Temperature and time stability of whole blood lactate: implications for feasibility of pre-hospital measurement
1 Division of Pulmonary and Critical Care Medicine, Harborview Medical Center, Seattle, WA, USA
2 KL2 Clinical Research Scholar, University of Washington Institute of Translational Health Sciences, Seattle, WA, USA
3 Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, MI, USA
4 Robert Wood Johnson Foundation Clinical Scholars Program, University of Michigan, Ann Arbor, MI, USA
5 Department of Surgery, Harborview Medical Center, University of Washington, Seattle, WA, USA
6 King County Medic One, Division of General Internal Medicine, University of Washington, Seattle, WA, USA
7 Department of Laboratory Medicine, University of Washington, Seattle, WA, USA
BMC Research Notes 2011, 4:169 doi:10.1186/1756-0500-4-169Published: 30 May 2011
To determine the time and temperature stability of whole blood lactate using experimental conditions applicable to the out-of-hospital environment.
We performed a prospective, clinical laboratory-based study at an academic hospital. Whole blood lactate was obtained by venipuncture from five post-prandial, resting subjects. Blood was stored in lithium heparinized vacutainers in three temperature conditions: 1) room temperature (20°C), 2) wrapped in a portable, instant ice pack (0°C), or 3) wet ice (0°C). Lactate concentrations (mmol/L) were measured at 0, 5, 10, 20, and 30 minutes after sampling, and compared using repeated measures analysis of variance.
Mean baseline lactate among resting subjects (N = 5) was 1.24 mmol/L (95%CI: 0.49,1.98 mmol/L). After 30 minutes, lactate concentration increased, on average, by 0.08 mmol/L (95%CI: 0.02,0.13 mmol/L), 0.18 mmol/L (95%CI: 0.07,0.28 mmol/L), and 0.36 mmol/L (95%CI: 0.24,0.47 mmol/L) when stored in wet ice, ice pack, and room temperature, respectively. The increase in lactate was similar in samples wrapped in portable ice pack or stored in wet ice at all time points (p > 0.05), and met criteria for equivalence at 30 minutes. However, lactate measurements from whole blood stored at room temperature were significantly greater, on average, than wet ice or portable ice pack within five and ten minutes, respectively (p < 0.05).
Whole blood lactate measurements using samples stored in a portable ice pack are similar to wet ice for up to 30 minutes. These conditions are applicable to the out-of-hospital environment, and should inform future studies of pre-hospital measurement of lactate.