Similarly, large medical centers can have an internist, a surgeon and a pediatrician all on duty at the same time to deal with all those unpredictable conditions that patients come into the ER with. But local hospitals can't necessarily afford the cost of keeping three doctors on duty for a small number of patients.
同樣的，醫學中心可以有內科、外科、小兒科等各科醫生前來輪值，以應付無法預料的各科急診病患，但是地區醫院不見得一個晚上負擔得起三個醫生值班的成本，來等待少數病患。