Why must plastic containers of the Baxter Healthcare Ltd product Potassium Chloride 0.15% w/v and Glucose 10% w/v Solution for Infusion BP not be connected in series?

Plastic containers of the Baxter Healthcare Ltd product Potassium Chloride 0.15% w/v and Glucose 10% w/v Solution for Infusion BP must not be connected in series because residual air drawn from the primary container before the secondary container finishes delivering fluid could cause air embolism.