Nonoliguric acute renal failure

Predictors of oliguria in post-traumatic acute kidney injury

BACKGROUND

Acute kidney injury is classified by urine output into non-oliguric and oliguric variants. Non-oliguric acute kidney injury has lower morbidity and mortality and accounts for up to 64% of acute kidney injury in hospitalized patients. However, the incidence of non-oliguric acute kidney injury in the trauma population and whether the 2 variants of acute kidney injury share the same risk factors is unknown. We hypothesized that oliguria would be present in the majority of acute kidney injury in severely injured trauma patients and that unique risk factors would predispose patients to the development of oliguria.

METHODS

Patients admitted to the trauma intensive care unit and diagnosed with an acute kidney injury between 2016 to 2021 were identified. Cases were categorized based on urine output into oliguric (<400 mL per day) and non-oliguric (>400 mL per day) disease. Risk factors, management, and outcomes were compared. Logistic regression was used to identify risk factors associated with oliguria.

RESULTS

A total of 227 patients met inclusion criteria. Non-oliguric acute kidney injury accounted for 74% of all cases and was associated with greater survival (78% vs 35.6%, P < .001). Using logistic regression, female sex, vasopressor use, and a greater net fluid balance at 48 hours were all predictive of oliguria (while controlling for age, race, shock index, massive transfusion, operative intervention, cardiac arrest, and nephrotoxic medication exposure).

CONCLUSION

Non-oliguria accounts for the majority of post-traumatic acute kidney injury and is associated with improved survival. Specific risk factors for the development of oliguric acute kidney injury include female sex, vasopressor use, and a higher net fluid balance at 48 hours.

Crush injury and syndrome: A review for emergency clinicians

INTRODUCTION

Primary disasters may result in mass casualty events with serious injuries, including crush injury and crush syndrome.

OBJECTIVE

This narrative review provides a focused overview of crush injury and crush syndrome for emergency clinicians.

DISCUSSION

Millions of people worldwide annually face natural or human-made disasters, which may lead to mass casualty events and severe medical issues including crush injury and syndrome. Crush injury is due to direct physical trauma and compression of the human body, most commonly involving the lower extremities. It may result in asphyxia, severe orthopedic injury, compartment syndrome, hypotension, and organ injury (including acute kidney injury). Crush syndrome is the systemic manifestation of severe, traumatic muscle injury. Emergency clinicians are at the forefront of the evaluation and treatment of these patients. Care at the incident scene is essential and focuses on treating life-threatening injuries, extrication, triage, fluid resuscitation, and transport. Care at the healthcare facility includes initial stabilization and trauma evaluation as well as treatment of any complication (e.g., compartment syndrome, hyperkalemia, rhabdomyolysis, acute kidney injury).

CONCLUSIONS

Crush injury and crush syndrome are common in natural and human-made disasters. Emergency clinicians must understand the pathophysiology, evaluation, and management of these conditions to optimize patient care.

Biomarkers in Acute Kidney Injury

Biomarkers have become a pillar of precision medicine in acute kidney injury (AKI). Traditional markers for diagnosis of AKI are insensitive and insufficient to provide comprehensive information for prognostication. Several emerging biomarkers have shown promising results in large-scale clinical studies. These novel markers likely will be beneficial for personalized AKI prevention and treatment.

Robust Association between Acute Kidney Injury after Radical Nephrectomy and Long-term Renal Function

The association between acute kidney injury (AKI) and long-term renal function after radical nephrectomy has not been evaluated fully. We reviewed 558 cases of radical nephrectomy. Postoperative AKI was defined by the Kidney Disease: Improving Global Outcomes (KDIGO) serum creatinine criteria. Values of estimated glomerular filtration rate (eGFR) were collected up to 36 months (median 35 months) after surgery. The primary outcome was new-onset chronic kidney disease (CKD) stage 3a or higher or all-cause mortality within three years after nephrectomy. The functional change ratio (FCR) of eGFR was defined as the ratio of the most recent GFR (24-36 months after surgery) to the new baseline during 3-12 months. A multivariable Cox proportional hazard regression analysis for new-onset CKD and a multivariable linear regression analysis for FCR were performed to evaluate the association between AKI and long-term renal outcomes. A correlation analysis was performed with the serum creatinine ratio and used to determine AKI and FCR. AKI occurred in 43.2% (n = 241/558) and our primary outcome developed in 40.5% (n = 226/558) of patients. The incidence of new-onset CKD was significantly higher in patients with AKI than those without at all follow-up time points after surgery. The Cox regression analysis showed a graded association between AKI and our primary outcome (AKI stage 1: Hazard ratio 1.71, 95% confidence interval 1.25-2.32; AKI stage 2 or 3: Hazard ratio 2.72, 95% confidence interval 1.78-4.10). The linear regression analysis for FCR showed that AKI was significantly associated with FCR (β = -0.168 ± 0.322, p = 0.011). There was a significant negative correlation between the serum creatinine ratio and FCR. In conclusion, our analysis demonstrated a robust and graded association between AKI after radical nephrectomy and long-term renal functional deterioration.

Urinary Sodium/Potassium Ratio in Acute Kidney Injury Accurately Differentiates Prerenal Azotemia from Acute Tubular Necrosis

Objective: To develop a more accurate, cost effective, non-invasive test to differentiate between pre-renal renal failure (PRA) and acute tubular necrosis (ATN) in acute kidney injury (AKI).

Methods: Urine sodium/potassium (Na/K) ratios were compared with fractional excretion of sodium (FeNa) and renal failure index (RFI) as well as other commonly used indices to differentiate patients with PRA from ATN. Patients with a rise in serum creatinine > 0.5 mg/d identified from medical records for a six- to eighteen-month period, were reviewed and categorized either as PRA or ATN based on presenting findings, course in hospital or renal biopsy. All patients had urinary sodium and potassium, creatinine, and serum creatinine done.

Results: The Na/K was < 1 in PRA and > 1 in ATN, correctly identifying all 42 cases of PRA and all 28 patients with ATN. The FeNa was >1 and misdiagnosed 9 of 42 patients with PRA and was >1 and correctly diagnosed all patients with ATN. The RFI was >1 and misdiagnosed 11 of 42 patients with PRA but was >1 and correctly diagnosed all patients with ATN. The BUN/creatinine ratio, urine sodium concentration and U/P creatinine ratio all had a very poor correlation with the correct diagnosis.

Conclusion: The Na/K ratio correctly diagnosed all 42 cases of PRA and all 28 cases of ATN. It is easy to do, is cost effective, non-invasive, and is useful for following patients with PRA to see if and when they develop ATN.

Intraoperative Oliguria with Decreased SvO₂ Predicts Acute Kidney Injury after Living Donor Liver Transplantation

Acute kidney injury (AKI) is a frequent complication after living donor liver transplantation (LDLT), and is associated with increased mortality. However, the association between intraoperative oliguria and the risk of AKI remains uncertain for LDLT. We sought to determine the association between intraoperative oliguria alone and oliguria coupled with hemodynamic derangement and the risk of AKI after LDLT. We evaluated the hemodynamic variables, including mean arterial pressure, cardiac index, and mixed venous oxygen saturation (SvO₂). We reviewed 583 adult patients without baseline renal dysfunction and who did not receive hydroxyethyl starch during surgery. AKI was defined using the Kidney Disease Improving Global Outcomes criteria according to the serum creatinine criteria. Multivariable logistic regression analysis was performed with and without oliguria and oliguria coupled with a decrease in SvO₂. The performance was compared with respect to the area under the receiver operating characteristic curve (AUC). Intraoperative oliguria <0.5 and <0.3 mL/kg/h were significantly associated with the risk of AKI; however, their performance in predicting AKI was poor. The AUC of single predictors increased significantly when oliguria was combined with decreased SvO₂ (AUC 0.72; 95% confidence interval (CI) 0.68–0.75 vs. AUC of oliguria alone 0.61; 95% CI 0.56–0.61; p < 0.0001; vs. AUC of SvO₂ alone 0.66; 95% CI 0.61–0.70; p < 0.0001). Addition of oliguria coupled with SvO₂ reduction also increased the AUC of multivariable prediction (AUC 0.87; 95% CI 0.84–0.90 vs. AUC with oliguria 0.73; 95% CI 0.69–0.77; p < 0.0001; vs. AUC with neither oliguria nor SvO₂ reduction 0.68; 95% CI 0.64–0.72; p < 0.0001). Intraoperative oliguria coupled with a decrease in SvO₂ may suggest the risk of AKI after LDLT more reliably than oliguria alone or decrease in SvO₂ alone. Intraoperative oliguria should be interpreted in conjunction with SvO₂ to predict AKI in patients with normal preoperative renal function and who did not receive hydroxyethyl starch during surgery.

Intravenous Contrast-Induced Nephropathy-The Rise and Fall of a Threatening Idea

Contrast-induced nephropathy (CIN) has been considered to be a cause of renal failure for over 50 years, but careful review of past and recent studies reveals the risks of CIN to be overestimated. Older studies frequently cited the use of high-osmolality contrast media, which have since been replaced by low-osmolality contrast media, which have lower risks for nephropathy. In addition, literature regarding CIN typically describes the incidence following cardiac angiography, whereas the risk of CIN from intravenous injection is much lower. Most of the early published literature also lacked appropriate control groups to compare to those that received iodinated contrast, and thus attributed rises in creatinine to intravenous contrast without considering normal creatinine fluctuations (frequent in patients with kidney disease) and other acute pathologic states such as hypotension or nephrotoxic drug administration. The aim of this paper is to review the literature detailing CIN risk, discuss why CIN risk is often overestimated and how withholding contrast can lead to misdiagnosis and delay in appropriate patient management.

Comparison of Urine Output among Patients Treated with More Intensive Versus Less Intensive RRT: Results from the Acute Renal Failure Trial Network Study

BACKGROUND AND OBJECTIVES

Intensive RRT may have adverse effects that account for the absence of benefit observed in randomized trials of more intensive versus less intensive RRT. We wished to determine the association of more intensive RRT with changes in urine output as a marker of worsening residual renal function in critically ill patients with severe AKI.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Acute Renal Failure Trial Network Study (n=1124) was a multicenter trial that randomized critically ill patients requiring initiation of RRT to more intensive (hemodialysis or sustained low-efficiency dialysis six times per week or continuous venovenous hemodiafiltration at 35 ml/kg per hour) versus less intensive (hemodialysis or sustained low-efficiency dialysis three times per week or continuous venovenous hemodiafiltration at 20 ml/kg per hour) RRT. Mixed linear regression models were fit to estimate the association of RRT intensity with change in daily urine output in survivors through day 7 (n=871); Cox regression models were fit to determine the association of RRT intensity with time to ≥50% decline in urine output in all patients through day 28.

RESULTS

Mean age of participants was 60±15 years old, 72% were men, and 30% were diabetic. In unadjusted models, among patients who survived ≥7 days, mean urine output was, on average, 31.7 ml/d higher (95% confidence interval, 8.2 to 55.2 ml/d) for the less intensive group compared with the more intensive group (P=0.01). More intensive RRT was associated with 29% greater unadjusted risk of decline in urine output of ≥50% (hazard ratio, 1.29; 95% confidence interval, 1.10 to 1.51).

CONCLUSIONS

More intensive versus less intensive RRT is associated with a greater reduction in urine output during the first 7 days of therapy and a greater risk of developing a decline in urine output of ≥50% in critically ill patients with severe AKI.

Acute Renal Failure in Critically Ill Patients

Acute renal failure is an important cause of morbidity in critically ill patients. Acute renal failure results from pre renal and postrenal causes and, most importantly, acute tubular necrosis (ATN). Although it is known that renal toxins and renal ischemia are the most common causes of ATN in hospitalized patients, the exact pathogenesis of this entity is still not fully understood. Patients in the intensive care unit are at high risk for ATN because of hemodynamic instability, the administration of neph rotoxic antibiotics or chemotherapeutic agents, and ex posure to radiographic contrast agents. The acquired immunodeficiency syndrome is also associated with an increased risk of renal failure development, either from complications of the disease itself or from its treatment. Many consequences of acute renal failure such as vol ume overload, acidosis, hyperkalemia, and serositis can be managed adequately with peritoneal dialysis, hemo dialysis, or a newer technique, continuous arteriove nous hemofiltration. Despite improvements in treat ment, however, the mortality of ATN remains high. In this review, we recommend measures to prevent ATN in certain clinical situations that commonly occur among critically ill patients. We also review therapeutic options for treating patients in whom acute renal failure devel ops and discuss newer developments that may begin to reduce the excessive morbidity associated with ATN.

Comparison of combination therapy of high-dose oral N-acetylcysteine and intravenous sodium bicarbonate hydration with individual therapies in the reduction of Contrast-induced Nephropathy during Cardiac Catheterisation and Percutaneous Coronary Intervention (CONTRAST): A multi-centre, randomised, controlled trial

INTRODUCTION

N-acetylcysteine (NAC) and sodium bicarbonate (SOB) therapies may prevent contrast-induced nephropathy (CIN). However, the efficacy of using combination over individual therapies was not established, and there was no large randomised study comparing abbreviated SOB therapy with conventional sustained saline pre-hydration with oral NAC.

METHODS

In a multi-centre, open-label, randomised, controlled trial (NCT00497328), we prospectively enrolled 548 patients with at least moderate renal impairment undergoing cardiac catheterisation with or without percutaneous coronary intervention. Patients were randomly assigned to 3 groups: 1) NAC: 154 mEq/L sustained sodium chloride regime (1 mL/kg/h 12 h before, during and 6h after the procedure) with oral NAC at 1.2g bid for 3 days (n=185); 2) SOB: 154 mEq/L abbreviated SOB regime at 3 mL/kg/h 1h before the procedure, and 1 mL/kg/h during and 6h after the procedure (n=182); and 3) COM: combination of abbreviated SOB regime and oral NAC (n=181). The primary end point was incidence of CIN. The secondary end points were rise in serum creatinine, hospitalisation duration, haemodialysis, morbidity and mortality within 30 days.

RESULTS

The 3 groups had similar baseline characteristics: age 68 ± 10 years, 76% male, 48% diabetic and baseline glomerular filtration rate (GFR) 47.7 ± 13.0 mL/min. There were 41 (8.8%) patients with GFR<30. The CIN incidences were NAC 6.5%, SOB 12.8% and COM 10.6%. The COM regimen was not superior to either the NAC (relative risk (RR)=1.61, 95% confidence interval (CI): 0.76 to 3.45, p=0.225) or SOB (RR=0.83, 95% CI: 0.44 to 1.56, p=0.593) regimens. The CIN incidence was lower in the NAC group than the SOB group (adjusted odds ratio (OR)=0.40, 95% CI: 0.17 to 0.92; p=0.032). Multivariate analysis showed contrast volume (OR=1.99, 95% CI: 1.33 to 2.96, p<0.001 per 100mL), female (OR=2.47, 95% CI: 1.22 to 5.00, p=0.012) and diabetes (OR=2.03, 95% CI: 1.03 to 3.99, p=0.041) were independent risk predictors. There were no differences in the secondary outcomes among the 3 groups.

CONCLUSION

The combination regimen was not superior to individual regimens in preventing CIN in patients with baseline renal impairment. There was a trend suggesting that the 12-hour sustained sodium chloride pre-hydration regimen was more protective than the 1-hour abbreviated SOB regimen.

The Frequency and Outcome of Acute Kidney Injury in a Tertiary Hospital: Which Factors Affect Mortality?

Acute kidney injury (AKI) is a major cause of mortality and morbidity in hospitalized patients. Incidence and mortality rates vary from country to country, and according to different in-hospital monitoring units and definitions of AKI. The aim of this study was to determine factors affecting frequency of AKI and mortality in our hospital. We retrospectively evaluated data for 1550 patients diagnosed with AKI and 788 patients meeting the Kidney Disease: Improving Global Outcomes (KDIGO) guideline AKI criteria out of a total of 174 852 patients hospitalized in our institution between January 1, 2007 and December 31, 2012. Staging was performed based on KDIGO Clinical Practice for Acute Kidney Injury and RIFLE (Risk, Injury, Failure, Loss of kidney function and End-stage renal failure). Demographic and biochemical data were recorded and correlations with mortality were assessed. The frequency of AKI in our hospital was 0.9%, with an in-hospital mortality rate of 34.6%. At multivariate analysis, diastolic blood pressure (OR 0.89, 95% CI 0.87-0.92; P < 0.001), monitoring in the intensive care unit (OR 0.18, 95% CI 0.09-0.38; P < 0.001), urine output (OR 4.00, 95% CI 2.03-7.89; P < 0.001), duration of oliguria (OR 1.51, 95% CI 1.34-1.69; P < 0.001), length of hospitalization (OR 0.83, 95% CI 0.79-0.88; P < 0.001), dialysis requirement (OR 2.30, 95% CI 1.12-4.71; P < 0.05), APACHE II score (OR 1.16, 95% CI 1.09-1.24; P < 0.001), and albumin level (OR 0.32, 95% CI 0.21-0.50; P < 0.001) were identified as independent determinants affecting mortality. Frequency of AKI and associated mortality rates in our regional reference hospital were compatible with those in the literature. This study shows that KDIGO criteria are more sensitive in determining AKI. Mortality was not correlated with staging based on RIFLE or KDIGO. Nonetheless, our identification of urine output as one of the independent determinants of mortality suggests that this parameter should be used in assessing the correlation between staging and mortality.

Proteinuria and hematuria are associated with acute kidney injury and mortality in critically ill patients: a retrospective observational study

BACKGROUND

Proteinuria and hematuria are both important health issues; however, the nature of the association between these findings and acute kidney injury (AKI) or mortality remains unresolved in critically ill patients.

METHODS

Proteinuria and hematuria were measured by a dipstick test and scored using a scale ranging from a negative result to 3+ in 1883 patients admitted to the intensive care unit. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. The odds ratios (ORs) for AKI and 3-year mortality were calculated after adjustment for multiple covariates according to the degree of proteinuria or hematuria. For evaluating the synergistic effect on mortality among proteinuria, hematuria, and AKI, the relative excess risk due to interaction (RERI) was used.

RESULTS

Proteinuria and hematuria increased the ORs for AKI: the ORs of proteinuria were 1.66 (+/-), 1.86 (1+), 2.18 (2+), and 4.74 (3+) compared with non-proteinuria; the ORs of hematuria were 1.31 (+/-), 1.58 (1+), 2.63 (2+), and 2.52 (3+) compared with non-hematuria. The correlations between the mortality risk and proteinuria or hematuria were all significant and graded (Ptrend<0.001). There was a relative excess risk of mortality when both AKI and proteinuria or hematuria were considered together: the synergy indexes were 1.30 and 1.23 for proteinuria and hematuria, respectively.

CONCLUSIONS

Proteinuria and hematuria are associated with the risks of AKI and mortality in critically ill patients. Additionally, these findings had a synergistic effect with AKI on mortality.

[Perioperative acute kidney injury and failure]

Perioperative period is very likely to lead to acute renal failure because of anesthesia (general or perimedullary) and/or surgery which can cause acute kidney injury. Characterization of acute renal failure is based on serum creatinine level which is imprecise during and following surgery. Studies are based on various definitions of acute renal failure with different thresholds which skewed their comparisons. The RIFLE classification (risk, injury, failure, loss, end stage kidney disease) allows clinicians to distinguish in a similar manner between different stages of acute kidney injury rather than using a unique definition of acute renal failure. Acute renal failure during the perioperative period can mainly be explained by iatrogenic, hemodynamic or surgical causes and can result in an increased morbi-mortality. Prevention of this complication requires hemodynamic optimization (venous return, cardiac output, vascular resistance), discontinuation of nephrotoxic drugs but also knowledge of the different steps of the surgery to avoid further degradation of renal perfusion. Diuretics do not prevent acute renal failure and may even push it forward especially during the perioperative period when venous retourn is already reduced. Edema or weight gain following surgery are not correlated with the vascular compartment volume, much less with renal perfusion. Treatment of perioperative acute renal failure is similar to other acute renal failure. Renal replacement therapy must be mastered to prevent any additional risk of hemodynamic instability or hydro-electrolytic imbalance.

Medical causes of acute kidney injury- clinical and therapeutic aspects in constanta county

Introduction. Acute kidney injury represents an important clinical syndrome within nephrology, approximately 5% of hospitalised patients being affected. Establishing a diagnosis for acute kidney injury can be challenging and requires many steps. A complete and correct diagnosis is essential for appropriate therapy and, ultimately, the patient’s prognosis.

Methods. An objective of this study is to determine the presentation of certain characteristics for the diagnosis of acute kidney injury. It is also intended to show the therapeutic methods undertaken for patients presenting with acute kidney injury, as well as evolution under therapy.

Results. The most common causes of acute kidney injury were medical causes and within that category, cardiovascular diseases were the most common etiological factor (18%). Nephropathies represented a minority, with acute pyelonephritis, responsible for 5% of medical causes, and acute glomerulonephritis accounting for 6%. Hemodialysis was initiated only in 15% of patients. The rest of the patients were treated conservatively and responded favourably to this therapeutic approach. The etiological factors that had the greatest number of patients requiring hemodialysis were Rifampicin administration and leptospirosis (~20% each).

Conclusions. The clinical characteristics of acute kidney injury are variable and are usually specific to the etiology of the disease. The most common causes were cardiovascular diseases (18%). The therapeutic approach was rather conservative. Hemodialysis was instituted only in 15% of the patients. Almost 5% of all patients evolved to chronic kidney disease in a variable period of time, and the overall mortality was 18%, mainly due to infections and cardiovascular complications.

Spectrum of acute kidney injury in the Himalayan region

Acute kidney injury (AKI) is common in hospitalized patients and is an important cause of mortality. This is a descriptive study of AKI in patients from Himachal Pradesh, India, located in Western Himalayan region. Over a period of 1 year, 102 patients with clinical and laboratory evidence of azotemia were included. Out of 102 patients, 84.3% had community acquired AKI and 15.7% had hospital acquired AKI. Medical causes were leading contributors (85.3%), with septicemia being the main factor (33.3%). Multiorgan failure was present in 59.8% patients. The overall mortality was 29.2%, and community acquired AKI was associated with higher mortality as compared to hospital-acquired AKI (22.5% vs 6.7%). AKI is still common in community and associated with high mortality. Septicemia, volume depletion and nephrotoxins were the leading cause of AKI in our study. Our study highlights the presence of hypotension, multiorgan failure and oliguria with mortality. Community-acquired AKI had higher mortality than hospital-acquired AKI.

Diagnostic value of urinary sodium, chloride, urea, and flow

Up to 30% of hospitalized critically ill patients may have a rise in serum creatinine concentration. In addition to history and physical examination, there is diagnostic value in assessing urinary electrolytes, solute excretion, and urine flow in these patients. The correct interpretation of these urinary parameters can avoid unnecessary volume overload and mechanical ventilation, risk factors for increased mortality in patients with rising serum creatinine. The present article also discusses the role of arterial underfilling in causing prerenal azotemia in the presence of an increase in total body sodium and extracellular fluid expansion. As with extracellular fluid volume depletion, arterial underfilling secondary to impaired cardiac function or primary arterial vasodilation can delay or prevent recovery from ischemic or toxic acute tubular necrosis. The present brief review discusses the various aspects of the correct interpretation of urinary electrolytes, solute excretion, and urine flow in the setting of a rising serum creatinine concentration.

Oliguria as predictive biomarker of acute kidney injury in critically ill patients

INTRODUCTION

During critical illness, oliguria is often used as a biomarker of acute kidney injury (AKI). However, its relationship with the subsequent development of AKI has not been prospectively evaluated.

METHODS

We documented urine output and daily serum creatinine concentration in patients admitted for more than 24 hours in seven intensive care units (ICUs) from six countries over a period of two to four weeks. Oliguria was defined by a urine output < 0.5 ml/kg/hr. Data were collected until the occurrence of creatinine-defined AKI (AKI-Cr), designated by RIFLE-Injury class or greater using creatinine criteria (RIFLE-I[Cr]), or until ICU discharge. Episodes of oliguria were classified by longest duration of consecutive oliguria during each day were correlated with new AKI-Cr the next day, examining cut-offs for oliguria of greater than 1,2,3,4,5,6, or 12 hr duration,

RESULTS

We studied 239 patients during 723 days. Overall, 32 patients had AKI on ICU admission, while in 23, AKI-Cr developed in ICU. Oliguria of greater than one hour was significantly associated with AKI-Cr the next day. On receiver-operator characteristic area under the curve (ROCAUC) analysis, oliguria showed fair predictive ability for AKI-Cr (ROCAUC = 0.75; CI:0.64-0.85). The presence of 4 hrs or more oliguria provided the best discrimination (sensitivity 52% (0.31-0.73%), specificity 86% (0.84-0.89%), positive likelihood ratio 3.8 (2.2-5.6), P < 0.0001) with negative predictive value of 98% (0.97-0.99). Oliguria preceding AKI-Cr was more likely to be associated with lower blood pressure, higher heart rate and use of vasopressors or inotropes and was more likely to prompt clinical intervention. However, only 30 of 487 individual episodes of oliguria preceded the new occurrence of AKI-Cr the next day.

CONCLUSIONS

Oliguria was significantly associated with the occurrence of new AKI-Cr, however oliguria occurred frequently compared to the small number of patients (~10%) developing AKI-Cr in the ICU, so that most episodes of oliguria were not followed by renal injury. Consequently, the occurrence of short periods (1-6 hr) of oliguria lacked utility in discriminating patients with incipient AKI-Cr (positive likelihood ratios of 2-4, with > 10 considered indicative of a useful screening test). However, oliguria accompanied by hemodynamic compromise or increasing vasopressor dose may represent a clinically useful trigger for other early biomarkers of renal injury.

Contrast induced nephropathy in urology

Intravenous contrast agents have a distinct role in urological imaging: to study precise anatomical delineation, vascularity, and to assess the function of the renal unit. Contrast induced nephropathy (CIN) is a known adverse effect of intravenous contrast administration. The literature on incidence, pathophysiology, clinical features, and current preventive strategies available for CIN relevant to urologists was reviewed. A search of the PubMed database was done using the keywords nephropathy and media, prevention and control or prevention Contrast media (explode), all adverse effects, and kidney diseases (explode). An online search of the EMBASE database for the time ranging from 1977 to February 2009 was performed using the keywords ionic contrast medium, adverse drug reaction, major or controlled clinical study, human, nephrotoxicity, and kidney disease. Current publications and data most relevant to urologists were examined. CIN was the third most common cause of hospital-acquired renal failure. The incidence is less common with intravenous contrast administration as compared with intra-arterial administration. The pathogenesis of contrast mediated nephropathy is due to a combination of toxic injury to renal tubules and medullary ischemic injury mediated by reactive oxygen species. CIN most commonly manifests as a nonoliguric and asymptomatic transient decline in renal function. Patients who developed CIN were found to have increased mortality, longer hospital stay, and complicated clinical course. An overview of risk factors and risk prediction score for prognostication of CIN are elaborated. Preventive strategies including choice of contrast agents, maximum tolerated dose, role of hydration, hydration regime, etc. are discussed. The role of N- acetyl cysteine, Theophylline, Fenoldapam, Endothelin receptor antagonists, iloprost, atrial natriuretic peptide, and newer therapies such as targeted renal therapy (TRT) are discussed. A working algorithm based on current evidence is proposed. No current treatment can reverse or ameliorate CIN once it occurs, but prophylaxis is possible.

Acute kidney injury: current perspectives

Acute kidney injury (AKI) increases morbidity and mortality, particularly for the critically ill. Recent definitions standardizing AKI to reflect graded changes in serum creatinine and urine output (per the Risk, Injury, Failure, Loss, and End-stage renal failure [RIFLE] and Acute Kidney Injury Network [AKIN] criteria) with severity of renal injury and developments in AKI pathobiology are being utilized to identify biomarkers of early kidney injury. These developments may be useful in the early intervention of preventing AKI. Although there has been progress in the management of AKI, therapeutic challenges include appropriate prophylaxis prior to contrast administration, use of diuretics, vasopressors, and the type and dose of renal replacement therapy. Future use of bioartificial dialyzers, plasma therapies, and the possibility of stem cell regeneration of injured kidney tissue are being actively investigated to provide alternative treatment options for AKI. This review aims to provide an overview of current practices, available therapies, and continued research in AKI therapy.

Update on the diagnosis and management of acute kidney injury

Acute kidney injury (AKI) is an independent risk factor for morbidity and mortality. This review provides essential information for the diagnosis and management of AKI. Blood urea nitrogen and serum creatinine are used for the diagnosis of AKI. The review also focuses on recent studies on the diagnosis of AKI using the RIFLE (R-renal risk, I-injury, F-failure, L-loss of kidney function, E-end stage kidney disease) and Acute Kidney Injury Network criteria, and serum and urine AKI biomarkers. Dialysis is the only Food and Drug Administration-approved therapy for AKI. Recent studies on the dose of dialysis in AKI are reviewed.

The prevention of acute kidney injury an in-depth narrative review: Part 2: Drugs in the prevention of acute kidney injury

The second part of this in-depth clinical review focuses on drugs used in the prevention of AKI in the patient at risk and/or in the management of the patient with incipient AKI. Among the drugs used to maintain a normal renal perfusion pressure, norepinephrine and vasopressin are most commonly used in hypotensive critically ill patients. The most recent RCT did not find a difference between low-dose vasopressin plus norepinephrine and norepinephrine alone in patients with septic shock, suggesting that either approach is reasonable. However, vasopressin may be beneficial in the less severe septic shock subgroup. Loop diuretics may convert an oliguric into a non-oliguric form of AKI that may allow easier fluid and/or nutritional support of the patient. Volume overload in AKI patients is common and diuretics may provide symptomatic benefit in that situation. However, loop diuretics are neither associated with improved survival, nor with better recovery of renal function in AKI. Among the renal vasodilating drugs, the routine administration of dopamine to patients for the prevention of AKI or incipient AKI is no longer justified. On the other hand, although additional studies may be warranted, fenoldopam may appear to be a likely candidate for the prevention of AKI, particularly in critically ill patients, if the positive results obtained in some recent studies are confirmed. Trials with natriuretic peptides were in general inconclusive but despite the fact that nesiritide is currently approved by the FDA only for the treatment of heart failure, this vasodilator may in the future play a role in the prevention of AKI, particularly in association with heart failure and cardiac surgery. The most recent trials seem to confirm a potential positive preventive effect of N-acetylcysteine (NAC), particularly in contrast-induced nephropathy (CIN), NAC alone should never take the place of IV hydration in patients at risk for CIN; fluids likely have a more substantiated benefit. At present, initiation of statin therapy for the prevention of CIN cannot be recommended, but these drugs should not be stopped before a radiological intervention in patients on chronic statin therapy. Rasburicase is very effective in the prevention of acute tumour lysis syndrome. Erythropoietin (EPO) has tissue-protective effects and prevents tissue damage during ischaemia and inflammation, and currently trials are performed with EPO in the prevention of AKI post-cardiac surgery, CIN and post-kidney transplantation. From this review it becomes clear that single-drug therapy will probably never be effective in the prevention of AKI and that multiple agents may be needed to improve outcomes. In addition, drugs should be administered early during the course of the disease.

Management of acute renal failure in the elderly patient: a clinician's guide

Numerous anatomical and functional changes occurring in the aging kidney lead to reduced glomerular filtration rate, lower renal blood flow and impaired renal autoregulation. The elderly are especially vulnerable to the development of renal dysfunction and in this population acute renal failure (ARF) is a common problem. ARF is often iatrogenic and multifactorial; common iatrogenic combinations include pre-existing renal dysfunction and exposure to nephrotoxins such as radiocontrast agents or aminoglycosides, use of NSAIDs in patients with congestive cardiac failure and use of ACE inhibitors and diuretics in patients with underlying atherosclerotic renal artery stenosis. The aetiology of ARF is classically grouped into three categories: prerenal, intrinsic and postrenal. Prerenal ARF is the second most common cause of ARF in the elderly, accounting for nearly one-third of all hospitalized cases. Common causes can be grouped into true volume depletion (e.g. decreased fluid intake), decreased effective blood volume (e.g. systemic vasodilation) and haemodynamic (e.g. renal artery stenosis, NSAID use). Acute tubular necrosis (ATN) is the most common cause of intrinsic ARF and is responsible for over 50% of ARF in hospitalized patients, and up to 76% of cases in patients in intensive care units. ATN usually occurs after an acute ischaemic or toxic event. The pathogenesis of ATN involves an interplay of processes that include endothelial injury, microvascular flow disruption, tubular hypoxia, dysfunction and apoptosis, tubular obstruction and trans-tubular back-leak. Vasculitis causing ARF should not be missed as this condition is potentially life threatening. The likelihood of a postrenal cause for ARF increases with age. Benign prostatic hypertrophy, prostatic carcinoma and pelvic malignancies are all important causes. Early identification of ARF secondary to obstruction with renal imaging is essential, and complete or partial renal recovery usually ensues following relief of the obstruction.A comprehensive medical and drug history and physical examination are all invaluable. Particular attention should be paid to the fluid status of the patient (skin turgor, jugular venous pressure, lying and standing blood pressure, urine output). Urinalysis should be performed to detect evidence of proteinuria and haematuria, which will aid diagnosis. Fractional excretion of sodium and urine osmolality may be measured but the widespread use of diuretics in the elderly gives rise to unreliable results. Renal imaging, usually ultrasound scanning, is routinely performed for assessment of renal size and to exclude urinary obstruction. In some cases, renal biopsy is necessary to provide specific diagnostic information. The general principles of managing ARF include treatment of life-threatening features such as shock, respiratory failure, hyperkalaemia, pulmonary oedema, metabolic acidosis and sepsis; stopping and avoiding administration of nephrotoxins; optimization of haemodynamic and fluid status; adjustment of drug dosage appropriate to glomerular filtration rate; early nutritional support; and early referral to nephrologists for diagnosis of ARF cause, timely initiation of dialysis and initiation of specific treatment. The treatment of prerenal and ATN ARF is largely supportive with little evidence of benefit from current pharmacological therapies. Despite advances in critical care medicine and renal replacement therapy, the mortality of ARF has not changed significantly over the last 40 years, with current mortality rates being up to 75%.

Contrast safety in the cancer patient: preventing contrast-induced nephropathy

Cancer patients undergo frequent imaging examinations. Computed tomography (CT) examinations for tumor staging and assessment of treatment response generally require administration of intravascular contrast medium. Iodinated contrast agents for CT are associated with the risk of contrast-induced nephrotoxicity (CIN), particularly in patients with impaired renal function and diabetes. In many cancer patients the risk of complications from intravascular contrast medium administration is compounded by advanced age, dehydration and coadministration of nephrotoxic chemotherapeutic drugs. In this article I review the definition, clinical manifestations, possible mechanisms and risk factors for CIN, and provide recommendations for prevention of this potentially life-threatening complication.

Acute renal failure in intensive care burn patients (ARF in burn patients)

The purpose of this study was to establish the incidence and mortality of burn patients with acute renal failure (ARF) at the Helsinki Burn Centre and to analyze the associated factors. The files of 238 intensive care (ICU) patients of a total of 1380 burn patients admitted to our institution between November 1988 and December 2001 were studied retrospectively. Of all admitted burn patients, 17.2% needed ICU. According to our criteria (S-Cr >120 micromol/l = 1.4 mg/dl), 39.1% of the ICU patients suffered from ARF and one in three of these required renal replacement therapy. The proportion of all admitted burn patients requiring renal replacement therapy was 2.3%. The mortality of ICU patients with ARF was 44.1% whereas that of patients without ARF was only 6.9%. Renal function recovered in all survivors. The nonsurvivors had a larger burned total body surface area, were older, and had more inhalation injuries and a higher abbreviated burn severity index score. The prognosis for patients with early ARF was worse than that for patients with late ARF. Rhabdomyolysis caused by flame injury was associated with high mortality. In this study we observed that ARF is associated with higher mortality even in minor burns when compared with patients without ARF. Flame burn with rhabdomyolysis and subsequent ARF predicts very poor survival. If a patient with severe ARF survives, the renal failure recovers over time.

Early renal replacement therapy in patients with postoperative acute liver failure associated with acute renal failure: effect on postoperative outcomes

BACKGROUND

Acute liver failure after major surgical procedures is associated with a high risk of multiple organ failure, including acute renal failure. The optimal time to initiate renal replacement therapy for acute renal failure is controversial because of the poor overall clinical outcomes.

STUDY DESIGN

From July 2002 to January 2005, all patients who had no history of liver disease, but developed acute liver failure and subsequent renal failure requiring renal replacement therapy after major surgery, at a surgical intensive care unit, were retrospectively analyzed. Patients were divided into early or late dialysis groups based on an arbitrary blood urea nitrogen cut-off level of 80 mg/dL before renal replacement therapy.

RESULTS

Eighty consecutive patients (21 women), with a mean age of 57.8+/-17.0 (SD) years, comprised the study group. The late dialysis group (n=26) had a higher ICU mortality rate (p=0.02) and a lower renal function recovery rate (p=0.02) than the early dialysis group (n=54). Fifty-three (66.3%) patients died during their ICU stay. Independent risk factors for ICU mortality were renal replacement therapy modality (intermittent hemodialysis versus continuous venous-venous hemofiltration; odds ratio [OR]=4.32, 95% CI 1.26 to 14.79; p=0.02), predialysis APACHE II score> 20 (OR=6.52, 95% CI 1.61 to 26.36; p < 0.01), and late dialysis (OR=4.01, 95% CI 1.05 to 15.27; p=0.04).

CONCLUSIONS

The mortality rate in postoperative patients with acute liver failure-associated acute renal failure was very high. Earlier initiation of renal replacement therapy, based on the predialysis blood urea nitrogen level, with continuous venous-venous hemofiltration might provide a better ICU survival rate.

Surgical critical care: from old boundaries to new frontiers

The surgical specialty of critical care has evolved into a field where the surgeon manages complex medical and surgical problems in critically ill patients. As a specialty, surgical critical care began when acutely ill surgical patients were placed in a designated area within a hospital to facilitate the delivery of medical care. As technology evolved to allow for development of increasingly intricate and sophisticated adjuncts to care, there has been recognition of the importance of physician availability and continuity of care as key factors in improving patient outcomes. Guidelines and protocols have been established to ensure quality improvement and are essential to licensing by state and national agencies. The modern ICU team provides continuous daily care to the patient in close communication with the primary operating physician. While the ultimate responsibility befalls the primary physician who performed the preoperative evaluation and operative procedure, the intensivist is expected to establish and enforce protocols, guidelines and patient care pathways for the critical care unit. It is difficult to imagine modern surgical ICU care without the surgical critical care specialist at the helm.

Continuous renal replacement therapy in patients following traumatic injury

In critically injured patients, the incidence of acute renal failure has been reported to occur in as many as 31% of patients. The use of CRRT modalities for patients following traumatic injuries is becoming more common, albeit slowly, and this therapy may impact upon long-term recovery of renal function and mortality. Historical studies investigating the early use of intermittent dialysis reported significant improvement in survival in patients who were dialyzed earlier and more vigorously than in control subjects. Early trauma patients also showed improved survival following war injuries when dialyzed prophylactically. Although there is a growing acceptance in favor of earlier renal replacement therapy, the published consensus and the practice in many centers has been to dialyze/filter relatively ill rather than relatively healthy patients. The R Adams Cowley Shock Trauma Center (STC) in Baltimore, Maryland, USA, admits over 8,000 trauma patients each year. Within the STC, a program of continuous renal replacement therapy was established in the early 1980's. We review both historical and current literature on the use of renal replacement therapies after traumatic injury, and suggest some future areas of investigation and indications for these modalities.

Oliguria, Volume Overload, Na+ Balance, and Diuretics

This article discusses the pathophysiology and treatment of common fluid and electrolyte disorders in the ICU. The presence of oliguria should alert the intensivist to identify the underlying cause rather than to resort reflexively to measures, such as diuretics or dopamine, to establish urine flow. Hypo- and hypernatremia, which are exceedingly commonly in the ICU setting, also are discussed using a pathophysiologic approach.

Pediatric acute renal failure in southwestern Nigeria

BACKGROUND

Acute renal failure (ARF) was investigated to determine the prevalence of ARF clinical types, etiology, comorbidities, and outcome in Nigerian children.

METHODS

Consecutive cases of ARF admitted from March, 1994 through February, 2003 were prospectively studied. Information were obtained concerning the following: age, gender, body surface area, early (within 48 hours of onset of ARF) or late (>48 hours of onset of ARF) presentation, admission duration, etiology, comorbidities, urine volume/day, dialysis need, reasons for considering dialysis, laboratory investigations, and outcome in each patient. Histopathologic reports of percutaneous renal and surgical biopsies, as well as autopsy specimens, were reviewed.

RESULTS

There were 78 boys and 45 girls (M:F, 1.73:1); mean age was 6.28 +/- 4.0 years. A portion of patients presented early (46.3%), while 53.7% presented late. Oliguric (63.41%), anuric (20.33%), and nonoliguric (16.26%) ARF were the clinical types seen. Dialysis requirement was significantly higher in oliguric (P < 0.005) and anuric (P < 0.005) than nonoliguric ARF. Primary and secondary etiologies accounted for 29% and 71% of ARF cases, respectively. Renal Burkitt's lymphoma (47.2%), glomerulonephritis (27.8%), nephrotic syndrome (16.7%), hemolytic uremic syndrome (5.5%), and acute tubulointerstitial nephritis (2.8%) were primary etiologies. Plasmodium falciparum malaria (42.53%), septicemia (28.73%), hypovolemia (11.49%), and obstructive uropathy (8.05%) were major secondary etiologies. Financial constraints on the part of parents of patients, as well as inadequate and/or lack of dialysis equipment, were major inhibitions to effective management of the patients; in fact, 6 patients took voluntary discharge due to inability to afford the cost of treatment. Mortality risk factors were late presentation [odds ratio (OR) 3.5, P < 0.001], dialysis eligibility (OR 3.8, P < 0.001), nondialysis (OR 23.1, P= 0.00004), primary etiology (OR 2.6, P < 0.025), and presence of > or =2 comorbidities (OR 2.9, P < 0.025); overall mortality rate was 46.2%.

CONCLUSION

These results show that many of the causes of ARF in our patients are preventable; it should be possible to reduce morbidity due to ARF through purposive preventive measures.