Does anyone determine what dose of heparin to use for flushing ports based on weight? We currenlty lock ports with 5mls heparin (100unit/ml) for those patients weighing 70# or more. We lock ports with 5mls heparin (10init/ml) for those patients weighing less then 70#s. This practice was put in place many years agos and I am being asked for evidence to support the practice. Does anyone else practice this or does any one have any evidence supporting this practice?