Patient selection:
(1) critically ill with severe sepsis
(2) baseline blood lactate < 3 mmol/L
Protocol: Infuse sodium lactate 1 mmol/kg over 15 minutes through a central venous catheter using a peristaltic pump and a solution of 1 molar lactate per L (1 mmol/mL).
where:
• The molecular weight of sodium lactate is 112.1 g (90.08 for lactic acid).
infusion rate for the 15 minutes in mL per minute =
= (body weight in kg) / 15
The blood lactate concentration was sampled at 60 minutes after starting (45 minutes after completing) the lactate infusion.
change in blood lactate at 60 minutes after starting the infusion =
= (blood lactate level at 60 minutes after starting the infusion) - (baseline blood lactate prior to the infusion)
Interpretation:
• A change in the blood lactate >= 0.6 mmol/L was considered a low clearance of exogenous lactate.
• A low clearance of exogenous lactate after the infusion is predictive of a poor outcome independent of other known risk factors.
Independent risk factors for mortality by 28 days:
(1) age of patient > 70 years
(2) >= 3 organ failures
(3) change in lactate at 60 minutes after starting lactate infusion >= 0.6 mmol/L
|
Risk Factor
|
Odds Ratio
|
95% CI
|
p value
|
|
age > 70 years
|
5.7
|
1.2 - 28.4
|
0.03
|
|
>= 3 organ failures
|
27.5
|
1.2 - 651.4
|
0.04
|
|
change in blood lactate >= 0.6 mmol/L
|
14.2
|
1.1 - 182
|
0.04
|
from Table 4, page 708
Performance:
• Sensitivity of change in lactate level was 53% with specificity 90%.
Implementation Note: To estimate the relative risk of mortality at 28 days, I developed a simple score based on multiples of the lowest odds ratio. This gives 1 point for age, 2.5 points for blood lactate and 5 points for organ failures. Scores range from 0 to 8.5 with 8 possible combinations (0, 1, 2.5, 3.5, 5, 6, 7.5 and 8.5).
