ADMA and homoarginine independently predict mortality in critically ill patients.

BACKGROUND: Arginine metabolites are associated with cardiovascular and all-cause mortality in several patient groups. We investigated whether arginine metabolites are associated with mortality in patients with critical illness and whether associations are independent of other factors affecting prognosis in an Intensive Care Unit (ICU). METHODS: 1155 acutely unwell adult patients admitted to a mixed medical-surgical ICU were studied. Arginine, asymmetric dimethyl-l-arginine (ADMA), monomethyl-l-arginine (MMA), symmetric dimethyl-l-arginine (SDMA) and l-homoarginine were measured in a plasma sample collected at admission to ICU by liquid chromatography tandem mass spectrometry. Risk of death score was calculated using data submitted to the Australia and New Zealand Intensive Care Society. RESULTS: In this cohort, 163 patients (14.1%) died. ADMA (odds ratio = 1.159 (1.033-1.300) per 0.1 µmol/L increment, p = 0.012), homoarginine (odds ratio = 0.963 (0.934-0.992), p = 0.013) and risk of death score (odds ratio = 1.045 (1.037-1.053) per 1% increment, p < 0.001) were independently associated with mortality in ICU patients. The area under the receiver operator characteristic curve for risk of death score, ADMA and homoarginine combined for mortality was greater than for risk of death score alone (0.815 (95% CI 0.790-0.837) vs 0.796 (95% CI 0.781-0.820), p = 0.019). Other arginine metabolites were not independently associated with mortality. CONCLUSIONS: ADMA is positively and homoarginine negatively associated with mortality in ICU patients, independent of other clinical factors. Measuring ADMA and homoarginine may refine models to predict ICU mortality. Reducing ADMA and increasing homoarginine are potential therapeutic targets to reduce mortality in critically ill patients.

Relative Hyperglycemia Is an Independent Determinant of In-Hospital Mortality in Patients With Critical Illness.

OBJECTIVES: To determine whether relative hyperglycemia was associated with in-hospital mortality in critically ill patients independent of other prognostic variables and whether this association is affected by background glycemia. DESIGN: Prospective observational study. SETTING: Mixed medical-surgical ICU in a metropolitan teaching hospital. PATIENTS: From 2,617 admissions to ICU between January 27, 2016, and March 30, 2017, 1,262 consecutive patients who met inclusion and exclusion criteria were studied. INTERVENTIONS: Glycosylated hemoglobin was used to estimate average glucose concentration over the prior 3 months. Glucose concentration on ICU admission was divided by estimated average glucose concentration to calculate the stress hyperglycemia ratio, an index of relative glycemia. Risk of death score was calculated using data submitted to the Australia and New Zealand Intensive Care Society. MEASUREMENTS AND MAIN RESULTS: In this study, there were 186 deaths (14.7%). Admission glucose was significantly associated with mortality in univariate analysis (odds ratio = 1.08 per mmol/L glucose increment; p < 0.001) but not after adjustment for risk of death score (odds ratio = 1.01; p = 0.338). In contrast, stress hyperglycemia ratio was significantly associated with mortality both in univariate analysis (odds ratio = 1.09 per 0.1 stress hyperglycemia ratio increment; p < 0.001) and after adjustment for risk of death score (odds ratio = 1.03; p = 0.014). Unlike admission glucose concentration, stress hyperglycemia ratio was significantly associated with mortality in patients with glycosylated hemoglobin less than 6.5% (odds ratio = 1.08 per 0.1 stress hyperglycemia ratio increment; p < 0.001) and glycosylated hemoglobin greater than or equal to 6.5% (48 mmol/mol) (odds ratio = 1.08 per 0.1 stress hyperglycemia ratio increment; p = 0.005). CONCLUSIONS: Unlike absolute hyperglycemia, relative hyperglycemia, as assessed by the stress hyperglycemia ratio, independently predicts in-hospital mortality in critically ill patients across the glycemic spectrum. Future studies should investigate whether using measures of relative hyperglycemia to determine individualized glycemic treatment targets improves outcomes in ICU.

Relative hyperglycemia is associated with complications following an acute myocardial infarction: a post-hoc analysis of HI-5 data.

BACKGROUND: Hyperglycemia is associated with increased morbidity and mortality in patients with an acute myocardial infarction (AMI). We evaluated whether complications after AMI are associated with absolute or relative glycemia. METHODS: A total of 192 patients with AMI were randomized to intensive or conventional insulin therapy. Absolute glycemia was defined as mean blood glucose level (BGL) during the first 24 h following randomization. Relative glycemia was defined by the stress hyperglycaemia ratio (SHR), calculated as mean BGL divided by average glucose concentration over the prior 3 months estimated from glycosylated haemoglobin. The primary endpoint was a "complicated AMI", defined as an AMI complicated by death, congestive cardiac failure, arrhythmia, cardiac arrest, reinfarction, cardiogenic shock, inotrope use or emergency revascularization. RESULTS: There was not a significant association between mean BGL and complicated AMI (odds ratio (OR) 1.05 per mmol/L glucose increment, 95% confidence intervals (CI) 0.93-1.19). In contrast, SHR was positively associated with a complicated myocardial infarction (OR 1.22 per 0.1 SHR increment, 95% CI 1.06-1.42), and individual complications of death (OR 1.55, 95% CI 1.14-2.11), congestive cardiac failure (OR 1.27, 95% CI 1.05-1.54), arrhythmia (OR 1.31, 95% CI 1.12-1.54) and cardiogenic shock (OR 1.42, 95% CI 1.03-1.97). The relationship between SHR and a complicated AMI was independent of diabetic status, intensive insulin therapy, sex and hypoglycemia. CONCLUSIONS: Relative, but not absolute, glycemia during insulin treatment is independently associated with complications after an AMI. Future studies should investigate whether basing therapeutic glycaemic targets on relative glycemia improves patient outcomes.

Does hyperglycemia affect arginine metabolites in critically ill patients? A prospective cohort and in vitro study.

BACKGROUND: Changes in the arginine metabolites asymmetric dimethyl-L-arginine (ADMA) and L-homoarginine and acute blood glucose concentrations have been shown to cause endothelial dysfunction and be independently associated with mortality in Intensive Care Unit (ICU) patients. The aim of this study was to investigate whether hyperglycemia potentially modulates these arginine metabolite concentrations to provide a mechanism that may link hyperglycemia and mortality in this patient group. METHODS: A clinical and in vitro study were undertaken. Glucose, glycosylated hemoglobin-A1c (HbA1c) and the stress hyperglycemia ratio (SHR) (to quantify absolute, chronic and relative hyperglycemia respectively) were measured in 1155 acutely unwell adult patients admitted to a mixed medical-surgical ICU. SHR was calculated by dividing the admission glucose by the estimated average glucose over the last 3 months, which was derived from HbA1c. ADMA and L-homoarginine were measured in a plasma sample collected at admission to ICU by liquid chromatography tandem mass spectrometry. The activity of dimethylarginine-dimethylaminohydrolase 1 (DDAH1), the main enzyme regulating ADMA concentrations, was assessed at varying glucose concentrations in vitro by quantifying the conversion of ADMA to citrulline in HEK293 cells that overexpress DDAH1. RESULTS: In the clinical study, plasma ADMA was not significantly associated with any measure of hyperglycemia. L-homoarginine was positively associated with glucose (ß = 0.067, p = 0.018) and SHR (ß = 0.107, p < 0.001) after correction for glomerular filtration rate. However, as L-homoarginine is a negative predictor of mortality, the direction of these associations are the opposite of those expected if hyperglycemia was affecting mortality via changes in L-homoarginine. In vitro DDAH1 activity was not significantly influenced by glucose concentrations (p = 0.506). CONCLUSION: In critically ill patients the association between relative hyperglycemia and mortality is not mediated by changes in ADMA or L-homoarginine. Trial registration ANZCTR Trial ID ACTRN12615001164583.