The potential benefit of continuous glucose and lactate monitoring

The potential benefit of continuous glucose and lactate monitoring
Azriel Perel, MD
Professor of Anesthesiology and Intensive CareSheba Medical Center, Tel Aviv, Tel
Aviv University, Is rael
A new technology for the continuous and simultaneous measurement of both glucose and lactate
has been recently introduced into clinical use. This monitoring device (EIRUS, MAQUET) is
composed of a central venous catheter with an integrated microdialysis function (1,2). This
lecture will explore the theoretical clinical benefits of such novel monitoring technology.
Critically ill patients often develop (stress-induced) hyperglycemia, which, when left untreated,
has been shown to be associated with increased mortality and morbidity. Several seminal studies
have therefore promoted Intensive Insulin Therapy (IIT) in order to achieve Tight Glycemic
Control (TGC). However, later studies failed to reproduce the same benefits of TGC.
Furthermore, they have pointed out that TGC may be associated with more frequent episodes of
hypoglycemia due to overzealous IIT leading to inadequate blood glucose control.In addition,
exaggerated variability of glucose levels has also been shown to be associated with worse
outcome. The achievement of adequate and safe glucose control has been dependent, until
recently, on frequent intermittent blood sampling which are both time-consuming and costly. The
newly introduced technologies for continuous glucose monitoring (3) offer a more practical and
safer alternative, as a continuous measurement may prevent long periods of undetected hyper- or
hypoglycemia, while enabling a safer implementation of a more pro-active glucose control
approach. It is also possible that TGC with continuous glucose measurement will reduce glucose
variability irrespective of the target range.
Hyperlactatemia is a useful surrogate marker representinganaerobic metabolism resulting from an
imbalancebetween oxygen supply and demand in the tissues. During circulatoryshock, inadequate
oxygen deliveryresults in mitochondrial hypoxia.Under such hypoxicconditions,
mitochondrialoxidative phosphorylationfails, and energy metabolism becomes dependenton
anaerobic glycolysis. Anaerobicglycolysis sharply increases theproduction of cellular lactate,
which diffusesinto the blood during prolonged cellhypoxia. Since elevated lactate levels are
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associated with poorer outcome, and their prognostic value exceeds that ofblood pressure, for
example, lactate is being used as an outcome marker (4).In patients with a clinical pictureof
severe infection, the blood lactateconcentration varies in proportionto the ongoing deficit in tissue
oxygenation,and the ability of the patient to reducethe blood lactateconcentration
indicatesrestoration of oxygen deliverywith resuscitation. Early resuscitationtargeting lactate
clearance as themarker of adequacy of oxygen deliverywas found to be non-inferior to ScvO2
monitoring for theoutcome of in-hospital mortality.Thus lactate trends can provide vital
information regarding the patient’s response to resuscitation interventions, while an increase in
lactate can point to continuing deterioration. This information may not be provided in a timely
manner by intermittent monitoring.. Changes in lactate levels in any patient deserve attention,
although increases in lactate may also be due to increased glycolysis or poor lactate clearance
(e.g. due to liver dysfunction) (6). The ideal time-domainof continuous lactate measurements
remains to be determined. However, our ability to continuously monitor lactate provides us with
new opportunities to detect and follow low-flow states, as well as better understandlactate's
unique pathophysiologicalfeatures.
References
1. Schierenbeck F, et al. Evaluation of Intravascular Microdialysis for Continuous Blood
Glucose Monitoring in Hypoglycemia: An Animal Model. Journal of Diabetes Science
and Technology 2014; 8:839.
2. Schierenbeck F, et al. Introducing intravascular microdialysis for continuous lactate
monitoring in patients undergoing cardiac surgery: a prospective observational study.
Critical Care 2014; 18:R56.
3. Wernerman J, et al. Continuous glucose control in the ICU: report of a 2013 round table
meeting. Critical Care 2014;18:226.
4. Casserly B, et al. Lactate measurements in sepsis-induced tissue hypoperfusion: results
from the surviving sepsis campaign database.Crit Care Med. 2015 ;43:567.
5. Jones AE, et al. Lactate clearance vs central venous oxygen saturation as goals of early
sepsis therapy: a randomized clinical trial.JAMA. 2010 ;303:739.
6. Bakker J, et al. Clinical use of lactate monitoring in critically ill patients.Ann Intensive
Care2013 ;3:12.
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