282 Short report
Lactate is associated with increased 10-day mortality in acute medical patients: a hospital-based cohort study Felix Haidla, Mikkel Brabrandc, Daniel P. Henriksenb and Annmarie T. Lassenb An increased lactate level is related to increased mortality in subpopulations of critically ill patients. The aim of this study was to investigate whether lactate was related to mortality in an emergency department (ED) setting of undifferentiated medical patients. All adult patients admitted from March 2009 to August 2011 to a medical ED with lactate measured within 6 h after arrival were studied. Lactate was stratified into 1-mmol/l intervals and analysed in a multivariate logistic regression analysis. A total of 5317 patients were included, 46.9% men, median age 71 years (5–95% percentiles 25–90 years). The median lactate level was 1.2 mmol/l (5–95% percentiles 0.6–3.8 mmol/l, range 0.2–22 mmol/l). Lactate was associated with 10-day mortality independent of age, comorbidity and presence of hypotension, with an odds ratio of 1.54 (95% confidence interval 1.44–1.63) per 1 mmol/l increase. Lactate is
Introduction Shock is defined as inadequate tissue oxygenation and/or perfusion and is caused by different pathophysiological mechanisms such as hypovolaemia, cardiac failure or severe infection [1]. This results in a shift to an anaerobic cell metabolism and an increased production of lactate. The condition is associated with high mortality, and randomized clinical trials have shown that rapid, focused interventions decrease mortality. There is growing awareness of a condition of occult or cryptic shock, which is as severe as shock identified by hypotension (i.e. ‘overt shock’) [2,3]. It is defined as signs of hypoperfusion (i.e. high blood lactate levels) without the presence of hypotension. In 2011, Puskarich et al. [2] found that the cryptic shock condition is associated with a mortality level equal to that of patients with overt shock. Several studies have found that increasing lactate is associated with increased mortality in the emergency department (ED) as well as in the ICU [3–6]. However, these studies are either based on a small number of patients or selected patient populations (i.e. trauma patients, patients with suspected infection or sepsis, etc.). The aim of this study was to investigate lactate as a marker of mortality among acutely admitted medical patients in the ED setting.
an independent predictor of 10-day mortality among patients admitted to a medical ED. European Journal of Emergency Medicine 22:282–284 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. European Journal of Emergency Medicine 2015, 22:282–284 Keywords: 10-day mortality, hypotension, lactate, medical patients, occult shock a Department of Anesthesia, Lillebaelt Hospital, Kolding, bDepartment of Emergency Medicine, Odense University Hospital, Odense and cDepartment of Emergency Medicine, Hospital of South West Jutland, Esbjerg, Denmark
Correspondence to Felix Haidl, MD, Department of Anesthesia, Lillebaelt Hospital, Skovvangen 2, DK-6000 Kolding, Denmark Tel: + 47 46 65 67 07; fax: + 47 67 96 88 61; e-mail: [email protected] Received 23 March 2014 Accepted 21 August 2014
at Odense University Hospital, Denmark, during the period from March 2009 to August 2011. The hospital serves as a primary hospital for a population of 288 000 individuals. The medical ED serves as an acute medical unit and receives patients from a wide variety of internal medicine subspecialities, although neurology and cardiology patients are generally admitted elsewhere. The patients are admitted either directly from primary care by ambulance services (∼60%) or from the open general ED (∼40%), and are generally admitted for short periods, or until they are transferred to a more disease-specific ward. The open general ED serves as a level-1 trauma centre with mixed medical–surgical patients. Initial stabilizing treatment and diagnostic investigation is performed in the general ED for patients in shock or otherwise severely ill patients, but most treatment is performed at the medical ED after transfer. Patients admitted to the department, who had an arterial blood gas sample taken within 6 h of arrival, were included in the study. Patients were included at their first registration during the study period. Patients were excluded if they had a venous blood gas sample drawn (defined as PO2 < 5.0 kPa and peripheral oxygen saturation > 90%); patients not registered by the Danish civil registration system were also excluded [7].
Data collection
Patients and methods Study population
The study was a single-centre cohort study including all adult (≥15 years) patients admitted to the medical ED 0969-9546 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Systolic blood pressure at arrival to the department was registered from the individual patient medical records. Information on length of hospitalization and ICD-10 discharge diagnoses was obtained from the Danish DOI: 10.1097/MEJ.0000000000000210
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Lactate is associated with increased mortality Haidl et al. 283
national patient register [8]. A Charlson comorbidity index was calculated on the basis of discharge diagnoses of the last 10 years [9]. Demographic data including mortality were obtained from the Danish civil registration system [7]. Because of the unique identification number assigned to every Danish citizen, we could link information from the different data sources to the individual patients.
Analysis
Lactate levels were reported in predefined 1-mmol/l intervals until 8 mmol/l or more. Ten-day mortality was reported for each of the 1-mmol/l intervals. Univariate analyses of risk of 10-day mortality were carried out for predefined prognostic factors possibly related to 10-day mortality. Prognostic factors with a P-value less than 0.1 were included in a multivariable logistic regression analysis for the evaluation of lactate levels as an independent risk factor for 10-day mortality. Missing values were treated as if they were within the normal range. Data were assumed to be non-normally distributed, and the χ2-test, and the Mann–Whitney U-test were used where appropriate. P-values less than 0.05 were considered significant, and 95% confidence intervals (CIs) for proportions were calculated under the assumption of a binomial distribution. Statistical analyses were carried out using Stata/MP version 11.2 (StataCorp, College Station, Texas, USA).
Ethics
The study was approved by the Danish Data Protection Agency (No. 2008-58-0035) and the Danish national board of health (No. 3-3013-35). Fig. 1
Absolute 10-day mortality (%)
Overall mortality 70 60 50 40
Results A total of 5317 patients were included. Samples were drawn within a median of 1 h (5–95% percentiles 0–4 h) after arrival to the medical ED. In seven patients (0.13%), the lactate value was missing, but in accordance with predefined management of missing values included as normal with lactate of less than 1 mmol/l. In all, 46.9% of the patients were men; the median age was 71 years (5–95% percentiles 25–90 years) and the median lactate value was 1.2 mmol/l (5–95% percentiles 0.6–3.8 mmol/l, range 0.2–22 mmol/l). The median length of stay was 5 days (5–95% percentiles 1–22 days); 34.8% were discharged from the hospital with a diagnosis of infection and 13.8% with respiratory failure. Overall 10-day mortality was 7.2%. Lactate was stratified into intervals of 1 mmol/l (0–0.99, 1–1.99, etc.) and correlated to absolute 10-day mortality with 4.3% (95% CI 3.4–5.3%) 10-day mortality for lactate less than 1.0 mmol/l and 45.5% (95% CI 32.0–59.4%) for lactate of 8 mmol/l or more (Fig. 1). We found a significant trend (P < 0.001) towards higher mortality associated with higher lactate levels. Univariate analysis showed that mortality increased with increasing lactate, increasing age, increasing comorbidity as well as the presence of hypotension at arrival (Table 1). The multivariable analysis (Table 1) showed that lactate was associated with 10-day mortality independent of age, comorbidity (Charlson comorbidity index) and the presence of hypotension. Ten-day mortality was 18.4% (95% CI 12.8–25.2%) among all the patients included with hypotension at arrival to the ED compared with 6.1% (95% CI 5.4–6.9%) among patients arriving with normotension (P < 0.001).
Discussion In this large cohort of acutely hospitalized medical patients, we found that a high level of lactate was an independent prognostic factor of short-term mortality. We found a significant trend towards increased mortality for every mmol/l increase of lactate and this trend was independent of the presence of hypotension. These findings confirm results from previous studies by Puskarich et al. [2], Howell et al. [3] and Shapiro et al. [4], who showed that lactate is associated with an increased short-term mortality among patients admitted with suspected infection.
P < 0.001
30 20 10 0 0–0.99 1–1.99 2–2.99 3–3.99 4–4.99 5–5.99 6–6.99 7–7.99 8+ (n=1857)(n=2313)(n=685) (n=203) (n=110) (n=48) (n=28) (n=18) (n=48) Lactate (mmol/l)
Absolute 10-day mortality (%) according to lactate (mmol/l). Data are presented as measured mortality (dot) 95% confidence interval (whisker). P-value for trend < 0.001.
Our results also confirm those of Puskarich et al. [6] evaluating the association between lactate as a continuous measure (rather than a dichotomous) and in-hospital mortality. Puskarich and colleagues found that, in a population of patients with suspected infection presenting to the ED, lactate was correlated with in-hospital
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
284 European Journal of Emergency Medicine 2015, Vol 22 No 4
Table 1
Univariate and multivariate analyses of selected variables according to 10-day mortality
Age (years) Male Female Charlson comorbidity index 0 score 1 score ≥ 2 score Systolic BP ≥ 90 mmHg Systolic BP < 90 mmHg Lactate (mmol/l)
Overall population (N = 5317)
Nonsurvivors (10 days) (N = 382)
71 (25–91) 2493 (47) 2824 (53)
81 (57–95) 178 (47) 204 (53)
1836 1315 2166 3959 163 1.2
75 75 232 242 30 1.8
(34) (25) (41) (96) (4) (0.6–3.8)
(20) (20) (60) (89) (11) (0.6–8.8)
P-value univariate
Multivariable logistic regressiona
< 0.001
1.05 (1.05–1.06)
0.91
< 0.001 < 0.001 < 0.001
1 1.14 (0.8–1.61) 1.81 (1.36–2.41) 1 1.71 (1.08–2.72) 1.53 (1.44–1.62)
Data are presented as median (5–95% percentiles) or N (%) or odds ratio (95% confidence interval). P-values were calculated using the χ2-test or the Mann–Whitney U-test. BP, blood pressure. a Multivariable (logistic regression) model of 10-day mortality including age (1-year intervals), comorbidity (Charlson comorbidity index), presence of hypotension (systolic blood pressure < 90 mmHg) and lactate in 1-mmol/l intervals up to 8 mmol/l.
mortality. However, in contrast to the present study, Puskarich and colleagues study was carried out on a smaller and narrower population. Our results lend further weight to the concept of occult shock [2,3] as normotensive patients had increasing mortality with increasing lactate, although we found that patients with hypotension and high lactate had higher mortality. The strength of this study is its sample size, which enables a multivariable analysis and a fair chance for control of confounding factors. Second, the cohort included a mixed population of acutely hospitalized medical patients, and it was confirmed that the relation between increasing lactate and mortality is not restricted to selected populations. The results pinpoint the prognostic potential of lactate to be a part of a rapid, objective identification of patients who require a quick and focused intervention. We used 10-day mortality as the outcome as we aimed to evaluate whether lactate is a marker of acute illness and not long-term mortality. A limitation of the study is the retrospective design, which increases the possibility of selection bias, as not all admitted patients have an arterial blood gas drawn. Blood gases were drawn on the basis of the clinician’s decision, and we have probably included a patient population with more severely ill patients than among acute medical patients who have no arterial blood samples taken. Not all patients had a complete set of vital signs recorded at arrival. As 22.5% of the systolic blood pressure recordings were missing, this could lead to misclassification of the hypotensive patients. Because of the retrospective design of the study, we could not retrieve information on the stage of treatment that the patient was in at the time of blood gas sampling. Although we have included a less selected study population than previous studies [3–6], we did not include all patients admitted to the hospital; thus, our results cannot be generalized to surgical patients or patients admitted with suspected myocardial infarction or stroke. These
patients might differ from the patient population in the present study. Both in patients with myocardial infarction and in those with stroke, increased lactate levels have been associated previously with a worsened prognosis [10]. Furthermore, we could not estimate to which degree a possible delay in treatment influenced the prognosis. Conclusion
Lactate levels within 6 h of admission from patients admitted to a medical ED provides prognostic information on 10-day mortality in a continuous manner.
Acknowledgements Conflicts of interest
There are no conflicts of interest.
References 1
Vincent JL, de Backer D. Circulatory shock. N Engl J Med 2013; 369:1726–1734. 2 Puskarich MA, Trzeciak S, Shapiro NI, Heffner AC, Kline JA, Jones AE. Emergency Medicine Shock Research Network (EMSHOCKNET). Outcomes of patients undergoing early sepsis resuscitation for cryptic shock compared with overt shock. Resuscitation 2011; 82:1289–1293. 3 Howell MD, Donnino M, Clardy P, Talmor D, Shapiro NI. Occult hypoperfusion and mortality in patients with suspected infection. Intensive Care Med 2007; 33:1892–1899. 4 Shapiro NI, Howell MD, Talmor D, Nathanson LA, Lisbon A, Wolfe RE, Weiss JW. Serum lactate as a predictor of mortality in emergency department patients with infection. Ann Emerg Med 2005; 45:524–528. 5 Mikkelsen ME, Miltiades AN, Gaieski DF, Goyal M, Fuchs BD, Shah CV, et al. Serum lactate is associated with mortality in severe sepsis independent of organ failure and shock. Crit Care Med 2009; 37:1670–1677. 6 Puskarich MA, Kline JA, Summers RL, Jones AE. Prognostic value of incremental lactate elevations in emergency department patients with suspected infection. Acad Emerg Med 2012; 19:983–985. 7 Petersen CB. The Danish Civil Registration System. Scand J Public Health 2011; 39 (Suppl):22–25. 8 Lynge E, Sandegaard JL, Rebolj M. The Danish National Patient Register. Scand J Public Health 2011; 39 (Suppl):30–33. 9 Olsson T, Terent A, Lind L. Charlson comorbidity index can add prognostic information to rapid emergency medicine score as a predictor of long-term mortality. Eur J Emerg Med 2005; 12:220–224. 10 Matsushita K, Williams EK, Mongraw-Chaffin ML, Coresh J, Schmidt MI, Brancati FL, et al. The association of plasma lactate with incident cardiovascular outcomes: the ARIC study. Am J Epidemiol 2013; 178:401–409.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Lactate is associated with increased 10-day mortality in acute medical patients: a hospital-based cohort study Felix Haidla, Mikkel Brabrandc, Daniel P. Henriksenb and Annmarie T. Lassenb An increased lactate level is related to increased mortality in subpopulations of critically ill patients. The aim of this study was to investigate whether lactate was related to mortality in an emergency department (ED) setting of undifferentiated medical patients. All adult patients admitted from March 2009 to August 2011 to a medical ED with lactate measured within 6 h after arrival were studied. Lactate was stratified into 1-mmol/l intervals and analysed in a multivariate logistic regression analysis. A total of 5317 patients were included, 46.9% men, median age 71 years (5–95% percentiles 25–90 years). The median lactate level was 1.2 mmol/l (5–95% percentiles 0.6–3.8 mmol/l, range 0.2–22 mmol/l). Lactate was associated with 10-day mortality independent of age, comorbidity and presence of hypotension, with an odds ratio of 1.54 (95% confidence interval 1.44–1.63) per 1 mmol/l increase. Lactate is
Introduction Shock is defined as inadequate tissue oxygenation and/or perfusion and is caused by different pathophysiological mechanisms such as hypovolaemia, cardiac failure or severe infection [1]. This results in a shift to an anaerobic cell metabolism and an increased production of lactate. The condition is associated with high mortality, and randomized clinical trials have shown that rapid, focused interventions decrease mortality. There is growing awareness of a condition of occult or cryptic shock, which is as severe as shock identified by hypotension (i.e. ‘overt shock’) [2,3]. It is defined as signs of hypoperfusion (i.e. high blood lactate levels) without the presence of hypotension. In 2011, Puskarich et al. [2] found that the cryptic shock condition is associated with a mortality level equal to that of patients with overt shock. Several studies have found that increasing lactate is associated with increased mortality in the emergency department (ED) as well as in the ICU [3–6]. However, these studies are either based on a small number of patients or selected patient populations (i.e. trauma patients, patients with suspected infection or sepsis, etc.). The aim of this study was to investigate lactate as a marker of mortality among acutely admitted medical patients in the ED setting.
an independent predictor of 10-day mortality among patients admitted to a medical ED. European Journal of Emergency Medicine 22:282–284 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. European Journal of Emergency Medicine 2015, 22:282–284 Keywords: 10-day mortality, hypotension, lactate, medical patients, occult shock a Department of Anesthesia, Lillebaelt Hospital, Kolding, bDepartment of Emergency Medicine, Odense University Hospital, Odense and cDepartment of Emergency Medicine, Hospital of South West Jutland, Esbjerg, Denmark
Correspondence to Felix Haidl, MD, Department of Anesthesia, Lillebaelt Hospital, Skovvangen 2, DK-6000 Kolding, Denmark Tel: + 47 46 65 67 07; fax: + 47 67 96 88 61; e-mail: [email protected] Received 23 March 2014 Accepted 21 August 2014
at Odense University Hospital, Denmark, during the period from March 2009 to August 2011. The hospital serves as a primary hospital for a population of 288 000 individuals. The medical ED serves as an acute medical unit and receives patients from a wide variety of internal medicine subspecialities, although neurology and cardiology patients are generally admitted elsewhere. The patients are admitted either directly from primary care by ambulance services (∼60%) or from the open general ED (∼40%), and are generally admitted for short periods, or until they are transferred to a more disease-specific ward. The open general ED serves as a level-1 trauma centre with mixed medical–surgical patients. Initial stabilizing treatment and diagnostic investigation is performed in the general ED for patients in shock or otherwise severely ill patients, but most treatment is performed at the medical ED after transfer. Patients admitted to the department, who had an arterial blood gas sample taken within 6 h of arrival, were included in the study. Patients were included at their first registration during the study period. Patients were excluded if they had a venous blood gas sample drawn (defined as PO2 < 5.0 kPa and peripheral oxygen saturation > 90%); patients not registered by the Danish civil registration system were also excluded [7].
Data collection
Patients and methods Study population
The study was a single-centre cohort study including all adult (≥15 years) patients admitted to the medical ED 0969-9546 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Systolic blood pressure at arrival to the department was registered from the individual patient medical records. Information on length of hospitalization and ICD-10 discharge diagnoses was obtained from the Danish DOI: 10.1097/MEJ.0000000000000210
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
Lactate is associated with increased mortality Haidl et al. 283
national patient register [8]. A Charlson comorbidity index was calculated on the basis of discharge diagnoses of the last 10 years [9]. Demographic data including mortality were obtained from the Danish civil registration system [7]. Because of the unique identification number assigned to every Danish citizen, we could link information from the different data sources to the individual patients.
Analysis
Lactate levels were reported in predefined 1-mmol/l intervals until 8 mmol/l or more. Ten-day mortality was reported for each of the 1-mmol/l intervals. Univariate analyses of risk of 10-day mortality were carried out for predefined prognostic factors possibly related to 10-day mortality. Prognostic factors with a P-value less than 0.1 were included in a multivariable logistic regression analysis for the evaluation of lactate levels as an independent risk factor for 10-day mortality. Missing values were treated as if they were within the normal range. Data were assumed to be non-normally distributed, and the χ2-test, and the Mann–Whitney U-test were used where appropriate. P-values less than 0.05 were considered significant, and 95% confidence intervals (CIs) for proportions were calculated under the assumption of a binomial distribution. Statistical analyses were carried out using Stata/MP version 11.2 (StataCorp, College Station, Texas, USA).
Ethics
The study was approved by the Danish Data Protection Agency (No. 2008-58-0035) and the Danish national board of health (No. 3-3013-35). Fig. 1
Absolute 10-day mortality (%)
Overall mortality 70 60 50 40
Results A total of 5317 patients were included. Samples were drawn within a median of 1 h (5–95% percentiles 0–4 h) after arrival to the medical ED. In seven patients (0.13%), the lactate value was missing, but in accordance with predefined management of missing values included as normal with lactate of less than 1 mmol/l. In all, 46.9% of the patients were men; the median age was 71 years (5–95% percentiles 25–90 years) and the median lactate value was 1.2 mmol/l (5–95% percentiles 0.6–3.8 mmol/l, range 0.2–22 mmol/l). The median length of stay was 5 days (5–95% percentiles 1–22 days); 34.8% were discharged from the hospital with a diagnosis of infection and 13.8% with respiratory failure. Overall 10-day mortality was 7.2%. Lactate was stratified into intervals of 1 mmol/l (0–0.99, 1–1.99, etc.) and correlated to absolute 10-day mortality with 4.3% (95% CI 3.4–5.3%) 10-day mortality for lactate less than 1.0 mmol/l and 45.5% (95% CI 32.0–59.4%) for lactate of 8 mmol/l or more (Fig. 1). We found a significant trend (P < 0.001) towards higher mortality associated with higher lactate levels. Univariate analysis showed that mortality increased with increasing lactate, increasing age, increasing comorbidity as well as the presence of hypotension at arrival (Table 1). The multivariable analysis (Table 1) showed that lactate was associated with 10-day mortality independent of age, comorbidity (Charlson comorbidity index) and the presence of hypotension. Ten-day mortality was 18.4% (95% CI 12.8–25.2%) among all the patients included with hypotension at arrival to the ED compared with 6.1% (95% CI 5.4–6.9%) among patients arriving with normotension (P < 0.001).
Discussion In this large cohort of acutely hospitalized medical patients, we found that a high level of lactate was an independent prognostic factor of short-term mortality. We found a significant trend towards increased mortality for every mmol/l increase of lactate and this trend was independent of the presence of hypotension. These findings confirm results from previous studies by Puskarich et al. [2], Howell et al. [3] and Shapiro et al. [4], who showed that lactate is associated with an increased short-term mortality among patients admitted with suspected infection.
P < 0.001
30 20 10 0 0–0.99 1–1.99 2–2.99 3–3.99 4–4.99 5–5.99 6–6.99 7–7.99 8+ (n=1857)(n=2313)(n=685) (n=203) (n=110) (n=48) (n=28) (n=18) (n=48) Lactate (mmol/l)
Absolute 10-day mortality (%) according to lactate (mmol/l). Data are presented as measured mortality (dot) 95% confidence interval (whisker). P-value for trend < 0.001.
Our results also confirm those of Puskarich et al. [6] evaluating the association between lactate as a continuous measure (rather than a dichotomous) and in-hospital mortality. Puskarich and colleagues found that, in a population of patients with suspected infection presenting to the ED, lactate was correlated with in-hospital
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
284 European Journal of Emergency Medicine 2015, Vol 22 No 4
Table 1
Univariate and multivariate analyses of selected variables according to 10-day mortality
Age (years) Male Female Charlson comorbidity index 0 score 1 score ≥ 2 score Systolic BP ≥ 90 mmHg Systolic BP < 90 mmHg Lactate (mmol/l)
Overall population (N = 5317)
Nonsurvivors (10 days) (N = 382)
71 (25–91) 2493 (47) 2824 (53)
81 (57–95) 178 (47) 204 (53)
1836 1315 2166 3959 163 1.2
75 75 232 242 30 1.8
(34) (25) (41) (96) (4) (0.6–3.8)
(20) (20) (60) (89) (11) (0.6–8.8)
P-value univariate
Multivariable logistic regressiona
< 0.001
1.05 (1.05–1.06)
0.91
< 0.001 < 0.001 < 0.001
1 1.14 (0.8–1.61) 1.81 (1.36–2.41) 1 1.71 (1.08–2.72) 1.53 (1.44–1.62)
Data are presented as median (5–95% percentiles) or N (%) or odds ratio (95% confidence interval). P-values were calculated using the χ2-test or the Mann–Whitney U-test. BP, blood pressure. a Multivariable (logistic regression) model of 10-day mortality including age (1-year intervals), comorbidity (Charlson comorbidity index), presence of hypotension (systolic blood pressure < 90 mmHg) and lactate in 1-mmol/l intervals up to 8 mmol/l.
mortality. However, in contrast to the present study, Puskarich and colleagues study was carried out on a smaller and narrower population. Our results lend further weight to the concept of occult shock [2,3] as normotensive patients had increasing mortality with increasing lactate, although we found that patients with hypotension and high lactate had higher mortality. The strength of this study is its sample size, which enables a multivariable analysis and a fair chance for control of confounding factors. Second, the cohort included a mixed population of acutely hospitalized medical patients, and it was confirmed that the relation between increasing lactate and mortality is not restricted to selected populations. The results pinpoint the prognostic potential of lactate to be a part of a rapid, objective identification of patients who require a quick and focused intervention. We used 10-day mortality as the outcome as we aimed to evaluate whether lactate is a marker of acute illness and not long-term mortality. A limitation of the study is the retrospective design, which increases the possibility of selection bias, as not all admitted patients have an arterial blood gas drawn. Blood gases were drawn on the basis of the clinician’s decision, and we have probably included a patient population with more severely ill patients than among acute medical patients who have no arterial blood samples taken. Not all patients had a complete set of vital signs recorded at arrival. As 22.5% of the systolic blood pressure recordings were missing, this could lead to misclassification of the hypotensive patients. Because of the retrospective design of the study, we could not retrieve information on the stage of treatment that the patient was in at the time of blood gas sampling. Although we have included a less selected study population than previous studies [3–6], we did not include all patients admitted to the hospital; thus, our results cannot be generalized to surgical patients or patients admitted with suspected myocardial infarction or stroke. These
patients might differ from the patient population in the present study. Both in patients with myocardial infarction and in those with stroke, increased lactate levels have been associated previously with a worsened prognosis [10]. Furthermore, we could not estimate to which degree a possible delay in treatment influenced the prognosis. Conclusion
Lactate levels within 6 h of admission from patients admitted to a medical ED provides prognostic information on 10-day mortality in a continuous manner.
Acknowledgements Conflicts of interest
There are no conflicts of interest.
References 1
Vincent JL, de Backer D. Circulatory shock. N Engl J Med 2013; 369:1726–1734. 2 Puskarich MA, Trzeciak S, Shapiro NI, Heffner AC, Kline JA, Jones AE. Emergency Medicine Shock Research Network (EMSHOCKNET). Outcomes of patients undergoing early sepsis resuscitation for cryptic shock compared with overt shock. Resuscitation 2011; 82:1289–1293. 3 Howell MD, Donnino M, Clardy P, Talmor D, Shapiro NI. Occult hypoperfusion and mortality in patients with suspected infection. Intensive Care Med 2007; 33:1892–1899. 4 Shapiro NI, Howell MD, Talmor D, Nathanson LA, Lisbon A, Wolfe RE, Weiss JW. Serum lactate as a predictor of mortality in emergency department patients with infection. Ann Emerg Med 2005; 45:524–528. 5 Mikkelsen ME, Miltiades AN, Gaieski DF, Goyal M, Fuchs BD, Shah CV, et al. Serum lactate is associated with mortality in severe sepsis independent of organ failure and shock. Crit Care Med 2009; 37:1670–1677. 6 Puskarich MA, Kline JA, Summers RL, Jones AE. Prognostic value of incremental lactate elevations in emergency department patients with suspected infection. Acad Emerg Med 2012; 19:983–985. 7 Petersen CB. The Danish Civil Registration System. Scand J Public Health 2011; 39 (Suppl):22–25. 8 Lynge E, Sandegaard JL, Rebolj M. The Danish National Patient Register. Scand J Public Health 2011; 39 (Suppl):30–33. 9 Olsson T, Terent A, Lind L. Charlson comorbidity index can add prognostic information to rapid emergency medicine score as a predictor of long-term mortality. Eur J Emerg Med 2005; 12:220–224. 10 Matsushita K, Williams EK, Mongraw-Chaffin ML, Coresh J, Schmidt MI, Brancati FL, et al. The association of plasma lactate with incident cardiovascular outcomes: the ARIC study. Am J Epidemiol 2013; 178:401–409.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
