Lactic acidosis: recognition, kinetics, and associated prognosis

Lactate/Hydroxycarboxylic Acid Receptor 1 in Alzheimer's Disease: Mechanisms and Therapeutic Implications-Exercise Perspective

Lactate has a novel function different from previously known functions despite its traditional association with hypoxia in skeletal muscle. It plays various direct and indirect physiological functions. It is a vital energy source within the central nervous system (CNS) and a signal transmitter regulating crucial processes, such as angiogenesis and inflammation. Activating lactate and its associated receptors elicits effects like synaptic plasticity and angiogenesis alterations. These effects can significantly influence the astrocyte-neuron lactate shuttle, potentially impacting cognitive performance. Decreased cognitive function relates to different neurodegenerative conditions, including Alzheimer's disease (AD), ischemic brain injury, and frontotemporal dementia. Therefore, lactic acid has significant potential for treating neurodegenerative disorders. Exercise is a method that induces the production of lactic acid, which is similar to the effect of lactate injections. It is a harmless and natural way to achieve comparable results. Animal experiments demonstrate that high-intensity intermittent exercise can increase vascular endothelial growth factor (VEGF) levels, thus promoting angiogenesis. In vivo, lactate receptor-hydroxycarboxylic acid receptor 1 (HCAR1) activation can occur by various stimuli, including variations in ion concentrations, cyclic adenosine monophosphate (cAMP) level elevations, and fluctuations in the availability of energy substrates. While several articles have been published on the benefits of physical activity on developing Alzheimer's disease in the CNS, could lactic acid act as a bridge? Understanding how HCAR1 responds to these signals and initiates associated pathways remains incomplete. This review comprehensively analyzes lactate-induced signaling pathways, investigating their influence on neuroinflammation, neurodegeneration, and cognitive decline. Consequently, this study describes the unique role of lactate in the progression of Alzheimer's disease.

Arterial Blood Gases and Acid-Base Regulation

Disorders of acid-base status are common in the critically ill and prompt recognition is central to clinical decision making. The bicarbonate/carbon dioxide buffer system plays a pivotal role in maintaining acid-base homeostasis, and measurements of pH, PCO2, and HCO3 - are routinely used in the estimation of metabolic and respiratory disturbance severity. Hypoventilation and hyperventilation cause primary respiratory acidosis and primary respiratory alkalosis, respectively. Metabolic acidosis and metabolic alkalosis have numerous origins, that include alterations in acid or base intake, body fluid losses, abnormalities of intermediary metabolism, and renal, hepatic, and gastrointestinal dysfunction. The concept of the anion gap is used to categorize metabolic acidoses, and urine chloride excretion helps define metabolic alkaloses. Both the lungs and kidneys employ compensatory mechanisms to minimize changes in pH caused by various physiologic and disease disturbances. Treatment of acid-base disorders should focus primarily on correcting the underlying cause and the hemodynamic and electrolyte derangements that ensue. Specific therapies under certain conditions include renal replacement therapy, mechanical ventilation, respiratory stimulants or depressants, and inhibition of specific enzymes in intermediary metabolism disorders.

Lactate modulates iron metabolism by binding soluble adenylyl cyclase

Overproduction of lactate (LA) can occur during exercise and in many diseases such as cancers. Individuals with hyperlactatemia often display anemia, decreased serum iron, and elevated hepcidin, a key regulator of iron metabolism. However, it is unknown whether and how LA regulates hepcidin expression. Here, we show LA binds to soluble adenylyl cyclase (sAC) in normal hepatocytes and affects systemic iron homeostasis in mice by increasing hepcidin expression. Comprehensive in vitro, in vivo, and in silico experiments show that the LA-sAC interaction raises cyclic adenosine monophosphate (cAMP) levels, which activates the PKA-Smad1/5/8 signaling pathway to increase hepcidin transcription. We verified this regulatory axis in wild-type mice and in mice with disordered iron homeostasis. LA also regulates hepcidin in humans at rest and subjected to extensive exercise that produce elevated LA. Our study links hyperlactatemia to iron deficiency, offering a mechanistic explanation for anemias seen in athletes and patients with lactic acidosis.

Lactate Clearance as an Early Prognostic Marker of Mortality for Pediatric Trauma

Background While lactate clearance (LC) has already been shown as a prognostic indicator in clinical studies, its certain character needs to be defined in pediatric trauma. This research aimed to evaluate the correlation between early lactate clearance and mortality in pediatric trauma.Patients and methods A retrospective cohort study was conducted in a university hospital. Repeated LC was measured at admission, at the 2nd, 6th, and 12th hours post-admission. The association of lactate clearance with mortality was analyzed and using receiver operating characteristic (ROC) to determine the threshold levels of lactate clearance and also logistic regression analysis was performed to determine whether LC was an independent risk factor.Results Seventy-eight patients were included and overall mortality was 13%. LC values of the non-survivors was significantly lower than survivors for LC0-2 h (28.60±14.26 vs 4.64±15.90), LC0-6 h (46.63±15.23 vs 3.33±18.07), LC0-12 h (56.97±15.53 vs 4.82±22.59) (p:<0.001, p:<0.001 and p:<0.001, respectively). Areas under the curve of lactate clearance at the 2nd, 6th, and 12th hours after therapy start were a significant predictor for mortality (p:<0.001, p:<0.001, and p:<0.001, respectively). Threshold values of LC were 12.9, 19.5 and 29.3%, respectively.Conclusion Lactate clearance was a beneficial tool to estimate outcomes of pediatric trauma. Poor lactate clearance was a significant marker for poor prognosis.

Critical Care of the Colic Patient: Monitoring, Fluid Therapy, and More

A successful outcome to management of the critical colic patient is highly dependent on how the patient is monitored and treated, particularly, in the perioperative period. In this article, we will provide an update on monitoring techniques, advances in fluid therapy, nutrition management and pharmacotherapeutic agents, inclusive of pain monitoring and management, prokinetics, and management of systemic inflammatory response syndrome and the hypercoagulable state.

Lactate: a pearl dropped in the ocean-an overlooked signal molecule in physiology and pathology

Lactate, once recognized as a wasty product from anaerobic glycolysis, is proved to be a pivotal signal molecule. Lactate accumulation occurs in diverse physiological and pathological settings due to the imbalance between lactate production and clearance. Under the condition with drastic changes in local microenvironment, such as tumorigenesis, inflammation, and microbial infection, the glycolysis turns to be active in surrounding cells leading to increased lactate release. Meanwhile, lactate can be utilized by these cells as an energy substrate and acts as a signal molecule to regulate cell functions through receptor-dependent or independent pathways. In this review, we tended to tease out the contribution of lactate in tumor progression and immunomodulation. And we also discussed the accessory role of lactate, beyond as the energy source only, in the growth of invading pathogens.

Lactate levels as a prognostic predict in cardiogenic shock under venoarterial extracorporeal membrane oxygenation support

INTRODUCTION AND OBJECTIVES

Lactate and its evolution are associated with the prognosis of patients in shock, although there is little evidence in those assisted with an extracorporeal venoarterial oxygenation membrane (VA-ECMO). Our objective was to evaluate its prognostic value in cardiogenic shock assisted with VA-ECMO.

METHODS

Study of patients with cardiogenic shock treated with VA-ECMO for medical indication between July 2013 and April 2021. Lactate clearance was calculated: [(initial lactate - 6 h lactate) / initial lactate × exact time between both determinations].

RESULTS

From 121 patients, 44 had acute myocardial infarction (36.4%), 42 implant during cardiopulmonary resuscitation (34.7%), 14 pulmonary embolism (11.6%), 14 arrhythmic storm (11.6%), and 6 fulminant myocarditis (5.0%). After 30 days, 60 patients (49.6%) died, mortality was higher for implant during cardiopulmonary resuscitation than for implant in spontaneous circulation (30 of 42 [71.4%] vs 30 of 79 [38.0%], P=.030). Preimplantation GPT and lactate (both baseline, at 6hours, and clearance) were independently associated with 30-day mortality. The regression models that included lactate clearance had a better predictive capacity for survival than the ENCOURAGE and ECMO-ACCEPTS scores, with the area under the ROC curve being greater in the model with lactate at 6 h.

CONCLUSIONS

Lactate (at baseline, 6h, and clearance) is an independent predictor of prognosis in patients in cardiogenic shock supported by VA-ECMO, allowing better risk stratification and predictive capacity.

The more you give, the worse it gets

Persistent tachypnoea despite resolution of bronchospasm in a patient with acute asthma exacerbation after administration of inhaled short acting β₂-receptor agonist should alert the clinician to this potential diagnosis. https://bit.ly/385VU2Q.

Machine Learning Consensus Clustering Approach for Patients with Lactic Acidosis in Intensive Care Units

BACKGROUND

Lactic acidosis is a heterogeneous condition with multiple underlying causes and associated outcomes. The use of multi-dimensional patient data to subtype lactic acidosis can personalize patient care. Machine learning consensus clustering may identify lactic acidosis subgroups with unique clinical profiles and outcomes.

METHODS

We used the Medical Information Mart for Intensive Care III database to abstract electronic medical record data from patients admitted to intensive care units (ICU) in a tertiary care hospital in the United States. We included patients who developed lactic acidosis (defined as serum lactate ≥ 4 mmol/L) within 48 h of ICU admission. We performed consensus clustering analysis based on patient characteristics, comorbidities, vital signs, organ supports, and laboratory data to identify clinically distinct lactic acidosis subgroups. We calculated standardized mean differences to show key subgroup features. We compared outcomes among subgroups.

RESULTS

We identified 1919 patients with lactic acidosis. The algorithm revealed three best unique lactic acidosis subgroups based on patient variables. Cluster 1 (n = 554) was characterized by old age, elective admission to cardiac surgery ICU, vasopressor use, mechanical ventilation use, and higher pH and serum bicarbonate. Cluster 2 (n = 815) was characterized by young age, admission to trauma/surgical ICU with higher blood pressure, lower comorbidity burden, lower severity index, and less vasopressor use. Cluster 3 (n = 550) was characterized by admission to medical ICU, history of liver disease and coagulopathy, acute kidney injury, lower blood pressure, higher comorbidity burden, higher severity index, higher serum lactate, and lower pH and serum bicarbonate. Cluster 3 had the worst outcomes, while cluster 1 had the most favorable outcomes in terms of persistent lactic acidosis and mortality.

CONCLUSIONS

Consensus clustering analysis synthesized the pattern of clinical and laboratory data to reveal clinically distinct lactic acidosis subgroups with different outcomes.

Machine Learning Prediction Models for Mortality in Intensive Care Unit Patients with Lactic Acidosis

Background: Lactic acidosis is the most common cause of anion gap metabolic acidosis in the intensive care unit (ICU), associated with poor outcomes including mortality. We sought to compare machine learning (ML) approaches versus logistic regression analysis for prediction of mortality in lactic acidosis patients admitted to the ICU. Methods: We used the Medical Information Mart for Intensive Care (MIMIC-III) database to identify ICU adult patients with lactic acidosis (serum lactate ≥4 mmol/L). The outcome of interest was hospital mortality. We developed prediction models using four ML approaches consisting of random forest (RF), decision tree (DT), extreme gradient boosting (XGBoost), artificial neural network (ANN), and statistical modeling with forward stepwise logistic regression using the testing dataset. We then assessed model performance using area under the receiver operating characteristic curve (AUROC), accuracy, precision, error rate, Matthews correlation coefficient (MCC), F1 score, and assessed model calibration using the Brier score, in the independent testing dataset. Results: Of 1919 lactic acidosis ICU patients, 1535 and 384 were included in the training and testing dataset, respectively. Hospital mortality was 30%. RF had the highest AUROC at 0.83, followed by logistic regression 0.81, XGBoost 0.81, ANN 0.79, and DT 0.71. In addition, RF also had the highest accuracy (0.79), MCC (0.45), F1 score (0.56), and lowest error rate (21.4%). The RF model was the most well-calibrated. The Brier score for RF, DT, XGBoost, ANN, and multivariable logistic regression was 0.15, 0.19, 0.18, 0.19, and 0.16, respectively. The RF model outperformed multivariable logistic regression model, SOFA score (AUROC 0.74), SAP II score (AUROC 0.77), and Charlson score (AUROC 0.69). Conclusion: The ML prediction model using RF algorithm provided the highest predictive performance for hospital mortality among ICU patient with lactic acidosis.

Prevalence and risk factors of lactic acidosis in children with acute moderate and severe asthma, a prospective observational study

Lactic acidosis is a common complication of status asthmaticus in adults. However, data is sparse in children. The aim of this study was to describe the prevalence and risk factors for lactic acidosis in children hospitalised for acute moderate or severe asthma. A total of 154 children 2-17 years of age were enrolled in a prospective observational study conducted in a tertiary hospital. All had capillary blood gas assessment 4 h after the first dose of salbutamol in hospital. The primary endpoint was the prevalence of lactic acidosis. Potential contributing factors such as age, sex, BMI, initial degree of asthma severity, type of salbutamol administration (nebuliser or inhaler), steroids, ipratropium bromide, and glucose-containing maintenance fluid represented secondary endpoints. All in all, 87% of patients had hyperlactatemia (lactate concentration > 2.2 mmol/l). Lactic acidosis (lactate concentration > 5 mmol/l and anion gap ≥ 16 mmol/l) was observed in 26%. In multivariate analysis, age more than 6 years (OR = 2.8, 95% CI 1.2-6.6), glycemia above 11 mmol/l (OR = 3.2 95% CI 1.4-7.4), and salbutamol administered by nebuliser (OR = 10, 95% CI 2.7-47) were identified as risk factors for lactic acidosis in children with moderate or severe asthma.Conclusion: Lactic acidosis is a frequent and early complication of acute moderate or severe asthma in children. What is Known: • Lactic acidosis during acute asthma is associated with b2-mimetics administration. • Salbutamol-related lactic acidosis is self-limited but important to recognise, as compensatory hyperventilation of lactic acidosis can be mistaken for respiratory worsening and lead to inappropriate supplemental bronchodilator administration. What is New: • Lactic acidosis is a frequent complication of acute asthma in the paediatric population. • Age older than 6 years, hyperglycaemia, and nebulised salbutamol are risk factors for lactic acidosis during asthma.

Time-weighted lactate as a predictor of adverse outcome in acute heart failure

Aims

The role of dynamic changes in lactate concentrations on prognosis in acute heart failure has been poorly investigated. The aim of this study was to explore the predictive value of 24 h time‐weighted lactate (LAC_TW) in patients with acute heart failure.

Methods and results

Ninety‐six consecutive acute heart failure patients presenting to the Emergency Department of San Paolo Hospital, Naples, Italy, were prospectively enrolled. Arterial blood lactate was measured at admission and during the following 24 h at random time intervals. LAC_TW was obtained by the sum of the average lactate values among consecutive time points multiplied by the intervals between consecutive time points and dividing the sum by the total time (24 h). The outcome was a composite of need of admission to the intensive care unit, hospitalization duration >7 days, or intra‐hospital death. Admission lactate, maximum measured lactate, and LAC_TW were collected. Univariate and multivariate Cox regression analysis was applied to determine the hazard ratio (HR) of developing the outcome. Forty‐three patients experienced the pre‐specified outcome. In sex‐adjusted and age‐adjusted multivariable analysis, LAC_TW predicted the outcome occurrence (HR: 1.51, 95% confidence interval: 1.24, 1.84, P < 0.001). Risk stratification analysis based on LAC_TW tertiles demonstrated a gradual increase in risk of developing the outcome (HR: 17.32, 95% confidence interval: 2.30, 130.23, P = 0.006) for the highest LAC_TW tertile.

Conclusions

In acute heart failure patients, 24 h LAC_TW had a significant independent predictive value for adverse intra‐hospital outcome. LAC_TW could be a useful index at identifying high‐risk patients who may require a more aggressive treatment during hospitalization.

The Association between Metformin Therapy and Lactic Acidosis

INTRODUCTION AND OBJECTIVES

There is increasing evidence to suggest that therapeutic doses of metformin are unlikely to cause lactic acidosis. The aims of this research were (1) to formally evaluate the association between metformin therapy and lactic acidosis in published case reports using two causality scoring systems, (2) to determine the frequency of pre-existing independent risk factors in published metformin-associated lactic acidosis cases, (3) to investigate the association between risk factors and mortality in metformin-associated lactic acidosis cases, and (4) to explore the relationship between prescribed metformin doses, elevated metformin plasma concentrations and the development of lactic acidosis in cases with chronic renal impairment.

METHODS

A systematic review was conducted to identify metformin-associated lactic acidosis cases. Causality was assessed using the World Health Organisation-Uppsala Monitoring Centre system and the Naranjo adverse drug reaction probability scale. Compliance to dosing guidelines was investigated for cases with chronic renal impairment as well as the association between steady-state plasma metformin concentrations prior to admission.

RESULTS

We identified 559 metformin-associated lactic acidosis cases. Almost all cases reviewed (97%) presented with independent risk factors for lactic acidosis. The prescribed metformin dose exceeded published guidelines in 60% of cases in patients with impaired kidney function. Metformin steady-state plasma concentrations prior to admission were predicted to be below the proposed upper limit of the therapeutic range of 5 mg/L.

CONCLUSIONS

Almost all cases of metformin-associated lactic acidosis reviewed presented with independent risk factors for lactic acidosis, supporting the suggestion that metformin plays a contributory role. The prescribed metformin dose, on average, exceeded the dosing recommendations by 1000 mg/day in patients with varying degrees of renal impairment but the predicted pre-admission plasma concentrations did not exceed the therapeutic range.

Diagnostic et Prise en Charge de l’Acidose Métabolique Recommandations formalisées d’experts communes Société de réanimation de langue française (SRLF) – Société française de médecine d’urgence (SFMU)

L’acidose métabolique est un trouble fréquemment rencontré en médecine d’urgence et en médecine intensive réanimation. La littérature s’étant enrichie de nouvelles données concernant la prise en charge de l’acidose métabolique, la Société de Réanimation de Langue Française (SRLF) et la Société Française de Médecine d’Urgence (SFMU) ont élaboré des recommandations formalisées d’experts selon la méthodologie GRADE. Les champs de la stratégie diagnostique, de l’orientation et de la prise en charge thérapeutique ont été traités et vingt-neuf recommandations ont été formulées : quatre recommandations fortes (Grade 1), dix recommandations faibles (Grade 2) et quinze avis d’experts. Toutes ont obtenu un accord fort. L’application des méthodes d’Henderson-Hasselbalch et de Stewart pour le diagnostic du mécanisme de l’acidose métabolique est discutée et un algorithme diagnostique est proposé. L’utilisation de la cétonémie et des lactatémies veineuse et capillaire est également traitée. L’intérêt du pH, de la lactatémie et de sa cinétique pour l’orientation des patients en pré-hospitalier et aux urgences est envisagé. Enfin, les modalités de l’insulinothérapie au cours de l’acidocétose diabétique, les indications de la perfusion de bicarbonate de sodium et de l’épuration extra-rénale ainsi que les modalités de la ventilation mécanique au cours des acidoses métaboliques sévères sont traitées dans la prise en charge thérapeutique.

Diagnosis and management of metabolic acidosis: guidelines from a French expert panel

Metabolic acidosis is a disorder frequently encountered in emergency medicine and intensive care medicine. As literature has been enriched with new data concerning the management of metabolic acidosis, the French Intensive Care Society (Société de Réanimation de Langue Française [SRLF]) and the French Emergency Medicine Society (Société Française de Médecine d’Urgence [SFMU]) have developed formalized recommendations from experts using the GRADE methodology. The fields of diagnostic strategy, patient assessment, and referral and therapeutic management were addressed and 29 recommendations were made: 4 recommendations were strong (Grade 1), 10 were weak (Grade 2), and 15 were experts’ opinions. A strong agreement from voting participants was obtained for all recommendations. The application of Henderson–Hasselbalch and Stewart methods for the diagnosis of the metabolic acidosis mechanism is discussed and a diagnostic algorithm is proposed. The use of ketosis and venous and capillary lactatemia is also treated. The value of pH, lactatemia, and its kinetics for the referral of patients in pre-hospital and emergency departments is considered. Finally, the modalities of insulin therapy during diabetic ketoacidosis, the indications for sodium bicarbonate infusion and extra-renal purification as well as the modalities of mechanical ventilation during severe metabolic acidosis are addressed in therapeutic management.

Acid-Base Disturbances in Patients with Asthma: A Literature Review and Comments on Their Pathophysiology

Asthma is a common illness throughout the world that affects the respiratory system function, i.e., a system whose operational adequacy determines the respiratory gases exchange. It is therefore expected that acute severe asthma will be associated with respiratory acid-base disorders. In addition, the resulting hypoxemia along with the circulatory compromise due to heart–lung interactions can reduce tissue oxygenation, with a particular impact on respiratory muscles that have increased energy needs due to the increased workload. Thus, anaerobic metabolism may ensue, leading to lactic acidosis. Additionally, chronic hypocapnia in asthma can cause a compensatory drop in plasma bicarbonate concentration, resulting in non-anion gap acidosis. Indeed, studies have shown that in acute severe asthma, metabolic acid-base disorders may occur, i.e., high anion gap or non-anion gap metabolic acidosis. This review briefly presents studies that have investigated acid-base disorders in asthma, with comments on their underlying pathophysiology.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Lactic Acidosis in a Critically Ill Patient: Not Always Sepsis

Lactic acidosis in the emergency department and other hospital settings is typically due to tissue hypoxia with sepsis being the most common cause. However, in patients with persistently elevated lactate without evidence of inadequate oxygen delivery, type B lactic acidosis should be considered. We report the case of a 12-year-old boy with relapsed and refractory pre-B-cell acute lymphoblastic leukemia who presented in distress with tachycardia, history of fever, and diffuse abdominal tenderness. The patient had severe metabolic acidosis with elevated lactate upon arrival to the emergency department. Despite aggressive fluid resuscitation and intravenous antibiotics, the patient's acidosis worsened. Serial blood cultures were negative, and he was eventually diagnosed with type B lactic acidosis secondary to relapsed acute lymphoblastic leukemia.

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.

Recurrent Ethylene Glycol Poisoning with Elevated Lactate Levels to Obtain Opioid Medications

BACKGROUND

Malingering is when a patient feigns illness for secondary gain. While most patients with malingering manufacture or exaggerate symptoms, some patients may induce illness. Previous reports of malingering patients inducing illness include sepsis, kidney pain, migraine, and chest pain. However, acute poisoning as a manifestation of malingering appears to be rare.

CASE REPORT

We describe the case of a 39-year-old man who presented to the emergency department complaining of diffuse body pain. The patient reported multiple admission at outside hospitals for "lactate" and said, "it feels like it is happening again because of how my body feels." Laboratory findings were concerning for serum lactate of >20.0 mmol/L and ethylene glycol (EG) level of 19 mg/dL. A chart review found that the man had been admitted for elevated serum lactate 8 times to area hospitals in several years, often in the setting of EG poisoning. During these episodes he required intravenous fluids and frequent intravenous pain medications. When confronted about concern regarding the recurrent fallacious lactate levels in the setting of factitious EG ingestion, the patient often became combative and left against medical advice. The primary metabolite of EG, glycolic acid, can interfere with lactate assays, causing a false elevation. Our patient apparently recognized this and took advantage of it to be admitted and receive intravenous opioids. This is the only case known to us of malingering via EG ingestion. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should be aware that metabolites of EG may interfere with serum lactate assay. In addition, they should be aware of possible malingering-related poisoning and plausible association with requests for intravenous opioid pain medications. This represents a risk to the patient and others if undiagnosed.

Hypoglycemia and severe lactic acidosis in a dog following metformin exposure

Hypoglycemia and lactic acidosis are rare complications with metformin use in humans. As metformin is not commonly used in veterinary medicine, severe adverse effects secondary to exposure are not known. Awareness of potentially life-threatening complications with metformin exposure is an important addition to the veterinary literature.

Role of leucocytes cell population data in the early detection of sepsis

AIMS

The cell population data (CPD) parameters reported by XN analyser (Sysmex, Kobe, Japan) reflect the size and internal structure of leucocytes. We aimed to assess the clinical utility of these parameters as biomarkers for the early diagnosis of sepsis.

METHODS

The study group (G1) included 586 controls (no quantitative or morphological alterations in the complete blood count) and 137 patients diagnosed with sepsis. The reliability of the model was evaluated using a validation group (G2) of 212 controls and 60 patients with sepsis. The optimal cut-off for the diagnosis of sepsis and the OR for CPD were established using a univariate logistic regression. A multivariate logistic regression model was then created. The OR and area under the curve were recorded. A risk stratification scale (neutrophils and monocytes (NEMO)) for diagnosing sepsis was established on the basis of the coefficients of the multivariate model.

RESULTS

MO-X and neutrophils fluorescence intensity (NE-SFL) were found to be the most relevant of the CPD in predicting sepsis applying multivariate analysis to G1.NEMO score was composed using the above-mentioned CPD and subsequently stratified into three risk groups: mild (≤3), moderate (4≤NEMO≤5) and high (≥6). The OR for patients with a score of 4-5 was 10 and 249 for a score of ≥6. When applied to G2, the positive predictive value was 84.8 % and the negative predictive value was 96.0%.

CONCLUSIONS

CPD are potentially useful for the early diagnosis of sepsis. Their values were used to compose in NEMO score can help in rapid and reliable decision making.

Close correlation between arterial and central venous lactate concentrations of children in shock: A cross-sectional study

BACKGROUND

Arterial lactate (aLact) has been widely used to guide therapeutic decisions in children with shock. We evaluated the feasibility of central venous lactate (cvLact) in assessing aLact among children with shock.

METHODS

Pairs of arterial and central venous samples for lactate concentrations were collected simultaneously during the shock and hemodynamically stable states. The results were analyzed by using a Cobas 8000 analyzer.

RESULTS

Sixty-four blood paired samples were collected from 48 patients. The overall correlation between central venous and arterial lactate concentrations was r=0.962, p<0.0001, r²=0.965. The regression equation was aLact=(0.978×cvLact)-0.137. A similar correlation was found between central venous and arterial lactate concentrations during the states of shock and stable hemodynamics (r=0.970, p<0.0001, r²=0.966 and r=0.935, p<0.0001, r²=0.962, respectively). The mean difference between central venous and arterial lactate concentrations was 0.20mmol/l (95% CI: 0.08 to 0.32) and the limits of agreement were -0.74mmol/l (95% CI: -0.94 to -0.53) and 1.13 (95% CI: 0.93 to 1.34).

CONCLUSIONS

In situations of shock where a central venous catheter is required, samples from a central vein present an acceptable and timely alternative to arterial samples for quantitating lactate concentrations.

Perioperative factors associated with pressure ulcer development after major surgery

Background

Postoperative pressure ulcers are important indicators of perioperative care quality, and are serious and expensive complications during critical care. This study aimed to identify perioperative risk factors for postoperative pressure ulcers.

Methods

This retrospective case-control study evaluated 2,498 patients who underwent major surgery. Forty-three patients developed postoperative pressure ulcers and were matched to 86 control patients based on age, sex, surgery, and comorbidities.

Results

The pressure ulcer group had lower baseline hemoglobin and albumin levels, compared to the control group. The pressure ulcer group also had higher values for lactate levels, blood loss, and number of packed red blood cell (pRBC) units. Univariate analysis revealed that pressure ulcer development was associated with preoperative hemoglobin levels, albumin levels, lactate levels, intraoperative blood loss, number of pRBC units, Acute Physiologic and Chronic Health Evaluation II score, Braden scale score, postoperative ventilator care, and patient restraint. In the multiple logistic regression analysis, only preoperative low albumin levels (odds ratio [OR]: 0.21, 95% CI: 0.05-0.82; P < 0.05) and high lactate levels (OR: 1.70, 95% CI: 1.07-2.71; P < 0.05) were independently associated with pressure ulcer development. A receiver operating characteristic curve was used to assess the predictive power of the logistic regression model, and the area under the curve was 0.88 (95% CI: 0.79-0.97; P < 0.001).

Conclusions

The present study revealed that preoperative low albumin levels and high lactate levels were significantly associated with pressure ulcer development after surgery.

Recoverable, Record-High Lactic Acidosis in a Patient with Glycogen Storage Disease Type 1: A Mixed Type A and Type B Lactate Disorder

A 17-year-old patient with GSD type 1a (von Gierke disease) was hospitalized with an extremely elevated serum lactate following an intercurrent infection and interruption of his frequent intake of carbohydrates. The patient developed shock, oliguric renal failure, and cardiorespiratory failure requiring mechanical ventilation and inotropes. At the peak of metabolic decompensation and clinical instability, serum lactate reached a level of 47.6 mmol/L which was accompanied by a severe anion gap metabolic acidosis with a pH of 6.8 and bicarbonate of 4 meq/L. The patient was stabilized with massive infusions of sodium bicarbonate (45 meq/h) and glucose and recovered without the need for dialysis. This patient illustrates pathophysiologic mechanisms involved in the development of extreme mixed type A and type B lactic acidemia, reflecting altered metabolic pathways in GSD type 1, combined with tissue hypoperfusion. The rationale for the specific interventions in this case is outlined.

Gentisic acid sodium salt, a phenolic compound, is superior to norepinephrine in reversing cardiovascular collapse, hepatic mitochondrial dysfunction and lactic acidemia in Pseudomonas aeruginosa septic shock in dogs

BACKGROUND

The development of lactic acidemia (LA) in septic shock (SS) is associated with an ominous prognosis. We previously showed that the mechanism of LA in SS may relate to impaired hepatic uptake of lactate, but the mechanism was not clear. Uptake of lactate by the liver occurs by a membrane-associated, pH-dependent, antiport system known as the monocarboxylate transporter. In the hepatocyte, lactate can then be metabolized by oxidative phosphorylation or converted to glucose in the cytosol. In the present study, we examined (1) whether hepatic mitochondrial dysfunction accounted for decreased uptake of lactate in a canine model of Pseudomonas aeruginosa SS, (2) whether norepinephrine (NE) treatment by increasing mean arterial pressure (MAP) could improve mitochondrial dysfunction and LA in this model, and (3) whether gentisic acid sodium salt (GSS), a novel phenolic compound, was superior to NE in these effects.

METHODS

In anesthetized/ventilated dogs, we infused the bacteria over ~10 h and measured hemodynamics in various treatment groups (see below). We then euthanized the animal and isolated the hepatic mitochondria. We measured hepatic mitochondrial oxygen consumption rates using the novel Seahorse XF24 analyzer under conditions that included: basal respiration, after the addition of adenosine- diphosphate to produce coupled respiration, and after the addition of a protonophore to produce maximal respiration.

RESULTS

We found that in the septic control group, mean arterial pressure decreased over the course of the study, and that mitochondrial dysfunction developed in which there was a reduction in maximal respiration. Whereas both NE and GSS treatments reversed the reduction in mean arterial pressure and increased maximal respiration to similar extents in respective groups, only in the GSS group was there a reduction in LA.

CONCLUSIONS

Hepatic mitochondrial dysfunction occurs in SS, but does not appear to be required for the development of LA in SS, since NE improved mitochondrial dysfunction without reversing LA. GSS, a phenolic compound restored mean arterial pressure, mitochondrial dysfunction, and LA in SS. This reduction in LA may be independent of its effect on improving hepatic mitochondrial function.

Use of Lactate in Small Animal Clinical Practice

Lactate is a product of anaerobic metabolism. Lactate concentration in blood is used clinically as an indicator of tissue hypoperfusion and hypoxia to determine disease severity, assess response to therapy, and predict outcome. This article reviews lactate physiology, sample collection and processing, and interpretation of lactate concentration in clinical practice.

Diagnostic accuracy of peripheral venous lactate and the 2009 WHO warning signs for identifying severe dengue in Thai adults: a prospective observational study

Background

Dengue is the most common mosquito-borne viral disease in humans. However, the sensitivities of warning signs (WSs) for identifying severe dengue in adults are low, and the utility of lactate levels for identifying severe dengue in adults has not been verified. Therefore, we aimed to evaluate the diagnostic accuracy of using peripheral venous lactate levels (PVL), as well as WSs established by the World Health Organization, for identifying severe dengue.

Methods

We prospectively evaluated individuals hospitalized for dengue who were admitted to the Hospital for Tropical Diseases in Thailand between May 2013 and January 2015. Blood samples to evaluate PVL levels were collected at admission and every 24 h until the patient exhibited a body temperature of <37.8 °C for at least 24 h. Data were recorded on a pre-defined case report form, including baseline characteristics, clinical parameters, and laboratory findings.

Results

Among 125 patients with confirmed dengue, 105 (84.0 %) patients had non-severe dengue, and 20 (16.0 %) patients had severe dengue. The presence of clinical fluid accumulation as a WS provided high sensitivity (75.0 %, 95 % confidence interval [CI]: 50.9–91.3 %) and specificity (90.5 %, 95 % CI: 83.2–95.3 %). The PVL level at admission was used to evaluate its diagnostic value, and receiver operating characteristic curve analysis revealed an area under the curve of 0.84 for identifying severe dengue. At the optimal cutoff value (PVL: 2.5 mmol/L), the sensitivity and specificity were 65.0 % (95 % CI: 40.8–84.6 %) and 96.2 % (95 % CI: 90.5–99.0 %), respectively. A combined biomarker comprising clinical fluid accumulation and/or PVL of ≥2.5 mmol/L provided the maximum diagnostic accuracy for identifying severe dengue, with a sensitivity of 90.0 % (95 % CI: 68.3–98.8 %) and a specificity of 87.6 % (95 % CI: 79.8–93.2 %).

Conclusions

Clinical fluid accumulation and/or PVL may be used as a diagnostic biomarker of severe dengue among adults. This biomarker may facilitate early recognition and timely treatment of patients with severe dengue, which may reduce dengue-related mortality and hospital burden.

Hepatic Failure

The progression of liver disease can cause several physiologic derangements that may precipitate hepatic failure and require admission to an intensive care unit. The underlying pathology may be acute, acute-on chronic, or chronic in nature. Liver failure may manifest with a variety of clinical signs and symptoms that need prompt attention. The compromised synthetic and metabolic activity of the failing liver affects all organ systems, from neurologic to integumentary. Supportive care and specific therapies should be instituted in order to improve outcome and minimize time of recovery.

In this chapter we will discuss the definition, clinical manifestations, workup, and management of acute and chronic liver failure and the general principles of treatment of these patients. Management of liver failure secondary to certain common etiologies will also be presented. Finally, liver transplantation and alternative therapies will also be discussed.

[The role of biomarkers in the diagnostics of acute mesenteric ischemia]

Acute mesenteric ischemia is a severe and challenging disease. Unspecific symptoms in the initial phase make a fast diagnosis difficult although it is of major importance to protect patients from irreversible ischemia, extended bowel resection, sepsis and death in the late phase. In contrast to troponin as an early biomarker for cardiac ischemia, a reliable biomarker for acute intestinal ischemia has not yet been identified in the current literature and clinical practice. This would allow the early identification of these critically ill patients in the initial reversible phase of acute intestinal ischemia.This review highlights the pathophysiology, epidemiology and clinical findings of acute mesenteric ischemia and gives an overview of biomarkers which have been investigated in mesenteric ischemia with a special focus on lactate, which is the only parameter routinely used in the diagnostic setting of acute mesenteric ischemia.

Tissue oxygen saturation as an early indicator of delayed lactate clearance after cardiac surgery: a prospective observational study

Background

In this observational study near infrared spectroscopy (NIRS) was evaluated as a non-invasive monitor of impaired tissue oxygenation (StO₂) after cardiac surgery. StO₂, cardiac output, mixed venous oxygen saturation and mean arterial pressure were compared with lactate clearance as established measure for sufficient tissue perfusion and oxygen metabolism.

Methods

Forty patients after cardiac surgery (24 aortocoronary bypass grafting, 5 heart valve, 3 ascending aorta and 8 combined procedures) were monitored until postoperative day 1 with NIRS of the thenar muscle (InSpectra™ StO₂-monitor, Hutchinson Technology), a pulmonary-artery catheter and intermittent blood gas analyses for the assessment of lactate clearance.

Results

StO₂ was reduced 4 h after surgery (75 ± 6 %), but recovered at day 1 (84 ± 5 %), while lactate concentration remained increased. Using uni- and multivariate regression analysis, minimum StO₂ (r = 0.46, p <0.01) and cardiac index (r = 0.40, p <0.05) correlated with lactate clearance at day 1, while minimum mixed venous saturation and mean arterial pressure did not. In a receiver-operating characteristics (ROC) analysis, minimum StO₂ (with a threshold of 75 %) predicted a lactate clearance <10 % at day 1 with an area under the ROC-curve of 0.83, a sensitivity of 78 % and a specificity of 88 %. In the subgroup with StO₂  <75 %, troponin and creatine kinase MB were significantly increased at day 1.

Conclusions

StO₂ below 75 % in the first hours after surgery was a better early indicator of persistent impaired lactate clearance at day 1 than cardiac index, mixed venous oxygen saturation or mean arterial pressure.

Emergency Department Management of Sepsis Patients: A Randomized, Goal-Oriented, Noninvasive Sepsis Trial

STUDY OBJECTIVE

The noninvasive cardiac output monitor and passive leg-raising maneuver has been shown to be reasonably accurate in predicting fluid responsiveness in critically ill patients. We examine whether using a noninvasive protocol would result in more rapid lactate clearance after 3 hours in patients with severe sepsis and septic shock in the emergency department.

METHODS

In this open-label randomized controlled trial, 122 adult patients with sepsis and serum lactate concentration of greater than or equal to 3.0 mmol/L were randomized to receive usual care or intravenous fluid bolus administration guided by measurements of change of stroke volume index, using the noninvasive cardiac output monitor after passive leg-raising maneuver. The primary outcome was lactate clearance of more than 20% at 3 hours. Secondary outcomes included mortality, length of hospital and ICU stay, and total hospital cost. Analysis was intention to treat.

RESULTS

Similar proportions of patients in the randomized intervention group (70.5%; N=61) versus control group (73.8%; N=61) achieved the primary outcome, with a relative risk of 0.96 (95% confidence interval [CI] 0.77 to 1.19). Secondary outcomes were similar in both groups (P>.05 for all comparisons). Hospital mortality occurred in 6 patients (9.8%) each in the intervention and control groups on or before 28 days (relative risk=1.00; 95% CI 0.34 to 2.93). Among a subgroup of patients with underlying fluid overload states, those in the intervention group tended to receive clinically significantly more intravenous fluids at 3 hours (difference=975 mL; 95% CI -450 to 1,725 mL) and attained better lactate clearance (difference=19.7%; 95% CI -34.6% to 60.2%) compared with the control group, with shorter hospital lengths of stay (difference=-4.5 days; 95% CI -9.5 to 2.5 days).

CONCLUSION

Protocol-based fluid resuscitation of patients with severe sepsis and septic shock with the noninvasive cardiac output monitor and passive leg-raising maneuver did not result in better outcomes compared with usual care. Future studies to demonstrate the use of the noninvasive protocol-based care in patients with preexisting fluid overload states may be warranted.

Association between serum lactate levels and early neurogenic pulmonary edema after nontraumatic subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Few studies have described the risk factors associated with the development of neurological pulmonary edema (NPE) after subarachnoid hemorrhage (SAH). We have hypothesized that acute-phase increases in serum lactate levels are associated with the early development of NPE following SAH. The aim of this study was to clarify the association between lactic acidosis and NPE in patients with nontraumatic SAH.

METHODS

We retrospectively evaluated 140 patients with nontraumatic SAH who were directly transported to the Nippon Medical School Hospital emergency room by the emergency medical services. We compared patients in whom NPE developed (NPE group) and those in whom it did not (non-NPE group).

RESULTS

The median (quartiles 1-3) arrival time at the hospital was 32 minutes (28-38 minutes) after the emergency call was received. Although the characteristics of the NPE and non-NPE groups, including mean arterial pressure (121.3 [109.0-144.5] and 124.6 [108.7-142.6] mm Hg, respectively; P=0.96), were similar, the median pH and the bicarbonate ion (HCO3(-)) concentrations were significantly lower in the NPE group than in the non-NPE group (pH, 7.33 [7.28-7.37] vs. 7.39 [7.35-7.43]); P=0.002; HCO3(-), 20.8 [18.6-22.6] vs. 22.8 [20.9-24.7] mmol/L; P=0.01). The lactate concentration was significantly higher in the NPE group (54.0 [40.3-61.0] mg/dL) than in the non-NPE group (28.0 [17.0-37.5] mg/dL; P<0.001). Multivariable regression analysis indicated that younger age and higher glucose and lactate levels were significantly associated with the early onset of NPE in patients with SAH.

CONCLUSION

The present findings indicate that an increased serum lactate level, occurring within 1 hour of the ictus, is an independent factor associated with the early onset of NPE. Multicenter prospective studies are required to confirm our results.

Type B lactic acidosis secondary to thiamine deficiency in a child with malignancy

Type B lactic acidosis is an underrecognized clinical entity that must be distinguished from type A (hypoxic) lactic acidosis. We present the case of a 4-year-old boy with medulloblastoma who presented with lactic acidosis in the setting of septic shock. His hyperlactatemia persisted to high levels even after his hemodynamic status improved. After administration of intravenous thiamine, his lactate level rapidly normalized and remained stable. It was determined that his total parenteral nutrition was deficient in vitamins due to a national shortage. Because thiamine is an important cofactor for pyruvate dehydrogenase, he was unable to use glucose through aerobic metabolism pathways. We briefly review type A versus type B lactic acidosis in this case report.

Development and validation of a novel derivatization method for the determination of lactate in urine and saliva by liquid chromatography with UV and fluorescence detection

We developed a novel and straightforward derivatization method for the determination of lactate by reversed phase high-performance liquid chromatography (RP-HPLC) with fluorescence and UV detection in biological matrices as urine and saliva. The derivatization of lactate was achieved employing 9-chloromethyl anthracene (9-CMA) as fluorescence reagent, which has never been previously used to obtain a lactate derivative. Lactate reacts with 9-CMA with high selectivity in a very short time, without requiring extraction procedures from the aqueous solution, and the reaction reaches 70% completion in 30 min. The ester derivative obtained can be easily determined by RP-HPLC with fluorescence detection at 410 nm (λ ex=365 nm) and UV detection at 365 nm. The method was also optimized in order to allow for the simultaneous determination of lactate and creatinine for the application to urine samples. The lactate calibration curve was linear in the investigated range 2 × 10(-4)-3 × 10(-2)mM and the limit of detection, calculated as three times the standard deviation of the blank divided by the calibration curve slope, was 50 nM for both fluorescence and UV detection. Intra-day and inter-day repeatability were lower than 5% and 6%, respectively. The method proposed was successfully applied to the analysis of urine and saliva samples.

Acute renal failure and type B lactic acidosis as first manifestation of extranodal T-cell lymphoblastic lymphoma

We describe a rare case of a 19-year-old male patient with a history of epilepsy and developmental delay who presented with acute renal failure (ARF) and lactic acidosis (LA) as the first manifestation of T-cell lymphoblastic lymphoma. Renal ultrasound and CT of the abdomen showed renal parenchymal infiltration, and renal biopsy demonstrated T-cell lymphoblastic lymphoma. LA, ARF and electrolyte abnormalities were refractory to the initial treatment of bicarbonate infusion and hydration. However, these abnormalities rapidly normalised after the initiation of chemotherapy, suggesting that the LA and ARF were secondary to lymphomatous renal infiltration.

Hypoxemia predicts death from severe falciparum malaria among children under 5 years of age in Nigeria: the need for pulse oximetry in case management

BACKGROUND

Oxygen saturation is a good marker for disease severity in emergency care. However, studies have not considered its use in identifying individuals infected with Plasmodium falciparum at risk of deaths.

OBJECTIVE

To investigate the prevalence and predictive value of hypoxaemia for deaths in under-5s with severe falciparum malaria infection.

METHODS

Oxygen saturation was prospectively measured alongside other indicators of disease severity in 369 under-5s admitted to a tertiary hospital in Nigeria. Participants were children in whom falciparum malaria parasitaemia was confirmed with blood film microscopy in the presence of any of the World Health Organization-defined life-threatening features for malaria.

RESULTS

Overall mortality rate was 8.1%. Of the 16 indicators of the disease severity assessed, hypoxaemia (OR=7.54; 95% CI=2.80, 20.29), co-morbidity with pneumonia (OR=19.27; 95% CI=2.87, 29.59), metabolic acidosis (OR=6.21; 95% CI=2.21, 17.47) and hypoglycaemia (OR=19.71; 95% CI=2.61, 25.47) were independent predictors of death. Cerebral malaria, male gender, wasting, hypokalaemia, hyponatriaemia, azotaemia and renal impairment were significantly associated with death in univariate analysis but not logistic regression model.

CONCLUSIONS

Hypoxaemia predicts deaths in Nigerian children with severe malaria, irrespective of other features. Efforts should always be made to measure oxygen saturation as part of the treatments for severe malaria in children.