There is probably room for disagreement here, but the benefits of using an abbreviation in saving space can be outweighed by the disadvantages if there is a significant risk they will be misinterpreted. Medical translators are very often faced with abbreviations they cannot understand (as illustrated by the many questions on this forum). People use undefined abbreviations when they're sure their readers will know what they mean, but I think it's better to err on the side of caution.

A straightforward case is when you have an expression used repeatedly in an article that is abbreviated and given in full on first use. So for example ILOC can be used for initial loss of consciousness if it so defined:

"we classified the severity of the TBI using initial GCS (IGCS)26 and initial loss of consciousness (ILOC)"
After this the author can safely use it later in the article:
"Without ILOC and age > 41 years were significantly associated with 24-hour TST (all p < 0.05)."
https://www.sciencedirect.com/science/article/pii/S092966461...

But without definition there will often be a serious risk that people won't understand ILOC or misinterpret it, for example as induced loss of consciousness, for which it's also used.

So what about "initial LOC"? That's less likely to be misinterpreted, and you can find examples of it. But even there, you need to be very careful, because the trouble is that LOC doesn't always stand for loss of consciousness; it often stands for level of consciousness. So if you put "initial LOC", can you be sure that people will read it as "initial loss of consciousness" and not as "initial level of consciousness?

In the following document, for example, you'll find "Initial LOC" and "decreased LOC":

"The classic _________________ presentation:
Initial LOC
Lucid period
Unresponsive"

"Became nauseated, increasingly confused with decreased LOC"
https://healthtraining.inhs.org/uploadedFiles/EMS_Live_at_Ni...

I think the first probably will be read as "initial loss of consciousness", because "initial level of consciousness" doesn't really make sense. In the second, "LOC" must mean level of consciousness.

You see the problem: if you are determined to use an abbreviation, and it may be appropriate, you must be very careful to ensure that there is no risk of it being misunderstood. If you are not sure, it's better not to abbreviate it.