Arterial vs. Venous blood in different lab measurements (CBC, Chemistry, Blood Gas)

[dancoster]

Prerequisites

• [X] Put an X between the brackets on this line if you have done all of the following:
  • Checked the online documentation: https://mimic.mit.edu/
  • Checked that your issue isn't already addressed: https://github.com/MIT-LCP/mimic-code/issues?utf8=%E2%9C%93&q=

Description

Hi, thanks for all the important work you all do on MIMIC.

I'm trying to compare glucose levels in Arterial and Venous blood. For this purpose, I saw that for part of the Blood Gas measurements the specimen type (Arterial blood vs. Venous blood) is available (following the CHARTTIME's trick in #488, #1161 and bg.sql script).

However, for the rest of the glucose measurements (for example ITEMID=50931 of the chemistry measurement) I couldn't find any information on the specimen type and I wonder if it is possible to assess whether the blood was obtained from Arterial or Venous blood.

I thought it might be beneficial to use the following heuristic - First, generate the central line and arterial line durations based on the queries mentioned in #371, and then 'Map' each glucose measurement to Venous vs. Arterial based on the existence of the central/arterial line (I saw that there are overlapping in part of the rows, so I'll exclude these measurements).

Your comment/advice would be greatly appreciated!

Many thanks in advance,

Dan

[aegis301]

Not an official answer but I might be able to offer some medical perspective here: While this is a reasonable approach it has some flaws. Blood samples will not always be drawn from either arterial lines or central lines. You are right that if the patient has an arterial line, most of the bloodsamples are drawn from here. However there might be scenarios where the arterial line is clotted and another form of access is used (peripheral venous cath or direct access transdermal puncture). These might be edge cases so I don't know how large your margin for error might be. Another point might be that I don't know how reliable documentation of central and arterial lines are, MIMIC owners might be able to offer some perspective here.

Another off-topic point: You might want to consider pushing this into discussions :).

Greetings!

[dancoster]

Thanks for your detailed reply @aegis301! I understand my heuristic is not perfect, but that's the only solution that I found... @alistairewj if you have any input into this question it would be greatly appreciated. Dan