Assessment of possible nephrotoxicity from iohexol in patients with normal and impaired renal function

Continuous Infusion of Low-Dose Iohexol Measures Changing Glomerular Filtration Rate in Critically Ill Patients

OBJECTIVE

Measurement of changing glomerular filtration rate in acute kidney injury remains problematic. We have previously used a continuous infusion of low-dose Iohexol to measure glomerular filtration rate in stable subjects and postulate that changes greater than 10.3% in critically ill patients indicate acute kidney injury. Our objective is to explore the extent to which continuous infusion of low-dose Iohexol can be a measure of changing glomerular filtration rate during acute kidney injury.

DESIGN

Clinical observational exploratory study.

SETTING

Adult ICU.

PATIENTS

Three patient groups were recruited: nephrectomy group: predictable onset of acute kidney injury and outcome (n = 10); surgery group: predictable onset of acute kidney injury, unpredictable outcome (n = 11); and acute kidney injury group: unpredictable onset of acute kidney injury and outcome (n = 13).

INTERVENTIONS

Continuous infusion of low-dose Iohexol was administered for 24-80 hours. Plasma (ClP) and renal (ClR) Iohexol clearances were measured at timed intervals.

MEASUREMENTS AND MAIN RESULTS

Kidney Disease: Improved Global Outcomes acute kidney injury criteria were fulfilled in 22 patients (nephrectomy = 5, surgery = 4, and acute kidney injury = 13); continuous infusion of low-dose Iohexol demonstrated acute kidney injury in 29 patients (nephrectomy = 10, surgery = 8, acute kidney injury = 11). Dynamic changes in glomerular filtration rate were tracked in all patients. In the nephrectomy group, ClR decreased by an expected 50% (50.8% ± 11.0%). Agreement between ClP and ClR improved with increasing duration of infusion: bias of ClP versus ClR at 48 hours was -0.1 ± 3.6 mL/min/1.73 m (limits of agreement: -7.2 to 7.1 mL/min/1.73 m). Coefficient of variation of laboratory sample analysis was 2.4%.

CONCLUSIONS

Continuous infusion of low-dose Iohexol is accurate and precise when measuring glomerular filtration rate and tracks changes in patients with differing risks of acute kidney injury. Continuous infusion of low-dose Iohexol may provide a useful standard against which to test novel biomarkers for the diagnosis of acute kidney injury.

Safety of Iohexol Administration to Measure Glomerular Filtration Rate in Different Patient Populations: A 25-Year Experience

<b><i>Background/Aim:</i></b> In clinical research setting, accurate and precise measurement of glomerular filtration rate (GFR) is essential to overcome the limitations of GFR estimation with equations, which are often unreliable. In recent decades, a method for measuring GFR by plasma clearance of iohexol, a non-ionic radiocontrast agent, was developed. To evaluate the safety of the procedure, we aimed to review all immediate adverse reactions that could be related to iohexol administration in our group’s 25 years worth of experience. <b><i>Methods:</i></b> We retrospectively reviewed all GFR investigations in 2,891 patients, between 1992 and 2016, as part of 37 clinical trials coordinated by our group. Subjects with disparate renal diseases, kidney transplant recipients, and living donors – all with different renal function categories – were included in the surveyed clinical trials. <b><i>Results:</i></b> During 15,147 GFR measurements, only one treatment-related event of moderate intensity was identified. Flushing, urticaria, and itching were observed in a diabetic patient a few minutes after iohexol administration during the first GFR measurement. The event recovered without sequelae after intravenous injection of methylprednisolone sodium succinate. The patient was not hospitalized and the event was categorized as non-serious. Eight additional non-serious events observed closely following iohexol injection were considered as not related to treatment. Thus, independent of disease conditions and GFR categories, the overall rate of treatment-related events was 0.0066%. <b><i>Conclusion:</i></b> Iohexol administration for GFR measurement is a safe procedure, even in repeated investigations in the same subject, that should be adopted in clinical research and, when needed, also in clinical practice.

Validation of a continuous infusion of low dose Iohexol to measure glomerular filtration rate: randomised clinical trial

INTRODUCTION

There is currently no accurate method of measuring glomerular filtration rate (GFR) during acute kidney injury (AKI). Knowledge of how much GFR varies in stable subjects is necessary before changes in GFR can be attributed to AKI. We have designed a method of continuous measurement of GFR intended as a research tool to time effects of AKI. The aims of this crossover trial were to establish accuracy and precision of a continuous infusion of low dose Iohexol (CILDI) and variation in GFR in stable volunteers over a range of estimated GFR (23-138 mL/min/1.73 m(2)).

METHODS

We randomised 17 volunteers to GFR measurement by plasma clearance (PC) and renal clearance (RC) of either a single bolus of Iohexol (SBI; routine method), or of a continuous infusion of low dose Iohexol (CILDI; experimental method) at 0.5 mL/h for 12 h. GFR was measured by the alternative method after a washout period (4-28 days). Iohexol concentration was measured by high performance liquid chromatography/electrospray tandem mass spectrometry and time to steady state concentration (Css) determined.

RESULTS

Mean PC was 76.7 ± 28.5 mL/min/1.73 m(2) (SBI), and 78.9 ± 28.6 mL/min/1.73 m(2) (CILDI), p = 0.82. No crossover effects occurred (p = 0.85). Correlation (r) between the methods was 0.98 (p < 0.0001). Bias was 2.2 mL/min/1.73 m(2) (limits of agreement -8.2 to 12.6 mL/min/1.73 m(2)) for CILDI. PC overestimated RC by 7.1 ± 7.3 mL/min/1.73 m(2). Mean intra-individual variation in GFR (CILDI) was 10.3% (p < 0.003). Mean ± SD Css was 172 ± 185 min.

CONCLUSION

We hypothesise that changes in GFR >10.3% depict evolving AKI. If this were applicable to AKI, this is less than the 50% change in serum creatinine currently required to define AKI. CILDI is now ready for testing in patients with AKI.

TRIAL REGISTRATION

This trial was registered with the European Union Clinical Trials Register ( https://www.clinicaltrialsregister.eu/ ), registration number: 2010-019933-89 .

Contrast induced nephropathy in urology

Intravenous contrast agents have a distinct role in urological imaging: to study precise anatomical delineation, vascularity, and to assess the function of the renal unit. Contrast induced nephropathy (CIN) is a known adverse effect of intravenous contrast administration. The literature on incidence, pathophysiology, clinical features, and current preventive strategies available for CIN relevant to urologists was reviewed. A search of the PubMed database was done using the keywords nephropathy and media, prevention and control or prevention Contrast media (explode), all adverse effects, and kidney diseases (explode). An online search of the EMBASE database for the time ranging from 1977 to February 2009 was performed using the keywords ionic contrast medium, adverse drug reaction, major or controlled clinical study, human, nephrotoxicity, and kidney disease. Current publications and data most relevant to urologists were examined. CIN was the third most common cause of hospital-acquired renal failure. The incidence is less common with intravenous contrast administration as compared with intra-arterial administration. The pathogenesis of contrast mediated nephropathy is due to a combination of toxic injury to renal tubules and medullary ischemic injury mediated by reactive oxygen species. CIN most commonly manifests as a nonoliguric and asymptomatic transient decline in renal function. Patients who developed CIN were found to have increased mortality, longer hospital stay, and complicated clinical course. An overview of risk factors and risk prediction score for prognostication of CIN are elaborated. Preventive strategies including choice of contrast agents, maximum tolerated dose, role of hydration, hydration regime, etc. are discussed. The role of N- acetyl cysteine, Theophylline, Fenoldapam, Endothelin receptor antagonists, iloprost, atrial natriuretic peptide, and newer therapies such as targeted renal therapy (TRT) are discussed. A working algorithm based on current evidence is proposed. No current treatment can reverse or ameliorate CIN once it occurs, but prophylaxis is possible.

Contrast medium induced nephropathy in urological practice

PURPOSE

Contrast medium induced nephropathy is the third cause of in-hospital acute renal failure. The first studies in this area were done with reference to urological practice only. Although various guidelines on the management of contrast medium induced nephropathy were provided by the European Society of Urogenital Radiology, more recently many investigators have focused their attention on contrast medium use in interventional vascular radiology and cardiology. We critically reviewed the literature to clarify the impact of contrast medium induced nephropathy in urology and the possible prophylactic measures against it.

MATERIALS AND METHODS

A MEDLINE/PubMed, EMBASE and Cochrane Library search for 1971 to 2006 was performed. All articles related to the use of contrast medium in urological practice and contrast medium induced nephropathy were reviewed.

RESULTS

Many pathological conditions frequently seen by urologists are diagnosed by imaging requiring contrast medium. A basic understanding of the risk factors for contrast medium induced nephropathy and the strategies for its prevention are useful to prepare urological patients for these procedures. Prophylaxis includes the discontinuation of potentially nephrotoxic drugs and the use of protocols for periprocedural hydration.

CONCLUSIONS

The general approach to the recognition and prevention of contrast medium induced nephropathy in patients at risk should be extended to urological clinical practice since no definitive evidence based data are available regarding contrast medium induced nephropathy management in urological patients. Moreover, these patients can frequently present with the most significant risk factor for contrast medium mediated kidney damage, that is preexisting acute or chronic renal failure. Controlled trials are needed to establish the incidence of contrast medium induced nephropathy in diagnostic or interventional procedures in uroradiology.

Selection of contrast media

The pathophysiologic mechanisms of contrast-induced nephropathy (CIN) have been reviewed by Persson and Tepel. They focus on the renal response to contrast media (CM). In this section, we focus on the CM itself. Aspects of importance with regard to CIN include the route of administration, the volume of CM, the manner of X-ray attenuation, and the specific chemical structure of the CM.

Risk of Nephropathy after Intravenous Administration of Contrast Material: A Critical Literature Analysis

PURPOSE

To assess the risk of nephropathy after administration of contrast material by reviewing the published literature on intravenous contrast material administration and by separating reports with appropriate control measures from those without such measures.

MATERIALS AND METHODS

The MEDLINE database was searched for articles published from October 1966 to September 2004 that contained the phrases "contrast," "contrast medium," "contrast media," or "radiocontrast" and any of the words or phrases "nephrotoxicity," "nephropathy," kidney failure," or "renal failure." The identified publications were reviewed and limited to original clinical series. Studies were categorized according to the route of contrast material administration. Those in which an identifiable group of patients received contrast material intravenously were further evaluated to determine which studies compared results with those from a control group of patients who did not receive contrast material.

RESULTS

Only 40 (1.3%) of 3081 publications had patients who received contrast material intravenously. Of these, only two publications had control groups of patients who received no contrast material. The incidence of postcontrast nephropathy in these two series was not substantially different from that in the control groups.

CONCLUSION

Properly controlled clinical studies of intravenously administered radiographic contrast media fail to demonstrate renal damage.

Thermosensitive N-isopropylacrylamide–N–propylacrylamide-vinyl pyrrolidone terpolymers: Synthesis, characterization and preliminary application as embolic agents

In this article, thermosensitive N-isopropylacrylamide (NIPAAm)-N-propylacrylamide (NPAAm)-vinyl pyrrolidone (VP) terpolymers (PNINAVP) were prepared by varying feed ratios with free radical copolymerization method. The composition ratios and molecular weights of PNINAVP were examined by NMR and GPC. The thermo-responsive behaviors of copolymer solutions in the absence and with addition of Iohexol, a radiopaque agent, were investigated by differential scanning calorimetry (DSC) and rheometer. The sol-gel transition of the copolymer solutions occurred reversibly within 1 min in response to temperature. Incorporation of Iohexol increased the transition time and transition temperature of PNINAVP solutions; the rheological properties were also influenced. It was observed that at body temperature, PNINAVP and Iohexol could form an integrated bulky hydrogel presumably due to the hydrogen bonding between them, which was favorable for the clinical follow-up and reducing toxic side effects. In vitro embolic model experiment indicated that 5 wt% 16:16:1H PNINAVP solution containing Iohexol displayed a satisfactory embolization effect. This solution was injected into the rete mirabiles (RM) of six swines through a microcatheter. The angiographical results obtained immediately after the operation showed a complete occlusion of the RM, and no recanalization was observed at postoperative month 1. The histological examination demonstrated no acute inflammatory reaction inside the RM and surrounding tissue. This work could provide a beneficial guidance for designing a new temperature-sensitive polymer-based embolic agent.