Corresponding Bundle Element:
Serum lactate measured.
Background:
Hyperlactatemia is typically present in patients with severe sepsis or septic shock and may be secondary to anaerobic metabolism due to hypoperfusion. The prognostic value of raised blood lactate levels has been well established in septic shock patients [1], particularly if the high levels persist. [2,3] In addition, blood lactate levels have been shown to have greater prognostic value than oxygen-derived variables. [4] Obtaining a lactate level is essential to identifying tissue hypoperfusion in patients who are not yet hypotensive but who are at risk for septic shock.
Limitations:
However, the interpretation of blood lactate levels in septic patients is not always straightforward. A number of studies have suggested that elevated lactate levels may result from cellular metabolic failure in sepsis rather than from global hypoperfusion. Elevated lactate levels can also result from decreased clearance by the liver. Although blood lactate concentration may lack precision as a measure of tissue metabolic status, elevated levels in sepsis support aggressive resuscitation.
Implications:
Given the high risk for septic shock, all patients with elevated lactate > 4 mmol/L (36 mg/dl) enter the early goal-directed therapy portion of the Severe Sepsis Resuscitation Bundle, regardless of blood pressure.
This approach is consistent with the trial that established the value of early goal directed therapies, Rivers et al. [5]
Turnaround Time:
Serum lactate must be available in your institution with rapid turnaround time (within minutes) to effectively treat severely septic patients. An arterial blood gas analyzer located in the clinical laboratories usually accomplishes this. However, any means of rapid turnaround time will be acceptable. It is essential for hospitals to invest in adequate equipment in order to meet present standards of care for septic patients.
The technique of obtaining serum lactate by venipuncture typically carries a 24- to 48-hour turnaround time and will not be suitable to care for septic patients. This technique also requires special collection conditions, such as without the use of tourniquet, hindering clinical care.
Arterial vs. Venous Lactate:
In the course of the Surviving Sepsis Campaign the question has been raised many times as to whether an arterial or venous lactate sample is appropriate. While there is no consensus of settled literature on this question, an elevated lactate of any variety is typically abnormal, although this may be influenced by other conditions such as a variety of medications, hepatic insufficiency, or hyperlactatemia due to primarily cardiac causes of hypoperfusion.
Grading the Evidence: [See Ranking the Evidence]
The use of lactate as a method to detect severe sepsis and septic shock and as a rationale for further therapies was evaluated as part of the larger recommendation on initial resuscitation in the 2008 Surviving Sepsis Campaign Guidelines. There, the guidelines committee recommended the protocolized resuscitation of a patient with sepsis-induced shock, defined as tissue hypoperfusion (hypotension persisting after initial fluid challenge or blood lactate concentration equal to or greater than 4 mmol/L).
Evidence Grade 1B: This is a strong recommendation for care based on a number of qualitative considerations. “B” level evidence generally derives from randomized control trials with certain limitations or very well-done observational or cohort studies.
References:
- Weil MH, Afifi AA. Experimental and clinical studies on lactate and pyruvate as indicators of the severity of acute circulatory failure (shock). Circulation. 1970;41:989–1001.
- Vincent JL, Dufaye P, Berre J, et al. Serial lactate determinations during circulatory shock. Critical Care Medicine. 1983;11:449–451.
- Friedman G, Berlot G, Kahn RJ, et al. Combined measurements of blood lactate concentrations and gastric intramucosal pH in patients with severe sepsis. Critical Care Medicine. 1995;23:1184–1193.
- Bakker J, Coffernils M, Leon M, et al. Blood lactate levels are superior to oxygen derived variables in predicting outcome in human septic shock. Chest. 1991;99:956–962.
- Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. New England Journal of Medicine. 2001;345:1368–1377.
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