Serum lactate as a predictor of mortality in patients with infection

Influenza A 2009 (H1N1) virus in admitted and critically ill patients

INTRODUCTION

The influenza A 2009 (H1N1) virus is a pandemic respiratory infection commanding international attention. More information is needed on patient demographics, illness severity, and risk indicators.

METHODS

A total of 43 patients with H1N1 influenza A 2009 presenting to 2 urban academic medical centers during the first wave were assessed for demographics, triage vital signs, hemograms, and serum chemistries including lactate. Chest X-rays were assessed for infiltrate or effusion. Illness severity markers were recorded including anion gap (AG), strong ion gap (SIG), systemic inflammatory response syndrome score, shock index, confusion, uremia, respiratory rate, blood pressure, and age >= 65 years (CURB-65) score, and pneumonia severity index. Subgroup analysis was performed on asthmatic, pregnant, and intensive care unit (ICU) versus non-ICU patients.

RESULTS

Eighty-one percent of patients were women. Pregnancy (34.8%), asthma (39.5%), diabetes mellitus (18.6%), and sickle cell (6.98%) were the most frequent comorbidities. In all, 91% had positive influenza nasopharyngeal direct antigen test, while 9% tested positive only by viral culture or real-time reverse transcriptase polymerase chain reaction (rRT-PCR); 14% required ICU admission; and 20.8% had infiltrate on chest X-ray. A trend toward greater incidence of ICU admission existed among patients with elevated SIG (P = .08), however contrary to our prior studies in noninfluenza patients, an elevated SIG in the presence of normal AG and lactate measurements did not correlate with ICU admission.

CONCLUSION

A high percentage of patients with H1N1 presented with underlying comorbid conditions including asthma and pregnancy. Traditional markers of pneumonia severity including CURB-65 score, Pneumonia Severity Index (PSI), serum lactate, and AG did not correlate with ICU admission in patients with H1N1. Strong ion gap effectively identified significant acid-base disturbances not identified by lactate or AG, however the trend of greater ICU admission rates among patients with elevated SIG did not reach statistical significance. Further study is needed to identify clinical tools to aid in risk-stratifying H1N1 patients.

Base excess is an accurate predictor of elevated lactate in ED septic patients

BACKGROUND

Prior studies showed that lactate is a useful marker in sepsis. However, lactate is often not routinely drawn or rapidly available in the emergency department (ED).

OBJECTIVE

The study aimed to determine if base excess (BE), widely and rapidly available in the ED, could be used as a surrogate marker for elevated lactate in ED septic patients.

METHODS

This was a prospective and observational cohort study. From March 2009 to March 2010, consecutive patients 18 years or older who presented to the ED with a suspected severe sepsis were enrolled in the study. Lactate and BE measurements were performed. We defined, a priori, a clinically significant lactate to be greater than 3 mmol/L and BE less than -4 mmol/L.

RESULTS

A total of 224 patients were enrolled in the study. The average BE was -4.5 mmol/L (SD, 4.9) and the average lactate was 3.5 mmol/L (SD, 2.9). The sensitivity of a BE less than -4 mmol/L in predicting elevated lactate greater than 3 mmol/L was 91.1% (95% confidence interval, 85.5%-96.6%) and the specificity was 88.6% (95% confidence interval, 83.0%-94.2%). The area under the curve was 0.95.

CONCLUSION

Base excess is an accurate marker for the prediction of elevated lactate in the ED. The measurement of BE, obtained in a few minutes in the ED, provides a secure and quick method, similar to the electrocardiogram at triage for patients with chest pain, to determine the patients with sepsis who need an early aggressive resuscitation.

A Computerized Alert Screening for Severe Sepsis in Emergency Department Patients Increases Lactate Testing but does not Improve Inpatient Mortality

OBJECTIVE

This study tested the hypothesis that lactate testing in ED sepsis patients could be increased using a computer alert that automatically recognizes systemic inflammatory response syndrome (SIRS) criteria and recommends lactate testing in cases of sepsis defined as ≥2 SIRS criteria plus physician suspicion of infection. Secondary outcomes included the effect of the alert on lactate testing among admitted sepsis patients, the proportion of admitted patients with lactate ≥4.0 mmol/L identified and the in-patient mortality difference before and after alert implementation.

METHODS

After a 6 month pre-alert phase, a computer alert was implemented that computed and displayed abnormal vital signs and white blood cell counts for all patients with >2 SIRS criteria and recommended testing lactate if an infection was suspected. Data for admitted patients was collected electronically on consecutive patients meeting sepsis criteria for 6 months before and 6 months after implementation of the alert.

RESULTS

There were a total of 5,796 subjects enrolled. Among all septic patients, lactate testing increased from 5.2% in the pre-alert phase to 12.7% in the alert phase, a 7.5% (95% CI 6.0 to 9.0%) absolute increase in lactate testing, p<0.001. Among the 1,798 admitted patients with sepsis, lactate testing increased from 15.3% to 34.2%, an 18.9% (95% CI 15.0 to 22.8%) absolute increase, p<0.001. Among admitted patients with sepsis, there was a 1.9% (95% CI 0.03 to 3.8%, p = 0.05) increase in absolute number of patients with elevated lactate levels identified and a 0.5% (95% CI -1.6 to 2.6%, p=0.64) decrease in mortality.

CONCLUSION

The proportion of ED patients who had lactate tested and the number of admitted patients identified with a lactate level ≥4.0 mmol/L improved significantly after the implementation of a computer alert identifying sepsis patients with >2 SIRS criteria while mortality among admitted sepsis patients remained unchanged.

Lactic acidosis: recognition, kinetics, and associated prognosis

Lactic acidosis is a common condition encountered by critical care providers. Elevated lactate and decreased lactate clearance are important for prognostication. Not all lactate in the intensive care unit is due to tissue hypoxia or ischemia and other sources should be evaluated. Lactate, in and of itself, is unlikely to be harmful and is a preferred fuel for many cells. Treatment of lactic acidosis continues to be aimed the underlying source.

The role of serum lactate in the acute care setting

Acute care services are increasingly faced with the double burden of high patient acuity and limited resources. Early identification of patients who are sick or who have the potential to deteriorate rapidly is crucial so that these resources may be allocated to those in greatest need. Traditional measures of illness and end points of resuscitation, such as vital signs, often fail to identify occult hypoperfusion with certain disease processes associated with high morbidity and mortality. Thus, biochemical markers that may predict illness earlier are becoming more relevant. We present a review of the evidence behind use of the serum lactate level in this setting.

Decompressive laparotomy for abdominal compartment syndrome in children: before it is too late

PURPOSE

Abdominal compartment syndrome (ACS) in children is an infrequently reported, rapidly progressive, and often lethal condition underappreciated in the pediatric population. This underrecognition can result in a critical delay in diagnosis causing increased morbidity and mortality. This study examines the clinical course of patients treated for ACS at our institution.

METHODS

A review of children requiring an emergency laparotomy (n = 264) identified 26 patients with a diagnosis of ACS. ACS was defined as sustained intraabdominal hypertension (bladder pressure >12 mm Hg) that was associated with new onset organ dysfunction or failure.

RESULTS

Patients ranged in age from 3 months to 17 years old and were cared for in the pediatric intensive care unit (PICU). Twenty-seven percent (n = 7) were transferred from referring hospitals, 50% (n = 13) were admitted directly from the emergency department, and 23% (n = 6) were inpatients before being transferred to PICU. Admission diagnoses included infectious enterocolitis (n = 12), postsurgical procedure (n = 10), and others (n = 4). Patients progressed to ACS rapidly, with most requiring decompressive laparotomy within 8 hours of PICU admission (range, <1-96 hours). Preoperatively, all patients had maximum ventilatory support and oliguria, 85% (n = 22) required vasopressors/inotropes, and 31% (n = 8) required hemodialysis. Mean bladder pressure was 25 mm Hg (range, 12-44 mm Hg). In 42% (n = 11), cardiac arrest preceeded decompressive laparotomy. All patients showed evidence of tissue ischemia before decompressive laparotomy with an average preoperative lactate of 8 (range, 1.2-20). Decompressive laparotomy was done at the bedside in the PICU in 13 patients and in the operating room in 14 patients. Abdominal wounds were managed with open vacuum pack or silastic silo dressings. Physiologic data including fluid resuscitation, oxygen index, mean airway pressure, vasopressor score, and urine output were recorded at 6-hour intervals beginning 12 hours before decompressive laparotomy and extending 12 hours after operation. The data demonstrate improvement of all physiologic parameters after decompressive laparotomy except for urine output, which continued to be minimal 12 hours post intervention. Mortality was 58% (n = 15) overall. The only significant factor related to increased mortality was bladder pressure (P = .046; odds ratio, 1.258). Cardiac arrest before decompressive laparotomy, need for hemodialysis, and transfer from referring hospital also trended toward increased mortality but did not reach significance.

CONCLUSION

Abdominal compartment syndrome in children carries a high mortality and may be a consequence of common childhood diseases such as enterocolitis. The diagnosis of ACS and the potential need for emergent decompressive laparotomy may be infrequently discussed in the pediatric literature. Increased awareness of ACS may promote earlier diagnosis, treatment, and possibly improve outcomes.

Disease progression in hemodynamically stable patients presenting to the emergency department with sepsis

BACKGROUND

Aggressive diagnosis and treatment of patients presenting to the emergency department (ED) with septic shock has been shown to reduce mortality. To enhance the ability to intervene in patients with lesser illness severity, a better understanding of the natural history of the early progression from simple infection to more severe illness is needed.

OBJECTIVES

The objectives were to 1) describe the clinical presentation of ED sepsis, including types of infection and causative microorganisms, and 2) determine the incidence, patient characteristics, and mortality associated with early progression to septic shock among ED patients with infection.

METHODS

This was a multicenter study of adult ED patients with sepsis but no evidence of shock. Multivariable logistic regression was used to identify patient factors for early progression to shock and its association with 30-day mortality.

RESULTS

Of 472 patients not in shock at ED presentation (systolic blood pressure > 90 mm Hg and lactate < 4 mmol/L), 84 (17.8%) progressed to shock within 72 hours. Independent factors associated with early progression to shock included older age, female sex, hyperthermia, anemia, comorbid lung disease, and vascular access device infection. Early progression to shock (vs. no progression) was associated with higher 30-day mortality (13.1% vs. 3.1%, odds ratio [OR] = 4.72, 95% confidence interval [CI] = 2.01 to 11.1; p < or = 0.001). Among 379 patients with uncomplicated sepsis (i.e., no evidence of shock or any end-organ dysfunction), 86 (22.7%) progressed to severe sepsis or shock within 72 hours of hospital admission.

CONCLUSIONS

A significant portion of ED patients with less severe sepsis progress to severe sepsis or shock within 72 hours. Additional diagnostic approaches are needed to risk stratify and more effectively treat ED patients with sepsis.

Treatment of lactic acidosis: appropriate confusion

BACKGROUND

Lactic acidosis (LA) is common in hospitalized patients and is associated with poor clinical outcomes. There have been major recent advances in our understanding of lactate generation and physiology. However, treatment of LA is an area of controversy and uncertainty, and the use of agents to raise pH is not clearly beneficial.

AIM AND METHODS

We reviewed animal and human studies on the pathogenesis, impact, and treatment of LA, published in the English language and available through the PubMed/MEDLINE database. Our aim was to clarify the physiology of the generation of LA, its impact on outcomes, and the different treatment modalities available. We also examined relevant data regarding LA induced by medications commonly prescribed by hospitalists: biguanides, nucleoside analog reverse-transcriptase inhibitors (NRTIs), linezolid, and lorazepam.

RESULTS/CONCLUSIONS

Lactic acid is a marker of tissue ischemia but it also may accumulate without tissue hypoperfusion. In the latter circumstance, lactic acid accumulation may be an adaptive mechanism-a novel possibility quite in contrast to the traditional view of lactic acid as only a marker of tissue ischemia. Studies on the treatment of LA with sodium bicarbonate or other buffers fail to show consistent clinical benefit. Severe acidemia in the setting of LA is a particularly poorly studied area. In the settings of medication-induced LA, optimal treatment, apart from prompt cessation of the offending agent, is still unclear.

Hemodynamic monitoring in sepsis

Tissue hypoperfusion is an important factor in the development of multiple organ failure. Therefore, recognition of sepsis-induced tissue hypoperfusion and timely clinical intervention to prevent and correct this are fundamental aspects of managing patients with sepsis and septic shock. Hemodynamic monitoring plays a key role in the management of the critically ill and is used to identify hemodynamic instability and its cause and to monitor response to therapy. However, the utility of many forms of hemodynamic monitoring that are used in management of sepsis and septic shock remain controversial and unproven. This article examines emerging technologies as well as more established techniques used to monitor hemodynamics in sepsis and assesses their potential roles in optimization of sepsis-induced tissue hypoperfusion.

Blood lactate monitoring in critically ill patients: a systematic health technology assessment

OBJECTIVE

To decide whether the use of blood lactate monitoring in critical care practice is appropriate. We performed a systematic health technology assessment as blood lactate monitoring has been implemented widely but its clinical value in critically ill patients has never been evaluated properly.

DATA SOURCE

PubMed, other databases, and citation review.

STUDY SELECTION

We searched for lactate combined with critically ill patients as the target patient population. Two reviewers independently selected studies based on relevance for the following questions: Does lactate measurement: 1) perform well in a laboratory setting? 2) provide information in a number of clinical situations? 3) relate to metabolic acidosis? 4) increase workers' confidence? 5) alter therapeutic decisions? 6) result in benefit to patients? 7) result in similar benefits in your own setting? 8) result in benefits which are worth the extra costs?

DATA EXTRACTION AND SYNTHESIS

We concluded that blood lactate measurement in critically ill patients: 1) is accurate in terms of measurement technique but adequate understanding of the (an)aerobic etiology is required for its correct interpretation; 2) provides not only diagnostic but also important prognostic information; 3) should be measured directly instead of estimated from other acid-base variables; 4) has an unknown effect on healthcare workers' confidence; 5) can alter therapeutic decisions; 6) could potentially improve patient outcome when combined with a treatment algorithm to optimize oxygen delivery, but this has only been shown indirectly; 7) is likely to have similar benefits in critical care settings worldwide; and 8) has an unknown cost-effectiveness.

CONCLUSIONS

The use of blood lactate monitoring has a place in risk-stratification in critically ill patients, but it is unknown whether the routine use of lactate as a resuscitation end point improves outcome. This warrants randomized controlled studies on the efficacy of lactate-directed therapy.

Potential dysregulation of the pyruvate dehydrogenase complex by bacterial toxins and insulin

BACKGROUND

The pyruvate dehydrogenase complex (PDC) catalyzes the conversion of pyruvate to acetyl CoA, effectively controlling the entrance of glycolysis products into aerobic metabolism. Because hyperlactatemia is one of the hallmarks of sepsis, we hyphothesized that gram-positive and negative bacterial toxin treatment will interfere with mRNA levels of regulatory enzymes of the PDC and overall enzyme activity in hepatocytes.

METHODS

HEP G2 hepatocarcinoma cells were incubated for 24 hours in the presence of lipopolysaccaride (LPS) or lipoteichoic acid. Total RNA was then isolated and message RNA levels for both pyruvate dehydrogense kinase 4 and phosphatase 2 were determined by RTPCR. Amplified DNA fragments were visualized by ethidium bromide in agarose gels and densitometry of the bands was performed. Data were then normalized to the housekeeping gene, GAPDH. Enzyme activity was then determined by capturing intact PDC on nitrocellulose membranes then determining PDC-dependent production of NADH.

RESULTS

LPS treatment led to a time dependent increase in PDK4 message while decreasing PDP2 levels. Enzyme activity, in these cells, also significantly decreased 24 hours after exposure to LPS. Cells cultured in the presence of lipoteichoic acid and insulin exhibited differing message ratios and activity levels when evaluated at 4 hours, but at 24 hours shifted to mimic those observed in LPS treated cells.

CONCLUSION

This data may indicate that exposure to bacterial cell wall components and insulin could create cellular environments that result in a build-up of lactate.

Surviving sepsis in low-income and middle-income countries: new directions for care and research

Sepsis is a disorder characterised by systemic inflammation secondary to infection. Despite recent progress in the understanding and treatment of sepsis, no data or recommendations exist that detail effective approaches to sepsis care in resource-limited low-income and middle-income countries (LMICs). Although few data exist on the burden of sepsis in LMICs, the prevalence of HIV and other comorbid conditions in some LMICs suggest that sepsis is a substantial contributor to mortality in these regions. In well-resourced countries, sepsis management relies on protocols and complex invasive technologies not widely available in most LMICs. However, the key concepts and components of sepsis management are potentially translatable to resource-limited environments. Health personnel in LMICs should be educated in the recognition of sepsis and the importance of early and appropriate antibiotic use. Simple and low-cost standardised laboratory testing should be emphasised to allow accurate diagnosis, prognosis, and monitoring of treatment response. Evidence-based interventions and treatment algorithms tailored to LMIC ecology and resources should thus be developed and validated.

The feasibility and accuracy of point-of-care lactate measurement in emergency department patients with suspected infection

BACKGROUND

Prior studies show that lactate is a useful prognostic marker in sepsis.

OBJECTIVE

To study the feasibility and accuracy of a point-of-care (POC) analyzer capable of performing bedside serum lactate measurements; and to determine if other measurements (pH, base excess) are predictive of mortality.

METHODS

DESIGN

prospective cohort study of adult (age 18 years or older) Emergency Department (ED) patients with suspected infection during the study period of May 2006 through March 2007.

SETTING

A 55,000-annual-visit urban tertiary care ED.

INTERVENTION

A point-of-care device (i-STAT, Abbott Point of Care Inc., Princeton, NJ) was deployed using a standardized training and quality assurance process. Using POC testing, we measured serum lactate, pH, and base excess, as well as concomitant lactate measurement via a central laboratory.

STATISTICS

Area under the curve (AUC) for receiver operator characteristic curve, Bland-Altman statistics along with a correlation coefficient, and relative risk with 95% confidence intervals reported.

RESULTS

There were 699 patients enrolled, of whom 34 (4.9%) died. The AUCs for mortality prediction were: POC lactate 0.72, laboratory lactate 0.70, pH measurement 0.60, and base excess 0.60. Bland-Altman showed that POC lactate was, on average, 0.32 (95% confidence interval -0.35-0.98) lower than laboratory lactate, with agreement kappa = 0.97.

CONCLUSIONS

A point-of-care testing device provides a reliable and feasible way to measure serum lactate at the bedside. The pH and base excess were less helpful.

Management of sepsis: early resuscitation

Key links in the chain of survival for the management of severe sepsis and septic shock are early identification and comprehensive resuscitation of high-risk patients. Multiple studies have shown that the first 6 hours of early sepsis management are especially important from a diagnostic, pathogenic, and therapeutic perspective, and that steps taken during this period can have a significant impact on outcome. The recognition of this critical time period and the robust outcome benefit realized in previous studies provides the rationale for adopting early resuscitation as a distinct intervention. Sepsis joins trauma, stroke, and acute myocardial infarction in having "golden hours," representing a critical opportunity early on in the course of disease for actions that offer the most benefit.

Mesenteric microcirculatory dysfunctions and translocation of indigenous bacteria in a rat model of strangulated small bowel obstruction

PURPOSE

Bacterial translocation has been shown to occur in critically ill patients after extensive trauma, shock, sepsis, or thermal injury. The present study investigates mesenteric microcirculatory dysfunctions, the bacterial translocation phenomenon, and hemodynamic/metabolic disturbances in a rat model of intestinal obstruction and ischemia.

METHODS

Anesthetized (pentobarbital 50 mg/kg, i.p.) male Wistar rats (250-350 g) were submitted to intestinal obstruction or laparotomy without intestinal obstruction (Sham) and were evaluated 24 hours later. Bacterial translocation was assessed by bacterial culture of the mesenteric lymph nodes (MLN), liver, spleen, and blood. Leukocyte-endothelial interactions in the mesenteric microcirculation were assessed by intravital microscopy, and P-selectin and intercellular adhesion molecule (ICAM)-1 expressions were quantified by immunohistochemistry. Hematocrit, blood gases, lactate, glucose, white blood cells, serum urea, creatinine, bilirubin, and hepatic enzymes were measured.

RESULTS

About 86% of intestinal obstruction rats presented positive cultures for E. coli in samples of the mesenteric lymph nodes, liver, and spleen, and 57% had positive hemocultures. In comparison to the Sham rats, intestinal obstruction induced neutrophilia and increased the number of rolling (approximately 2-fold), adherent (approximately 5-fold), and migrated leukocytes (approximately 11-fold); this increase was accompanied by an increased expression of P-selectin (approximately 2-fold) and intercellular adhesion molecule-1 (approximately 2-fold) in the mesenteric microcirculation. Intestinal obstruction rats exhibited decreased PaCO2, alkalosis, hyperlactatemia, and hyperglycemia, and increased blood potassium, hepatic enzyme activity, serum urea, creatinine, and bilirubin. A high mortality rate was observed after intestinal obstruction (83% at 72 h vs. 0% in Sham rats).

CONCLUSION

Intestinal obstruction and ischemia in rats is a relevant model for the in vivo study of mesenteric microcirculatory dysfunction and the occurrence of bacterial translocation. This model parallels the events implicated in multiple organ dysfunction (MOD) and death.

Improving outcomes for severe sepsis and septic shock: tools for early identification of at-risk patients and treatment protocol implementation

Sepsis is a significant problem, and septicemia is the 10th leading cause of death in the United States. Sepsis incidence is increasing, and the mortality rate is 20% to 50% for patients with severe sepsis. This article identifies methods for improving outcomes of severe sepsis and septic shock. Included are recommendations for diagnosis and treatment. Case studies are included.

Validation of the Fournier's gangrene severity index in a large contemporary series

PURPOSE

In this study we identified prognostic factors for survival and validated the accuracy of the Fournier's gangrene severity index in patients with Fournier's gangrene.

MATERIALS AND METHODS

We retrospectively reviewed medical records of patients diagnosed with Fournier's gangrene between 1996 and 2006. Fournier's gangrene severity index scores were assessed using a receiver operating characteristic curve. Using an outcome variable of inpatient mortality, univariate analyses were performed using the Mann-Whitney U, chi-square and Fisher exact tests.

RESULTS

A total of 68 patients (79.4% male, mean age 55.8 +/- 15.2 years) diagnosed with Fournier's gangrene met the criteria for review. The inpatient mortality rate was 10% (7 patients). The mean Fournier's gangrene severity index score for survivors was 5.4 +/- 3.5 vs 10.9 +/- 4.7 for nonsurvivors (p = 0.006). Isolated Fournier's gangrene severity index and individual laboratory parameters associated with mortality included heart rate (p = 0.05), respiratory rate (p = 0.02), serum creatinine (p = 0.03), serum bicarbonate (p = 0.001), serum lactate (p = 0.001) and serum calcium (p = 0.03). Although mean total body surface area was only suggestive of an association (p = 0.169), abdominal wall (p = 0.004) or lower extremity (p = 0.005) involvement was associated with increased mortality. Using a Fournier's gangrene severity index score threshold of 9 (sensitivity 71.4%, specificity 90%) there was a 96% survival rate in patients with a Fournier's gangrene severity index of less than 9 and a 46% mortality rate in those with a Fournier's gangrene severity index of 9 or greater (p = 0.001, OR 22, 95% CI 3.5-139.7).

CONCLUSIONS

The Fournier's gangrene severity index remains an objective and simple method to quantify the extent of metabolic aberration at presentation in patients with Fournier's gangrene. A Fournier's gangrene severity index threshold value of 9 is sensitive and specific for predicting mortality in this patient population.

Diagnosis and treatment of severe sepsis

The burden of infection in industrialized countries has prompted considerable effort to improve the outcomes of patients with sepsis. This has been formalized through the Surviving Sepsis Campaign 'bundles', derived from the recommendations of 11 professional societies, which have promoted global improvement in those practices whose primary goal it is to reduce sepsis-related death. However, difficulties remain in implementing all of the procedures recommended by the experts, despite the apparent pragmatism of those procedures. We summarize the main proposals made by the Surviving Sepsis Campaign and focus on the difficulties associated with making a proper diagnosis and supplying adequate treatment promptly to septic patients.