Renal Doppler to assess renal perfusion in the critically ill: a reappraisal

Doppler renal resistivity index in horses: A systematic review

BACKGROUND

The resistivity index (RI) evaluates haemodynamic based on arterial resistance. Alterations in renal blood flow are important for the early detection of kidney damage, as perfusion might be one of the first affected aspects.

OBJECTIVES

To retrieve published studies on equine renal RI to develop a standardised method of renal ultrasonographic examination and to evaluate the current reference range for the renal RI in horses.

STUDY DESIGN

Systematic review.

METHODS

An electronic search in Science Direct, PubMed, Scopus and Web of Science databases was performed in February 2023 using the terms 'RI' OR 'resistivity index' OR 'IP' OR 'pulsatility index' AND (kidney OR renal) AND (equine OR horse) in titles, keywords and abstracts. The studies were screened for inclusion based on pre-determined criteria and data on the variables of interest were collected from included studies. The SYRCLE risk of bias tool was used to assess the methodological quality.

RESULTS

The electronic searches identified 134 studies, of which 5 were eligible for inclusion in this review. The studies had been conducted in healthy non-sedated horses through the transabdominal technique. The upper limit of normality for the renal RI was 0.58 ± 0.06 for the right kidney of untrained horses, which is considerably lower than the value of 0.70 currently used for humans, cats and dogs. There were heterogenous outcomes among the studies: two of the five demonstrated a difference between the right and left renal RI values, and one of the five showed an increased renal RI in elderly horses compared with foals and adult horses.

MAIN LIMITATIONS

Data regarding the RI in horses are still scarce.

CONCLUSIONS

Additional studies that establish a reference range for the renal RI in horses are needed and there is a need to ensure consistency of techniques.

Impact of positive end-expiratory pressure on renal resistive index in mechanical ventilated patients

PURPOSE

Growing evidence shows the complex interaction between lung and kidney in critically ill patients. The renal resistive index (RRI) is a bedside measurement of the resistance of the renal blood flow and it is correlated with kidney injury. The positive end-expiratory pressure (PEEP) level could affect the resistance of renal blood flow, so we assumed that RRI could help to monitoring the changes in renal hemodynamics at different PEEP levels. Our hypothesis was that the RRI at ICU admission could predict the risk of acute kidney injury in mechanical ventilated critically ill patients.

METHODS

We performed a prospective study including 92 patients requiring mechanical ventilation for ≥ 48 h. A RRI ≥ 0.70, was deemed as pathological. RRI was measured within 24 h from ICU admission while applying 5,10 and 15 cmH2O of PEEP in random order (PEEP trial).

RESULTS

Overall, RRI increased from 0.62 ± 0.09 at PEEP 5 to 0.66 ± 0.09 at PEEP 15 (p < 0.001). The mean RRI value during the PEEP trial was able to predict the occurrence of AKI with AUROC = 0.834 [95%CI 0.742-0.927]. Patients exhibiting a RRI ≥ 0.70 were 17/92(18%) at PEEP 5, 28/92(30%) at PEEP 10, 38/92(41%) at PEEP 15, respectively. Thirty-eight patients (41%) exhibited RRI ≥ 0.70 at least once during the PEEP trial. In these patients, AKI occurred in 55% of the cases, versus 13% remaining patients, p < 0.001.

CONCLUSIONS

RRI seems able to predict the risk of AKI in mechanical ventilated patients; further, RRI values are influenced by the PEEP level applied.

TRIAL REGISTRATION

Clinical gov NCT03969914 Registered 31 May 2019.

Elevated Renal-Resistive Index as an Indicator of Acute Kidney Injury Associated With Neonatal Extracorporeal Membrane Oxygenation

OBJECTIVE

The authors aimed to assess the relationship between elevated renal-resistive index (RRI) and acute kidney injury (AKI) related to extracorporeal membrane oxygenation (ECMO) in neonatal patients.

DESIGN

This was a retrospective study.

SETTING

The study was conducted at a teaching hospital.

PARTICIPANTS

Sixteen neonates treated with ECMO at the authors' hospital between June 2021 and December 2022 were included in this study.

INTERVENTIONS

Demographic and clinical data of patients were collected from the computer database. The RRI of patients before and during ECMO treatment was measured by bedside ultrasound. A receiver operating characteristic (ROC) curve was constructed to evaluate the diagnostic value of elevation of RRI as evidence of neonatal ECMO-related AKI. Logistic regression analysis was utilized to calculate the odds ratio (OR) with a 95% CI.

MEASUREMENTS AND MAIN RESULTS

A total of 16 patients met the inclusion criteria. For the primary outcome, the authors observed that the RRI during ECMO therapy was significantly elevated in patients with AKI compared to those without AKI. As for the secondary outcome, ROC curve analysis revealed an optimal RRI cutoff of 0.797, with an area under the curve of 0.855 (95% CI, 0.664-1, p = 0.027). The sensitivity and specificity of RRI values >0.797 for diagnosing AKI were 72.7% and 80%, respectively. Univariate logistic regression analysis indicated an OR of 1.433 (95% CI 1.192-1.873, p < 0.05) for RRI values above 0.797. This association remained statistically significant even after adjusting for serum cystatin C and Sequential Organ Failure Assessment score, with an adjusted OR of 1.352 (95% CI 1.108-1.612, p < 0.05).

CONCLUSION

The elevation of the RRI demonstrated a strong correlation with the onset of neonatal ECMO-related AKI, which may offer valuable support for diagnosing neonatal ECMO-related AKI.

Influence of arterial blood gases on the renal arterial resistive index in intensive care unit

BACKGROUND

Renal artery Doppler sonography with resistive index (RI) determination is a noninvasive, fast, and reliable diagnostic tool increasingly used in the intensive care unit (ICU) to predict and assess the reversibility of acute kidney injury (AKI). However, interpreting the RI can be challenging due to numerous influencing factors. While some studies have explored various confounding factors, arterial blood gases have received limited attention. Therefore, our study aims to evaluate the impact of arterial blood gases on the RI in the ICU setting.

METHODS

This prospective observational study enrolled ICU patients who required blood gas analysis and had not experienced significant hemodynamic changes recently. The RI was measured using standardized Doppler ultrasound within an hour of the arterial blood gases sampling and analysis.

RESULTS

A total of sixty-four patients were included in the analysis. Univariate analysis revealed a correlation between the RI and several variables, including PaCO2 (R = 0.270, p = 0.03), age (R = 0.574, p < 0.0001), diastolic arterial pressure (DAP) (R = - 0.368, p = 0.0028), and SaO2 (R = - 0.284, p = 0.0231). Multivariate analysis confirmed that age > 58 years and PaCO2 were significant factors influencing the RI, with respective odds ratios of 18.67 (p = 0.0003) and 1.132 (p = 0.0267).

CONCLUSION

The interpretation of renal arterial RI should take into account thresholds for PaCO2, age, and diastolic arterial pressure. Further studies are needed to develop a comprehensive scoring system that incorporates all these cofactors for a reliable analysis of RI levels. Trial registration This observational study, registered under number 70-0914, received approval from local Ethical Committee of Toulouse University Hospital.

Doppler ultrasound in the assessment of renal perfusion before and during continuous kidney replacement therapy in the pediatric intensive care unit

BACKGROUND

This study aimed to assess observer variability and describe renal resistive index (RRI) and pulsatility index (PI) before and after onset of continuous kidney replacement therapy (CKRT). A secondary objective was to correlate Doppler ultrasound findings with those from direct measurement of renal blood flow (RBF).

METHODS

This is a prospective observational study in hemodynamically stable Maryland piglets with and without acute kidney injury (AKI) and in hemodynamically unstable critically ill children requiring CKRT. Doppler-based RRI and PI were assessed for each subject. Measurements were made by two different operators (pediatric intensivists) before and after CKRT onset.

RESULTS

Observer variability assessment in the measurement of RRI and PI rendered a moderate correlation for both RRI (ICC 0.65, IQR 0.51-0.76) and PI (ICC 0.63, IQR 0.47-0.75). RRI and PI showed no correlation with RBF or urine output. Baseline RRI and PI were normal in control piglets [RRI 0.68 (SD 0.02), PI 1.25 (SD 0.09)] and those with AKI [RRI 0.68 (SD 0.03), PI 1.20 (SD 0.13)]. Baseline RRI and PI were elevated in critically ill children (RRI 0.85, PI 2.0). PI and RRI did not change with CKRT in any study group.

CONCLUSIONS

Observer variability between inexperienced pediatric intensivists was comparable with that between senior and junior operators. Doppler-based calculations did not correlate with invasive measurements of RBF. RRI and PI were normal in hemodynamically stable piglets with and without AKI. RRI and PI were high in hemodynamically unstable patients requiring CKRT. RRI and PI did not change after CKRT onset, despite changes in hemodynamic status. A higher resolution version of the Graphical abstract is available as Supplementary information.

Intrarenal Doppler approaches in hemodynamics: A major application in critical care

The treatment of severe cases usually requires multimodality hemodynamic monitoring approaches, particularly for tissue and organ perfusion tracking. Currently, only a few studies have investigated renal perfusion status at the bedside. Ultrasound has become increasingly utilized to guide the hemodynamic management of severe patients. Similarly, intrarenal Doppler (IRD) is widely used to assess renal perfusion from both the intrarenal artery and vein perspectives. The renal resistive index (RRI), which reflects the renal arterial blood flow profile, is often applied to predict the reversibility of renal dysfunction and to titrate hemodynamic support. Intrarenal venous flow (IRVF) patterns and the renal venous stasis index (RVSI), which reflects the intrarenal vein blood flow profile, are now being used to assess intravenous congestion. They may also be useful in predicting the risk of acute kidney injury and avoiding fluid overload. IRD can provide diverse and supplemental information on renal perfusion and may help to establish the early diagnosis in severe patients. This review focused on the specific operational methods, influencing factors, and applications of IRD in hemodynamics.

Renal replacement therapy for acute kidney injury in burn patients, an international survey and a qualitative review of current controversies

BACKGROUND OF THE STUDY

Acute kidney injury (AKI) is a common complication in critically ill burn patients and is associated with a number of serious adverse outcomes. The clinical decision-making process related to the management of AKI in burn patients is complex and has not been sufficiently standardized. The main aim of this study was to explore the diagnostic approach and clinician's attitudes toward the management of AKI and RRT in burn patients around the world.

METHODS

The questionnaire was widely distributed among the members of International Society for Burn Injury (ISBI), who were invited to complete the survey. Data collection and report was compliant with the the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) Web-survey guidelines. The survey form with multiple-choice questions was divided into 3 parts: a. physician and institutional demographics, b. AKI diagnostic information, c. technical aspects of RRT.

RESULTS

A total of 44 respondents worldwide submitted valuable data in the 2-month period. Of all respondents, 43.2% were from Europe, 30% from North America, 7% from South-East Asia 2.3% from Africa and 18.2% from other regions. 93.1% of participants declare that they use specific definitions to detect AKI, while 11.4% declare the use of renal ultrasonography for AKI diagnosis. CRRT appeared to be the most preferred option by 43.2% of participants, followed by intermittent hemodialysis (25%), and prolonged intermittent RRT (6.8%). The expertise to deliver a modality and the availability of resources were considered important factors when selecting the optimal RRT modality by 20.5% and 29.6% of respondents. The use of specific serum biomarkers for AKI diagnosis are stated by 16% of respondents; 25% of specialists refer to the use of biomarkers of AKI as a criterium for discontinuing the RRT. Femoral vena and right jugular vena were the most frequently used location for RRT temporary catheter placement, 54.6% of respondents declared using ultrasound guidance for catheter placement.

CONCLUSIONS

The majority of burn specialists use specific consensus classifications to detect acute kidney injury. Continuous renal replacement therapy appeared to be the most preferred option, while the expertise to deliver a particular modality and resources availability play a significant role in modality selection. The use of ultrasound and specific biomarkers for AKI evaluation is infrequent in routine clinical practice.

Development and validation of a clinical prediction model of acute kidney injury in intensive care unit patients at a rural tertiary teaching hospital in South Africa: a study protocol

INTRODUCTION

Acute kidney injury (AKI) is a decline in renal function lasting hours to days. The rising global incidence of AKI, and associated costs of renal replacement therapy, is a public health priority. With the only therapeutic option being supportive therapy, prevention and early diagnosis will facilitate timely interventions to prevent progression to chronic kidney disease. While many factors have been identified as predictive of AKI, none have shown adequate sensitivity or specificity on their own. Many tools have been developed in developed-country cohorts with higher rates of non-communicable disease, and few have been validated and practically implemented. The development and validation of a predictive tool incorporating clinical, biochemical and imaging parameters, as well as quantification of their impact on the development of AKI, should make timely and improved prediction of AKI possible. This study is positioned to develop and validate an AKI prediction tool in critically ill patients at a rural tertiary hospital in South Africa.

METHOD AND ANALYSIS

Critically ill patients will be followed from admission until discharge or death. Risk factors for AKI will be identified and their impact quantified using statistical modelling. Internal validation of the developed model will be done on separate patients admitted at a different time. Furthermore, patients developing AKI will be monitored for 3 months to assess renal recovery and quality of life. The study will also explore the utility of endothelial monitoring using the biomarker Syndecan-1 and capillary leak measurements in predicting persistent AKI.

ETHICS AND DISSEMINATION

The study has been approved by the Walter Sisulu University Faculty of Health Science Research Ethics and Biosafety Committee (WSU No. 005/2021), and the Eastern Cape Department of Health Research Ethics (approval number: EC 202103006). The findings will be shared with facility management, and presented at relevant conferences and seminars.

Resistivity and pulsatility indexes in feline kidney disease: a systematic review

Doppler ultrasonography is used in the evaluation of hemodynamics, and the resistivity (RI) and pulsatility (PI) indexes provide information about resistance to blood flow within a vessel. This systematic review was carried out to evaluate renal RI and PI in clinically healthy and nonsedated cats and as well as their usefulness in the evaluation of kidney disease in cats. An electronic search in the PubMed, Scopus, and Web of Science databases was carried out using the terms "resistive index" or "resistivity index" or "pulsatility index;" "Doppler;" "renal" or "kidney;" and "cat" or "feline" in titles, abstracts, and keywords. Variables of interest related to experimental model features, research methods, and technical resources were extracted from the studies. The methodological quality was assessed with SYRCLE's risk of bias tool. Thus, 14 studies involving healthy and sick cats were selected. Interestingly, the upper limits estimated for both RI and PI varied among studies. The upper limits of renal RI for healthy cats varied between 0.64 and 0.72, while for PI, the values varied from 1.06 to 1.29. A limited number of studies evaluated cats with kidney disease. In most studies, RI values of kidneys with different conditions were significantly different from kidneys of healthy animals, indicating that RI values increase with kidney disease. The parameters body weight, heart rate, and age seem to influence the RI values. Standardized studies regarding its realization and description are still necessary to define normal values and analyze its applicability in the clinical diagnostic routine.

Intraoperative evaluation of renal resistive index with transesophageal echocardiography for the assessment of acute renal injury in patients undergoing coronary artery bypass grafting surgery: A prospective observational study

Background

Acute kidney injury (AKI) is a common complication after on pump coronary artery bypass grafting (CABG) surgery and is associated with a poor prognosis. Postoperative AKI is associated with morbidity, mortality, and increase in length of intensive care unit (ICU) stay and increases the financial burden. Identifying individuals at risk for developing AKI in postoperative period is extremely important to optimize outcomes. The aim of the study is to evaluate the association between the intraoperative transesophageal echocardiography (TEE) derived renal resistive index (RRI) and AKI in patients undergoing on-pump CABG surgery.

Methods

This prospective observational study was conducted in patients more than 18 years of age undergoing elective on pump CABG surgery between July 1, 2018, and December 31, 2019, at a tertiary care center. All preoperative, intraoperative, and postoperative parameters were recorded. TEE measurement was performed in hemodynamically stable patients before the sternum was opened. Postoperative AKI was diagnosed based on the serial measurement of serum creatinine and the monitoring of urine output.

Results

A total of 115 patients were included in our study. Thirty-nine (33.91%) patients had RRI >0.7 while remaining seventy-six (66.08%) patients had RRI <0.7. AKI was diagnosed in 26% (30/115) patients. AKI rates were significantly higher in patients with RRI values exceeding 0.7 with 46.15% (18/39) compared to 15.75% (12/76) in RRI values of less than 0.7. Multivariate analysis revealed that AKI was associated with an increase in RRI and diabetes mellitus. The RRI assessed by receiver operating characteristic (ROC) curve and the area under the curve (AUC) to distinguish between non-AKI and AKI groups were 0.705 (95% CI: 0.588-0.826) for preoperative RRI. The most accurate cut-off value to distinguish non-AKI and AKI groups was a preoperative RRI of 0.68 with a sensitivity of 70% and specificity of 67%.

Conclusions

An increased intraoperative RRI is an independent predictor of AKI in the postoperative period in patients undergoing CABG surgery. The cutoff value of TEE-derived RRI in the intraoperative period should be >0.68 to predict AKI in the postoperative period.

Non-invasive Early Prediction of Septic Acute Kidney Injury by Doppler-Based Renal Resistive Indexes Combined With Echocardiographic Parameters: An Experimental Study

Non-invasive early prediction of septic acute kidney injury (S-AKI) is still urgent and challenging. Increased Doppler-based renal resistive index (RRI) has been shown to be associated with S-AKI, but its clinical use is limited, which may be explained by the complex effects of systemic circulation. Echocardiogram allows non-invasive assessment of systemic circulation, which may provide an effective supplement to RRI. To find the value of RRI combined with echocardiographic parameters in the non-invasive early prediction of S-AKI, we designed this experiment with repeated measurements of ultrasonographic parameters in the early stage of sepsis (3, 6, 12, and 24 h) in cecum ligation and puncture (CLP) rats (divided into AKI and non-AKI groups at 24 h based on serum creatinine), with sham-operated group serving as controls. Our results found that RRI alone could not effectively predict S-AKI, but when combined with echocardiographic parameters (heart rate, left ventricular end-diastolic internal diameter, and left ventricular end-systolic internal diameter), the predictive value was significantly improved, especially in the early stage of sepsis (3 h, AUC: 0.948, 95% CI 0.839–0.992, P < 0.001), and far earlier than the conventional renal function indicators (serum creatinine and blood urea nitrogen), which only significantly elevated at 24 h. Our method showed novel advances and potential in the early detection of S-AKI.

Effects of ulinastatin on renal perfusion evaluated by Doppler ultrasonography in a porcine model of septic shock

The present study aimed to evaluate the effect of ulinastatin (UTI) on renal perfusion using Doppler ultrasonography in a porcine model of septic shock induced by smoking inhalation and live methicillin-resistant Staphylococcus aureus instillation. A total of 32 healthy Landrace pigs were randomly assigned into the following four groups: Sham group (SH; n=5), septic shock group (SS; n=9), septic shock treated with vancomycin (15 mg/kg) group (VAN; n=9) and septic shock treated with UTI (50,000 U/kg) + vancomycin (UTI; n=9) group. Renal perfusion was evaluated by contrast-enhanced ultrasound (CEUS) at baseline and at the end of the protocol (24 h). The spectrum of interlobar or arcuate artery was selected to calculate the corrected resistive index (cRI). Sulphur hexafluoride microbubbles were bolus injected via a venous catheter. The peak intensity (Pi) and area under curve (AUC) were calculated using a time-intensity curve. Compared with the baseline group, cRI was increased significantly at the end of the protocol, except for that in the SH group, whereas Pi decreased significantly after injury in all experimental groups but was higher in the UTI group compared with that in the SS and VAN groups (both P<0.001). Linear correlation was found between the cardiac output (CO) and Pi (R²=0.752; P<0.001). The AUC was significantly decreased after injury in the SS and VAN groups compared with the baseline group. All parameters detected by CEUS were improved in the UTI group, and significant differences were found between the UTI and SS or VAN group (all P<0.05). In conclusion, acute renal injury, which occasionally occurs during septic shock, is accompanied with a significantly lower perfusion rate in the renal microcirculation. By contrast, UTI can significantly improve renal perfusion, which can be reliably evaluated using CEUS.

Renal Resistive Index: Not Only for Kidney Clinics

Renal Resistive Index (RRI) is a measurement of the resistance of the renal blood flow. A value higher than 0.70 is a marker of increased resistance and is correlated with kidney injury and its severity. Additionally, it may be associated with the mortality rate in the post-surgery population. In COVID-19 subjects, we found that high RRI has been associated with high levels of serum C-reactive protein, a marker of systemic inflammatory reaction syndrome. Finally, we propose RRI not only as a marker of kidney injury, but also as a tool to evaluate the course of critical illness.

Future developments in the imaging of the gastrointestinal tract: the role of ultrasound

PURPOSE OF REVIEW

The purpose of this review is to summarize the utilization and most recent developments with regard to the use of ultrasound when imaging the abdomen and gastrointestinal tract.

RECENT FINDINGS

Although the use of ultrasound to assess the anatomy of the various abdominal organs is well established within radiology and critical care, its use as part of functional and physiological assessment is still evolving. Recent developments have extended the use of ultrasound beyond standard B-mode/2D imaging techniques to incorporate more functional and haemodynamic assessment. These include the use of contrast-enhanced ultrasound (CEUS), elastography, and colour Doppler techniques.

SUMMARY

Whilst Doppler techniques are reasonably well established within critical care ultrasound (CCUS), especially in echocardiography, CEUS and elastography are less well known. CEUS utilizes a purely intravascular contrast agent whilst elastography measures the degree of deformation or stiffness in various organs. Whilst their use individually may be limited; they may play a role in a multiparametric assessment. Mirroring the overall trends in critical care ultrasound development, abdominal ultrasound assessment is best integrated in a holistic approach and adapted to the individual patient.

The furosemide stress test, electrolyte response and Renal Index in critically ill patients

BACKGROUND

Acute kidney injury (AKI) is a common syndrome in critically ill patients. The diagnostic ability of traditional markers such as serum creatinine has recently been questioned, and the use of newer tests such as the furosemide stress test or the ultrasound assessment of renal resistive index have been proposed. Aim of the present study was to compare the response to a furosemide stress test, the Renal Index in mechanically ventilated patients with and without acute kidney injury at admission, and who did or did not develop AKI at day three, among those with normal renal function at the CIU admission.

METHODS

Prospective observational study in consecutive mechanically ventilated patients admitted in a general intensive care. Furosemide stress test and ultrasonographical Renal Index were performed at the admission and clinical and laboratory data were collected before and two hours after the furosemide stress text. The urine output after the first and the second hours was recorded.

RESULTS

Forty patients were enrolled, 19 of whom had AKI at admission. The Renal Index was significantly higher in patients with AKI (0.77±0.07 vs. 0.72±0.08, P=0.027); patients with AKI had a significantly lower urine output after the furosemide stress test (400 [340; 1400] vs.1525 [400; 2550] mL; P=0.013). The plasma concentrations of sodium, potassium and chloride were not different before and after the furosemide stress test in patients with and without AKI, whereas in patients with AKI, the total urine output of sodium, potassium and chloride were significantly lower compared to patients without AKI. Similar results were found in patients without AKI at admission and who developed AKI at day three as compared to those who did not develop AKI.

CONCLUSIONS

The response to the furosemide stress test and the Renal Index could be used as additional tools to evaluate the kidney function in critically ill patients.

Renal resistive index as a predictor of postoperative complications in liver resection surgery. Observational study

Mortality after liver surgery reduced during the last three decades to less than 2%, but post-operative morbidity occurs in 20-50% of cases. Patients are often considered eligible for post-operative intensive-care unit (ICU) admission. Predicting which patients that are at higher risk could lead to a more precise perioperative management. We investigated whether renal resistive index (RRI), alone or along with other items, can predict post-operative complication after hepatic resection. All consecutive patients undergoing hepatectomy for primary or metastatic neoplasm at our Institution between February 2015 and March 2017 were enrolled. They received RRI measurement before entering in operative room and after awakening from general anesthesia. 183 Patients were enrolled. High surgical invasiveness, surgery time > 360 min, pre-operative RRI and postoperative serum lactate clearance <  - 6%, showed to be associated with postoperative complications. Pre-operative RRI, complex liver resection, long-lasting surgery and poor lactate clearance (cLac) close to awakening from general anesthesia, all together may permit to classify the risk of post-operative adverse outcome after hepatic resection surgery.

Feasibility of renal resistive index measurements performed by an intermediate and novice sonographer in a volunteer population

Background

The Doppler-derived renal resistive index (RRI) is emerging as a promising bedside tool for assessing renal perfusion and risk of developing acute kidney injury in critically ill patients. It is not known what level of ultrasonography competence is needed to obtain reliable RRI values.

Objective

The aim of this study was to evaluate the feasibility of RRI measurements by an intermediate and novice sonographer in a volunteer population.

Methods

After a focused teaching session, an intermediate (resident), novice (medical student) and expert sonographer performed RRI measurements in 23 volunteers consecutively and blinded to the results of one another. Intraclass correlation coefficients and Bland–Altman plots were used to evaluate interobserver reliability, bias and precision.

Results

Both non-experts were able to obtain RRI values in all volunteers. Median RRI in the population measured by the expert was 0.58 (interquartile range 0.52–0.62). The intraclass correlation coefficient was 0.96 (95% confidence interval 0.90–0.98) for the intermediate and expert, and 0.85 (95% confidence interval 0.69–0.94) for the novice and expert. In relation to the measurements of the expert, both non-experts showed negligible bias (mean difference 0.002 [95% confidence interval − 0.005 to 0.009, p = 0.597] between intermediate and expert, mean difference 0.002 [95% confidence interval − 0.011 to 0.015, p = 0.752] between novice and expert) and clinically acceptable precision (95% limits of agreement − 0.031 to 0.035 for the intermediate, 95% limits of agreement − 0.056 to 0.060 for the novice).

Conclusions

RRI measurements by both an intermediate and novice sonographer in a volunteer population were reliable, accurate and precise after a brief course. RRI is easy to learn and feasible within the scope of point-of-care ultrasound.

Early Recognition of Persistent Acute Kidney Injury

Despite the vast amount of literature dedicated to acute kidney injury (AKI) and its clinical consequences, short-term renal recovery has been relatively neglected. Recent studies have suggested that timing of renal recovery is associated with longer-term risk of death, residual renal function, and end-stage renal failure risk. In addition, longer AKI duration is associated with an increased requirement for renal replacement therapy. Comorbidities, especially renal and cardiovascular, severity of AKI, criteria to reach AKI diagnosis, as well as severity of critical illness have been associated with longer AKI duration, and, more specifically, risk of persistent renal dysfunction. Because predicting short-term renal recovery is clinically relevant, several tests, imaging, and biomarkers have been tested in a way to predict the course of AKI and chances for early renal recovery. In this review, the definition of recovery, consequences of persistent AKI, and tools proposed to predict recovery are described. The performance of these tools and their limits are discussed.

Whole body ultrasound in the operating room and intensive care unit

Whole body ultrasound can be used to improve the speed and accuracy of evaluation of an increasing number of organ systems in the critically ill. Cardiac and abdominal ultrasound can be used to identify the mechanisms and etiology of hemodynamic instability. In hypoxemia or hypercarbia, lung ultrasound can rapidly identify the etiology of the condition with an accuracy that is equivalent to that of computed tomography. For encephalopathy, ocular ultrasound and transcranial Doppler can identify elevated intracranial pressure and midline shift. Renal and bladder ultrasound can identify the mechanisms and etiology of renal failure. Ultrasound can also improve the accuracy and safety of percutaneous procedures and should be currently used routinely for central vein catheterization and percutaneous tracheostomy.

Performance of Doppler-based resistive index and semi-quantitative renal perfusion in predicting persistent AKI: results of a prospective multicenter study

PURPOSE

The Doppler-based resistive index (RI) and semi-quantitative evaluation of renal perfusion using color Doppler (SQP) have shown promising results for predicting persistent acute kidney injury (AKI) in preliminary studies. This study aimed at evaluating the performance of RI and SQP to predict short-term renal prognosis in critically ill patients.

METHODS

Prospective multicenter cohort study including unselected critically ill patients. Renal Doppler was performed at admission to the intensive care unit. The diagnostic performance of RI and SQP to predict persistent AKI at day 3 was evaluated.

RESULTS

Overall, 371 patients were included, of whom 351 could be assessed for short-term renal recovery. Two thirds of the included patients had AKI (n = 233; 66.3%), of whom 136 had persistent AKI (58.4%). Doppler-based RI was higher and SQP lower in AKI patients and according to AKI recovery. Overall performance in predicting persistent AKI was however poor with area under ROC curve of respectively 0.58 (95% CI 0.52-0.64) and 0.59 (95% CI 0.54-0.65) for RI and SQP. Optimal cutoff was respectively 0.71 and 2 for RI and SQP. At optimal cutoff, sensitivity and specificity were 50% (95% CI 41-58%) and 68% (62-74%) for RI and 39% (32-45%) and 75% (66-82%) for SQP.

CONCLUSION

Although statistically associated with AKI occurrence, RI and SQP perform poorly in predicting persistent AKI at day 3. Further studies are needed to adequately describe factors influencing Doppler-based assessment of renal perfusion and to delineate whether these indicators may be useful at the bedside. CLINICALTRIAL.GOV: NCT02355314.

Terlipressin-induced modifications of Doppler ultrasound signals of systemic arteries in preterm infants with vasoactive-resistant patent ductus arteriosus: A pilot study

PURPOSE

To study the effects of terlipressin (TP) infusion on systemic perfusion, estimated with pulsed-wave Doppler ultrasonography of systemic arteries, in a population of extremely low birth-weight (ELBW) preterm infants with vasoactive-resistant ductus arteriosus.

METHODS

This prospective, observational cohort included, during five years, 12 ELBW infants with hemodynamically significant patent ductus arteriosus and absent or reversed diastolic flow at Doppler ultrasonography of systemic arteries, despite treatment and high-dose vasoactive support. We measured flow velocity of the anterior cerebral, right renal, and superior mesenteric arteries before and after TP infusion. Changes were evaluated by Spearman's rho coefficient analysis, Wilcoxon signed-rank, and Friedman test.

RESULTS

Time-averaged mean velocity of the renal artery (P = .028) increased, while renal pulsatility (P = .010) and resistance (P = .004) indexes, and cerebral artery resistance index (P = .021) decreased after TP infusion. Time-averaged mean velocity of the anterior cerebral artery proportionately increased with dopamine dose (rho = 0.678; P = .015), but showed opposite shifts after TP (rho = -0.662; P = .024).

CONCLUSIONS

These changes suggest that TP may improve systemic perfusion in the ELBW infants with vasoactive-resistant ductus arteriosus.

Can Renal Resistive Index Predict Acute Kidney Injury After Acute Type A Aortic Dissection Repair?

BACKGROUND

This study sought to determine whether assessment of the renal resistive index (RRI) can predict the short-term reversibility of acute kidney injury (AKI) after repair of acute type A aortic dissection (TAAD).

METHODS

This prospective study included 62 patients undergoing repair of acute TAAD. Doppler-based RRIs were obtained preoperatively, immediately after the surgical procedure, and 6, 24, and 48 hours postoperatively. The occurrence of AKI was evaluated daily according to Acute Kidney Injury Network criteria. Persistent AKI was defined as AKI lasting longer than 3 days. The association between the maximum RRI level at different time points and persistent AKI was analyzed by the receiver-operating characteristic curve.

RESULTS

Of the 62 patients, 22 (35.5%) had no AKI, 21 (33.9%) had transient AKI, and 19 (30.6%) had persistent AKI. The maximum RRI was 0.67 ± 0.03 (0.62 to 0.71), 0.71 ± 0.05 (0.59 to 0.79), and 0.78 ± 0.05 (0.70 to 0.92) in the no AKI, transient AKI, and persistent AKI groups, respectively. The maximum level of RRI was significantly correlated with that of SCr during the first 48 hours postoperatively (rho = 0.606; p < 0.001). RRI could predict persistent AKI with an area under the receiver-operating characteristic curve of 0.918 (95% confidence interval, 0.850 to 0.986; p < 0.001). A postoperative RRI of 0.725 or higher was a marker for early detection of persistent AKI with high sensitivity and specificity (94.7% and 72.1%, respectively).

CONCLUSIONS

An elevated maximum RRI may be a predictor of persistent AKI after repair of acute TAAD. This is helpful for management decision making and improving the prognosis of patients with AKI.

Diagnostic work-up and specific causes of acute kidney injury

Acute kidney injury (AKI) is common in critically ill patients and associated with grim short- and long-term outcome. Although in the vast majority of cases AKI is multifactorial, with sepsis, shock and nephrotoxicity accounting for most episodes, specific causes of AKI are not uncommon. Despite remaining uncertainties regarding their prevalence in the ICU, prompt recognition of specific aetiologies of AKI is likely to ensure timely management, limit worsening of renal dysfunction, and ultimately limit renal and systemic consequences of AKI. The ability to recognize conditions that may be associated with specific aetiologies and the appropriate use of clinical imaging, biological and immunological tests, along with optimal assessment of the need for renal biopsies, should be part of routine ICU care. In this review, we summarize uncertainties, current knowledge and recent advances regarding specific types of AKI. We describe the most common specific causes as well as rare aetiologies requiring urgent management, and outline available tools that may be used during the diagnostic work-up along with their limitations.

Renal Doppler and Novel Biomarkers to Assess Acute Kidney Injury in a Swine Model of Ventricular Fibrillation Cardiac Arrest

Background:

Majority of the research on cardiac arrest (CA) have focused on post-CA brain injury and myocardial dysfunction, the renal dysfunction and acute kidney injury (AKI) in other critical illnesses after CA have not been well described. This study was designed to assess AKI with renal Doppler and novel AKI biomarkers in a swine model of ventricular fibrillation cardiac arrest (VFCA).

Methods:

Thirty healthy piglets were divided into VFCA group (n = 22) and Sham group (n = 8) in a blinded manner. Mean arterial pressure, heart rate, and cardiac output were recorded continuously. Cardiac arrest (CA) was induced by programmed electric stimulation in the VFCA group, and then cardiopulmonary resuscitation was performed. Twenty piglets returned of spontaneous circulation (ROSC) and received intensive care. Blood and urine samples were collected for AKI biomarkers testing, and Color Doppler flow imaging was performed at baseline, 6 h, 12 h, and 24 h, respectively after ROSC. At ROSC 24 h, the animals were sacrificed and a semi-quantitative evaluation of pathologic kidney injury was performed.

Results:

In the VFCA group, corrected resistive index (cRI) increased from 0.47 ± 0.03 to 0.64 ± 0.06, and pulsatility index (PI) decreased from 0.82 ± 0.03 to 0.68 ± 0.04 after ROSC. Cystatin C (CysC) in both serum and urine samples increased at ROSC 6 h, but neutrophil gelatinase-associated lipocalin (NGAL) in serum increased to 5.34 ± 1.68 ng/ml at ROSC 6 h, and then decreased to 3.16 ± 0.69 ng/ml at ROSC 24 h while CysC increasing constantly. According to the renal histopathology, 18 of 20 animals suffered from kidney injury. The grade of renal injury was highly correlated with RI, cRI, NGAL, and CysC. Linear regression equation was established: Grade of renal injury = 0.002 × serum CysC + 6.489 × PI + 4.544 × cRI – 8.358 (r² = 0.698, F = 18.506, P < 0.001).

Conclusions:

AKI is common in post-CA syndrome. Renal Doppler and novel AKI biomarkers in serum and urine are of significant importance as early predictors of post-CA AKI.

Acute kidney injury in the perioperative period and in intensive care units (excluding renal replacement therapies)

Acute kidney injury (AKI) is a syndrome that has progressed a great deal over the last 20 years. The decrease in urine output and the increase in classical renal biomarkers, such as blood urea nitrogen and serum creatinine, have largely been used as surrogate markers for decreased glomerular filtration rate (GFR), which defines AKI. However, using such markers of GFR as criteria for diagnosing AKI has several limits including the difficult diagnosis of non-organic AKI, also called "functional renal insufficiency" or "pre-renal insufficiency". This situation is characterized by an oliguria and an increase in creatininemia as a consequence of a reduction in renal blood flow related to systemic haemodynamic abnormalities. In this situation, "renal insufficiency" seems rather inappropriate as kidney function is not impaired. On the contrary, the kidney delivers an appropriate response aiming to recover optimal systemic physiological haemodynamic conditions. Considering the kidney as insufficient is erroneous because this suggests that it does not work correctly, whereas the opposite is occurring, because the kidney is healthy even in a threatening situation. With current definitions of AKI, normalization of volaemia is needed before defining AKI in order to avoid this pitfall.

The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association?

Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care.

Doppler ultrasound measurement of resistance index in the diagnosis of prostate cancer

Prostate cancer (PCa) remains the second leading cause of cancer diagnosis worldwide. Early diagnosis and treatment of PCa is critical since the long-term prognosis is excellent in patients with tumors confined to the prostate gland. The current meta-analysis investigates the diagnostic value of resistive index (RI) measurement using color Doppler ultrasound in patients with PCa. Electronic literature databases were exhaustively searched for relevant studies published prior to May 31, 2014. Nine studies met our predetermined inclusion criteria for the present meta-analysis. The methodologic quality of the selected studies was independently assessed by 2 reviewers based on Quality Assessment of Diagnostic Accuracy Studies tool. Our meta-analysis results showed that RI values were significantly higher in malignant prostate tissues compared to normal prostate tissues (standardized mean difference [SMD] 0.42, 95% confidence interval [CI] 0.12~0.73, p = 0.007) and benign prostate tissues (SMD 0.41, 95% CI 0.26~0.56, p<0.001). Subgroup analysis based on the diagnostic instruments used revealed that RI values were accurate in diagnosis of PCa when compared between malignant tissue vs normal tissue and malignant tissue vs benign tissue (all p<0.05). Taken together, our findings support the potential clinical applications of RI values in diagnosis of PCa.

Doppler-based renal resistive index for prediction of renal dysfunction reversibility: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Doppler-based renal resistive index (RI) might help in distinguishing transient from persistent acute kidney injury (AKI). The main objective of these systematic review and meta-analysis was to investigate the diagnostic performance of RI in predicting short-term reversibility of AKI.

STUDY DESIGN

A systematic review of the literature was performed. Relevant studies were identified in Pubmed and Cochrane databases covering the years 1985 to 2013 and reviewed independently by 3 authors. Renal transplant recipients were excluded from this analysis. The summary estimates were computed using a random-effects model based on the DerSimonian and Lair meta-analytic method.

RESULTS

Among the 154 unique articles identified, 9 studies were included. Of the 176 patients in these studies with elevated RI or pulsatility index, 146 (83%) had a persistent AKI vs 44 (16%) of the 273 patients with normal values. Elevated RI or pulsatility index was associated with an increased risk of persistent AKI (odds ratio, 29.85; 95% confidence interval [CI], 8.73-102.16; P < .00001) with significant heterogeneity (I(2) = 75.0%, P < .0001). The pooled sensitivity and specificity were 0.83 (95% CI, 0.77-0.88) and 0.84 (95% CI, 0.79-0.88). The summary positive and negative likelihood ratios were 4.9 (95% CI, 2.44-9.87) and 0.21 (95% CI, 0.11-0.41).

CONCLUSION

These results suggest that an elevated RI may be a predictor of persistent AKI in critically ill patients. Further studies are warranted, however, to clarify the exact test performance given the marked heterogeneity among the included studies.

Bedside Doppler ultrasound for the assessment of renal perfusion in the ICU: advantages and limitations of the available techniques

Three Doppler-derived techniques have been proposed to assess renal perfusion at bedside: Doppler-based renal resistive index (RI) which has been extensively but imperfectly studied in assessing renal allograft status and changes in renal perfusion in critically ill patients and for predicting the reversibility of an acute kidney injury (AKI), semi-quantitative evaluation of renal perfusion using colour-Doppler which may be easier to perform and may give similar information than RI and contrast-enhanced sonography that may allow more precise renal and cortical perfusion assessment. These promising tools have several obvious advantages including their feasibility, non-invasiveness, repeatability and potential interest in assessing renal function or perfusion. However, several limits need to be taken into account with these techniques, and promising results remain associated with large areas of uncertainty. This editorial will describe more carefully advantages and limits of these techniques and will discuss their potential interest in assessing renal perfusion.

Berberine ameliorates renal interstitial fibrosis induced by unilateral ureteral obstruction in rats

AIM

To investigate the potential effects of berberine on renal interstitial fibrosis (RIF) of obstructed kidneys in a unilateral ureteral obstruction (UUO) rat model.

METHODS

Forty-eight rats were randomly divided into three groups: sham-operated, vehicle-treated UUO, and berberine-treated UUO. Rats were gavaged with berberine (200 mg/kg per day) or vehicle. Eight randomly chosen rats in each group were kiled and specimens were collected at day 14 after UUO. Physiological parameters and histological changes were assessed, RIF was evaluated using Masson's trichrome and Sirius red staining, oxidative stress and inflammation markers were determined, transforming growth factor β1 (TGF-β1), phosphorylated Smad3 (pSmad3) and α-smooth muscle actin (α-SMA) were measured using immunohistochemistry or western blotting analysis. The obstruction was relieved at day 14 by percutaneous nephrostomy in the remaining UUO rats. The resistive index of left kidneys was undertaken by coloured Doppler flow imaging at day 14 before nephrostomy and day 7 after the relief.

RESULTS

Berberine treatment significantly attenuated RIF induced by UUO. The UUO-induced reduction in kidney superoxide dismutase and catalase activities increased, whereas elevated kidney malondialdehyde level markedly decreased. Berberine treatment significantly ameliorated UUO-induced inflammation, and decreased TGF-β1, pSmad3 and α-SMA expression of UUO kidneys. Moreover, berberine treatment significantly suppressed the increase of resistive index compared with UUO group at day 14 after UUO as well as day 7 after the relief of obstruction.

CONCLUSION

Berberine treatment ameliorates RIF in a UUO rat model by inhibition of oxidative stress, inflammatory responses, and TGF-β1/pSmad3 signalling.

Increased cardiac index attenuates septic acute kidney injury: a prospective observational study

Background

The relationship between cardiac output and septic acute kidney injury (AKI) remains unclear. The purpose of this study was to assess the association between the cardiac index (CI) and the renal outcomes in patients with septic shock.

Methods

A one-year prospective cohort study was performed in the surgical and medical ICU of a teaching hospital in Nanjing, China. Twenty-nine septic shock patients who required early goal-directed fluid resuscitation were consecutively included. Pulse indicator continuous cardiac output (PiCCO) device was used to measure hemodynamic parameters before and after early goal-directed therapy (EGDT). Based on CI changes after EGDT, patients were assign to the CI increased group or the CI constant group, respectively. The incidence of poor renal outcome, which was defined as AKI on admission without recovery in following three days or new onset AKI within 28 days, was recorded. We investigated whether an increased CI was associated with a better renal outcome.

Results

After EGDT, there were 16 patients in the CI increased group and 13 patients in the CI constant group. The incidence of poor renal outcome was lower in CI increased group than in the CI constant group (6% vs. 62%; P = 0.003) with a relative risk of 0.10. The logistic regression showed that the CI percent change was associated with renal outcome, with an odd ratio of 0.003 (P = 0.056) after adjustment of possible confounding factors. The CI percent change would predict a good renal outcome (AU ROC 0.739, P = 0.012) with moderate accuracy (sensitivity 75% and specificity 89%) when using a 10% cut-off value from Youden index. The CI percent change was also positively correlated with creatinine clearance (CCr) after EGDT (ρ = 0.548; P = 0.002).

Conclusions

The increased CI after EGDT was a protective factor for kidney in patients with septic shock. A CI increased above 10% could be potentially used to predict development and reversibility of AKI in septic shock patients.

Trial registration

Clinicaltrials.gov:NCT01862588 (May 13, 2013).

Duplex scanning has a limited role in the evaluation of patients with renal failure

OBJECTIVE

Although common indications for renal duplex scanning (RDS) include hypertension (HT) and renal failure (RF), the role of RDS in the evaluation of patients with RF is not known. The goal of this study was to define ultrasound findings with predictive or discriminatory value in patients with RF and to identify patients undergoing a renal artery intervention as a result of RDS findings.

METHODS

We conducted a retrospective review of 214 consecutive patients referred to an Intersocietal Accreditation Commission-accredited vascular laboratory for an initial RDS from January 1, 2010, to June 30, 2010. RDS included direct ultrasound evaluation of the main renal vessels and renal parenchyma. Significant renal artery stenosis of ≥ 60% diameter reduction was indicated by a renal/aortic velocity ratio ≥ 3.5 and abnormally increased parenchymal resistance by an end-diastolic ratio ≤ 0.3.

RESULTS

We separated the patients into two groups by indication for RDS: Group I (HT alone, n = 102) and group II (RF alone or with HT, n = 112). When group I was compared with group II, there were significant differences in gender (50% vs 67% male; P = .013), age (50.9 ± 18.5 vs 60.0 ± 14.8 years; P < .001), mean arterial pressure (103.1 ± 18.8 vs 85.7 ± 17.0 mm Hg; P < .001), and creatinine (0.95 ± 0.35 vs 2.25 ± 1.07 mg/dL; P < .001). In group I patients, 86 (84.3%) had normal parenchymal resistance, whereas in group II patients, 68 (60.7%) had abnormally increased parenchymal resistance unilaterally or bilaterally (P < .001). Unilateral or bilateral renal artery stenosis was identified in six group I patients and in three group II patients (P = .315). Evaluation of group II patients revealed a diagnosis of decompensated congestive heart failure (CHF) and the presence of unilateral or bilateral increased parenchymal resistance in 27 of 68 (39.7%) vs nine of 44 (20.4%) with CHF and normal parenchymal resistance. One renal artery angioplasty was performed in a patient with unilateral renal artery stenosis and fibromuscular dysplasia.

CONCLUSIONS

Renal artery stenosis is extremely uncommon in patients undergoing RDS for RF, indicating that ischemic nephropathy is rarely a cause of RF in these patients. Abnormally increased renal parenchymal resistance is frequently found in patients being evaluated for RF and is associated with increasing creatinine and age. A diagnosis of CHF is also more common in patients with increased parenchymal resistance. Although patients who undergo RDS for RF rarely require renal artery interventions, ultrasound indices of parenchymal resistance may serve as a marker for renal disease and cardiovascular morbidity. Further studies are required to determine the prognostic significance of these ultrasound findings in the setting of RF.

The small fibrinopeptide Bβ15-42 as renoprotective agent preserving the endothelial and vascular integrity in early ischemia reperfusion injury in the mouse kidney

Disruption of the renal endothelial integrity is pivotal for the development of a vascular leak, tissue edema and consequently acute kidney injury. Kidney ischemia amplifies endothelial activation and up-regulation of pro-inflammatory mechanisms. After restoring a sufficient blood flow, the kidney is damaged through complex pathomechanisms that are classically referred to as ischemia and reperfusion injury, where the disruption of the inter-endothelial connections seems to be a crucial step in this pathomechanism. Focusing on the molecular cell-cell interaction, the fibrinopeptide Bβ_15–42 prevents vascular leakage by stabilizing these inter-endothelial junctions. The peptide associates with vascular endothelial-cadherin, thus preventing early kidney dysfunction by preserving blood perfusion efficacy, edema formation and thus organ dysfunction. We intended to demonstrate the early therapeutic benefit of intravenously administered Bβ_15–42 in a mouse model of renal ischemia and reperfusion. After 30 minutes of ischemia, the fibrinopeptide Bβ_15–42 was administered intravenously before reperfusion was commenced for 1 and 3 hours. We show that Bβ_15–42 alleviates early functional and morphological kidney damage as soon as 1 h and 3 h after ischemia and reperfusion. Mice treated with Bβ_15–42 displayed a significantly reduced loss of VE-cadherin, indicating a conserved endothelial barrier leading to less neutrophil infiltration which in turn resulted in significantly reduced structural renal damage. The significant reduction in tissue and serum neutrophil gelatinase-associated lipocalin levels reinforced our findings. Moreover, renal perfusion analysis by color duplex sonography revealed that Bβ_15–42 treatment preserved resistive indices and even improved blood velocity. Our data demonstrate the efficacy of early therapeutic intervention using the fibrinopeptide Bβ_15–42 in the treatment of acute kidney injury resulting from ischemia and reperfusion. In this context Bβ_15–42 may act as a potent renoprotective agent by preserving the endothelial and vascular integrity.

Year in review 2012: Critical Care--Nephrology

We summarize original research in the field of critical care nephrology accepted or published in 2012 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Three main topics have been identified for a rapid overview: acute kidney injury, detailed in some pathogenetic and epidemiological aspects; fluid overload as a predictor of mortality both in acute kidney injury and renal replacement therapy (RRT) patients; and RRT, evaluating some features of citrate anticoagulation and describing the effects of RRT modalities or timing on survival.