Lactate and glucose metabolism in severe sepsis and cardiogenic shock

Early blood lactate area as a prognostic marker in pediatric septic shock

PURPOSE

We attempted to evaluate whether the early lactate area is useful as an early prognostic marker of mortality in pediatric septic shock patients.

METHODS

We performed a retrospective study of pediatric patients with septic shock who were admitted to the pediatric intensive care unit of Asan Medical Center, Seoul, Korea. Serial arterial lactate levels were obtained immediately and then every 6 h after admission for a total of 24 h. The lactate area (mmol/lh) was defined as the sum of the area under the curve (AUC) of serial lactate levels measured during the 24 h following admission. We compared the lactate-associated parameters as a predictor of mortality.

RESULTS

A total of 65 patients were included in this study, and the overall 28-day mortality of these patients was 26.2%. Survivors compared with non-survivors had an initial lactate level of 3.13 ± 2.79 vs. 6.16 ± 4.87 mmol/l, a lactate clearance of 32.8 ± 63.4 vs. -30.8 ± 75.6%, and a lactate area of 59.7 ± 56.0 vs. 168.0 ± 107.0 mmol/lh (p < 0.05 for all variables). Receiver operating characteristic curves indicated a strong predictive power for the lactate area (AUC = 0.828), which demonstrated the largest AUC in comparison with the AUCs of the initial lactate level (0.699) or the 24-h lactate clearance (0.719). Using multivariate logistic regression analysis, the lactate area was a significant prognostic factor.

CONCLUSION

The early lactate area is a potentially feasible and clinically useful predictor of mortality in pediatric septic shock patients.

Combined APACH II score and arterial blood lactate clearance rate to predict the prognosis of ARDS patients

OBJECTIVE

To explore the easily applicable indicators of practical value to evaluate the prognosis of acute respiratory distress syndrome (ARDS).

METHODS

Blood and biochemical tests and blood-gas analyses were performed upon entry into the ICUs, 12 h, 24 h, 48 h and 72 h after that in 72 ARDS patients (who were admitted to the ICUs of our hospital from January 2000 to December 2009). Then APACHE II scores were achieved by combining relevant physiological parameters and laboratory results.

RESULTS

There was a statistical difference between the death group and survival group at different time points upon entering the ICUs in terms of APACHE II score, alveolar-arterial oxygen difference and arterial blood lactate clearance rate. PaO(2)/FiO(2) values were recorded to be statistically different between the death group and survival group 24 h, 48 h and 72 h, respectively after entry into the ICUs. In addition, registered linear regression existed between APACHE II score, alveolar-arterial oxygen difference or PaO(2)/FiO(2) value and time. APACHE II score 24 h and 72 h after entering ICUs predicted mortality with an area under the ROC curve (AUC) standing respectively at 0.919 and 0.955. Arterial blood lactate clearance rate 12 h, 24 h, 48 h and 72 h after entering ICUs predicted mortality with an area under the ROC curve (AUC) at 0.918, 0.918, 0.909 and 0.991, respectively.

CONCLUSIONS

APACHE II score applied in combination with arterial blood lactate clearance rate is of clinical significance in assessing the prognosis of ARDS patients.

Hyperlactatemia affects the association of hyperglycemia with mortality in nondiabetic adults with sepsis

BACKGROUND

Admission hyperglycemia has been reported as a mortality risk factor for septic nondiabetic patients; however, hyperglycemia's known association with hyperlactatemia was not addressed in these analyses.

OBJECTIVES

The objective was to determine whether the association of hyperglycemia with mortality remains significant when adjusted for concurrent hyperlactatemia.

METHODS

This was a post hoc, nested analysis of a retrospective cohort study performed at a single center. Providers had identified study subjects during their emergency department (ED) encounters; all data were collected from the electronic medical record (EMR). Nondiabetic adult ED patients hospitalized for suspected infection, two or more systemic inflammatory response syndrome (SIRS) criteria, and simultaneous lactate and glucose testing in the ED were enrolled. The setting was the ED of an urban teaching hospital from 2007 to 2009. To evaluate the association of hyperglycemia (glucose > 200 mg/dL) with hyperlactatemia (lactate ≥ 4.0 mmol/L), a logistic regression model was created. The outcome was a diagnosis of hyperlactatemia, and the primary variable of interest was hyperglycemia. A second model was created to determine if coexisting hyperlactatemia affects hyperglycemia's association with mortality; the main outcome was 28-day mortality, and the primary risk variable was hyperglycemia with an interaction term for simultaneous hyperlactatemia. Both models were adjusted for demographics; comorbidities; presenting infectious source; and objective evidence of renal, respiratory, hematologic, or cardiovascular dysfunction.

RESULTS

A total of 1,236 ED patients were included, and the median age was 77 years (interquartile range [IQR] = 60 to 87 years). A total of 115 (9.3%) subjects were hyperglycemic, 162 (13%) were hyperlactatemic, and 214 (17%) died within 28 days of their initial ED visits. After adjustment, hyperglycemia was significantly associated with simultaneous hyperlactatemia (odds ratio [OR] = 4.14, 95% confidence interval [CI] = 2.65 to 6.45). Hyperglycemia and concurrent hyperlactatemia were associated with increased mortality risk (OR = 3.96, 95% CI = 2.01 to 7.79), but hyperglycemia in the absence of simultaneous hyperlactatemia was not (OR = 0.78, 95% CI = 0.39 to 1.57).

CONCLUSIONS

In this cohort of septic adult nondiabetic patients, mortality risk did not increase with hyperglycemia unless associated with simultaneous hyperlactatemia. The previously reported association of hyperglycemia with mortality in nondiabetic sepsis may be due to the association of hyperglycemia with hyperlactatemia.

Phosphorylation of mammalian cytochrome c and cytochrome c oxidase in the regulation of cell destiny: respiration, apoptosis, and human disease

The mitochondrial oxidative phosphorylation (OxPhos) system not only generates the vast majority of cellular energy, but is also involved in the generation of reactive oxygen species (ROS), and apoptosis. Cytochrome c (Cytc) and cytochrome c oxidase (COX) represent the terminal step of the electron transport chain (ETC), the proposed rate-limiting reaction in mammals. Cytc and COX show unique regulatory features including allosteric regulation, isoform expression, and regulation through cell signaling pathways. This chapter focuses on the latter and discusses all mapped phosphorylation sites based on the crystal structures of COX and Cytc. Several signaling pathways have been identified that target COX including protein kinase A and C, receptor tyrosine kinase, and inflammatory signaling. In addition, four phosphorylation sites have been mapped on Cytc with potentially large implications due to its multiple functions including apoptosis, a pathway that is overactive in stressed cells but inactive in cancer. The role of COX and Cytc phosphorylation is reviewed in a human disease context, including cancer, inflammation, sepsis, asthma, and ischemia/reperfusion injury as seen in myocardial infarction and ischemic stroke.

Effects of endotoxin on lactate metabolism in humans

Introduction

Hyperlactatemia represents one prominent component of the metabolic response to sepsis. In critically ill patients, hyperlactatemia is related to the severity of the underlying condition. Both an increased production and a decreased utilization and clearance might be involved in this process, but their relative contribution remains unknown. The present study aimed at assessing systemic and muscle lactate production and systemic lactate clearance in healthy human volunteers, using intravenous endotoxin (LPS) challenge.

Methods

Fourteen healthy male volunteers were enrolled in 2 consecutive studies (n = 6 in trial 1 and n = 8 in trial 2). Each subject took part in one of two investigation days (LPS-day with endotoxin injection and placebo-day with saline injection) separated by one week at least and in a random order. In trial 1, their muscle lactate metabolism was monitored using microdialysis. In trial 2, their systemic lactate metabolism was monitored by means of a constant infusion of exogenous lactate. Energy metabolism was monitored by indirect calorimetry and glucose kinetics was measured with 6,6-H₂ glucose.

Results

In both trials, LPS increased energy expenditure (p = 0.011), lipid oxidation (p<0.0001), and plasma lactate concentration (p = 0.016). In trial 1, lactate concentration in the muscle microdialysate was higher than in blood, indicating lactate production by muscles. This was, however, similar with and without LPS. In trial 2, calculated systemic lactate production increased after LPS (p = 0.031), while lactate clearance remained unchanged.

Conclusions

LPS administration increases lactatemia by increasing lactate production rather than by decreasing lactate clearance. Muscle is, however, unlikely to be a major contributor to this increase in lactate production.

Trial registration

ClinicalTrials.gov NCT01647997

Initial emergency department diagnosis and management of adult patients with severe sepsis and septic shock

Severe sepsis is a medical emergency affecting up to 18 million individuals world wide, with an annual incidence of 750,000 in North America alone. Mortality ranges between 28-50% of those individuals stricken by severe sepsis. Sepsis is a time critical illness, requiring early identification and prompt intervention in order to improve outcomes. This observation has led to increased awareness and education in the field of Emergency Medicine; it has also led to the implementation of critical interventions early in the course of patient management, specifically Early-Goal Directed Therapy, and rapid administration of appropriate antimicrobials. This review begins with a brief summary of the pathophysiology of sepsis, and then addresses the fundamental clinical aspects of ED identification and resuscitation of the septic patient.

Lactate/pyruvate ratio as a marker of tissue hypoxia in circulatory and septic shock

In this prospective, observational study, we measured arterial lactate and pyruvate concentrations within the first four hours of shock and at four hour intervals during the first 24 hours in 26 patients with septic and 13 with cardiogenic shock. We also studied 10 intensive care unit patients with normal lactate levels as controls. Seven patients (18%) died during the first 24 hours of shock, 12 (31%) patients died later in the intensive care unit and 21 (54%) were discharged alive from the intensive care unit. Blood lactate values were higher at shock onset in the non-survivors than in the survivors (P=0.02) and remained significantly elevated throughout the study. The lactate/pyruvate ratio at shock onset was significantly higher in the non-survivors (24 [17 to 34] vs 15 [10 to 19], P=0.01) than in the survivors. All patients with cardiogenic shock had hyperlactataemia at the onset of shock, and 69% had a high lactate/pyruvate ratio. Only 65% of patients with septic shock had hyperlactataemia at the onset of shock and 76% of these also had a high lactate/pyruvate ratio. In conclusion, the lactate/pyruvate ratio confirms that hyperlactataemia is frequently, but not solely, due to hypoxia, especially at the onset of shock.

Early rehabilitation in sepsis: a prospective randomised controlled trial investigating functional and physiological outcomes The i-PERFORM Trial (Protocol Article)

BACKGROUND

Patients with sepsis syndromes in comparison to general intensive care patients can have worse outcomes for physical function, quality of life and survival. Early intensive care rehabilitation can improve the outcome in general Intensive Care Unit (ICU) patients, however no investigations have specifically looked at patients with sepsis syndromes. The 'i-PERFORM Trial' will investigate if early targeted rehabilitation is both safe and effective in patients with sepsis syndromes admitted to ICU.

METHODS/DESIGN

A single-centred blinded randomized controlled trial will be conducted in Brisbane, Australia. Participants (n = 252) will include those ≥ 18 years, mechanically ventilated for ≥ 48 hours and diagnosed with a sepsis syndrome. Participants will be randomised to an intervention arm which will undergo an early targeted rehabilitation program according to the level of arousal, strength and cardiovascular stability and a control group which will receive normal care.The primary outcome measures will be physical function tests on discharge from ICU (The Acute Care Index of Function and The Physical Function ICU Test). Health-related quality of life will be measured using the Short Form-36 and the psychological component will be tested using The Hospital Anxiety and Depression Scale. Secondary measures will include inflammatory biomarkers; Interleukin-6, Interleukin-10 and Tumour Necrosis Factor-α, peripheral blood mitochondrial DNA content and lactate, fat free muscle mass, tissue oxygenation and microcirculatory flow.

DISCUSSION

The 'i-PERFORM Trial' will determine whether early rehabilitation for patients with sepsis is effective at improving patient outcomes with functional and physiological parameters reflecting long and short-term effects of early exercise and the safety in its application in critical illness.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000808044.

Lactate: biomarker and potential therapeutic target

Lactate levels are frequently elevated in critically ill patients and correlate well with disease severity. Elevated lactate levels are prognostic in prehospital, emergency department, and intensive care unit settings. This review discusses the role of lactate as a biomarker in diagnosing and assessing the severity of systemic hypoperfusion, as well as the role of serum lactate measurements in guiding clinical care and enabling prognosis in critically ill patients.

Monocarboxylate Transporter Inhibition with Osmotic Diuresis Increases γ-Hydroxybutyrate Renal Elimination in Humans: A Proof-of-Concept Study

BACKGROUND AND OBJECTIVE

The purpose of the current study was to demonstrate proof-of-concept that monocarboxylate transporter (MCT) inhibition with L-lactate combined with osmotic diuresis increases renal clearance of γ-hydroxybutyrate (GHB) in human subjects. GHB is a substrate for human and rodent MCTs, which are responsible for GHB renal reabsorption, and this therapy increases GHB renal clearance in rats.

METHODS

Ten healthy volunteers were administered GHB orally as sodium oxybate 50 mg/kg (4.5 gm maximum dose) on two different study days. On study day 1, GHB was administered alone. On study day 2, treatment of L-lactate 0.125 mmol/kg and mannitol 200 mg/kg followed by L-lactate 0.75 mmol/kg/hr was administered intravenously 30 minutes after GHB ingestion. Blood and urine were collected for 6 hours, analyzed for GHB, and pharmacokinetic and statistical analyses performed.

RESULTS

L-lactate/mannitol administration significantly increased GHB renal clearance compared to GHB alone, 439 vs. 615 mL/hr (P=0.001), and increased the percentage of GHB dose excreted in the urine, 2.2 vs. 3.3% (P=0.021). Total clearance was unchanged.

CONCLUSIONS

MCT inhibition with L-lactate combined with osmotic diuresis increases GHB renal elimination in humans. No effect on total clearance was observed in this study due to the negligible contribution of renal clearance to total clearance at this low GHB dose. Considering the nonlinear renal elimination of GHB, further research in overdose cases is warranted to assess the efficacy of this treatment strategy for increasing renal and total clearance at high GHB doses.

Hemodynamic and perfusion end points for volemic resuscitation in sepsis

Sepsis is the systemic inflammatory response syndrome secondary to a local infection, and severe sepsis and septic shock are the more devastating scenarios of this disease. In the last decade, considerable achievements were obtained in sepsis knowledge, and an international campaign was developed to improve the treatment of this condition. However, sepsis is still one of the most important causes of death in intensive care units. The early stages of sepsis are characterized by a variety of hemodynamic derangements that induce a systemic imbalance between tissue oxygen supply and demand, leading to global tissue hypoxia. This dysfunction, which may occur in patients presenting normal vital signs, can be accompanied by a significant increase in both morbidity and mortality. The early identification of high-risk sepsis patients through tissue perfusion markers such as lactate and venous oxygen saturation is crucial for prompt initiation of therapeutic support, which includes early goal-directed therapy as necessary. The purpose of this article was to review the most commonly used hemodynamic and perfusion parameters for hemodynamic optimization in sepsis, emphasizing the physiological background for their use and the studies that demonstrated their effectiveness as goals of volemic resuscitation.

Lactate in the acute phase of ST-elevation myocardial infarction treated with mechanical revascularization: a single-center experience

AIMS

The prognostic role (if any) of lactate for early mortality in patients with ST-elevation myocardial infarction (STEMI) submitted to primary percutaneous coronary intervention (PCI) is so far not elucidated. We therefore assessed whether lactic acid (LA) was a prognostic predictor for early mortality in 807 patients with STEMI submitted to primary PCI consecutively admitted to our intensive cardiac care unit (ICCU) from January 1, 2006, to December 31, 2009.

RESULT

Higher levels of LA were found in older patients (P = .025) and were associated with a progressive decline in estimated glomerular filtration rate (P < .001) and in ejection fraction (P < .001). The increase in LA values paralleled the progressive increase in glucose values, peak glycemia, troponin I, N-terminal pro-brain natriuretic peptide, and uric acid (P < .001, P < .001, P < .001, P = .018, and P = .006, respectively). The in-ICCU mortality rate was highest in the third LA tertile (P < .001). Lactate levels were independent predictors for in-hospital mortality only in patients with Killip classes III to IV (odds ratio [OR], 1.17; 95% confidence interval [CI], 1.05-1.30, P = .003). In addition, age (OR, 1.11; 95% CI, 1.03-1.19, P = .006) and leukocytes (OR, 1.17; 95% CI, 1.03-1.33, P = .015) were independent predictors for in-hospital mortality when adjusted for PCI failure.

CONCLUSION

In patients with STEMI submitted to primary PCI, blood lactate is a prognostic marker for early mortality only in the subgroup with advanced Killip class. The degree of hemodynamic impairment (as indicated by Killip class), of myocardial ischemia (as inferred by troponin I), and glucose values are the main factors influencing lactate concentrations in the early phase of STEMI.

Intensive care unit admission parameters improve the accuracy of operative mortality predictive models in cardiac surgery

BACKGROUND

Operative mortality risk in cardiac surgery is usually assessed using preoperative risk models. However, intraoperative factors may change the risk profile of the patients, and parameters at the admission in the intensive care unit may be relevant in determining the operative mortality. This study investigates the association between a number of parameters at the admission in the intensive care unit and the operative mortality, and verifies the hypothesis that including these parameters into the preoperative risk models may increase the accuracy of prediction of the operative mortality.

METHODOLOGY

929 adult patients who underwent cardiac surgery were admitted to the study. The preoperative risk profile was assessed using the logistic EuroSCORE and the ACEF score. A number of parameters recorded at the admission in the intensive care unit were explored for univariate and multivariable association with the operative mortality.

PRINCIPAL FINDINGS

A heart rate higher than 120 beats per minute and a blood lactate value higher than 4 mmol/L at the admission in the intensive care unit were independent predictors of operative mortality, with odds ratio of 6.7 and 13.4 respectively. Including these parameters into the logistic EuroSCORE and the ACEF score increased their accuracy (area under the curve 0.85 to 0.88 for the logistic EuroSCORE and 0.81 to 0.86 for the ACEF score).

CONCLUSIONS

A double-stage assessment of operative mortality risk provides a higher accuracy of the prediction. Elevated blood lactates and tachycardia reflect a condition of inadequate cardiac output. Their inclusion in the assessment of the severity of the clinical conditions after cardiac surgery may offer a useful tool to introduce more sophisticated hemodynamic monitoring techniques. Comparison between the predicted operative mortality risk before and after the operation may offer an assessment of the operative performance.

Evaluation of acid-base balance in ST-elevation myocardial infarction in the early phase: a prognostic tool?

OBJECTIVES

Metabolic acidosis has been described after myocardial infarction, but little data are available on the acid-base imbalance in ST-elevation myocardial infarction (STEMI) submitted to mechanical revascularization, and earlier studies on this topic differ with respect to patients' selection criteria, treatment and evaluated parameters.

METHODS

We assessed admission base excess, anion gap, and lactate in 445 consecutive patients with STEMI submitted to primary percutaneous coronary intervention and whether its evaluation could help in identifying patients at a higher risk for in-hospital mortality and complications (acute pulmonary edema and arrhythmias).

RESULTS

At backward stepwise logistic regression analysis, the following variables were independently associated with intra-ICCU mortality: age [odds ratio (OR) 1.05; 95% confidence interval (CI) 1.02-1.10; P = 0.006], estimated glumerular filtration rate (OR 0.98; 95% CI 0.96-0.99; P= 0.010), Tn I (OR 1.006; 95% CI 1.004-1.008; P <0.001), and base excess (OR 0.90; 95% CI 0.82-0.99; P = 0.038); Hosmer-Lemeshow v2: 5.69, P = 0.681. At backward stepwise logistic regression analysis, the following variables were independently associated with intra-ICCU complications: left ventricular ejection fraction (OR 0.95; 95% CI 0.91-0.98; P = 0.005) and lactic acid (OR 1.31; 95% CI 1.10-1.57; P =0.003); Hosmer-Lemeshow v2: 4.11, P = 0.847.

CONCLUSION

According to our findings, the evaluation of base excess and lactate in the early phase of STEMI provides the bedside clinicians with useful tools for early risk stratification. In fact, base excess proved to be an independent predictor for intra-ICCU mortality, whereas lactate represented an independent marker for intra-ICCU complications.

The value of initial lactate in patients with carbon monoxide intoxication: in the emergency department

Patients with carbon monoxide (CO) poisoning have been found to have a correlation between initial clinical severity on admission and blood lactate levels. Recently, it is suggested that the lactate level may be a useful prognostic factor in cases study. The purpose of this study was to determine whether lactate levels were associated with the short-term outcome of patients with CO poisoning and identify the characteristics of patients with high initial lactate levels. Eighty patients that presented to the Chonnam National University Hospital after CO poisoning, over 5 years, were enrolled in this retrospective study. Fifty-six (70.0%) patients had high lactate (>2.1 mmo/L) on admission. Thirty-three (41.3%) patients had medical complications and one patient (1.3%) died. The patients with high initial lactate had an altered mental status more frequently, higher WBC, glucose and carboxyhemoglobin (COHb), and lower base deficit on admission. The multivariate analysis showed that lactate was an independent factor associated with serious complications and the need for intensive medical treatment, along with advanced age, WBC, and altered mental status on admission. The results of this study show that the initial lactate was useful for patient prognosis after CO poisoning.

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.

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.

Molecular mechanisms behind clinical benefits of intensive insulin therapy during critical illness: glucose versus insulin

High blood glucose levels have been associated with morbidity and poor outcome in critically ill patients, irrespective of underlying pathology. In a large, randomised, controlled study the use of insulin therapy to maintain normoglycaemia for at least a few days improved survival and reduced morbidity of patients who are in a surgical intensive care unit (ICU). Since the publication of this landmark study, several other investigators have provided support for, whereas others have questioned, the beneficial effects of intensive insulin therapy. In this review, we discuss the investigated potential molecular mechanisms behind the clinical benefits of intensive insulin therapy. We first describe the molecular origin of hyperglycaemia and the impact of the therapy on insulin sensitivity. Next, the molecular basis of glucose toxicity in critical illness and the impact of intensive insulin therapy hereon are described, as well as other non-glucose-toxicity-related metabolic effects of intensive insulin therapy.

Acid-base imbalance in uncomplicated ST-elevation myocardial infarction: the clinical role of tissue acidosis

Little information is available on acid-base imbalance in uncomplicated ST-elevation myocardial infarction (STEMI) submitted to primary percutaneous intervention (PCI). We therefore assessed acid-base imbalance in 257 consecutive uncomplicated STEMI patients submitted to PCI to determine whether its evaluation could help in identifying patients at higher risk for in-hospital complications (acute pulmonary edema and dysrhythmias). A basic metabolic profile was performed at hospital admission, that is before PCI. After PCI, we measured: creatinine, uric acid and NT-pro BNP and serum electrolytes. Peak troponin I was also considered. Acidemia was present in 11 patients (4.2%), HCO(3) < 22 in 62 (24.1%). Base excess < -3 was detectable in 70 patients (27.2%), anion gap > 12 in 13 (5.1%), Cl/Na < 0.79 in 93 patients (38.5%). Patients with a Cl/Na < 0.79 had a lower LVEF (p = 0.042) and higher values of NT-pro-BNP (p = 0.019) and of latency (p = 0.029) together with a higher length of stay (p = 0.017) and a higher incidence of in-hospital complications (p = 0.017). At backward stepwise regression analysis, the following variables resulted independent predictors of in-hospital complications: base excess OR 1.47 (95% CI 1.04-2.10) p = 0.031; Cl/Na ratio O.R. 1.85 (95% CI 1.05-3.27) p = 0.035. In STEMI patients submitted to mechanical revascularization the evaluation of acid-base status and, in particular the detection of even mild degrees of acidosis may help in risk stratification for in-hospital complications. A Cl/Na < 0.79 ratio and a base excess are independent predictors for in-hospital complications.

Training in hypoxia fails to further enhance endurance performance and lactate clearance in well-trained men and impairs glucose metabolism during prolonged exercise

The aim of this study was to investigate the synergistic effects of endurance training and hypoxia on endurance performance in normoxic and hypoxic conditions (approximately 3000 m above sea level) as well as on lactate and glucose metabolism during prolonged exercise. For this purpose, 14 well-trained cyclists performed 12 training sessions in conditions of normobaric hypoxia (HYP group, n = 7) or normoxia (NOR group, n = 7) over 4 weeks. Before and after training, lactate and glucose turnover rates were measured by infusion of exogenous lactate and stable isotope tracers. Endurance performance was assessed during incremental tests performed in normoxia and hypoxia and a 40 km time trial performed in normoxia. After training, performance was similarly and significantly improved in the NOR and HYP groups (training, P < 0.001) in normoxic conditions. No further effect of hypoxic training was found on markers of endurance performance in hypoxia (training x hypoxia interaction, n.s.). In addition, training and hypoxia had no significant effect on lactate turnover rate. In contrast, there was a significant interaction of training and hypoxia (P < 0.05) on glucose metabolism, as follows: plasma insulin and glucose concentrations were significantly increased; glucose metabolic clearance rate was decreased; and the insulin to glucagon ratio was increased after training in the HYP group. In conclusion, our results show that, compared with training in normoxia, training in hypoxia has no further effect on endurance performance in both normoxic and hypoxic conditions or on lactate metabolic clearance rate. Additionally, these findings suggest that training in hypoxia impairs blood glucose regulation in endurance-trained subjects during exercise.

Hyperglycemia in critical illness: a review

Hyperglycemia is commonplace in the critically ill patient and is associated with worse outcomes. It occurs after severe stress (e.g., infection or injury) and results from a combination of increased secretion of catabolic hormones, increased hepatic gluconeogenesis, and resistance to the peripheral and hepatic actions of insulin. The use of carbohydrate-based feeds, glucose containing solutions, and drugs such as epinephrine may exacerbate the hyperglycemia. Mechanisms by which hyperglycemia cause harm are uncertain. Deranged osmolality and blood flow, intracellular acidosis, and enhanced superoxide production have all been implicated. The net result is derangement of endothelial, immune and coagulation function and an association with neuropathy and myopathy. These changes can be prevented, at least in part, by the use of insulin to maintain normoglycemia.

Glucose metabolism in children: influence of age, fasting, and infectious diseases

This review describes the occurrence of hypoglycemia in young children as a common and serious complication that needs to be avoided because of the high risk of brain damage and mortality. Young age, fasting, and severe infectious disease are considered important risk factors. The limited data on the effect of these risk factors on glucose metabolism in children are discussed and compared with data on glucose metabolism in adults. The observations discussed may have implications for further research on glucose kinetics in young children with infectious disease.

A metabonomic approach to early prognostic evaluation of experimental sepsis by (1)H NMR and pattern recognition

This study proposes an NMR-based metabonomic approach to early prognostic evaluation of sepsis. Forty septic rats receiving cecal ligation and puncture (CLP) were divided into the surviving group and nonsurviving group on day 6, while 20 sham-operated rats served as the control group. Serum samples were collected from septic and sham-operated rats at 12 h after surgery and analyzed using (1)H NMR spectroscopy. Orthogonal partial least squares (OPLS) were applied and showed clustering according to predefined groups, indicating that NMR-based metabolic profiling could reveal pathologic characteristics in the serum of sham-operated, surviving, and nonsurviving septic rats. In addition, six characteristic metabolites including lactate, alanine, acetate, acetoacetate, hydroxybutyrate, and formate, which are mainly involved in energy metabolism, changed markedly in septic rats, especially in the nonsurvivors. Using these metabolites, a predictive model for prognostic evaluation of sepsis was constructed using a radial basis function neural network (RBFNN) with a prediction accuracy of about 87% by test samples. The results indicated that the NMR-based metabonomic approach is a potential technique for the early prognostic evaluation of sepsis.

Hyperglycemic kidney damage in an animal model of prolonged critical illness

Acute kidney injury frequently complicates critical illness and increases mortality; maintaining normoglycemia with insulin has been shown to reduce the incidence of intensive care unit (ICU)-acquired kidney injury. Here we tested the mechanisms by which this intervention might achieve its goal, using a rabbit model of burn-induced prolonged critical illness in which blood glucose and insulin were independently regulated at normal or elevated levels. Hyperglycemia caused elevated plasma creatinine and severe morphological kidney damage that correlated with elevated cortical glucose levels. Renal cortical perfusion and oxygen delivery were lower in hyperglycemic/hyperinsulinemic rabbits, compared to other groups, but this did not explain the elevated creatinine. Mitochondrial respiratory chain activities were severely reduced in the hyperglycemic groups (30-40% residual activity), and were inversely correlated with plasma creatinine and cortical glucose. These activities were much less affected by normoglycemia, and hyperinsulinemia was not directly protective. Mitochondrial damage, evident at day 3, preceded the structural injury evident at 7 days. Our study found that hyperglycemia evoked cellular glucose overload in the kidneys of critically ill rabbits, and this was associated with mitochondrial dysfunction and renal injury. Normoglycemia, independent of insulinemia, protected against this damage.

Tissue-specific glucose toxicity induces mitochondrial damage in a burn injury model of critical illness

OBJECTIVE

In critically ill patients, preventing hyperglycemia (HG) with insulin therapy partially prevented organ dysfunction and protected mitochondria. A study in a rabbit model of critical illness indicated that lower blood glucose level, rather than higher insulinemia, is a key factor in such organ protection. In this model, we now investigated the impact of blood glucose lowering vs. hyperinsulinemia (HI) on mitochondria in relation to organ damage. We assessed whether such effects on mitochondria are mediated indirectly via organ perfusion or directly via reducing cellular glucose toxicity.

DESIGN

Prospective, randomized laboratory investigation.

SETTING

University laboratory.

SUBJECTS

Three-month-old male rabbits.

INTERVENTIONS

After induction of critical illness by burn injury, followed by fluid-resuscitation and parenteral nutrition, rabbits were allocated to four groups, each a combination of normal or elevated blood glucose levels with normal or elevated insulin levels. This required alloxan administration, immediately followed by intravenous insulin and glucose infusions titrated to the respective targets.

MEASUREMENTS AND MAIN RESULTS

In liver, the reduced damage by glucose lowering was not explained by better perfusion/oxygen delivery. Abnormal mitochondrial ultrastructure and function was present in the two hyperglycemic groups, most pronounced with concomitant HI. Affected mitochondrial respiratory chain enzyme activities were reduced to 25% to 62% of values in healthy rabbits, in the presence of up to five-fold increased tissue levels of glucose. This was accompanied by elevated levels of dicarbonyls, which may mediate direct toxicity of cellular glucose overload and accelerated glycolysis. The abnormalities were also present in myocardium, although to a lesser extent, and absent in skeletal muscle.

CONCLUSIONS

In a rabbit model of critical illness, HG evokes cellular glucose overload in liver and myocardium inducing mitochondrial dysfunction, which explained the HG-induced organ damage. Maintenance of normoglycemia, but not HI, protects against such mitochondrial and organ damage.

A high-fructose diet impairs basal and stress-mediated lipid metabolism in healthy male subjects

The effects of a 7 d high-fructose diet (HFrD) or control diet on lipid metabolism were studied in a group of six healthy lean males. Plasma NEFA and β-hydroxybutyrate concentrations, net lipid oxidation (indirect calorimetry) and exogenous lipid oxidation (13CO2production) were monitored in basal conditions, after lipid loading (olive oil labelled with [13C]triolein) and during a standardised mental stress. Lactate clearance and the metabolic effects of an exogenous lactate infusion were also monitored. The HFrD lowered plasma concentrations of NEFA and β-hydroxybutyrate as well as lipid oxidation in both basal and after lipid-loading conditions. In addition, the HFrD blunted the increase in plasma NEFA and exogenous lipid oxidation during mental stress. The HFrD also increased basal lactate concentrations by 31·8 %, and lactate production by 53·8 %, while lactate clearance remained unchanged. Lactate infusion lowered plasma NEFA with the control diet, and net lipid oxidation with both the HFrD and control diet. These results indicate that a 7 d HFrD markedly inhibits lipolysis and lipid oxidation. The HFrD also increases lactate production, and the ensuing increased lactate utilisation may contribute to suppress lipid oxidation.

Type B lactic acidosis and insulin-resistant hyperglycemia in an adolescent following cardiac surgery

OBJECTIVE

To report the presence of type B lactic acidosis and insulin-resistant hyperglycemia following cardiopulmonary bypass in a pediatric patient.

DESIGN

Case report.

SETTING

Tertiary referral children's hospital pediatric intensive care unit.

PATIENT

Fourteen-year-old child with hyperlactatemia and hyperglycemia following cardiac surgery.

INTERVENTIONS AND RESULTS

We report a patient who following cardiopulmonary bypass for repair of his congenital heart disease developed type B lactic acidosis and hyperglycemia resistant to insulin therapy. Resolution of his hyperlactatemia and hyperglycemia occurred approximately 24 hrs postoperatively without apparent ill effect.

CONCLUSIONS

Type B lactic acidosis is a phenomenon that may occur in the pediatric population in conjunction with insulin-resistant hyperglycemia. We observed that its resolution corresponded to improvement in the patient's hyperglycemia.

Caecal ligation and puncture in the rat mimics the pathophysiological changes in human sepsis and causes multi-organ dysfunction

Sepsis is a major clinical challenge that is associated with encephalopathy and multi-organ dysfunction. Current therapeutic interventions are relatively ineffective and the development of novel treatments is hampered by the lack of a well-characterised animal model. Therefore, the behavioural, metabolic, physiological and histological changes resulting from 'through and through' caecal ligation and puncture (CLP) in the rat were investigated to determine its suitability as an animal model of human sepsis. CLP resulted in bacteraemia, characterised by the presence of multiple enteric species within 18-20 h. Locomotor activity was reduced within 4 h of CLP and this reduction increased with time. Pyrexia was evident 4-5 h after CLP and was followed by hypothermia beginning 17 h after intervention. CLP resulted in reduced white blood cell and platelet counts and an increased neutrophil: lymphocyte ratio within 18-20 h. It also resulted in decreased blood glucose, but not lactate levels. CLP caused histopathological changes in the cerebral cortex, liver, lungs and vascular system indicative of multi-organ dysfunction. Therefore, CLP in the rat mimics the cardinal clinical features of human sepsis and the subsequent development of multi-organ dysfunction. It appears to be the best available animal model currently available, in which to investigate the underlying pathophysiology of sepsis and identify therapeutic targets.

Lactate in veterinary critical care: pathophysiology and management

The measurement of blood lactate in people has proven to be a useful tool in the diagnosis, monitoring, and prognosis of a wide range of clinical syndromes. Its use in small animals is increasing, and several studies have been completed that demonstrate its potential role in critical care. This article summarizes the current state of knowledge regarding the physiology and pathophysiology of lactate production and lactic acidosis; current indications and the utility of measurement in a critical care setting are described; novel applications in the evaluation of cavitary effusions are highlighted; and a guide to the therapy of lactic acidosis is presented.

Substrate utilization in sepsis and multiple organ failure

Sepsis and multiple organ failure are characterized by an excessive release of inflammatory mediators and a marked stimulation of stress hormones. These in turn have profound effects on energy and substrate metabolism: energy expenditure is generally increased, and increased lipolysis and fat oxidation are observed. Net protein breakdown occurs and leads to accelerated wasting. Most of these effects can be produced in healthy humans by administration of bacterial endotoxin or by tumor necrosis factor-alpha. Hyperlactatemia is a hallmark of sepsis and critical illness, and its severity is related to mortality. An increased lactate production, possibly secondary to activation of Na-K adenosine 5'-triphosphatase and to muscle mitochondrial dysfunction, is involved. Lactate production by immune cells and wound tissue may also play a role. Long-chain, n-3 polyunsaturated fatty acids have anti-inflammatory effects that may be beneficial in sepsis. They also decrease the stimulation of stress hormones induced by bacterial endotoxin, possibly through an effect exerted at the level of the central nervous sytem. Their use in patients with sepsis does not lead to adverse metabolic effects.

Advances in pathogenesis and management of sepsis

PURPOSE OF REVIEW

The rationale for therapeutic targets in sepsis has arisen from the concept of pathogenesis. This review focuses on recent advances in pathogenesis of sepsis that can aid in management of sepsis patients.

RECENT FINDINGS

Cellular survival in sepsis is related to the magnitude of the stimulus, the stage of the cell cycle and the type of microbe. While phenotypic modification of the endothelium (procoagulant and proadhesive properties, increased endothelial permeability, endothelial apoptosis and changes in vasomotor properties) leads to vasoplegia as a direct correlate to septic shock mortality, phenotypic changes in the epithelium cause activation of the virulence of the opportunistic pathogens and loss of mucosal barrier function, the latter causing a vicious circle in severe sepsis. Early identification of sepsis with protocolized screening, triggering evidence-based protocolized care, is anticipated to reduce sepsis morbidity and mortality. Current treatment of sepsis includes early antibiotic therapy, early aggressive goal-directed resuscitation targeting tissue hypoperfusion, steroids (for refractory shock), activated protein C (for high risk of death) and maintaining support of organ systems.

SUMMARY

A better understanding of pathogenesis of sepsis has led to specific proven management tools that are likely to improve clinical outcome once incorporated into protocolized care.

Hemodynamic monitoring in shock and implications for management. International Consensus Conference, Paris, France, 27-28 April 2006

OBJECTIVE

Shock is a severe syndrome resulting in multiple organ dysfunction and a high mortality rate. The goal of this consensus statement is to provide recommendations regarding the monitoring and management of the critically ill patient with shock.

METHODS

An international consensus conference was held in April 2006 to develop recommendations for hemodynamic monitoring and implications for management of patients with shock. Evidence-based recommendations were developed, after conferring with experts and reviewing the pertinent literature, by a jury of 11 persons representing five critical care societies.

DATA SYNTHESIS

A total of 17 recommendations were developed to provide guidance to intensive care physicians monitoring and caring for the patient with shock. Topics addressed were as follows: (1) What are the epidemiologic and pathophysiologic features of shock in the ICU? (2) Should we monitor preload and fluid responsiveness in shock? (3) How and when should we monitor stroke volume or cardiac output in shock? (4) What markers of the regional and micro-circulation can be monitored, and how can cellular function be assessed in shock? (5) What is the evidence for using hemodynamic monitoring to direct therapy in shock? One of the most important recommendations was that hypotension is not required to define shock, and as a result, importance is assigned to the presence of inadequate tissue perfusion on physical examination. Given the current evidence, the only bio-marker recommended for diagnosis or staging of shock is blood lactate. The jury also recommended against the routine use of (1) the pulmonary artery catheter in shock and (2) static preload measurements used alone to predict fluid responsiveness.

CONCLUSIONS

This consensus statement provides 17 different recommendations pertaining to the monitoring and caring of patients with shock. There were some important questions that could not be fully addressed using an evidence-based approach, and areas needing further research were identified.

Metabolic effects of phosphodiesterase III inhibitors: another reason to promote their use?

Phosphodiesterase III inhibitors combine positive inotropic and vasodilator properties. These inhibitors are therefore frequently used to treat low cardiac output and/or severe left heart failure associated with cardiac surgery. Their effects on energy metabolism and visceral organ function are not well studied, however, particularly in comparison with their 'competitors' in daily practice (that is, catecholamines).

Hyperlactatemia during cardiopulmonary bypass: determinants and impact on postoperative outcome

Introduction

Hyperlactatemia during cardiopulmonary bypass is relatively frequent and is associated with an increased postoperative morbidity. The aim of this study was to determine which perfusion-related factors may be responsible for hyperlactatemia, with specific respect to hemodilution and oxygen delivery, and to verify the clinical impact of hyperlactatemia during cardiopulmonary bypass in terms of postoperative morbidity and mortality rate.

Methods

Five hundred consecutive patients undergoing cardiac surgery with cardiopulmonary bypass were admitted to this prospective observational study. During cardiopulmonary bypass, serial arterial blood gas analyses with blood lactate and glucose determinations were obtained. Hyperlactatemia was defined as a peak arterial blood lactate concentration exceeding 3 mmol/l. Pre- and intraoperative factors were tested for independent association with the peak arterial lactate concentration and hyperlactatemia. The postoperative outcome of patients with or without hyperlactatemia was compared.

Results

Factors independently associated with hyperlactatemia were the preoperative serum creatinine value, the presence of active endocarditis, the cardiopulmonary bypass duration, the lowest oxygen delivery during cardiopulmonary bypass, and the peak blood glucose level. Once corrected for other explanatory variables, hyperlactatemia during cardiopulmonary bypass remained significantly associated with an increased morbidity, related mainly to a postoperative low cardiac output syndrome, but not to mortality.

Conclusion

Hyperlactatemia during cardiopulmonary bypass appears to be related mainly to a condition of insufficient oxygen delivery (type A hyperlactatemia). During cardiopulmonary bypass, a careful coupling of pump flow and arterial oxygen content therefore seems mandatory to guarantee a sufficient oxygen supply to the peripheral tissues.

Effect of nutritional support on glucose control

PURPOSE OF REVIEW

There is evidence that maintaining a normal glycemia level in critically ill patients has beneficial effects on outcome. Strategies aimed at lowering glycemia are based on the understanding of mechanisms regulating glucose metabolism.

RECENT FINDINGS

Activation of AMP protein kinase in skeletal muscle and in the liver leads to a reduction in glucose production, a stimulation of glucose uptake, and a lowering of glycemia. These mechanisms appear to be activated during exercise, or by the endogenous adipokine adiponectin. Alterations in adiponectin concentrations during critical illness may thus play a role in the metabolic stress responses. In addition, AMP-activated protein kinase is the target for drugs (metformin, thazolidinediones), which may be of interest in the intensive care unit. Besides insulin, plasma glucose concentrations may be lowered by hypocaloric feeding, or by feeding 'diabetic' formula with low glucose content and supplemented with fructose. Whether such approaches lead to beneficial effects comparable to those observed with insulin remains to be established.

SUMMARY

Recent findings regarding the molecular mechanisms underlying glucose transport and metabolism are summarized, and potential strategies other than insulin are outlined which may contribute to lowering glycemia in critically ill patients.

Lactate and shock state: the metabolic view

PURPOSE OF REVIEW

The conventional view in severe sepsis or septic shock is that most of the lactate that accumulates in the circulation is due to cellular hypoxia and the onset of anaerobic glycolysis. A number of papers have suggested that lactate formation during sepsis is not due to hypoxia. I discuss this hypothesis and outline the recent advances in the understanding of lactate metabolism in shock.

RECENT FINDINGS

Numerous experimental data have demonstrated that stimulation of aerobic glycolysis - that is, glycolysis not attributable to oxygen deficiency - and glycogenolysis occurs not only in resting, well-oxygenated skeletal muscles but also during experimental haemorrhagic shock and experimental sepsis, and is closely linked to stimulation of sarcolemmal Na+/K+ -ATPase under epinephrine stimulation. A human study of hyperkinetic septic shock demonstrated that skeletal muscle is a leading source of lactate production by exaggerated aerobic glycolysis through Na+/K+ -ATPase stimulation.

SUMMARY

There is increasing evidence that sepsis is accompanied by a hypermetabolic state, with enhanced glycolysis and hyperlactataemia. This should not be rigorously interpreted as an indication of hypoxia. It now appears, at least in the hyperkinetic state, that increased lactate production and concentration as a result of hypoxia are often the exception rather than the rule.

Human malarial disease: a consequence of inflammatory cytokine release

Malaria causes an acute systemic human disease that bears many similarities, both clinically and mechanistically, to those caused by bacteria, rickettsia, and viruses. Over the past few decades, a literature has emerged that argues for most of the pathology seen in all of these infectious diseases being explained by activation of the inflammatory system, with the balance between the pro and anti-inflammatory cytokines being tipped towards the onset of systemic inflammation. Although not often expressed in energy terms, there is, when reduced to biochemical essentials, wide agreement that infection with falciparum malaria is often fatal because mitochondria are unable to generate enough ATP to maintain normal cellular function. Most, however, would contend that this largely occurs because sequestered parasitized red cells prevent sufficient oxygen getting to where it is needed. This review considers the evidence that an equally or more important way ATP deficiency arises in malaria, as well as these other infectious diseases, is an inability of mitochondria, through the effects of inflammatory cytokines on their function, to utilise available oxygen. This activity of these cytokines, plus their capacity to control the pathways through which oxygen supply to mitochondria are restricted (particularly through directing sequestration and driving anaemia), combine to make falciparum malaria primarily an inflammatory cytokine-driven disease.

Is pyruvate an endogenous anti-inflammatory molecule?

Pyruvic acid is an effective scavenger of reactive oxygen species. Ethyl pyruvate has demonstrated anti-inflammatory actions and improved hyperpermeability and bacterial translocation due to endotoxemia and is of benefit in animal models of sepsis and septic shock. Ethyl pyruvate specifically inhibits tumor necrosis factor-alpha production and decreases circulating levels of high-mobility group box-1 and nuclear factor-kappaB signaling pathways by specifically targeting its p65 subunit in animals with established endotoxemia or sepsis and in macrophage cultures. Ethyl pyruvate also decreases cyclo-oxygenase-2, inducible nitric oxide synthase, and interleukin-6 mRNA expression in the liver, ileal mucosa, and colonic mucosa in animal models with hemorrhagic shock. Similar beneficial actions have been seen in endotoxemia. These and other studies suggest that ethyl pyruvate could be of significant benefit in the treatment of patients who are critically ill and have sepsis/septic shock.