Lactate Metabolism

NDP-MSH treatment recovers marginal lungs during ex vivo lung perfusion (EVLP)

The increasing use of marginal lungs for transplantation encourages novel approaches to improve graft quality. Melanocortins and their receptors (MCRs) exert multiple beneficial effects in pulmonary inflammation. We tested the idea that treatment with the synthetic α-melanocyte-stimulating hormone analogue [Nle4,D-Phe7]-α-MSH (NDP-MSH) during ex vivo lung perfusion (EVLP) could exert positive influences in lungs exposed to different injuries. Rats were assigned to one of the following protocols (N = 10 each): 1) ischemia/reperfusion (IR) or 2) cardiac death (CD) followed by ex vivo perfusion. NDP-MSH treatment was performed in five rats of each protocol before lung procurement and during EVLP. Pulmonary function and perfusate concentration of gases, electrolytes, metabolites, nitric-oxide, mediators, and cells were assessed throughout EVLP. ATP content and specific MCR expression were investigated in perfused lungs and in biopsies collected from rats in resting conditions (Native, N = 5). NDP-MSH reduced the release of inflammatory mediators in perfusates of both the IR and the CD groups. Treatment was likewise associated with a lesser amount of leukocytes (IR: p = 0.034; CD: p = 0.002) and reduced lactate production (IR: p = 0.010; CD: p = 0.008). In lungs exposed to IR injury, the NDP-MSH group showed increased ATP content (p = 0.040) compared to controls. In CD lungs, a significant improvement of vascular (p = 0.002) and airway (Ppeak: p < 0.001, compliance: p < 0.050, pO2: p < 0.001) parameters was observed. Finally, the expression of MC1R and MC5R was detected in both native and ex vivo-perfused lungs. The results indicate that NDP-MSH administration preserves lung function through broad positive effects on multiple pathways and suggest that exploitation of the melanocortin system during EVLP could improve reconditioning of marginal lungs before transplantation.

Functional, Metabolic and Morphologic Results of Ex Vivo Donor Lung Perfusion with a Perfluorocarbon-Based Oxygen Carrier Nanoemulsion in a Large Animal Transplantation Model

Background: Ex vivo lung perfusion (EVLP) is a technology that allows the re-evaluation of questionable donor lung before implantation and it has the potential to repair injured donor lungs that are otherwise unsuitable for transplantation. We hypothesized that perfluorocarbon-based oxygen carrier, a novel reconditioning strategy instilled during EVLP would improve graft function. Methods: We utilized perfluorocarbon-based oxygen carrier (PFCOC) during EVLP to recondition and improve lung graft function in a pig model of EVLP and lung transplantation. Lungs were retrieved and stored for 24 h at 4 °C. EVLP was done for 6 h with or without PFCOC. In the transplantation groups, left lung transplantation was done after EVLP with or without PFCOC. Allograft function was assessed by means of pulmonary gas exchange, lung mechanics and vascular pressures, histology and transmission electron microscopy (TEM). Results: In the EVLP only groups, physiological and biochemical markers during the 6-h perfusion period were comparable. However, perfusate lactate potassium levels were lower and ATP levels were higher in the PFCOC group. Radiologic assessment revealed significantly more lung infiltrates in the controls than in the PFCOC group (p = 0.04). In transplantation groups, perfusate glucose consumption was higher in the control group. Lactate levels were significantly lower in the PFCOC group (p = 0.02). Perfusate flavin mononucleotide (FMN) was significantly higher in the controls (p = 0.008). Post-transplant gas exchange was significantly better during the 4-h reperfusion period in the PFCOC group (p = 0.01). Plasma IL-8 and IL-12 levels were significantly lower in the PFCOC group (p = 0.01, p = 0.03, respectively). ATP lung tissue levels at the end of the transplantation were higher and myeloperoxidase (MPO) levels in lung tissue were lower in the PFCOC group compared to the control group. In the PFCOC group, TEM showed better tissue preservation and cellular viability. Conclusion: PFCOC application is safe during EVLP in lungs preserved 24 h at 4 °C. Although this strategy did not significantly affect the EVLP physiology, metabolic markers of the donor quality such as lactate production, glucose consumption, neutrophil infiltration and preservation of mitochondrial function were better in the PFCOC group. Following transplantation, PFCOC resulted in better graft function and TEM showed better tissue preservation, cellular viability and improved gas transport.

Acid-Base, Electrolyte and Lactate Abnormalities as Well as Gastric Necrosis and Survival in Dogs With Gastric Dilation-Volvulus Syndrome. A Retrospective Study in 75 Dogs

Gastric dilation-volvulus (GDV) syndrome in dogs is associated with complex metabolic, acid-base, and electrolyte abnormalities. The aim of this study was to evaluate previously analyzed factors (lactate and BE) in combination with other acid-base parameters (pH, pCO₂, bicarbonate, base excess [BE], anion gap [AG], and strong ion difference) and electrolyte concentrations and to evaluate their association with the incidence of gastric necrosis and outcome in dogs with GDV. A retrospective study in 75 dogs with gastric dilation-volvulus syndrome, University veterinary teaching hospital. Medical records were reviewed including signalment, history, initial plasma lactate, acid-base parameters, and electrolyte concentrations, surgical findings and outcome. The overall mortality was 18.7%. In dogs with gastric necrosis, higher initial plasma lactate (median 5.84 vs. 3.36 mmol/L) and AG (20.7 vs. 16.55 mmol/L) and lower pH (7.29 vs. 7.36), bicarbonate (18.7 vs. 22.9 mmol/L), and BE concentration (-8.1 vs. -1.85 mmol/L) were found compared to dogs without gastric necrosis. Anorganic phosphorus was the only electrolyte investigated for which a significant difference was noted between dogs with and without gastric necrosis (1.93 vs. 1.39 mmol/L). The initial plasma lactate concentration (3.36 mmol/L vs. 9.68 mmol/L) and AG (16.8 vs. 20.95 mmol/L) were lower in survivors than nonsurvivors. Survivors had higher pH (7.35 vs. 7.27), bicarbonate concentrations (22.9 vs. 17.35 mmol/L), and BE (-1.9 vs. -9.55 mmol/L) compared to nonsurvivors. Anorganic phosphorus was ultimately the only electrolyte with a significant difference between survivors and nonsurvivors (1.4 vs. 1.84 mmol/L). A multivariate logistic regression model of combination lactate, pH, bicarbonate, BE, AG, and anorganic phosphorus identified pH ≤7.331 and bicarbonate as factors independently associated with gastric necrosis. Similarly, pH ˃7.331, bicarbonate and anorganic phosphorus were independently associated with outcome. Higher initial plasma lactate, AG and anorganic phosphorus levels, and lower pH, BE and bicarbonate concentrations were found in GDV dogs with gastric necrosis. Similarly, initially higher plasma lactate, AG and anorganic phosphorus concentrations, and lower pH, BE and bicarbonate were found in GDV dogs who required euthanasia or who died after surgery. Of these parameters, pH and bicarbonate were strongly and independently associated with gastric necrosis, and pH, bicarbonate and phosphorus were independently associated with outcome.

Lactate determination in pleural and abdominal effusions: a quick diagnostic marker of exudate-a pilot study

Pleural or abdominal effusions are frequent findings in ICU and Internal Medicine patients. Diagnostic gold standard to distinguish between transudate and exudate is represented by "Light's Criteria," but, unfortunately, the chemical-physical examination for their calculation is not a rapid test. Pursuing an acid-base assessment of the fluid by a blood-gas analyzer, an increase of lactate beyond the normal serum range is reported in the exudative effusions. The advantages of this test are that it is a very fast bed-side test, executable directly by the physician. The aim of this study is to evaluate whether the increase in lactate in pleural and abdominal effusions might be used as a criterion for the differential diagnosis of the nature of the fluid. Sixty-nine patients with pleural or abdominal effusions and clinical indication for thoracentesis or paracentesis were enrolled. Acid-base assessment with lactate, total protein, and LDH dosage on the serum, and acid-base assessment with lactate, total protein, and LDH dosage, cytology, and bacterial culture on the fluid were performed to each patient. Fluid-blood lactate difference (ΔLacFB) and fluid-blood lactate ratio (LacFB ratio) were calculated. A statistical analysis was carried out for fluid lactate (LacF), ΔLacFB, and LacFB ratio, performing ROC curves to find the cut-off values with best sensitivity (Sn) and specificity (Sp) predicting an exudate diagnosis: LacF: cut-off value: 2.4 mmol/L; AU-ROC 0.854 95% CI 0.756-0.952; Sn 0.77; Sp 0.84. ΔLacFB: cut-off value: 0.95 mmol/L; Au-ROC 0.876 95% CI 0.785-0.966; Sn 0.80; Sp 0.92. LacFB ratio: cut-off value: 2 mmol/L; Au-ROC 0.730 95% CI 0.609-0.851; Sn 0.74; Sp 0.65. Lactate dosage by blood-gas analyzer on pleural and abdominal effusions seems to be a promising tool to predict a diagnosis of exudate.

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.

Systematic review regarding metabolic profiling for improved pathophysiological understanding of disease and outcome prediction in respiratory infections

Metabolic profiling through targeted quantification of a predefined subset of metabolites, performed by mass spectrometric analytical techniques, allows detailed investigation of biological pathways and thus may provide information about the interaction of different organic systems, ultimately improving understanding of disease risk and prognosis in a variety of diseases. Early risk assessment, in turn, may improve patient management in regard to cite-of-care decisions and treatment modalities. Within this review, we focus on the potential of metabolic profiling to improve our pathophysiological understanding of disease and management of patients. We focus thereby on lower respiratory tract infections (LRTI) including community-acquired pneumonia (CAP) and chronic obstructive pulmonary disease (COPD), an important disease responsible for high mortality, morbidity and costs worldwide. Observational data from numerous clinical and experimental studies have provided convincing data linking metabolic blood biomarkers such as lactate, glucose or cortisol to patient outcomes. Also, identified through metabolomic studies, novel innovative metabolic markers such as steroid hormones, biogenic amines, members of the oxidative status, sphingo- and glycerophospholipids, and trimethylamine-N-oxide (TMAO) have shown promising results. Since many uncertainties remain in predicting mortality in these patients, further prospective and retrospective observational studies are needed to uncover metabolic pathways responsible for mortality associated with LRTI. Improved understanding of outcome-specific metabolite signatures in LRTIs may optimize patient management strategies, provide potential new targets for future individual therapy, and thereby improve patients' chances for survival.

Transient occult cardiotoxicity in children receiving continuous beta-agonist therapy

BACKGROUND

Continuous beta-agonist therapy, typically in the form of inhaled albuterol, is the first line therapy for the treatment of acute and severe bronchospasm in children. Although this treatment is commonly used, concerns about cardiotoxicity have been raised. We aimed to investigate the cardiotoxic effects of continuous beta-agonist therapy in children.

METHODS

We conducted a retrospective review of children admitted to the intensive care unit (ICU) between May 2008 and April 2009, who were treated with continuous beta-agonist therapy (intravenous and nebulized).

RESULTS

Twenty of the 36 children treated with continuous albuterol had repeated serum troponin-T and lactate levels measured. Eleven patients (55%) were also treated with continuous intravenous terbutaline. Elevated levels of troponin-T levels were found in 25% of children, and elevated lactate levels were found in 60%. However, all returned to normal levels within 48 hours of ICU admission, despite continued beta-agonist therapy. No children experienced arrhythmias during therapy. There was no association between intravenous terbutaline use and elevated troponin-T [odds ratio (OR), 1.3; 95% CI, 0.2-10.3] or with elevated serum lactate (OR, 0.6; 95% CI, 0.1-3.7). There was also no association between elevated troponin-T or lactate and ICU or hospital length of stay.

CONCLUSIONS

In this small study, a significant proportion of children had elevated serum troponin-T and lactate levels while receiving inhaled continuous beta-agonist therapy, irrespective of intravenous therapy. However, these abnormal values all returned to normal within 48 hours of ICU admission and were not associated with increased duration of hospitalization.

Plasma lactate concentration as a prognostic biomarker in dogs with gastric dilation and volvulus

Initial and serial plasma lactate concentrations can be used to guide decision making in individual dogs with GDV but care is necessary in phrasing conversations with owners. Published data suggests that survival is more likely and the chance of complications less in dogs with an initial plasma lactate of <4 mmol/L. An initial lactate >6 mmol/L makes gastric necrosis and greater expense more likely. However, because of the overlap between groups and the good overall survival rates, exploratory laparotomy should always be recommended irrespective of the plasma lactate concentration. Falls in plasma lactate of greater than ~40% after fluid resuscitation are likely to indicate better survival. If the initial plasma lactate concentration is moderately to severely increased (5->10 mmol/L) and a sustained increase in plasma lactate occurs after fluid resuscitation, the cause should be aggressively pursued. Many dogs with persistent hyperlactatemia over 24-48 hours do not survive.

Plasma lactate concentration as an indicator of plasma caffeine concentration in acute caffeine poisoning

Aim

Severe caffeine poisoning is rare, but is associated with high mortality. Plasma caffeine concentration is one of the indications of treatment of caffeine poisoning; however, it is not easily measured at most emergency departments. If the plasma lactate concentration and the plasma caffeine concentration were correlated, the plasma lactate concentration may be an indication of caffeine poisoning. In this study, we investigated the correlation between the plasma lactate concentration and the plasma caffeine concentration.

Methods

From April 2010 to March 2012, 18 patients with severe caffeine poisoning by overdose were admitted at our Emergency Center. The plasma lactate concentration and plasma caffeine concentration of 10 patients were determined at the same time at 12-24 h after admission. These findings were plotted and we analyzed the correlation and trends in these concentrations.

Results

There were strong correlations between the plasma lactate concentration and the plasma caffeine concentration at admission (n = 18) and at 12-24 h after admission (n = 10) (correlation coefficients, 0.95 and 0.91, respectively). There was a strong positive correlation between the trend of the plasma lactate concentration and the plasma caffeine concentration (n = 10). The correlation coefficient was 0.91.

Conclusion

These results are extremely beneficial for emergency department clinical physicians because such findings permit the determination of the severe caffeine poisoning patient. Additionally, the plasma lactate concentration might be one of the indicators of hospitalization and discharge.

Evaluation of hypercoagulability using soluble fibrin monomer complex in sick newborns

BACKGROUND

Soluble fibrin monomer complex (SFMC) and fibrin monomer (FM) are well known as markers for hypercoagulability, but such measurements have not been investigated in detail for the neonate. To identify the presence of a hypercoagulable state in sick newborns, the behavior of SFMC with special reference to those of other coagulation tests, and the relationships with other parameters of blood coagulation as well as lactate, which is considered to be the gold standard for assessing tissue hypoxia, were studied.

METHODS

Records of 216 sick newborns, who had undergone blood coagulation tests, were retrospectively studied based on their medical records.

RESULTS

SFMC had a significant correlation with d-dimer in infants with birthweight <1500 g, but no correlation was observed with prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, anti-thrombin or platelet count. In contrast, in infants with birthweight ≥ 1500 g, SFMC was correlated with PT, APTT, fibrinogen, and d-dimer, but no correlation was observed with anti-thrombin or platelet count. In addition, SFMC was significantly higher in the high lactate group (lactate ≥ 4 mmol/L), compared with the low lactate group (<4 mmol/L).

CONCLUSION

Measurement of blood SFMC is useful to monitor hypercoagulable state in sick newborns with hypoxia.

Point of care serum lactate levels as a prognostic marker of outcome in complex pediatric cardiac surgery patients: Can we utilize it?

BACKGROUND

Post-operative course after complex pediatric cardiac surgery is unpredictable. Although, change in arterial lactate levels has been used as a surrogate marker for many years, scientific evidence correlating the early perioperative lactate levels with outcome is still lacking.

OBJECTIVE

To evaluate the trends in lactate levels from intraoperative period to an extended post-operative period in pediatric intensive care unit (PICU) and to assess its usefulness as a prognostic marker.

DESIGN

Prospective observational study.

SETTING

Tertiary pediatric cardiac surgical unit.

PATIENTS

Thirty-five non-consecutive children aged 1-140 months who underwent surgery for congenital heart diseases (CHD) on cardiopulmonary bypass (CPB).

INTERVENTION

None.

MATERIALS AND METHODS

ARTERIAL BLOOD LACTATE LEVELS WERE OBTAINED AT THE FOLLOWING TIME POINTS: After induction of anesthesia, 15 and 45 min after institution of CPB, at the start of rewarming, after sternotomy closure, then at 1, 6, 24, and 48 h in PICU. Other hemodynamic and clinical variables, CPB variables, blood gas values, and laboratory variables were also recorded.

RESULTS

Four patients died out of 35 patients (11.4%). Non-survivors showed significant persistent elevation in lactates (>4.0 mmol/l). Peak lactates correlate significantly with longer aortic cross clamp time, CPB duration, ventilation hours and PICU stay.

CONCLUSION

Early point of care lactate can be a useful prognostic marker in post-cardiac surgery patients in adjunct with other parameters measured in PICU. This reiterates the importance of measuring lactates and timely recognition of at-risk patients, which on early intervention can help in reducing post-operative morbidity and mortality.

Effect of transfusion on the venous blood lactate level in very low-birthweight infants

BACKGROUND

In recent years the blood lactate level can be easily and quickly measured with a small amount of blood, and the availability of an arterial blood lactate level has been reported as an indicator of oxygen deficit in adults. To determine whether venous blood lactate level can serve as such a marker for determining the indications for transfusion, blood lactate and hemoglobin level were monitored before and after transfusion.

METHODS

The study subjects consisted of 12 very low-birthweight infants admitted to the neonatal intensive care unit and who had transfusion between June 2005 and June 2007. The data on the blood lactate and hemoglobin were collected retrospectively by referring to the clinical records.

RESULTS

A total of 18 transfusions was performed. There was no significant relationship between venous blood lactate and hemoglobin concentration before transfusion. The subjects were classified into two groups according to the lactate level before transfusion: > or =3.3 mmol/L and <3.3 mmol/L. In the high-lactate group the lactate decreased significantly after transfusion (P < 0.01) and it continued to decrease thereafter. In the low-lactate group, however, the lactate remained unchanged.

CONCLUSIONS

Venous blood lactate measurements may offer some additional information regarding the optimal time for performing a transfusion. To the authors' knowledge this is the first report to study the changes in lactate levels using venous blood sampling in red blood cell transfusion in very low-birthweight infants.

Serial lactate measurements using microdialysis of interstitial fluid do not correlate with plasma lactate in children after cardiac surgery

OBJECTIVES

Serial postoperative blood lactate (BL) concentrations have been shown to predict outcome of children after congenital heart surgery (CHS), and interventions aimed at lowering lactate can improve the outcome of these children. The cumulative blood loss for diagnostic purposes, such as repetitive arterial blood sampling in the intensive care unit, contributes, especially in small children, to anemia. Techniques to limit blood loss can therefore be of use. Microdialysis is a technique to monitor tissue chemistry in various clinical settings, and we hypothesized that it may be a valuable alternative for frequent blood sampling to monitor lactate in children after CHS.

METHODS

Fifteen children with a mean age of 40 months (range, 4-118 months) were prospectively enrolled after CHS. A CMA double lumen microdialysis catheter was inserted into the subcutaneous adipose tissue of the abdominal wall and infused with an isotone mannitol 5% solution at 1 microL/min via the inlet tubing. Microdialysate fluid was collected every hour for 48 hrs and stored at -80 degrees C for lactate determination (interstitial fluid lactate, IFL). Every hour arterial blood was taken for lactate determination. Individual profiles, correlation coefficient, and Bland-Altman analysis were used to compare BL and IFL results.

RESULTS

There were no complications with the microdialysis technique. All patients were discharged alive from hospital. Six hundred twenty paired samples were analyzed. Mean recovery of microdialysate fluid was 84%. Median (interquartile range) was 0.95 (0.70-1.15) mmol/L for BL and 1.13 (0.86-1.48) mmol/L for IFL (p < 0.0001). Individual profiles showed that IFL follows changes in BL in some, but not all children. With this study, we could not explain this discrepancy. The correlation between BL and IFL was poor (r = .77 (p < 0.0001) r = .59). Bland-Altman analysis confirmed the insufficient performance of the current microdialysis-based procedure compared with BL.

CONCLUSION

Serial lactate measurements in microdialysis fluid of subcutaneous adipose tissue are feasible, but cannot be used as a reliable interchangeable method for plasma lactate analysis in children after CHS at this time. Whether this technique has its own place in the assessment of the overall hemodynamic status and tissue perfusion in children after CHS needs to be addressed in future studies.

Serum Lactate Level Has Prognostic Significance After Pediatric Cardiac Surgery

OBJECTIVE

The determination of postoperative course after cardiac surgery has always been a challenging issue. It is more sophisticated in the pediatric age group. The aim of this investigation was to identify whether increased concentrations of lactate in arterial blood has a predictive value for postoperative morbidity and mortality after heart surgery.

METHODS

From May 2002 to June 2003, 60 infants operated on at the authors' institution were included in this prospective study. The patients were divided into 2 groups according to their respective postoperative serum lactate values. After the stabilization period in the intensive care unit (first 3 hours postoperatively), samples for serum lactate were obtained from arterial blood at 3 (t1), 6 (t2), and 12 hours (t3) postoperatively. The patients were subdivided into 2 groups according to their respective mean serum lactate values. A value of 4.8 mmol/L (3 times the normal upper limit) was chosen as a threshold for serum lactate. The patients with a mean value of greater than 4.8 mmol/L (group 1) were compared with the remaining group of patients (group 2). The relationship between serum mean lactate level and intraoperative and postoperative clinical variables was evaluated.

RESULTS

Among the patients in this study, 26 (43.3%) had a serum mean lactate level more than 4.8 mmol/L and 34 (56.7%) had a level of 4.8 mmol/L or less. Age, aortic cross-clamping time, cardiopulmonary bypass time, and the lowest hematocrit during cardiopulmonary bypass were significant variables that influenced the postoperative serum mean lactate level. Six patients died in the postoperative period and 54 infants survived. The hospital mortality was significantly higher in group 1 than in group 2 (19.0% v 2.9%; p = 0.037, kappa = 0.179). Multivariate analysis revealed that serum mean lactate level correlated significantly with inotrope score, intubation time, and intensive care unit stay.

CONCLUSIONS

Blood lactate concentration of 4.8 mmol/L or higher during the early postoperative hours identifies a group of patients with increased risk of postoperative morbidity and mortality.

Relationship between injury severity and lactate levels in severely injured patients

OBJECTIVE

To determine the correlation of blood concentration of lactate and severity of injury and survival in severely injured patients.

DESIGN AND SETTING

A prospective study of severely injured patients admitted directly from an emergency surgical unit to a surgical intensive care unit with an Injury Severity Score (ISS) of 16 points or more. The study was conducted over 30 months.

PATIENTS

98 severely injured subjects aged between 16 and 82 years with ISS range from 16 to 75 points, overall 25.5% mortality.

INTERVENTIONS

Blood lactate concentrations were measured once on admission, twice daily during the first 2 days and once daily during the next 3 days. ISS, Revised Trauma Score, Shock Index, and Trauma and Injury Severity Score were calculated for each subject.

MEASUREMENTS AND RESULTS

Of 98 severely injured patients 91 had elevated blood lactate concentration (over 2.0 mmol/l). Regression analyses demonstrated that injury severity, as measured by ISS, can be predicted from lactate concentration on admission, while survival, either actual or predicted by Trauma and Injury Severity Score higher than 0.5, can be predicted from lactate concentration after 12 h. We also found that patients with Shock Index higher than 0.9 had significantly higher lactate levels during the first 36 h than those with values less than 0.9.

CONCLUSIONS

This study confirmed the relationship between blood lactate levels and injury severity as well as the prognostic value of blood lactate level for survival of severely injured patients.

Comparison of lactate or BE during out-of-hospital cardiac arrest to determine metabolic acidosis

During cardiopulmonary resuscitation, pH and base excess (BE) decrease to a variable degree due to metabolic acidosis. The main cause has been shown to be lactate, which cannot be eliminated sufficiently because of low perfusion during cardiac massage. Both BE and lactate can be measured in the prehospital phase. The aim of the study was to determine if BE and lactate are comparable variables during cardiopulmonary resuscitation (CPR) and if the measurement of lactate level alone would be sufficient to determine the patient's metabolic status and sufficiently reliable to determine the administration of buffer solutions. During the observation period, we registered 31 patients (21 males, ten females) who were resuscitated according to European Resuscitation Council recommendations, who had blood gas analysis and lactate levels measured in blood taken by arterial puncture or arterial line. The first measurement from each patient was taken after primary resuscitation (within 5-20 min). The mean lactate level was 9.85+/-2.98 (range, 4.1-18.7) mmol/l, and the mean BE was -15.0+/-5.98 (range, 5.5 to -24.3). There were statistically significant correlations between the lactate level and BE and pH (linear correlation, r=-0.673, P<0,001 and r=-0,683, P<0,001, respectively), but not with pO2 and pCO2. The receiver-operated curve analysis showed that a cut-off point of 7.0 mmol/l lactate indicates a BE below -10 with a sensitivity of 96% and a specificity of 67%. Lactate measurement is a valuable tool to determine metabolic acidosis during CPR and may be able to replace blood gas analysis in this situation.

Effects of bicarbonate- and lactate-buffered replacement fluids on cardiovascular outcome in CVVH patients

BACKGROUND

Bicarbonate-buffered replacement fluid (RF-bic) in continuous venovenous hemofiltration (CVVH) may be superior to lactate-buffered replacement fluid (RF-lac) in acute renal failure. In an open, randomized, multicenter study, we investigated the effects of RF-bic and RF-lac on cardiovascular outcome in patients requiring CVVH following acute renal failure.

METHODS

One hundred seventeen patients between the age of 18 and 80 years were randomized to CVVH either with RF-bic (N = 61) or RF-lac (N = 56). Patients were treated with CVVH for five days or until either renal function was restored or the patient was removed from the study. Data were analyzed on day 5 or according to the "last observation carried forward" (LOCF) option. Adverse events were classified according to the WHO-Adverse Reaction Terminology system.

RESULTS

Blood lactate levels were significantly lower and blood bicarbonate levels were significantly higher in patients treated with RF-bic than in those treated with RF-lac (lactate, 17.4 +/- 8.5 vs. 28.7 +/- 10.4 mg/dL, P < 0.05; bicarbonate, 23.7 +/- 0.4 vs. 21.8 +/- 0.5 mmol/L, P < 0. 01). The number of hypotensive crises was lower in RF-bic-treated patients than in RF-lac-treated patients (RF-bic 14 out of 61 patients, RF-lac in 29 out of 56 patients; 0.26 +/- 0.09 vs. 0.60 +/- 0.31 episodes per 24 h, P < 0.05). Nine out of 61 patients (15%) treated with RF-bic and 21 out of 56 patients (38%) treated with RF-lac developed cardiovascular events during CVVH therapy (P < 0. 01). A multiple regression analysis showed that the occurrence of cardiovascular events was dependent on replacement fluid and previous cardiovascular disease and not on age or blood pressure. Patients with cardiac failure died less frequently in the group treated with RF-bic (7 out of 24, 29%) than in the group treated with RF-lac (12 out of 21, 57%, P = 0.058). In patients with septic shock, lethality was comparable in both groups (RF-bic, 10 out of 27, 37%; RF-lac, 7 out of 20, 35%, P = NS).

CONCLUSIONS

The results show that the administration of RF-bic solution was superior in normalizing acidosis of patients without the risk of alkalosis. The data also suggest that the use of RF-bic during CVVH reduces cardiovascular events in critically ill patients with acute renal failure, particularly those with previous cardiovascular disease or heart failure.

Effects of crystalloid solutions on circulating lactate concentrations: Part 1. Implications for the proper handling of blood specimens obtained from critically ill patients

OBJECTIVES

a) To test the hypothesis that circulating lactate concentrations are the same in simultaneously collected arterial and central venous blood specimens; b) to test the hypothesis that even small amounts of crystalloid solutions, which are inadequately "cleared" from these indwelling arterial and venous catheters, can lead to clinically important and misleading changes in the measured lactate values.

DESIGN

A prospective, multiexperiment study.

SETTING

A critical care research laboratory and a 20-bed intensive care unit (ICU).

PATIENTS

Three hundred fifty-five patients.

INTERVENTIONS

Blood samples were collected.

MEASUREMENTS AND MAIN RESULTS

Experiment 1: Simultaneously collected arterial and central venous blood specimens were obtained on 148 occasions from 48 medical ICU patients receiving no lactated Ringer's solution (RL). Arterial and central venous lactate values were nearly identical in these patients. The correlation between the arterial and central venous lactate concentrations was excellent (r2 = .85; p < .0001) and the agreement between the arterial and central venous lactate concentrations was also excellent (bias and precision = 0.04 mmol/L and +/- 0.38 mmol/L, respectively). Experiment 2: Arterial and mixed venous blood samples were obtained from 100 percutaneous transluminal coronary angioplasty (PTCA) and 75 cardiac surgical patients immediately before the performance of these cardiac procedures. We found the central venous lactate concentrations to be higher than arterial lactate values in the cardiac surgical group, and there was a very poor correlation (r2 = .07) between arterial and central venous lactate values in the cardiac surgical group. The correlation between central venous and arterial lactate concentrations in the PTCA patients was excellent (r2 = .84) and similar to the findings of experiment 1. Since the cardiac surgical patients received RL and the PTCA patients received no RL, we speculated that the intravenous infusion of RL in the cardiac surgical group accounted for these discordant findings. To test this speculation, we performed experiments 3 and 4. Experiment 3: In a large bench study, blood specimens were divided into multiple 1-mL aliquot portions, to which 0.01, 0.05, 0.10, 0.50, or 1.0 mL of various crystalloid solutions, containing or not containing RL, were added. In a volume-dependent and linear manner, solutions containing RL increased the circulating lactate concentration from 10% to > 400% of the baseline lactate value. In a volume-dependent and linear fashion, the non-RL crystalloid solutions decreased the lactate concentration by 0 to 66% of the baseline nondiluted lactate concentration. Experiment 4: In 30 different cardiac surgical patients, we simultaneously obtained central venous and arterial blood specimens. Patients this time received no RL, and catheter lines were adequately cleared (removal > 5 mL) of crystalloid solutions. We found a correlation (r2 = .82; p < .0001) that was virtually identical to the findings of experiment 1 and to the findings in the PTCA group of experiment 2.

CONCLUSIONS

a) Arterial and central venous lactate concentrations are similar in hemodynamically stable critically ill patients, b) Even small amounts of RL-containing solutions in catheters used for blood sampling may cause false increases in the circulating lactate concentration. c) Even small amounts of non-RL crystalloid solutions in catheters used for blood sampling may falsely decrease circulating lactate values. d) When blood specimens are drawn from indwelling catheters, all crystalloid solutions must be cleared from the line.

Serum lactates correlate with mortality after operations for complex congenital heart disease

BACKGROUND

The objective of this study was to determine whether serum lactate levels predict mortality in children less than 1 year of age who have undergone cardiopulmonary bypass and operations for complex congenital heart disease.

METHODS

The initial lactate, maximum lactate, and lactate levels at 4 to 6 hours after operation were analyzed for each of 48 children less than 12 months of age who underwent cardiopulmonary bypass.

RESULTS

Data were analyzed for the 6 patients who died and the 42 patients who survived. For the patients who died, the initial postoperative serum lactate, maximum lactate, and 4- to 6-hour lactate levels were significantly higher than those in the patients who survived. All patients with an initial lactate less than 7 mmol/L, a maximum lactate less than 9 mmol/L, or a 4- to 6-hour lactate level less than 4 mmol/L survived to hospital discharge.

CONCLUSIONS

Serum lactate levels may be a useful predictor of mortality in children less than 1 year of age who have undergone cardiopulmonary bypass. An elevation in serum lactate level after a complex operation for congenital heart disease should be taken as a serious indicator of potential mortality.

A randomized cross-over comparison of the hemodynamic response to intermittent hemodialysis and continuous hemofiltration in ICU patients with acute renal failure

OBJECTIVE

To compare the hemodynamic response of ICU patients with acute renal failure of a 24-h continuous arteriovenous hemofiltration (CAVH) and that of patients with a 4-h intermittent hemodialysis (HD).

DESIGN

Cross-over randomized clinical trial. The two periods to be compared were a 24-h CAVH and the 24-h encompassing a 4-h HD. These two periods were separated by a 24-h wash-out period.

SETTING

Ten bed medicosurgical ICU of a tertiary care center in Paris, France.

PATIENTS

Inclusion criterion was the requirement of replacement therapy for acute renal failure in patients already submitted to mechanical ventilation.

INTERVENTIONS

CAVH was performed with Ringers' lactate used for restitution and infused before the hemofilter. The ultrafiltrate output was maintained at around 15 ml/min. HD was performed with a bicarbonate-buffered dialysate.

MEAN OUTCOME MEASURES

Mean arterial pressure (MAP), use of adrenergic drugs, and change in body weight during each period.

RESULTS

Twenty-seven consecutive patients were included, 15 CAVH-HD and 12HD-CAVH. CAVH and HD allowed the same metabolic efficacy. No hemodynamic parameter (MAP, amount of adrenergic drugs, change in body weight) differed between the two methods.

CONCLUSIONS

CAVH is equivalent to HD in terms of MAP and the use of vasopressive drugs and fluids. Establishing the superiority of CAVH would require carefully controlled studies assessing either outcome or changes in tissue oxygenation.

Alterations in carbohydrate metabolism during stress: a review of the literature

Patients with sepsis, burn, or trauma commonly enter a hypermetabolic stress state that is associated with a number of alterations in carbohydrate metabolism. These alterations include enhanced peripheral glucose uptake and utilization, hyperlactatemia, increased glucose production, depressed glycogenesis, glucose intolerance, and insulin resistance. The hypermetabolic state is induced by the area of infection or injury as well as by organs involved in the immunologic response to stress; it generates a glycemic milieu that is directed toward satisfying an obligatory requirement for glucose as an energy substrate. This article reviews experimental and clinical data that indicate potential mechanisms for these alterations and emphasizes aspects that have relevance for the clinician.

Arterial or mixed venous lactate measurement in critically ill children. Is there a difference?

Seven critically ill children had simultaneous measurement of whole blood lactate concentrations obtained from a systemic arterial and mixed venous (pulmonary artery) site. An excellent correlation was found (r = 0.995). The mean difference between arterial and mixed venous values was 0.02 mmol/l and the limits of agreement (+/- 0.22) were -0.20 to 0.24. The differences found were clinically insignificant (two-tailed paired Student's t-test; p = 0.36) and therefore support the continued use of arterial sampling for blood lactate measurement.

Lactic acidosis and acute ethanol intoxication

Ethanol intoxication has been widely reported as a cause of lactic acidosis. To determine the frequency and severity of ethanol-induced lactic acidosis, patients who presented to an emergency department with a clinical diagnosis of acute ethanol intoxication and a serum ethanol concentration of at least 100 mg/dL were studied. Arterial blood was sampled for lactate and blood gas determinations. A total of 60 patients (mean age, 41 years) were studied. Twenty-two patients sustained minor trauma. Ethanol concentrations ranged from 100 to 667 mg/dL (mean, 287 mg/dL). Lactate concentrations were abnormal (> 2.4 mmol/L) in seven patients (11.7%). In all cases, blood lactate was less than 5 mmol/L. Of the patients with elevated lactate, other potential causes for lactic acidosis, including hypoxia, seizures, and hypoperfusion, were also present. Only one case with elevated blood lactate concentration had associated acidemia. Significant elevations of blood lactate are uncommon in acute ethanol intoxication. In patients with ethanol intoxication who are found to have lactic acidosis, other etiologies for the elevated lactate level should be considered.

Severe lactic acidosis related to acute thiamine deficiency

The authors report a case of severe lactic acidosis in a 3-year-old boy, after 20 days of total parenteral nutrition without vitamin supplementation. This child with acute lymphoblastic leukemia underwent a period of severe refractory lactic acidosis (pH between 6.81 and 7.00 and a serum lactate level up to 38 mmol/liter) leading to cardiac arrest. After the initial resuscitation and the subsequent treatment of shock and vitamin K deficiency, acute peritoneal dialysis was instituted to correct the severe lactic acidosis. Initial low plasma thiamine levels confirmed the diagnosis of thiamine deficiency. An associated transient pancreatic dysfunction was also noted. The patient's overall course with thiamine replacement therapy led to a complete recovery within 5 days and no sequelae were noted after 12 months.

Lactate levels as predictors of the relationship between oxygen delivery and consumption in ARDS

We reviewed the changes in Do2 and Vo2 in 58 patients with ARDS after interventions which included fluid loading, blood transfusion, and PEEP. After a significant change in Do2, patients with lactic acidosis (lactate level greater than 2.4 mmol/L) exhibited significant corresponding changes in Vo2 (p less than 0.001); however, no change in Vo2 was observed in patients without lactic acidosis (1-beta greater than 0.8). We conclude that a biphasic pattern of oxygen utilization in patients with ARDS emerges when subsets of patients with and without lactic acidosis are compared. Lactic acidosis, a marker of anaerobic metabolism, may be a characteristic of patients with ARDS who exhibit changes in Vo2 that are dependent on changes in Do2.

Lactic acidosis

An understanding of the pathophysiology of lactic acidosis is crucial in facilitating the optimal care of critically ill patients. The relevant biochemistry of lactic acidosis is reviewed, and the more controversial aspects relating to the genesis of the acidosis are highlighted. The current system of classification of lactic acidosis divides etiologies on the basis of the presence or absence of clinical signs of tissue hypoperfusion. Several types of lactic acidosis in which clinical evidence of tissue hypoperfusion is lacking demonstrate hemodynamic evidence of occult hypoperfusion. The diagnostic and therapeutic implications of this observation are discussed. Current diagnostic criteria for lactic acidosis include a pH less than 7.35 and blood lactate concentration greater than 5 to 6 mM/L. An important issue relates to the implications of lactate values that are greater than normal but below this diagnostic range. The use of the oxygen flux test may be valuable in the diagnosis of occult tissue hypoperfusion in patients with low-grade elevations in lactate levels. The current therapy for lactic acidosis involves addressing the primary cause and supportive management. The use of bicarbonate in the therapy for lactic acidosis is controversial due to potential adverse effects on cardiac function. The specifics of this controversy are outlined, and newer therapeutic alternatives are reviewed. The use of blood lactate concentration as a prognostic index may be more useful in patients with shock than without shock.