Management of early acute renal failure: focus on post-injury prevention

Diagnosis and incidence of acute kidney injury in a mixed paediatric intensive care unit: Retrospective analysis, 2005 and 2015

Acute kidney injury (AKI) is common in intensive care patients. While creatinine definitions for AKI have been validated, oliguria criteria are less well evaluated in children. Our study compared the validity and agreement of creatinine and oliguria criteria for diagnosing AKI in a large mixed medical, surgical and cardiac paediatric intensive care unit (PICU), and assessed the significance of their independent and combined effects on predicted mortality relative to paediatric index of mortality (PIM risk of death) on admission. Creatinine measurements during PICU admissions in 2005 and 2015 were obtained from the electronic medical record. Urine output was reviewed to identify periods of oliguria of more than eight hours. We used the PIM3 model for predicted risk of death. AKI based on creatinine rise occurred in 23.6% of the total 2203 admissions (10.0%, 8.2% and 5.6% for mild, moderate and severe categories, respectively). Oliguria occurred in 11.4% (8.4%, 1.8% and 1.2% for mild, moderate and severe categories, respectively) and overlapped only partially with creatinine criteria. Mortality relative to predicted mortality increased with increasing creatinine and oliguria severity, but was lower than predicted where oliguria occurred without creatinine rise. AKI by creatinine criteria and/or oliguria are common in the PICU, but criteria overlap only partially. Increasing severity of creatinine rise and oliguria confers increasing risk-adjusted mortality, especially for admissions with low PIM3 risk of death. The mortality of patients with AKI defined by oliguria alone is low. Defining AKI by oliguria alone has less clinical utility and may not represent true AKI.

Higher diastolic blood pressure at admission and antiedema therapy is associated with acute kidney injury in acute ischemic stroke patients

Antiedema therapy with mannitol and furosemide is widely used for prevention and management of cerebral edema, elevated intracranial pressure, and cerebral hernia. There are some reports about mannitol and furosemide as risk factors of acute kidney injury (AKI). We investigated the risk factors for AKI including antiedema therapy in acute ischemic stroke patients. The subjects were 129 patients with acute ischemic stroke including 56 females and 73 males with a mean age 68.16±12.29 years. Patients were divided into two groups: patients with AKI and without AKI according to Acute Kidney Injury Network criteria. All patients had undergone cranial, carotid, and vertebral artery evaluation with magnetic resonance imaging. The number of patients with AKI was 14 (10.9%). Subjects experiencing atrial fibrillation (P=0.043) and higher diastolic blood pressure (DBP) (P=0.032) treated with mannitol (P=0.019) and furosemide (P=0.019) disclosed significant association with AKI. Regression analysis revealed that higher DBP (P=0.029) and management with mannitol (P=0.044) were the risk factors for AKI. Higher DBP at admission is the most important risk factor for AKI. However antiedema therapy should be used carefully in patients with acute ischemic stroke. Serum creatinine levels or estimated glomerular filtration rate should be watched frequently to prevent AKI.

Acute kidney injury

Acute kidney injury (formerly known as acute renal failure) is a syndrome characterised by the rapid loss of the kidney's excretory function and is typically diagnosed by the accumulation of end products of nitrogen metabolism (urea and creatinine) or decreased urine output, or both. It is the clinical manifestation of several disorders that affect the kidney acutely. Acute kidney injury is common in hospital patients and very common in critically ill patients. In these patients, it is most often secondary to extrarenal events. How such events cause acute kidney injury is controversial. No specific therapies have emerged that can attenuate acute kidney injury or expedite recovery; thus, treatment is supportive. New diagnostic techniques (eg, renal biomarkers) might help with early diagnosis. Patients are given renal replacement therapy if acute kidney injury is severe and biochemical or volume-related, or if uraemic-toxaemia-related complications are of concern. If patients survive their illness and do not have premorbid chronic kidney disease, they typically recover to dialysis independence. However, evidence suggests that patients who have had acute kidney injury are at increased risk of subsequent chronic kidney disease.

[Volume replacement in intensive care medicine]

Volume substitution represents an essential component of intensive care medicine. The amount of fluid administered, the composition and the timing of volume replacement seem to affect the morbidity and mortality of critically ill patients. Although restrictive volume strategies bear the risk of tissue hypoperfusion and tissue hypoxia in hemodynamically unstable patients liberal strategies favour the development of avoidable hypervolemia with edema and resultant organ dysfunction. However, neither strategy has shown a consistent benefit. In order to account for the heavily varying oxygen demand of critically ill patients, a goal-directed, demand-adapted volume strategy is proposed. Using this strategy, volume replacement should be aligned to the need to restore tissue perfusion and the evidence of volume responsiveness. As the efficiency of volume resuscitation for correction of tissue hypoxia is time-dependent, preload optimization should be completed in the very first hours. Whether colloids or crystalloids are more suitable for this purpose is still controversially discussed. Nevertheless, a temporally limited use of colloids during the initial stage of tissue hypoperfusion appears to represent a strategy which uses the greater volume effect during hypovolemia while minimizing the risks for adverse reactions.

Causes of inpatient death for patients with warfare-related limb trauma and logistic regression analysis of the risk factors

OBJECTIVES

To explore the causes and risk factors of inpatient death for patients with warfare-related limb trauma.

METHODS

A retrospective study involving 339 patients with warfare-related limb trauma who were admitted to our hospital from 1998 to 2002 was conducted. Autopsy was performed for 15 cases who died in order to investigate the cause of death. Furthermore, based on the clinical features of warfare-related trauma patients, 11 factors were selected for further analysis: X1: causes of trauma, X2: shock after injury, X3: time from injury to hospital admission, X4: injured sites, X5: combined trauma (including head, thorax, abdomen, and vascular injury), X6: number of surgical procedures, X7: foreign body remaining, X8: fracture, X9: amputation, X10: duration of tourniquet homeostasis, X11: infection. All variables were available in all cases, and all parameters were quantified and fed into a computer. Multivariate statistical analysis was performed with a logistic regression model to elucidate the risk factors influencing death.

RESULTS

Fifteen of the 339 inpatient cases died (4.4%). The causes were primarily acute renal failure (ARF) (seven cases, 46.7%), pulmonary embolism (PE) (three cases, 20.0%), multiple organ system failure (MOSF) (two cases, 13.3%), and gas gangrene (three cases, 20.0%). There was one case of gas gangrene with concomitant ARF, and one of gas gangrene with MOSF. The primary risk factors influencing death included shock, amputation, and complicating infection (P < 0.05).

CONCLUSION

The primary cause of death from warfare-related limb trauma is ARF. The appropriate and prompt management of shock patients, the correct timing of amputation, and the prevention and correct handling of infection are important in reducing mortality.

Comparative analysis of urinary biomarkers for early detection of acute kidney injury following cardiopulmonary bypass

The purpose of this study was to compare the performance of six candidate urinary biomarkers, kidney injury molecule (KIM)-1, N-acetyl-beta-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL), interleukin (IL)-18, cystatin C and alpha-1 microglobulin, measured 2 h following cardiopulmonary bypass (CPB) for the early detection of acute kidney injury (AKI) in a prospective cohort of patients undergoing cardiac surgery. A total of 103 subjects were enrolled; AKI developed in 13%. Urinary KIM-1 achieved the highest area under-the-receiver-operator-characteristic curve (AUC 0.78, 95% confidence interval 0.64-0.91), followed by IL-18 and NAG. Only urinary KIM-1 remained independently associated with AKI after adjustment for a preoperative AKI prediction score (Cleveland Clinic Foundation score; p = 0.02), or CPB perfusion time (p = 0.006). In this small pilot cohort, KIM-1 performed best as an early biomarker for AKI. Larger studies are needed to explore further the role of biomarkers for early detection of AKI following cardiac surgery.

Dendritic cells facilitate accumulation of IL-17 T cells in the kidney following acute renal obstruction

Acute urinary obstruction causes interstitial inflammation with leukocyte accumulation and the secretion of soluble mediators. Here we show that unilateral ureteral ligation caused a progressive increase in renal F4/80(+) and F4/80(-) dendritic cells, monocytes, neutrophils and T-cells 24-72 h following obstruction. Depletion of dendritic cells by clodronate pretreatment showed these cells to be the most potent source of tumor necrosis factor and other pro-inflammatory mediators in the obstructed kidney. F4/80(+) dendritic cells and T-cells co-localized in the cortico-medullary junction and cortex of the obstructed kidney. Cytokine secretion patterns and surface phenotypes of T-cells from obstructed kidneys were found to include interferon-gamma-secreting CD4(+) and CD8(+) memory T-cells as well as interleukin 17 (IL-17)-secreting CD4(+) memory T-cells. Depletion of the intra-renal dendritic cells prior to ligation did not numerically reduce T-cells in obstructed kidneys but attenuated interferon-gamma and IL-17-competent T-cells. Our study shows that intra-renal dendritic cells are a previously unidentified early source of proinflammatory mediators after acute urinary obstruction and play a specific role in recruitment and activation of effector-memory T-cells including IL-17-secreting CD4(+) T-cells.

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.

Evaluation and initial management of acute kidney injury

The evaluation and initial management of patients with acute kidney injury (AKI) should include: (1) an assessment of the contributing causes of the kidney injury, (2) an assessment of the clinical course including comorbidities, (3) a careful assessment of volume status, and (4) the institution of appropriate therapeutic measures designed to reverse or prevent worsening of functional or structural kidney abnormalities. The initial assessment of patients with AKI classically includes the differentiation between prerenal, renal, and postrenal causes. The differentiation between so-called "prerenal" and "renal" causes is more difficult, especially because renal hypoperfusion may coexist with any stage of AKI. Using a modified Delphi approach, the multidisciplinary international working group, generated a set of testable research questions. Key questions included the following: Is there a difference in prognosis between volume-responsive and volume-unresponsive AKI? Are there biomarkers whose patterns (dynamic changes) predict the severity and recovery of AKI (maximal stage of AKI, need for RRT, renal recovery, mortality) and guide therapy? What is the best biomarker to assess prospectively whether AKI is volume responsive? What is the best biomarker to assess the optimal volume status in AKI patients? In evaluating the current literature and ongoing studies, it was thought that the answers to the questions posed herein would improve the understanding of AKI, and ultimately patient outcomes.

Preconditioning and protection against ischaemia-reperfusion in non-cardiac organs: a place for volatile anaesthetics?

There is an increasing body of evidence that volatile anaesthetics protect myocardium against ischaemic insult by a mechanism termed 'anaesthetic preconditioning'. Anaesthetic preconditioning and ischaemic preconditioning share several common mechanisms of action. Since ischaemic preconditioning has been demonstrated in organs other than the heart, anaesthetic preconditioning might also apply in these organs and have significant clinical applications in surgical procedures carrying a high risk of ischaemia-reperfusion injury. After a brief review on myocardial preconditioning, experimental and clinical data on preconditioning in non-cardiac tissues will be presented. Potential benefits of anaesthetic preconditioning during non-cardiac surgery will be addressed.

Acute Renal Injury and Dysfunction Following Elective Abdominal Aortic Surgery

OBJECTIVES

To evaluate the incidence of kidney injury and acute renal dysfunction (ARD) and associated risk factors in open abdominal aortic surgery.

MATERIALS AND METHODS

69 patients undergoing elective infrarenal aortic repair were included in a prospective study. Anaesthesia and haemodynamic management were standardised targeting a mean arterial pressure (MAP) of 70-90 mmHg, pulmonary artery occlusion pressure of 12-14 mmHg and cardiac index >or=2.4 l/min/m(2). Urinary albumin-creatinine and N-acetyl-B-D-glucosaminidase-creatinine ratios were measured as indicators of kidney injury. The definition of ARD was based on the RIFLE criteria.

RESULTS

Kidney injury was found in most patients. ARD developed in 22% of the patients, and acute renal failure in 4%. The patients with ARD were older, and had lower plasma creatinine and estimated GFR before surgery. ARD was associated with intraoperative hypotension (MAP <60 mmHg >15 min), low cardiac index (<2.4 l/min/m(2)), rhabdomyolysis, and early reoperation. Intraoperative hypotension and postoperative low cardiac output were independent risk factors for ARD in multivariate analysis.

CONCLUSIONS

Kidney injury occurs in most patients undergoing infrarenal aortic surgery, but only 22% develop acute renal dysfunction. Hypotension and low cardiac output are risk factors that could be avoided by optimizing perioperative management.

Combined measurements of N-terminal pro-brain natriuretic peptide and cardiac troponins in potential organ donors

OBJECTIVE

Brain death may induce cardiac dysfunction. In potential organ donors measurements of N-terminal pro-brain natriuretic peptide (NT-proBNP) and circulating cardiac troponins T and I (cTnT and cTnI), alone or in combination, are performed to investigate the accuracy of these biomarkers for early diagnosis of left ventricular systolic dysfunction.

DESIGN AND SETTING

Prospective study in a multidisciplinary intensive care unit of an university hospital.

PATIENTS

63 brain-dead patients scheduled for multiple organ harvesting.

MEASUREMENTS AND RESULTS

We measured NT-proBNP, cTnT, and cTnI and determined fractional area change (FAC) using transesophageal echocardiography. Forty-five patients had normal FAC, 9 a moderate decrease in FAC (30-50), and 9 a severe decrease in FAC (<or=30%). NT-proBNP and cTnT concentrations were significantly higher in patients with a severe decrease in FAC than in those with a moderate decrease. Combining measurements of these two biomarkers, the sensitivity of the test to predict severe decrease in FAC increased significantly to reach 1.00 compared with the sensitivities of individual measurements. The ROC curve area of combined measurements of NT-proBNP and cTnT was significantly higher than single measurements: 0.87 vs. 0.82 for NT-proBNP, 0.78 for cTnT, and 0.72 for cTnI.

CONCLUSIONS

In potential organ donors the combined measurement of NT-proBNP and cTnT concentrations is more accurate than individual measurement of NT-proBNP, cTnT, and cTnI in the early diagnosis of severe left ventricular systolic dysfunction. These findings may lead to improve the quality of cardiac care of the potential organ donors.