Extracorporeal membrane oxygenation (ECMO) is a cardiorespiratory support technique for patients with circulatory or pulmonary failure. Frequently, large-volume fluid resuscitation is needed to ensure sufficient extracorporeal blood flow in patients initiating ECMO. However, excessive overhydration is known to increase mortality in critically ill patients. Therefore, in order to define a tolerant volume range in patients undergoing ECMO treatment, the association between cumulative fluid balance (CFB) and outcome was evaluated in patients undergoing ECMO. This retrospective multicenter cohort study was conducted with 723 patients who underwent ECMO in three tertiary care hospitals between 2005 and 2016. CFB was calculated as total fluid input minus total fluid output during the first 3 days from ECMO initiation. The patients were divided into groups that initiated ECMO owing to cardiovascular disease (CVD)-related or non-cardiovascular disease (non-CVD)-related causes. The primary endpoint was mortality within 90 days after ECMO commencement. Totals of 406 and 317 patients were included in the CVD and non-CVD groups, respectively. In the CVD group, the mean age was 58.4 ± 17.7 years, and 68.2% were male. The mean age was 55.7 ± 15.7 years, and 65.3% were male in the non-CVD group. The median CFB values were 64.7 and 53.5 ml/kg in the CVD and non-CVD groups, respectively. Multivariable analysis using Cox proportional hazards models revealed a significantly increased risk of 90-day mortality in patients with higher CFB values in both the CVD and non-CVD groups. However, the risks were elevated only in the two CFB quartile groups with the largest CFB amounts. Cubic spline models showed that mortality risk began to increase significantly when CFB was 82.3 ml/kg in the CVD group. In patients with respiratory diseases, the mortality risk increase was significant for those with CFB levels above 189.6 ml/kg. Mortality risk did not increase until a certain level of fluid overload was reached in patients undergoing ECMO. Adequate fluid resuscitation is critical to improving outcomes in these patients.

Guidelines for general hypertension treatment do not recommend the combined use of renin-angiotensin-aldosterone system (RAAS) inhibitors due to the risk of hyperkalemia. However, a recent clinical trial showed that polycystic kidney disease (PKD) patients had infrequent episodes of hyperkalemia despite receiving combined RAAS inhibitors. Because intrarenal RAAS is a main component for renal potassium handling, we further investigated the association between intrarenal RAAS activity and serum potassium level in patients with chronic kidney disease, particularly in PKD patients, and examined whether intrarenal RAAS activity has a prognostic role in patients with PKD. A total of 1788 subjects from the KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD) were enrolled in this study. Intrarenal RAAS activity was assessed by the measurement of urinary angiotensinogen (AGT). The primary outcome was the composite of all-cause mortality and renal function decline. Patients with PKD had a significantly lower serum potassium level in chronic kidney disease stages 1 to 3b than non-PKD patients. In logistic regression analysis, after adjusting for multiple confounders, PKD patients had a significantly lower risk of hyperkalemia than non-PKD patients. In multivariable linear regression analysis, the urinary AGT/creatinine (Cr) ratio was negatively correlated with the serum potassium level (β = − 0.058, P = 0.017) and positively correlated with the transtubular potassium gradient (TTKG, β = 0.087, P = 0.001). In propensity score matching analysis, after matching factors associated with serum potassium and TTKG, PKD patients had a significantly higher TTKG (P = 0.021) despite a lower serum potassium level (P = 0.004). Additionally, the urinary AGT/Cr ratio was significantly higher in PKD patients than in non-PKD patients (P = 0.011). In 293 patients with PKD, high urinary AGT/Cr ratio was associated with increased risk of the composite outcome (hazard ratio 1.29; 95% confidence interval, 1.07–1.55; P = 0.007). High activity of intrarenal RAAS is associated with increased urinary potassium excretion and low serum potassium level in patients with PKD. In addition, intrarenal RAAS activity can be a prognostic marker for mortality and renal function decline in these patients.

Both serum creatinine (sCr) and estimated glomerular filtration rate (eGFR) have been used to assess kidney function in public health check-ups. However, when the sCr is within the normal levels but the eGFR is 60 mL/min/1.73 m² were analyzed. The subjects were classified into quartiles based on sCr levels. The primary outcome was the development of eGFR <60 mL/min/1.73 m² on two consecutive measures. During a mean follow-up of 8.4 ± 4.3 years, 779 (8.2%) subjects developed eGFR <60 mL/min/1.73 m². The incidence of the development of eGFR <60 mL/min/1.73 m² was higher in the higher quartiles than in the lowest quartile. In multivariable Cox analysis, the highest quartile was associated with an increased risk for the development of eGFR <60 mL/min/1.73 m² (hazard ratio (HR), 4.71; 95% confidence interval (CI), 3.29–6.74 in females; HR, 12.77; 95% CI, 7.69–21.23 in males). In the receiver operating characteristic curve analysis, adding sCr to the traditional risk factors for CKD improved the accuracy of predicting the development of eGFR <60 mL/min/1.73 m² (area under the curve, 0.83 vs. 0.80 in females and 0.85 vs. 0.78 in males), and the cutoff value of sCr was 0.75 mg/dL and 0.78 mg/dL in females and males. Cautious interpretation is necessary when sCr is within the normal range, considering that the upper normal range of sCr has a higher risk of CKD development.