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      Lactate versus non-lactate metabolic acidosis: a retrospective outcome evaluation of critically ill patients

      1 , 2 , 3 , , 4

      Critical Care

      BioMed Central

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          Acid–base abnormalities are common in the intensive care unit (ICU). Differences in outcome exist between respiratory and metabolic acidosis in similar pH ranges. Some forms of metabolic acidosis (for example, lactate) seem to have worse outcomes than others (for example, chloride). The relative incidence of each type of disorder is unknown. We therefore designed this study to determine the nature and clinical significance of metabolic acidosis in critically ill patients.


          An observational, cohort study of critically ill patients was performed in a tertiary care hospital. Critically ill patients were selected on the clinical suspicion of the presence of lactic acidosis. The inpatient mortality of the entire group was 14%, with a length of stay in hospital of 12 days and a length of stay in the ICU of 5.8 days.


          We reviewed records of 9,799 patients admitted to the ICUs at our institution between 1 January 2001 and 30 June 2002. We selected a cohort in which clinicians caring for patients ordered a measurement of arterial lactate level. We excluded patients in which any necessary variable required to characterize an acid–base disorder was absent. A total of 851 patients (9% of ICU admissions) met our criteria. Of these, 548 patients (64%) had a metabolic acidosis (standard base excess < -2 mEq/l) and these patients had a 45% mortality, compared with 25% for those with no metabolic acidosis ( p < 0.001). We then subclassified metabolic acidosis cases on the basis of the predominant anion present (lactate, chloride, or all other anions). The mortality rate was highest for lactic acidosis (56%); for strong ion gap (SIG) acidosis it was 39% and for hyperchloremic acidosis 29% ( p < 0.001). A stepwise logistic regression model identified serum lactate, SIG, phosphate, and age as independent predictors of mortality.


          In critically ill patients in which a measurement of lactate level was ordered, lactate and SIG were strong independent predictors of mortality when they were the major source of metabolic acidosis. Overall, patients with metabolic acidosis were nearly twice as likely to die as patients without metabolic acidosis.

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          Most cited references 28

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          Low mortality rate in adult respiratory distress syndrome using low-volume, pressure-limited ventilation with permissive hypercapnia: a prospective study.

          To evaluate the outcome in patients with severe adult respiratory distress syndrome (ARDS) managed with limitation of peak inspiratory pressure to 30 to 40 cm H2O, low tidal volumes (4 to 7 mL/kg), spontaneous breathing using synchronized intermittent mandatory ventilation from the start of ventilation, and permissive hypercapnia without the use of bicarbonate to buffer acidosis. Also, to compare hospital mortality rate with that predicted by the Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system and the "ventilator score." A ten-bed general intensive care unit in a university hospital. Prospective, descriptive study. Fifty-three patients with severe ARDS having a lung injury score of > or = 2.5. Data recording. The hospital mortality rate was significantly lower than that predicted by the APACHE II scores (26.4% vs. 53.3%, p = .004), even after correcting the latter for the effect of hypercapnic acidosis (26.4% vs. 51.1%, p = .008). The mortality rate increased with increasing number of organ failures, but was only 43% in patients with > or = 4 organ failures, 20.5% with < or = 3 organ failures, and 6.6% with only respiratory failure. The mean maximum PaCO2 was 66.5 torr (range 38 to 158 torr [8.87 kPa, range 5.07 to 21.07]), and the mean arterial pH at the same time was 7.23 (range 6.79 to 7.45). There was no correlation between the maximum PaCO2 or the corresponding pH and the total respiratory rate at the same time. No pneumothoraces developed during mechanical ventilation. These results lend further support to the hypothesis that limitation of peak inspiratory pressure and reduction of regional lung overdistention by the use of low tidal volumes with permissive hypercapnia may reduce ventilator-induced lung injury and improve outcome in severe ARDS. This hypothesis is supported by a large body of experimental evidence, which also suggests that ventilator-induced lung injury may result in the release of inflammatory mediators, and thus may have the potential to augment the development of multiple organ dysfunction. However, the hypothesis requires testing in a randomized trial as acute hypercapnia could potentially have some adverse as well as beneficial effects.
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            Admission base deficit predicts transfusion requirements and risk of complications.

             K Kaups,  J. Davis,  S Nicol (1996)
            Trauma center resource management could be facilitated by a readily available indicator of resource consumption. This marker should identify patients more likely to require transfusion and intensive care services and to develop complications. Base deficit (BD) has been shown to be a valuable indicator of shock, abdominal injury, fluid requirements, efficacy of resuscitation, and to be predictive of mortality after trauma. This study was performed to determine whether BD could be used to identify which patients were likely to require blood transfusion in the first 24 hours of hospitalization, and to develop shock-related complications and increased intensive care unit (ICU) and hospital stays. A retrospective review of 2,954 patients admitted to the Valley Medical Center Level I trauma service from July 1990 through August 1995 was done using the trauma registry and blood bank data bases. Medical record review was done to supplement missing data. Transfusion requirements increased as the BD category became more severe (p -6 (p < 0.001, chi 2). Both ICU and hospital length of stay increased with worsening BD (p < 0.015 and p < 0.05, respectively). The frequency of adult respiratory distress syndrome (ARDS) (p < 0.01), renal failure (p = 0.015), coagulopathy (p < 0.001), and multiorgan system failure (MOF) (p = 0.002) all increased with increasingly severe BD. Discriminate analysis using Injury Severity Score (ISS) and BD category demonstrated predictive accuracy of 81%, 77%, and 77% for coagulopathy, ARDS, and MOF, respectively. Mortality also increased with worsening BD. When stratified by BD category, there was no difference between observed and predicted survival. Admission BD identifies patients likely to require early transfusion and increased ICU and hospital stays, and be at increased risk for shock-related complications. Patients with BD < or = -6 should undergo type and cross-match rather than type and screen. The use of ISS and BD category probability curves may identify candidates for early invasive monitoring.
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              Determinants of blood pH in health and disease

              An advanced understanding of acid–base physiology is as central to the practice of critical care medicine, as are an understanding of cardiac and pulmonary physiology. Intensivists spend much of their time managing problems related to fluids, electrolytes, and blood pH. Recent advances in the understanding of acid–base physiology have occurred as the result of the application of basic physical-chemical principles of aqueous solutions to blood plasma. This analysis has revealed three independent variables that regulate pH in blood plasma. These variables are carbon dioxide, relative electrolyte concentrations, and total weak acid concentrations. All changes in blood pH, in health and in disease, occur through changes in these three variables. Clinical implications for these findings are also discussed.

                Author and article information

                Crit Care
                Critical Care
                BioMed Central (London )
                10 February 2006
                : 10
                : 1
                : R22
                [1 ]Assistant Professor, VCURES (Virginia Commonwealth University Reanimation Engineering Shock Center) Laboratory, Departments of Anesthesiology/Critical Care and Emergency Medicine, Medical College of Virginia/Virginia Commonwealth University, 1200 East Broad Street, Richmond, VA, 23298, USA
                [2 ]Director, Clinical Research Informatics Service, University of Pittsburgh, 450 Scaife Hall, 200 Lothrop St. Pittsburgh, PA, 15213, USA
                [3 ]Research Assistant, Department of Biostatistics, University of Pittsburgh, Graduate School of Public Health, Crabtree Hall, Pittsburgh, PA, 15213, USA
                [4 ]Professor, CRISMA (Clinical Research, Investigation, and Systems Modeling of Acute illness) Laboratory, Department of Critical Care Medicine, University of Pittsburgh, 608, Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA
                Copyright © 2006 Gunnerson et al.; licensee BioMed Central Ltd.

                This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


                Emergency medicine & Trauma


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