HL7 Event : A11 : Cancel Admit

  MSH           Message Header
  EVN           Event Type
  PID           Patient Identification
   [PD1]        Additional Demographics
  PV1           Patient Visit
  [ PV2 ]       Patient Visit - Additional Info.
  [ { DB1 } ]   Disability Information 
  [ { OBX } ]   Observation/Result
  [ { DG1 } ]   Diagnosis Information