Hans Dieperink

Management of an acute outbreak of diarrhoea-associated haemolytic uraemic syndrome with early plasma exchange in adults from southern Denmark: an observational study

BACKGROUND Diarrhoea-associated haemolytic uraemic syndrome in adults is a life-threatening, but rare multisystem disorder that is characterised by acute haemolytic anaemia, thrombocytopenia, and renal insufficiency. We aimed to assess the success of management of this disorder with plasma exchange therapy. METHODS Patients diagnosed with diarrhoea-associated haemolytic uraemic syndrome in southern Denmark were treated with daily plasma exchange by centrifugation and substitution with fresh frozen plasma. Stool culture and serological testing was done to identify the cause of disease, and the success of management with plasma exchange therapy was assessed from change in platelet count, glomerular filtration rate, and lactate dehydrogenase. FINDINGS During May 25-28, 2011, five patients with a median age of 62 years (range 44-70) presented with diarrhoea-associated haemolytic uraemic syndrome, which was caused by an unusual Shiga-toxin-producing Escherichia coli serotype O104:H4. Strains of E coli showed a high resistance to third-generation cephalosporins because the strains had extended-spectrum β lactamases. After plasma exchange, median platelet count and glomerular filtration rate increased, median lactate dehydrogenase concentration decreased, and neurological status improved. The time interval from onset of bloody diarrhoea to start of plasma exchange had an inverse correlation with reduction of lactate dehydrogenase concentrations by plasma exchange (p=0.02). All patients were discharged with normal neurological status at 7 days (range 5-8) after starting plasma exchange. INTERPRETATION Early plasma exchange might ameliorate the course of diarrhoea-associated haemolytic uraemic syndrome in adults. However, this finding should be verified in randomised controlled trials FUNDING None.

Nephrotoxicity of cyclosporin A in humans: effects on glomerular filtration and tubular reabsorption rates

Abstract. The contention that cyclosporin A (CyA) nephrotoxicity may be due to renal afferent arteriolar constriction was inferred from rat studies showing CyA to increase renal vascular resistance, to reduce glomerular filtration rate (GFR) and delivery of tubular fluid from the end of the proximal tubule to the loop of Henle (Vprox), and to increase proximal fractional reabsorption. In order to test whether the mechanism of human CyA nephrotoxicity is similar to its rat analogue, and whether CyA treatment causes prolonged renal malfunction after drug withdrawal, renal function was investigated with clearance techniques including lithium clearance (CLi) as a measure of Vprox. The subjects were patients (n= 11) with previously normal renal function, given CyA in the treatment of ocular manifestation of extrarenal disease, or bone‐marrow transplant recipients. Nine out of these eleven patients were investigated before and during CyA treatment: GFR (P<0·05) and Vprox (P<0·005) decreased while proximal fractional reabsorption increased (P<0·01). In six patients investigated before CyA was given, and re‐examined a mean of 273 days (range 84–384 days) after CyA withdrawal, CLi was reduced (P<0·05) while mean GFR was not significantly lowered (0·5>P > 0·2). In one of these six patients GFR was reduced to a subnormal value of 26 ml min‐1 (1·73m2 body surface)‐1. In conclusion, human and rat CyA nephrotoxicity have the same pattern of renal functional deterioration. Cyclosporin A nephrotoxicity was evident in patients investigated a mean of 9 months after CyA withdrawal.

Nephrotoxicity of cyclosporin A. A lithium clearance and micropuncture study in rats

Abstract. Renal function was studied in rats treated with cyclosporin A (CyA). Peroral CyA 25 mg kg‐1 day‐1 depressed glomerular filtration rate (GFR) from 1284 ± 429 to 500 ± 228 μl min‐1 g‐1 kidney weight (KW) (P < 0·01). Absolute rate of proximal tubular reabsorption (APR) decreased from 1075 ± 437 to 468 ± 203 μl min gKW‐1 (P < 0·01). Proximal tubular fractional reabsorption (PFR) was 67·7 and 68·5% measured with the TT/OT and fractional lithium‐clearance methods, respectively. Amiloride had no effect on lithium‐clearance in CyA treated rats. Acute isotonic volume expansion increased GFR and APR towards normal, while PFR remained increased. Increased sodium clearance did not normalize renal function. CyA intravenously (12·5 mg kg‐1) depressed GFR and APR acutely, while PFR increased. Proximal intratubular pressures were low normal (mean 11·6 mmHg). Proximal transit times were prolonged (mean 25·2 s, P < 0·01). Renal morphology was normal. The data are evidence against a primary tubular damage of CyA, and makes it less likely that the major lesion is located to the glomerular membrane. The results suggest that CyA nephrotoxicity mainly is due to a haemodynamic effect.

Antagonist capacities of nifedipine, captopril, phenoxybenzamine, prostacyclin and indomethacin on cyclosporin A induced impairment of rat renal function

Abstract. Experimental evidence indicates that cyclosporin A (CyA) nephrotoxicity is due to renal arteriolar constriction, reducing renal blood flow, glomerular filtration rate (GFR), and delivery of tubular fluid from the end of the proximal tubule to the loop of Henle. The proximal tubular fractional reabsorption (PFR) is increased. Therefore, the impact on renal function of vasodilating agents was studied in rats given CyA. Conscious catheterized rats and clearance techniques were used. In acute experiments a preexisting CyA‐nephrotoxicity was resistant to infusion of phenoxybenzamine, prostacyclin, captopril, nifedipine and indomethacin. Concomitant treatment with captopril and CyA did not improve renal function, while concomitant treatment with CyA and nifedipine improved GFR to 1·13±0·34 ml min‐1 g‐1 kidney weight (gKW) (n=19, P<0·05), as compared to CyA and placebo treated controls (n=12, 0·83±0·32 ml min‐1 g‐1 KW). Nifedipine also reduced FPR (88·6±5·1% vs. 83·2±5·6%. P<0·01), and increased lithium clearance from 99±54 to 184±64 μl min‐1 g‐1 KW (P<0·001). The results are further evidence that CyA nephrotoxicity includes renal vasoconstriction, and indicates that calcium entry blockade is nephroprotective in the case of CyA toxicity.

Impaired glomerular and tubular function as a short-term effect of sirolimus treatment in the rat.

Aims: To investigate acute and short-term effects of sirolimus (SRL) on glomerulo-tubular function, blood pressure (BP), and renal morphology in the rat. Methods: Male Sprague-Dawley rats, weighing initially 140–180 g were treated with SRL in three series: SRL 0.2, 0.4, or 0.8 mg/kg/day intraperitoneally for up to 28 days after skin allo-transplantation from Lewis donors (to establish a dosage with significant immunosuppressive effect). SRL 0.4 mg/kg intravenously (acute effects). SRL 0.4 mg/kg/day intraperitoneally for 7 days (short-term effects). Inulin, lithium (CLi) and sodium clearance, and intra-arterial BP were measured in conscious catheterized rats. Morphological kidney studies were completed after post-mortem fixation. Results: Maximum immunosuppressive effect was achieved with SRL 0.4 mg/kg/day. SRL acutely increased GFR and CLi, whereas fractional proximal reabsorption (PFR) declined. In the short-term study SRL had opposite effects on GFR and CLi, unaffected proximal tubular reabsorption and PFR, raised BP, diminished food consumption, and slower increase in body weight. Morphological changes were non-specific. Conclusion: In a dosage giving maximum immunosuppressive effect, SRL revealed acute effects on glomerular and proximal tubular function thus indicating increased outflow from the proximal tubules whereas one week of SRL treatment produced a change resembling the known nephrotoxic effects of the calcineurine inhibitors.

Cyclosporine/tacrolimus (FK-506)

The search for effective and safe methods of blocking the immune response has continued over the last four decades and has in fact permitted many advances in clinical organ transplantation. In the mid-1970s Borel et al.[1] discovered the immunosuppressive properties of a new agent, cyclosporine (CsA), that, unlike azathioprine and adrenal corticosteroids, selectively inhibits the adaptive immune response. This was the basis for its widespread clinical use during the 1980s and it had a major impact on the management of graft rejection in organ transplantation.

Hope for successful xenografting by immunosuppression with monoclonal antibody against CD4, total lymphoid irradiation and cyclosporine: six months' survival of hamster heart transplanted into rat

Hamster hearts were transplanted to rats, and the effects of combinations of total lymphoid irradiation (TLI), cyclophosphamide, cyclosporine A (CyA) and monoclonal antibodies (MAB) were investigated. Controls not immunosuppressed rejected their xenograft in 3 to 5 days, while combination immunosuppression including MABs against CD4 or IL-2-receptors extended graft survival significantly. In one case, the graft was still functioning 180 days after transplantation, which is the longest survival seen in this model. The use of specific MABs may open a new era for both xeno- and allo-transplantation.

The resistance of delayed xenograft rejection to α(1,3)‐galactosyltransferase gene inactivation and CD4 depletion in a mouse‐to‐rat model

Critical to the prevention of xenograft loss is the prevention of delayed xenograft rejection (DXR), due to its resistance to conventional immunosuppression. The role of the carbohydrate galactose‐α1,3‐galactose (α1,3Gal) has been a matter of great debate and it has been proposed that the reaction between α1,3Gal epitopes on donor endothelial cells and recipient anti‐α1,3Gal antibodies (Abs) may damage the graft during DXR. Recipient anti‐α1,3Gal Abs are produced by CD4‐dependent B cells. To test the above‐mentioned hypothesis, hearts from α1,3Gal‐free mice (GT‐Ko mice), generated by α1,3‐galacto‐syltransferase gene disruption, were transplanted to anti‐α1,3Gal antibody‐free Lew/Mol rats. This model consists of an α1,3Gal/α1,3Gal‐antibody‐free environment, eliminating a possible influence of this specific system on DXR. A subgroup of recipients were furthermore CD4 depleted in order to inhibit CD4‐dependent B‐cell antibody production. Rejected hearts were evaluated by light‐ and immunofluorescence microscopy. Treatment effects on recipient T‐cell subsets and cytokine expression were analyzed by flow cytometry, while antibody production was measured by ELISA. All recipients developed DXR with no differences among the groups. DXR was related to thrombosis with IgG and IgM desposition in vessel walls, as well as macrophage and granulocyte accumulation in the myocardium. No complement C3, CD4 cells or NK cells were found. Flow cytometric analysis confirmed peripheral blood CD4 depletion and IFN‐γ suppression in CD4 Ab‐treated recipients. Finally, ELISA showed that specific anti‐α1,3Gal Ab production was absent. However, Ab(s) against an unidentified Galα 1 were found among recipients. In our model, DXR is resistant to α1,3‐galactosyltransferase gene inactivation and CD4 depletion. However, other Galα 1 epitopes and antibodies may play a role during DXR. Further studies are needed to elucidate the precise pathways leading to DXR.

Segmental Tubular Sodium Reabsorption in Type 1 Diabetes

Segmental tubular sodium reabsorption in Type 1 (insulin‐dependent) diabetes was measured in 36 patients in a cross‐sectional study including one group (n = 13) without significant albuminuria (UalbV < 30 mg 24 h−1), one group (n = 16) with albuminuria in the range from 30 to 300 mg 24 h−1, and a group (n = 7) with nephropathy (UalbV > 300 mg 24 h−1). Lithium clearance was used to measure end proximal delivery. From end proximal delivery, 51Cr‐EDTA clearance (GFR) and sodium clearance, segmental tubular reabsorption was calculated. For all patients, GFR was directly correlated with end proximal delivery (r = 0.62, p<0.0005), while end proximal delivery was inversely correlated to fractional proximal reabsorption (r = −0.71, p<0.0005). In the subgroup with UalbV less than 30 mg 24 h−1, the direct correlation between GFR and end proximal delivery was also significant (r = 0.77, p<0.05). In the group with nephropathy (UalbV > 300 mg 24 h−1), mean GFR and end proximal delivery were decreased and fractional proximal reabsorption was increased, but there was still a positive correlation between GFR and end proximal delivery (r = 0.75, p<0.05) and an inverse correlation between end proximal delivery and fractional proximal reabsorption (r = −0.85, p<0.05). It is concluded that in these groups of diabetic patients the end proximal delivery is increased while GFR is increased. This finding is an argument against a recent hypothesis explaining intraglomerular hypertension, as well as increased glomerular filtration rate in some patients, as secondary to decreased end proximal delivery and reduced tubuloglomerular feedback activity. Nevertheless, the tubuloglomerular feedback activity may be reduced in Type 1 diabetes due to constant extracellular volume expansion.

Pinacidil - Effects on Function and Perfusion of Normal Kidneys and Renal Xe nog rafts

Pinacidil is a new vasodilating compound claimed to increase renal perfusion and function. A preliminary study showed that pinacidil did not sustain renal perfusion through a period of increasing renal vascular resistance in pig-to-rabbit renal xenotransplantation. Accordingly, the effect of pinacidil on renal function in conscious catheterized rats was studied. Pinacidil 0.12-0.18 mg/kg i.v. caused a moderate reduction in mean arterial blood pressure (14-17 mmHg), a decrease in inulin and PAH clearances (50-65%), and sodium and water retention. The sodium clearance/lithium clearance ratio decreased, suggesting increased sodium reabsorption in the distal nephron during pinacidil administration. Thus the results are in accord with those obtained with several other vasodilators, but not with those obtained in mongrel dogs during pinacidil administration.