The prognostic value of blood lactate levels relative to that of vital signs in the pre-hospital setting: a pilot study.
BACKGROUND
A limitation of pre-hospital monitoring is that vital signs often do not change until a patient is in a critical stage. Blood lactate levels are suggested as a more sensitive parameter to evaluate a patient's condition. The aim of this pilot study was to find presumptive evidence for a relation between pre-hospital lactate levels and in-hospital mortality, corrected for vital sign abnormalities.


METHODS
In this prospective observational study (n = 124), patients who required urgent ambulance dispatching and had a systolic blood pressure below 100 mmHg, a respiratory rate less than 10 or more than 29 breaths/minute, or a Glasgow Coma Scale (GCS) below 14 were enrolled. Nurses from Emergency Medical Services measured capillary or venous lactate levels using a hand-held device on arrival at the scene (T1) and just before or on arrival at the emergency department (T2). The primary outcome measured was in-hospital mortality.


RESULTS
The average (standard deviation) time from T1 to T2 was 27 (10) minutes. Non-survivors (n = 32, 26%) had significantly higher lactate levels than survivors at T1 (5.3 vs 3.7 mmol/L) and at T2 (5.4 vs 3.2 mmol/L). Mortality was significantly higher in patients with lactate levels of 3.5 mmol/L or higher compared with those with lactate levels below 3.5 mmol/L (T1: 41 vs 12% and T2: 47 vs 15%). Also in the absence of hypotension, mortality was higher in those with higher lactate levels. In a multivariable Cox proportional hazard analysis including systolic blood pressure, heart rate, GCS (all at T1) and delta lactate level (from T1 to T2), only delta lactate level (hazard ratio (HR) = 0.20, 95% confidence interval (CI) = 0.05 to 0.76, p = 0.018) and GCS (HR = 0.93, 95% CI = 0.88 to 0.99, p = 0.022) were significant independent predictors of in-hospital mortality.


CONCLUSIONS
In a cohort of patients that required urgent ambulance dispatching, pre-hospital blood lactate levels were associated with in-hospital mortality and provided prognostic information superior to that provided by the patient's vital signs. There is potential for early detection of occult shock and pre-hospital resuscitation guided by lactate measurement. However, external validation is required before widespread implementation of lactate measurement in the out-of-hospital setting.
Jansen
Tim C
TC
Department of Intensive Care, Erasmus MC University Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands. t.c.jansen@erasmusmc.nl
van Bommel
Jasper
J
Mulder
Paul G
PG
Rommes
Johannes H
JH
Schieveld
Selma J M
SJ
Bakker
Jan
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010808:Physical Examination; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies
D019344:Lactic Acid