Effect of radiologic contrast media on cell volume regulation in rabbit proximal renal tubules

Changes in blood and renal function in patients after cerebral digital subtraction angiography

Objective

Describe the incidence of contrast-induced acute renal injury (CI-AKI) and the changes in hematocrit in a cohort of patients undergoing elective cerebral digital subtraction angiography (DSA).

Methods

In this prospective study, patients undergoing cerebral DSA were assessed for hematocrit level and CI-AKI risk factors before the procedure and for developing CI-AKI 72 h after exposure to the contrast media.

Results

Among 215 patients (109 men, mean age 36.6 years). The most frequently found CI-AKI risk factor was hypertension. There were no cases of permanent renal impairment after 14 days. Significant changes were observed in hematocrit (45.7 ± 4.9, vs. 44.5 ± 4.6, p = 0.001), estimated creatinine clearance (129.7 ± 48.3, vs. 123.1 ± 40.5, p = 0.002), and serum creatinine (0.72 ± 0.19, vs 0.74 ± 0.18, p = 0.031). The mean change in serum creatinine 72 h after contrast administration was +0.27 ± 0.10 mg/dL (p < 0.05).

Conclusions

The incidence of CI-AKI after elective cerebral DSA was 1.4%. A significant decrease in hematocrit was observed up to 72 h after the procedure.

Contrast Administration to the Deceased Kidney Donor Has No Impact on Post-Transplant Outcomes

BACKGROUND

Contrast-induced acute kidney injury may occur in patients undergoing imaging studies. This study reviews all deceased kidney donors at a single center during a 15-y period to determine if donor contrast exposure results in contrast-induced acute kidney injury in the donor or is associated with worse outcomes in the transplant recipient.

METHODS

Donor and recipient renal functions were recorded, including donor serum creatinine and recipient delayed graft function, creatinine clearance at 1 y, and early and late graft survival. Donor contrast exposure was recorded as the number of preprocurement contrasted studies.

RESULTS

Donor and recipient records were available for 1394 transplants (88%). There were 51% of donors who received any contrasted study (38%, one study; 12%, two studies, and 1%, three studies). Donor contrast exposure was not associated with significant differences in preprocurement serum creatinine levels. Post-transplant, donor contrast exposure was associated with risk of neither delayed graft function (4% for all) nor early kidney graft loss. Creatinine clearance at 1 y was equivalent. Five-year Cox regression demonstrated higher graft survival for contrast-exposed grafts (P = 0.03).

CONCLUSIONS

There is no negative effect of donor contrast administration on early and late kidney graft function. These findings included donor kidneys exposed to as many as three contrasted studies.

Increased plasma osmolar gap is predictive of contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CIAKI) is a common complication after percutaneous coronary artery intervention (PCI). It is urgent to find a novel, easily measurable and accurate predictor for the early detection of CIAKI. Hyperosmolarity and large amounts of contrast media are risk factors for CIAKI. However, there is no study on plasma osmolar gap as a predictor of CIAKI. We enrolled 89 patients undergoing elective PCI and tested changes of serum sodium, osmolar gap, and renal function at 0, 6, 12 and 24 hours. Plasma osmolar gap was calculated using the following formula: measured plasma osmolarity - [2(Na) + serum urea nitrogen/2.8 + glucose/18]. CIAKI was defined as follows: increase in serum creatinine of ≥ 50%, increase in serum creatinine of ≥ 0.3 mg/dL, or decrease in estimated glomerular filtration rate of ≥ 25% within 24 hours after PCI. The incidence of CIAKI was 13.5% (12/89 patients). The CIAKI group had higher plasma osmolar gaps 6 hours after PCI. The adjusted hazard ratio of the plasma osmolar gap from hour 6 (1-mOsm/L increments) to the development of CIAKI was 1.12 (95% confidence interval [CI], 1.01-1.26; P = 0.041). Sensitivity and specificity of 7 mOsm/L or higher plasma osmolar gap at hour 6 were 70.0% and 76.6%, respectively (area under the ROC curve = 0.77 [95% CI, 0.65-0.89]). Increased plasma osmolar gap may precede the development of CIAKI in patients undergoing PCI. In conclusion, plasma osmolar gap may be a useful predictor for the development of CIAKI.

Early renal transplantation after donor renal angiography affects initial graft function

BACKGROUND

Renal angiography of a living donor is a common radiologic examination before transplantation. However, the contrast agent used during this procedure can cause contrast nephropathy. There are insufficient data regarding whether this radiocontrast exposure detoriates renal function and survival after transplantation. In this study, we analyzed the effects of radiocontrast exposure to donors before transplant surgery on the incidence of delayed graft function (DGF) and on the outcomes of recipients at 1 year posttransplantation.

METHODS

We divided 80 living donor transplantations according to the duration between the renal angiography and the transplantation procedure: Group 1 as early transplantation at ≤ 20 days (n = 42) versus group 2 of late transplantation at ≥ 20 days (n = 38). We retrospectively collected acute rejection episodes and graft survival at 1 year, monthly serum creatinine values of, DGF, proteinuria at 1 month, GFR at posttransplant day 3 month 1, and 1 year.

RESULTS

There were 10 group 1 recipients (23.8%) and 2 group 2 (5.3%) subjects who experienced ≥ 1 acute rejection episode in the 1st posttransplant year (P = .02); 1 patient in each group experienced graft loss at 1 year (P = .941). DGF was observed in 9 (22%) versus 1 patient (2.6%) in group 2 (P = .009). Posttransplant day 3 creatinine values were significantly higher (P = .005) with significantly lower GFR values (P = .043) in group 1. However, creatinine and GFR levels were similar at 1 month and 1 year. Month 1 proteinuria levels were significantly higher in group 1 (P = .014). There was a significant negative correlation between renal angiography time and month 1 proteinuria (P = .014).

CONCLUSIONS

Early renal transplantation (within 2 weeks after renal angiography) in living kidney donors can detoriate initial graft function and cause DGF.

Contrast-induced kidney injury: mechanisms, risk factors, and prevention

In general, iodinated contrast media (CM) are tolerated well, and CM use is steadily increasing. Acute kidney injury is the leading life-threatening side effect of CM. Here, we highlight endpoints used to assess CM-induced acute kidney injury (CIAKI), CM types, risk factors, and CIAKI prevention. Moreover, we put forward a unifying theory as to how CIAKI comes about; the kidney medulla's unique hyperosmolar environment concentrates CM in the tubules and vasculature. Highly concentrated CM in the tubules and vessels increases fluid viscosity. Thus, flow through medullary tubules and vessels decreases. Reducing the flow rate will increase the contact time of cytotoxic CM with the tubular epithelial cells and vascular endothelium, and thereby damage cells and generate oxygen radicals. As a result, medullary vasoconstriction takes place, causing hypoxia. Moreover, the glomerular filtration rate declines due to congestion of highly viscous tubular fluid. Effective prevention aims at reducing the medullary concentration of CM, thereby diminishing fluid viscosity. This is achieved by generous hydration using isotonic electrolyte solutions. Even forced diuresis may prove efficient if accompanied by adequate volume supplementation. Limiting the CM dose is the most effective measure to diminish fluid viscosity and to reduce cytotoxic effects.

Pathophysiology of renal tissue damage by iodinated contrast media

1. The present review focuses on the cytotoxic effects of iodinated contrast media (CM) that are shared by all types of CM. 2. Although the clinical nephrotoxicity of CM has been progressively improved, all currently available CM still possess a level of cytotoxicity, which is probably caused by iodine. 3. The toxicity caused by specific CM properties, such as osmolarity, viscosity and ionic strength, can be differentiated from the cytotoxicity common to all CM in studies using cell culture, isolated blood vessels and isolated tubules. 4. The cytotoxicity induced by CM leads to apoptosis and cell death of endothelial and tubular cells and may be initiated by cell membrane damage, together with oxidative stress. 5. Cell damage may be aggravated by factors such as tissue hypoperfusion and hypoxia, properties of individual CM, such as ionic strength, high osmolarity and/or viscosity, and clinically unfavourable conditions. 6. Clinically detectable renal failure may result from the summation of all these factors.

The use of contrast media in deceased kidney donors does not affect initial graft function or graft survival

Patients receiving cadaveric kidney transplants often experience delayed graft function. As iodinated contrast media injection (ICMI), necessary for cerebral angiography, which is often used to diagnose brain death, can be nephrotoxic, we compared renal function recovery (RFR) and 1-year and long-term graft survival according to the method used to diagnose brain death. Data from 9921 cadaveric kidneys, transplanted between 1 January 1998 and 31 December 2003, were retrieved from the French National Registry for organ donation. We defined RFR as the number of days for the recipient to reach a plasma creatinine less than 250 mumol/l, and/or a 24-h urine output greater than 1000 ml. RFR and 1-year and long-term graft survival were compared between four different donor groups (according to ICMI and diabetes mellitus). A total of 41.5% of deceased donors received ICMI before organ procurement and 1.95% of them were diabetic. History of ICMI or diabetes in the donor did not influence RFR or 1-year graft survival. Long-term graft survival was decreased in the group of patients transplanted with a diabetic graft as compared to patients transplanted with a non-diabetic graft (P=0.001). History of ICMI in the donor did not affect long-term graft survival in the non-diabetic donor group (P=0.2); however, in the diabetic group, ICMI tended to decrease long-term graft survival (P=0.056). ICMI did not affect RFR or graft survival in non-diabetic deceased donors. However, its use in diabetic deceased donors requires further study.

Effect of radiologic contrast media on cell volume regulatory mechanisms in human red blood cells

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate cell volume regulation in human red blood cells (RBCs) after incubation in solutions of three contrast media: iohexol (830 mOsm), ioxaglate (520 mOsm), and iodixanol (300 mOsm).

MATERIALS AND METHODS

Whole blood sampled from six healthy subjects was exposed to Ringer solutions containing 25% or 5% vol/vol iohexol (final osmolality, 440 or 340 mOsm, respectively), ioxaglate (final osmolality, 395 or 335 mOsm, respectively), iodixanol (final osmolality, 330 or 315 mOsm, respectively), or NaCl (control solutions with the same osmolality as that of the contrast media). In some experiments, control RBCs were subjected to a hyposmotic solution (100 mOsm). RBC volumes were obtained with a Coulter counter.

RESULTS

The RBCs showed normal regulatory cell shrinkage after hyposmotically induced swelling. All 25% vol/vol contrast material solutions and their control solutions induced RBC shrinkage (range, 6% +/- 1 [standard error] to 22% +/- 3). The same was true for cells exposed to 5% vol/vol contrast material (range, 4% +/- 1 to 7% +/- 1). The shrinkage phase was followed by cell swelling (10% +/- 2 to 20% +/- 2 for 25% contrast material and their control solutions and 8% +/- 1 to 15% +/- 2 for 5% contrast material and their control solutions). No contrast material-exposed RBCs increased their volumes to the level reached with their control solutions.

CONCLUSION

RBCs exposed to hyperosmotic iohexol, ioxaglate, or iodixanol solutions shrank and then swelled. The degree of shrinkage and subsequent swelling could not be explained simply with the osmolality of the test solutions. Physicochemical properties of the contrast media must be involved, putatively affecting electrolyte fluxes over the RBC membrane. Possible targets of these effects are the K+/Cl- symporter, K+ channels, and the Na+/K+/Cl- symporter.