Acute renal failure due to nephrotoxins

Applying Metabolomics and Aptamer-based Proteomics to Determine Pathophysiologic Differences in Decompensated Cirrhosis Patients Hospitalized with Acute Kidney Injury

A case-control study of 97 patients hospitalized at our institution. We performed aptamer-based proteomics and metabolomics on serum biospecimens obtained within 72 hours of admission. We compared the proteome and metabolome by the AKI phenotype (i.e., HRS-AKI, ATN) and by AKI recovery (decrease in sCr within 0.3 mg/dL of baseline) using ANCOVA analyses adjusting for demographics and clinical characteristics. We completed Random Forest (RF) analyses to identify metabolites and proteins associated with AKI phenotype and recovery. Lasso regression models were developed to highlight metabolites and proteins could improve diagnostic accuracy. Results: ANCOVA analyses showed no metabolomic or proteomic differences by AKI phenotype while identifying differences by AKI recovery status. Our RF and Lasso analyses showed that metabolomics can improve the diagnostic accuracy of both AKI diagnosis and recovery, and aptamer-based proteomics can enhance the diagnostic accuracy of AKI recovery. Discussion: Our analyses provide novel insight into pathophysiologic pathways, highlighting the metabolomic and proteomic similarities between patients with cirrhosis with HRS-AKI and ATN while also identifying differences between those with and without AKI recovery.

Extravasation of Blood and Blood Toxicity Drives Tubular Injury from RBC Trapping in Ischemic AKI

Red blood cell (RBC) trapping is common in ischemic acute kidney injury (AKI) and presents as densely packed RBCs that accumulate within and engorge the kidney medullary circulation. In this study, we tested the hypothesis that "RBC trapping directly promotes tubular injury independent of extending ischemia time." Studies were performed on rats. Red blood cell congestion and tubular injury were compared between renal arterial clamping, venous clamping, and venous clamping of blood-free kidneys. Vessels were occluded for either 15 or 45 min with and without reperfusion. We found that RBC trapping in the medullary capillaries occurred rapidly following reperfusion from renal arterial clamping and that this was associated with extravasation of blood from congested vessels, uptake of blood proteins by the tubules, and marked tubular injury. To determine if this injury was due to blood toxicity or an extension of ischemia time, we compared renal venous and arterial clamping without reperfusion. Venous clamping resulted in RBC trapping and marked tubular injury within 45 min of ischemia. Conversely, despite the same ischemia time, RBC trapping and tubular injury were minimal following arterial clamping without reperfusion. Confirming the role of blood toward tubular injury, injury was markedly reduced in blood-free kidneys with venous clamping. Our data demonstrate that RBC trapping results in the rapid extravasation and uptake of blood components by tubular cells, causing toxic tubular injury. Tubular toxicity from extravasation of blood following RBC trapping appears to be a major component of tubular injury in ischemic AKI, which has not previously been recognized.

Intrarenal arteriovenous shunts in kidney transplants demonstrated by contrast-enhanced ultrasound

The kidney can undergo several hemodynamic changes in response to physiological stressful conditions. Arteriovenous (AV) shunting is an example where renal blood flow is redistributed away from the cortex toward the metabolically vulnerable medulla. Identification of this phenomenon is important as it may reflect underlying pathology. Despite evidence of renal AV shunting, its existence has been questioned. To our knowledge, this case series demonstrates for the first time the presence of renal AV shunting using contrast enhanced ultrasound.

Chronic kidney disease: an inherent risk factor for acute kidney injury?

Epidemiologic evidence suggests that chronic kidney disease (CKD) is a risk factor for acute kidney injury (AKI) due to the prevalence of CKD in patients who have episodes of AKI. However, the high burden of comorbidities such as age, diabetes, peripheral vascular, cardiovascular, and liver disease accompanying CKD, and the difficulties of defining AKI in the setting of CKD make these observations difficult to interpret. These comorbidities not only could alter the course of AKI but also may be the driving force behind the epidemiologic association between CKD and AKI because of systemic changes and/or increased exposure to potential nephrotoxic risks. Here, we contend that studies suggesting that CKD is a risk factor for AKI may suffer from residual confounding and reflect an overall susceptibility to illness rather than biologic susceptibility of the kidney parenchyma to injury. In support of our argument, we discuss the clinical evidence from epidemiologic studies, and the knowledge obtained from animal models on the pathophysiology of AKI and CKD, demonstrating a preconditioning influence of the previously impaired kidneys against subsequent injury. We conclude that, under careful analysis, factors apart from the inherent pathophysiology of the diseased kidney may be responsible for the increased frequency of AKI in CKD patients, and the impact of CKD on the risk and severity of AKI needs further investigation. Moreover, certain elements in the pathophysiology of a previously injured kidney may, surprisingly, bear out to be protective against AKI.

Renal plasma flow and glomerular filtration rate during acute kidney injury in man

During acute kidney injury (AKI), lowered glomerular filtration rate (GFR) is believed to be consequent to reduced renal plasma flow (RPF). We aimed to systematically evaluate the evidence for such an association. Using specific search terms, we systematically interrogated the Pub Med electronic reference database for studies of human AKI where renal plasma or blood flow and GFR were measured; older articles were then identified by screening bibliographies of retrieved reports. We identified 22 articles describing 250 patients (203 native kidney, 47 in renal allograft). Of these studies, 8 articles (110 patients) estimated effective renal plasma flow (ERPF) by clearance techniques and 14 articles (140 patients) estimated true renal plasma flow (TRPF). Mean RPF was 272 mL/min (95% CI 213-331) and GFR 13.9 mL/min (9.9-17.9). Mean TRPF was significantly greater than mean ERPF (344 vs. 180, p=0.004) despite lower mean GFR (8.8 vs. 20.4, p=0.002). There was no significant association between RPF and GFR between studies. Eleven studies presented individual patient data (76 patients: 49 TRPF, 27 ERPF); here, individual patient ERPF was associated with GFR (r2=0.52), but TRPF was not. During AKI in man, there is only a limited association between ERPF and GFR, and no detectable association between TRPF and GFR.

The pathophysiology of acute renal failure

This article summarizes the pathophysiology of acute renal failure from both experimental and clinical points of view. Prerenal acute renal failure is an appropriate physiologic response to renal hypoperfusion and can complicate any disease characterized by either true hypovolemia or a reduction in the effective circulating volume. In acute tubular necrosis, the abrupt fall in glomerular filtration rate is thought to be caused by interplay of hemodynamic and tubular abnormalities. The postischemic kidney also shows a dramatic capacity for recovery. The molecular mechanisms and the effect of growth factors are also summarized.

Continuous measurements of renal perfusion in pigs by means of intravascular Doppler

BACKGROUND

Changes in renal blood flow are considered to play a significant role in the induction and maintenance of kidney failure, but are difficult to monitor with currently available techniques. The objective was to validate renal flow measurements with Doppler guidewires and to apply this technique to assess dose and time dependency of the renal vascular effects of norepinephrine (NE).

METHODS

In 10 anesthetized pigs, flow velocity in renal arteries (FVart) and veins (FVvein) and volumetric renal blood flow (VBF) were measured before and after intravenous bolus application of incremental doses of NE (2 to 200 microg).

RESULTS

FVart curves exactly reflected the changes in VBF. Beat-to-beat analysis revealed a strong linear correlation over a mean VBF range of less than 0.05 to 0.35 L/min (median correlation coefficient with FVart, r = 0.998), and significant but less close relationships were also found between VBF and FVvein. Ten seconds after the administration of 200 microg NE, FVart dropped from 71 to 6 cm/sec and was 90% reversible after 48 seconds. Similarly, the renal vascular resistance temporarily rose from 988 to 13711 mm Hg. min/L. In contrast, NE-induced increases in systemic vascular resistance were on average a maximum of 1.5-fold but persisted for more than 60 seconds.

CONCLUSIONS

Doppler flow measurements in the renal artery provide an excellent surrogate of volumetric blood flow, which may be useful for continuous monitoring of renal hemodynamics. The renal vasculature is more sensitive when compared with the systemic vasculature, but also appears to evoke more efficient counter-regulatory mechanisms in response to NE.

The nutrition management of the patient with acute renal failure

The clinical status of patients with acute renal failure (ARF) varies greatly. Some individuals have only mild or moderate ARF or may have only mild perturbations of their metabolic status. Other patients exhibit a severe reduction in renal function with oliguria or anuria. Depending upon their comorbid conditions, ARF patients may be among the most hypercatabolic patients in the hospital. Clinical trials have not clearly shown a beneficial effect of nutrition support on morbidity or mortality in patients with ARF, although limitations in sample size and experimental design and inclusion of patients with widely disparate clinical conditions may have contributed to the difficulty in demonstrating benefits. Several recent therapeutic approaches that have been studied either in experimental animals with ARF or in small numbers of humans with ARF hold promise for improving clinical outcome. Continuous arteriovenous or venovenous hemofiltration with or without dialysis is such a therapy. In comparison to intermittent hemodialysis this former treatment more safely removes large quantities of water and solutes from critically ill patients with unstable hemodynamics and allows them to receive rather large quantities of nutrients, including amino acids. Also promising are studies in experimental animals with ARF which indicate that several growth factors may accelerate the recovery of renal function. In rats with ARF, insulin-like growth factor 1 both enhances recovery of renal function and suppresses their enhanced catabolism. For most patients with ARF requiring nutrition support, evidence suggests that both essential and nonessential amino acids should be employed. However, there appears to be a therapeutic role for small quantities of essential amino acids, without nonessential amino acids, in selected patients. Data support the importance of proactive measures to prevent fluid and electrolyte imbalances in patients with ARF.

Nitric oxide mediates redistribution of intrarenal blood flow during bacteremia

The normal or hyperdynamic circulatory response during the early phases of the systemic septic response is associated with renal microvascular constriction and can result in renal dysfunction. Intrarenal redistribution of blood flow from the outer cortex to the medulla appears to account for decreased glomerular filtration in spite of normal or elevated renal blood flow, but the mechanisms of this response are not well described. Nitric oxide is recognized as an important regulator of regional blood flow during both normal and pathologic conditions including sepsis, and we hypothesized that alterations in nitric oxide contribute to redistribution of renal blood flow during sepsis. The current study used laser Doppler fluximetry and clearance of p-aminohippuric acid (effective renal plasma flow, ERPF) to study intrarenal distribution of blood flow during basal conditions and during normodynamic Escherichia coli bacteremia, with and without inhibition of nitric oxide. Inhibition of nitric oxide in normal animals resulted in a decrease in ERPF (-19%) with a decrease in cortical flux (-39%) without alteration of medullary flux. Bacteremia resulted in a decrease in cortical flow (-17%), an increase in medullary flow (36%), and a modest reduction (-9%) in ERPF. Inhibition of nitric oxide synthase during bacteremia worsened cortical flow (-43%), reversed the increase in medullary flux (-42%), and further impaired ERPF (-28%). These data suggest that nitric oxide regulates renovascular tone during normal conditions and bacteremia, and indicate that it is a prime mediator of intrarenal redistribution of blood flow during sepsis.

Profound hypotension and sodium retention with the ovarian hyperstimulation syndrome

A 34-year-old woman developed profound hypotension and sodium retention following hormonal induction of ovulation. There was a transient response to infusion of albumin, but hypotension and hyponatremia persisted for 5 days. Nevertheless, acute renal failure did not develop. Available information indicates that this syndrome can occur with exogenous administration of gonadotrophic hormones or with a successful pregnancy.

The measurement of blood flow in humans using radioactive tracers

Since the first description of the movement of blood around the body by William Harvey, the accurate measurement of blood velocity has provided a major challenge for medical science. This review looks at the contribution made by techniques using radioactive tracers. Initially consideration is given to the fundamental problem of how to measure the amount of radiotracer in an organ with sufficient accuracy, using both single-photon and positron-emitting tracers. The various models used to link tracer behaviour with blood flow are then discussed and the article closes with a detailed review of the clinical applications of blood flow measurements.

Ischemic acute renal failure

Underperfusion of the kidneys often results in the development of ischemic acute renal failure. This review summarizes the recent developments in the understanding of the pathophysiology, diagnosis, and treatment of this serious and costly disorder that affects almost 5% of hospitalized patients.

Postischaemic renal cortical microcirculation and tissue oxygenation in the pig

Porcine and human renal physiology are similar in important aspects. Renal cortical microcirculation and its relation to inulin clearance (CIn) was therefore studied before and after renal ischaemia in 28 pigs under continuous intravenous chlormethiazole-pancuronium anaesthesia. The anaesthesia used provided essential stability in central haemodynamics. The animals were studied for 90 min of reperfusion following 0, 30 or 60 min of renal ischaemia. Twelve of the animals (four were subjected to each duration of ischemia) were also studied 18 h after start of reperfusion. Regional blood flow in the superficial renal cortex was measured by laser Doppler flowmetry (LDF), and tissue oxygenation (PtO2) by surface microelectrode technique. These techniques allow continuous or repeated measurements. During the first 90 min of reperfusion, superficial renal cortical blood flow measured by LDF (Qsrc) underwent considerable temporal variation which followed a certain pattern. Thus, when the renal arterial blood flow was restored after ischaemia, we observed an instant peak in Qsrc followed by a decreasing flow until a minimum value (Qmin) was reached between 3 and 9 min after start of reperfusion (tQmin). Thereafter, Qsrc increased until a maximal value (Qmax) was reached between 11 and 64 min after start of reperfusion (tQmax). The parameters tQmin and tQmax were related to inulin clearance 18 h after start of reperfusion (P less than 0.05 and P less than 0.01, respectively). Thus, it might be possible soon after start of reperfusion--to evaluate the severity of ischaemic damage. This could be useful in the evaluation of different prophylactic strategies, since the full extent of the ischaemic damage, as assessed by clearance determinations, cannot be established until hours later.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive monitoring of renal blood flow characteristics during acute renal failure in man

Duplex Doppler ultrasound (DDU) was used to study the blood flow characteristics of the renal interlobar artery in 20 subjects with acute renal failure (ARF), 14 subjects with transient impairment of renal function and 23 control subjects with normal function. Renovascular resistance was assessed by pulsatility index (PI) and change in flow velocity by change in mean frequency shift (delta f). The 99% confidence intervals for PI in the three groups were 3.32-5.46, 1.58-2.34 and 0.99-1.33 respectively. Values for delta f were 0.2-0.38, 0.5-0.62 and 0.7-1.02 kHz respectively. Ten ARF patients recovered function, 99% confidence intervals for PI just prior to recovery were 0.9-1.48 and for delta f 0.52-1.02 kHz. There was increased renovascular resistance and reduced intrarenal blood flow velocity at the onset of ARF. These changes persisted during ARF; recovery of function occurred after they returned to normal. Similar, but less marked, changes were found in patients with a transient impairment of function.

Glomerular hemodynamics in mercury-induced acute renal failure

As manifest by tubular collapse and the virtual absence of flow into the glomerulotubular junction (GTJ), filtration in most nephrons (SNGFR) of rats poisoned with 9 mg/kg body wt HgCl2 16 to 28 hours earlier was virtually absent. Arterial colloid osmotic pressure (COPA) and Bowman's space pressure (PBS) were modestly depressed (P less than 0.05 or below), and mean blood pressure was reduced from 115 +/- 2 mm Hg (SEM) to 97 +/- 1 mm Hg (P less than 0.001). Glomerular capillary hydraulic pressure (Pg), 25.6 +/- 1.3 mm Hg was some 24 mm Hg lower than control (P less than 0.001) and yielded a net afferent effective filtration pressure (Pnet) of 4.1 +/- 1.2 mm Hg. Excluding three rats with values greater than 10 mm Hg, Pnet averaged 2.0 +/- 0.9 mm Hg (N = 17 rats) versus 20.0 +/- 1.8 mm Hg in controls (N = 10, P less than 0.001), the former being statistically almost indistinguishable from 0 mm Hg and barely able to support any filtration. This decrease in Pg was caused by a major increase in preglomerular resistance (RA) and a reciprocal fall in efferent arteriolar resistance (RE), the RA/RE ratio of 7.2 +/- 0.8 being fourfold higher than control (P less than 0.001). Renocortical blood flow was not different from control (P greater than 0.2). A wide spread of Pg values in individual glomeruli and the absence of tubular flow despite the appearance of i.v. injected lissamine green in a quadrant of surface glomeruli suggested the possibility of a greatly increased, glomerular capillary resistance. It is concluded that reciprocal changes in RA and RE are the immediate cause of filtration failure in this form of ARF and that, in the virtual absence of filtration, tubular leakage can play no important role. Since PBS was depressed in both the developmental and established phases of ARF, tubular obstruction appears to play no direct role in the pathogenesis of this particular model of murine acute renal failure.

The pathophysiology of severe falciparum malaria

By the end of the 1940s, the clinical and pathological features of severe falciparum malaria had been well described by military physicians and pathologists working in theatres of war where the disease was endemic. From that time serious efforts were made to discover the pathophysiology of the severe manifestations of malaria because an understanding of these mechanisms forms an important basis for the clinical management of affected patients. Recently, after a period of neglect, there has been a revival of interest in malaria as a subject for clinical and laboratory research. In this article, Rodney Phillips and David Warrell review aspects of that work and attempt to unravel the mysteries of the pathophysiology of severe malaria in man.

Selective inhibition of thromboxane synthesis in glycerol-induced acute renal failure

It has recently been postulated that thromboxane A2 may participate in the pathogenesis of acute myohemoglobinuric experimental acute renal failure. To investigate this further, the effect of selective inhibition of thromboxane synthesis on the course of glycerol-induced acute renal failure was determined. Despite significant inhibition of thromboxane synthesis by 4-imidazole-yl-acetophenone, the functional and morphologic disturbance induced by glycerol was unaltered. Moreover, pretreatment with 4-imidazole-yl-acetophenone failed to prevent the fall in renal blood flow seen following glycerol administration. These results argue against a major role for thromboxane A2 in the pathogenesis of this form of experimental acute renal failure.

Pathophysiology of haemorrhagic shock

The immediate effect of sudden blood loss is the activation of a variety of homeostatic responses. These include increased sympathetic activity and increased release or production of renin, angiotensin, anti-diuretic hormone, aldosterone, adrenocorticotrophic hormone, beta-endorphins, glucocorticoids, glucagon, erythropoeitin, 2-3 diphosphoglycerate, prostaglandins and complement. This may be followed by the release of many substances, some initially appropriate locally, and some the products of damaged cells, which may go on to cause both local and systemic damage. These include lysosomal enzymes, kinins, histamines, serotonin, lactic acid, free oxygen radicals, neutrophil proteases, fibrinogen degradation products, endotoxins, myocardial depressant polypeptides, and passive transferable lethal factor. The early and late effects on the cardiovascular and respiratory systems, and on the blood, brain, kidneys, gut, liver, pancreas, and on overall metabolism and cellular function, are considered in turn. Although an enormous research effort has increased our understanding of the pathophysiology of haemorrhagic shock, no special measures have yet been shown to influence morbidity or mortality in man. Management still hinges on the early recognition and treatment of bleeding, on general supportive measures, and on safeguarding each link in the oxygen delivery chain.

Hemodynamic basis for human acute renal failure (vasomotor nephropathy)

Oliguric acute renal failure in man is characterized by intense outer cortical vasoconstriction and a marked increase in preglomerular resistance. The degree of preglomerlar resistance change needed to cause the expected 50 to 80 percent fall in blood flow far exceeds the level that would totally abolish filtration. By contrast, equal 3.0-fold increases in both pre- and postglomerular resistance provide this same degree of ischemia but leave filtration very well maintained. Such a scenario seems unlikely, however, since it would entail a mere 15 to 25 percent decrease in preglomerular resistance vessel caliber rather than the extreme attenuation observed. By contrast, there are reasons to believe that preglomerular constriction may be accompanied by postglomerular vascular relaxation. In sum, unless cortical ischemia reflects precisely matched increases in pre- and postglomerular resistances, filtration failure is inevitable in human vasomotor nephropathy.

Assessment of the nephrotoxic potential of ceftazidime and a ceftazidime/tobramycin combination in volunteers

Ten informed healthy volunteers with normal renal function received 2 X 3.0 g ceftazidime intravenously for three consecutive days. Four weeks later, ceftazidime was combined with 1 X 3 mg/kg body weight tobramycin, administered intramuscularly, for three consecutive days. The effect of the two treatments on parameters used to assess renal function was examined prior to administration, during administration for three days and for a follow-up period. Alanine-aminopeptidase (AAP) levels in 24 h urine samples were measured in addition to kidney function parameters. The urine from the volunteer who had shown the highest AAP levels in each series was examined by ultracentrifugation for the presence of membrane particles with AAP activity. Ceftazidime showed no effect on the proximal tubular membrane. No increased elimination of AAP could be demonstrated. The kidney function parameters remained unchanged. The combination of ceftazidime with tobramycin led to a cumulative increase in AAP activity which was not significantly different from the increase observed when the same dose of tobramycin is administered alone. No additive effects could be demonstrated. Ultracentrifugation showed no indication of an impairment of the membrane integrity when ceftazidime was administered alone or in combination with tobramycin.

Acute tubular necrosis in hepatorenal syndrome: an electron microscopy study

This report describes light and transmission electron microscopy (LM and EM, respectively) studies of kidneys from five cases of hepatorenal syndrome. The kidneys were removed and fixed for LM and EM between 30 and 120 min after death. All patients had progressive renal failure after admission to the hospital. All cases were jaundiced, had ascites, and exhibited features of hepatic encephalopathy. LM study revealed severe acute tubular lesions (ATL) or, more conventionally, acute tubular necrosis (ATN). EM study demonstrated necrosis of the proximal tubules characterized by swelling, disorganization of the cristae and appearance of dark bodies in the mitochondria, coalescence, fragmentation or displacement of the microvilli, loss of plasma membranes, rupture of the basement membranes, and separation of the cells from the basement membranes. Rupture of tubular basement membranes (tubulorrhexis) and mitochondrial dark bodies suggest an ATN due to ischemia or induced by vasoconstrictor substance(s). Glomerular lesions were infrequent (one in five) and therefore, do not seem to have contributed to renal failure. All cases terminally had extremely low urinary sodium (11 mEq/liter), high urinary potassium (50 mEq/liter), a remarkably low urinary sodium/potassium ratio (0.26, normal = 4.27), and a low urinary osmolality (less than 400 mOsm/kg). From this study we conclude that an ATN of variable severity may be associated with the hepatorenal syndrome. Since this ATN developed without preceding shock, sepsis, or hypotension it is possible that this ATN like that in ischemic acute renal failure may be due to reduced renal blood flow and intense cortical vasoconstriction which has been reported in hepatorenal syndrome. Finally, our data imply that low urinary sodium is consistent with this pathologic lesion in this clinical setting.

Contrast medium-induced renal vasoconstriction and endogenous vasoconstrictor hormones

Hypertonic solutions, such as contrast media (meglumine/sodium diatrizoate-76%; Renografin-76), induce vasoconstriction in the renal vascular bed via an unknown mechanism. We assessed a possible role of two vasoconstrictor hormones known to be released by the kidney, angiotensin II (AII) and the prostaglandin, thromboxane. Specific inhibition of AII at the smooth muscle receptor level by saralasin (0.33-0.75 microgram/kg/min, IA) did not attenuate the response. Inhibition of prostaglandin formation by indomethacin (4 mg/kg, IV), likewise, did not prevent the decrease in renal perfusion. We conclude that neither AII nor the prostaglandin system mediate the contrast medium-induced renal vasoconstriction.

Nephrotoxicity of cis-diamminedichloride platinum (CDDP) during remission-induction and maintenance chemotherapy of testicular carcinoma

We studied renal function in nine patients with disseminated testicular carcinoma before and after remission-induction and maintenance therapy with a drug combination containing cis-platinum. The median glomerular filtration rate (GFR) decreased during remission-induction therapy from 146 to 118 ml/min. No effect of cumulative toxicity on the median GFR was found during maintenance therapy, nor did the median GFR improve. The median effective renal plasma flow (ERPF) decreased during the total period from 705 to 514 ml/min. No significant changes in median filtration fraction (FF) and serum creatinine were observed. It is suggested that intrarenal hemodynamic effects are important in the nephrotoxicity of cis-diamminedichloride platinum (CDDP).

Renal hemodynamics and oxygen consumption during postischemic acute renal failure in the rat

Acute renal failure in the rat was induced by occluding the left renal artery for 1 hour. The kidneys were examined 1, 3, 10, and 40 days after temporary ischemia. Inulin clearance was essentially zero in oligoanuric kidneys on days 1 and 3, and regained 14% and 63% of the control value on days 10 and 40, respectively. Mean cortical blood flow remained almost constant at 75% of control up to day 10 and normalized subsequently on day 40. Renal oxygen consumption during anuria on days 1 and 3 was 53% and 46% of the control value and increased thereafter concurrently with the restoration of renal function. With a single linear correlation being assumed to exist between sodium reabsorption and oxygen consumption for all kidneys, the sodium reabsorption and oxygen consumption for all kidneys, the sodium transport estimated from oxygen consumption on day 1 was about 40% of control value. The difference between the sodium transport calculated from oxygen consumption and that from inulin clearance decreased with time in the recovery phase. The results indicate only a partial reduction of GFR due to the reduced blood flow in this model. The data are consistent with the hypothesis that tubular leakage and tubular obstruction play an important role in the loss of renal function during the manifestation of acute renal failure.

Renal blood flow distribution during E. coli endotoxin shock in dog

The effect of endotoxin on renal blood flow distribution was studied in anesthetized dogs. Renal blood flow was measured as hydrogen clearance by platinum electrodes placed in outer and in inner halves of cortex and by electromagnetic flowmeter. Intravenous injection of E. coli endotoxin, 3-5 mg/kg b. wt., promptly reduced arterial blood pressure (AP) and renal blood flow. After a transient increase for 45 min AP and renal blood flow declined to about 50% of the control 2 1/2-3 h after injection. The reduction in outer cortical blood flow (OCF) was not significantly different from the reduction in inner cortical blood flow (ICF). The hematocrit (Hct) increased from 40.1 +/- 3.8% to 54.6 +/- 8%, but mean renal vascular resistance did not change. Total plasma protein concentration was not significantly elevated. A marked local flow variability was observed in some periods during the phase of shock with declining AP and total renal blood flow at high Hct. Thus renal blood flow showed phasic changes, but the OCF/ICF ratio was not changed during endotoxin shock. Local blood flow instability was observed periodically at high Hct.

[Toxic nephropathies (author's transl)]

Direct tubular damage, hypersensitivity reaction, metabolically mediated kidney disturbances, and chronic nephropathies are important sequelae of several drugs or their metabolites. In this review the drug-induced kidney disease is discussed from a clinical, histological, and pathogenetic point of view. The knowledge of possible nephrotoxic reactions and their underlying toxins are essential for prevention of this kidney disease.

Tobramycin nephrotoxicity. A prospective clinical study

The nephrotoxicity of tobramycin given at a dose of 4·5 mg/kg/day for a period of 12 days to a group of 90 patients with a mean age of 62·9 years was studied. Toxicity was determined on the basis of 3 main criteria (oliguria <400 ml/24 hr, serum creatinine 0·4 mg increase over a minimum basal level of 1·2 mg/100 ml, BUN 5 mg increase over a minimum of 25 mg/100 ml); and 3 minor criteria (proteinuria, microhaematuria and cylindruria). These parameters were determined before treatment at 7, 10, 14, 17, 21, and 30 days afterwards. The age and coexistence of factors such as hypertension, diabetes, anaemia, cardiac insufficiency, shock and dehydration were considered. Nephrotoxicity level ranges from 3·3 to 38·8% depending on the criterion used, and is related to hypertension (P<0·001), age (P<0·005) and association with ampicillin (P<0·005). Nephrotoxicity was reversible spontaneously in 96·7% of the cases and no differences have been observed between patients with moderate renal insufficiency and those with normal renal function on the initiation of treatment.

Synergism of dopamine plus furosemide in preventing acute renal failure in the dog

The protective effects of a combination of dopamine and furosemide were studied in dogs during the initial phase of acute renal failure (ARF) induced by intravenous uranyl nitrate (10 mg/kg). Fifteen minutes after injection of the nephrotoxin, and infusion of dopamine (3 micrograms/kg/min), furosemide (1 mg/kg/bolus followed by 1 mg/kg/hr), or both drugs simultaneously were given for 6 hours. Exogenous creatinine clearance was measured for 6 hours, and the intrarenal blood flow was measured with radioactive microspheres before and 3 hours after the induction of ARF. Treatment with both dopamine and furosemide produced renal vasodilatation, high urine flow rate, and attenuation of the fall in GRF seen in untreated animals. In contrast, single use of dopamine or furosemide was totally ineffective in producing renal vasodilation, a diuresis, or the maintenance of the GFR. These data indicate that dopamine plus furosemide have a synergistic effect in preventing the early pathophysiologic changes associated with ARF in this animal model. Maintenance of a high GFR correlated best with the enhancement of solute excretion and urine flow rate. Potential protective effects of dopamine plus furosemide in other models of ARF deserve careful investigation.

Mercury nephrotoxicity from peritoneal lavage

Two cases of acute renal failure following intraperitoneal administration of mercury are described.

The patterns of peripheral plasma renin concentration in the early post-renal-transplant period

Serial determinations of peripheral plasma renin concentration (PRC) were performed in 11 kidney transplant recipients during the early post-transplant period. In 5 recipients with late onset of graft function, PRC values were increased during the anuric phase and, subsequently, PRC values declined in every during restoration of graft function. In 4 recipients with an acute renal allograft reaction, PRC values were increased at the onset of the allograft reaction in 3 with hypertension whereas PRC values were normal in one normotensive recipient. Subsequently, PRC normalized in the hypertensives coincident with increasing body weights. In 2 recipients with an uncomplicated course and with a normal graft function immediately after transplantation and throughout the study period, PRC values were constantly normal. The results indicate that acute anuria in the early phase after kidney transplantation is associated with an increased release of renin. The results also suggest that an increased activity of the renin-angiotensin system may be counterbalanced by sodium and fluid retention in hypertension following an acute renal allograft reaction.

Experimental acute renal failure in primates. Clinical and histopathologic evaluation in light and electron microscopy

Acute renal failure or its equivalent, acute tubular necrosis, was induced in rhesus monkeys by a combination of dehydration, hemorrhagic hypovolemia, and packed cell transfusion. Clinicopathologic changes were studied at different time intervals. Increasing edematous swelling and disintegration of the epithelial cells in the convoluted tubules, thick loops of Henle, and collecting tubules during the first four hours were conspicuous. As a result, intratubular cellular detritus, red blood cells, and various types of casts were increased progressively between one and four hours, and decreased thereafter. As the time progressed, edema was subsiding but the absorption granules and fat droplets were increased in size and number from one to twenty-four hours. These findings would indicate widespread cellular degeneration and necrosis. Consequently, tubular integrity was impaired leading to necrosis, denuded tubular basement membranes, and occasional tubulorrhexis. Concurrently, some dilated peritubular or interstitial capillaries were ruptured releasing red blood cells and cellular debris, which eventually were picked up by the damaged tubules. Although the regeneration of the renal parenchyma was in progress after sixteen hours, groups of subcapsular tubules were dilated showing flattened epithelial cells. The glomerular capillaries were either dilated or engorged, empty or collapsed during the experiment. Bowman's spaces contained red blood cells and varying amounts of cellular debris. Although the clinicopathologic changes reported here may be attributed to one or more of the following factors, hypoxia, toxic effects and dehydration, most of the changes were apparently due to hypoxia.

Spasm of cortical arteries as a complication to selective nephroangiography

Six cases of spasm of the cortical arteries with redistribution of blood flow to the corticomedullary glomeruli as a complication to nephroangiography are reported. The etiology and the underlying anatomy and physiology are reviewed. Advice is given to avoid the complication.

Pathogenic mechanisms in early norepinephrine-induced acute renal failure: functional and histological correlates of protection

The present study investigated the protective effect of acute volume expansion (25%) with isotonic saline, isotonic mannitol, and hypertonic mannitol in a model of unilateral norepinephrine-induced acute renal failure (ARF). Three hours following a 40-min intrarenal infusion of norepinephrine (NE) (0.75 microgram/kg/min), inulin clearance had fallen from a control value of 54.1 +/- 6.5 to 1.3 +/- 1.3 ml/min in untreated dogs and fell similarly (P = NS) to 3.3 +/- 1.5 ml/min in animals preexpanded with 0.9% saline (0.75 ml/kg/min). In contrast, as compared to the untreated animals, inulin clearance 3 hr post NE infusion was significantly greater in dogs preexpanded with 5% mannitol (9.2 +/- 2.5 ml/min, P less than 0.01), or 20% mannitol (16.6 +/- 3.9 ml/min, P less than 0.01). The protective effects of 5% and 20% mannitol were not statistically different from each other. Recovery of renal excretory function in all groups, expressed as 3-hr post NE inulin clearance, correlated with the magnitude of pre NE solute excretion rate (r = 0.612, P less than 0.001) and osmolar clearance rate (r=0.593, P less than 0.001), but not with pre insult inulin clearance (r = 0.233, P = NS) or renal blood flow (r = 0.249, P = NS). In the presence of a profound fall in inulin clearance, proximal tubular (PT) pressures in untreated dogs 3 hr post NE infusion achieved a value equal to control (26 +/- 11 vs. 25 +/- 2 mm Hg). In contrast, pretreatment with isotonic mannitol produced a rise in PT pressure both before (45 +/- 4 mm Hg, P less than 0.05) and 3 hr post NE infusion (38 +/- 5 mm Hg, P less than 0.05). In all groups of animals, at both 3 and 24 hr post NE, tubular injury was observed but glomerular architecture remained normal by light and electron microscopy. Conclusion. the protective effect of mannitol in this reversible model of ARF did not correlate with inulin clearance, renal blood flow, extracellular fluid (ECF) volume, ECF hypertonicity, or renal histologic changes but did correlate with the solute excretion rate. The increased PT pressures with mannitol both before and after the NE insult could contribute to the protective effect of attenuating any relative intratubular obstruction.

Hypovolemic models of acute tubular necrosis in the rat kidney

Studies were undertaken to determine whether a hypotensive episode under variable conditions is capable of inducing experimental acute renal failure in rats. Animals were subjected to hypovolemic shock by withdrawing volumes of blood necessary to maintain a systolic pressure of 30-40 mm Hg for 105-110 min. The blood was then reinfused and the animal was allowed to recover for 48 h prior to sacrifice. In an attempt to increase the injury, a second group of animals was salt-depleted prior to injury, a third group was volume-depleted by being deprived of H2O for 72 h prior of injury, a fourth group received 7.5 mg/kg indomethacin 30 min prior to injury, and a fifth group had 30% of the blood which was removed to produce shock hemolyzed and returned following the injury. In all groups examined, light microscopy revealed a moderate to severe acute tubular necrosis localized mainly in the outer stripe of the outer zone as defined by Peter (1909). Tubular damage was confined to the medullary pars recta of the proximal tubule and only in the most severe cases did injury involve the cortical pars recta and pars convoluta. Casts were present in the distal tubules and collecting ducts. Despite these significant histologic alterations, BUN values from all experimental groups remained within control levels. These studies clearly show that extensive necrosis of the medullary pars recta can be dissociated from the development of acute renal failure.

Plasma renin and angiotensin II in acute renal failure

The role of raised plasma renin and angiotensin-II concentrations in the development of acute renal failure in man was examined in patients in shock from various causes and in patients in whom hypotension was used to promote haemostasis. Ten of the thirteen patients in shock had raised angiotensin-II concentrations in peripheral blood and acute renal failure manifested by oliguria, increasing serum-creatinine, a urine osmolality of less than 400 mos-mol/kg and a urine/plasma osmolality ratio of less than 1-5. Although patients who were hypotensive for periods of 1 h 45 min to 4 h to promote haemostasis during surgery had similarly raised plasma-renin activity and angiotensin-II concentrations in peripheral venous blood, they did not have acute renal failure. It is concluded that high plasma-angiotensin-II concentrations do not explain the pathogenesis of acute renal failure in patients in shock.

Acute renal failure in the neonate

With advances in diagnostic technology, the diagnosis of renal failure from prerenal and renal causes is being made more frequently. With better clinical understanding of etiologic causes, early prevention and diagnostic and therapeutic measures can be taken. Proper and controlled use of fluids, calories, and drugs is essential. Because of its relative ease, peritoneal dialysis is usually preferred over hemodialysis when renal failure cannot be handled more conservatively. Although the incidence of renal failure has apparently increased with the advent of neonatal intensive care, survival rates are increasing and the potential for prevention is better.