: 2000mL of tap water within the 24 hours after coronary angiography. Patients were randomized before the procedure to intravenous hydration (1000mL of 0.9% saline infusion) or no additional hydration. The infusion was started in the catheterization laboratory and continued for 24 hours. The primary endpoint was the change in calculated creatinine clearance between baseline and 24 hours after coronary angiography. The same ionic low osmolar radiographic contrast agent (ioxaglate) was used in all patients.

RESULTS

Both groups had similar baseline characteristics, including age, serum creatinine, volume of contrast and proportion of patients undergoing ad hoc coronary angioplasty. The overall decrease in serum creatinine clearance 24 hours after the procedure was -3.44 (0.68)mL/min. The change in serum creatinine clearance 24 hours after the procedure was -2.81 (1.07)mL/min in the infusion group vs -4.09 (0.91)mL/min in the control group (p=0.38).

CONCLUSION

Renal function is altered only slightly 24 hours after coronary angiography with standard oral hydration alone and is not affected by saline infusion started at the beginning of coronary angiography, even in patients with mild-to-moderate renal dysfunction.

The incidence of contrast-induced nephropathy in trauma patients

BACKGROUND

We measured the incidence and risk factors for contrast-induced nephropathy (CIN) in trauma patients.

METHODS

We conducted a retrospective review of a prospectively collected trauma database. We studied injured patients who received a contrast-enhanced computer tomography with an initial and repeat serum creatinine after 48 h. Exclusion criteria were patients on dialysis. CIN was defined as a 25% rise in creatinine or an increase in creatinine > or =0.5 mg/dl from baseline 48 h after contrast. Data were reported as means+/-SD. Group comparisons were made by Fisher's exact test or Student's t-test (alpha=0.05, two tails).

RESULTS

In total, 235 patients were studied with an average age of 44+/-20 (13-92 years) (80% men), 79% of whom had blunt injuries. CIN incidence was 5.1% [95% confidence interval (CI), 2.9-8.8%]. No patients in the CIN or non-CIN groups died, or required in-patient/chronic dialysis. CIN patients were significantly (P=0.003) older (61 vs. 43 years). For age > or =75 years, the relative risk was 7.7 and the number needed to harm was 5. An elevated creatinine (more than 1.5 mg/dl) was significantly (P=0.007) associated with CIN. For creatinine greater than 1.5 mg/dl, the relative risk was 6.4 and the number needed to harm was 6. CIN was significantly (P=0.02) more likely in patients with glomerular filtration rate less than 60 ml/min/1.73 m. We found no significant (P>0.05) difference in base-deficit, lactate, and Injury Severity Score between CIN and non-CIN patients.

CONCLUSION

We found a 5.1% incidence of CIN in trauma patients exposed to intravenous contrast. Elderly and trauma patients with low glomerular filtration rate were especially predisposed to CIN.

Contrast-induced acute kidney injury

Cardiac angiography and coronary/vascular interventions depend on iodinated contrast media and consequently pose the risk of contrast-induced acute kidney injury (AKI). This is an important complication that accounts for a significant number of cases of hospital-acquired renal failure, with adverse effects on prognosis and health care costs. The epidemiology and pathogenesis of contrast-induced AKI, baseline renal function measurement, risk assessment, identification of high-risk patients, contrast medium use, and preventive strategies are discussed in this report. An advanced algorithm is suggested for the risk stratification and management of contrast-induced AKI as it relates to patients undergoing cardiovascular procedures. Contrast-induced AKI is likely to remain a significant challenge for cardiologists in the future because the patient population is aging and chronic kidney disease and diabetes are becoming more common.

Acute kidney injury with iodinated contrast

Diagnostic and interventional radiographic procedures in critically ill patients commonly depend on iodinated contrast media and consequently pose the risk of contrast-induced acute kidney injury. This is an important complication that accounts for a significant number of cases of hospital-acquired renal failure, with adverse effects on prognosis and healthcare costs. The epidemiology and pathogenesis of contrast-induced acute kidney injury, baseline renal function measurement, risk assessment, identification of high-risk patients, contrast medium use, and preventive strategies will be discussed in this article. An algorithm is suggested for the risk stratification and management of contrast-induced acute kidney injury as it relates to patients undergoing iodinated contrast exposure during critical illness. Contrast-induced acute kidney injury is likely to remain a significant challenge for intensivists in the future because the patient population is aging and chronic kidney disease and diabetes are becoming more common.

A Prospective Feasibility Study of Duplex Ultrasound Arterial Mapping, Digital-Subtraction Angiography, and Magnetic Resonance Angiography in Management of Critical Lower Limb Ischemia by Endovascular Revascularization

Duplex ultrasound arterial mapping (DUAM) allows precise evaluation of peripheral vascular disease (PVD). However, magnetic resonance angiography (MRA) and digital-subtraction angiography (DSA) are the diagnostic tools used most frequently prior to intervention. Our aim was to compare clinical pragmatism, hemodynamic outcomes, and cost-effectiveness when using DUAM alone compared to DSA or MRA as preoperative assessment tools for endovascular revascularization (EvR) in critical lower limb ischemia (CLI). From 2002 through 2005, 465 patients were referred with PVD. Of these, 199 had CLI and 137 required EvR. Preoperative diagnostic evaluation included DUAM (n = 41), DSA (n = 50), or MRA (n = 46). EvR was aortoiliac in 27% of cases and infrainguinal in 73%. Patients were assessed at day 1, 6 weeks, 3 months, and 6 months. Composite end points were relief of rest pain, ulcer/gangrene healing, and increase in perfusion pressure, as measured by ankle-brachial index (ABI) and digital pressures. Patency by DUAM, limb salvage, morbidity, mortality, length of stay, and cost-effectiveness were compared between groups using nonparametric t-test, analysis of variance, and Kaplan-Meier analysis. The three groups were comparable in terms of age, sex, comorbidity, and Society for Vascular Surgery/International Society of Cardiovascular Surgery clinical classification. Six-month mean improvement in ABI in the DUAM group was comparable to that in the DSA group (P = 0.25) and significantly better than that in the MRA group (P < 0.05). Six-month patency rates for the DUAM group were comparable to those in the DSA group (P = 0.68, relative risk [RR] = 0.74, 95% confidence interval [CI] 0.18-2.99) and superior to that in the MRA group (P = 0.022, RR = 0.255, 95% CI 0.09-0.71). Length of hospital stay was lower in the DUAM group compared with the DSA group (P < 0.0001) and the MRA group (P = 0.0003). The cost of DUAM is lower than that of both DSA and MRA. DUAM accurately identified the total number of target lesions for revascularization; however, MRA overestimated it. Our results indicate that DUAM is outstanding when compared with other available modalities as a preoperative imaging tool in a successful EvR program. DUAM is a minimally invasive preoperative evaluation for EvR and offers precise consecutive data with patency and limb salvage rates comparable to EvR based on DSA and superior to MRA. We believe that our feasibility study has established DUAM as an economically proficient primary modality for investigating patients with CLI that significantly shortens length of hospital stay.

Preprocedural imaging: new options to reduce need for contrast angiography

In vascular surgery, the gold standard for evaluation of the lower-extremity arterial tree has long been contrast arteriography (CA). Associated risks of CA are well-documented and include severe allergic reactions, arterial injury and/or hemorrhage, and contrast-induced nephropathy. Increasingly, less-invasive techniques, with fewer inherent risks for complication, are being explored as diagnostic alternatives. Magnetic resonance angiography, computed tomography angiography, and duplex arteriography, each offer distinct advantages, though are not without limitation. This review explores the indications, advantages, and disadvantages of these newer technologies and provides a comparison to CA as a means for defining the anatomic features of patients undergoing lower-extremity revascularization. This data suggests that noninvasive imaging technologies may, in the future, play an increasingly important role in the surgical evaluation of the patient with lower-extremity ischemia.

Efficacy of N-acetylcysteine and hydration versus placebo and hydration in decreasing contrast-induced renal dysfunction in patients undergoing coronary angiography with or without concomitant percutaneous coronary intervention

OBJECTIVE

Contrast-induced renal dysfunction is an iatrogenic complication that occurs more frequently in patients with preexisting renal dysfunction. A prospective, double-blind, randomized, placebo, controlled trial was completed to assess the efficacy of N-acetylcysteine in decreasing the incidence of contrast-induced renal dysfunction in patients with an acute coronary syndrome and renal insufficiency who underwent coronary angiography with or without percutaneous coronary intervention.

METHODS

With similar intravenous hydration protocols, 20 patients received N-acetylcysteine (treatment group) and 20 patients received placebo (control group) in a twice per day dosing regimen with one dose before and three doses after contrast media exposure.

RESULTS

The two groups were similar at baseline on demographic and clinical characteristics, and preexisting renal insufficiency. Contrast-induced renal dysfunction, defined as an increase in serum creatinine greater than 44 micromol/L (.5 mg/dL) and/or 25% above baseline within 48 hours, occurred in 7.5% of the cohort, with 2.5% in the treatment group, and 5% in the control group, for an absolute difference of 2.5%. There was no difference in serum creatinine or creatinine clearance at 24 hours or at 48 hours between the treatment and control groups.

CONCLUSION

These results suggest that this cohort gained no added protection to renal function with the use of N-acetylcysteine.

Carbon dioxide digital subtraction angiography-assisted endovascular aortic aneurysm repair in the azotemic patient

OBJECTIVE

This report analyzes the safety and efficacy of carbon dioxide digital subtraction angiography (CO(2)-DSA) for EVAR in a group of patients with renal insufficiency compared with a concurrent group of patients with normal renal function undergoing EVAR with iodinated contrast angiography (ICA).

METHODS

Between 2003 and 2005, 100 consecutive patients who underwent EVAR using ICA, CO(2)-DSA, or both were retrospectively reviewed, and preoperative, intraoperative, postoperative, and follow-up variables were collected. Patients were divided into two groups depending on renal function and contrast used. Group I comprised patients with normal renal function in whom ICA was used exclusively, and group II patients had a serum creatinine >or=1.5 mg/dL, and CO(2)-DSA was used preferentially and supplemented with ICA, when necessary. The two groups were compared for the outcomes of successful graft placement, renal function, endoleak type, and frequency, and the need for graft revision. Comparisons were made using chi(2) analysis, Student t test, and the Fisher exact test.

RESULTS

A total of 84 EVARs were performed in group I and 16 in group II. Patient demographics and risk factors were similar between groups with the exception of serum creatinine, which was significantly increased in group II (1.8 mg/dL vs 1.0 mg/dL P < .0005). All 100 endografts were successfully implanted. Patients in group II had longer fluoroscopy times, longer operative times, and increased radiation exposure, and 13 of 16 patients required supplemental ICA. Mean iodinated contrast use was 27 mL for group II vs 148 mL in group I (P < .0005). Mean postoperative serum creatinine was unchanged from baseline, and 30-day morbidity was similar for both groups. No patient required dialysis. No patients died. Perioperatively, and at 1 and 6 months, the endoleak type and incidence and need for endograft revision was no different between groups.

CONCLUSIONS

CO(2)-DSA is safe, can be used to guide EVAR, and provides outcomes similar to ICA-guided EVAR. CO2-DSA protects renal function in the azotemic patient by lessening the need for iodinated contrast and associated nephrotoxicity, but with the tradeoff of longer fluoroscopy and operating room times and increased radiation exposure.

Contrast medium use

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Epidemiology and prognostic implications of contrast-induced nephropathy

Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 0.5 mg/dL (44.2 mumol/L), or a 25% increase from the baseline value 48 hours after the procedure, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, responsible for approximately 11% of cases. CIN may be difficult to distinguish from cholesterol embolization, another cause of postprocedure renal impairment. The reported incidence of CIN varies depending on the patient population studied. The impact of postprocedural renal impairment on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention. CIN is associated with increased mortality both in hospital and at 1 year. A higher incidence of in-hospital and late cardiovascular events, as well as longer hospital stays, has been reported in patients developing CIN. In a small proportion of patients, CIN is severe enough to require dialysis, and these patients have a particularly poor prognosis. Many of the risk markers for CIN are also predictive of a worse prognosis.

Duplex-guided balloon angioplasty and stenting for femoropopliteal arterial occlusive disease: An alternative in patients with renal insufficiency

BACKGROUND

The technique of balloon angioplasty of infrainguinal arteries requires standard arteriography and fluoroscopic guidance. We attempted to perform this procedure under duplex guidance to avoid the use of nephrotoxic contrast material and radiation exposure in patients with renal insufficiency.

METHODS

Over 16 months, 28 patients (17 men) with serum creatinine levels of 1.5 mg/dL or more underwent 37 lower extremity duplex-guided balloon angioplasties at our institution. Ages ranged from 58 to 92 years (mean +/- SD, 74 +/- 9 years). Disabling claudication was the indication in 24 cases (65%), and critical ischemia, in 13 cases. Preoperative duplex arterial mapping showed severe superficial femoral artery and/or popliteal artery stenoses in all cases. No arterial occlusions were treated in this series. Seven procedures (19%) were performed for restenosis. The ipsilateral common femoral artery was cannulated in 32 cases (86%), and the contralateral common femoral artery, in 5 cases (14%), under direct duplex visualization. Contralateral common iliac artery cannulations were performed with the help of fluoroscopy. By using sonographic visualization, a guidewire was directed into the origin of the superficial femoral artery, across the diseased segment, and into the popliteal artery. The diseased segment was then balloon-dilated. Balloon diameter and length were chosen according to arterial measurements obtained by duplex scan. Plaque dissections and recoils causing stenosis of 30% or more, a peak systolic velocity ratio of 2 or more, or both were stented under duplex guidance. Arterial duplex examinations and ankle/brachial indexes were obtained before hospital discharge, within 1 month after the procedure, and every 3 months thereafter.

RESULTS

Thirty-day survival was 100%. Local complications included one open exploration for expanding hematoma. Technical success was achieved in all cases. Placement of intraluminal stents was deemed appropriate in 23 (62%) of 37 cases. The 1-month patency and limb salvage rates were 100%. Preprocedure and postprocedure ankle/brachial indexes ranged from 0.3 to 0.9 (mean +/- SD, 0.64 +/- 0.16) and 0.64 to 1.2 (mean +/- SD, 0.92 +/- 0.15), respectively (P < .0001).

CONCLUSIONS

Duplex-guided balloon angioplasty seems to be a safe and effective technique that allows renal patients to experience continued limb salvage and relief from claudication without the risk of developing dye-induced acute renal failure. Other advantages include direct visualization of the puncture site, accurate selection of the proper size of balloon and stent, confirmation of the adequacy of the technique by hemodynamic and imaging parameters, and avoidance of radiation. Although this technique holds considerable potential, longer follow-up will help to fully evaluate its broader applicability.

Duplex–assisted internal carotid artery balloon angioplasty and stent placement: A novel approach to minimize or eliminate the use of contrast material

BACKGROUND

Carotid artery balloon angioplasty and stenting (CBAS) is emerging as an acceptable alternative to carotid endarterectomy in selected high-risk patients. Conversely, patients with pre-existing renal impairment, diabetes, or both may be harmed by the nephrotoxic contrast agents required during CBAS. We attempted to limit or eliminate the use of contrast material during CBAS.

METHODS

Eighteen patients with severe carotid stenoses (>70%) underwent CBAS at our institution over the last 12 months with duplex scan-assisted CBAS. Of these, 12 were primary procedures, and 6 were performed for carotid re-stenosis. Fourteen patients (78%) were neurologically asymptomatic. The average age of these patients was 75 +/- 11 years (range, 44-92 years). Hypertension, chronic renal insufficiency (serum creatinine level > or =1.5 mg/dL), coronary artery disease, diabetes, and smoking were present in 89%, 67%, 59%, 33%, and 28% of patients, respectively. Preoperative duplex carotid mapping was performed in all cases. All procedures were performed with patients under local anesthesia and light sedation.

RESULTS

An ATL HDI 5000 scanner with the SonoCT feature was used. The common femoral artery was cannulated with a single-entry needle under direct ultrasound visualization. Fluoroscopy was used to assist passage of the guidewire into the aorta and the common carotid artery. In only four cases (22%) was an aortic arch angiogram obtained. Selective catheterization of the internal and external carotid arteries was performed under ultrasound guidance. The distal cerebral protection device (17 cases) was placed under fluoroscopic guidance. Balloon width and length were chosen according to ultrasound measurements. Balloon and stent deployment were successfully achieved with ultrasound guidance alone in all cases. Appropriate stent apposition and resolution of the stenosis was confirmed by duplex scanning in all cases. Five patients (28%) were noted to have low (<100 mL/min) internal carotid artery volume flow after stent deployment (range, 20-88 mL/min; mean +/- SD, 50 +/- 25 mL/min). The internal carotid artery volume flow increased immediately after Filterwire retrieval in all cases and ranged from 136 to 400 mL/min (mean, 245 +/- 107 mL/min). This increase was statistically significant ( P < .02). No ipsilateral strokes or deaths occurred during follow-up from 1 to 12 months (mean follow-up, 5 months).

CONCLUSIONS

Duplex scan-assisted CBAS is feasible and may reduce the need for intra-arterial contrast injection in selected patients deemed at high risk for renal failure from nephrotoxic contrast material. Additional advantages include direct visualization of the puncture site, precise position of the balloon and stent, and B-mode and hemodynamic confirmation of the adequacy of the technique.

Advances in vascular imaging

The improvement of vascular imaging has allowed the acquisition of vascular images with higher resolution while minimizing the risks and discomfort to patients. As imaging developments continue to progress, establishment of valid clinical-based evidence, before the application of each innovation, will assure maintenance of the current trend. Also, as the vascular surgeon adopts a more comprehensive approach in the care of vascular patients, a high-quality endovascular suite will provide an environment for integration of both traditional open and evolving endovascular procedures.

Role of Duplex Arteriography as the Sole Preoperative Imaging Modality Prior to Lower Extremity Revascularization Surgery in Diabetic and Renal Patients

The limitations and complications associated with contrast angiography (CA) prior to lower extremity revascularization have led to an increased interest in duplex arteriography (DA) as a potential replacement. We report our experience with DA in patients with diabetes and/or chronic renal insufficiency (CRI) that would particularly benefit from a noninvasive approach to preoperative evaluation of the arterial tree. From January 1998 to November 2000, DA was performed in 145 patients with diabetes mellitus and/or CRI prior to 180 arterial reconstructions. One hundred twenty-one procedures were performed on 91 patients with diabetes alone, 41 on 33 patients with diabetes and CRI, and 18 on 15 patients with CRI alone. Patient ages ranged from 36 to 98 years (mean 72 +/- 12 years). Indications for surgery were severe claudication in 33 (18%), rest pain in 37 (21%), nonhealing ischemic ulcers in 52 (29%), and limb gangrene in 58 (32%). Optimal inflow and outflow anastomotic sites were selected according to a diagram based on DA that included arterial tree imaging from mid-aorta to the pedal vessels. Preoperative contrast arteriography was performed in 16 cases (9%) because of extremely poor runoff based on DA and limited visualization of outflow vessels. The distal anastomosis was to the popliteal artery in 89 cases (49%) and to the tibial and pedal arteries in 91 (51%). Intraoperative findings confirmed the preoperative DA results with the exception of one (0.6%) where the distal anastomosis was placed proximal to a significant stenosis requiring an extension graft. The use of DA presents a safe and reliable option to prebypass CA for many patients with diabetes or CRI. The ease of use and favorable patient outcomes achieved by this imaging modality may rival the use of CA for these patients.

Radiocontrast induced nephropathy

In spite of improvements in chemical structure, contrast media assisted X-ray examination is still the third leading cause of hospital-acquired acute renal failure. An increase >50% or >88 micro mol/L in S-creatinine is a clinically important acute renal failure. The peak in S-creatinine occurs within 2-5 days after exposure. The frequency of oliguria, transient or permanent haemodialysis is unknown. The cause is a hypoxic tubular injury due to vasoconstriction with release of free oxygen radicals. Major risk factors are prior renal insufficiency and diabetes mellitus. Minor risk factors are congestive heart disease, dehydration, hypotension, hypoxia, amount of contrast, ionic and high osmolar contrast, repeated examinations at short intervals, abdominal examination, and perhaps age, smoking, hypercholesterolaemia, and use of Non-Steroidal Anti inflammatory Drug. Prevention seems possible by omission or reduction of contrast, ameliorating predisposing factors, saline hydration 24h before and after exposure, and 600 mg acetylcysteine orally twice daily 24h before and after exposure. A three-day treatment with 20mg nitrendipine daily, starting 1 day before examination may also be preventive. The present research is unfortunately characterised by small numbers, lack of clinical important renal failure, and lack of long term results. The latter may be important after new data indicate that radiation may trigger a chronic oxidative process through a similar pathway.

The endovascular management of ruptured abdominal aortic aneurysms

Endovascular aneurysm repair (EVAR) is a controversial technique, which remains the subject of a number of prospective randomised trials. Although questions remain regarding its long-term durability objective evidence exists which demonstrates its reduced physiological impact compared with conventional open repair. If this technique could be used in patients with ruptured abdominal aortic aneurysm (AAA) it may reduce the high peri-operative mortality. A review of the literature identified a limited experience with EVAR of ruptured AAA. Only a small number of case series with selected patients exist. The majority of patients were haemodynamically stable. However, the selective use of aortic occlusion balloons allowed successful endovascular management in a small number of unstable cases. All investigators had access to an "off the shelf" endovascular stent-graft (EVG). Per-operative mortality ranged from 9 to 45% and may reflect increasing experience and patient selection. A number of patients who underwent successful EVAR were turned down for open repair. A number of important lessons have been learned from these studies but questions remain regarding patient suitability and staffing issues. If these difficulties can be surmounted then the technique may offer an alternative to open repair.

Comparison of Magnetic Resonance Angiography (MRA) and Duplex Ultrasound Arterial Mapping (DUAM) prior to infrainguinal arterial reconstruction

OBJECTIVE

the purpose of this study is to compare Magnetic Resonance Angiography (MRA) to Duplex Ultrasound Arterial Mapping (DUAM) and intraoperative findings to determine the clinical, accuracy of MRA for planning lower extremity revascularization procedures.

METHODS

forty-two patients who underwent lower extremity revascularization procedures had both MRA and DUAM evaluations. These data were analyzed retrospectively and two distinct endpoints were considered. First, we compared the MRA and DUAM findings for aorto-iliac, femoral-popliteal and infra-popliteal segments to intraoperative findings and evaluated the degree to which they agreed. Second, if there was a disagreement between imaging modalities, it was established whether a change in operative procedure would have resulted.

RESULTS

MRA and DUAM findings agreed in 26 of 31 cases (83%) of aorto-iliac segments, in 25 of 31 cases (81%) of femoral-popliteal segments, and in 16 of 21 cases (76%) of infra-popliteal segments. In total, DUAM agreed with intraoperative findings in 98% of cases while MRA agreed in 82% (p<.001). Disagreement between intraoperative findings and DUAM lead to an alternate surgical procedure in only one case (2%) while disagreement with MRA lead to a different procedure in 38% of cases (p<.001).

CONCLUSIONS

these data show that MRA is not yet adequate to replace conventional angiography and is less accurate that DUAM. Further improvements are necessary before MRA can be used as the sole modality for formulation of a pre-operative plan for lower extremity revascularization.

Compensated heart failure predisposes to outer medullary tubular injury: studies in rats

BACKGROUND

Heart failure (HF) is considered a putative factor predisposing to acute renal failure (ARF). Since outer medullary hypoxic injury may play an important role in the pathogenesis of acute tubular necrosis, we explored the impact of experimental HF on the propensity to develop ARF with hypoxic medullary injury following the inhibition of prostaglandin and nitric oxide synthesis.

METHODS

Compensated, high-output HF was induced in Sprague-Dawley rats by aorto-caval fistula. At the eighth to ninth postoperative day, the rats were injected with indomethacin and N(omega) nitro-L-arginine methyl ester (L-NAME; ARF protocol) and were sacrificed 24 hours later for morphologic evaluation.

RESULTS

Kidney function comparably declined in HF-ARF rats and in control sham operated animals (CTR-ARF). Nevertheless, outer medullary hypoxic damage with medullary thick ascending limb (mTAL) necrosis occurred almost exclusively in the HF-ARF group (11 +/- 4% vs. 0.2 +/- 0.2% of tubules in CTR-ARF, P < 0.03). In a third group of HF animals subjected to vehicles only (HF-Nil), kidney function was preserved and renal morphology remained intact. Papillary-tip necrosis was consistently found in all animals subjected to indomethacin and L-NAME, irrespective of preconditioning. Morphometric evaluation disclosed that HF was not associated with mTAL hypertrophy.

CONCLUSIONS

Incipient HF predisposes to hypoxic outer medullary injury, probably reflecting the impact of regional vasoconstrictive stimuli rather than tubular hypertrophy when protective local vasodilating mechanisms are hampered. The presence and extent of outer medullary hypoxic damage cannot be predicted from the functional derangement, which in the experimental settings may also represent prerenal azotemia or papillary damage.

Accuracy of CO(2) angiography in vessel diameter assessment: a comparative study of CO(2) versus iodinated contrast material in a porcine model

PURPOSE

To compare, with use of intravascular ultrasound (IVUS) as an internal reference standard in a porcine model, arterial diameters measured from arteriograms obtained with use of CO(2) to those obtained with use of iodinated contrast material (ICM).

MATERIALS AND METHODS

In nine pigs, digital subtraction angiograms (DSAs) were obtained in the aorta and iliac arteries to compare vessel diameters measured with use of CO(2) to those measured with use of ICM. These measurements were divided by measurements made with use of intravascular ultrasound (IVUS) to yield a DSA/IVUS ratio. Differences between ICM and CO(2) were compared with analysis of variance to assess the effect of location (aorta vs iliac), contrast material used (ICM vs CO(2)), and position (posteroanterior, right anterior oblique, or left anterior oblique). Secondary analysis compared measurements of dependent and nondependent iliac arteries and compared the use of hand-injected CO(2) to that of CO(2) injected by an injector.

RESULTS

The DSA/IVUS ratio was 70.7% +/- 4.4% with ICM use and 69.6% +/- 6.3% with CO(2) use, which did not represent a significant difference (P =.311). Animal position had no effect (P =.477). Underestimation was worse in the iliac arteries than in the aorta (67.4% +/- 1.5% vs 71.4% +/- 1.7%; P =.038). There was no difference in nondependent (P =.163) arteries, but CO(2) underestimated dependent iliac artery size more than ICM did (66.3% +/- 4.8% vs 70.3% +/- 5.4%; P =.051). Vessel diameter was underestimated more with the CO(2) injector than with hand-injected CO(2) (64.3% +/- 2.3% vs 71.7% +/- 1.7%; P <.0001).

CONCLUSION

There is no difference in diameter underestimation between CO(2) and ICM in this animal model. Hand-injection of CO(2) causes less underestimation of vessel diameter than does the CO(2) injector.

Grading of Internal Carotid Artery Stenosis: Validation of Doppler/Duplex Ultrasound Criteria and Angiography Against Endarterectomy Specimen

OBJECTIVES

duplex ultrasound has replaced angiography prior to carotid endarterectomy (CEA) in many institutions. However, the indications for CEA are based on angiographically controlled studies and widely accepted ultrasound criteria do not exist. Consequently, the reliability of Doppler and/or duplex ultrasound to predict a high-grade ICA stenosis has to be proven.

DESIGN

prospective validation study.

MATERIALS

one hundred and fifty carotid bifurcations assessed by ultrasound and selective angiography and 68 acrylat outcasts of carotid specimen after eversion CEA.

METHODS

ICA stenosis was measured angiographically according to the ECST criteria. Combined Doppler acoustic standard criteria (CDASC), peak systolic frequency (PSF), peak systolic velocity (PSV) and end-diastolic velocity (EDV) served as criteria for the ultrasound assessment. These criteria and the results of angiography were compared to the degree of ICA stenosis determined by specimen measurements.

RESULTS

the median degree of ICA stenosis as assessed by angiography (82%, range 56-97%) and CDASC (83%, range 50-99%) corresponded well to the specimen measurements (80%, range 50-95%). The sensitivity of angiography and CDASC to predict a 70-90% ICA stenosis (ECST criteria) compared to the specimen measurements was 88% and 95%, respectively. The positive predictive value (PPV) reached 92% and 96%, respectively. CDASC were equivalent to angiography and were superior to the best single frequency or velocity parameters. If CDASC do not indicate a >/=70% ICA stenosis in spite of a PSV >/=180 cm/s and/or an EDV >/=50 cm/s, angiography may detect patients with a >70% ICA stenosis.

CONCLUSIONS

CDASC are valid in the quantification of high-grade ICA stenosis. They are more reliable than single velocity and/or frequency measurements. However, if velocity criteria and CDASC do not agree, angiography should be performed.

Carbon dioxide angiography for endovascular grafting in high-risk patients with infrarenal abdominal aortic aneurysms

Allergic reactions to contrast media, preexisting renal dysfunction, and hyperthyroidism are relative contraindications for angiography with conventional contrast medium. Carbon dioxide (CO(2)) angiography is an alternative method in high-risk patients because CO(2) is nontoxic, without allergic potential, and not iodic. CO(2)-related complications are extremely rare. Because renal insufficiency often occurs in vascular patients, this method will become increasingly important for endovascular surgery. We report on three consecutive patients with asymptomatic infrarenal aortic aneurysm and concomitant renal dysfunction or allergic reactions to standard contrast media. Aortic stent grafts were deployed under CO(2) angiographic control without complications or worsening of renal function.

The prognostic implications of further renal function deterioration within 48 h of interventional coronary procedures in patients with pre-existent chronic renal insufficiency

BACKGROUND

Acute deterioration in renal function is a recognized complication after coronary angiography and intervention.

OBJECTIVES

The goal of this study was to determine the impact on acute and long-term mortality and morbidity of contrast-induced deterioration in renal function after coronary intervention.

METHODS

We studied 439 consecutive patients who had a baseline serum creatinine > or = 1.8 mg/dL (159.1 /micromol/L) who were not on dialysis who underwent percutaneous coronary intervention in a tertiary referral center. All patients were hydrated before the procedure, and almost all received ioxaglate meglumine; 161 (37%) patients had an increase in serum creatinine > or = 25% within 48 h or required dialysis and 278 (63%) did not. In-hospital and out-of-hospital clinical events (death, myocardial infarction, repeat revascularization) were assessed by source documentation.

RESULTS

Independent predictors of renal function deterioration were left ventricular ejection fraction (p = 0.02) and contrast volume (p = 0.01). In-hospital mortality was 14.9% for patients with further renal function deterioration versus 4.9% for patients with no creatinine increase (p = 0.001); other complications were also more frequent. Thirty-one patients required hemodialysis; their in-hospital mortality was 22.6%. Four patients were discharged on chronic dialysis. The cumulative one-year mortality was 45.2% for those who required dialysis, 35.4% for those who did not require dialysis and 19.4% for patients with no creatinine increase (p = 0.001). Independent predictors of one-year mortality were creatinine elevation (p = 0.0001), age (p = 0.03) and vein graft lesion location (p = 0.08).

CONCLUSIONS

For patients with pre-existing renal insufficiency, renal function deterioration after coronary intervention is a marker for poor outcomes. This is especially true for patients who require dialysis.

Lower-extremity revascularisation without preoperative contrast arteriography in 185 cases: lessons learned with duplex ultrasound arterial mapping

PURPOSE

we have previously reported our experience with lower-extremity duplex-ultrasound arterial mapping (DUAM) compared to contrast arteriography (CA) to predict lower-extremity bypass sites. The present study evaluates arterial revascularisation procedures for chronic limb ischaemia based on DUAM.

MATERIALS AND METHODS

from January 1998 to July 1999, 195 patients (128 men, 67 women) underwent 211 lower-extremity revascularisation procedures based on DUAM. Indications for surgery were tissue loss, severe claudication, rest pain and popliteal aneurysm in 57%, 25%, 14% and 4% of the limbs, respectively. The mean age was 72+/-12 years and risk factors such as diabetes, hypertension, tobacco use, coronary artery and end-stage renal disease were present in 53%, 58%, 53%, 50% and 12% of the patients, respectively. Previous revascularisation procedures had been performed in 23% of the limbs. Preoperative evaluation consisted of DUAM alone (185) or of a combination of DUAM and CA (29 limbs). CA was deemed necessary due to a combination of technical difficulties that jeopardized adequate sonographic imaging and presence of disadvantaged run-off for medico-legal reasons. DUAM consisted of direct imaging of all major arteries from the distal aorta to the pedal circulation. Optimal inflow and outflow bypass anastomotic sites were selected according to a diagram based on DUAM. Adequacy of the inflow was additionally assessed by common-femoral-artery waveform and confirmed by intraoperative pressure measurements. Post-bypass CA was obtained to verify patency of the run-off.

RESULTS

DUAM procedure time averaged 75+/-26 min. For patients who underwent only DUAM, the distal anastomosis was to the popliteal artery in 91 cases and to tibial or pedal arteries in 58 cases. Distal anastomosis was proximal to a significant lesion in two cases that required jump grafts. Cumulative patency rates at 1 and 3 months for popliteal bypasses were 96% and 90%, and for infrapopliteal bypasses 90% and 83%, respectively. Inflow procedures to the femoral artery, patch and balloon angioplasties accounted for the remaining 40 cases. Four primary amputations were performed after CA confirmed DUAM findings.

CONCLUSIONS

contrary to general belief, these data show that high-quality arterial ultrasonography represents a safe alternative to preoperative CA, even for infrapopliteal bypasses. This non-invasive approach may be especially useful for patients with contrast allergy or impaired renal function.

Contrast medium-induced nephrotoxicity: pathophysiology and prevention

Contrast medium-induced nephrotoxicity (CMN) is a common form of iatrogenic acute renal failure. Typically, patients experience changes in serum creatinine or creatinine clearance between 1 and 5 days after exposure to a contrast medium, but they rarely require dialysis. The mechanism for CMN is not understood, but renal insufficiency, dehydration, and congestive heart failure are risk factors. The frequency of CMN with high-osmolality versus low-osmolality media is controversial. Prophylaxis can reduce CMN. Of many different strategies, hydration with normal saline before and after exposure offers the best protection with the fewest adverse effects.

Accuracy of CO2 angiography in vessel diameter assessment: a comparative study of CO2 versus iodinated contrast material in an aortoiliac flow model

PURPOSE

Precise vessel sizing prior to endovascular intervention is critical to achievement of technical success. Diameter measurements obtained with CO2 and iodinated contrast material in an aortoiliac flow model were compared.

MATERIALS AND METHODS

Aortoiliac flow was simulated in a compliant, silicone elastomer phantom of the aortoiliac system using an autoperfusion pump (flow volume, approximately 1100 mL/min; mean arterial pressure, 70-80 mm Hg at 80-90 cycles/minute) and a glycerol solution (40% by weight; viscosity 3.7 centipoise at 20 degrees C). Digital subtraction angiography was performed with the phantom in the anteroposterior (AP) plane and in three oblique planes with both CO2 and iodinated contrast material. Five sets of images for both CO2 and iodinated contrast material were obtained for each projection. Two readers independently performed vessel diameter measurements at seven sites (distal abdominal aorta, bilateral proximal and distal common iliac, and mid-external iliac arteries). The model was then evaluated with intravascular ultrasound (IVUS) using a 20-MHz imaging catheter. Actual diameter measurements were taken from the inner wall to inner wall in orthogonal planes at the same locations within the model, as described previously. Analysis was performed to determine local difference in measurements (t tests), difference when compared to the standard AP projection with iodinated contrast material (Dunnett's test) and inter-reader variability (Pitman's test).

RESULTS

The contralateral iliac vessel segment did not opacify when imaging with CO2 in the 45 degrees obliquities; thus, 22 of 28 sites were available for comparison. At 18 of 22 (81.8%) sites, there was significant difference in vessel measurements (P < .01), with CO2 yielding a significantly larger diameter at 17 of 22 (77.3%) of the sites. The difference in mean diameter ranged from -1.28 to 4.47 mm. With use of the AP iodinated contrast material run as the standard, there were significant differences (P < .05) in vessel diameter at 17 of 22 (77.3%) and four of 21 (19%) sites for CO2 and iodinated contrast material respectively, with CO2 tending toward greater diameter measurements. Significant differences (P < .05) in variance between the two readers were present but occurred primarily with CO2 in the AP projection and iodinated contrast material in the 45 degrees left obliquity. With use of IVUS as the standard, there were significant differences (P < .05) in the measured vessel diameters with CO2 at nine of 22 (40.9%) of the sites and with iodinated contrast material at 17 of 28 (60.7%) of the sites. Of the measurements made with CO2, seven of nine (77.8%) of the measurements were of larger diameter than those obtained with IVUS. By contrast, of the measurements made with iodinated contrast material angiography, IVUS measured larger diameters in 16 of 17 (94.1%).

CONCLUSION

CO2 angiography consistently yielded significantly larger vessel measurements when compared to both iodinated contrast angiography and WVUS. These results have important implications in regards to planning intervention based solely on CO2 angiography. Further evaluation is needed before recommending CO2 for vessel sizing in clinical practice.

Digital subtraction angiography of the abdominal aorta and lower extremities: carbon dioxide versus iodinated contrast material

PURPOSE

To compare the diagnostic value of carbon dioxide to that of iodinated contrast material for digital subtraction angiography of the abdominal aorta and lower extremities.

MATERIALS AND METHODS

Thirty-five patients underwent comparative CO2 and iodinated contrast material arteriography of the abdominal aorta and lower extremities. For each contrast study, three independent observers evaluated the degree of opacification and percentage of stenosis of each vessel, the degree of certainty of their observations, and the overall quality of the study. Data of CO2 and iodinated studies were compared using analysis of variance for repeated measures. Interobserver and intertechnique agreements were estimated with Cohen's kappa and intraclass correlation coefficient.

RESULTS

Iodine-based vascular opacification was superior to that with CO2 in the central and distal arteries (P = .02). The degree of certainty and overall quality score were higher for iodine than for CO2-based contrast studies (P = .00001). The interobserver agreement for categorizing stenoses was higher for iodine as compared to CO2-based angiography. No significant difference was observed between the mean stenosis values obtained with CO2 and iodine-based angiography in any segment. Intraclass correlation coefficient demonstrated a high degree of convergence of the two techniques for assessing the percentage of stenosis.

CONCLUSION

CO2 can be used as an alternative to iodinated contrast material for obtaining arteriograms of the abdominal aorta and lower extremities for investigating atherosclerotic disease.

Diagnosis and treatment of chronic lower extremity ischemia

Chronic lower extremity ischemia is due to progressive atherosclerosis of the aorto-iliac and/or infrainguinal arteries. This disease process is of great importance as millions of patients are affected by lower extremity arterial occlusive disease. Most of these patients are asymptomatic but a growing number of them are symptomatic, with complaints ranging from mild claudication to gangrene. The increasing number of patients affected by lower extremity atherosclerosis is, in part, due to the 'graying' of the general population and to the medical improvements of the past three decades that have allowed patients with generalized atherosclerosis to survive longer. Fortunately, the diagnosis and management of peripheral arterial occlusive disease has also significantly progressed leading to improved graft patency, limb salvage rates, and quality of life for patients.

Arteriography in chronic renal failure: a case for carbon dioxide

PURPOSE

The aim of this study was to assess the utilisation of carbon dioxide arteriography, performed with a simple injection system, as the imaging technique of choice in patients with chronic renal failure.

METHODS

Patients with chronic renal impairment who required arterial imaging or intervention were recruited for carbon dioxide angiography. Demographic data were prospectively recorded and pre- and post-arteriogram renal function was quantified. Radiographic images were graded by an independent radiologist.

RESULTS

Twenty-eight patients underwent renal or aorto-femoral studies with only one failure. There were no cases of contrast-induced nephropathy. Twenty-two of the films (79%) were graded as excellent or good, four as acceptable and two were considered to be poor (non-diagnostic).

CONCLUSIONS

This study has demonstrated that carbon dioxide angiography is a safe and clinically effective procedure in patients with chronic renal failure.

Vascular surgery without arteriography: use of Duplex ultrasound

Although contrast arteriography has served as the historical 'gold standard' for diagnosis of arterial disease, recent improvements in noninvasive diagnostic methods have made it possible to plan surgical treatment without subjecting patients to this invasive procedure. This approach avoids both the risks and costs associated with arteriography. Duplex scanning has become the standard noninvasive test for extracranial carotid artery disease, and it can also be used to directly evaluate the lower extremity arteries. In addition to the standard duplex criteria for classification of carotid stenosis, new criteria are available that reflect the stenosis thresholds identified in randomized clinical trials. Clinical experience has clearly shown that carotid endarterectomy can be performed safely based on the duplex scan alone in the majority of patients: however, arteriography is still indicated in selected cases. The evaluation of lower extremity arterial disease requires examination of multiple arterial segments, and most vascular surgeons still rely on the anatomic detail provided by arteriography for preoperative planning. Still, it may be possible to avoid formal preoperative arteriography in selected patients by using a combination of lower extremity duplex scanning and intraoperative arteriography. Further developments in noninvasive testing will continue to reduce the need for diagnostic arteriography prior to direct arterial surgery.

Angiography with carbon dioxide (CO2)

CO2 possesses many advantages over conventional iodinated contrast agents used for arteriography. It is nonallergic and lacks renal toxicity. Its unique properties permit use of smaller catheters in diagnostic and therapeutic angiographic procedures, allow optimal vascular imaging of various neoplasm, assist in detection of occult gastrointestinal bleeding, and facilitate TIPS procedures. With digital subtraction techniques and stacking programs, CO2 arteriography is as accurate as iodinated contrast studies in most patients and thus is the preferred arterial imaging technique in patients with contrast allergy and renal insufficiency. CO2 is also extremely inexpensive compared with available contrast agents. Understanding of the effects of buoyancy and compressibility is necessary for safe, controlled delivery of CO2 during arteriography, but only rare complications have occurred in our large experience with CO2 angiography. Thus, use of CO2 as an arterial contrast agent significantly expands the safety and utility of arterial imaging in patients with peripheral vascular disease.

Accuracy of duplex ultrasound in evaluating carotid artery anatomy before endarterectomy

PURPOSE

Anatomic features, such as a high carotid bifurcation (< 1.5 cm from the angle of the mandible), excessive distal extent of plaque (> 2.0 cm above the carotid bifurcation), or a small diameter (< or = 0.5 cm) redundant or kinked internal carotid artery can complicate carotid endarterectomy. In the past, arteriography was the only preoperative study capable of imaging these features. This study assessed the ability of duplex ultrasound to evaluate their presence before surgery.

METHODS

A consecutive series of 20 patients who underwent 21 carotid endarterectomies had preoperative duplex ultrasound evaluations of these anatomic features. These evaluations were correlated with operative measurements from an observer blinded to the duplex findings.

RESULTS

The mean difference between duplex and operative measurements for the distance between the carotid bifurcation and the angle of the mandible, the distal extent of plaque, and the internal carotid artery diameter was 0.9 cm, 0.3 cm, and 0.8 mm, respectively. The correlation coefficient between the two methods was 0.86, 0.75, and 0.59, respectively. Duplex ultrasound predicted a high carotid bifurcation, excessive distal extent of plaque, or a redundant or kinked internal carotid artery with 100% sensitivity (p < 0.05, p < 0.01, and p < 0.001, respectively). The sensitivity of duplex ultrasound in predicting a small internal carotid artery diameter was 80%. The specificity of duplex ultrasound for predicting excessive distal extent of plaque, small internal carotid artery diameter, high carotid bifurcation, and a coiled or kinked carotid artery was 92%, 56%, 100%, and 100%, respectively.

CONCLUSION

Duplex ultrasound can predict the presence of anatomic features that may complicate carotid endarterectomy. Preoperative duplex imaging of these features may be helpful in patients who undergo carotid endarterectomy without preoperative arteriography.

Preoperative testing before carotid endarterectomy: a survey of vascular surgeons' attitudes

Traditional surgical practice and published consensus statements from major vascular surgery specialty societies have considered contrast arteriography to be a routine part of the diagnostic evaluation prior to carotid endarterectomy (CEA). However, some surgeons now omit routine preoperative arteriography if a technically adequate carotid duplex scan is performed and indications for CEA are clear. To better establish current practice patterns and to characterize vascular surgeons' opinions about the role of preoperative arteriography, the Peripheral Vascular Surgery Society membership was surveyed by mail. Eighty-six percent of the members responded (430 of 502). Ninety-three percent of all patients considered for CEA are evaluated with duplex scanning; 82% with arteriography. While the majority of surgeons typically obtain both a duplex scan and an arteriogram, 70% have performed CEA without a preoperative arteriogram. Brain imaging studies (CT or MRI) are obtained in 26% and MR angiograms in 10% of cases. Seventy-five percent of the surgeons agreed with the statement that CEA without preoperative arteriography is an acceptable practice if appropriate indications for surgery are present. Furthermore, one third believed that CEA without a preoperative arteriogram is generally acceptable (acceptable more than half the time). Respondents were stratified by surgical experience time in practice and practice type. No significant differences in responses were found, suggesting the acceptance of CEA without preoperative arteriography is broad-based. This survey demonstrates changing attitudes among practicing vascular surgeons regarding the necessity for routine arteriography prior to CEA. Carotid endarterectomy on the basis of duplex scanning and clinical assessment should be considered an accepted alternative.

CO2 angiography--a technique for vascular imaging in renal allograft dysfunction

Use of iodinated contrast for vascular imaging can be associated with nephrotoxicity and hypersensitivity reactions. Renal injury following conventional angiography is more likely to manifest in the setting of preexisting renal dysfunction. In the setting of suboptimal renal allograft function, these considerations are particularly relevant. Recently, CO2 has received attention as a nontoxic, injectable, rapidly absorbed gas that is a cost-effective alternative to standard contrast agents in high-risk patients, such as renal transplant recipients. We report the clinical course of a patient with transplant renal artery stenosis and a serum creatinine of 2.8 mg/dl who has successfully undergone angiography and percutaneous transluminal angioplasty using CO2 as the sole contrast agent. This case illustrates the potential use for CO2 as a contrast agent for vascular imaging in patients with suboptimal renal function who require definitive vascular imaging or therapy.

Effects of saline, mannitol, and furosemide on acute decreases in renal function induced by radiocontrast agents

BACKGROUND

Injections of radiocontrast agents are a frequent cause of acute decreases in renal function, occurring most often in patients with chronic renal insufficiency and diabetes mellitus.

METHODS

We prospectively studied 78 patients with chronic renal insufficiency (mean [+/- SD] serum creatinine concentration, 2.1 +/- 0.6 mg per deciliter [186 +/- 53 mumol per liter]) who underwent cardiac angiography. The patients were randomly assigned to receive 0.45 percent saline alone for 12 hours before and 12 hours after angiography, saline plus mannitol, or saline plus furosemide. The mannitol and furosemide were given just before angiography. Serum creatinine was measured before and for 48 hours after angiography, and urine was collected for 24 hours after angiography. An acute radiocontrast-induced decrease in renal function was defined as an increase in the base-line serum creatinine concentration of at least 0.5 mg per deciliter (44 mumol per liter) within 48 hours after the injection of radiocontrast agents.

RESULTS

Twenty of the 78 patients (26 percent) had an increase in the serum creatinine concentration of at least 0.5 mg per deciliter after angiography. Among the 28 patients in the saline group, 3 (11 percent) had such an increase in serum creatinine, as compared with 7 of 25 in the mannitol group (28 percent) and 10 of 25 in the furosemide group (40 percent) (P = 0.05). The mean increase in serum creatinine 48 hours after angiography was significantly greater in the furosemide group (P = 0.01) than in the saline group.

CONCLUSIONS

In patients with chronic renal insufficiency who are undergoing cardiac angiography, hydration with 0.45 percent saline provides better protection against acute decreases in renal function induced by radiocontrast agents than does hydration with 0.45 percent saline plus mannitol or furosemide.

Nephrotoxic risks of renal angiography: contrast media-associated nephrotoxicity and atheroembolism--a critical review

Renal angiography remains the "gold standard" procedure for the detection of renal artery stenosis. However, clinicians often avoid renal angiography because of fears of contrast media-associated nephrotoxicity (CM-AN) and atheroembolism. This review focuses on these potential angiographic complications, with particular emphasis, in the case of CM-AN, on clinical features, incidence, risk factors with an emphasis on pre-existing renal insufficiency and diabetes mellitus, volume of contrast media, low osmolar versus high osmolar contrast media, and prophylaxis. For atheroembolism, areas emphasized are pathology, clinical features, precipitating features, and incidence in various settings. Although the literature contains an abundance of information about CM-AN and atheroembolism, this review identified multiple areas of uncertainty regarding features of both of these complications. For example, additional studies are needed to determine the incidence of CM-AN, both asymptomatic and clinically severe, in patients with a wide range of pre-existing renal insufficiency with and without diabetes mellitus, following low volume digital subtraction renal angiography with low osmolar contrast media. In a similar manner, studies are needed with adequate postcontrast observation periods to determine the true incidence of clinically significant atheroembolism following diagnostic renal angiography and angioplasty and techniques that may modify this complication. Until further knowledge in both of these areas is available, it is difficult to precisely determine the risks of renal angiography and/or angioplasty in the azotemic patient suspected of or having renal ischemic disease using modern radiologic techniques.