BUN as a risk factor for mortality after coronary artery bypass grafting

Blood Urea Nitrogen-to-Albumin Ratio in Predicting Long-Term Mortality in Patients Following Coronary Artery Bypass Grafting: An Analysis of the MIMIC-III Database

Background

This study examined the role of blood urea nitrogen-to-albumin ratio (BAR) in predicting long-term mortality in patients undergoing coronary artery bypass grafting (CABG).

Methods

In this retrospective cohort study, patients undergoing CABG were enrolled from the Medical Information Mart for Intensive Care III (MIMIC III) database. Patients were divided into the three groups according to the optimal cutoff values of BAR determined by X-tile software. The survival curve was constructed by the Kaplan–Meier method and multivariate Cox regression analysis was performed to explore the independent prognostic factors of 1- and 4-year mortality after CABG. The receiver operating characteristic (ROC) curves and the areas under the ROC curves (AUCs) were calculated to estimate the accuracy of BAR in predicting the outcomes. Subgroup analyses were also carried out.

Results

A total of 1,462 patients at 4-year follow-up were included, of which 933, 293, and 236 patients were categorized into the group 1 (≤ 6.45 mg/g), group 2 (>6.45 and ≤ 10.23 mg/g), and group 3 (>10.23 mg/g), respectively. Non-survivors showed an increased level of BAR at both 1- (p < 0.001) and 4-year (p < 0.001) follow-up compared with the survivors. The patients with a higher BAR had a higher risk of 1- and 4-year mortality following CABG (33.05 vs. 14.33 vs. 5.14%, p < 0.001 and 52.97 vs. 30.72 vs. 13.08%, p < 0.001, respectively). Cox proportional hazards regression model suggested a higher BAR as an independent risk factor of 1-year mortality (HR 3.904; 95% CI 2.559–5.956; P < 0.001) and 4-year mortality (HR 2.895; 95% CI 2.138–3.921; P < 0.001) after adjusting for confounders. Besides, the receiver operating characteristic (ROC) curves showed the better predictive ability of BAR compared to other grading scores at both 1- (0.7383, 95% CI: 0.6966–0.7800) and 4-year mortality (0.7189, 95% CI: 0.6872–0.7506). Subgroup analysis demonstrated no heterogeneous results of BAR in 4-year mortality in particular groups of patient.

Conclusion

This report provided evidence of an independent association between 1- and 4-year mortality after CABG and BAR. A higher BAR was associated with a higher risk of long-term mortality and could serve as a prognostic predictor in patients following CABG.

Prognostic Value of Blood Urea Nitrogen/Creatinine Ratio for Septic Shock: An Analysis of the MIMIC-III Clinical Database

Background

Research has previously been done into the risk factors for mortality in septic shock patients. However, there has been no epidemiological study investigating the effect of the blood urea nitrogen/creatinine ratio (BCR) on the prognosis of critically ill septic shock patients. This study is aimed at determining the relationship between BCR and all-cause mortality in adult septic shock patients.

Methods

Data were extracted from the MIMIC-III database. The clinical endpoints were 28-, 90-, and 365-day all-cause mortality rates in critically ill septic shock patients. Cox proportional hazards models and subgroup analyses were used to analyze the relationship between BCR quartiles and all-cause mortality in septic shock patients. Receiver operator characteristic (ROC) curves and areas under the ROC curves (AUCs) were calculated to evaluate how accurately BCR predicts the mortality of septic shock patients.

Results

Among the 2484 septic shock patients extracted from the database, 619, 563, 677, and 625 fell into the first (<14.4 mg/dL), second (≥14.4 mg/dL and <20.0 mg/dL), third (≥20.0 mg/dL and <27.3 mg/dL), and fourth (≥27.3 mg/dL) quartiles of BCR, respectively. Male and white patients accounted for 53.8% (1336 patients) and 74.8% (1857 patients) of the population, respectively. The mean age of the population was 67.7 ± 15.8 years. An inverse M-shaped relationship between BCR and mortality in septic shock patients was identified, with a value of ≥27.3 mg/dL providing the highest risk (HR = 1.596, 95% CI: 1.396-1.824, P < 0.001). In the Cox regression model adjusted for different confounding variables, BCR values in the fourth quartiles were significantly associated with increased mortality, using the first quartiles as a reference. The areas under the ROC curves (AUCs) for BCR plus the Sequential Organ Failure Assessment (SOFA) score and BCR plus Acute Physiology Score III (APSIII) were 0.694 (95% CI: 0.673-0.716) and 0.724 (95% CI: 0.703-0.744), respectively.

Conclusion

An inverse M-shaped curve was determined between BCR and the mortality of septic shock patients. BCR was identified as a readily available and independent prognostic biomarker for septic shock patients, and higher BCRs were associated with increased mortality in these patients.

Blood urea nitrogen is associated with long-term all-cause mortality in stable angina pectoris patients: 8-year follow-up results

Background    Elevation of blood urea nitrogen (BUN) indicates renal dysfunction and is associated with increased mortality in cardiovascular diseases. We investigated the relationship between the BUN concentration measured at hospital admission and the long-term all-cause mortality in patients with stable angina pectoris (SAP).Methods    The mortality rate of 344 patients who underwent coronary angiography (CAG) in our clinic due to SAP was analyzed during a mean follow-up period of 8 yrs.Results    Age (p&lt;0.001), male gender (p=0.020), waist circumference (p=0.007), body-mass index (p=0.002), fasting glucose (p=0.004), BUN (p&lt;0.001), serum creatinine (Cr) (p&lt;0.001), hemoglobin (p=0.015), triglyceride concentrations (p=0.033), and the Gensini score (p&lt;0.001) were related to all-cause mortality as shown by univariate Cox regression analysis. Age (OR 1.056, 95 % CI 1.015-1.100, p=0.008), fasting glucose (OR 1.006, 95 % CI 1.001-1.011, p=0.018), BUN, (OR 1.077, 95 % CI 1.026-1.130, p=0.003), and the Gensini score (OR 2.269, 95 % CI 1.233-4.174, p=0.008) were significantly related with mortality as shown by multivariate Cox regression analysis. According to receiver operating characteristic analysis ofthe sensitivity and specificity of BUN and Cr for predicting mortality, the area under the curve values of BUN and Cr were 0.789 (p&lt;0.001) and 0.652 (p=0.001), respectively. BUN had a stronger relationship with mortality than Cr. A concentration of BUN above 16.1 mg / dl had 90.1 % sensitivity and 60 % specificity for predicting mortality (OR=2.23).Conclusion    In patients who underwent CAG due to SAP, the BUN concentration was associated with all-cause mortality during a mean follow-up period of 8 yrs.

Preoperative blood urea nitrogen-to-left ventricular ejection fraction ratio is an independent predictor of long-term major adverse cardiac events in patients undergoing coronary artery bypass grafting surgery

Background

Long-term mortality rate following coronary artery bypass grafting (CABG) procedure is still considered to be high despite advances in surgical techniques and perioperative management. Identifying high-risk patients by using cost-effective and clinically useful parameters is needed.

Methods

Patients who were admitted to our cardiology clinic with the diagnosis of coronary artery disease and underwent CABG between January 2008 and August 2010 were included. Study patients were followed-up for 112.6 ± 17.8 months for major adverse cardiac events (MACE) which were defined as all-cause mortality and new-onset decompensated heart failure (HF).

Results

Patients in MACE (+) group were older (p < 0.001), had higher additive Euroscore (p < 0.001), and lower left ventricular ejection fraction (p < 0.001). Multivariate Cox regression analysis showed that additive Euroscore [odds ratio (OR) = 1.601; 95% confidence interval (CI) = 1.374–1.864; p < 0.001)] and blood urea nitrogen-to-left ventricular ejection fraction ratio (BUNEFr; OR = 1.028; 95% CI = 1.006–1.050; p = 0.011) independently predicted MACE. Receiver operating characteristic curve analysis demonstrated that BUNEFr had an area under curve of 0.794 and BUNEFr >33 had a sensitivity and specificity of 74% and 64%, respectively.

Conclusion

BUNEFr is a clinically useful and cost-effective parameter for the prediction of long-term mortality and new-onset decompensated HF in patients undergoing CABG.

A multidisciplinary consensus on dehydration: definitions, diagnostic methods and clinical implications

Background: Dehydration appears prevalent, costly and associated with adverse outcomes. We sought to generate consensus on such key issues and elucidate need for further scientific enquiry. Materials and methods: A modified Delphi process combined expert opinion and evidence appraisal. Twelve relevant experts addressed dehydration's definition, objective markers and impact on physiology and outcome. Results: Fifteen consensus statements and seven research recommendations were generated. Key findings, evidenced in detail, were that there is no universally accepted definition for dehydration; hydration assessment is complex and requires combining physiological and laboratory variables; "dehydration" and "hypovolaemia" are incorrectly used interchangeably; abnormal hydration status includes relative and/or absolute abnormalities in body water and serum/plasma osmolality (pOsm); raised pOsm usually indicates dehydration; direct measurement of pOsm is the gold standard for determining dehydration; pOsm >300 and ≤280 mOsm/kg classifies a person as hyper or hypo-osmolar; outside extremes, signs of adult dehydration are subtle and unreliable; dehydration is common in hospitals and care homes and associated with poorer outcomes. Discussion: Dehydration poses risk to public health. Dehydration is under-recognized and poorly managed in hospital and community-based care. Further research is required to improve assessment and management of dehydration and the authors have made recommendations to focus academic endeavours. Key messages Dehydration assessment is a major clinical challenge due to a complex, varying pathophysiology, non-specific clinical presentations and the lack of international consensus on definition and diagnosis. Plasma osmolality represents a valuable, objective surrogate marker of hypertonic dehydration which is underutilized in clinical practice. Dehydration is prevalent within the healthcare setting and in the community, and appears associated with increased morbidity and mortality.

Urea

Urea is generated by the urea cycle enzymes, which are mainly in the liver but are also ubiquitously expressed at low levels in other tissues. The metabolic process is altered in several conditions such as by diets, hormones, and diseases. Urea is then eliminated through fluids, especially urine. Blood urea nitrogen (BUN) has been utilized to evaluate renal function for decades. New roles for urea in the urinary system, circulation system, respiratory system, digestive system, nervous system, etc., were reported lately, which suggests clinical significance of urea.

The meaning of the blood urea nitrogen/creatinine ratio in acute kidney injury

Background.

A blood urea nitrogen (BUN)/creatinine ratio (BCR) >20 (0.081 in international unit) is used to distinguish pre-renal azotemia (PRA) and acute tubular necrosis (ATN). However, there is little evidence that BCR can distinguish between these two conditions and/or is clinically useful.

Methods.

We conducted a retrospective study using a large hospital database. Patients were divided into three groups: ‘low BCR’ (if BCR when acute kidney injury (AKI) developed was ≤20), ‘high BCR’ (if BCR when AKI developed was >20) and ‘no AKI’ if patients did not satisfy any of the Risk, Injury, Failure, Loss and End-stage kidney disease criteria for AKI during hospitalization.

Results.

Among 20 126 study patients, 3641 (18.1%) had AKI. Among these patients, 1704 (46.8%) had a BCR <20 at AKI diagnosis (‘low BCR’) and 1937 (53.2%) had a BCR >20 (‘high BCR’). The average BCR for the two groups was 15.8 versus 26.1 (P < 0.001). Hospital mortality was significantly less in the ‘low-BCR’ group (18.4 versus 29.9%, P < 0.001). Multivariable logistic regression analysis for hospital mortality (‘no AKI’ as a reference) showed that the odds ratio of ‘high BCR’ (5.73) was higher than that of ‘low BCR’ (3.32).

Conclusions.

Approximately half of the patients with AKI have a BCR >20, the traditional threshold of diagnosing PRA. Unlike PRA patients who have a lower mortality than ATN patients, high BCR patients had higher hospital mortality compared with low BCR patients, which was confirmed with multivariable analysis. These findings do not support BCR as a marker of PRA.

Elevation of blood urea nitrogen is predictive of long-term mortality in critically ill patients independent of "normal" creatinine

OBJECTIVE

We hypothesized that elevated blood urea nitrogen can be associated with all-cause mortality independent of creatinine in a heterogeneous critically ill population.

DESIGN

Multicenter observational study of patients treated in medical and surgical intensive care units.

SETTING

Twenty intensive care units in two teaching hospitals in Boston, MA.

PATIENTS

A total of 26,288 patients, age ≥ 18 yrs, hospitalized between 1997 and 2007 with creatinine of 0.80-1.30 mg/dL.

INTERVENTIONS

None.

MEASUREMENTS

Blood urea nitrogen at intensive care unit admission was categorized as 10-20, 20-40, and >40 mg/dL. Logistic regression examined death at days 30, 90, and 365 after intensive care unit admission as well as in-hospital mortality. Adjusted odds ratios were estimated by multivariable logistic regression models.

MAIN RESULTS

Blood urea nitrogen at intensive care unit admission was predictive for short- and long-term mortality independent of creatinine. Thirty days following intensive care unit admission, patients with blood urea nitrogen of >40 mg/dL had an odds ratio for mortality of 5.12 (95% confidence interval, 4.30-6.09; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Blood urea nitrogen remained a significant predictor of mortality at 30 days after intensive care unit admission following multivariable adjustment for confounders; patients with blood urea nitrogen of >40 mg/dL had an odds ratio for mortality of 2.78 (95% confidence interval, 2.27-3.39; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Thirty days following intensive care unit admission, patients with blood urea nitrogen of 20-40 mg/dL had an odds ratio of 2.15 (95% confidence interval, 1.98-2.33; <.0001) and a multivariable odds ratio of 1.53 (95% confidence interval, 1.40-1.68; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Results were similar at 90 and 365 days following intensive care unit admission as well as for in-hospital mortality. A subanalysis of patients with blood cultures (n = 7,482) demonstrated that blood urea nitrogen at intensive care unit admission was associated with the risk of blood culture positivity.

CONCLUSION

Among critically ill patients with creatinine of 0.8-1.3 mg/dL, an elevated blood urea nitrogen was associated with increased mortality, independent of serum creatinine.

The 2003 heat wave in France: hydratation status changes in older inpatients

Little is known about the impact of behavioral changes after the 2003 heat wave on hydration status of elderly citizens in France. We used an administrative data file provided information about 23,022 inpatients aged > or =70 years admitted between 2000 and 2006, including vital status at discharge and Charlson comorbidity index and matched it with the result of five blood tests (sodium, potassium, glucose, urea nitrogen, creatinine) within the first 24 h after admission and with daily temperatures before admission. We then measured the prevalence of plasma tonicity (PT) <275 mOsm/l or >300 mOsm/l, blood urea nitrogen/creatinine ratio (BUNC) >100 and inhospital mortality. In 2000-2002, 2003, 2004-2006, prevalence (%) was, respectively 7.5, 8.0, 9.5 (P < 0.0001) for PT < 275 mMol/l, 8.4, 10.4, 7.2 (P < 0.0001) for PT > 300 mOsm/l, and 35.4, 30.7, 26.7 (P < 0.0001) for BUNC > 100. Inhospital mortality rate was 10.8, 10.8 and 9.0%, respectively (P < 0.0001). After adjustment for covariates, OR (95% CI) in 2004-2006 with reference to 2000-2002 was 1.26 (1.13-1.39) for PT < 275 mMol/l, 0.85 (0.76-0.94) for PT > 300 mOsm/l, and 0.65 (0.61-0.69) for BUNC > 100. Inhospital mortality risk associated with hydration disorders did not vary significantly over periods for PT < 275 mMol/l (HR 1.06 to 1.40) and PT > 300 mOsm/l (HR 1.76 to 1.96) but was lower for BUNC > 100 in 2003 (HR 1.27) than in 2000-2002 (HR 1.64) or 2004-2006 (HR 1.77) (P = 0.04). So, since the 2003 heat wave, significant shifts in prevalence of intracellular hydration disorders indicate behavioral changes with positive impact on hydration status.

Relation of blood urea nitrogen to long-term mortality in patients with heart failure

Patients with chronic kidney disease and heart failure (HF) have been shown to be at higher risk for major adverse cardiovascular events and death. Recent studies have demonstrated that blood urea nitrogen (BUN) might serve as a powerful predictor of mortality in acutely decompensated HF. The goal of this study was to determine the impact of BUN on long-term mortality in patients with stage B and C HF. Our retrospective analysis included patients undergoing percutaneous intervention with a calculated left ventricular ejection fraction < or =50%. Patients on dialysis or with technically inadequate left ventriculograms were excluded. Chart review was performed and mortality data were obtained. Our population included 444 patients with a mean ejection fraction of 38 +/- 10%, mean age of 59 +/- 11 years, median BUN of 14 mg/dl, and median glomerular filtration rate (GFR) of 81 ml/min/1.73 m(2); 31% had stage C HF, and 33% died during follow-up. Patients with increased BUN (> or =17 mg/dl) and decreased GFR (< or =69 ml/min/1.73 m(2)) had significantly increased long-term mortality on Kaplan-Meier analysis (8-year mortalities of 57% and 55%, respectively). In patients with stage C HF, mortalities at 8 years were 69% and 73% with abnormal BUN and GFR, respectively. Proportional hazard regression analysis demonstrated that BUN and stage C HF were independently associated with increased mortality, whereas GFR was not. In conclusion, we demonstrated that BUN is strongly associated with mortality in patients with stage B and C HF and may serve as a better biomarker than GFR for prognostication.

Mortalité hospitalière et durée de séjour des patients non programmés en médecine interne: valeur pronostique de paramètres biochimiques usuels à l'admission

PURPOSE

Little is known about prognosis values of biochemical markers in internal medicine patients. We have examined retrospectively the relationship between inhospital mortality or stay duration and several biochemical markers commonly performed on admission in internal medicine patients.

METHODS

Among all stays unplanned in our department during the year 2004, we collected data about 8 blood biochemical markers (sodium, potassium, chloride, bicarbonate, anion gap, urea nitrogen, creatinin, proteins), performed between the day before and the day after admission. Mixed Cox regression models computed hazard ratios for mortality associated with biochemical markers concentration. The relationship between biochemical markers concentration and duration stay was investigated in mixed linear regression models.

RESULTS

In 2004 our department totalized 1199 unplanned stays by 1054 distinct patients (age: 69.9+/-19.2 y, women: 59.2%), among which 59 deceased during stay. Biochemical markers were available for 977 (81.5%) stays (stay duration: 17.5+/-16.0 days). Inhospital mortality was significantly associated with plasma concentration on admission of potassium, proteins, anion gap and with urea nitrogen/creatinin ratio. Among survivors, duration stay was significantly associated with plasma concentration on admission of sodium, chlore, and anion gap.

CONCLUSION

Biochemical markers performed on admission need particular attention as they provide immediate information about short term prognosis of internal medicine patients.

Does renal dysfunction predict mortality after acute stroke? A 7-year follow-up study

BACKGROUND AND PURPOSE

The purpose of this study was to investigate renal function as a long-term predictor of mortality in patients hospitalized for acute stroke.

METHODS

This was a cohort study done in a Scottish tertiary teaching hospital. Participants included 2042 (993 male) unselected consecutive stroke patients (mean age, 73 years) admitted to hospital within 48 hours of stroke between 1988 and 1994. Follow-up was up to 7 years. Main outcome measure was all-cause mortality.

RESULTS

The total number of deaths at the end of follow-up was 1026. Most subjects (1512) had creatinine <124 micromol/L. The mean calculated creatinine clearance was 54.8 mL/min (SD, 23 mL/min). Renal function indexes were analyzed by quartiles with Cox proportional-hazards model. Stroke survivors had higher calculated creatinine clearance and lower serum creatinine, urea, and ratios of urea to creatinine. Calculated creatinine clearance > or =51.27 mL/min significantly predicted better long-term survival in these stroke patients even after adjustment for confounders (age, neurological score, ischemic heart disease, hypertension, smoking, and diuretic use). Similarly, creatinine > or =119 micromol/L "relative risk (RR), 1.59; 95% confidence interval (CI), 1.32 to 1.92", urea 6.8 to 8.9 mmol/L (RR, 1.34; 95% CI, 1.09 to 1.65) or > or =9 mmol/L (RR, 1.74; 95% CI, 1.42 to 2.13), and ratio of urea to creatinine > or =0.08573 mmol/micromol (RR, 1.24; 95% CI, 1.03 to 1.50) remained significant predictors of mortality after adjustment for confounders.

CONCLUSIONS

After acute stroke, patients with reduced admission calculated creatinine clearance, raised serum creatinine and urea concentrations (even within conventional reference intervals), and raised ratio of urea to creatinine had a higher mortality risk. This finding may be used to stratify risk and target interventions, eg, the use of angiotensin-converting enzyme inhibitors.

Atrial natriuretic peptide level contributes to a model of future mortality in the oldest old

OBJECTIVES

To determine if atrial natriuretic peptide (ANP) level is associated with mortality in the oldest old and to develop a comprehensive model of mortality in the oldest old using clinical and laboratory parameters.

DESIGN

Prospective cohort study with 7 years of follow-up.

SETTING

A 725-bed life care facility.

PARTICIPANTS

282 frail older individuals (mean age 88, range 70-102).

MEASUREMENTS

Variables measured included age, gender, Charlson Comorbidity Index, functional measurements, weight, blood pressure, and multiple laboratory variables, including ANP. Main outcome measurement was death.

RESULTS

Eighty-four percent (237/282) of subjects died during the 7-year follow-up period. On univariate analysis, the risk ratio (RR) for ANP tertile was 1.28. On bivariate analysis, adjusting for the development of congestive heart failure, the RR was 1.22. On multivariate analysis, the following variables were associated with mortality: ANP tertile (RR 1.24), age (RR 1.04), female gender (RR 0.43), Charlson Comorbidity Index score (RR 1.13), mentation score (RR 1.27), BUN/Cr ratio (RR 1.04), albumin level (RR 0.63), and hemoglobin level (RR 0.84).

CONCLUSIONS

ANP level and other variables are independent risk factors for mortality in frail individuals. ANP level may indicate homeostatic failure to adapt to fluid volume changes or may reflect subclinical heart disease. ANP level contributes to a multivariate model of mortality in frail older individuals.

Use of postoperative information to predict mortality rates for patients who have long stays in the intensive care unit after coronary artery bypass grafting

OBJECTIVE

To derive and evaluate prediction models for patients who had undergone coronary artery bypass grafting (CABG) and had a difficult postoperative course.

DESIGN

Observational.

SETTING

Midwestern hospital specializing in high-risk CABG procedures.

PATIENTS

One hundred eighty-three patients who stayed at least 10 consecutive days in the intensive care unit after a CABG procedure.

OUTCOME MEASURE

Death within 60 days of surgery.

INTERVENTION

None.

RESULTS

The final logistic regression prediction models included the following findings: pulmonary capillary wedge pressure, cardiac index, heart rate, urine output, positive end-expiratory pressure, blood urea nitrogen levels, and the arterial pressure of carbon dioxide. The model was able to stratify patients into four risk groups with observed 60-day mortality rates of 0.0% (n = 107), 21% (n = 39), 55% (n = 20), and 88% (n = 17). Preoperative patient information was not associated with prognosis for these patients.

CONCLUSIONS

The findings suggest that a risk model that is specific for patients who have undergone CABG and is based on postoperative findings may provide useful prognostic information for patients who are having a difficult postoperative course.