Lactate kinetics in ICU patients using a bolus of 13C-labeled lactate

Hyperglycemia suppresses Lactate Clearance during Exercise in Type 1 Diabetes

CONTEXT

Circulating lactate concentration is an important determinant of exercise tolerance.

OBJECTIVE

To determine the role of hyperglycemia on lactate metabolism during exercise in type 1 diabetes (T1D).

DESIGN

Protocol involved compared T1D participants and participants without diabetes (ND) at euglycemia [5.5mM] or hyperglycemia [9.2mM] in random order in T1D and at euglycemia in ND.

SETTING

Clinical Research Unit, University of Virginia, Charlottesville, VA.

PARTICIPANTS

7 T1D and 7 ND.

INTERVENTION

[1-13C] lactate infusion, exercise at 65% VO2max, euglycemia and hyperglycemia visits.

MAIN OUTCOME MEASURE

Lactate turnover before, during and after 60 min of exercise at 65% VO2max.

RESULTS

A two-compartment model with loss only from the peripheral compartment described lactate kinetics. Volume of distribution of the accessible compartment was similar between T1D and ND (p=0.76) and concordant to plasma volume (∼40ml/kg). Circulating lactate concentrations were higher (p<0.001) in T1D participants during exercise at hyperglycemia than euglycemia. Exercise induced lactate appearance did not differ (p=0.13) between hyperglycemia and euglycemia. However, lactate clearance was lower (p=0.03) during hyperglycemia than euglycemia in T1D. There were no differences in any of the above parameters between T1D and ND during euglycemia.

CONCLUSIONS

Hyperglycemia modulates lactate metabolism during exercise by lowering lactate clearance leading to higher circulating lactate concentrations in T1D. This novel observation implies that exercise during hyperglycemia can lead to higher circulating lactate concentrations thus increasing the likelihood of reaching the lactate threshold sooner in T1D, and has high translational relevance for both providers and recreationally active people with Type 1 diabetes.

Drug monitoring during ciprofloxacin prophylaxis of allogeneic stem cell transplant patients: associations with bacterial infections through a monocentric observational prospective study

BACKGROUND

Bacterial infection ranks amongst the most common causes of morbidity and mortality in patients undergoing allogeneic haematopoietic stem cell transplantation (alloHSCT). Although ciprofloxacin (CIP) prophylaxis is recommended, information on serum levels and clinical course is lacking.

AIM

To investigate relationships between CIP level and failure of prophylaxis, particularly in terms of whether different pharmacokinetic (PK) indices [area under the concentration-time curve (AUC0-24h) vs single time samples] correlate differently with the outcome.

METHODS

This prospective observational monocentric study was conducted at a 1500-bed teaching hospital (March 2018-March 2019), including 63 adult patients with alloHSCT receiving CIP prophylaxis. Blood samples were drawn at three sampling times (1, 6 and 12 h post-administration), twice per week, and measured via high performance liquid chromatography. The onset of febrile episodes (FEBs) indicated suspected failure of CIP prophylaxis. Positive blood cultures [bloodstream infection (BSI)] indicated confirmed failure of prophylaxis.

FINDINGS

Seven of 63 patients died without significant differences in their average CIP levels compared with survivors, with patients experiencing FEBs (54/63) displaying a 13% [95% confidence interval (CI) 4-22%] lower probability of survival. In total, 225 sets of three values (triplets) were obtained from 58 primary CIP episodes. Triplets preceding BSI with Gram-negative bacteria (GNB-BSI) showed lower AUC0-24h on average, but similar single time sample indices. An AUC0-24h of ≤21.61 mgh/L resulted in four-fold higher odds of GNB-BSI (adjusted odds ratio 3.96, 95% CI 1.21-13.00). These results were independent of the administration route, patient demographics or sampling protocol deviations, indicating reduced CIP exposure upon GNB-BSI events.

CONCLUSION

Monitoring CIP levels, using multiple sampling times, may be useful to reduce alloHSCT-associated bacterial infections. Further analysis is needed to investigate causality.

Blood lactate levels in sepsis: in 8 questions

PURPOSE OF REVIEW

Blood lactate concentrations are frequently measured in critically ill patients and have important prognostic value. Here, we review some key questions related to their clinical use in sepsis.

RECENT FINDINGS

Despite the metabolic hurdles, measuring lactate concentrations remains very informative in clinical practice. Although blood lactate levels change too slowly to represent the only guide to resuscitation, serial lactate levels can help to define the patient's trajectory and encourage a review of the therapeutic strategy if they remain stable or increase over time.

SUMMARY

Lactate concentrations respond too slowly to be used to guide acute changes in therapy, but can help evaluate overall response. Hyperlactatemia should not be considered as a problem in itself, but as a warning of altered cell function.

Modeling Challenge Data to Quantify Endogenous Lactate Production

With the intention of isolating the susceptibility of modeling methodology to influence our investigation of the infusion data, we used three kinetic approaches to our models: a simple approach, a unit approach, and a novel approach. The simple approach used exclusively built-in modeling features of the software in terms of units of the infusion dilution (mmol/L), as well as in terms of the precision of switching the infusion on and off. The unit approach used the same switching mechanism as the simple approach, but the units were modeled in those of the infusion (e.g., mmol/kg). Thirdly with the novel approach, we used an automated approach to controlling the infusion, in the sense that as the modeling mechanism sensed the slowdown of the infusion, it was gradually turned off. The units of the analysis for the novel approach were exactly the same as those deployed in the unit approach. Our objective here was to see if common pharmacokinetic parameters were seriously impacted by the particular modeling method.

Lactate Arterial-Central Venous Gradient among COVID-19 Patients in ICU: A Potential Tool in the Clinical Practice

Objective

In physiological conditions, arterial blood lactate concentration is equal to or lower than central venous blood lactate concentration. A reversal in this rate (i.e., higher lactate concentration in central venous blood), which could reflect a derangement in the mitochondrial metabolism of lung cells induced by inflammation, has been previously reported in patients with ARDS but has been never explored in COVID-19 patients. The aim of this study was to explore if the COVID-19-induced lung cell damage was mirrored by an arterial lactatemia higher than the central venous one; then if the administration of anti-inflammatory therapy (i.e., canakinumab 300 mg subcutaneous) could normalize such abnormal lactate a-cv difference.

Methods

A prospective cohort study was conducted, started on March 25, 2020, for a duration of 10 days, enrolling 21 patients affected by severe COVID-19 pneumonia undergoing mechanical ventilation consecutively admitted to the ICU of the Rimini Hospital, Italy. Arterial and central venous blood samples were contemporarily collected to calculate the difference between arterial and central venous lactate (Delta a-cv lactate) concentrations within 24 h from tracheal intubation (T ₀) and 24 hours after canakinumab administration (T ₁).

Results

At T ₀, 19 of 21 (90.5%) patients showed a pathologic Delta a-cv lactate (median 0.15 mmol/L; IQR 0.07-0.25). In the 13 patients undergoing canakinumab administration, at T ₁, Delta a-cv lactate decreased in 92.3% of cases, the decrease being statistically significant (T ₀: median 0.24, IQR 0.09-0.31 mmol/L; T ₁: median -0.01, IQR -0.08-0.04 mmol/L; p=0.002).

Conclusion

A reversed Delta a-cv lactate might be interpreted as one of the effects of COVID-19-related cytokine storm, which could reflect a derangement in the mitochondrial metabolism of lung cells induced by severe inflammation or other uncoupling mediators. In addition, Delta a-cv lactate decrease might also reflect the anti-inflammatory activity of canakinumab. Our preliminary findings need to be confirmed by larger outcome studies.