Blood Gas Analysis


Lactate in Critical Illness—Implications for Monitoring Karen Robinson, RCP (NBRC), POCS1


and Gail L Kongable, RN, MSN, FNP2 1. Lewis Gale Medical Center, Salem, Virginia; 2. The Epsilon Group, Charlottesville


Abstract


Hyperlactatemia occurs in nearly half of all patients admitted to the intesive care unit (ICU) and is associated with significantly increased mortality. Lactate levels outside of the ‘normal’ reference range (<2–4mEq/l) are thought to also reflect injury severity, but lactate can be present under stable oxygenation and hemodynamic conditions. Recent evidence also suggests that intervention should be initiated while lactate levels are in the normal reference range and rising to be most effective. The frequent measurement of lactate using blood glucose analyzers is useful in identifying patients at an increased risk for poor outcomes.


Keywords Intensive care unit (ICU), lactate, sepsis, blood glucose analyzer


Disclosure: The authors have no conflicts of interest to declare. Acknowledgment: The authors acknowledge Roche Diagnostics Corporation, Professional Diagnostics for the Hospital, maker of cobas b 221 blood gas analyzer for supporting the development of this manuscript. Received: September 6, 2010 Accepted: November 23, 2010 Citation: US Respiratory Disease, 2010;6:52–5 Correspondence: Gail Kongable, RN, MSN, FNP, The Epsilon Group, Virginia, 615 Woodbrook Drive, Charlottesville, VA 22901. E: gkongable@tegvirginia.com


Support: The publication of this article was funded by Roche Diagnostics Corporation. The views and opinions expressed are those of the authors and not those of Roche Diagnostics Corporation.


Under normal physiologic conditions, serum lactate levels are between 0.5 and 1mEq/l, representing balanced lactate metabolism. Hyperlactatemia in critical illness is considered to be an adaptive response to anaerobic glycolysis1 conditions of sepsis or trauma,2–4


clearance until hemodynamic stabilization.5,6


and higher levels are common during as accumulation exceeds the rate of While lactate levels at


concentrations outside the reference range (<2–4mEq/l) are tolerated in patients, higher levels have been found to be independently related to increased mortality7


goal-directed therapy (EGDT).8


and call for intervention in the form of early In modern intensive care units (ICUs) the


frequent measurement of lactate using blood glucose analyzers is useful in identifying patients at increased risk for death and serve as an early marker of a potentially reversible state.9


Outcomes may be


improved by adapting resuscitation to serial lactate measurements. This article presents a brief discussion of the available evidence.


More recently, not only the presence of hyperlactatemia on admission, but also subsequent development and duration of elevated lactate, are reported to increase the risk for mortality in


Lactate as an Indicator of Severity of Illness Early studies found that elevated venous lactate (≥4mEq/l) was often present in shock patients on admission to the medical ICU and was associated with increased incidence of organ failure and mortality rates >30%.2,3,7


52


surgical and trauma ICU patients.9 Cerovic et al.10


postulated that blood


lactate concentrations in injured patients on hospital admission might be an objective indicator of the patient’s true condition and serve as an independent predictor of injury severity, morbidity, and mortality. These researchers examined the correlation of the admission Injury Severity Score (ISS)11


and Trauma Injury Severity Score (TRISS)12 with lactate levels


drawn at admission, twice daily for the first two days, and daily for a following three days. Lactate levels in non-survivors were significantly higher than those in survivors on admission (6.3 ±5.9 versus 4.2 ± 3.3mEq/l) and at 12 hours (6.1 ± 7.0 versus 3.2 ±1.9mEq/l). Regression analysis demonstrated that injury severity, as measured by the ISS can also be predicted from lactate concentration on admission, while actual or predicted survival, as measured by the TRISS can be predicted from lactate concentration after 12 hours. In surviving patients, lactate showed a progressive decline over time, while levels remained high in non-survivors from the 12-hour sampling until death.


More recently, in a retrospective observational study, Jansen et al.13 examined whether the level and duration of increased blood lactate (>2mEq/l) was associated with daily Sequential Organ Failure Assessment (SOFA)14


scores and organ subscores during the early and


late phases of ICU stay. At 28 days they found a 57% increased risk for death for every day lactate was elevated and every 1mEq/l above


© TOUCH BRIEFINGS 2010


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