Q. Re- above question. I once heard in a shiur, that since the Gemorah teaches when a sickness is sent to a person, an oath is made with that sickness so it will not leave the person, only at an appointed time and by an appointed doctor. Therefore Halacha dictates, that if he was chosen and called as a doctor, he can't refuse and ask the patient to call 911 or any other medic. Is that true?
A. Indeed the Talmud (Avodah Zarah 58a) teaches that the sickness is sworn to depart only by the appointed physician, time and medicine. Yerushalmi (Nedorim 4: 2) mentions that "not from all (doctors) does a person merit to be cured."
Therefore, Shvus Yaakov (Y.D. 1: 86) rules in regards to a physician in avelus that he may attend the sick in a case of sakana, even if there are others that can replace him, due to the oath mentioned above, since he may be the only one appointed to cure that illness. (See Pischei Teshuva Y.D. 380: 1, and Sdei Chemed - M. Avelus 44).
Boruch Sheomar (Tefilah p.125) rules that due to the above teachings, a physician that was asked to attend to a particular patient, cannot refuse.
However, Horav Shlomo Miller's Shlit'a opinion is that being called, does not establish at all that he is the chosen physician, and if there are others that can treat him faster or better, or if he is an avel etc.,let the others available medics cure, as they may be the appointed ones.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a