The influence of postoperative albumin levels on the outcome of cardiac surgery.

BACKGROUND: The prognostic role of low postoperative serum albumin levels (SAL) after cardiac surgery (CS) remains unclear in patients with normal preoperative SAL. Our aim was to evaluate the influence of SAL on the outcome of CS. METHODS: Prospective observational study. Patients undergoing CS with normal preoperative SAL and nutritional status were included and classified into different subgroups based on SAL at 24 h after CS. We assessed outcomes (i.e., in-hospital mortality, postoperative complications and long-term survival) and results were analyzed among the different subgroups of SAL. RESULTS: We included 2818 patients. Mean age was 64.5 ± 11.6 years and body mass index 28.0 ± 4.3Kg·m- 2. 5.8%(n = 162) of the patients had normal SAL levels(≥35 g·L- 1), 32.8%(n = 924) low deficit (30-34.9 g·L- 1), 44.3%(n = 1249) moderate deficit (25-29.9 g·L- 1), and 17.1%(n = 483) severe deficit(< 25 g·L- 1). Higher SAL after CS was associated with reduced in-hospital (OR:0.84;95% CI:0.80-0.84; P = 0.007) and long-term mortality (HR:0.85;95% CI:0.82-0.87;P < 0.001). Subgroups of patients with lower SAL showed worst long-term survival (5-year mortality:94.3% normal subgroup, 87.4% low, 83.1% moderate and 72.4% severe;P < 0.001). Multivariable analysis showed higher in-hospital mortality, sepsis, hemorrhage related complications, and ICU stay in subgroups of patients with lower SAL. Predictors of moderate and severe hypoalbuminemia were preoperative chronic kidney disease, previous CS, and longer cardiopulmonary bypass time. CONCLUSIONS: The presence of postoperative hypoalbuminemia after CS is frequent and the degree of hypoalbuminemia may be associated with worst outcomes, even in the long-term scenario.

Five-year mortality in cardiac surgery patients with low cardiac output syndrome treated with levosimendan: prognostic evaluation of NT-proBNP and C-reactive protein.

BACKGROUND: To determine the clinical risk factors predictive of the 5-year mortality in patients with low cardiac output syndrome (LCOS) after cardiac surgery. In addition, to assess the influence of inflammation and myocardial dysfunction severity, as measured by C-reactive protein (CRP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations, on outcome. METHODS: We studied 30 patients who underwent cardiac surgery and developed postoperative LCOS requiring inotropic support for longer than 48 hours after intensive care unit (ICU) admission. All patients received a 24-hour infusion of levosimendan after study enrolment. We measured the following at baseline, 24 h, 48 h and 7 days: clinical data, serum NT-proBNP and serum CRP levels. Patients were followed-up at 5 years for death by any cause. A risk-adjusted Cox proportional hazards regression model was used for statistical analysis. Hazard ratios and their 95% confidence intervals (CI) are presented. RESULTS: The 5-year mortality was 36.6% (n.=11). The predictors of 5-year mortality were the presence of dilated cardiomyopathy (HR=36.909; 95% CI: 1.901-716.747; P=0.017), a higher central venous pressure (CVP) at 48 hours (HR=2.686; 95% CI: 1.383-5.214; P=0.004), and lower CRP levels on day 7 (HR=0.963; 95% CI: 0.933-0.994; P=0.021). NT-proBNP levels showed a trend to higher initial levels in survivors without statistical significance, but were not associated with 5-year mortality. CONCLUSIONS: The presence of dilated cardiomyopathy, elevated CVP at 48 h and reduced CRP levels on day 7 predicted 5-year mortality in patients who developed postoperative LCOS after cardiac surgery. NT-proBNP levels in the first postoperative week were not predictors of long-term outcomes.

Evaluation of Serial Arterial Lactate Levels as a Predictor of Hospital and Long-Term Mortality in Patients After Cardiac Surgery.

OBJECTIVES: Although hyperlactatemia is common after cardiac surgery, its value as a prognostic marker is unclear. The aim of the present study was to determine whether postoperative serial arterial lactate (AL) measurements after cardiac surgery could predict outcome. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit in a tertiary-level university hospital. PARTICIPANTS: Participants included 2,935 consecutive patients. INTERVENTIONS: AL was measured on admission to the intensive care unit and 6, 12, and 24 hours after surgery, and evaluated together with clinical data and outcomes including in-hospital and long-term mortality. MEASUREMENTS AND MAIN RESULTS: In-hospital and long-term mortality (mean follow-up 6.3±1.7 years) were 5.9% and 8.7%, respectively. Compared with survivors, nonsurvivors showed higher mean AL values in all measurements (p<0.001). Hyperlactatemia (AL>3.0 mmol/L) was a predictor for in-hospital mortality (odds ratio = 1.468; 95% confidence interval = 1.239-1.739; p<0.001) and long-term mortality (hazard ratio = 1.511; 95% confidence interval = 1.251-1.825; p<0.001). Recent myocardial infarction and longer cardiopulmonary bypass time were predictors of hyperlactatemia. The pattern of AL dynamics was similar in both groups, but nonsurvivors showed higher AL values, as confirmed by repeated measures analysis of variance (p<0.001). The area under the curve also showed higher levels of AL in nonsurvivors (80.9±68.2 v 49.71±25.8 mmol/L/h; p = 0.038). Patients with hyperlactatemia were divided according to their timing of peak AL, with higher mortality and worse survival in patients in whom AL peaked at 24 hours compared with other groups (79.1% v 86.7%-89.2%; p = 0.03). CONCLUSIONS: The dynamics of the postoperative AL curve in patients undergoing cardiac surgery suggests a similar mechanism of hyperlactatemia in survivors and nonsurvivors, albeit with a higher production or lower clearance of AL in nonsurvivors. The presence of a peak of hyperlactatemia at 24 hours is associated with higher in-hospital and long-term mortality.

The inflammatory response in cardiac surgery: an overview of the pathophysiology and clinical implications.

During cardiac surgery different factors, such as the aortic clamp, the extracorporeal circulation and the surgical injury itself, produce complex inflammatory responses which can lead to varying degrees of ischemia-reperfusion injury and/or systemic inflammatory response. This may have clinical implications due to hemodynamic changes related with an enlarged vasodilatory response. Thus, maintaining adequate levels of blood pressure during and after cardiac surgery represents a challenge for physicians when inflammatory response appears. The use of noradrenaline to raise arterial pressure is the most current pharmacological approach in the operating room and ICU. However, it is not always effective and other drugs, such as methylene blue, have to be used among others in specific cases as rescue therapy. The aim of our research is to review briefly the pathophysiology and clinical implications in the treatment of the inflammatory response in cardiac surgery, together with the mechanisms involved in those treatments.

Influence of cirrhosis in cardiac surgery outcomes.

Liver cirrhosis has evolved an important risk factor for cardiac surgery due to the higher morbidity and mortality that these patients may suffer compared with general cardiac surgery population. The presence of contributing factors for a poor outcome, such as coagulopathy, a poor nutritional status, an adaptive immune dysfunction, a degree of cirrhotic cardiomyopathy, and a degree of renal and pulmonary dysfunction, have to be taken into account for surgical evaluation when cardiac surgery is needed, together with the degree of liver disease and its primary complications. The associated pathophysiological characteristics that liver cirrhosis represents have a great influence in the development of complications during cardiac surgery and the postoperative course. Despite the population of cirrhotic patients who are referred for cardiac surgery is small and recommendations come from small series, since liver cirrhotic patients have increased their chance of survival in the last 20 years due to the advances in their medical care, which includes liver transplantation, they have been increasingly considered for cardiac surgery. Indeed, there is an expected rise of cirrhotic patients within the cardiac surgical population due to the increasing rates of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, especially in western countries. In consequence, a more specific approach is needed in the assessment of care of these patients if we want to improve their management. In this article, we review the pathophysiology and outcome prediction of cirrhotic patients who underwent cardiac surgery.

The influence of body mass index on outcomes in patients undergoing cardiac surgery: does the obesity paradox really exist?

PURPOSE: Obesity influences risk stratification in cardiac surgery in everyday practice. However, some studies have reported better outcomes in patients with a high body mass index (BMI): this is known as the obesity paradox. The aim of this study was to quantify the effect of diverse degrees of high BMI on clinical outcomes after cardiac surgery, and to assess the existence of an obesity paradox in our patients. METHODS: A total of 2,499 consecutive patients requiring all types of cardiac surgery with cardiopulmonary bypass between January 2004 and February 2009 were prospectively studied at our institution. Patients were divided into four groups based on BMI: normal weight (18.5-24.9 kg∙m-2; n = 523; 21.4%), overweight (25-29.9 kg∙m-2; n = 1150; 47%), obese (≥ 30-≤ 34.9 kg∙m-2; n = 624; 25.5%) and morbidly obese (≥ 35kg∙m-2; n = 152; 6.2%). Follow-up was performed in 2,379 patients during the first year. RESULTS: After adjusting for confounding factors, patients with higher BMI presented worse oxygenation and better nutritional status, reflected by lower PaO2/FiO2 at 24h and higher albumin levels 48 h after admission respectively. Obese patients showed a higher risk for Perioperative Myocardial Infarction (OR: 1.768; 95% CI: 1.035-3.022; p = 0.037) and septicaemia (OR: 1.489; 95% CI: 1.282-1.997; p = 0.005). In-hospital mortality was 4.8% (n = 118) and 1-year mortality was 10.1% (n = 252). No differences were found regarding in-hospital mortality between BMI groups. The overweight group showed better 1-year survival than normal weight patients (91.2% vs. 87.6%; Log Rank: p = 0.029. HR: 1.496; 95% CI: 1.062-2.108; p = 0.021). CONCLUSIONS: In our population, obesity increases Perioperative Myocardial Infarction and septicaemia after cardiac surgery, but does not influence in-hospital mortality. Although we found better 1-year survival in overweight patients, our results do not support any protective effect of obesity in patients undergoing cardiac surgery.

Evaluation of the PaO2/FiO2 ratio after cardiac surgery as a predictor of outcome during hospital stay.

BACKGROUND: The arterial partial pressure of O2 and the fraction of inspired oxygen (PaO2/FiO2) ratio is widely used in ICUs as an indicator of oxygenation status. Although cardiac surgery and ICU scores can predict mortality, during the first hours after cardiac surgery few instruments are available to assess outcome. The aim of this study was to evaluate the usefulness of PaO2/FIO2 ratio to predict mortality in patients immediately after cardiac surgery. METHODS: We prospectively studied 2725 consecutive cardiac surgery patients between 2004 and 2009. PaO2/FiO2 ratio was measured on admission and at 3 h, 6 h, 12 h and 24 h after ICU admission, together with clinical data and outcomes. RESULTS: All PaO2/FIO2 ratio measurements differed between survivors and non-survivors (p < 0.001). The PaO2/FIO2 at 3 h after ICU admission was the best predictor of mortality based on area under the curve (p < 0.001) and the optimum threshold estimation gave an optimal cut-off of 222 (95% Confidence interval (CI): 202-242), yielding three groups of patients: Group 1, with PaO2/FIO2 > 242; Group 2, with PaO2/FIO2 from 202 to 242; and Group 3, with PaO2/FIO2 < 202. Group 3 showed higher in-ICU mortality and ICU length of stay and Groups 2 and 3 also showed higher respiratory complication rates. The presence of a PaO2/FIO2 ratio < 202 at 3 h after admission was shown to be a predictor of in-ICU mortality (OR:1.364; 95% CI:1.212-1.625, p < 0.001) and of worse long-term survival (88.8% vs. 95.8%; Log rank p = 0.002. Adjusted Hazard ratio: 1.48; 95% CI:1.293-1.786; p = 0.004). CONCLUSIONS: A simple determination of PaO2/FIO2 at 3 h after ICU admission may be useful to identify patients at risk immediately after cardiac surgery.

Influence of acute kidney injury on short- and long-term outcomes in patients undergoing cardiac surgery: risk factors and prognostic value of a modified RIFLE classification.

INTRODUCTION: The development of acute kidney injury (AKI) is associated with poor outcome. The modified RIFLE (risk, injury, failure, loss of kidney function, and end-stage renal failure) classification for AKI, which classifies patients with renal replacement therapy needs according to RIFLE failure class, improves the predictive value of AKI in patients undergoing cardiac surgery. Our aim was to assess risk factors for post-operative AKI and the impact of renal function on short- and long-term survival among all AKI subgroups using the modified RIFLE classification. METHODS: We prospectively studied 2,940 consecutive cardiosurgical patients between January 2004 and July 2009. AKI was defined according to the modified RIFLE system. Pre-operative, operative and post-operative variables usually measured on and during admission, which included main outcomes, were recorded together with cardiac surgery scores and ICU scores. These data were evaluated for association with AKI and staging in the different RIFLE groups by means of multivariable analyses. Survival was analyzed via Kaplan-Meier and a risk-adjusted Cox proportional hazards regression model. A complete follow-up (mean 6.9 ± 4.3 years) was performed in 2,840 patients up to April 2013. RESULTS: Of those patients studied, 14% (n = 409) were diagnosed with AKI. We identified one intra-operative (higher cardiopulmonary bypass time) and two post-operative (a longer need for vasoactive drugs and higher arterial lactate 24 hours after admission) predictors of AKI. The worst outcomes, including in-hospital mortality, were associated with the worst RIFLE class. Kaplan-Meier analysis showed survival of 74.9% in the RIFLE risk group, 42.9% in the RIFLE injury group and 22.3% in the RIFLE failure group (P <0.001). Classification at RIFLE injury (Hazard ratio (HR) = 2.347, 95% confidence interval (CI) 1.122 to 4.907, P = 0.023) and RIFLE failure (HR = 3.093, 95% CI 1.460 to 6.550, P = 0.003) were independent predictors for long-term patient mortality. CONCLUSIONS: AKI development after cardiac surgery is associated mainly with post-operative variables, which ultimately could lead to a worst RIFLE class. Staging at the RIFLE injury and RIFLE failure class is associated with higher short- and long-term mortality in our population.

Short-term independent mortality risk factors in patients with cirrhosis undergoing cardiac surgery.

OBJECTIVES: Cirrhosis represents a serious risk in patients undergoing cardiac surgery. Several preoperative factors identify cirrhotic patients as high risk for cardiac surgery; however, a patient's preoperative status may be modified by surgical intervention and, as yet, no independent postoperative mortality risk factors have been identified in this setting. The objective of this study was to identify preoperative and postoperative mortality risk factors and the scores that are the best predictors of short-term risk. METHODS: Fifty-eight consecutive cirrhotic patients requiring cardiac surgery between January 2004 and January 2009 were prospectively studied at our institution. Forty-two (72%) patients were operated on for valve replacement, 9 (16%) for a CABG and 7 (12%) for both (CABG and valve replacement). Thirty-four (58%) patients were classified as Child-Turcotte-Pugh class A, 21 (36%) as class B and 3 (5%) as class C. We evaluated the variables that are usually measured on admission and during the first 24 h of the postoperative period together with potential operative predictors of outcome, such as cardiac surgery scores (Parsonnet, EuroSCORE), liver scores (Child-Turcotte-Pugh, model for end-stage liver disease, United Kingdom end-stage liver disease score) and ICU scores (acute physiology and chronic health evaluation II and III, simplified acute physiology score II and III, sequential organ failure assessment). RESULTS: Seven patients (12%) died in-hospital, of whom 5 were Child-Turcotte-Pugh class B and 2 class C. Comparing survivors vs non-survivors, univariate analysis revealed that variables associated with short-term outcome were international normalized ratio (1.5 ± 0.24 vs 2.2 ± 0.11, P < 0.0001), presurgery platelet count (171 ± 87 vs 113 ± 52 l nl(-1), P = 0.031), presurgery haemoglobin count (11.8 ± 1.8 vs 10.2 ± 1.4 g dl(-1), P = 0.021), total need for erythrocyte concentrates (2 ± 3.4 vs 8.5 ± 8 units, P < 0.0001), PaO(2)/FiO(2) at 12 h after ICU admission (327 ± 84 vs 257 ± 78, P = 0.04), initial central venous pressure (11 ± 3 vs 16 ± 4 mmHg, P = 0.02) and arterial blood lactate concentration 24 h after admission (1.8 ± 0.5 vs 2.5 ± 1.3 mmol l(-1), P = 0.019). Multivariate analysis identified initial central venous pressure as the only independent factor associated with short-term outcome (P = 0.027). The receiver operating characteristic curve showed that the model for end-stage Liver disease score had a better predictive value for short-term outcome than other scores (AUC: 90.5 ± 4.4%; sensitivity: 85.7%; specificity: 83.7%), although simplified acute physiology score III was acceptable. CONCLUSIONS: We conclude that central venous pressure could be a valuable predictor of short-term outcome in patients with cirrhosis undergoing cardiac surgery. The model for end-stage liver disease score is the best predictor of cirrhotic patients who are at high risk for cardiac surgery. Sequential organ failure assessment and simplified acute physiology score III are also valuable predictors.

Does post-cardiac surgery magnesium supplementation improve outcome?

Hypomagnesemia has been linked with increased morbidity and mortality in critically ill patients. Since the condition is common after cardiopulmonary bypass surgery, the objective of this study was to determine whether magnesium supplementation in the immediate postoperative period may improve outcomes of patients undergoing cardiac surgery with cardiopulmonary bypass. This prospective, randomized, double-blind, placebo-controlled study was conducted in a third-level, cardiac surgery intensive care unit (ICU) at a university hospital. Two hundred and sixteen patients undergoing elective cardiac surgery with cardiopulmonary bypass were randomized to receive either an intravenous bolus of 1.5 g of magnesium sulphate followed by an infusion of 12 g of the same salt in 24 h (105 patients), or placebo (111 patients) administered according to the same schedule as the treatment group. No significant differences were found either in the primary end point (hours of intubation) or in the secondary end points (length of inotropic support, new atrial fibrillation, ventricular tachycardia or ventricular fibrillation, length of intensive care unit stay, or ICU or hospital mortality). Hypomagnesemia was present in 12% of patients on admission to the intensive care unit. The magnesium group had a greater need for pacemaker stimulation. In conclusion, under the conditions of the present study, magnesium supplementation after cardiac surgery with cardiopulmonary bypass does not favourably affect clinical outcomes.

Age and sex differences in perioperative myocardial infarction after cardiac surgery.

We investigate age and sex differences in acute myocardial infarction (AMI) after cardiac surgery in a prospective study of 2038 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass. An age of ≥ 70 years implied changes in the type of AMI from the ST-segment elevation myocardial infarction (STEMI) to non-ST-segment elevation myocardial infarction (non-STEMI). Men were more likely than women to suffer from AMI after cardiac surgery (11.8% vs. 5.6%), as a result of the higher frequency of STEMI (6% of men vs. 1.8% of women; P < 0.001) in both age groups. A troponin-I (Tn-I) peak was significantly higher in patients ≥ 70 years old. In-hospital mortality was higher in patients ≥ 70 (7.3%) than in those < 70 years old (3.3%), because of the increased mortality observed in men with non-AMI (2.1% vs. 6.3%) and women with STEMI (0% vs. 28.6%) and non-STEMI (0% vs. 36.8%, P < 0.05). Old age was associated with a higher frequency of non-STEMI, Tn-I peak, mortality and length of stay in the intensive care unit (ICU). Regardless of age, men more often suffer from AMI (particularly STEMI). AMI in women had a notable impact on excess mortality and ICU stay observed in patients ≥ 70 years of age. Clinical and Tn-I peak differences are expected in relation to age and gender after AMI post-cardiac surgery.

Are there sex-based differences in serum troponin I after cardiac surgery?

OBJECTIVE: To determine whether there are sex-based differences in serum troponin I (TnI) after cardiac surgery with cardiopulmonary bypass. DESIGN: Prospective, observational, cohort study. SETTING: Tertiary cardiac surgery intensive care unit (ICU) at a university hospital. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Serum TnI was measured in samples obtained at ICU admission and 6, 12, 24, and 48 hours later. A total of 761 consecutive patients were studied (444 men and 317 women). The characteristics and results of the different sex subgroups were as follows:A) Coronary bypass: 165 men and 38 women. Age, Parsonnet score, Acute Physiology and Chronic Health Evaluation III score, prevalence of renal failure, intra-aortic balloon use, and the lengths of cardiopulmonary bypass, mechanical ventilation, and ICU stay were similar in the two groups. Body mass index, red-cell transfusion needs, and use of noradrenaline were significantly higher in women, whereas dobutamine requirements were higher in men. Mortality: 3 men (1.6%) vs. 0 women (p = not significant).The TnI peak was slightly, but significantly, higher in men (6.2 +/- 4.9 vs. 4.5 +/- 2.6 microg/L. p < 0.05).B) Valve surgery: 279 men and 279 women. Some significant differences were found: Women were older than men and had higher Parsonnet score and transfusion needs. The other recorded variables were similar. Mitral prosthesis: 62 men and 125 women (p < 0.05). Mitral valvuloplasty: 24 men, 7 women (p < 0.05). Aortic prosthesis: 162 men, 103 women (p < 0.05). Mitral and aortic prosthesis: 31 men and 44 women (p < 0.05). TnI peaks were similar for both sexes in each valve subgroup. Mortality: 3 men (1%) vs. 11 women (3.4%) (p < 0.05).The TnI peak did not reach any significant differences between sexes (men 7.9 +/- 6.0 vs. 8.5 +/- 6.5 microg/L in women. p = not significant). CONCLUSION: No clinically relevant sex-based differences were found in the TnI peaks after cardiac surgery.

Relationships among haemoglobin level, packed red cell transfusion and clinical outcomes in patients after cardiac surgery.

OBJECTIVE: To identify associations among haemoglobin (Hb) concentrations, blood transfusions, and clinical outcomes in patients after cardiac surgery, especially in those who undergo valve replacement or bypass surgery. DESIGN: Prospective observational trial. SETTING: Surgical intensive care unit in a tertiary-level university hospital. PATIENTS: 1216 Consecutive patients. MEASUREMENTS: Haemoglobin at admission and 6, 12, 24, and 48 h later, and then, every 24 h while patients remained in the intensive care unit (ICU); number of transfusions and clinical events. RESULTS: Patients were divided into quartiles according to minimal haemoglobin, the first and second of which (Hb <8.10 and <8.91 g/dL, respectively) differed significantly (P < 0.001) from the other two quartiles in terms of more organ failure, longer ICU stay, and higher mortality. We found associations between being transfused >or=4 packed red cells (PRCs) and a worse clinical outcome and higher mortality. The associated mortality rate was higher for patients who underwent bypass surgery when they had Hb 8.9 g/dL and were transfused >or=4 PRCs. CONCLUSIONS: Low haemoglobin concentrations and transfusions in patients undergoing cardiac surgery are associated with increased morbidity and mortality. Also, anemia and transfusions are associated with poor outcome. Therefore, intra- and postoperative bleeding seem to be a risk factor in patients undergoing cardiac surgery.

Is C-reactive protein a biomarker for immediate clinical outcome after cardiac surgery?

OBJECTIVE: The purpose of this study was to determine the possible correlation between inflammatory activation after cardiac surgery with cardiopulmonary bypass, measured by postoperative C-reactive protein concentrations, and immediate intensive care unit outcome. DESIGN: A prospective, clinical cohort study. SETTING: A 10-bed surgical intensive care unit at a tertiary university hospital. PATIENTS: Two hundred sixteen consecutive patients undergoing nonemergency cardiac surgery with cardiopulmonary bypass. MEASUREMENTS AND MAIN RESULTS: Parsonnet and Acute Physiology and Chronic Health Evaluation scores, characteristics of the surgical intervention, intensive care unit length of stay, and mortality were recorded along with the following variables: cardiac (hours requiring inotropic support and new atrial fibrillation), respiratory (oxygenation index and hours requiring intubation), renal (difference between serum creatinine at admission and maximum creatinine), and analytic (C-reactive protein at admission and 6, 24, and 48 hours later; troponin I; CK-MB; and lactate). RESULTS: Postoperative C-reactive protein concentrations did not correlate with variables such as time requiring inotropic support or intubation, oxygenation index, delta serum creatinine, and intensive care unit length of stay (with the exception of cardiopulmonary bypass time and the more frequent norepinephrine requirement in patients with higher C-reactive protein concentration at 48 hours); nor did C-reactive protein correlate with the analytic variables (with the exception of the lactate peak and C-reactive protein concentrations at 24 and 48 hours). There was no correlation between C-reactive protein and postoperative variables for coronary artery bypass graft surgery and valvular groups analyzed separately. CONCLUSION: Postoperative C-reactive protein does not seem to be a useful marker in predicting outcome after 48 hours in the intensive care unit.