Prevention of acute renal failure in the critically ill

The management and diagnosis of rhabdomyolysis-induced acute kidney injury: a case study

Rhabdomyolysis is characterised by a rapid dissolution of damaged or injured skeletal muscle that can be the result of a multitude of mechanisms. It can range in severity from mild to severe, leading to multi-organ failure and death. Rhabdomyolysis causes muscular cellular breakdown, which can cause fatal electrolyte imbalances and metabolic acidosis, as myoglobin, creatine phosphokinase, lactate dehydrogenase and other electrolytes move into the circulation; acute kidney injury can follow as a severe complication. This article reflects on the case of a person who was diagnosed with rhabdomyolysis and acute kidney injury after a fall at home. Understanding the underpinning mechanism of rhabdomyolysis and the associated severity of symptoms may improve early diagnosis and treatment initiation.

Mitigation of Acute Aluminum Toxicity by Sodium Selenite and N-Acetylcysteine in Adult Male Rats

The objective of this study is to investigate the toxic effects of aluminum and the potential alleviation of selenite and N-acetylcysteine (NAC) on this toxicity. Acute aluminum toxicity was induced by intraperitoneal (i.p.) injection of AlCl₃ (30 mg Al³⁺/kg) for four consecutive days. Al³⁺ damaged the synthetic capability and regeneration power of liver cells and induced inflammation. It also damaged the kidney and disturbed the lipid profile enhancing the total cholesterol level and LDL-cholesterol level increasing the risks of atherosclerosis. Al³⁺ reduced the cellular antioxidant milieu typified by the decrease in reduced glutathione, vitamin E, and four antioxidant enzymes and induced lipid peroxidation (LPO). Selenite at 1 mg Se/kg and NAC at 150 mg/kg injected either simultaneously with or after Al³⁺ mitigated most of these damaging effects probably by the virtue of scavenging the free radicals, binding aluminum and stimulating its excretion and reducing its bioavailability, bolstering the endogenous antioxidant defense systems, stabilizing the cell membrane, and preventing LPO. The beneficial effects of selenite and NAC against aluminum toxicity were also confirmed by the light and electron histopathology study. There were no significant differences between the two regimens used (protection and therapeutic) in the current study probably due to the short time of exposure, and the abrogation of Al³⁺ toxicity offered by selenite was better than that provided by NAC on the histopathology level.

The role of perioperative sodium bicarbonate infusion affecting renal function after cardiothoracic surgery

Cardiac surgery associated acute kidney injury (CSA-AKI) is associated with poor outcomes including increased mortality, length of hospital stay (LOS) and cost. The incidence of acute kidney injury (AKI) is reported to be between 3 and 30% depending on the definition of AKI. We designed a multicenter randomized controlled trial to test our hypothesis that a perioperative infusion of sodium bicarbonate (SB) during cardiac surgery will attenuate the post-operative rise in creatinine indicating renal injury when compared to a perioperative infusion with normal saline. An interim analysis was performed after data was available on the first 120 participants. A similar number of patients in the two treatment groups developed AKI, defined as an increase in serum creatinine the first 48 h after surgery of 0.3 mg/dl or more. Specifically 14 patients (24%) who received sodium chloride (SC) and 17 patients (27%) who received SB were observed to develop AKI post-surgery, resulting in a relative risk of AKI of 1.1 (95% CI: 0.6–2.1, chi-square p-value = 0.68) for patients receiving SB compared to those who received SC. The data safety monitoring board for the trial recommended closing the study early as there was only a 12% probability that the null hypothesis would be rejected. We therefore concluded that a perioperative infusion of SB failed to attenuate the risk of CSA-AKI.

Effects of levosimendan on glomerular filtration rate, renal blood flow, and renal oxygenation after cardiac surgery with cardiopulmonary bypass: a randomized placebo-controlled study

OBJECTIVES

Acute kidney injury develops in a large proportion of patients after cardiac surgery because of the low cardiac output syndrome. The inodilator levosimendan increases cardiac output after cardiac surgery with cardiopulmonary bypass, but a detailed analysis of its effects on renal perfusion, glomerular filtration, and renal oxygenation in this group of patients is lacking. We therefore evaluated the effects of levosimendan on renal blood flow, glomerular filtration rate, renal oxygen consumption, and renal oxygen demand/supply relationship, i.e., renal oxygen extraction, early after cardiac surgery with cardiopulmonary bypass.

DESIGN

Prospective, placebo-controlled, and randomized trial.

SETTING

Cardiothoracic ICU of a tertiary center.

PATIENTS

Postcardiac surgery patients (n=30).

INTERVENTIONS

The patients were randomized to receive levosimendan, 0.1 µg/kg/min after a loading dose of 12 µg/kg (n=15), or placebo (n=15).

MEASUREMENTS AND MAIN RESULTS

The experimental procedure started 4-6 hours after surgery in the ICU during propofol sedation and mechanical ventilation. Systemic hemodynamic were evaluated by a pulmonary artery thermodilution catheter. Renal blood flow and glomerular filtration rate were measured by the renal vein retrograde thermodilution technique and by renal extraction of Cr-EDTA, respectively. Central venous pressure was kept constant by colloid/crystalloid infusion. Compared to placebo, levosimendan increased cardiac index (22%), stroke volume index (15%), and heart rate (7%) and decreased systemic vascular resistance index (21%), whereas mean arterial pressure was not affected. Levosimendan induced significant increases in renal blood flow (12%, p<0.05) and glomerular filtration rate (21%, p<0.05), decreased renal vascular resistance (18%, p<0.05) but caused no significant changes in filtration fraction, renal oxygen consumption, or renal oxygen extraction, compared to placebo.

CONCLUSIONS

After cardiac surgery with cardiopulmonary bypass, levosimendan induces a vasodilation, preferentially of preglomerular resistance vessels, increasing both renal blood flow and glomerular filtration rate without jeopardizing renal oxygenation. Due to its pharmacodynamic profile, levosimendan might be an interesting alternative for treatment of postoperative heart failure complicated by acute kidney injury in postcardiac surgery patients.

Atrial natriuretic peptide attenuates kidney-lung crosstalk in kidney injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury after cardiovascular surgery, which in turn deteriorates oxygenation. Atrial natriuretic peptide (ANP) has natriuretic, diuretic, and anti-inflammatory effects. To elucidate whether renal IRI induces inflammation in the kidney and lung and ANP attenuates kidney-lung crosstalk.

MATERIALS AND METHODS

The rats were anesthetized, tracheostomized, mechanically ventilated, and randomized to four groups: saline + IRI (n = 12), ANP + IRI (n = 12), ANP + sham (n = 6), and saline + sham (n = 6). Saline (6 mL/kg/h) or ANP (0.2 μg/kg/min) at the rate of 6 mL/kg/h was started 5 min before clamping, respectively. Renal IRI was induced by clamping the left renal pedicle for 30 min. The hemodynamics, arterial blood gases, and plasma concentrations of creatinine and lactate were measured at baseline and 1, 2, and 3 h after declamping. Lung wet-to-dry ratio was measured. The mRNA expression of tumor necrosis factor (TNF)-α, interleukin (IL) 1β, and IL-6 and histologic localization of TNF-α in the kidney and lung were measured.

RESULTS

Renal IRI induced metabolic acidosis, pulmonary edema, increases in plasma concentrations of creatinine and lactate, and augmentation of the cytokine mRNA expression and histologic localization of TNF-α in the kidney and Renal IRI induced lung. ANP prevented IRI-induced metabolic acidosis, pulmonary edema, increases in creatinine, lactate, and the cytokine mRNA expression, attenuated histologic localization of TNF-α in the kidney and lung, and increased oxygenation.

CONCLUSIONS

ANP has renoprotective and anti-inflammatory effects on the kidney and lung in a rat model of renal IRI, suggesting that ANP attenuates kidney-lung crosstalk.

Effects of carperitide on contrast-induced acute kidney injury with a minimum volume of contrast in chronic kidney disease patients

BACKGROUND/AIMS

Although contrast-induced acute kidney injury (CIAKI) is a major complication associated with angiography, the prophylaxis is not well established. Use of a low dose of carperitide for preventing CIAKI remains controversial. We examined the protective effect of carperitide on CIAKI after coronary angiography with a small contrast volume in chronic kidney disease (CKD) patients with coronary artery disease.

METHODS

We randomly assigned 112 consecutive patients to a carperitide or a control group. The contrast volume was kept under 150 ml. The primary endpoint was the incidence of CIAKI defined by a serum creatinine of ≥25% or a serum creatinine of ≥0.5 mg/dl from baseline within 48 h. The secondary endpoint was a change in renal function at 1 week after the procedure.

RESULTS

The baseline characteristics and contrast volumes (carperitide group: 67.4 ± 38.2 ml vs. control group: 64.8 ± 20.5 ml, p = 0.661) were comparable in the two groups. The incidence of CIAKI was similar in the two groups (carperitide group: 8.5% vs. control group: 5.7%, p = 0.564). A multivariate analysis revealed that a hypotension ≥20 mm Hg was a significant predictor of developing CIAKI in the carperitide group (p = 0.015). The incidence of CIAKI in the carperitide group without hypotension was rare, but not significantly different (carperitide group: 2.4% vs. control group: 5.7%, p = 0.432).

CONCLUSIONS

This study indicated that the use of a small contrast volume suppressed the incidence of CIAKI and that carperitide had no prophylactic effect against CIAKI. Our results also revealed the impact of hypotension on the development of CIAKI in the carperitide group.

Mannitol increases renal blood flow and maintains filtration fraction and oxygenation in postoperative acute kidney injury: a prospective interventional study

Introduction

Acute kidney injury (AKI), which is a major complication after cardiovascular surgery, is associated with significant morbidity and mortality. Diuretic agents are frequently used to improve urine output and to facilitate fluid management in these patients. Mannitol, an osmotic diuretic, is used in the perioperative setting in the belief that it exerts reno-protective properties. In a recent study on uncomplicated postcardiac-surgery patients with normal renal function, mannitol increased glomerular filtration rate (GFR), possibly by a deswelling effect on tubular cells. Furthermore, experimental studies have previously shown that renal ischemia causes an endothelial cell injury and dysfunction followed by endothelial cell edema. We studied the effects of mannitol on renal blood flow (RBF), glomerular filtration rate (GFR), renal oxygen consumption (RVO₂), and extraction (RO₂Ex) in early, ischemic AKI after cardiac surgery.

Methods

Eleven patients with AKI were studied during propofol sedation and mechanical ventilation 2 to 6 days after complicated cardiac surgery. All patients had severe heart failure treated with one (100%) or two (73%) inotropic agents and intraaortic balloon pump (36%). Systemic hemodynamics were measured with a pulmonary artery catheter. RBF and renal filtration fraction (FF) were measured by the renal vein thermo-dilution technique and by renal extraction of chromium-51-ethylenediaminetetraacetic acid (⁵¹Cr-EDTA), respectively. GFR was calculated as the product of FF and renal plasma flow RBF × (1-hematocrit). RVO₂ and RO₂Ex were calculated from arterial and renal vein blood samples according to standard formulae. After control measurements, a bolus dose of mannitol, 225 mg/kg, was given, followed by an infusion at a rate of 75 mg/kg/h for two 30-minute periods.

Results

Mannitol did not affect cardiac index or cardiac filling pressures. Mannitol increased urine flow by 61% (P < 0.001). This was accompanied by a 12% increase in RBF (P < 0.05) and a 13% decrease in renal vascular resistance (P < 0.05). Mannitol increased the RBF/cardiac output (CO) relation (P = 0.040). Mannitol caused no significant changes in RO₂Ext or renal FF.

Conclusions

Mannitol treatment of postoperative AKI induces a renal vasodilation and redistributes systemic blood flow to the kidneys. Mannitol does not affect filtration fraction or renal oxygenation, suggestive of balanced increases in perfusion/filtration and oxygen demand/supply.

Multicenter trial of carperitide in patients with renal dysfunction undergoing cardiovascular surgery

PURPOSE

The aim of this study was to evaluate the efficacy of carperitide in maintaining renal function during intraoperative and postoperative management of patients with renal dysfunction undergoing elective cardiovascular surgery.

METHODS

The subjects were 88 patients with a preoperative serum creatinine level ≥1.2 mg/dl who underwent elective cardiovascular surgery using cardiopulmonary bypass. They were prospectively divided into a group that received carperitide from the start of surgery (carperitide group, n = 44) and a group that was not given carperitide (control group, n = 44). Carperitide infusion was initiated at the beginning of surgery and was continued for ≥5 days, with the central dose being 0.02 g/kg/min. The primary endpoint was the serum creatinine level on postoperative day (POD) 3.

RESULTS

The serum creatinine levels on PODs 3, 4, and 7 were significantly lower, and creatinine clearance on PODs 2 and 3 was significantly higher in the carperitide group than in the controls. One patient in the control group and no patient in the carperitide group required continuous hemodiafiltration, but the difference was not statistically significant.

CONCLUSION

Continuous low-dose infusion of carperitide from the start of cardiovascular surgery maintained renal function in patients with preoperative renal dysfunction.

Neutrophilic Cells in Sputum of Allergic Asthmatic Children

Airway inflammation is regarded as a central feature of asthma and is mostly sustained by eosinophilic infiltrate. Recent studies have shown that a co-activation of eosinophil- and neutrophil-dependent inflammatory mechanisms might explain why some asthmatics do not respond to conventional asthma therapy. The aim of our study is to determine whether neutrophilic inflammation was involved in 55 allergic children with mild-moderate persistent asthma and the relationship with the response to steroid treatment. Before the sputum analysis, all children underwent spirometry with the reversibility test, and were divided into two groups on the basis of the response (such as >12% of baseline FEV1): group 1 positive and group 2 negative. Eosinophil cationic protein concentrations were measured by radioimmunoassay and neutrophyl myeloperoxidase (MPO) concentrations were measured by an MPO-EIA. Ten healthy children of comparable ages served as control group. Total IgE, FEV1 and FEV/FVC values were similar in both groups. The sputum macrophage count was higher in controls than in allergic asthmatics, but there was no difference between groups 1 and 2 (59.6% vs 18.3% and 17%; p≤ 0.005). Sputum neutrophils were significantly higher in group 2 both vs controls (62% vs 34%; p≤ 0.005) and vs group 1 (62% vs 37%; p≤ 0.005). Our data suggest that neutrophils are involved in airway allergic inflammation in mild-moderate persistent childhood asthma and a high neutrophil count in sputum may be related to a lower responsiveness to inhaled corticosteroids.

Acute renal failure is NOT an "acute renal success"--a clinical study on the renal oxygen supply/demand relationship in acute kidney injury

OBJECTIVES

Acute kidney injury occurs frequently after cardiac or major vascular surgery and is believed to be predominantly a consequence of impaired renal oxygenation. However, in patients with acute kidney injury, data on renal oxygen consumption (RVO2), renal blood flow, glomerular filtration, and renal oxygenation, i.e., the renal oxygen supply/demand relationship, are lacking and current views on renal oxygenation in the clinical situation of acute kidney injury are presumptive and largely based on experimental studies.

DESIGN

Prospective, two-group comparative study.

SETTING

Cardiothoracic intensive care unit of a tertiary center.

PATIENTS

Postcardiac surgery patients with (n = 12) and without (n = 37) acute kidney injury were compared with respect to renal blood flow, glomerular filtration, RVO2, and renal oxygenation.

INTERVENTIONS

None

MEASUREMENTS AND MAIN RESULTS

Data on systemic hemodynamics (pulmonary artery catheter) and renal variables were obtained during two 30-min periods. Renal blood flow was measured using two independent techniques: the renal vein thermodilution technique and the infusion clearance of paraaminohippuric acid, corrected for renal extraction of paraaminohippuric acid. The filtration fraction was measured by the renal extraction of Cr-EDTA and the renal sodium resorption was measured as the difference between filtered and excreted sodium. Renal oxygenation was estimated from the renal oxygen extraction. Cardiac index and mean arterial pressure did not differ between the two groups. In the acute kidney injury group, glomerular filtration (-57%), renal blood flow (-40%), filtration fraction (-26%), and sodium resorption (-59%) were lower, renal vascular resistance (52%) and renal oxygen extraction (68%) were higher, whereas there was no difference in renal oxygen consumption between groups. Renal oxygen consumption for one unit of reabsorbed sodium was 2.4 times higher in acute kidney injury.

CONCLUSIONS

Renal oxygenation is severely impaired in acute kidney injury after cardiac surgery, despite the decrease in glomerular filtration and tubular workload. This was caused by a combination of renal vasoconstriction and tubular sodium resorption at a high oxygen demand.

Neutrophil gelatinase associated lipocalin as a biomarker for acute kidney injury in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass

BACKGROUND

Acute kidney injury (AKI) is a significant cause of morbidity and mortality following cardiac surgery throughout the world. The paucity of early biomarkers has hampered early therapeutic intervention. Our aim was to evaluate plasma neutrophil gelatinase associated lipocalin (NGAL) levels as a predictor of renal injury in patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) along with markers of oxidative stress.

METHODS

About 30 patients undergoing CABG with CPB were prospectively studied. Blood was collected before bypass, at 4, 12, and 24 hr after CPB initiation, for the analysis of NGAL and oxidative stress markers.

RESULTS

Eight of 30 patients (26.6%) developed AKI, while 22 (73.4%) did not, as measured by serum creatinine, after 48-72 hr of surgery. However, plasma NGAL levels at 4 hr were high in patients who developed AKI compared with those who did not (352.97 +/- 49.32 vs. 199.83 +/- 23.28 ng/mL, p = 0.000). There was a significant difference in aortic cross-clamp time (p = 0.000), duration of CPB (p = 0.000), and ventilation duration (p < 0.05) between the two groups. The level of malondialdehyde (MDA), a marker of oxidative stress, was higher only at 4 hr in the AKI group. No significant differences were observed in the level of antioxidants between the two groups. A significant correlation was found between plasma NGAL at 4 hr and the change in serum creatinine (r = 0.863, p = 0.006) as well as ventilation duration (r = 0.830, p = 0.011). The sensitivity and specificity of plasma NGAL at 4 hr after CPB was optimal at the 229 ng/mL cut-off with an area under the curve of 0.98 for prediction of AKI.

CONCLUSION

Measurement of plasma NGAL in patients in the first few hours after CPB is predictive of AKI. Oxidative stress as measured by the level of MDA and antioxidants has no substantial role in the progression of AKI during CABG with CPB.

Dopamine increases renal oxygenation: a clinical study in post-cardiac surgery patients

BACKGROUND

Imbalance of the renal medullary oxygen supply/demand relationship can cause ischaemic acute renal failure (ARF). The use of dopamine for prevention/treatment of ischaemic ARF has been questioned. It has been suggested that dopamine may increase renal oxygen consumption (RVO(2)) due to increased solute delivery to tubular cells, which may jeopardize renal oxygenation. Information on the effects of dopamine on renal perfusion, filtration and oxygenation in man is, however, lacking. We evaluated the effects of dopamine on renal blood flow (RBF), glomerular filtration rate (GFR), RVO(2) and renal O(2) demand/supply relationship, i.e. renal oxygen extraction (RO(2)Ex).

METHODS

Twelve uncomplicated, mechanically ventilated and sedated post-cardiac surgery patients with pre-operatively normal renal function were studied. Dopamine was sequentially infused at 2 and 4 ug/kg/min. Systemic haemodynamics were evaluated by a pulmonary artery catheter. Absolute RBF was measured using two independent techniques: by the renal vein thermodilution technique and by infusion clearance of paraaminohippuric acid (PAH), with a correction for renal extraction of PAH. The filtration fraction (FF) was measured by the renal extraction of (51)Cr-EDTA.

RESULTS

Neither GFR, tubular sodium reabsorption nor RVO(2) was affected by dopamine, which increased RBF (45-55%) with both methods, decreased renal vascular resistance (30-35%), FF (21-26%) and RO(2)Ex (28-34%). The RBF/CI ratio increased with dopamine. Dopamine decreased renal PAH extraction, suggestive of a flow distribution to the medulla.

CONCLUSIONS

In post-cardiac surgery patients, dopamine increases the renal oxygenation by a pronounced renal pre-and post-glomerular vasodilation with no increases in GFR, tubular sodium reabsorption or renal oxygen consumption.

Effects of mannitol alone and mannitol plus furosemide on renal oxygen consumption, blood flow and glomerular filtration after cardiac surgery

OBJECTIVE

Imbalance of the renal medullary oxygen supply/demand relationship can cause hypoxic medullary damage and ischaemic acute renal failure (ARF). The use of mannitol for prophylaxis/treatment of clinical ischaemic ARF is controversial and the effect of mannitol on renal oxygenation in man has not yet been investigated. We evaluated the effects of mannitol on renal oxygen consumption (RVO(2))(,) renal blood flow (RBF) and glomerular filtration rate (GFR) in postoperative patients.

DESIGN

Prospective interventional study.

SETTING

University hospital cardiothoracic ICU.

PATIENTS

Ten uncomplicated mechanically ventilated and sedated postcardiac surgery patients with preoperatively normal renal function.

INTERVENTIONS

Mannitol infusion (225 mg/kg + 75 mg/kg/h) and combined mannitol and furosemide infusion (0.25 mg/kg + 0.25 mg/kg/h).

MEASUREMENTS AND RESULTS

Systemic haemodynamics were evaluated by a pulmonary artery catheter. RBF and GFR were measured by the renal vein thermodilution technique and by renal extraction of (51)Cr-EDTA, respectively. Mannitol increased urine flow (60%), GFR (20%) and filtration fraction (FF) (20%) with no change in RBF. This was accompanied by an increase in renal sodium reabsorption (18%), RVO(2) (19%) and renal oxygen extraction (21%). When combined with mannitol, furosemide normalised sodium reabsorption, RVO(2), renal oxygen extraction with no change in RBF, while GFR and FF were still elevated compared to control.

CONCLUSIONS

In patients with normal renal function, mannitol increases GFR, which increases tubular sodium load, sodium reabsorption and RVO(2) after cardiac surgery. The lack of effect on RBF, indicates that mannitol impairs the renal oxygen supply/demand relationship. Furosemide normalised renal oxygenation when combined with mannitol.

Effects of human atrial natriuretic peptide on renal function in patients undergoing abdominal aortic aneurysm repair

OBJECTIVE

Ischemia-reperfusion injury is an important cause of renal dysfunction after abdominal aortic aneurysm repair. Human atrial natriuretic peptide (hANP) is a potent endogenous natriuretic, diuretic, and vasorelaxant peptide. The objective of the present study was to evaluate the effects of hANP on renal function in patients undergoing abdominal aortic aneurysm repair.

DESIGN

A prospective, randomized, placebo-controlled study

SETTING

Intensive care unit of a university hospital.

PATIENTS

Forty patients undergoing elective abdominal aortic aneurysm repair.

INTERVENTIONS

The patients were randomized to receive a continuous infusion of either hANP (0.01-0.05 microg/kg/min) (n = 20) or placebo (n = 20) immediately before aortic cross-clamping. The infusion of hANP or placebo continued for 48 hrs.

MEASUREMENTS AND MAIN RESULTS

Blood and urine samples were taken before surgery, at admission to the intensive care unit, and on days 1, 2, and 3 postoperatively, for measurement of serum concentrations of sodium, creatinine, and blood urea nitrogen and plasma concentrations of ANP and brain natriuretic peptide (BNP). Urine volume and urinary concentrations of N-acetyl-beta-D-glucosaminidase (NAG), sodium, and creatinine were also measured. The mean plasma concentration of ANP was significantly higher in the hANP group than in the placebo group. The mean plasma BNP concentration was significantly lower in the hANP group than in the placebo group. The mean serum concentrations of creatinine and blood urea nitrogen were significantly (p < .05) lower in the hANP group than in the placebo group. The mean urine volume and mean creatinine clearance were significantly (p < .05) higher in the hANP group than in the placebo group. The mean urinary NAG/creatinine ratio was significantly (p < .05) lower in the hANP group than in the placebo group.

CONCLUSIONS

The intraoperative and postoperative infusion of low-dose hANP preserved renal function in patients undergoing abdominal aortic aneurysm repair. Further studies are needed to assess the efficacy of prophylactic hANP infusion on perioperative renal outcome.

Cystatin C in critically ill patients treated with continuous venovenous hemofiltration

Assessment of residual renal function in critically ill patients with acute renal failure (ARF) treated with continuous venovenous hemofiltration (CVVH) is difficult. Cystatin C (CysC) is a low-molecular-weight protein (13.3 kDa) removed from the body by glomerular filtration. Its serum concentration has been advocated for assessment of renal function in patients with kidney disease. To investigate whether the removal of CysC by CVVH is likely to influence its serum concentration, concentrations of CysC were measured in 3 consecutive samples in 18 patients with oliguric ARF treated with CVVH (2 L/hr). Samples were taken from the afferent and efferent blood lines and from the ultrafiltrate line. Concentrations of CysC did not change during the time interval studied. The mean serum concentrations of CysC were 2.25+/-0.45 mg/L in the afferent and 2.19+/-0.56 mg/L in the efferent samples (NS); ultrafiltrate concentrations of CysC were 1.01+/-0.45 mg/L. The sieving coefficient of CysC was 0.52+/-0.20; the clearance of CysC was 17.3+/-6.6 mL/min; and the quantity of CysC removed averaged 2.13 mg/hr. During CVVH (2 L/hr), the quantity of CysC removed is less than 30% of its production and no rapid changes in its serum concentration are observed. Therefore, CVVH (2 L/hr) is unlikely to influence serum concentrations of CysC significantly, which suggests that it can be used to monitor residual renal function during CVVH.

Risk factors for death among critically ill patients with acute renal failure

CONTEXT AND OBJECTIVE

Acute renal failure is a common medical problem, with a high mortality rate. The aim of this work was to investigate the risk factors for death among critically ill patients with acute renal failure.

DESIGN AND SETTING

Retrospective cohort at the intensive care unit of Hospital Universitário Walter Cantídio, Fortaleza.

METHODS

Survivors and non-survivors were compared. Univariate and multivariate analyses were performed to establish risk factors for death.

RESULTS

Acute renal failure occurred in 128 patients (33.5%), with mean age of 49 +/- 20 years (79 males; 62%). Death occurred in 80 (62.5%). The risk factors most frequently associated with death were hypotension, sepsis, nephrotoxic drug use, respiratory insufficiency, liver failure, hypovolemia, septic shock, multiple organ dysfunction, need for vasoactive drugs, need for mechanical ventilation, oliguria, hypoalbuminemia, metabolic acidosis and anemia. There were negative correlations between death and: prothrombin time, hematocrit, hemoglobin, systolic blood pressure, diastolic blood pressure, arterial pH, arterial bicarbonate and urine volume. From multivariate analysis, the independent risk factors for death were: need for mechanical ventilation (OR = 3.15; p = 0.03), hypotension (OR = 3.48; p = 0.02), liver failure (OR = 5.37; p = 0.02), low arterial bicarbonate (OR = 0.85; p = 0.005), oliguria (OR = 3.36; p = 0.009), vasopressor use (OR = 4.83; p = 0.004) and sepsis (OR = 6.14; p = 0.003).

CONCLUSIONS

There are significant risk factors for death among patients with acute renal failure in intensive care units, which need to be identified at an early stage for early treatment.

Facts and fallacies concerning the prevention of contrast medium-induced nephropathy

OBJECTIVE

The aim of this article is to extract from recent medical literature and nephrologic practice the facts and fallacies concerning the possible prophylaxis of contrast medium-induced nephropathy.

DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION

A MEDLINE/PubMed search (1985 to January 2006) was conducted, including all relevant articles investigating the pathogenesis and prevention of contrast medium-induced nephropathy from a nephrologic critical point of view.

DATA SYNTHESIS

Considerable efforts have been made to develop pharmacologic therapy for the prevention of contrast medium-induced nephropathy, especially in patients at risk, such as elderly subjects and those with preexisting renal impairment, hypovolemia, or dehydration. There is general consensus that hydration protocols implemented before and after imaging with contrast medium may be effective in preventing contrast medium-induced nephropathy. However, definitive and convincing data related to amounts to be infused, infusion timing, and type of solutions (half-isotonic, isotonic saline solution, or bicarbonate) are lacking. Forced diuresis with furosemide or mannitol and use of dopamine, together with concomitant hydration, have been proved to be ineffective or even more risky in the event of inadequate maintenance of euvolemia. Various direct or indirect vasodilators have been investigated (atrial natriuretic peptide, calcium channel blockers, angiotensin-converting enzyme inhibitors, and endothelin receptor antagonists), yet results have been inconsistent and inconclusive. Recent large meta-analyses concerning the protective role of antioxidant action of N-acetylcysteine have led to the conclusion that the statistical significance of the results is borderline. Preventive hemodialysis has not proved to be useful; on the contrary, it might worsen the clinical conditions by inducing hypotension. Hemofiltration, despite some positive studies, is too complex and cannot be used extensively.

CONCLUSIONS

: It is believed that prevention is actually achieved by correcting hypovolemia, dehydration, or both. Normalization of body fluids is probably the true objective to be achieved by preventive measures in all patients, not only in those at risk. Because limited data have been collected in intensive care units, at present, no firm or specific recommendations can yet be provided for the critically ill.

Management of acute renal failure

Acute renal failure is a common condition, frequently encountered in both community practice and hospital inpatients. While it remains a heterologous condition, following basic principles makes investigation straightforward, and initial management follows a standard pathway in most patients. This article shows this, advises on therapeutic strategies, including those in special situations, and should help the clinician in deciding when to refer to a nephrologist, and when to consider renal replacement therapy.

Small increases in the urinary excretion of glutathione S-transferase A1 and P1 after cardiac surgery are not associated with clinically relevant renal injury

OBJECTIVE

Cardiac surgery is an important risk factor for the development of acute renal failure. Cytosolic enzymes glutathione S-transferase (GST) A1 and P1 are present selectively in proximal and distal tubular cells, respectively. We determined the extent and site of tubular injury and examined if GST excretion may predict a clinically relevant change in renal function.

DESIGN AND SETTING

A prospective, observational study in 84 consecutive patients in the cardiac surgery intensive care unit of the University Medical Centre Nijmegen.

MEASUREMENTS AND RESULTS

Urinary GST enzyme excretion was determined 0-4 h and 20-24 h after cardiac surgery by enzyme-linked immunosorbent assay. Data are expressed as median and 5-95% range. Urinary excretion of GSTA1 was increased: 1.25 microg/mmol [0.31-10.20] creatinine at t =0-4 h ( p <0.0001, compared with controls; 0.25 [0.1-0.8]) and returned to normal values at t =20-24 h. Excretion of GSTP1 was 2.11 microg/mmol [0.52-17.82] creatinine ( p <0.0001) at t =0-4 h and remained significantly elevated: 0.84 [0.30-16.86] at t =20-24 h ( p =0.01) compared with controls (0.5 [0.2-1.1]). The ten patients with the highest urinary excretion of GSTA1 or GSTP1 did not demonstrate a different plasma creatinine level on postoperative day 3, compared with the ten patients with the lowest urinary excretion of GSTA1 or GSTP1.

CONCLUSION

Uncomplicated cardiac surgery results in a statistically significant increase in the urinary excretion of GSTA1 and GSTP1 as compared with healthy controls, indicating proximal and distal tubular damage. However, this small increase in urinary excretion of GSTs is not associated with clinically relevant renal injury.

Bench-to-bedside review: preventive measures for contrast-induced nephropathy in critically ill patients

An increasing number of diagnostic imaging procedures requires the use of intravenous radiographic contrast agents, which has led to a parallel increase in the incidence of contrast-induced nephropathy. Risk factors for development of contrast-induced nephropathy include pre-existing renal dysfunction (especially diabetic nephropathy and multiple myeloma-associated nephropathy), dehydration, congestive heart failure and use of concurrent nephrotoxic medication (including aminoglycosides and amphotericin B). Because contrast-induced nephropathy accounts for a significant increase in hospital-acquired renal failure, several strategies to prevent contrast-induced nephropathy are currently advocated, including use of alternative imaging techniques (for which contrast media are not needed), use of (the lowest possible amount of) iso-osmolar or low-osmolar contrast agents (instead of high-osmolar contrast agents), hyperhydration and forced diuresis. Administration of N-acetylcysteine, theophylline, or fenoldopam, sodium bicarbonate infusion, and periprocedural haemofiltration/haemodialysis have been investigated as preventive measures in recent years. This review addresses the literature on these newer strategies. Since only one (nonrandomized) study has been performed in intensive care unit patients, at present it is difficult to draw firm conclusions about preventive measures for contrast-induced nephropathy in the critically ill. Further studies are needed to determine the true role of these preventive measures in this group of patients who are at risk for contrast-induced nephropathy. Based on the available evidence, we advise administration of N-acetylcysteine, preferentially orally, or theophylline intravenously, next to hydration with bicarbonate solutions.

Differential effects of human atrial natriuretic peptide and furosemide on glomerular filtration rate and renal oxygen consumption in humans

OBJECTIVE

Imbalance in the renal medullary oxygen supply/demand relationship can cause hypoxic medullary damage and ischemic acute renal failure. Human atrial natriuretic peptide (h-ANP) increases glomerular filtration rate in clinical acute renal failure. This would increase renal oxygen consumption due to increased tubular load of sodium. Loop diuretics are commonly used in acute renal failure. Data on the effects of loop diuretics on glomerular filtration rate and renal oxygen consumption in humans are, however, controversial. We evaluated the effects of h-ANP and furosemide on renal oxygen consumption, glomerular filtration rate, and renal hemodynamics in humans.

DESIGN AND SETTING

Prospective two-agent interventional study in a university hospital cardiothoracic ICU.

PATIENTS

Nineteen uncomplicated, mechanically ventilated postcardiac surgery patients with normal renal function.

INTERVENTIONS

h-ANP (25 and 50 ng/kg per minute, n=10) or furosemide (0.5 mg/kg per hour, n=9).

MEASUREMENTS AND RESULTS

Renal plasma flow and glomerular filtration rate were measured using the infusion clearance technique for (51)Cr-labeled EDTA and paraaminohippurate, corrected for by renal extraction of PAH. h-ANP increased glomerular filtration rate, renal filtration fraction, fractional excretion of sodium, and urine flow. This was accompanied by an increase in tubular sodium reabsorption (9%) and renal oxygen consumption (26%). Furosemide infusion caused a 10- and 15-fold increase in urine flow and fractional excretion of sodium, respectively, accompanied by a decrease in tubular sodium reabsorption (-28%), renal oxygen consumption (-23%), glomerular filtration rate and filtration fraction (-12% and -7%, respectively).

CONCLUSIONS

The filtered load of sodium is an important determinant of renal oxygen consumption. h-ANP improves glomerular filtration rate but does not have energy-conserving tubular effects. In contrast, furosemide decreases tubular sodium reabsorption and renal oxygen consumption and thus has the potential to improve the oxygen supply/demand relationship in clinical ischemic acute renal failure.

Bedside estimation of absolute renal blood flow and glomerular filtration rate in the intensive care unit. A validation of two independent methods

OBJECTIVE

To evaluate various treatment strategies in critically ill patients with ischaemic acute renal failure, there is a need for reliable bedside measurements of total renal blood flow (RBF), glomerular filtration rate (GFR) and renal oxygen consumption without the need for urine collection.

DESIGN

The continuous renal vein thermodilution method and the infusion clearance techniques were validated against the gold standard technique, the urinary clearance of paraaminohippurate (PAH) and chromium ethylenediaminetetraacetic acid, respectively.

SETTING

University hospital cardiothoracic ICU.

PATIENTS

Seventeen uncomplicated mechanically ventilated post-cardiac surgical patients.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Renal blood flow, GFR and the renal filtration fraction (FF) were measured for two consecutive 30-min periods by urinary clearance and compared with simultaneous measurements made by the thermodilution and infusion clearance techniques. Urinary clearance for PAH was corrected for by renal extraction of PAH. The within-group error, repeatability coefficient and the coefficient of variation were highest for the thermodilution technique and lowest for the infusion clearance technique with regard to RBF, GFR and FF. The infusion clearance technique had a higher agreement with the urinary clearance method than the thermodilution method. For estimations of RBF and GFR, the between-group errors were 33% and 43% comparing infusion clearance with urinary clearance and 65% and 67% comparing thermodilution with urinary clearance.

CONCLUSIONS

The infusion clearance method had the highest reproducibility and the highest agreement with the urinary clearance reference method. The renal vein thermodilution technique is less reliable in the ICU setting due to poor repeatability and poor agreement with the reference method.

Recombinant human atrial natriuretic peptide in ischemic acute renal failure: A randomized placebo-controlled trial*

OBJECTIVE

Acute renal failure is associated with significant morbidity and mortality rates. Need for dialysis is an independent risk factor for early mortality after complicated cardiac surgery. Human atrial natriuretic peptide (h-ANP) is a potent endogenous natriuretic and diuretic substance. Exogenous administration of h-ANP increases glomerular filtration rate and renal blood flow in clinical acute renal failure. We have studied the effects of h-ANP on renal outcome in ischemic acute renal failure.

DESIGN

A prospective, double-blind, randomized, placebo-controlled study.

SETTING

Cardiothoracic intensive care units of two tertiary care centers.

PATIENTS

Sixty-one patients with normal preoperative renal function suffering from postcardiac surgical heart failure requiring significant inotropic and vasoactive support.

INTERVENTIONS

The patients were randomized to receive a continuous infusion of either recombinant h-ANP (50 ng.kg(-1).min(-1)) or placebo when serum creatinine increased by >50% from baseline. The treatment with h-ANP/placebo continued until serum creatinine decreased below the trigger value for inclusion or the patients fulfilled predefined criteria for dialysis.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was dialysis on or before day 21 after the start of treatment. Secondary renal outcome variables were dialysis-free survival at day 21 and creatinine clearance. Twenty-nine patients were assigned h-ANP and 30 placebo. Six (21%) patients in the h-ANP group compared with 14 (47%) in the placebo group needed dialysis before or at day 21 (hazard ratio, 0.28; 95% confidence interval, 0.10-0.73; p =.009). Eight (28%) patients in the h-ANP group compared with 17 (57%) in the placebo group suffered from the combined end point dialysis or death before or at day 21 (hazard ratio, 0.35; 95% confidence interval, 0.14-0.82; p =.017). h-ANP improved creatinine clearance in contrast to placebo (p =.040).

CONCLUSIONS

Infusion of h-ANP at a rate of 50 ng.kg(-1).min(-1) enhances renal excretory function, decreases the probability of dialysis, and improves dialysis-free survival in early, ischemic acute renal dysfunction after complicated cardiac surgery.

Acute toxic renal failure

Acute renal failure (ARF) is a common problem in intensive care medicine. Even modest degrees of ARF not requiring dialysis treatment increase the risk of death approximately fivefold. Despite the widespread appreciation of the role of nephrotoxic drugs in their contribution to ARF, these drugs continue to have an ongoing aetiological role. Potentially nephrotoxic drugs include non-steroidal anti-inflammatory drugs, radiocontrast agents, antimicrobial and anaesthetic agents. Endogenous compounds such as myoglobin and haemoglobin may furthermore cause toxic nephropathy. Tubular injury initiated by toxins often results from a combination of acute renal vasoconstriction and direct cellular toxicity due to intracellular accumulation of the toxin, or, alternatively, may be mediated immunologically in case of interstitial nephritis. Patients with reduced renal functional reserve, cardiovascular co-morbidity, diabetes mellitus, and advanced age are at increased risk. Awareness of the range of toxins on the one hand and simple measures such as adequate pre-hydration of the patient and drug monitoring on the other hand may be sufficient to avoid drug-induced ARF or minimize its clinical severity in susceptible patients.

Outcome of pediatric patients treated with extracorporeal life support after cardiac surgery

BACKGROUND

Extracorporeal life support (ECLS) has been used for over two decades in select patients after cardiac surgery. We previously described factors associated with death in this population. We now review our recent experience to reassess factors related to mortality.

METHODS

All pediatric patients who received ECLS support within 7 days after surgery between July 1995 and June 2001 were examined to describe clinical features associated with survival. We compared the results with our prior report to assess changes in practice and outcome.

RESULTS

Seventy-four patients were followed. Fifty percent survived to discharge. Hospital survival was not significantly related to patient age, cannulation site, or indication. Thirty-five percent of patients required hemofiltration while on ECLS and were significantly less likely to survive (23% vs 65%). A multivariate analysis combining all children from our prior report with the present cohort revealed that patients who received hemofiltration were five times more likely to die (odds ratio 5.01, 95% confidence interval 2.11-11.88). Children with an adequate two-ventricular repair had lower risk of death (odds ratio 0.42, 95% confidence interval 0.19-0.91) after adjusting for patient age, study period, and hours elapsed before initiation of ECLS after surgery.

CONCLUSIONS

Patients with an adequate two-ventricle repair have significantly higher hospital survival, whereas those with single ventricle physiology or need for dialysis have decreased survival.

The utilisation of continuous veno-venous haemofiltration for the removal of septic mediators in patients with systemic inflammatory response syndrome

Septic shock is the leading cause of morbidity and mortality in critically ill patients. If the mediators responsible for the continuum of the sepsis cascade could be blocked or removed, patient outcome might improve. Researchers have been attempting to eliminate such mediators by continuous veno-venous haemofiltration (CVVH) but, despite over a decade of studies, many obstacles still remain. In this article, a comparison has been made of four similar research studies to ascertain any significant findings. Future research proposals have been considered in conjunction with the role the nurse within critical care might play in what could arguably be considered to be within the medical domain.

The other medical causes of rhabdomyolysis

Rhabdomyolysis is the clinical and laboratory syndrome resulting from skeletal muscle injury and release of potentially toxic substances into the circulation. The severity of rhabdomyolysis varies widely from asymptomatic elevation of muscle enzymes to the life-threatening complications of acute renal failure and severe electrolyte abnormalities. The etiology of rhabdomyolysis may be considered under 4 categories: (1) trauma or direct injury, (2) excessive muscle activity, (3) hereditary muscle enzyme defects, and (4) other less obvious medical causes. The latter medical causes may be subdivided into the following: (1) drugs and toxins, (2) muscle hypoxia, (3) metabolic and endocrine disorders, (4) infections, (5) temperature alterations, and (6) miscellaneous causes. The diagnosis of rhabdomyolysis depends on recognizing the symptoms of muscle pain and weakness, detecting the presence of or history of red-to-brown urine (myoglobinuria), and finding short-term elevations of creatine kinase that are not attributable to myocardial infarction or inflammatory myopathies. The major therapeutic goal is to recognize and treat complications as soon as possible, particularly electrolyte abnormalities and acute renal failure. Knowledge of the other medical causes of rhabdomyolysis allows one to identify and treat this potentially serious condition in otherwise occult cases.

Acetylcysteine and contrast media nephropathy

PURPOSE OF REVIEW

Radiographic contrast media are used at an increasing rate for several diagnostic and therapeutic applications. Therefore, contrast agent-induced nephropathy will become more important, including the risk of patient impairment and costs. The prevention of radiographic contrast-induced nephropathy is mandatory. Radiographic contrast agent-induced nephropathy is caused by vasoconstriction-mediated renal medullary ischaemia and direct toxic damage to renal tubular epithelial cells. These effects may be partly mediated by the generation of reactive oxygen species. Data from experimental studies indicate that antioxidants, e.g. acetylcysteine, may prevent radiocontrast-induced nephropathy.

RECENT FINDINGS

Two prospective, randomized, placebo-controlled studies in patients with moderate renal insufficiency confirmed that the prophylactic oral administration of acetylcysteine, at a dose of 600 mg twice a day along with hydration, prevents the reduction in renal function after radiocontrast administration.

SUMMARY

The use of acetylcysteine together with hydration is the treatment of choice to protect against radiographic contrast media-induced nephropathy.