English to Dutch Medical

Folks, the word 'piggyback' has always intrigued me in a medical sense ever since my son was in an American hospital at age 3 and he pulled over a contraption on wheels (of course!) that enabled him to move around while his medicine was dripping into him intravenously. At the same time, another liquid medicine was being provided to him, in other words, 'piggybacking' into him via another tube {none of which hindered his activities, I might add!). So I know perfectly well what it means, however, I cannot put it into my supposed mother language!
Any insights will be very much appreciated and Kudo'd!
Marijke