Since some of the 1.22 update will introduce more bags, especially medical bags, I thought it would be fitting to have improvised saline.
The way this could work would be to introduce a new item to the loot table: Salt pills

1. Combine a bottle of water with salt pills to get Improvised Saline Bottle
2. Combine the aforementioned bottle with IV Kit to get Improvised Saline IV
3. Apply the same way you would with a normal saline bag, thus consuming the bottle in the process.

As we already are able to craft fish traps and improvised filters with the bottle, this would definitely fit in with the game.