cpt 76700 ultrasound, abdominal real time

Yesterday I found out that all trauma patient that come in gets an ultrasound abdominal to rule out or confirm if there is any fluid/blood in the abdominal that can cause a life threaten event..in viewing code correct it looks like this code can be billed with critical care 99291..Does anyone know what need to be documented in order to bill..also reimbursement is $45.93 for physician and $114.97 for facility