Relationship between arterial and peripheral venous lactate levels

The Relationship Between Lactate and Lactate Clearance with In-Hospital Mortality in Unselected Emergency Department Patients

INTRODUCTION

Lactate is a frequently used biomarker in emergency departments (EDs), especially in critically ill patients. The aim of this study is to investigate the relationship between lactate and lactate clearance with in-hospital mortality in unselected ED patients.

METHODS

This study was carried out retrospectively in the ED of a tertiary hospital. Patients aged 18 years and older whose blood lactate level was obtained in the ED were included in the study. Patients whose lactate value did not have sufficient analytical accuracy, whose lactate value was recorded in the system 180 minutes after admission, who were admitted to the ED as cardiac arrest, and whose ED or hospital outcome was unknown were excluded from the study. According to the first measured lactate value, the patients were divided into three groups: < 2.0mmol/L, 2.0-3.9mmol/L, and ≥ 4.0mmol/L. Lactate clearance was calculated and recorded in patients with one-to-four hours between two lactate values.

RESULTS

During the five-year study period, a total of 1,070,406 patients were admitted to the ED, of which 114,438 (10.7%) received blood gas analysis. The median age of 81,449 patients included in the study was 58 years (IQR: 30, min: 18-max: 117) and 54.4% were female. The study found that non-trauma patients with a lactate level between 2.0-3.9mmol/L had a 2.5-times higher mortality risk, while those with a lactate level of ≥ 4.0mmol/L had a 20.8-times higher risk, compared to those with a lactate level < 2.0mmol/L. For trauma patients, the mortality risk was three-times higher for those with lactate levels between 2.0-3.9mmol/L and nine-times higher for those with a lactate level of ≥ 4.0mmol/L, compared to those with a lactate level < 2.0mmol/L. Among patients with a first measured lactate value ≥ 4.0mmol/L and a two-hour lactate clearance < 20%, the mortality rate was 19.7%. In addition, lactate, lactate clearance, and age were independent variables for mortality in this patient group.

CONCLUSION

The lactate value in unselected patients in the ED is a biomarker that can be used to predict the prognosis of the patients. In addition, lactate, lactate clearance, and age are independent predictors of mortality.

Serum Lactate Level as a Predictor for Blood Transfusion in Postpartum Hemorrhage

OBJECTIVE

Postpartum hemorrhage (PPH) is the leading cause of maternal morbidity and mortality. At present, there are no reliable clinical or laboratory indicators to identify which patients might require blood transfusions during a PPH. Serum lactate has long been used as an early biomarker of tissue hypoperfusion in trauma settings. The aim of this study is to understand serum lactate's role in the management of obstetric hemorrhage.

STUDY DESIGN

A retrospective chart review was performed of women who delivered between 2016 and 2019 at our institution and experienced a PPH. The patients were divided into two groups: those with a normal serum lactate level, defined as ≤2 mmol/L, and those with an abnormal serum lactate level, defined as >2 mmol/L. Need for packed red blood cell transfusion, as part of the resuscitation, was assessed for both groups.

RESULTS

During the study period, 938 women experienced PPH. Of these, 108 (11.5%) had a normal serum lactate, ≤2 mmol/L, and 830 (88.5%) had an abnormal lactate, >2 mmol/L. Women with elevated lactate levels were more likely to receive a blood transfusion versus those with a normal lactate level (57.0 vs. 46.3%, p = 0.035, respectively). Additionally, the average number of blood transfusions administered was significantly higher in the abnormal lactate group versus in the normal lactate group (1.34 vs. 0.97, respectively, p = 0.004). In a multivariable linear regression model, increasing serum lactate levels were found to be predictive of requiring more than 1 unit of blood (p < 0.001).

CONCLUSION

Women with elevated serum lactate levels were more likely to require blood transfusions during a PPH versus those with a normal serum lactate level. Thus, serum lactate levels are useful as an early indicator of requirement for blood transfusion in the management of obstetric hemorrhage.

KEY POINTS

· Lactate is a biomarker for blood transfusion in trauma.. · Lactate's role in PPH is unknown.. · Elevated lactate predicts receiving more blood transfusions..

Elevated blood lactate in COPD exacerbations associates with adverse clinical outcomes and signals excessive treatment with β2 -agonists

BACKGROUND AND OBJECTIVE

Raised blood lactate secondary to high dose β2 -agonist treatment has been reported in asthma exacerbations but has not been investigated during acute exacerbations of COPD (AECOPD). We explored associations of blood lactate measurements with disease outcomes and β2 -agonist treatments during AECOPD.

METHODS

Retrospective (n = 199) and prospective studies (n = 142) of patients hospitalized with AECOPD were conducted. The retrospective cohort was identified via medical records and the prospective cohort was recruited during hospitalization for AECOPD. Baseline demographics, comorbidities, β2 -agonist treatment, biochemical measurements and clinical outcomes were compared between patients with normal (≤2.0 mmol/L) versus elevated lactate (>2.0 mmol/L). Regression analyses examined associations of lactate measurements with β2 -agonist dosages.

RESULTS

Demographic data and comorbidities were similar between high versus normal lactate groups in both cohorts. The populations were elderly (mean >70 years), predominantly male (>60%) with reduced FEV1 (%) 48.2 ± 19 (prospective cohort). Lactate was elevated in approximately 50% of patients during AECOPD and not related to evidence of sepsis. In the prospective cohort, patients with high lactate had more tachypnoea, tachycardia, acidosis and hyperglycaemia (p < 0.05) and received more non-invasive ventilation (37% vs. 9.7%, p < 0.001, prospective cohort). There was a trend to longer hospitalization (6 vs. 5 days, p = 0.06, prospective cohort). Higher cumulative β2 -agonist dosages were linked to elevated lactate levels (OR 1.04, p = 0.01).

CONCLUSION

Elevated lactate during AECOPD was common, unrelated to sepsis and correlated with high cumulative doses of β2 -agonists. Raised lactate may indicate excessive β2 -agonist treatment and should now be investigated as a possible biomarker.

Early clinical outcome prediction based on the initial National Early Warning Score + Lactate (News+L) Score among adult emergency department patients

BACKGROUND

The National Early Warning Score + Lactate (NEWS+L) Score has been previously shown to outperform NEWS alone in prediction of mortality and need for critical care in a small adult ED study. We validated the score in a large patient data set and constructed a model that allows early prediction of the probability of clinical outcomes based on the individual's NEWS+L Score.

METHODS

In this retrospective study, we included all adult patients who visited the ED of a single urban academic tertiary-care university hospital in South Korea for five consecutive years (1 January 2015 to 31 December 2019). The initial (<1 hour) NEWS+L Score is routinely recorded electronically at our ED and was abstracted for each visit. The outcomes were hospital death or a composite of hospital death and intensive care unit admission at 24 hours, 48 hours and 72 hours. The data set was randomly split into train and test sets (1:1) for internal validation. The area under the receiver operating characteristic curve (AUROC) value and area under the precision and recall curve (AUPRC) value were evaluated and logistic regression models were used to develop an equation to calculate the predicted probabilities for each of these outcomes according to the NEWS+L Score.

RESULTS

After excluding 808 patients (0.5%) from 149 007 patients in total, the study cohort consisted of 148 199 patients. The mean NEWS+L Score was 3.3±3.8. The AUROC value was 0.789~0.813 for the NEWS+L Score with good calibration (calibration-in-the-large=-0.082~0.001, slope=0.964~0.987, Brier Score=0.011~0.065). The AUPRC values of the NEWS+L Score for outcomes were 0.331~0.415. The AUROC and AUPRC values of the NEWS+L Score were greater than those of NEWS alone (AUROC 0.744~0.806 and AUPRC 0.316~0.380 for NEWS). Using the equation, 48 hours hospital mortality rates for NEWS+L Score of 5, 10 and 15 were found to be 1.1%, 3.1% and 8.8%, and for the composite outcome 9.2%, 27.5% and 58.5%, respectively.

CONCLUSION

The NEWS+L Score has acceptable to excellent performance for risk estimation among undifferentiated adult ED patients, and outperforms NEWS alone.

Admission lactate level and the GRACE 2.0 score are independent and additive predictors of 30-day mortality of STEMI patients treated with primary PCI-Results of a real-world registry

BACKGROUND

In many of the risk estimation algorithms for patients with ST-elevation myocardial infarction (STEMI), heart rate and systolic blood pressure are key predictors. Yet, these parameters may also be altered by the applied medical treatment / circulatory support without concomitant improvement in microcirculation. Therefore, we aimed to investigate whether venous lactate level, a well-known marker of microcirculatory failure, may have an added prognostic value on top of the conventional variables of the "Global Registry of Acute Coronary Events" (GRACE) 2.0 model for predicting 30-day all-cause mortality of STEMI patients treated with primary percutaneous coronary intervention (PCI).

METHODS

In a prospective single-center registry study conducted from May 2020 through April 2021, we analyzed data of 323 cases. Venous blood gas analysis was performed in all patients at admission. Nested logistic regression models were built using the GRACE 2.0 score alone (base model) and with the addition of venous lactate level (expanded model) with 30-day all-cause mortality as primary outcome measure. Difference in model performance was analyzed by the likelihood ratio (LR) test and the integrated discrimination improvement (IDI). Independence of the predictors was evaluated by the variance inflation factor (VIF). Discrimination and calibration was characterized by the c-statistic and calibration intercept / slope, respectively.

RESULTS

Addition of lactate level to the GRACE 2.0 score improved the predictions of 30-day mortality significantly as assessed by both LR test (LR Chi-square = 8.7967, p = 0.0030) and IDI (IDI = 0.0685, p = 0.0402), suggesting that the expanded model may have better predictive ability than the GRACE 2.0 score. Furthermore, the VIF was 1.1203, indicating that the measured lactate values were independent of the calculated GRACE 2.0 scores.

CONCLUSIONS

Our results suggest that admission venous lactate level and the GRACE 2.0 score may be independent and additive predictors of 30-day all-cause mortality of STEMI patients treated with primary PCI.

Prognostic role of elevated lactate in acute pulmonary embolism: A systematic review and meta-analysis

BACKGROUND

Previous studies have shown elevated lactate was a good predictor for the prognosis of pulmonary embolism (PE). However, due to low number of patients and different expression of blood lactate in separate study, these results are inconsistent. Therefore, the aim of this meta-analysis is to evaluate the relationship between increased lactate levels and adverse outcome in acute PE.

METHOD

The literatures search was conducted in PubMed, Web of Science, and EMBASE until May 29, 2021.

RESULTS

Finally, 6 studies with 1706 patients were included in our meta-analysis. High lactate levels were markedly associated with overall mortality both in unselected PE patients (OR 5.13, 95% CI: 3.36-7.86, p < .00,001) and normotensive PE patients (OR 4.54, 95% CI: 2.64-7.80, p < .00,001), and PE-related short-term mortality in patients with elevated lactate was significantly higher than that in patients with normal levels (OR 9.05, 95% CI :4.08-20.10, p < .00,001). The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of lactate for predicting overall mortality in patients with acute PE were 0.67 (95% CI: 0.43-0.85), 0.73 (95% CI: 0.60-0.83), 2.5 (95% CI: 2.0-3.1), and 0.45 (95% CI: 0.26-0.78), respectively. The area under SROC curve (AUC) was 0.76 (95% CI: 0.73-0.80).

CONCLUSION

The result of our meta-analysis indicate that elevated blood lactate is a good predictor for overall mortality and short-term mortality in patients with acute PE, and can be routinely measured in risk stratification, but its prognostic role in patients with different risk classes still need to be verified.

Principles of Resuscitation

Shock from all causes carries a high mortality. Rapid and intentional intervention to resuscitate can reduce mortality and organ injury. Approaches to fluid resuscitation, vasopressor use as well as commonly assessed laboratory values are reviewed in this paper.

Venous lactate improves the prediction of in-hospital adverse outcomes in normotensive pulmonary embolism

BACKGROUND

Arterial lactate is an established risk marker in patients with pulmonary embolism (PE). However, its clinical applicability is limited by the need of an arterial puncture. In contrast, venous lactate can easily be measured from blood samples obtained via routine peripheral venepuncture.

METHODS

We investigated the prognostic value of venous lactate with regard to in-hospital adverse outcomes and mortality in 419 consecutive PE patients enrolled in a single-center registry between 09/2008 and 09/2017.

RESULTS

An optimised venous lactate cut-off value of 3.3 mmol/l predicted both, in-hospital adverse outcome (OR 11.0 [95% CI 4.6-26.3]) and all-cause mortality (OR 3.8 [95%CI 1.3-11.3]). The established cut-off value for arterial lactate (2.0 mmol/l) and the upper limit of normal for venous lactate (2.3 mmol/l) had lower prognostic value for adverse outcomes (OR 3.6 [95% CI 1.5-8.7] and 5.7 [95% CI 2.4-13.6], respectively) and did not predict mortality. If added to the 2019 European Society of Cardiology (ESC) algorithm, venous lactate <2.3 mmol/l was associated with a high negative predictive value (0.99 [95% CI 0.97-1.00]) for adverse outcomes in intermediate-low-risk patients, whereas levels ≥3.3 mmol/l predicted adverse outcomes in the intermediate-high-risk group (OR 5.2 [95% CI 1.8-15.0]).

CONCLUSION

Venous lactate above the upper limit of normal was associated with increased risk for adverse outcomes and an optimised cut-off value of 3.3 mmol/l predicted adverse outcome and mortality. Adding venous lactate to the 2019 ESC algorithm may improve risk stratification. Importantly, the established cut-off value for arterial lactate has limited specificity in venous samples and should not be used.

Prospective evaluation of plasma lactate parameters for prognosticating dogs with shock

OBJECTIVE

To determine whether admission venous plasma lactate concentration, serially calculated lactate variables, or the Acute Patient Physiologic and Laboratory Evaluation (APPLE_fast ) score could discriminate hospital survivors from non-survivors in dogs presenting to the emergency department with clinical signs of shock.

DESIGN

Prospective case series performed over a 24-month period.

SETTING

Large urban private teaching hospital.

ANIMALS

Seventy-one dogs admitted to the ICU with initial peripheral venous plasma lactate concentration > 2.5 mmol/L and clinical and hemodynamic parameters consistent with shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Heart rate, systolic blood pressure, temperature, initial venous plasma lactate, and APPLE_fast score were recorded at admission. Lactate concentrations were serially recorded at predefined time points and used to calculate lactate variables, including lactime (time lactate > 2.5 mmol/L), lactate clearance ([lactate_initial - lactate_delayed ]/ lactate_initial × 100), and LAC_AREA (area under the lactate concentration versus time curve). Primary outcome was survival to discharge. Overall survival rate was 61%. Admission plasma lactate did not differ between groups (P = 0.28). Lactime was shorter in survivors vs non-survivors (P = 0.03). Lactate clearance at hours (h) 1, 4, 10, and 16 was greater in survivors vs non-survivors (P < 0.05). Final plasma lactate clearance differed between groups (P < 0.05). LAC_AREA at time intervals 1 to 4 hours, 4 to 10 hours, 10 to 16 hours, and 16 to 24 hours was larger in non-survivors vs survivors (P < 0.05). Total LAC_AREA did not differ between groups (P = 0.51). Admission APPLE_fast was not different between survivors and non-survivors (P = 0.16).

CONCLUSIONS

While neither single APPLE_fast nor admission plasma lactate concentration could discriminate between hospital survivors and non-survivors, measures of lactate clearance can prognosticate survival in dogs with shock.

Effect of tourniquet time on whole blood point-of-care lactate concentration: A healthy human volunteer study

OBJECTIVE

Lactate is frequently utilised in clinical practice. Some have concerns that tourniquet application for venous blood collection may falsely elevate venous lactate. The objective of the present study was to determine the effect of tourniquet time on varying venous lactate concentrations.

METHODS

This is a healthy volunteer study, in which subjects were their own controls. A cannula was inserted into each arm, with a tourniquet remaining on one. Subjects were allocated to one of three groups; rest (no activity), exercise (maximal exertion to elevate lactate concentrations) with immediate tourniquet application or exercise with delayed (5-min post-exercise) tourniquet application. In all blood was drawn simultaneously from both cannulas at 0, 2.5, 5, 10 and 15-min post-tourniquet application and analysed for lactate on a point-of-care device. The primary outcome was a clinically significant difference (>1 mmol/L) in tourniquet versus non-tourniquet arm lactate concentration.

RESULTS

There were 10 subjects per group; the exercise groups achieved a mean maximum lactate concentration of 10.4 mmol/L (standard deviation [SD] 3.6) (exercise with immediate tourniquet application group) and 8.9 mmol/L (SD 2.5) (exercise with delayed tourniquet application group). There was no clinically significant increase in lactate concentration in the tourniquet compared to non-tourniquet arm in all groups, across all tourniquet application times, and over a range of lactate concentrations. In the rest group after 15-min of tourniquet application the mean lactate concentration of the tourniquet versus non-tourniquet arm was 0.91 mmol/L (SD 0.55) versus 0.89 mmol/L (SD 0.46) (P = 0.99), respectively.

CONCLUSION

In the present study tourniquet application for blood collection did not significantly increase lactate concentration. Hence, clinically a raised venous lactate concentration should not be attributed to prolonged tourniquet application.

Using pCO2 Gap in the Differential Diagnosis of Hyperlactatemia Outside the Context of Sepsis: A Physiological Review and Case Series

INTRODUCTION

There is an inverse relationship between cardiac output and the central venous-arterial difference of partial pressures of carbon dioxide (pCO2 gap), and pCO2 gap has been used to guide early resuscitation of septic shock. It can be hypothesized that pCO2 gap can be used outside the context of sepsis to distinguish type A and type B lactic acidosis and thereby avoid unnecessary fluid resuscitation in patients with high lactate, but without organ hypoperfusion.

METHODS

We performed a structured review of the literature enlightening the physiological background. Next, we retrospectively selected a series of case reports of nonseptic critically ill patients with elevated lactate, in whom both arterial and central venous blood gases were simultaneously measured and the diagnosis of either type A or type B hyperlactataemia was conclusively known. In these cases, we calculated venous-arterial CO2 and O2 content differences and pCO2 gap.

RESULTS

Based on available physiological data, pCO2 can be considered as an acceptable surrogate of venous-arterial CO2 content difference, and it should better reflect cardiac output than central venous saturation or indices based on venous-arterial O2 content difference. In our case report of nonseptic patients, we observed that if global hypoperfusion was present (i.e., in type A lactic acidosis), pCO2 gap was elevated (>1 kPa), whilst in the absence of it (i.e., in type B lactic acidosis), pCO2 gap was low (<0.5 kPa).

CONCLUSION

Physiological rationale and a small case series are consistent with the hypothesis that low pCO2 gap in nonseptic critically ill is suggestive of the absence of tissue hypoperfusion, mandating the search for the cause of type B lactic acidosis rather than administration of fluids or other drugs aimed at increasing cardiac output.

Relation Between Central Venous, Peripheral Venous and Arterial Lactate Levels in Patients With Sepsis in the Emergency Department

Background

Sepsis and multi-organ failure remain a major clinical problem with high morbidity and mortality worldwide. Lactate measurement remains part of the initial assessment and management of patients with sepsis. Although arterial blood is most commonly used for lactate measurement, there is increasing use of peripheral venous lactate for initial assessment and for monitoring of response to treatment in patients with sepsis. The aim of this study was to evaluate the relation between lactate levels measured from central line, peripheral vein and arterial line in patients treated for sepsis in the emergency department (ED).

Methods

This prospective study enrolled 31 patients with diagnosis of sepsis who were evaluated and treated in the ED of a university hospital. During initial resuscitation, blood samples from the artery, peripheral vein and central vein (when available) were collected and lactate concentrations were measured. Correlation between lactate values from the three different locations was assessed using Pearson correlation. Bland-Altman plots were used to evaluate agreement between lactate measurements in different sampling locations. All patients were eventually admitted to the Internal Medicine Department ward or to the intensive care unit (ICU) for further treatment.

Results

Our data showed strong, highly significant correlation between arterial and peripheral venous lactate levels (r = 0.880, P < 0.0001), between arterial and central venous blood lactate (r = 0.898, P < 0.0001) and between central and peripheral venous blood lactate (r = 0.941, P < 0.0001).

Conclusions

In this study we observed strong correlation between arterial, central vein and peripheral vein lactate concentrations in 31 patients assessed and treated for sepsis. We suggest that lactate measurement in peripheral venous blood could be used for screening and for monitoring response to therapy in sepsis patients. However, because this is a small study in only 31 patients and published data are limited, larger studies are needed in order to confirm the validity of our findings.

Demystifying Lactate in the Emergency Department

The role of lactic acid and its conjugate base, lactate, has evolved during the past decade in the care of patients in the emergency department (ED). A recent national sepsis quality measure has led to increased use of serum lactate in the ED, but many causes for hyperlactatemia exist outside of sepsis. We provide a review of the biology of lactate production and metabolism, the many causes of hyperlactatemia, and evidence on its use as a marker in prognosis and resuscitation. Additionally, we review the evolving role of lactate in sepsis care. We provide recommendations to aid lactate interpretation in the ED and highlight areas for future research.

Agreement between arterial and peripheral venous lactate levels in the ED: A systematic review

BACKGROUND

In the Emergency Department, lactate measurement is a useful tool to risk-stratify critically ill patients. However, it is unclear whether arterial or peripheral venous lactate levels can be used interchangeably for this purpose. In this systematic review, we provide an overview of studies investigating the agreement between arterial and peripheral venous lactate levels in the Emergency Department.

METHODS

PubMed, Embase, the Cochrane Central Register of Controlled Trials/Wiley, Web of Science/Clarivate Analytics, and references of selected articles were assessed for all studies comparing arterial and peripheral venous lactate levels in adult patients in the emergency department. Two reviewers independently screened all potentially relevant titles and abstracts for eligibility using a standardized data-worksheet.

RESULTS

Nine studies were included. Peripheral venous lactate levels tend to be higher than arterial lactate levels with mean differences ranging from 0.18 mmol/l to 1.06 mmol/l. Importantly, poorer agreement occurs in hyperlactatemia. At a cut-of level of 1.6 mmol/l, peripheral venous lactate can rule out arterial hyperlactatemia with a sensitivity between 94% and 100%. At a cut off value of 2 mmol/l, sensitivities of 97% and 100% were found.

CONCLUSION

Agreement between arterial and peripheral venous lactate is poor in hyperlactatemia, making peripheral venous lactate an unreliable parameter to use interchangeably in the ED. In clinical practice, peripheral venous lactate can be used as a screening tool to rule out arterial hyperlactatemia at a cut-off value of 2 mmol/l. However, hyperlactatemia should be confirmed using arterial sampling in case of a peripheral venous lactate level > 2 mmol/l.

Early Lactate Dynamics in Critically Ill Non-Traumatic Patients in a Resuscitation Room of a German Emergency Department (OBSERvE-Lactate-Study)

BACKGROUND

Management of critically ill non-trauma patients in the resuscitation room of an emergency department (ED) is very challenging, and it is difficult to identify patients with a higher risk of death. Previous studies have shown that lactate indices can predict survival for selected diseases and syndromes.

OBJECTIVE

As reported for other patient populations, we set out to determine whether admission lactate or lactate dynamics (LD) within 24 h can predict 30-day mortality in unselected critically ill non-traumatic patients.

METHODS

In this retrospective study over a 1-year period, admission lactate, time weighted average lactate (Lac_TW) and LD of all critically ill adult patients admitted from ED to intensive care unit were analyzed. A linear regression model was implemented to estimate lactate data 1 h after admission.

RESULTS

The admission lactate, Lac_TW, and LD within 24 h were analyzed from 392 critically ill patients. The overall 30-day mortality rate was around 29%. Admission lactate (4.1 ± 4.0 mmol/L vs. 6.6 ± 6.1 mmol/L; p < 0.01) and Lac_TW (1.8 ± 1.7 mmol/L vs. 4.1 ± 4.8 mmol/L; p < 0.01) were different between survivors and non-survivors. LD between survivors and non-survivors did not differ at 1 h, 6 h, 12 h, or 24 h. After excluding patients with out-of-hospital or in-hospital cardiac arrest during resuscitation room management, admission lactate and LD between survivors and non-survivors did not differ at 1 h, 12 h, and 24 h. LD at 6 h (44% ± 42% vs. 33% ± 58%; p = 0.042) and Lac_TW (1.7 ± 1.6 mmol/L vs. 2.6 ± 3.0 mmol/L; p < 0.01) did differ.

CONCLUSIONS

In critically ill ED patients initially requiring treatment in a resuscitation room setting, LD at 6 h and Lac_TW may predict their survival beyond 30 days. These findings need to be confirmed in a prospective study design.

Lactate - Arterial and Venous Agreement in Sepsis: a prospective observational study

BACKGROUND

Sepsis is a common condition in the emergency department (ED). Lactate measurement is an important part of management: arterial lactate (A-LACT) measurement is the gold standard. There is increasing use of peripheral venous lactate (PV-LACT); however, there is little research supporting the interchangeability of the two measures.If PV-LACT has good agreement with A-LACT, it would significantly reduce patient discomfort and the risks of arterial sampling for a large group of acutely unwell patients, while allowing faster and wider screening, with potential reduced costs to the healthcare system.

OBJECTIVE

The aim of this study is to determine the agreement between PV-LACT and A-LACT in septic patients attending the ED.

METHODS

We carried out a prospective observational cohort study of 304 consented patients presenting with sepsis to a single UK NHS ED (110 000 adult attendances annually) taking paired PV-LACT and A-LACT. Bland-Altman analysis was carried out to determine agreement. Receiver operating characteristic curves and 2×2 tables were constructed to explore the predictive value of PV-LACT for A-LACT.

RESULTS

The mean difference (PV-LACT-A-LACT) is 0.4 mmol/l [95% confidence interval (CI): 0.37-0.45], with 95% limits of agreement from -0.4 (95% CI: -0.45 to -0.32) to 1.2 (95% CI: 1.14-1.27). A PV-LACT of at least 2 mmol/l predicts an A-LACT of at least 2 with 100% sensitivity (95% CI: 89-100%) and 83% specificity (95% CI: 77-87%).

CONCLUSION

This study is the largest comparing the two measurements, and shows good clinical agreement. We recommend using PV-LACT in the routine screening of septic patients. A PV-LACT less than 2 mmol/l is predictive of an A-LACT less than 2 mmol/l.

Peripheral measurements of venous oxygen saturation and lactate as a less invasive alternative for hemodynamic monitoring

Background

Peripheral measurement of venous oxygen saturation and lactate is a less invasive alternative to monitor tissue oxygenation as compared to measurements from a central venous catheter. However, there is a lack of evidence to support the use of peripheral measurements. In this study, we investigated the agreement between central and peripheral venous oxygen saturation and lactate.

Methods

We conducted a prospective observational study including 115 patients who underwent elective cardiac surgery between April and May 2015 at Rigshospitalet, Copenhagen, Denmark. Measurements were obtained simultaneously at induction of anaesthesia, upon arrival in the ICU and 3–4 h postoperatively. Bias and trending ability was identified using Bland-Altman analysis and a four-quadrant plot.

Results

Bias was 13.37% for venous oxygen saturation preoperatively (95% CI: 11.52–15.22, LoA: ±19.10, PE: 22.08%), 11.29% at arrival to the ICU (95% CI: 8.81–13.77, LoA: ±25.10, PE: 32.39%) and 16.49% at 3–4 h postoperatively (95% CI: 14.16–18.82, LoA: ±21.20, PE: 26.82%). A four-quadrant plot demonstrated an 89% concordance. Central and peripheral lactate showed a bias of 0.14 mmol/L preoperatively (95% CI: 0.11–0.17, LoA: ±0.30, PE: 32.08%), 0.16 mmol/L at arrival to ICU (95% CI: 0.09–0.23, LoA: ±0.70, PE: 38.88%) and 0.23 mmol/L at 3–4 h postoperatively (95% CI: 0.11–0.35, LoA: ±0.50, 25.18%).

Discussion

Measurements of peripheral oxygen saturation and lactate may be valuable in an emergency setting, avoiding unnecessary and time consuming application of a CVC.

Conclusion

We found a high bias but an acceptable trending ability between central and peripheral venous oxygenation. Central and peripheral lactate had excellent agreement. Further studies are necessary to validate the use of peripheral venous samples to identify patients at risk of impaired tissue oxygenation.

Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement

OBJECTIVE

To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate.

DATA SOURCES

Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na⁺ -K⁺ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics.

CONCLUSION

The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.

Repeat lactate level predicts mortality better than rate of clearance

BACKGROUND

Lactate clearance has been developed into a marker of resuscitation in trauma, but no study has compared the predictive power of the various clearance calculations. Our objective was to determine which method of calculating lactate clearance best predicted 24-hour and in-hospital mortality after injury.

STUDY DESIGN

Retrospective chart review of patients admitted to a Level-1 trauma center directly from the scene of injury from 2010 to 2013 who survived >15min, had an elevated lactate at admission (≥3mmol/L), followed by another measurement within 24h of admission. Lactate clearance was calculated using five models: actual value of the repeat level, absolute clearance, relative clearance, absolute rate, and relative rate. Models were compared using the areas under the respective receiver operating curves (AUCs), with an endpoint of death at 24h and in-hospital mortality.

RESULTS

3910 patients had an elevated admission lactate concentration on admission (mean=5.6±3.0mmol/L) followed by a second measurement (2.7±1.8mmol/L). Repeat absolute measurement best predicted 24-hour (AUC=0.85, 95% CI: 0.84-0.86) and in-hospital death (AUC=0.77; 95% CI, 0.76-0.78). Relative clearance was the best model of lactate clearance (AUC=0.77, 95% CI: 0.75-0.78 and AUC=0.705, 95% CI: 0.69-72, respectively) (p<0.0001 for each). A sensitivity analysis using a range of initial lactate measures yielded similar results.

CONCLUSIONS

The absolute value of the repeat lactate measurement had the greatest ability to predict mortality in injured patients undergoing resuscitation.

Prognostic Value of Cardiac Troponin I and L-Lactate in Blood of Dairy Cows Affected by Downer Cow Syndrome

Background

The downer cow syndrome (DCS) is a challenging health issue in the dairy industry. No cow‐side test is available to provide an accurate prognosis for DCS cases in farm settings.

Hypothesis/Objectives

Local or systemic hypoperfusion and myocardial lesions lead to an increase in blood concentration of biomarkers cardiac troponin I (cTnI) and L‐lactate. The objective was to determine the prognostic values of these biomarkers assessed cow‐sides in addition to clinical examinations in prognostication of a negative outcome (NO: death or euthanasia within 7 days).

Animals

218 client‐owned dairy cows affected by DCS.

Methods

In a prospective study, animals were monitored for 60 days after inclusion of each cow. Blood cTnI and L‐lactate concentrations were measured on the day of inclusion. The prognostic accuracy of both biomarkers and physical examination variables was estimated to predict NO. A mixed multivariable logistic regression model was used for data analysis.

Results

Prevalence of NO in this study was 63% on day 7. Troponin concentrations greater than 0.7 ng/mL had sensitivity and specificity of 54.1% (95% CI: 45.3–62.7%) and 78.4% (95% CI: 67.3–87.1%), respectively, for predicting NO. Blood L‐lactate was not associated with the outcome. The multivariable model revealed that heart rate >100 bpm (OR; 95% CI: 3.7; 1.3–10.2) and cTnI > 0.7 ng/mL (OR; 95% CI: 5.5; 2.1–14.6) were associated with the risk of NO.

Conclusions and Clinical Importance

Hypertroponinemia and tachycardia were associated with reduced survival in DCS cases. The use of cow‐side blood cTnI concentrations and heart rate could help to rapidly identify cows in farm setting that have poor chances of recovery and would benefit from a more aggressive treatment or euthanasia.

End Points of Sepsis Resuscitation

Resuscitation goals for the patient with sepsis and septic shock are to return the patient to a physiologic state that promotes adequate end-organ perfusion along with matching metabolic supply and demand. Ideal resuscitation end points should assess the adequacy of tissue oxygen delivery and oxygen consumption, and be quantifiable and reproducible. Despite years of research, a single resuscitation end point to assess adequacy of resuscitation has yet to be found. Thus, the clinician must rely on multiple end points to assess the patient's overall response to therapy. This review will discuss the role and limitations of central venous pressure (CVP), mean arterial pressure (MAP), and cardiac output/index as macrocirculatory resuscitation targets along with lactate, central venous oxygen saturation (ScvO₂), central venous-arterial CO₂ gradient, urine output, and capillary refill time as microcirculatory resuscitation endpoints in patients with sepsis.

Agreement between arterial and venous lactate in emergency department patients: a prospective study of 157 consecutive patients

INTRODUCTION

In the emergency department (ED), lactate is routinely used for risk stratification. Whether venous or arterial lactate measured on blood gas is interchangeable is not known. We hypothesized that venous lactate can be used instead of arterial lactate for the evaluation of acute patients in the ED.

PATIENTS AND METHODS

This was a prospective single-center study. All patients requiring a lactate measurement were enrolled and we simultaneously drew arterial and venous blood. We followed up all patients to hospital discharge. Our primary aim was to evaluate agreements between the two measurements using Bland and Altman plots with the report of bias (mean difference) and limits of agreements. We also aimed to determine the rate of misclassification (defined as one measurement<1.8 mmol/l and the other>2.2). Our secondary aim was to evaluate their respective prognostic value to predict in-hospital death or admission in the ICU longer than 72 h.

RESULTS

The mean age of the 132 analyzed patients was 62 years (SD: 18 years), and 59% were men. The mean difference (bias) between arterial and venous lactate was -0.6 mmol/l (limits of agreement: -1.7 to 0.6 mmol/l). The rate of misclassification was 8% (95% confidence interval: 3-2%). Both methods present similar performances for the prediction of poor outcomes, with an area under the receiving operator characteristic curves of 0.67 for both. Results were similar when focused only on septic patients.

CONCLUSION

Venous and arterial lactates do not agree well, and there is a high misclassification rate. Venous lactate does not appear to be interchangeable with arterial sampling.

The Practice Guidelines for Primary Care of Acute Abdomen 2015

BACKGROUND

Since acute abdomen requires accurate diagnosis and treatment within a particular time limit to prevent mortality, the Japanese Society for Abdominal Emergency Medicine in collaboration with four other medical societies launched the Practice Guidelines for Primary Care of Acute Abdomen that were the first English guidelines in the world for the management of acute abdomen. Here we provide the highlights of these guidelines [all clinical questions (CQs) and recommendations are shown in supplementary information].

METHODS

A systematic and comprehensive evaluation of the evidence for epidemiology, diagnosis, differential diagnosis, and primary treatment for acute abdomen was performed to develop the Practice Guidelines for Primary Care of Acute Abdomen 2015. Because many types of pathophysiological events underlie acute abdomen, these guidelines cover the primary care of adult patients with nontraumatic acute abdomen.

RESULTS

A total of 108 questions based on 9 subject areas were used to compile 113 recommendations. The subject areas included definition, epidemiology, history taking, physical examination, laboratory test, imaging studies, differential diagnosis, initial treatment, and education. Japanese medical circumstances were considered for grading the recommendations to assure useful information. The two-step methods for the initial management of acute abdomen were proposed. Early use of transfusion and analgesia, particularly intravenous acetaminophen, were recommended.

CONCLUSIONS

The Practice Guidelines for Primary Care of Acute Abdomen 2015 have been prepared as the first evidence-based guidelines for the management of acute abdomen. We hope that these guidelines contribute to clinical practice and improve the primary care and prognosis of patients with acute abdomen.

Alcohol consumption decreases lactate clearance in acutely injured patients

INTRODUCTION

Alcohol, a common risk factor for injury, has direct toxic effects on the liver. The use of lactate clearance has been well described as an indicator of the adequacy of resuscitation in injured patients. We investigated whether acutely injured patients with positive blood alcohol content (+BAC) had less lactate clearance than sober patients.

METHODS

We conducted a retrospective cohort study of acutely injured patients treated at an urban Level 1 trauma centre between January 2010 and December 2012. Blood alcohol and venous lactate levels were measured on all patients at the time of arrival. Study subjects were patients transported directly from the scene of injury, who had an elevated lactate concentration on arrival (≥3.0mmol/L) and at least one subsequent lactate measurement within 24h after admission. Lactate clearance ([Lactate1-Lactate2]/Lactate1) was calculated for all patients. Chi-squared tests were used to compare values from sober and intoxicated subjects. Lactate clearance was plotted against alcohol levels and stratified by age and Injury Severity Score (ISS).

RESULTS

Serial lactate concentration measurements were obtained in 3910 patients; 1674 of them had +BAC. Patients with +BAC were younger (mean age: 36.6 [SD 14.7] vs 41.0 [SD 19.9] years [p=0.0001]), were more often male (83.4% vs 75.9% [p=0.0001]), had more minor injuries (ISS<9) (33.8% vs 27.1% [p=0.0001]), had a lower in-hospital mortality rate (1.4% vs 3.9% [p=0.0001]), but also had lower average lactate clearance (37.8% vs 47.6% [p=0.0001]). The lactate clearance of the sober patients (47.6 [SD 33.5]) was twice that of those with +BAC >400 (23.5 [SD 6.5]). Lactate clearance decreased with increasing BAC irrespective of age and ISS.

CONCLUSIONS

In a large group of acutely injured patients, a dose-dependent decrease in lactate clearance was seen in those with elevated BAC. This relationship will cause a falsely elevated lactate reading or prolong lactate clearance and should be taken into account when evaluating patients with +BAC.

The Correlation Between Arterial Lactate and Venous Lactate in Patients With Sepsis and Septic Shock

BACKGROUND

Applying peripheral venous lactate instead of arterial lactate in clinical practice is questionable because of deviation between both values. We aimed to find the relationship between the arterial lactate and the peripheral venous lactate before reasoned that the venous lactate could be used in substitution to the arterial lactate in sepsis.

METHODS

We conducted a prospective, cross-sectional study at a university hospital. The patients with sepsis in ICU who required lactate level monitoring were enrolled in this research. The correlation and agreement between arterial lactate (A-LACT) and peripheral venous lactate (V-LACT) were the primary outcomes.

RESULTS

A total of 63 paired samples were collected. The A-LACT and V-LACT were strongly correlated ( r = .934, P < .0001, r² = .873). The regression equation was A-LACT = (0.934 × V-LACT) - 0.236. The mean difference between V-LACT and A-LACT was 0.66 ± 1.53 mmol/L. The 95% limits of agreement were between -3.66 and 2.33 mmol/L. The V-LACT ≥ 4 mmol/L can predict A-LACT level ≥ 4 mmol/L with 87.5% sensitivity and 91.5% specificity, and the area under receiver operating characteristic curve was 0.948.

CONCLUSION

The present study demonstrated a strong correlation between A-LACT and V-LACT, but an agreement between both parameters was poor. We suggest not to use the V-LACT in substitution to the A-LACT in sepsis regarding the absolute value and clearance rate, but the V-LACT ≥ 4.5 mmol/L may be used for predicting the A-LACT ≥ 4 mmol/L.

Predictive value of the National Early Warning Score-Lactate for mortality and the need for critical care among general emergency department patients

STUDY OBJECTIVES

What is the predictive value of the National Early Warning Score-Lactate (NEWS-L) score for mortality and the need for critical care in general emergency department (ED) patients?

METHODS

In this retrospective cohort study, we enrolled all adult patients who visited the ED of an urban academic tertiary-care university hospital in South Korea over 2 consecutive months. The primary outcome was 2-day mortality. The secondary outcomes were the need for critical care (advanced airway use, vasopressor or inotropic agent use, intensive care unit admission) during an ED stay; 2-day composite outcome (2-day mortality and the need for critical care); 7-day mortality; and in-hospital mortality.

RESULTS

During the study period, 4624 adult patients visited the ED. Of these, 87 (1.9%) died within 2 days. In total, 481 patients (10.4%) required critical care during their ED stay. The 2-day composite outcome, 7-day mortality, and in-hospital mortality were 10.9% (503/4624), 2.5% (116/4624), and 3.9% (182/4624), respectively. The NEWS-L demonstrated excellent predictive value for 2-day mortality with an area under the receiver operating characteristic curve (AUROC) of 0.96 (95% confidence interval [CI], 0.94-0.98); this value was better than that of the NEWS alone (AUROC 0.94 [95% CI, 0.91-0.96], P=.002). The AUROC of the NEWS-L for the need for critical care was 0.83 (95% CI, 0.81-0.85); for the 2-day composite outcome, it was 0.84 (95% CI, 0.82-0.86); for 7-day mortality, it was 0.94 (95% CI, 0.92-0.96); and for in-hospital mortality, it was 0.87 (95% CI, 0.85-0.90). Logistic regression results confirmed that the ratio of the NEWS to the initial lactate level was 1:1. Similar results were obtained in the subgroup analyses (disease-infection, disease-vascular and heart, disease-others, and nondisease). The high-risk NEWS-L group (NEWS-L≥7, 9.4% of all patients) had an adjusted odds ratio of 28.67 (12.66-64.92) for 2-day mortality in the logistic regression model adjusted for basic characteristics.

CONCLUSION

The NEWS-L can provide excellent discriminant value for predicting 2-day mortality in general ED patients, and it has the best discriminant value regarding the need for critical care and composite outcomes. The NEWS-L may be helpful in the early identification of at-risk general ED patients.

Use of serum lactate levels to predict survival for patients with out-of-hospital cardiac arrest: A cohort study

OBJECTIVES

We examined the association of serum lactate levels and early lactate clearance with survival to hospital discharge for patients suffering an out-of-hospital cardiac arrest (OHCA).

METHODS

A retrospective cohort analysis was performed of patients with OHCA transported by ambulance to two adult tertiary hospitals in Perth, Western Australia. Exclusion criteria were traumatic cardiac arrest, return of spontaneous circulation prior to the arrival of the ambulance, age less than 18 years and no serum lactate levels recorded. Serum lactate levels recorded for up to 48 h post-arrest were obtained from the hospital clinical information system, and lactate clearance over 48 h was calculated. Descriptive and logistic regression analyses were conducted.

RESULTS

There were 518 patients with lactate values, of whom 126 (24.3%) survived to hospital discharge. Survivors and non-survivors had different mean initial lactate levels (mean ± SD 6.9 ± 4.7 and 12.2 ± 5.5 mmol/L, respectively; P < 0.001). Lactate clearance was higher in survivors. Lactate levels for non-survivors did not decrease below 2 mmol/L until at least 30 h after the ambulance call.

CONCLUSION

In OHCA patients who had serum lactate levels measured, both lower initial serum lactate and early lactate clearance in the first 48 h following OHCA were associated with increased likelihood of survival. However, the use of lactate in isolation as a predictor of survival or neurological outcome is not recommended. Prospective studies that minimise selection bias are required to determine the clinical utility of serum lactate levels in OHCA patients.

Validation of modified early warning score using serum lactate level in community-acquired pneumonia patients. The National Early Warning Score-Lactate score

STUDY OBJECTIVE

The aim of this study was to investigate the prognostic prediction power of a newly introduced early warning score modified by serum lactate level, the National Early Warning Score-Lactate (NEWS-L) score, among community-acquired pneumonia (CAP) patients. We also compared the NEWS-L score with the pneumonia severity index (PSI) and CURB-65.

METHODS

We designed a retrospective observational study and collected data on confirmed adult CAP patients who visited the study hospital between October 2013 and September 2014. Variables relevant to, the NEWS-L score, PSI, and CURB-65 were extracted from electronic medical records. Survival status at hospital discharge was determined in the same manner. The NEWS-L score was calculated as NEWS-L=NEWS+serum lactate level (mmol/L). The NEWS-L was divided into quartiles. The ability to predict mortality was assessed through area under the receiver operating characteristic curve analysis and calibration analysis.

RESULTS

A total of 553 patients were enrolled, and the inpatient mortality rate was 10.8% (n=60). Mortality rates increased incrementally in conjunction with the NEWS-L quartiles: first quartile, 2.2%; second quartile, 7.9%; third quartile, 9.6%; and fourth quartile, 23.9%. The area under the receiver operating characteristic curve of the NEWS-L score was 0.73 (95% confidence interval [CI], 0.66-0.80), which showed no significant difference from that of the PSI (0.68; 95% CI, 0.61-0.76; P=.28) and CURB-65 (0.66; 95% CI, 0.59-0.73; P=.06).

CONCLUSIONS

The newly introduced early warning score modified by serum lactate level, NEWS-L score, was comparable to PSI and CURB-65, for predicting inpatient mortality among adult CAP patients.

Failure to clear elevated lactate predicts 24-hour mortality in trauma patients

BACKGROUND

Lactate clearance is a standard resuscitation goal in patients in nontraumatic shock but has not been investigated adequately as a tool to identify trauma patients at risk of dying. Our objective was to determine if trauma patients with impaired lactate clearance have a higher 24-hour mortality rate than patients whose lactate concentration normalizes.

METHODS

A retrospective chart review identified patients who were admitted directly from the scene of injury to an urban trauma center between 2010 and 2013 and who had at least one lactate concentration measurement within 24 hours. Transfers, patients without lactate measurement, and those who were dead on arrival were excluded. Of the 26,545 screened patients, 18,304 constituted the initial lactate measurement population, and 3,887 were the lactate clearance cohorts.

RESULTS

Initial lactate had an area under the receiver operating characteristic curve of 0.86 and 0.73 for mortality at 24 hours and in the hospital, respectively. An initial concentration of 3 mmol/L or greater had a sensitivity of 0.86 and a specificity of 0.73 for mortality at 24 hours. The mortality rate among patients with elevated lactate concentrations (n = 2,381; 5.6 [2.8] mmol/L) that did not decline to less than 2.0 mmol/L in response to resuscitative efforts (mean [SD] second measurement, 3.7 [1.9] mmol/L) was nearly seven times higher (4.1% vs. 0.6%, p < 0.001) than among those with an elevated concentration (n = 1,506, 5.3 [2.7] mmol/L) that normalized (1.4 [0.4] mmol/L). Logistic regression analysis showed that failure to clear lactate was associated with death more than any other feature (odds ratio, 7.4; 95% confidence interval, 1.5-35.5), except having an Injury Severity Score (ISS) greater than 25 (odds ratio, 8.2; 95% confidence interval, 2.7-25.2).

CONCLUSION

Failure to clear lactate is a strong negative prognostic marker after injury. An initial lactate measurement combined with a second measurement for high-risk individuals might constitute a useful method of risk stratifying injured patients.

LEVEL OF EVIDENCE

Prognostic study, level III.

Practice Guidelines for Primary Care of Acute Abdomen 2015

Since acute abdomen requires accurate diagnosis and treatment within a particular time limit to prevent mortality, the Japanese Society for Abdominal Emergency Medicine, in collaboration with four other medical societies, launched the Practice Guidelines for Primary Care of Acute Abdomen that were the first English guidelines in the world for the management of acute abdomen. Here we provide the highlights of these guidelines (all clinical questions and recommendations were shown in supplementary information). A systematic and comprehensive evaluation of the evidence for epidemiology, diagnosis, differential diagnosis, and primary treatment for acute abdomen was performed to develop the Practice Guidelines for Primary Care of Acute Abdomen 2015. Because many types of pathophysiological events underlie acute abdomen, these guidelines cover the primary care of adult patients with nontraumatic acute abdomen. A total of 108 questions based on nine subject areas were used to compile 113 recommendations. The subject areas included definition, epidemiology, history taking, physical examination, laboratory test, imaging studies, differential diagnosis, initial treatment, and education. Japanese medical circumstances were considered for grading the recommendations to assure useful information. The two-step methods for the initial management of acute abdomen were proposed. Early use of transfusion and analgesia, particularly intravenous acetaminophen, were recommended. The Practice Guidelines for Primary Care of Acute Abdomen 2015 have been prepared as the first evidence-based guidelines for the management of acute abdomen. We hope that these guidelines contribute to clinical practice and improve the primary care and prognosis of patients with acute abdomen.

Arteriovenous Blood Metabolomics: A Readout of Intra-Tissue Metabostasis

The human circulatory system consists of arterial blood that delivers nutrients to tissues, and venous blood that removes the metabolic by-products. Although it is well established that arterial blood generally has higher concentrations of glucose and oxygen relative to venous blood, a comprehensive biochemical characterization of arteriovenous differences has not yet been reported. Here we apply cutting-edge, mass spectrometry-based metabolomic technologies to provide a global characterization of metabolites that vary in concentration between the arterial and venous blood of human patients. Global profiling of paired arterial and venous plasma from 20 healthy individuals, followed up by targeted analysis made it possible to measure subtle (<2 fold), yet highly statistically significant and physiologically important differences in water soluble human plasma metabolome. While we detected changes in lactic acid, alanine, glutamine, and glutamate as expected from skeletal muscle activity, a number of unanticipated metabolites were also determined to be significantly altered including Krebs cycle intermediates, amino acids that have not been previously implicated in transport, and a few oxidized fatty acids. This study provides the most comprehensive assessment of metabolic changes in the blood during circulation to date and suggests that such profiling approach may offer new insights into organ homeostasis and organ specific pathology.

High serum lactate level may predict death within 24 hours

BACKGROUND

Unexpected death within 24 hours of admission is a real challenge for the clinician in the emergency room. How to diagnose these patients and the right approach to prevent sudden death with 24 hours is still an enigma. The aims of our study were to find the independent factors that may affect the clinical outcome in the first 24 hours of admission to the hospital.

METHODS

We performed a retrospective study defining unexpected death within 24 hours of admission in our Department of Medicine in the last 6 years. We found 43 patients who died within 24 hours of admission, and compared their clinical and biochemical characteristics to 6055 consecutive patients who were admitted in that period of time and did not die within the first 24 hours of admission. The parameters that were used include gender, age, temperature, clinical and laboratory criteria for SIRS, arterial blood lactate, and arterial blood pH.

RESULTS

Most of the patients who died within 24 hours had sepsis with SIRS. These patients were older (78.6±14.7 vs. 65.2±20.2 years [p<.0001]), had higher lactate levels (8.0±4.8 vs. 2.1±1.8mmol/L [p<.0001]), and lower pH (7.2±0.2 vs. 7.4±0.1 [p<.0001]). Logistic regression analysis found that lactate was the strongest independent parameter to predict death within 24 hours of admission (OR 1.366 [95% CI 1.235-1.512]), followed by old age (OR 1.048 [95% CI 1.048-1.075] and low arterial blood pH (OR 0.007 [CI <0.001-0.147]). When gender was analyzed, pH was not an independent variable in females (only in males).

CONCLUSIONS

The significant independent variable that predicted death within 24 hours of admission was arterial blood lactate level on admission. Older age was also an independent variable; low pH affected only males, but was a less dominant variable. We suggest use of arterial blood lactate level on admission as a bio-marker in patients with suspected sepsis admitted to the hospital for risk assessment and prediction of death within 24 hours of admission.

Use of femoral vein catheters for the assessment of perfusion parameters

The use of central venous oxygen saturation (SvcO₂) and arterial lactate in the diagnosis of severe tissue hypoperfusion is well established, and the optimization of these parameters is currently under investigation, particularly in patients with severe sepsis/septic shock. However, the only place for deep venous puncture or the first choice for puncture is often the femoral vein. Although venous saturation obtained from blood sampling from this catheter, instead of SvcO₂, has already been used in the diagnosis of severe tissue hypoperfusion, little is known about the accuracy of the results. The venous lactate in place of arterial puncture has also been used to guide therapeutic decisions. We conducted this literature review to seek evidence on the correlation and concordance of parameters obtained by collecting femoral venous blood gases in relation to SvcO₂ and arterial lactate. Few studies in the literature have evaluated the use of femoral venous oxygen saturation (SvfO₂) or venous lactate. The results obtained thus far demonstrate no adequate agreement between SvfO₂ and SvcO₂, which limits the clinical use of SvfO₂. However, the apparent strong correlation between arterial and peripheral and central venous lactate values suggests that venous lactate obtained from the femoral vein could eventually be used instead of arterial lactate, although there is insufficient evidence on which to base this procedure at this time.

Peripheral venous lactate at admission is associated with in-hospital mortality, a prospective cohort study

BACKGROUND

The prognostic value of blood lactate as a predictor of adverse outcome in the acutely ill patient is unclear. The aim of this study was to investigate if a peripheral venous lactate measurement, taken at admission, is associated with in-hospital mortality in acutely ill patients with all diagnosis. Furthermore, we wanted to investigate if the test improves a triage model in terms of predicting in-hospital mortality.

METHODS

We retrieved a cohort of 2272 adult patients from a prospectively gathered acute admission database. We performed regression analysis to evaluate the association between the relevant covariates and the outcome measure: in-hospital mortality.

RESULTS

Lactate as a continuous variable was a risk for in-hospital mortality with an odds ratio (OR) of 1.40 [95% confidence interval (CI) 1.25-1.57, P<0.0001]. OR for in-hospital mortality increased with increasing lactate levels from 2.97 (95% CI 1.55-5.72, P<0.001) for lactate between 2 mmol/l and 4 mmol/l, to 7.77 (95% CI 3.23-18.66, P<0.0001) for lactate>4 mmol/l. If the condition was non-compensated (i.e. pH<7.35), OR for in-hospital mortality increased to 19.99 (7.26-55.06, P<0.0001). Patient with a blood lactate at 4 mmol/l or more had a risk of in-hospital mortality equivalent to the patients in the most urgent triage category.

CONCLUSION

We found elevated admission peripheral venous lactate to be independently associated with in-hospital mortality in the acutely ill patient admitted to the emergency department. Patients with a lactate>4 mmol/l at hospital admission should be considered triaged to the most urgent triage category.

Preoperative and postoperative L-lactatemia assessment for the prognosis of right abomasal disorders in dairy cattle

BACKGROUND

Preoperative L-lactatemia and heart rate have been suggested as prognostic indicators of outcome for cows with right dilatation of the abomasum or volvulus (RDA/AV). However, postoperative L-lactatemia has not been assessed as a potential prognostic tool.

OBJECTIVES

To determine the prognostic value of postoperative L-lactatemia (LAC2 ), duration of treatment (Dt), relative L-lactatemia difference (compared with preoperative L-lactatemia [LAC1 ]) ([LAC2 - LAC1 ]/LAC2 ) and change in L-lactate over time ([LAC2 - LAC1 ]/Dt) as compared to preoperative findings (LAC1 and heart rate [HR]) as prognostic factors in dairy cows with RDA/AV.

ANIMALS

A total of 41 dairy cows were included: 19 with AV and 22 with RDA; 11 cows had a negative outcome (NO) and 30 cows had a positive outcome (PO) based on telephone follow-up with owners 30 days after surgery.

METHODS

Prospective cohort study. Analysis was performed using logistic regression and comparison of area under the receiver operating characteristics curve (AUC) using nonparametric tests.

RESULTS

LAC1 > 1.4 mmol/L or LAC2 > 2.2 mmol/L had the same accuracy with sensitivity of 100% (95% CI, 75.1-100%) and specificity of 80% (95% CI, 61.4-92.3%) for predicting NO. The relative L-lactatemia difference ([LAC2 - LAC1 ]/LAC1 ) or lactate kinetics ([LAC2 - LAC1 ]/Dt) were not associated with prognosis. The AUC of the preoperative model (which included HR and lnLAC1 ) was 0.92 (95% CI, 0.83-1.0) and that of the postoperative model (including only lnLAC2 ) was 0.95 (95% CI, 0.88-1.0); these were not significantly different.

CONCLUSIONS AND CLINICAL IMPORTANCE

Postoperative L-lactatemia is helpful to predict outcome in cows with RDA/AV. The short-term change in blood L-lactate is not a useful prognostic indicator, at least during the period of time spent on the farm for surgery and treatment.

Validating a pragmatic definition of shock in adult patients presenting to the ED

OBJECTIVE

The importance of the early recognition of shock in patients presenting to emergency departments is well recognized, but at present, there is no agreed practical definition for undifferentiated shock. The main aim of this study was to validate an a priori clinical definition of shock against 28-day mortality.

DESIGN, SETTING AND SUBJECTS

This prospective, observational, cross-sectional, single-center study was conducted in Hong Kong, China. Data were collected between July 1, 2012, and January 31, 2013. An a priori definition of shock was designed, whereby patients admitted to the resuscitation room or high dependency area of the emergency department were divided into 1 of 3 groups-no shock, possible shock, and shock. The primary outcome was 28-day mortality. Secondary outcomes were in-hospital mortality or admission to the intensive or coronary care unit.

MEASUREMENTS AND MAIN RESULTS

A total of 111 patients (mean age, 67.2 ± 17.1 years; male = 69 [62%]) were recruited, of which 22 were classified as no shock, 54 as possible shock, and 35 as shock. Systolic blood pressure, mean arterial pressure, lactate, and base deficit correlated well with shock classifications (P < .05). Patients who had 3 or more positively defined shock variables had a 100% poor composite outcome rate (5 of 5). Patients with 2 shock variables had a 66.7% (4 of 6) poor composite outcome rate.

CONCLUSIONS

A simple, practical definition of undifferentiated shock has been proposed and validated in a group of patients presenting to an emergency department in Hong Kong. This definition needs further validation in a larger population and other settings.

The role of immune and metabolic biomarkers for improved management of sepsis patients

Sepsis, the body`s overwhelming response to systemic infections, is responsible for significant morbidity, mortality, and financial burden. Pathogens and their antigens stimulate pro- and anti-inflammatory mediators and immune markers which characterize the host defense and orchestrate leukocyte recruitment to the acute site of infection. Different immune and metabolic biomarkers have been studied in relation to sepsis for their diagnostic and/or prognostic aid. Recent studies have provided abundant evidence that specific immune and metabolic biomarkers improve a physician`s ability to guide early sepsis recognition, severity assessment and therapeutic decisions in individual patients. This may allow for a transition from bundled sepsis care (protocols combining several medical practices) to more individualized management. First, lactate has now been widely used for risk stratification and guidance of fluid resuscitation. Second, procalcitonin correlates with risks of bacterial infections and helps guide therapeutic decisions about initiation and withdrawal of anti-microbial therapy. Third, prognostic markers such as pro-adrenomedullin improve early mortality prediction and thereby site-of-care decisions in respiratory infections. For these markers interventional trials have documented their value when integrated in clinical protocols.

Introducing intravascular microdialysis for continuous lactate monitoring in patients undergoing cardiac surgery: a prospective observational study

Introduction

Lactate is a marker of hypoperfusion and may be used for risk assessment in critically ill patients. Although evidence suggests that repeated lactate measurements are of clinical interest, how and when lactate should be analyzed is controversial. Intravascular microdialysis provides a novel method for the continuous monitoring of lactate, which may be clinically beneficial in critically ill patients.

Methods

Circulating lactate levels were continuously monitored in 80 patients undergoing cardiac surgery using either a separate single-lumen microdialysis catheter or a triple-lumen central venous catheter with an integrated microdialysis function. The catheter was placed with the tip positioned in the superior vena cava. Arterial blood gas samples were taken every hour to obtain reference values, and the lactate levels were analyzed in a blood gas analyzer.

Results

A total of 1,601 paired microdialysis–arterial blood gas lactate samples were obtained. Bland-Altman analysis showed a bias (mean difference) ± limits of agreement (±1.96 SD) of 0.02 ± 0.42 mmol/L. The regression coefficient was 0.98 (P = 0.0001).

Conclusions

Central venous microdialysis is an accurate and reliable method for continuous blood lactate monitoring in patients undergoing cardiac surgery. The system may be useful for early lactate-guided therapy in critically ill patients.

Can we predict arterial lactate from venous lactate in the ED?

OBJECTIVE

We aimed to generate equation to predict arterial lactate (a-Lac) using venous lactate (v-Lac) and other lab data.

METHODS

A prospective cross-sectional study was conducted on emergency patients in the emergency department for 6 months at a general hospital in Tokyo, Japan. We collected arterial and venous gas analysis data. Patients were eligible for entry into the study if an arterial blood gas analysis was required for appropriate diagnostic care by the treating physician. Univariate linear regression analysis was conducted to generate an equation to calculate a-Lac incorporating only v-Lac. A multivariate forward stepwise logistic regression model (p-value of 0.05 for entry, 0.1 for removal) was used to generate an equation including v-Lac and other potentially relevant variables. Bland-Altman plot was drawn and the two equations were compared for model fitting using R-squares.

RESULTS

Seventy-two arterial samples from 72 participants (61% male; mean age, 58.2 years) were included in the study. An initial regression equation was derived from univariate linear regression analysis:"(a-Lac) = -0.259 + (v-Lac) × 0.996". Subsequent multivariate forward stepwise logistic regression analysis, incorporating v-Lac and Po2, generated the following equation:"(a-Lac) = -0.469+(venous Po2) × 0.005 + (v-Lac) × 0.997". Calculated R-squares by single and multiple regression were 0.94 and 0.96, respectively.

CONCLUSION

v-Lac estimates showed a high correlation with arterial values and our data provide two clinically useful equations to calculate a-Lac from v-Lac data. Considering clinical flexibility, "Lac = -0.259 + v-Lac × 0.996" might be more useful while avoiding a time-consuming and invasive procedure.

Clinical use of lactate monitoring in critically ill patients

Increased blood lactate levels (hyperlactataemia) are common in critically ill patients. Although frequently used to diagnose inadequate tissue oxygenation, other processes not related to tissue oxygenation may increase lactate levels. Especially in critically ill patients, increased glycolysis may be an important cause of hyperlactataemia. Nevertheless, the presence of increased lactate levels has important implications for the morbidity and mortality of the hyperlactataemic patients. Although the term lactic acidosis is frequently used, a significant relationship between lactate and pH only exists at higher lactate levels. The term lactate associated acidosis is therefore more appropriate. Two recent studies have underscored the importance of monitoring lactate levels and adjust treatment to the change in lactate levels in early resuscitation. As lactate levels can be measured rapidly at the bedside from various sources, structured lactate measurements should be incorporated in resuscitation protocols.

Do sepsis biomarkers in the emergency room allow transition from bundled sepsis care to personalized patient care?

PURPOSE OF REVIEW

There is convincing evidence linking early start of fluid resuscitation and initiation of appropriate antimicrobial therapy to improved outcomes in patients with sepsis in the emergency department. Blood biomarkers measured on admission and during follow-up have the ability to guide early sepsis recognition, severity assessment and therapeutic decisions in individual patients and may allow transition from bundled sepsis care to more individualized management in single patients.

RECENT FINDINGS

Although a large number of promising diagnostic and prognostic biomarkers have been put forward in observational studies, only few have been evaluated in prospective randomized-controlled intervention trials. Markers such as lactate for risk stratification and guidance of fluid resuscitation, procalcitonin for assessing risk of bacterial infections and guiding therapeutic decisions about initiation and duration of antimicrobial therapy, and recently proadrenomedullin for early mortality prediction and site-of-care decisions in respiratory infections, have shown to improve patient management.

SUMMARY

For few biomarkers, recent study results demonstrate that well defined clinical protocols have the potential to guide decisions about the individual risk stratification and treatment of patients with suspicion of sepsis ultimately leading to improved patient care and outcomes. For other biomarkers, promising observation data have been put forward, but their potential needs to be evaluated in large-scale, well designed prospective intervention studies before clinical use can be recommended.

End-tidal carbon dioxide is associated with mortality and lactate in patients with suspected sepsis

OBJECTIVE

Exhaled end-tidal carbon dioxide (ETCO(2)) concentration is associated with lactate levels in febrile patients. We assessed the association of ETCO(2) with mortality and lactate levels in patients with suspected sepsis.

METHODS

This was a prospective observational study. We enrolled 201 adult patients presenting with suspected infection and 2 or more systemic inflammatory response syndrome criteria. Lactate and ETCO(2) were measured and analyzed with patient outcomes.

RESULTS

The area under the receiver operator characteristics curve (AUC) was 0.75 (confidence interval [CI], 0.65-0.86) for lactate and mortality and 0.73 (CI, 0.61-0.84) for ETCO(2) and mortality. When analyzed across the different categories of sepsis, the AUCs for lactate and mortality were 0.61 (CI, 0.36-0.87) for sepsis, 0.69 (CI, 0.48-0.89) for severe sepsis, and 0.74 (CI, 0.55-0.93) for septic shock. The AUCs for ETCO(2) and mortality were 0.60 (CI, 0.37-0.83) for sepsis, 0.67 (CI, 0.46-0.88) for severe sepsis, and 0.78 (CI, 0.59-0.96) for septic shock. There was a significant inverse relationship between ETCO(2) and lactate in all categories, with correlation coefficients of -0.421 (P < .001) in the sepsis group, -0.597 (P < .001) in the severe sepsis group, and -0.482 (P = .011), respectively. Adjusted odds ratios were calculated, demonstrating 3 significant predictors of mortality: use of vasopressors 16.4 (95% CI, 1.80-149.2), mechanical ventilation 16.4 (95% CI, 3.13-85.9), and abnormal ETCO(2) levels 6.48 (95% CI, 1.06-39.54).

CONCLUSIONS

We observed a significant association between ETCO(2) concentration and in-hospital mortality in emergency department patients with suspected sepsis across a range of disease severity.

Venous lactate levels can be used to identify patients with poor outcome following community-onset norovirus enteritis

BACKGROUND

Norovirus enteritis (NVE) can be fatal in frail patients. High blood lactate levels indicate hypoperfusion and predict mortality in many infectious diseases. The objective was to determine the frequency and association with mortality of elevated lactate levels in patients with community-onset NVE.

METHODS

A retrospective cohort study was performed. All hospitalized adult patients with community-onset NVE verified by polymerase chain reaction during the period August 2008 to June 2009 were included. Vital signs and venous lactate on arrival, co-morbid conditions, and time of death were registered. The outcome measure was 30-day all-cause mortality.

RESULTS

Eighty-two patients with a median age of 77 y (interquartile range (IQR) 53-86 y) were included, of whom 47 (57%) were female and 49 (60%) had at least 1 major co-morbid condition. Lactate levels were above the upper limit of normal (ULN; 1.6 mmol/l) in 45 patients (55%). The overall 30-day mortality rate was 7% (6/82). Mortality was 18% (5/28) with lactate ≥ 2.4 mmol/l (> 50% above the ULN) on admission compared to 2% (1/54) with lactate < 2.4 mmol/l (p < 0.05). Patients who died had a higher median lactate level compared to survivors: 4.5 (IQR 2.7-7.9) mmol/l vs 1.7 (IQR 1.3-2.5) mmol/l, respectively (p < 0.01). The adjusted odds ratio for death within 30 days for a 1 mmol/l increase in lactate was 2.5 (95% confidence interval 1.003-6.3, p = 0.049).

CONCLUSIONS

We observed a high proportion of patients with elevated lactate levels in community-onset NVE. Lactate elevation could predict mortality. Measurement of blood lactate may be a valuable tool in the clinical management of patients with a suspected norovirus infection.

Blood lactate as a predictor for in-hospital mortality in patients admitted acutely to hospital: a systematic review

BACKGROUND

Using blood lactate monitoring for risk assessment in the critically ill patient remains controversial. Some of the discrepancy is due to uncertainty regarding the appropriate reference interval, and whether to perform a single lactate measurement as a screening method at admission to the hospital, or serial lactate measurements. Furthermore there is no consensus whether the sample should be drawn from arterial, peripheral venous, or capillary blood. The aim of this review was: 1) To examine whether blood lactate levels are predictive for in-hospital mortality in patients in the acute setting, i.e. patients assessed pre-hospitally, in the trauma centre, emergency department, or intensive care unit. 2) To examine the agreement between arterial, peripheral venous, and capillary blood lactate levels in patients in the acute setting.

METHODS

We performed a systematic search using PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and CINAHL up to April 2011. 66 articles were considered potentially relevant and evaluated in full text, of these ultimately 33 articles were selected.

RESULTS AND CONCLUSION

The literature reviewed supported blood lactate monitoring as being useful for risk assessment in patients admitted acutely to hospital, and especially the trend, achieved by serial lactate sampling, is valuable in predicting in-hospital mortality. All patients with a lactate at admission above 2.5 mM should be closely monitored for signs of deterioration, but patients with even lower lactate levels should be considered for serial lactate monitoring. The correlation between lactate levels in arterial and venous blood was found to be acceptable, and venous sampling should therefore be encouraged, as the risk and inconvenience for this procedure is minimal for the patient. The relevance of lactate guided therapy has to be supported by more studies.

Early detection and treatment of severe sepsis in the emergency department: identifying barriers to implementation of a protocol-based approach

INTRODUCTION

Despite evidence to support efficacy of early goal-directed therapy for resuscitation of patients with severe sepsis and septic shock in the emergency department, implementation remains incomplete. To identify and address specific barriers at our institution and maximize benefits of a planned sepsis treatment initiative, a baseline assessment of knowledge, attitudes, and behaviors regarding detection and treatment of severe sepsis was performed.

METHODS

An online survey was offered to nurses and physicians in the emergency department of a major urban academic medical center. The questionnaire was designed to assess (1) baseline knowledge and self-reported confidence in identification of systemic inflammatory response syndrome and sepsis; (2) current practices in treatment; (3) difficulties encountered in managing sepsis cases; (4) perceived barriers to implementation of a clinical pathway based on early quantitative resuscitation goals; and (5) to elicit suggestions for improvement of sepsis treatment within the department.

RESULTS

Respondents (n = 101) identified barriers to a quantitative resuscitation protocol for sepsis. These barriers included the inability to perform central venous pressure/central venous oxygen saturation monitoring, limited physical space in the emergency department, and lack of sufficient nursing staff. Among nurses, the greatest perceived contributor to delays in treatment was a delay in diagnosis by physicians; among physicians, a delay in availability of ICU beds and nursing delays were the greatest barriers. Despite these issues, respondents indicated that a written protocol would be helpful to them.

DISCUSSION

Knowledge gaps and procedural hurdles identified by the survey will inform both educational and process components of an initiative to improve sepsis care in the emergency department.