For those at hospitals with children units, do send send blood products syringes and/or aliquot bags through the pneumatic tube system? If you do did you do a validation for tubing products in syringes? 

Do you return to inventory unused blood products issued in syringes or aliquot bags? If you do what is the acceptance requirement?

We do perform both activities.  Since we had already validated the system for transport of all other products, we validated syringes by ensuring that when they were sent they wouldn't leak or break.  We also add a little additional padding to the tubes with syringes to guarantee they are held in place.

We send both syringes and bags through the tube system.  

We have a special cap that we use for syringes for which it is obvious if someone has taken it off.  That is to prevent partially used syringes from being accepted back into stock.  

That was an issue for all syringes, not just the ones sent through the tube.