Precursors to oliguria during major burn resuscitation: An analysis of a prospective observational trial at 5 major US burn centers.

Currently, urine output is the leading variable used to tailor fluid resuscitation in patients with large TBSA burns. However, this metric often lags with respect to resuscitation. Our group sought to identify derangements in variables that precede development of oliguria (<30 cc/hr) that we hypothesize will aid in more efficient resuscitation. We performed a retrospective analysis of 146 adult patients admitted within 4 h of a large TBSA (>20%) burn. We then divided them into two cohorts: those who developed oliguria within 6 h of admission and those who did not. Patients who experienced early oliguria had a higher incidence of invasive SBP < 90 (p = 0.02) or DBP < 40 (p = 0.009), lower minimum bicarbonate level (p = 0.04), more full thickness burns (p = 0.004), and higher TBSA (p = 0.01). More female patients were found in the oliguric group (p = 0.003). Multivariate analysis was used to develop a model to predict development of oliguria. When evaluated together, minimum DBP, sex, TBSA (or percent full thickness burn), and maximum base deficit constituted the most parsimonious model that significantly predicted oliguria (AUC = 0.92). Interestingly, the model lost significance when DBP was omitted, highlighting the importance of diastolic pressure in the development of oliguria.

Clinicopathological characteristics and predictors of outcome of rapidly progressive glomerulonephritis: a retrospective study.

BACKGROUND: Globally, there are regional and time-based variations in the prevalence, etiology, and prognosis of rapidly progressive glomerulonephritis (RPGN). Prognosis of RPGN is poor, with a higher risk of death and end stage renal disease (ESRD) even with immunosuppressive medications. In the Middle East and North Africa, the studies on this disease are very limited. Therefore, we determined the predictors of outcome of RPGN. METHODS: We retrospectively assessed 101 adult patients over age of 18, diagnosed with RPGN based on renal biopsy illustrating crescents in ≥ 50% of the glomeruli. Patients who had crescents in their renal biopsies that were < 50% and those who refused to consent to a renal biopsy were excluded. We categorized the patients into 3 groups based on immunohistochemistry; type I, type II and type III. Then, depending on renal loss, we divided them into ESRD and non-ESRD groups. The clinical history and physical examination were retrieved. Additionally, 24-hour urine protein, urine analysis, renal function tests, serum albumin, complete blood count, antinuclear antibodies, anti-double stranded DNA antibodies, ANCA antibodies and serum complement levels were checked. Each patient underwent a kidney biopsy for immunohistochemistry and light microscopy. The percentage of crescentic glomeruli, number of sclerosed glomeruli, tertiary lymphoid organ (TLO), neutrophil infiltration, endocapillary or mesangial hypercellularity, interstitial fibrosis with tubular atrophy (IFTA) were analyzed. Primary outcomes (remission, ESRD and mortality) and secondary outcomes were assessed. RESULTS: Type II was the most frequent cause of RPGN (47.5%), followed by type III (32.7%) and type I (19.8%). 32 patients (31.7%) died during follow up, whereas 60 patients (59.4%) developed ESRD. In 41 patients (40.6%), remission occurred. Oliguria, serum creatinine, and need for HD at presentation were significantly increased in ESRD group compared to non-ESRD group (P < 0.001 for each). Mesangial proliferation, IFTA, TLO formation, sclerotic glomeruli and fibrous crescents were also significantly increased in ESRD group in comparison to non-ESRD group (P < 0.001 for each). Glomerulosclerosis (P = 0.036), and IFTA (P = 0.008) were predictors of ESRD. Infections (P = 0.02), respiratory failure (P < 0.001), and heart failure (P = 0.004) were mortality risk factors. CONCLUSION: Type II RPGN was the most common. Infection was the most frequent secondary outcome. Oliguria, glomerulosclerosis, the requirement for hemodialysis at presentation, IFTA and TLO formation were predictors of ESRD. Respiratory failure, heart failure and infections were significant predictors of mortality.

Spontaneous rupture of bladder diverticulum with pseudo renal failure:A case report and literature review.

BACKGROUND: Spontaneous or non-traumatic bladder rupture is rare but can be life-threatening. Bladder rupture caused by a diverticulum is extremely rare, with only a few case reports in medical literature. CASE PRESENTATION: We report the case of a 32-year-old woman admitted to hospital complaints of abdominal pain, oliguria and ascites with no history of trauma. Laboratory tests revealed an elevated serum urea nitrogen(UN) level of 33.5 mmol/l and an elevated creatinine levels of 528 umol/l. X-ray cystography confirmed the rupture of a bladder diverticulum. Subsequent transurethral catheterization led to a prompt increase in urinary output, and serum creatinine level returned to 40 umol/l within 48 h. The patient was successfully treated with laparoscopic diverticulectomy. CONCLUSION: Clinicians should maintain a high level of suspicion for urinary bladder rupture in cases presenting with acute lower abdominal pain, urinary difficulties, and oliguria. When acute renal failure, complicated ascites, and an elevated peritoneal fluid creatinine or potassium level exceeding serum levels are observed, intraperitoneal urine leakage should be suspected without delay. This case emphasizes the importance of early diagnosis and intervention in managing this rare but serious condition.

Initial lactate levels linked to oliguria in term neonates with perinatal asphyxia.

BACKGROUND: Oliguria is a sign of impaired kidney function and has been shown to be an early predictor of adverse prognoses in patients with acute kidney injury. The relationship between urine output (UOP) and early lactate levels in neonates with perinatal asphyxia (PA) has not been extensively explored. This study aimed to investigate the link between oliguria during the first 24 h of life and early lactate levels in neonates with PA. METHODS: The medical records of 293 term neonates with asphyxia from 9216 hospitalized newborns were retrospectively analyzed, including 127 cases designated as the oliguria group and 166 cases as controls. Peripheral arterial blood gas after PA and UOP within 24 h after birth were analyzed. Logistic regression analyses and receiver operating characteristic curve analysis were conducted. RESULTS: Oliguria occurred in 43.34% of neonates with PA. The median UOP of the oliguria and control groups were 0.65 and 1.46 mL/kg/h, respectively. Elevated lactate levels after PA are an independent risk factor for oliguria in the following 24 h (p = 0.01; OR: 1.19; 95%CI: 1.04-1.35) and show a moderate discriminatory power for oliguria (AUC = 0.62). Using a cut off value of 8.15 mmol/L, the positive and negative predictive values and the specificity were 59.34%, 63.86%, and 78.30%, respectively. CONCLUSION: Neonates with elevated lactate levels after PA face a risk of oliguria in the following 24 h. Based on early elevated lactate levels after resuscitation, especially ≥ 8.15 mmol/L, meticulously monitoring UOP will allow this vulnerable population to receive early, tailored fluid management and medical intervention.

Machine-learning model for predicting oliguria in critically ill patients.

This retrospective cohort study aimed to develop and evaluate a machine-learning algorithm for predicting oliguria, a sign of acute kidney injury (AKI). To this end, electronic health record data from consecutive patients admitted to the intensive care unit (ICU) between 2010 and 2019 were used and oliguria was defined as a urine output of less than 0.5 mL/kg/h. Furthermore, a light-gradient boosting machine was used for model development. Among the 9,241 patients who participated in the study, the proportions of patients with urine output < 0.5 mL/kg/h for 6 h and with AKI during the ICU stay were 27.4% and 30.2%, respectively. The area under the curve (AUC) values provided by the prediction algorithm for the onset of oliguria at 6 h and 72 h using 28 clinically relevant variables were 0.964 (a 95% confidence interval (CI) of 0.963-0.965) and 0.916 (a 95% CI of 0.914-0.918), respectively. The Shapley additive explanation analysis for predicting oliguria at 6 h identified urine values, severity scores, serum creatinine, oxygen partial pressure, fibrinogen/fibrin degradation products, interleukin-6, and peripheral temperature as important variables. Thus, this study demonstrates that a machine-learning algorithm can accurately predict oliguria onset in ICU patients, suggesting the importance of oliguria in the early diagnosis and optimal management of AKI.

Predictors of oliguria in post-traumatic acute kidney injury.

BACKGROUND: Acute kidney injury is classified by urine output into non-oliguric and oliguric variants. Non-oliguric acute kidney injury has lower morbidity and mortality and accounts for up to 64% of acute kidney injury in hospitalized patients. However, the incidence of non-oliguric acute kidney injury in the trauma population and whether the 2 variants of acute kidney injury share the same risk factors is unknown. We hypothesized that oliguria would be present in the majority of acute kidney injury in severely injured trauma patients and that unique risk factors would predispose patients to the development of oliguria. METHODS: Patients admitted to the trauma intensive care unit and diagnosed with an acute kidney injury between 2016 to 2021 were identified. Cases were categorized based on urine output into oliguric (<400 mL per day) and non-oliguric (>400 mL per day) disease. Risk factors, management, and outcomes were compared. Logistic regression was used to identify risk factors associated with oliguria. RESULTS: A total of 227 patients met inclusion criteria. Non-oliguric acute kidney injury accounted for 74% of all cases and was associated with greater survival (78% vs 35.6%, P < .001). Using logistic regression, female sex, vasopressor use, and a greater net fluid balance at 48 hours were all predictive of oliguria (while controlling for age, race, shock index, massive transfusion, operative intervention, cardiac arrest, and nephrotoxic medication exposure). CONCLUSION: Non-oliguria accounts for the majority of post-traumatic acute kidney injury and is associated with improved survival. Specific risk factors for the development of oliguric acute kidney injury include female sex, vasopressor use, and a higher net fluid balance at 48 hours.

Urine output as one of the most important features in differentiating in-hospital death among patients receiving extracorporeal membrane oxygenation: a random forest approach.

BACKGROUND: It is common to support cardiovascular function in critically ill patients with extracorporeal membrane oxygenation (ECMO). The purpose of this study was to identify patients receiving ECMO with a considerable risk of dying in hospital using machine learning algorithms. METHODS: A total of 1342 adult patients on ECMO support were randomly assigned to the training and test groups. The discriminatory power (DP) for predicting in-hospital mortality was tested using both random forest (RF) and logistic regression (LR) algorithms. RESULTS: Urine output on the first day of ECMO implantation was found to be one of the most predictive features that were related to in-hospital death in both RF and LR models. For those with oliguria, the hazard ratio for 1 year mortality was 1.445 (p < 0.001, 95% CI 1.265-1.650). CONCLUSIONS: Oliguria within the first 24 h was deemed especially significant in differentiating in-hospital death and 1 year mortality.

Tocilizumab Associated With Survival in Patients Hospitalized for COVID-19 Acute Respiratory Distress Syndrome and Low Urine Output.

BACKGROUND: Acute respiratory distress syndrome (ARDS) with oliguria is associated with increased mortality. Interleukin-6 (IL-6) plays an integral role in the pathophysiology of both disease processes. Patients who experience severe COVID-19 have demonstrated higher IL-6 levels compared to baseline, and use of tocilizumab has demonstrated efficacy in such cohorts. We set out to investigate the relationship between tocilizumab use, COVID-19 ARDS, low urine output, and mortality. METHODS: Retrospective cohort review of adult patients aged ≥ 18 years with COVID-19 and moderate or severe ARDS, admitted to the intensive care unit (ICU) of a tertiary referral center in metropolitan Detroit. Patients were analyzed based on presence of oliguria (defined as ≤ 0.7 mL/kg/h) on the day of intubation and exposure to tocilizumab while inpatient. The primary outcome was inpatient mortality. RESULTS: One hundred and twenty-eight patients were analyzed, 103 (80%) with low urine output, of whom 30 (29%) received tocilizumab. In patients with low urine output, risk factors associated with mortality on univariate analysis included Black race (P = .028), lower static compliance (P = .015), and tocilizumab administration (P = .002). Tocilizumab (odds ratio 0.245, 95% confidence interval 0.079-0.764, P = .015) was the only risk factor independently associated with survival on multivariate logistic regression analysis. CONCLUSION: In this retrospective cohort review of patients hospitalized with COVID-19 and moderate or severe ARDS, tocilizumab administration was independently associated with survival in patients with low urine output ≤ 0.7 mL/kg/h on the day of intubation. Prospective studies are needed to investigate the impact of urine output on efficacy of interleukin-targeted therapies in the management of ARDS.

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.

Early detection of oliguric events in critically ill patients in the ICU with a novel continuous urine flow measurement device: results of an initial validation study.

OBJECTIVES: Urine output is used to evaluate fluid status and is an important marker for acute kidney injury (AKI). Our primary aim was to validate a new automatic urine output monitoring device by comparison to the current practice - the standard urometer. METHODS: We conducted a prospective observational study in three ICUs. Urine flow measurements by Serenno Medical Automatic urine output measuring device (Serenno Medical, Yokneam, Israel) were compared to standard urometer readings taken automatically at 5-minutes intervals by a camera, and to hourly urometer readings by the nurses, both over 1 to 7 days. Our primary outcome was the difference between urine flow assessed by the Serenno device and reference camera-derived measurements (Camera). Our secondary outcome was the difference between urine flow assessed by the Serenno device and hourly nursing assessments (Nurse), and detection of oliguria. RESULTS: Thirty-seven patients completed the study, with 1,306 h of recording and a median of 25 measurement hours per patient. Bland and Altman analysis comparing the study device to camera measurements demonstrated good agreement, with a bias of -0.4 ml/h and 95% confidence intervals ranging from - 28 to 27ml/h. Concordance was 92%. The correlation between Camera and hourly nursing assessment of urine output was distinctly worse with a bias of 7.2 ml and limits of agreement extending from - 75 to + 107 ml. Severe oliguria (urine output < 0.3 ml/kg/h) lasting 2 h or more was common and observed in 8 (21%) of patients. Among the severe oliguric events lasting more than 3 consecutive hours, 6 (41%) were not detected or documented by the nursing staff. There were no device-related complications. CONCLUSION: The Serenno Medical Automatic urine output measuring device required minimal supervision, little ICU nursing staff attention, and is sufficiently accurate and precise. In addition to providing continuous assessments of urine output, it was considerably more accurate than hourly nursing assessments.

The role of the bladder diary in phenotyping men with LUTS.

AIMS: The aim of this study was to compare the clinical characteristics of men with lower urinary tract symptoms (LUTS) grouped by 24-h urine output determined from a bladder voiding diary. METHODS: An online database was queried to identify men who completed a 24-hour bladder diary (24HBD), and the Lower Urinary Tract Symptom Score (LUTSS) questionnaire from 2015 to 2019 using a mobile app. Data from the bladder diary and questionnaire were contemporaneously matched within a 2-week period. Additional data, including maximum uroflow (Qmax ) and postvoid residual urine (PVR), were obtained from the electronic medical record (EMR). The cohort was divided into three groups: normal, oliguria, and polyuria based on their 24-hour voided volume (24HVV). The LUTSS, 24HVV, maximum voided volume (MVV), maximum flow rate (Qmax ), and PVR were compared between those with oliguria and polyuria. RESULTS: A total of 327 men (mean age 62, SD: 19) completed the LUTSS questionnaire and contemporaneous 24HBD. Of these, 61% had a normal 24HVV, 13% had oliguria, and 26% had polyuria. A total of 147 patients from the study cohort had contemporaneous Qmax and PVR abstracted from the EMR. There was no difference in symptom severity, bother, or PVR among the three patient groups. However, several objective metrics were significantly correlated with urine output. Men with oliguria, as compared to men with polyuria were older (65 vs. 55 years) and had lower MVV (260 vs. 470 mL), fewer voids/24 h (8 vs. 13), and lower Qmax (8.5 vs. 18.3 mL/s). CONCLUSIONS: These observations suggest that men with oliguria or polyuria and LUTS constitute easily distinguished phenotypes that might require different diagnostic and therapeutic algorithms. Those with oliguria were older, and had lower MVVs and much lower uroflows, suggesting that they are more likely to have underlying disorders such as bladder outlet obstruction and detrusor underactivity or may be patients with overactive bladder who reduced fluid intake to improve symptoms.

Explainable machine learning model for predicting furosemide responsiveness in patients with oliguric acute kidney injury.

BACKGROUND: Although current guidelines didn't support the routine use of furosemide in oliguric acute kidney injury (AKI) management, some patients may benefit from furosemide administration at an early stage. We aimed to develop an explainable machine learning (ML) model to differentiate between furosemide-responsive (FR) and furosemide-unresponsive (FU) oliguric AKI. METHODS: From Medical Information Mart for Intensive Care-IV (MIMIC-IV) and eICU Collaborative Research Database (eICU-CRD), oliguric AKI patients with urine output (UO) < 0.5 ml/kg/h for the first 6 h after ICU admission and furosemide infusion ≥ 40 mg in the following 6 h were retrospectively selected. The MIMIC-IV cohort was used in training a XGBoost model to predict UO > 0.65 ml/kg/h during 6-24 h succeeding the initial 6 h for assessing oliguria, and it was validated in the eICU-CRD cohort. We compared the predictive performance of the XGBoost model with the traditional logistic regression and other ML models. RESULTS: 6897 patients were included in the MIMIC-IV training cohort, with 2235 patients in the eICU-CRD validation cohort. The XGBoost model showed an AUC of 0.97 (95% CI: 0.96-0.98) for differentiating FR and FU oliguric AKI. It outperformed the logistic regression and other ML models in correctly predicting furosemide diuretic response, achieved 92.43% sensitivity (95% CI: 90.88-93.73%) and 95.12% specificity (95% CI: 93.51-96.3%). CONCLUSION: A boosted ensemble algorithm can be used to accurately differentiate between patients who would and would not respond to furosemide in oliguric AKI. By making the model explainable, clinicians would be able to better understand the reasoning behind the prediction outcome and make individualized treatment.

Evaluation of neonatal acute kidney injury (AKI) after emergency gastrointestinal surgery.

BACKGROUND: The overall incidence of acute kidney injury (AKI) in neonates undergoing emergency gastrointestinal surgery is yet to be determined. The study aims are to analyze our experience in emergency gastrointestinal surgery for neonates and to evaluate the incidence of AKI. METHODS: We conducted a retrospective study of neonates undergoing emergency gastrointestinal surgery between June 31, 2018 and May 10, 2022 (N = 329). The primary outcome was the overall incidence of AKI. The diagnostic AKI was based on the Modified Kidney Disease: Improving Global Outcomes (KDIGO) definition of neonatal AKI. The secondary outcomes, including the postoperative length of hospital stay (PLOS), 24-h mortality, in-hospital mortality, and total in-hospital cost, were analyzed. The risk factors associated with the development of postoperative AKI were also analyzed. RESULTS: The incidence of postoperative AKI was 9.1% (30/329). No significant differences were detected in the 24-h mortality and in-hospital mortality between the two cohorts. In the final model, patients undergoing mechanical ventilation before surgery, vasopressor support, surgical duration, intraoperative oliguria and preoperative lowest serum creatinine (SCr), were independently associated with AKI. CONCLUSION: Our study found that patients undergoing mechanical ventilation before surgery, vasopressor support, surgical duration, intraoperative oliguria and preoperative lowest SCr were independently associated with postoperative AKI in neonates who accepted emergency gastrointestinal surgeries.

Association between intraoperative oliguria and postoperative acute kidney injury in non-cardiac surgical patients: a systematic review and meta-analysis.

PURPOSE: This systematic review and meta-analysis aimed to evaluate the association between intraoperative oliguria and the risk of postoperative acute kidney injury (AKI) in patients undergoing non-cardiac surgery. METHODS: The MEDLINE and EMBASE databases were searched up to August 2022 for studies in adult patients undergoing non-cardiac surgery, where the association between intraoperative urine output and the risk of postoperative AKI was assessed. Both randomised and non-randomised studies were eligible for inclusion. Study selection and risk of bias assessment were independently performed by two investigators. The risk of bias was evaluated using the Newcastle-Ottawa scale. We performed meta-analysis of the reported multivariate adjusted odds ratios for the association between intraoperative oliguria (defined as urine output < 0.5 mL/kg/hr) and the risk of postoperative AKI using the inverse-variance method with random effects models. We conducted sensitivity analyses using varying definitions of oliguria as well as by pooling unadjusted odds ratios to establish the robustness of the primary meta-analysis. We also conducted subgroup analyses according to surgery type and definition of AKI to explore potential sources of clinical or methodological heterogeneity. RESULTS: Eleven studies (total 49,252 patients from 11 observational studies including a post hoc analysis of a randomised controlled trial) met the selection criteria. Seven of these studies contributed data from a total 17,148 patients to the primary meta-analysis. Intraoperative oliguria was associated with a significantly elevated risk of postoperative AKI (pooled adjusted odds ratio [OR] 1.74; 95% confidence interval [CI] 1.36-2.23, p < 0.0001, 8 studies). Sensitivity analyses supported the robustness of the primary meta-analysis. There was no evidence of any significant subgroup differences according to surgery type or definition of AKI. CONCLUSIONS: This study demonstrated a significant association between intraoperative oliguria and the risk of postoperative AKI, regardless of the definitions of oliguria or AKI used. Further prospective and multi-centre studies using standardised definitions of intraoperative oliguria are required to define the thresholds of oliguria and establish strategies to minimise the risk of AKI.