Clearance of iopamidol, a non-ionic contrast medium, by CAPD in patients with end-stage renal failure

Contrast-Induced Encephalopathy: A Rare Complication in a Patient on Peritoneal Dialysis with Several Risk Factors

Major adverse renal and cardiovascular events are reported for high-risk patients undergoing intra-arterial procedures, even if performed with iso-osmolar contrast media (CM). We report a case of contrast-induced encephalopathy (CIE) in a peritoneal dialysis (PD) patient, affected by diabetes, hypertension, and chronic heart failure. A 78-year-old PD patient (diuresis 1,000 mL) underwent a percutaneous angioplasty of the carotid. Immediately after the exam, he developed mental confusion and aphasia. Encephalic computed tomography scan and magnetic resonance imaging excluded ischemia or hemorrhage, but both showed cerebral edema; EEG showed right hemisphere abnormalities, sequelae of recent ischemia. Mannitol and steroids were administered to reduce edema, and additional PD exchange was performed with depurative aim. Within 2 days the patient completely recovered. CIE mimics severe neurological diseases, and it should be considered as differential diagnosis if symptoms come out soon after intra-arterial administration of CM, especially in high-risk patients. Our patient suffered from diabetes, chronic kidney disease, hypertension, chronic heart failure, which are possible contributing factors to the development of CIE. Moreover, this clinical scenario is noteworthy because the development in a patient who underwent PD had never been described before.

Development of a Nanoscale Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent That Measures pH

AcidoCEST MRI can measure the extracellular pH (pHe) of the tumor microenvironment in mouse models of human cancers and in patients who have cancer. However, chemical exchange saturation transfer (CEST) is an insensitive magnetic resonance imaging (MRI) contrast mechanism, requiring a high concentration of small-molecule agent to be delivered to the tumor. Herein, we developed a nanoscale CEST agent that can measure pH using acidoCEST MRI, which may decrease the requirement for high delivery concentrations of agent. We also developed a monomer agent for comparison to the polymer. After optimizing CEST experimental conditions, we determined that the polymer agent could be used during acidoCEST MRI studies at 125-fold and 488-fold lower concentration than the monomer agent and iopamidol, respectively. We also determined that both agents can measure pH with negligible dependence on temperature. However, pH measurements with both agents were dependent on concentration, which may be due to concentration-dependent changes in hydrogen bonding and/or steric hindrance. We performed in vivo acidoCEST MRI studies using the three agents to study a xenograft MDA-MB-231 model of mammary carcinoma. The tumor pHe measurements were 6.33 ± 0.12, 6.70 ± 0.15, and 6.85 ± 0.15 units with iopamidol, the monomer agent, and polymer agent, respectively. The higher pHe measurements with the monomer and polymer agents were attributed to the concentration dependence of these agents. This study demonstrated that nanoscale agents have merit for CEST MRI studies, but consideration should be given to the dependence of CEST contrast on the concentration of these agents.

Elimination of Iomeprol in Patients Undergoing Continuous Ambulatory Peritoneal Dialysis

Objective

To examine the elimination of iomeprol, its safety in clinical use, and its peritoneal permeability in continuous ambulatory peritoneal dialysis (CAPD) patients with variable degrees of residual renal function (RRF).

Design

A nonrandomized comparison study.

Setting

Hospitalized patients in CAPD unit of Chikuho and University Hospitals.

Participants

Fourteen patients treated by CAPD and 6 by hemodialysis (HD).

Interventions

Total dialysate, blood, and 24-hour urine collections were obtained for 4 consecutive days after the administration of iomeprol. A peritoneal equilibration test was performed just before and after the administration of iomeprol.

Measurements

Iomeprol (iodine) concentration was measured. Residual renal function was estimated as the mean of renal creatinine and urea clearances. Dialysate-to-plasma ratios (D/P) of creatinine and iomeprol were also determined.

Results

In all CAPD patients, plasma iomeprol clearance was markedly slow, with a biological half-life ( T1/2) of over 32 hours. However, no patients suffered from any adverse effects, and over 80% of plasma iomeprol was eliminated during the 4-hour HD. The plasma iomeprol elimination rate was significantly higher from 4 hours after the iomeprol administration in CAPD patients with RRF [mean estimated creatinine clearance (CCr) 3.8 mL/min, n = 7] compared to the remaining patients (mean estimated CCr 0.6 mL/min, n = 7); however, T1/2 in patients with RRF was over 24 hours. D/P creatinine was significantly correlated with D/P iomeprol, and peritoneal iomeprol permeability may depend on an individual's peritoneal solute transport properties.

Conclusions

A prolonged elimination rate of iomeprol was documented in our CAPD patients both with and without RRF. A HD procedure or intensive peritoneal dialysis just after the use of iomeprol may be advisable to promptly remove circulating iomeprol.

Comparative Study of the Dialysability of Iobitridol and Iohexol in the Rat with Impaired Renal Function

Purpose:

To assess the dialysability of iobitridol, a comparative study with iohexol was conducted in the rat over 4 hours.

Material and Methods:

After ligature of the renal veins and arteries, a group of animals was submitted to continuous peritoneal dialysis, while the remainder were not.

Results:

In the event of total renal failure, biliary excretion rose from 0.4 to 9% for iobitridol and from 2 to 16% for iohexol. In the rats submitted to peritoneal dialysis, biliary excretion decreased to 5% in the iobitridol group and to 13% in the iohexol group. Further, 18% of the test substances were eliminated in the dialysis liquid.

Conclusions:

As their physicochemical characteristics are very similar, the differences between the biliary excretion levels of these 2 media may be caused by a factor related to their respective molecular conformations.

The use of iodinated contrast media in patients with end-stage renal disease

Iodinated contrast agents are well tolerated in ESRD patients. Certain types of ICM, i.e., LOCM and the nonionic agents are associated with better safety profiles. Current available evidence, although not optimal, does not support the need for additional hemodialysis for ICM removal to preserve residual renal function or to treat other potential toxicities of ICM. However, limiting exposure to ICM is a prudent measure in ESRD patients given ICM’s potential toxicity; close monitoring of patients with poor cardiac function is also recommended in subjects receiving higher doses of ICM, especially those receiving HOCM.

Clearance and safety of the radiocontrast medium iopamidol in peritoneal dialysis patients

Although the characteristics and safety of radiocontrast media in peritoneal dialysis (PD) patients are not yet well defined, their use in PD patients is considered generally safe. In this study, we evaluated clearance and adverse events of iopamidol in PD patients. We measured the iopamidol concentration in the plasma, dialysate, and urine of 11 patients. Iopamidol clearance from patient plasma was delayed with a half-life of 33.3 h, and the elimination ratio was 83.6% for 96 h. We retrospectively investigated adverse events occurring in a total of 50 stable PD patients who underwent a total of 64 angiographic computed tomography (CT) scans. In 64 angiographic CT scans, two cases of adverse events were observed. Our results suggest that iopamidol can be eliminated by regular PD and careful observation for adverse events are necessary for the safe use of radiocontrast media.

Preventing complications of radiographic contrast media: is there a role for dialysis?

Nephrologists are often called upon to provide hemodialysis to remove radiographic contrast media in patients with chronic kidney disease (CKD)--usually but not exclusively, those with end-stage renal disease. The reasons for this request vary from concerns over the volume load associated with the administration of a hyperosmolar solution, to the renal and extra-renal toxicities of the contrast itself. Simple calculations demonstrate that the increase in extracellular volume after a typical contrast load is minimal. Data supporting the extra-renal toxicity of contrast in patients maintained on dialysis are lacking. Iodinated contrast agents have molecular weights of 700-1500. This relatively small size as well as their lack of protein binding makes them well suited for removal with extracorporeal renal replacement therapies. Thus, provision of hemodialysis immediately following a contrast load is often utilized in an attempt to prevent further renal damage in patients with advanced stages of CKD. A number of trials have failed to demonstrate that this maneuver is effective. Hemofiltration (HF) has been reported to decrease the risk of acute renal failure in patients with CKD receiving a contrast load, but the studies are methodologically flawed. Therefore, there is currently no sound basis for routinely recommending hemodialysis (or HF) in patients at high risk for contrast media-associated complications.

Dialysis and iodinated contrast media

Contrast media are excreted mainly by glomerular filtration. There is thus, a significant correlation between both body and renal clearances of contrast media and glomerular filtration rate, and their renal excretion will be delayed in patients with renal insufficiency. Contrast media can be efficiently removed from blood by hemodialysis (HD). Since most contrast media are middle-sized molecules, the main factors potentially influencing their removal by HD are blood flow, membrane surface area, molecular size, transmembrane pressure, and dialysis time. Peritoneal dialysis is also effective in removing contrast agents from the body but takes longer than HD. Dialysis immediately after radiographic contrast studies has been suggested for two groups of patients. Those on chronic HD and those at very high risk for contrast nephropathy. Three studies have examined the necessity of immediate dialysis after intravascular injection of contrast media in chronic HD patients; the authors found no evidence that it is effective at preventing contrast nephropathy. The reasons why HD treatment was not beneficial in those three studies are not known. Perhaps, the rapid onset of renal injury after administration of contrast media is one answer. It is also possible that HD per se was nephrotoxic and might have offset the beneficial effect of the removal of contrast media. Marenzi et al. randomized 114 consecutive patients with chronic renal failure undergoing coronary interventions to either hemofiltration in an intensive care unit or isotonic saline hydration. The authors concluded that periprocedural hemofiltration given in an intensive care unit setting appears to be effective in preventing the deterioration of renal function due to contrast agent induced nephropathy and is associated with improved in-hospital and long term outcomes. The concentration of contrast media can effectively be reduced by HD and peritoneal dialysis. HD does not offer any protection against contrast media induced nephrotoxicity. Hemofiltration may decrease the risk of contrast induced nephropathy and have some long-term benefits, but additional studies are needed to better define the appropriate population for this treatment.

Evaluation of Kidney Function in Patients with Acute Renal Failure Using High-Performance Liquid Chromatography: A Case Report

Accurate measurement of glomerular function rate (GFR) in the setting of acute renal failure is difficult to achieve with current clinical methods, such as measuring plasma creatinine concentration and 24-hour urine creatinine clearance. High-performance liquid chromatography was used to measure GFR directly in a critically ill patient with acute renal failure. This approach involved evaluating the elimination kinetics of nonionic contrast material administered intravenously for radiologic imaging. It required no additional patient exposure to radiographic contrast media and enabled caregivers to determine kidney function accurately in the presence of worsening clinical status and delayed changes in plasma creatinine. This and other methods for more accurate measurement of GFR in patients with acute renal failure may provide the foundation for clinical studies that assess the severity and management of acute renal failure.

Pharmacokinetics of gadodiamide injection in patients with severe renal insufficiency and patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate the pharmacokinetics, dialysability, and safety of gadodiamide injection in patients with severely reduced renal function not treated with renal replacement therapy and patients undergoing hemodialysis or continuous ambulatory peritoneal dialysis.

MATERIALS AND METHODS

Twenty-seven patients--nine with severely reduced renal function (glomerular filtration rate, 2-10 mL/min), nine undergoing hemodialysis, and nine undergoing continuous ambulatory peritoneal dialysis--were followed up for 5, 8, and 22 days, respectively, after receiving gadodiamide injection (0.1 mmol per kilogram body weight).

RESULTS

Gadodiamide injection caused no changes in renal function. In patients with severely reduced renal function, the elimination half-life of gadodiamide injection was prolonged (34.3 hours +/- 22.9) compared with data in healthy volunteers (1.3 hours +/- 0.25). An average of 65% of the gadodiamide injected was eliminated during a hemodialysis session. After 22 days of continuous ambulatory peritoneal dialysis, 69% of the total amount of gadodiamide was excreted; this reflects the low peritoneal clearance. In all patients, no metabolism or transmetallation of gadodiamide was found. There were no contrast material-related adverse events.

CONCLUSION

Gadodiamide is dialysable and can safely be used in patients with severely impaired renal function or those undergoing hemodialysis or continuous ambulatory peritoneal dialysis. No precautions to increase the elimination are necessary.

Elimination of low-osmolality contrast media by hemodialysis

PURPOSE

To compare the dialyzability and safety of 2 types of low-osmolality contrast media administered to end-stage renal failure patients maintained on regular hemodialysis.

MATERIAL AND METHODS

Of 44 CT examinations, iohexol was used in 22 and ioxaglate in the other 22. Adverse reactions and hemodynamic changes were recorded. Thirty minutes after the beginning of CT investigation, hemodialysis was commenced. Elimination rate and clearance of the contrast media were measured as indices of their dialyzability.

RESULTS

After 4 hours of hemodialysis, 78.4+/-6.5% of iohexol and 72.4+/-6.0% ioxaglate were eliminated. Clearance of iohexol was higher than that of ioxaglate at all sampling times. No severe hemodynamic change nor adverse reaction were observed. Minor reactions were more frequently observed in the ioxaglate group.

CONCLUSION

Iohexol, a nonionic monomeric contrast medium, is more advantageous for hemodialysis patients than ioxaglate, an ionic dimeric contrast medium.

Polyarthropathy--a delayed reaction to low osmolality angiographic contrast medium in patients with end stage renal disease

Since the introduction of low osmolality non-ionic media, acute reactions to radiographic contrast are uncommon and delayed reactions are especially rare, consisting mostly of mild flu-like symptoms. We report two patients suffering from end-stage renal failure and treated by continuous ambulatory peritoneal dialysis (CAPD) who developed a severe constitutional illness including acute polyarthropathy 6 and 16 h after injection of the low osmolality non-ionic contrast medium, iopamidol. Although the clinical presentation of the reactions was similar to a systemic lupus syndrome there was no immunological evidence to support this as an aetiological mechanism. Since CAPD is a relatively inefficient method of clearing contrast media prolonged high circulating levels of iopamidol may have been a contributory factor to these unusually severe delayed contrast reactions.