Pharmacologic agents used in the management of acute renal failure

Acute renal ischemia model in dogs: effects of metoprolol

INTRODUCTION

To study the functional and histological alterations in dog kidneys submitted to total ischemia for thirty minutes and the possible metoprolol protective action.

MATERIAL AND METHODS

Sixteen dogs anesthetized with sodium pentobarbital (SP) were studied and divided into two groups: G1-8 dogs submitted to left nephrectomy and right renal artery clamping for thirty minutes, and G2-8 dogs submitted to the same procedures of G1 and to the administration of 0.5 mg x kg(-1) metoprolol before ischemia. Attributes of renal function were studied.

RESULTS

There was acute tubular necrosis and a decrease of renal blood flow and glomerular filtration, and a increase of renal vascular resistance in both groups.

CONCLUSION

The thirty minute renal ischemia appears to have determined the alterations found in the renal function and histology in both groups. Metoprolol, used in G2, as to the time and dose applied didn't protect the kidney from the ischemic episode.

Effect of YM435, a dopamine DA1 receptor agonist, in a canine model of ischemic acute renal failure

1. The effects of (-)-(S)-4-(3,4-dihydroxyphenyl)- 1,2,3,4-tetrahydroisoquinoline-7,8-diol monohydrochloride monohydrate (YM435), a dopamine DA1 receptor agonist, were evaluated in a canine model of ischemic acute renal failure (ARF). 2. ARF was induced by clamping the left renal artery for 1 hr and subsequent reperfusion of the left kidney in anesthetized uninephrectomized dogs. 3. After 1-hr complete renal artery occlusion, an intravenous infusion of either YM435 (0.3 microg/kg/ min) or 0.9% saline (vehicle) was begun and continued for 1 hr. 4. In the vehicle group, renal ischemia markedly decreased glomerular filtration rate, urine flow and urinary sodium excretion. The YM435 group was characterized by significant recoveries in glomerular filtration rate, urine flow, and urinary sodium excretion as compared with the vehicle group. 5. These results indicate that YM435 can facilitate recovery in glomerular filtration rate, urine flow, and urinary sodium excretion in a canine model of ARF induced by ischemia. YM435 may be useful in the preservation of renal function in ischemia-induced ARF.

Protein-restricted diet prior to renal insult improves the recovery of renal function following ischemia

The effects of a protein-restricted diet on renal recovery following renal ischemia were studied. The renal function was assessed by measuring the inulin clearance (CIN), the p-aminohippurate clearance (CPAH), and the percent fractional sodium excretion (%FENa) 24 h after 45 min renal ischemia. In rats fed with a regular diet (containing 19.6% protein), CIN was 10.0 +/- 2.2 microL/min/100 g body weight (BW), CPAH 0.08 +/- 0.02 mL/min/100 g BW, and %FENa 14.8 +/- 2.0, 24 h after renal ischemia. In contrast, feeding rats with a no-protein diet (0% protein) for 1 week prior to the ischemic insult significantly improved renal recovery (CIN 48.0 +/- 9.3 microL/min/100 g BW, CPAH 0.16 +/- 0.04 mL/min/100 g BW, and %FENa 2.43 +/- 0.58). Feeding rats with a no-protein diet for 3 weeks prior to ischemic insult further improved the renal recovery (CIN 113 +/- 30 microL/min/100 g BW, CPAH 0.47 +/- 0.17 mL/min/100 g BW, and %FENa 1.55 +/- 0.29). When rats fed with a regular diet were exposed to 45 min of ischemia, the survival rate on day 7 was 16.7%. In rats fed with the no-protein diet for 1 week and for 3 weeks, the 7-day survival rate was 100% in each case. The survival rate of rats fed for 3 days instead of 7 days with the no-protein diet was 87.5%. When a no-protein feeding was shortened to 1 day, no beneficial effects were observed and survival rate was 14.3%. (ABSTRACT TRUNCATED AT 250 WORDS)

High doses of furosemide in children with acute renal failure. A preliminary retrospective study

The diuretic effect of high doses of furosemide alone and furosemide plus mannitol was analysed retrospectively in 30 children with acute renal failure. In 10 children (Group 1) renal failure developed mainly during glomerulonephritis, and in 20 children (Group 2) the cause was gastroenteritis. The diuretic effects of furosemide and furosemide plus mannitol were evaluated measuring the 24-hour urine volume at the time of anuria, oliguria or normal diuresis. The highest mean single intravenous doses of furosemide were 6.5 and 14 mg/kg in Groups 1 and 2, respectively; the highest average daily doses were 10.1 and 25.5 mg/kg, respectively. A broad relationship was observed between single i.v. dose and diuretic response following administration of furosemide (1.2 to 30.8 mg/kg). In both groups of patients a statistically significant negative linear correlation was found between the daily intravenous dose of furosemide and the 24-hour urine volume. Calculations based on the obtained regression equations showed that the expected 24-hour urine volumes corresponding to daily diuresis normal for age could be obtained after administration of daily 2.8 to 1.4 mg/kg furosemide in Group 1 and 9.3 to 2.3 in Group 2. It is therefore suggested that the total daily dose of furosemide should not exceed 100 mg in children with acute renal failure. Administration of furosemide plus mannitol did not result in higher daily diuresis as compared to 24-hour urine volume obtained when furosemide was given alone. Furosemide was well tolerated. Electrolyte disturbances, especially in Group 2, were the most frequent side effects due to high doses of furosemide.

Long-term effects of acetazolamide and sodium chloride loading on cisplatin nephrotoxicity in the rat

The protective effect of acetazolamide or sodium chloride loading on cisplatin nephrotoxicity was investigated in rats. After a single dose of cisplatin (5 mg kg-1 i.p.) kidney function was studied after 5, 28 and 84 days. Acetazolamide (75 mg kg-1 i.p.) was administered as a single dose prior (30 min) to the cisplatin injection. By the time of cisplatin administration, the rats were sodium depleted except the sodium-loaded group. Five days after the cisplatin administration all rats received a regular rat chow for the rest of the experiment. Cisplatin alone caused renal failure that could be observed for up to 12 weeks (ClCr 0.32 +/- 0.13 vs. 0.62 +/- 0.06 ml min-1 x 100 g BW-1) with polyuria (UVol 41.2 +/- 4.5 vs. 18.4 +/- 4.6 ml 24 h-1). Pretreatment with acetazolamide was the most protective manoeuvre tested. Five days after cisplatin, kidney function was significantly better than in rats treated with cisplatin alone (ClCr 0.21 +/- 0.06 vs. 0.03 +/- 0.01 ml min-1 x 100 g BW-1), after 28 days the only sign of nephrotoxicity was polyuria (UVol 28.9 +/- 3.7 vs. 19.0 +/- 2.6 ml 24 h-1) after 84 days no differences could be observed at all. Sodium chloride loading was less protective on cisplatin nephrotoxicity. Impaired renal function could still be observed after 12 weeks (ClCr 0.41 +/- 0.05 vs. 0.62 +/- 0.06 ml min-1 x 100 g BW-1) with no difference in comparison with the rats treated with cisplatin alone. However, since 12 rats died in the group having received cisplatin alone and only one rat in the high-salt group, sodium chloride loading is regarded as being advantageous over sodium depletion on cisplatin nephrotoxicity.

Acute renal failure

Although a wide variety of disease processes can result in a failure of renal excretory function, the vast majority of cases with "acute renal failure" (ARF) are due to the syndrome of acute tubular necrosis (ATN). The syndrome is usually initiated by an acute injury to the proximal renal tubular epithelial cells by ischemic or nephrotoxic events. This is followed by progressive and often rapid increases in the concentration of blood urea nitrogen (BUN) and serum creatinine. In the average case, the failure of renal excretory function persists for 1 to 3 weeks, to be followed by recovery. Oliguria (urine volume less than 400 ml) is present in about half of the patients. The pathogenesis of the retention of nitrogenous waste in human ATN is the subject of controversy, but the balance of data in most patients suggests that the predominant mechanism is a profound secondary vasoconstriction in response to tubular cell injury. This may represent a teleologically appropriate response to prevent catastrophic losses of fluid that would occur, if the normally high rates of glomerular filtration continued, in the face of reduced tubular reabsorptive capacity. The mechanisms by which the tubular cell injury is communicated to the vasculature, and the mediators of the hemodynamic changes, remain to be established. The differential diagnosis in a patient with ARF, usually involves exclusion of an obstruction to the urinary tract as an initial step. The next step is to differentiate the patients with ATN from those who have renal hypoperfusion in response to events in the systemic circulation, but who otherwise have functionally and structurally intact kidneys, i.e., prerenal ARF. The kidneys of patients with prerenal ARF exhibit the normal renal response to an acute reduction in renal blood flow and glomerular filtration rate (GFR). This consists of avid reabsorption of the filtered salt and H2O, so that a small amount of concentrated and NaCl-poor urine is elaborated. The tubular cell injury in ATN syndromes prevents this response from maximally occurring, so that the urine is isosmotic and relatively rich in NaCl.

Intrarenal blood coagulation induced by ischemia in rats. Heparin and thrombocytopenia does not prevent the intracortical fibrin formation

In various human and experimental renal failures some hemostatic parameters indicate the occurrence of intrarenal blood coagulation (1, 2). However, the fact that the common anticoagulants fail to cure the acute renal failure (3) appears to suggest either that they are ineffective against the intrarenal blood coagulation or no causal relationship exists between the hemostatic disturbances and impaired renal function. Therefore this study was undertaken to investigate the relationship between coagulation and impairment of renal function after a 45-min ischemic period in untreated, heparin-treated and in heparin- plus antiplatelet serum (APS)-treated thrombocytopenic animals.