Body weight definitions for evaluating a urinary diagnosis of acute kidney injury in patients with sepsis

Impact of underweight status on mortality in sepsis patients: a meta-analysis

Objective

The evidence regarding the impact of underweight status on clinical outcomes in patients with sepsis are still scarce and controversial. We aimed at conducting a meta-analysis to evaluate the potential associations between underweight and the mortality rate among sepsis patients.

Methods

A comprehensive electronic search was performed in PubMed, Cochrane Library, Embase, and Web of Science databases. Odds ratios (ORs) or mean differences and 95% confidence intervals (CIs) were calculated using RevMan 5.3.

Results

A total of 58,348 patients (normal weight group: 49,084 patients; underweight group: 9,264 patients) from 23 studies were included in this meta-analysis. The results indicated that the in-hospital mortality (OR, 1.28; 95% CI, 1.21, 1.35; heterogeneity: I 2 = 21%, P = 0.21), 28-day mortality (OR, 1.54; 95% CI, 1.26, 1.88; heterogeneity: I 2 = 74%, P < 0.0001) and 1-year mortality (OR, 1.78; 95% CI, 1.58, 2.00; heterogeneity: I 2 = 41%, P = 0.17) of underweight patients were significantly higher than those of normal weight patients. However, there was no significant difference in length of hospital stay or intensive care unit length of stay between underweight patients and normal-weight patients.

Conclusion

Underweight is associated with increased mortality in patients with sepsis. Physicians should pay more attention to the management of underweight sepsis patients.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=631417, identifier CRD42025631417.

Comparison of methods to normalize urine output in critically ill patients: a multicenter cohort study

BACKGROUND

Oliguria diagnosis includes the normalization of urine output (UO) by body weight. However, the rational and the method to apply to normalize UO to body weight are unclear. We aimed to explore the impact of the method applied to normalize UO on oliguria incidence and association with outcomes.

METHODS

We included all adult patients admitted to a Swiss (derivation cohort) and a US (MIMIC-IV database, validation cohort) ICU, except those on maintenance hemodialysis, who declined consent or had < 6 consecutive UO measurements. Among a panel of candidate variables (ideal body weight, body mass index, body surface area and adjusted body weight), we identified the best predictor for UO (i.e. the variable that was most closely associated with mean UO during ICU stay). We then compared oliguria incidence and association with 90-day mortality and acute kidney disease (AKD) at hospital discharge, according to whether UO was normalized by actual body weight (ABW) or the identified best UO predictor.

RESULTS

The derivation and validation cohorts included respectively 15 322 and 28 610 patients. Those in the validation cohort were heavier (mean ABW 81 versus 75 kg) older (65 versus 62 years) and had a lower SAPS-II score (38 versus 43). The best UO predictor was ideal body weight (IBW). Oliguria incidence increased almost linearly across weight categories with ABW normalization but remained constant with IBW normalization. Using IBW for UO normalization rather than ABW improved the association between oliguria and 90-day mortality and AKD. It increased the proportion of patients correctly classified from 37.6 to 48.3% (mortality) and from 37.8 to 47% (AKD). All findings persisted after correction for sex and SAPS-II score and were confirmed in sensitivity analyses.

CONCLUSION

UO normalization by IBW lead to a stable incidence of oliguria across categories of weight and improved the association between oliguria and outcomes. IBW should be preferred to normalize UO in critically ill patients.

Adjusting Acute Kidney Injury Kidney Disease: Improving Global Outcomes Urine Output Criterion for Predicted Body Weight Improves Prediction of Hospital Mortality

BACKGROUND

Based on the Kidney Disease: Improving Global Outcomes (KDIGO) definitions, urine output, serum creatinine, and need for kidney replacement therapy are used for staging acute kidney injury (AKI). Currently, AKI staging correlates strongly with mortality and can be used as a predictive tool. However, factors associated with the development of AKI may affect its predictive ability. We tested whether adjustment for predicted (versus actual) body weight improved the ability of AKI staging to predict hospital mortality.

METHODS

A total of 3279 patients who had undergone cardiac surgery in a university hospital were retrospectively analyzed. AKI was staged according to KDIGO criteria (standard staging) and after adjustment for hourly urine output adjusted by predicted body weight for each patient and each day of their hospital stay.

RESULTS

The incidence of AKI (all stages) was 43% (predicted body weight adjusted) and 50% (standard staging), respectively ( P < .001). In sensitivity-specificity analyses for predicting hospital mortality, the area under the curve was significantly higher after adjustment for predicted body weight than with standard staging ( P = .002).

CONCLUSIONS

Compared to standard staging, adjustment of urine output for predicted body weight increases the specificity and improves prediction of hospital mortality in patients undergoing cardiac surgery.

Urine output for predicting in-hospital mortality of intensive care patients with cardiogenic shock

Background

The role of urine output (UO) in the first 24 h of admission in the clinical management of cardiogenic shock (CS) patients has not been elucidated.

Methods

This study retrospectively analyzed intensive care CS patients in the MIMIC-IV database. Binomial logistic regression analysis was conducted to evaluate whether UO was an independent risk factor for in-hospital mortality in CS patients. The performance of UO in predicting mortality was evaluated by the receiver operating characteristic (ROC) curve and compared with the Oxford Acute Severity of Illness Score (OASIS). The clinical net benefit of UO in predicting mortality was determined using the decision curve analysis (DCA). Survival analysis was performed with Kaplan-Meier curves.

Results

After adjusting for confounding factors including diuretic use and acute kidney injury (AKI), UO remained an independent risk factor for in-hospital mortality in CS patients. The areas under the ROC curves (AUCs) of UO for predicting in-hospital mortality were 0.712 (UO, ml/day) and 0.701 (UO, ml/kg/h), which were comparable to OASIS (AUC = 0.695). In terms of clinical net benefit, UO was comparable to OASIS, with different degrees of benefit at different threshold probabilities. Survival analysis showed that the risk of in-hospital death in the low-UO (≤857 ml/day) group was 3.0143 times that of the high-UO (>857 ml/day) group.

Conclusions

UO in the first 24 h of admission is an independent risk factor for in-hospital mortality in intensive care CS patients and has moderate predictive value in predicting in-hospital mortality.

Identification of an optimal threshold to define oliguria in critically ill patients: an observational study

BACKGROUND

The relevance of current consensus threshold to define oliguria has been challenged by small observational studies. We aimed to determine the optimal threshold to define oliguria in critically-ill patients.

METHODS

Cohort study including adult patients admitted within a multi-disciplinary intensive care unit between January 1st 2010 and June 15th 2020. Patients on chronic dialysis or who declined consent were excluded. We extracted hourly urinary output (UO) measurements along with patient's characteristics from electronic medical records and 90-day mortality from the Swiss national death registry. We randomly split our data into a training (80%) and a validation (20%) set. In the training set, we developed multivariable models to assess the relationship between 90-day mortality and the minimum average UO calculated over time windows of 3, 6, 12 and 24 h. Optimal thresholds were determined by visually identifying cut-off values for the minimum average UO below which predicted mortality increased substantially. We tested models' discrimination and calibration on the entire validation set as well as on a subset of patients with oliguria according to proposed thresholds.

RESULTS

Among the 15,500 patients included in this analysis (training set: 12,440, validation set: 3110), 73.0% (95% CI [72.3-73.8]) presented an episode of oliguria as defined by consensus criteria (UO < 0.5 ml/kg/h for 6 h). Our models had excellent (AUC > 85% for all time windows) discrimination and calibration. The relationship between minimum average UO and predicted 90-day mortality was nonlinear with an inflexion point at 0.2 ml/kg/h for 3 and 6 h windows and 0.3 ml/kg/h for 12 and 24 h windows. Considering a threshold of < 0.2 ml/kg/h over 6 h, the proportion of patients with an episode of oliguria decreased substantially to 24.7% (95% CI [24.0-25.4]). Contrary to consensus definition, this threshold identified a population with a higher predicted 90-day mortality.

CONCLUSIONS

The widely used cut-off for oliguria of 0.5 ml/kg/h over 6 h may be too conservative. A cut-off of 0.2 ml/kg/h over 3 or 6 h is supported by the data and should be considered in further definitions of oliguria.

The clinical use of urinary mitochondrial DNA in adult surgical critical care patients with acute kidney injury

Acute kidney injury (AKI) affects 47% of adult surgical critical care patients (ASCCPs). AKI is induced through a common oxidative stress pathway resulting in mitochondrial and tubular cell injury with increased urinary mitochondrial DNA (UmtDNA) excretion. UmtDNA is an emerging and readily sampled novel biomarker for varied surgical critical care cohorts. This review aimed to determine the clinical use of UmtDNA genes (ND1 and COX3) in AKI in ASCCPs. PubMed, MEDLINE and Web of Science databases were searched. Eligibility criteria were based on the patient/problem, intervention, comparison and outcome framework. Methodological quality of studies was assessed with the Newcastle-Ottawa Quality Assessment Scale. WebPlot Digitizer version 4.4 was used to extract UmtDNA data from graphs and UmtDNA ratios were statistically analysed with PRISM version 9.1.0 (GraphPad Software). Six human studies (n = 391) with three translational murine models (n = 112) satisfied inclusion criteria. One sample t test suggested significantly high UmtDNA-ND1 ratios in progressive/severe AKI (or delayed renal transplant graft function) to no AKI (or immediate renal transplant graft function) and increased UmtDNA-COX3 ratios approached significance. Sensitivities and specificities for UmtDNA ranged from 68% to 85% and 52% to 83.6%, respectively, comparable with new biomarkers, neutrophil gelatinase-associated lipocalin and kidney injury molecule-1. Weak correlation was observed with serum creatinine. These findings were complemented in translational murine AKI experiments with significantly elevated ND1 and COX3. From bench to clinical practice, UmtDNA appears to be a promising novel biomarker of progressive/severe AKI (or delayed graft function). Large prospective, multi-centre studies reporting standardised UmtDNA findings should clarify use of UmtDNA in ASCCP-AKI management.

Changing epidemiology of acute kidney injury in critically ill patients with COVID-19: a prospective cohort

BACKGROUND

Acute kidney injury (AKI) is common in critically ill patients with coronavirus disease-19 (COVID-19). We aimed to explore the changes in AKI epidemiology between the first and the second COVID wave in the United Kingdom (UK).

METHODS

This was an observational study of critically ill adult patients with COVID-19 in an expanded tertiary care intensive care unit (ICU) in London, UK. Baseline characteristics, organ support, COVID-19 treatments, and patient and kidney outcomes up to 90 days after discharge from hospital were compared.

RESULTS

A total of 772 patients were included in the final analysis (68% male, mean age 56 ± 13.6). Compared with wave 1, patients in wave 2 were older, had higher body mass index and clinical frailty score, but lower baseline serum creatinine and C-reactive protein (CRP). The proportion of patients receiving invasive mechanical ventilation (MV) on ICU admission was lower in wave 2 (61% vs 80%; p < 0.001). AKI incidence within 14 days of ICU admission was 76% in wave 1 and 51% in wave 2 (p < 0.001); in wave 1, 32% received KRT compared with 13% in wave 2 (p < 0.001). Patients in wave 2 had significantly lower daily cumulative fluid balance (FB) than in wave 1. Fewer patients were dialysis dependent at 90 days in wave 2 (1% vs. 4%; p < 0.001).

CONCLUSIONS

In critically ill adult patients admitted to ICU with COVID-19, the risk of AKI and receipt of KRT significantly declined in the second wave. The trend was associated with less MV, lower PEEP and lower cumulative FB.

TRIAL REGISTRATION

NCT04445259.

Urine Output Calculated Using Actual Body Weight May Result in Overestimation of Acute Kidney Injury for Obese Patients

GOAL

The derived hourly urine output (UO) indexed by body weight is one of the major criteria for the diagnosis of acute kidney injury (AKI). However, it is unclear whether actual body weight (ABW) or ideal body weight (IBW) should be used. This study aims to explore whether UO calculation based on ABW might lead to overestimation of AKI.

METHOD

AKI patients identified in the Medical Information Mart for Intensive Care III database by different components of the Kidney Disease Improving Global Outcomes guidelines and different definitions of body weight were retrospectively studied. Hospital and 90-day mortality were compared to decide whether different patient groups had the same outcome.

RESULTS

In the cohort of 14,725 patients, AKI was identified in 4,298 (29.19%) and 3,060 (20.78%) patients respectively when ABW or IBW was used (P < 0.01). Multivariate logistic regression revealed that AKI patients identified by UO calculated from ABW had similar hospital and 90-day mortality to that of patients with no evidence of AKI. Whereas AKI patients identified by serum creatinine changes, or those identified by both ABW and IBW, had twice higher the risks of hospital death and about 1.5 times higher the risks of 90-day death compared with thoese with no evidence of AKI. Results were confirmed in two separate sensitivity analyses where patients whose admission creatinine levels were within the normal reference ranges and patients identified as sepsis were studied.

CONCLUSIONS

Calculating hourly body weight normalized UO using ABW may lead to underestimation of UO and overestimation of AKI.

Fluid balance-adjusted creatinine in diagnosing acute kidney injury in the critically ill

Background

Acute kidney injury (AKI) is often diagnosed based on plasma creatinine (Cr) only. Adjustment of Cr for cumulative fluid balance due to potential dilution of Cr and subsequently missed Cr‐based diagnosis of AKI has been suggested, albeit the physiological rationale for these adjustments is questionable. Furthermore, whether these adjustments lead to a different incidence of AKI when used in conjunction with urine output (UO) criteria is unknown.

Methods

This was a post hoc analysis of the Finnish Acute Kidney Injury study. Hourly UO and daily plasma Cr were measured during the first 5 days of intensive care unit admission. Cr values were adjusted following the previously used formula and combined with the UO criteria. Resulting incidences and mortality rates were compared with the results based on unadjusted values.

Results

In total, 2044 critically ill patients were analyzed. The mean difference between the adjusted and unadjusted Cr of all 7279 observations was 5 (±15) µmol/L. Using adjusted Cr in combination with UO and renal replacement therapy criteria resulted in the diagnosis of 19 (1%) additional AKI patients. The absolute difference in the incidence was 0.9% (95% confidence interval [CI]: 0.3%‐1.6%). Mortality rates were not significantly different between the reclassified AKI patients using the full set of Kidney Disease: Improving Global Outcomes criteria.

Conclusion

Fluid balance‐adjusted Cr resulted in little change in AKI incidence, and only minor differences in mortality between patients who changed category after adjustment and those who did not. Using adjusted Cr values to diagnose AKI does not seem worthwhile in critically ill patients.

Acute kidney injury prevalence, progression and long-term outcomes in critically ill patients with COVID-19: a cohort study

BACKGROUND

There are limited data on acute kidney injury (AKI) progression and long-term outcomes in critically ill patients with coronavirus disease-19 (COVID-19). We aimed to describe the prevalence and risk factors for development of AKI, its subsequent clinical course and AKI progression, as well as renal recovery or dialysis dependence and survival in this group of patients.

METHODS

This was a retrospective observational study in an expanded tertiary care intensive care unit in London, United Kingdom. Critically ill patients admitted to ICU between 1st March 2020 and 31st July 2020 with confirmed SARS-COV2 infection were included. Analysis of baseline characteristics, organ support, COVID-19 associated therapies and their association with mortality and outcomes at 90 days was performed.

RESULTS

Of 313 patients (70% male, mean age 54.5 ± 13.9 years), 240 (76.7%) developed AKI within 14 days after ICU admission: 63 (20.1%) stage 1, 41 (13.1%) stage 2, 136 (43.5%) stage 3. 113 (36.1%) patients presented with AKI on ICU admission. Progression to AKI stage 2/3 occurred in 36%. Risk factors for AKI progression were mechanical ventilation [HR (hazard ratio) 4.11; 95% confidence interval (CI) 1.61-10.49] and positive fluid balance [HR 1.21 (95% CI 1.11-1.31)], while steroid therapy was associated with a reduction in AKI progression (HR 0.73 [95% CI 0.55-0.97]). Kidney replacement therapy (KRT) was initiated in 31.9%. AKI patients had a higher 90-day mortality than non-AKI patients (34% vs. 14%; p < 0.001). Dialysis dependence was 5% at hospital discharge and 4% at 90 days. Renal recovery was identified in 81.6% of survivors at discharge and in 90.9% at 90 days. At 3 months, 16% of all AKI survivors had chronic kidney disease (CKD); among those without renal recovery, the CKD incidence was 44%.

CONCLUSIONS

During the first COVID-19 wave, AKI was highly prevalent among severely ill COVID-19 patients with a third progressing to severe AKI requiring KRT. The risk of developing CKD was high. This study identifies factors modifying AKI progression, including a potentially protective effect of steroid therapy. Recognition of risk factors and monitoring of renal function post-discharge might help guide future practice and follow-up management strategies. Trial registration NCT04445259.

Body mass index and chronic kidney disease outcomes after acute kidney injury: a prospective matched cohort study

BACKGROUND

Acute kidney injury (AKI) and obesity are independent risk factors for chronic kidney disease (CKD). This study aimed to determine if obesity modifies risk for CKD outcomes after AKI.

METHODS

This prospective multisite cohort study followed adult survivors after hospitalization, with or without AKI. The primary outcome was a combined CKD event of incident CKD, progression of CKD and kidney failure, examined using time-to-event Cox proportional hazards models, adjusted for diabetes status, age, pre-existing CKD, cardiovascular disease status and intensive care unit admission, and stratified by study center. Body mass index (BMI) was added as an interaction term to examine effect modification by body size.

RESULTS

The cohort included 769 participants with AKI and 769 matched controls. After median follow-up of 4.3 years, among AKI survivors, the rate of the combined CKD outcome was 84.7 per1000-person-years with BMI ≥30 kg/m2, 56.4 per 1000-person-years with BMI 25-29.9 kg/m2, and 72.6 per 1000-person-years with BMI 20-24.9 kg/m2. AKI was associated with a higher risk of combined CKD outcomes; adjusted-HR 2.43 (95%CI 1.87-3.16), with no evidence that this was modified by BMI (p for interaction = 0.3). After adjustment for competing risk of death, AKI remained associated with a higher risk of the combined CKD outcome (subdistribution-HR 2.27, 95%CI 1.76-2.92) and similarly, there was no detectable effect of BMI modifying this risk.

CONCLUSIONS

In this post-hospitalization cohort, we found no evidence for obesity modifying the association between AKI and development or progression of CKD.

Prognostic Utility of KDIGO Urine Output Criteria After Cardiac Surgery

OBJECTIVES

Kidney Disease: Improving Global Outcomes (KDIGO) guidelines include assessment of creatinine and urine output to identify acute kidney injury (AKI). Whether urine output is an accurate indicator of AKI after cardiac surgery, however, is unclear. The authors' goal was to examine whether cardiac surgery patients who fulfilled criteria for AKI by KDIGO urine output criteria also demonstrated kidney injury by elevated creatinine, other kidney biomarkers, or had worse clinical outcomes.

DESIGN

Secondary analysis of prospectively collected data from a clinical trial, "6% Hydroxyethyl starch 130/0.4 in Cardiac Surgery (NCT02192502)."

SETTING

Academic, quaternary care hospital.

PARTICIPANTS

Patients undergoing elective aortic valve replacement INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: One hundred forty-one patients were classified into AKI stage by KDIGO urine output criteria within 24 hours after surgery. Kidney biomarkers (serum creatinine, urinary neutrophil gelatinase-associated lipocalin [NGAL], urinary interleukin-18 [IL-18]) and hospital and intensive care unit length of stay were analyzed across AKI stages. Urine output criteria classified four times as many patients with AKI than creatinine criteria (95 [67%] v 21 [15%]). Most patients meeting KDIGO urine output criteria for AKI postoperatively did not satisfy KDIGO creatinine criteria for AKI within one week (77 of 95 [81%]) or six-to-12 months (27 of 29 [93%]). Higher AKI stage assessed by urine output was not associated with higher NGAL, IL-18, or longer hospital or intensive care unit stays.

CONCLUSIONS

Acute kidney injury classified by KDIGO urine output criteria was not associated with other biomarkers of kidney injury or worse patient outcomes. These data suggested that KDIGO urine output criteria after cardiac surgery may overclassify AKI stage; further research is needed.

Different applications of the KDIGO criteria for AKI lead to different incidences in critically ill patients: a post hoc analysis from the prospective observational SICS-II study

BACKGROUND

Acute kidney injury (AKI) is a frequent and clinically relevant problem in critically ill patients. Various randomized controlled trials (RCT) have attempted to assess potentially beneficial treatments for AKI. Different approaches to applying the Kidney Disease Improving Global Outcomes (KDIGO) criteria for AKI make a comparison of studies difficult. The objective of this study was to assess how different approaches may impact estimates of AKI incidence and whether the association between AKI and 90-day mortality varied by the approach used.

METHODS

Consecutive acutely admitted adult intensive care patients were included in a prospective observational study. AKI was determined following the KDIGO criteria during the first 7 days of ICU admission. In this post hoc analysis, we assessed whether AKI incidence differed when applying the KDIGO criteria in 30 different possible methods, varying in (A) serum creatinine (sCr), (B) urine output (UO), and (C) the method of combining these two into an outcome, e.g., severe AKI. We assessed point estimates and 95% confidence intervals for each incidence. Univariable regression was used to assess the associations between AKI and 90-day mortality.

RESULTS

A total of 1010 patients were included. Baseline creatinine was available in 449 (44%) patients. The incidence of any AKI ranged from 28% (95%CI 25-31%) to 75% (95%CI 72-77%) depending on the approach used. Methods to estimate missing baseline sCr caused a variation in AKI incidence up to 15%. Different methods of handling UO caused a variation of up to 35%. At 90 days, 263 patients (26%) had died, and all 30 variations were associated with 90-day mortality.

CONCLUSIONS

In this cohort of critically ill patients, AKI incidence varied from 28 to 75%, depending on the method used of applying the KDIGO criteria. A tighter adherence to KDIGO definitions is warranted to decrease the heterogeneity of AKI and increase the comparability of future studies.

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.