The role of Cushing's reflex and the vasopressin-mediated oligoanuric response to intracranial hypertension in patients with abdominal compartment syndrome.

BACKGROUND: We examined the link between increased intra-abdominal pressure, intracranial pressure, and vasopressin release as a potential mechanism. Intra-abdominal pressure, produced by abdominal-cavity insufflation with carbon dioxide (CO2) during laparoscopic abdominal procedures to facilitate visualization, is associated with various complications, including arterial hypertension and oliguria. METHODS: Mean arterial pressure, optic nerve sheath diameter, measured as a proxy for intracranial pressure, plasma vasopressin, serum and urine osmolarity, and urine output were measured 4 times during laparoscopic sleeve gastrectomy in 42 patients: before insufflation with CO2 (T0); after insufflation to 15 cm water (H2O) pressure, with 5 cm H2O positive end-expiratory pressure (T1); after positive end-expiratory pressure was raised to 10 cm H2O (T2); and after a return to the baseline state (T3). Mean values at T0 to T3 and the directional consistency of changes (increase/decrease/ unchanged) were compared among the 4 data-collection points. RESULTS: Statistically significant elevations (all P ≤ .001) were noted from T0 to T1 and from T0 to T2 in mean arterial pressure, optic nerve sheath diameter, and vasopressin, followed by decreases at T3. For optic nerve sheath diameter and vasopressin, the increases at T1 and T2 occurred in 98% and 100% of patients, ultimately exceeding normal levels in 88 and 97%, respectively. Conversely, urine output fell from T0 to T1 and T2 by 60.9 and 73.4%, decreasing in 88.1% of patients (all P < .001). Patients with class II obesity exhibited statistically greater increases in optic nerve sheath diameter and vasopressin, but statistically less impact on urine output, than patients with class III obesity. CONCLUSION: Increased mean arterial pressure, intracranial pressure, and vasopressin release appear to be intermediary steps between increased intra-abdominal pressure and oliguria. Further research is necessary to determine any causative links between these physiological changes.

Effect of losartan on the recoverability of renal function in anuric and oliguric patients with a solitary obstructed kidney: a double-blind randomized placebo-controlled trial.

OBJECTIVES: To assess the role of the angiotensin receptor blocker losartan on the recoverability of renal function after de-obstruction in patients with anuria and oliguria. MATERIALS AND METHODS: This was a double-blind randomized placebo-controlled trial in anuric or oliguric patients with calcular obstruction of solitary kidney. Patients with an anomalous kidney or those with an American Society of Anesthesiology score of >3 were excluded. After relief of obstruction, patients were allocated to receive either losartan potassium 25 mg or placebo for 3 months. Serum creatinine (sCr) and renographic glomerular filtration rate (GFR) were measured at nadir and after 3 months. Changes in sCr and renographic GFR were calculated by subtracting the values at nadir from those at 3 months. Improvement, stabilization or deterioration of sCr and renographic GFR were defined as percentage increase or decrease from nadir ≥10%, while changes <10% were considered as stabilization. RESULTS: A total of 76 patients completed 3 months of follow-up. Demographics and peri-operative data were comparable in the two groups. The median (range) sCr change was -1.05 (-1.8, 0.4) and -0.5 (-1.3, 0.1) mg/dL in the losartan and placebo, groups, respectively (P = 0.07). In the losartan group, renographic GFR had improved in 26 (59.1%) and deteriorated in six (13.6%) patients, while, in the placebo group, it had improved in eight (25%) and deteriorated in 10 patients (31.3%; P = 0.01). Losartan also enhanced renographic GFR improvement vs placebo by a median (range) of 6.9 (-9, 44) vs 1.4 (-10, 32) mL/min (P = 0.004). CONCLUSIONS: In patients with anuria and oliguria, losartan treatment contributes to renal function recoverability after relief of calcular obstruction of the solitary kidney.

Clinical effect and safety of continuous renal replacement therapy in the treatment of neonatal sepsis-related acute kidney injury.

BACKGROUND: Sepsis is the leading cause of acute kidney injury (AKI) in the neonatal intensive care unit (NICU). The aim of the study is to explore the efficacy and security of continuous renal replacement therapy (CRRT) in the treatment of neonatal sepsis-related AKI. METHOD: Totally12 sepsis-related AKI neonates treated with CRRT were hospitalized in the NICU of Shanghai Children's Hospital between November 2012 and November 2019, and the clinical data of these 12 cases were retrospectively analyzed. Renal function, acid-base balance, electrolytes, blood pressure and hemodynamics indexes were recorded before CRRT initiation, 12/24/48 h after CRRT initiation and at the end of CRRT respectively. The efficacy of CRRT was evaluated and the clinical outcome was observed in these 12 sepsis-related AKI neonates. Repeated measurement analysis of variance was used for statistical analysis of the data. RESULT: (1) Continuous veno-venous hemodialysis filtration (CVVHDF) was used in 12 cases of sepsis-related AKI neonates. There were 6 cases with oliguria, 3 cases with fluid overload (FO), 3 cases with septic shock. The duration of CRRT was 49 ~ 110 h, average (76.2 ± 23.5) h. (2) The blood pressure (BP) of 12 sepsis -related AKI neonates could reach the normal level (40-60 mmHg) 12 h after CRRT initiation, and the normal BP level could be maintained during the CRRT treatment. After 12 h CRRT, the blood pH value increased to the normal range (7.35 ~ 7.45). After 12 h CRRT treatment, the oxygenation index of 12sepsis-related AKI neonates could reach 200 mmHg. After 24 h CRRT treatment, it could rise to more than 300 mmHg. Serum potassium, serum urea nitrogen and serum creatinine levels decreased significantly 12 h after CRRT initiation, and reached the normal range 24 h after CRRT initiation. The urine volume significantly increased 24 h after CRRT initiation. (3) Venous catheterization was performed successfully in all sepsis-related AKI neonates. We observed 2 cases of thrombocytopenia, 1 case of obstruction and 1 case of hypotension in the course of CRRT. There were no complications such as hypothermia, hemorrhage, thrombosis and infection.11 neonates were cured and discharged. One neonate was treated with CRRT and passed through the oliguria stage of AKI, but died after the parents gave up the treatment. CONCLUSIONS: It is safe and effective to treat neonatal sepsis-related AKI with CRRT, which should be an effective measure for the treatment of sepsis-related AKI neonates.

Machine learning for the prediction of volume responsiveness in patients with oliguric acute kidney injury in critical care.

BACKGROUND AND OBJECTIVES: Excess fluid balance in acute kidney injury (AKI) may be harmful, and conversely, some patients may respond to fluid challenges. This study aimed to develop a prediction model that can be used to differentiate between volume-responsive (VR) and volume-unresponsive (VU) AKI. METHODS: AKI patients with urine output < 0.5 ml/kg/h for the first 6 h after ICU admission and fluid intake > 5 l in the following 6 h in the US-based critical care database (Medical Information Mart for Intensive Care (MIMIC-III)) were considered. Patients who received diuretics and renal replacement on day 1 were excluded. Two predictive models, using either machine learning extreme gradient boosting (XGBoost) or logistic regression, were developed to predict urine output > 0.65 ml/kg/h during 18 h succeeding the initial 6 h for assessing oliguria. Established models were assessed by using out-of-sample validation. The whole sample was split into training and testing samples by the ratio of 3:1. MAIN RESULTS: Of the 6682 patients included in the analysis, 2456 (36.8%) patients were volume responsive with an increase in urine output after receiving > 5 l fluid. Urinary creatinine, blood urea nitrogen (BUN), age, and albumin were the important predictors of VR. The machine learning XGBoost model outperformed the traditional logistic regression model in differentiating between the VR and VU groups (AU-ROC, 0.860; 95% CI, 0.842 to 0.878 vs. 0.728; 95% CI 0.703 to 0.753, respectively). CONCLUSIONS: The XGBoost model was able to differentiate between patients who would and would not respond to fluid intake in urine output better than a traditional logistic regression model. This result suggests that machine learning techniques have the potential to improve the development and validation of predictive modeling in critical care research.

Disfunción de vaciado y retención aguda de orina / Voiding dysfunction and acute urinary retention

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Oliguria in critically ill patients: a narrative review.

Oliguria is often observed in critically ill patients. However, different thresholds in urine output (UO) have raised discussion as to the clinical importance of a transiently reduced UO of less than 0.5 ml/kg/h lasting for at least 6 h. While some studies have demonstrated that isolated oliguria without a concomitant increase in serum creatinine is associated with higher mortality rates, different underlying pathophysiological mechanisms suggest varied clinical importance of reduced UO, as some episodes of oliguria may be fully reversible. We aim to explore the clinical relevance of oliguria in critically ill patients and propose a clinical pathway for the diagnostic and therapeutic management of an oliguric, critically ill patient.

Urine volume as a predicting factor for furosemide clearance during continuous infusion in AKI septic shock patients on hemodiafiltration.

BACKGROUND: This study assessed the contribution of intracorporeal (IC) and extracorporeal clearance (EC) of furosemide in patients with septic acute kidney injury (AKI), and the relationship between plasma concentrations and urine volume. METHODS: Prospective cohort observational study of 15 patients with septic AKI undergoing continuous veno-venous hemodiafiltration (CVVHDF) divided according to urine volume (< 500 ml/12 h, Oliguria group, n = 5; > 500 ml/12 h, Diuresis group, n = 10) during continuous infusion of furosemide (120 mg/12 h) at steady-state condition. Plasma and effluent furosemide concentrations were determined by high-performance liquid chromatography (HPLC)-mass spectrometry every 12 h for 48 h. RESULTS: Furosemide plasma concentrations and total body clearance (TBC) were 6.14 mg/l and 22.1 ml/min for the Oliguria group, and 2.63 mg/l and 54.4 ml/min for the Diuresis group, respectively (p < 0.05). When urine volume was < 500 ml/24 h, the furosemide plasma concentrations peaked at the potentially toxic value of 13.0 mg/l. Furosemide EC was not relevant for the Diuresis group, but it represented 18% of TBC for the Oliguria group. Furosemide plasma concentrations correlated positively with dose infusion for both groups (r = 0.728 and 0.685, p < 0.05), and negatively with urine volume only for the Diuresis (r = - 0.578, p < 0.01) but not for the Oliguria group (r = - 0.089, p = 0.715). CONCLUSIONS: For patients with urine volume > 500 ml/12 h continuous infusion of furosemide up to 480 mg/24 h leads to increasing urine volume, which can predict furosemide plasma levels within its safety range. When the urine volume is lower, the furosemide plasma levels are increased beyond any further diuretic efficacy.

Update on Perioperative Acute Kidney Injury.

Acute kidney injury (AKI) in the perioperative period is a common complication and is associated with increased morbidity and mortality. A standard definition and staging system for AKI has been developed, incorporating a reduction of the urine output and/or an increase of serum creatinine. Novel biomarkers may detect kidney damage in the absence of a change in function and can also predict the development of AKI. Several specific considerations for AKI risk are important in surgical patients. The surgery, especially major and emergency procedures in critically ill patients, may cause AKI. In addition, certain comorbidities, such as chronic kidney disease and chronic heart failure, are important risk factors for AKI. Diuretics, contrast agents, and nephrotoxic drugs are commonly used in the perioperative period and may result in a significant amount of in-hospital AKI. Before and during surgery, anesthetists are supposed to optimize the patient, including preventing and treating a hypovolemia and correcting an anemia. Intraoperative episodes of hypotension have to be avoided because even short periods of hypotension are associated with an increased risk of AKI. During the intraoperative period, urine output might be reduced in the absence of kidney injury or the presence of kidney injury with or without fluid responsiveness. Therefore, fluids should be used carefully to avoid hypovolemia and hypervolemia. The Kidney Disease: Improving Global Outcomes guidelines suggest implementing preventive strategies in high-risk patients, which include optimization of hemodynamics, restoration of the circulating volume, institution of functional hemodynamic monitoring, and avoidance of nephrotoxic agents and hyperglycemia. Two recently published studies found that implementing this bundle in high-risk patients reduced the occurrence of AKI in the perioperative period. In addition, the application of remote ischemic preconditioning has been studied to potentially reduce the incidence of perioperative AKI. This review discusses the epidemiology and pathophysiology of surgery-associated AKI, highlights the importance of intraoperative oliguria, and emphasizes potential preventive strategies.

Tamm-Horsfall protein/uromodulin deficiency elicits tubular compensatory responses leading to hypertension and hyperuricemia.

Expression of Tamm-Horsfall protein (THP or uromodulin) is highly restricted to the kidney thick ascending limb (TAL) of loop of Henle. Despite the unique location and recent association of THP gene mutations with hereditary uromodulin-associated kidney disease and THP single nucleotide polymorphisms with chronic kidney disease and hypertension, the physiological function(s) of THP and its pathological involvement remain incompletely understood. By studying age-dependent changes of THP knockout (KO) mice, we show here that young KO mice had significant salt and water wasting but were partially responsive to furosemide, due to decreased luminal translocation of Na-K-Cl cotransporter 2 (NKCC2) in the TAL. Aged THP KO mice were, however, markedly oliguric and unresponsive to furosemide, and their NKCC2 was localized primarily in the cytoplasm as evidenced by lipid raft floatation assay, cell fractionation, and confocal and immunoelectron microscopy. These aged KO mice responded to metolazone and acetazolamide, known to target distal and proximal tubules, respectively. They also had marked upregulation of renin in juxtaglomerular apparatus and serum, and they were hypertensive. Finally, the aged THP KO mice had significant upregulation of Na-coupled urate transporters Slc5a8 and Slc22a12 as well as sodium-hydrogen exchanger 3 (NHE3) in the proximal tubule and elevated serum uric acid and allantoin. Collectively, our results suggest that THP deficiency can cause progressive disturbances in renal functions via initially NKCC2 dysfunction and later compensatory responses, resulting in prolonged activation of the renin-angiotensin-aldosterone axis and hyperuricemia.

Nephroprotective Effect of EDL Peptide at Acute Injury of Kidneys of Different Genesis.

EDL peptide produced a nephroprotective effect on experimental models gentamycin-induced nephropathy and ischemia/reperfusion kidney injury in rats. The nephroprotective effect of EDL peptide manifested in prevention of oliguria and retention azotemia, a decrease in proteinuria and sodium excretion, prevention of critical decrease in activities of antioxidant enzymes, suppression of LPO, and normalization of energy supply to kidneys cells. Our findings confirm the prospects of further studies of the nephroprotective properties of peptide EDL in various pathologies of the kidneys.

Effect of high-dose furosemide on the prognosis of critically ill patients.

PURPOSE: Diuretics are used frequently in critically ill patients. We investigated the effects of furosemide on the prognosis. MATERIALS AND METHODS: Following a retrospective review of patients admitted to the medical intensive care unit (ICU), we analyzed risk factors with variables including initial furosemide dose for ICU mortality. RESULTS: A total of 448 patients were included. Total furosemide dose during the first three days of the ICU stay (odds ratio (OR) 2.35, 95% confidence interval (CI) 1.01-5.02) and fluid balance during the same period (OR 3.04, 95% CI 1.46-6.31) were associated with ICU mortality, as were malignancy, chronic furosemide use, and APACHE II score. However, in oliguric patients, positive fluid balance was associated with ICU mortality (OR 22.33, 95% CI 1.82-273.72) but the high-dose furosemide was not. In contrast, in non-oliguric patients, high-dose furosemide was associated with ICU mortality (OR 2.47, 95% CI 1.01-5.68); however, the positive fluid balance showed only a trend for high ICU mortality. CONCLUSION: Early high-dose furosemide use is associated with ICU mortality, particularly in non-oliguric patients. We suggest that furosemide should be used with caution even in non-oliguric critically ill patients until the safety is confirmed in powered study.

Low Versus Standard Urine Output Targets in Patients Undergoing Major Abdominal Surgery: A Randomized Noninferiority Trial.

OBJECTIVE: To determine whether a low perioperative minimum urine output target is safe and fluid sparing when compared with the standard target. BACKGROUND: A minimum hourly urine output of 0.5 mL/kg is a key target guiding perioperative fluid therapy. Few data support this standard practice, which may contribute to perioperative fluid overloading. METHODS: We randomized patients without significant risk factors for acute kidney injury undergoing elective colectomy to a minimum urine output target of 0.2 mL/kg/h (low group) or 0.5 mL/kg/h (standard group) from induction of anesthesia until 8 AM 2 days after surgery. Maintenance fluids were standardized and additional fluids administered to achieve the targets. Primary outcome was noninferiority for urine neutrophil gelatinase-associated lipocalin on the day after surgery. RESULTS: Between November 21, 2011 and July 11, 2013, 40 participants completed the study. The low group received 3170 mL (95% confidence interval 2380-3960) intravenous fluids versus 5490 mL (95% confidence interval 4570-6410) in the standard group (P = 0.0004), and was noninferior for neutrophil gelatinase-associated lipocalin [14.7 µg/L (interquartile range 7.60-28.9) vs 18.4 µg/L (interquartile range 8.30-21.2); Pnoninferiority = 0.0011], serum cystatin C (Pnoninferiority < 0.0001), serum creatinine (Pnoninferiority = 0.0004), and measured glomerular filtration (Pnoninferiority = 0.0003). Effective renal plasma flow increased in both groups after surgery, and more in the standard group (Pnoninferiority = 0.125). CONCLUSIONS: A perioperative urine output target of 0.2 mL/kg/h is noninferior to the standard target of 0.5 mL/kg/h and results in a large intravenous fluid sparing. This target should be adopted in surgical patients without significant kidney injury risk factors.

Early-phase cumulative hypotension duration and severe-stage progression in oliguric acute kidney injury with and without sepsis: an observational study.

BACKGROUND: Managing blood pressure in patients with acute kidney injury (AKI) could effectively prevent severe-stage progression. However, the effect of hypotension duration in the early phase of AKI remains poorly understood. This study investigated the association between early-phase cumulative duration of hypotension below threshold mean arterial pressure (MAP) and severe-stage progression of oliguric AKI in critically ill patients, and assessed the difference in association with presence of sepsis. METHODS: This was a single-center, observational study conducted in the ICU of a university hospital in Japan. We examined data from adults with oliguric AKI who were admitted to the ICU during 2010-2014 and stayed in the ICU for ≥24 h after diagnosis of stage-1 oliguric AKI defined in the Kidney Disease Improving Global Outcomes (KDIGO) guidelines. The primary outcome was the progression from stage-1 oliguric AKI to stage-3 oliguric AKI (progression to oligoanuria and use of renal replacement therapy) according to the KDIGO criteria. During the first 6 h after oliguric AKI, we analyzed the association between cumulative time the patient had below threshold MAP (65, 70, and 75 mm Hg) and progression to stage-3. RESULTS: Among 538 patients with oliguric AKI, progression to stage-3 increased as the time spent below any threshold MAP was elongated. In the multivariable analysis of all patients, longer hypotension time (3-6 h) showed significant association with stage-3 progression for the time spent below MAP of 65 mm Hg (adjusted odds ratio (OR) 3.73, 95% confidence interval (CI) 1.53-9.09, p = 0.004), but the association was attenuated for the threshold MAP of 70 mm Hg (adjusted OR 2.35, 95% CI 0.96-5.78, p = 0.063) and 75 mm Hg (adjusted OR 1.92, 95% CI 0.72-5.15, p = 0.200). Longer hypotension time with the thresholds of 65 and 70 mm Hg was significantly associated with the risk of stage-3 progression in patients without sepsis, whereas the association was weak and not significant in patients with sepsis. CONCLUSIONS: Even in a short time frame (6 h) after oliguric AKI diagnosis, early-phase cumulative hypotension duration was associated with progression to stage-3 oliguric AKI, especially in patients without sepsis.

Neutrophil Gelatinase-Associated Lipocalin as a Diagnostic Marker for Acute Kidney Injury in Oliguric Critically Ill Patients: A Post-Hoc Analysis.

BACKGROUND: Oliguria occurs frequently in critically ill patients, challenging clinicians to distinguish functional adaptation from serum-creatinine-defined acute kidney injury (AKIsCr). We investigated neutrophil gelatinase-associated lipocalin (NGAL)'s ability to differentiate between these 2 conditions. METHODS: This is a post-hoc analysis of a prospective cohort of adult critically ill patients. Patients without oliguria within the first 6 h of admission were excluded. Plasma and urinary NGAL were measured at 4 h after admission. AKIsCr was defined using the AKI network criteria with pre-admission serum creatinine or lowest serum creatinine value during the admission as the baseline value. Hazard ratios for AKIsCr occurrence within 72 h were calculated using Cox regression and adjusted for risk factors such as sepsis, pre-admission serum creatinine, and urinary output. Positive predictive values (PPV) and negative predictive values (NPV) were calculated for the optimal cutoffs for NGAL. RESULTS: Oliguria occurred in 176 patients, and 61 (35%) patients developed AKIsCr. NGAL was a predictor for AKIsCr in univariate and multivariate analysis. When NGAL was added to a multivariate model including sepsis, pre-admission serum creatinine and lowest hourly urine output, it outperformed the latter model (plasma p = 0.001; urinary p = 0.048). Cutoff values for AKIsCr were 280 ng/ml for plasma (PPV 80%; NPV 79%), and 250 ng/ml for urinary NGAL (PPV 58%; NPV 78%). CONCLUSIONS: NGAL can be used to distinguish oliguria due to the functional adaptation from AKIsCr, directing resources to patients more likely to develop AKIsCr.

Predictive value of the RIFLE urine output criteria on contrast-induced nephropathy in critically ill patients.

BACKGROUND: To investigate the predictive value of decreased urine output based on the Risk of renal dysfunction, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-stage renal disease (RIFLE) classification on contrast- induced acute kidney injury (CA-AKI) in intensive care (ICU) patients. METHODS: All patients who received contrast media (CM) injection for CT scan or coronary angiography during a 3-year period in a 24 bed medico-surgical ICU were reviewed. RESULTS: Daily serum creatinine concentrations and diuresis were measured for 3 days after CM injection. We identified 23 cases of CA-AKI in the 149 patients included (15.4 %). Patients who developed CA-AKI were more likely to require renal replacement therapy and had higher ICU mortality rates. At least one RIFLE urine output criteria was observed in 45 patients (30.2 %) and 14 of these 45 patients (31.1 %) developed CA-AKI based on creatinine concentrations. In 30 % of these cases, urine output decreased or didn't change after the increase in creatinine concentrations. The RIFLE urine output criteria had low sensitivity (39.1 %) and specificity (67.9 %) for prediction of CA-AKI, a low positive predictive value of 50 % and a negative predictive value of 87.2 %. The maximal dose of vasopressors before CM was the only independent predictive factor for CA-AKI. CONCLUSIONS: CA-AKI is a frequent pathology observed in ICU patients and is associated with increased need for renal replacement therapy and increased mortality. The predictive value of RIFLE urine output criteria for the development of CA-AKI based on creatinine concentrations was low, which limits its use for assessing the effects of therapeutic interventions on the development and progression of AKI.

Targeting Oliguria Reversal in Goal-Directed Hemodynamic Management Does Not Reduce Renal Dysfunction in Perioperative and Critically Ill Patients: A Systematic Review and Meta-Analysis.

BACKGROUND: We investigated whether resuscitation protocols to achieve and maintain urine output above a predefined threshold-including oliguria reversal as a target--prevent acute renal failure (ARF). METHODS: We performed a systematic review and meta-analysis using studies found by searching MEDLINE, EMBASE, and references in relevant reviews and articles. We included all studies that compared "conventional fluid management" (CFM) with "goal-directed therapy" (GDT) using cardiac output, urine output, or oxygen delivery parameters and reported the occurrence of ARF in critically ill or surgical patients. We divided studies into groups with and without oliguria reversal as a target for hemodynamic optimization. We calculated the combined odds ratio (OR) and 95% confidence intervals (CIs) using random-effects meta-analysis. RESULTS: We based our analyses on 28 studies. In the overall analysis, GDT resulted in less ARF than CFM (OR, 0.58; 95% CI, 0.44-0.76; P < 0.001; I = 34.3%; n = 28). GDT without oliguria reversal as a target resulted in less ARF (OR, 0.45; 95% CI, 0.34-0.61; P < 0.001; I = 7.1%; n = 7) when compared with CFM with oliguria reversal as a target. The studies comparing GDT with CFM in which the reversal of oliguria was targeted in both or in neither group did not provide enough evidence to conclude a superiority of GDT (targeting oliguria reversal in both protocols: OR, 0.63; 95% CI, 0.36-1.10; P = 0.09; I = 48.6%; n = 9, and in neither protocol: OR, 0.66; 95% CI, 0.37-1.16; P = 0.14; I = 20.2%; n = 12). CONCLUSIONS: Current literature favors targeting circulatory optimization by GDT without targeting oliguria reversal to prevent ARF. Future studies are needed to investigate the hypothesis that targeting oliguria reversal does not prevent ARF in critically ill and surgical patients.

Prediction of urine volume soon after birth using serum cystatin C.

BACKGROUND: Urine volume is an important clinical finding particularly during the early neonatal period. Oliguria is not a sign of impaired renal function but also a predictive factor for various complications and prognoses. It has been postulated that serum cystatin C (S-CysC) is a more sensitive biomarker for renal function than serum creatinine (S-Cr) in both adults and children. The objective of the current study was to investigate whether urine volume during 24 h after birth can be predicted using S-CysC. METHODS: The subjects were 87 infants. The average gestational age was 34.7 ± 2.9 weeks and the average birth weight was 2135 ± 614 g. Blood samples were obtained from either the umbilical cord or the peripheral veins or artery of the newborn at birth. Data regarding the amount of urine volume and fluid intake during the first 24 h of life, maternal S-Cr and S-CysC levels within 48 h before delivery, and neonatal S-Cr and S-CysC levels at birth were collected from the medical records. RESULTS: A significantly positive correlation was observed between maternal and neonatal S-Cr levels (r = 0.84, p < 0.0001) but not between maternal S-Cr levels and neonatal S-CysC levels (r = -0.069, p = 0.52). A significant negative correlation was seen between neonatal S-CysC levels and urine volume (r = -0.47, p < 0.0001). CONCLUSION: The present study findings indicate that it may be possible to use S-CysC levels at birth to predict urine volume during the first 24 h of life.

Reduction of Tubular Flow Rate as a Mechanism of Oliguria in the Early Phase of Endotoxemia Revealed by Intravital Imaging.

Urine output is widely used as a criterion for the diagnosis of AKI. Although several potential mechanisms of septic AKI have been identified, regulation of urine flow after glomerular filtration has not been evaluated. This study evaluated changes in urine flow in mice with septic AKI. The intratubular urine flow rate was monitored in real time by intravital imaging using two-photon laser microscopy. The tubular flow rate, as measured by freely filtered dye (FITC-inulin or Lucifer yellow), time-dependently declined after LPS injection. At 2 hours, the tubular flow rate was slower in mice injected with LPS than in mice injected with saline, whereas BP and GFR were similar in the two groups. Importantly, fluorophore-conjugated LPS selectively accumulated in the proximal tubules that showed reduced tubular flow at 2 hours and luminal obstruction with cell swelling at 24 hours. Delipidation of LPS or deletion of Toll-like receptor 4 in mice abolished these effects, whereas neutralization of TNF-α had little effect on LPS-induced tubular flow retention. Rapid intravenous fluid resuscitation within 6 hours improved the tubular flow rate only when accompanied by the dilation of obstructed proximal tubules with accumulated LPS. These findings suggest that LPS reduces the intratubular urine flow rate during early phases of endotoxemia through a Toll-like receptor 4-dependent mechanism, and that the efficacy of fluid resuscitation may depend on the response of tubules with LPS accumulation.

Risk factors for loss of residual renal function in children treated with chronic peritoneal dialysis.

In dialyzed patients, preservation of residual renal function is associated with better survival, lower morbidity, and greater quality of life. To analyze the evolution of residual diuresis over time, we prospectively monitored urine output in 401 pediatric patients in the global IPPN registry who commenced peritoneal dialysis (PD) with significant residual renal function. Associations of patient characteristics and time-variant covariates with daily urine output and the risk of developing oligoanuria (under 100 ml/m(2)/day) were analyzed by mixed linear modeling and Cox regression analysis including time-varying covariates. With an average loss of daily urine volume of 130 ml/m(2) per year, median time to oligoanuria was 48 months. Residual diuresis significantly subsided more rapidly in children with glomerulopathies, lower diuresis at start of PD, high ultrafiltration volume, and icodextrin use. Administration of diuretics significantly reduced oligoanuria risk, whereas the prescription of renin-angiotensin system antagonists significantly increased the risk oligoanuria. Urine output on PD was significantly associated in a negative manner with glomerulopathies (-584 ml/m(2)) and marginally with the use of icodextrin (-179 ml/m(2)) but positively associated with the use of biocompatible PD fluid (+111 ml/m(2)). Children in both Asia and North America had consistently lower urine output compared with those in Europe perhaps due to regional variances in therapy. Thus, in children undergoing PD, residual renal function depends strongly on the cause of underlying kidney disease and may be modifiable by diuretic therapy, peritoneal ultrafiltration, and choice of PD fluid.