This is a question I remember asking myself quite a bit during my training when I used to check/trend lactate levels more than I do today. Does it really matter whether I check it from an arterial line or from a venous stick?

This study which was a prospective study of 100 patients who had both an arterial line and a central line. The authors compared the values during resuscitation. Short answer is no, there’s no statistically significant difference.

Does this reflect the real world? Not really. As much as I would like to have an arterial line in all of my septic shock patients, this does not necessarily happen right away. Arterial lines, even for me who has put in hundreds, is not the easiest of procedures. I actually failed miserably on a patient in 5 different sites several weeks ago. I have excuses but I won’t share them ;). Also, it is time consuming and causes the patient discomfort. That being said, when someone is sick sick, they get an arterial line from me or my trusty badass RT’s.

The other real-world concern is the central line issue. There’s data out there that you don’t necessarily need a central line to run vasopressors, some of that data is my own data (my ONLY data out there haha). That being said, these patients will have their venous lactate checked via a peripheral stick, in many cases using a tourniquet. Using a tourniquet has its own problems as that could make the lactate levels unreliable.

Now, let’s say that you have both an arterial line and a central line, then you can use this data more appropriately. Sort of. The authors did not specify whether they used the same point-of-care device to check the lactate levels in the venous nor arterial values. You know, some shops use POC for arterial, some have the fancy machine inside the ICU. Some could run the venous blood in that fancy machine, the POC, and some shops have to send it downstairs to the lab. This was not specified. Sigh.
Either way, I need to dissect the data regarding tourniquets for you.
-EJ

A. Mahmoodpoor, K. Shadvar, S. Sanaie, et al., Arterial vs venous lactate: Correlation and predictive value of mortality of patients with sepsis du…, Journal of Critical Care, https://doi.org/10.1016/j.jcrc.2019.05.019
Link to Abstract

If you are interested in going through my analysis on many questions lactate, lactic acid, and its metabolism, click here.