In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you are a surgeon doing surgery, you should not break the fast by eating or drinking – if doing so may jeopardize the procedure.
However, if you can sip water without any interference with the procedure, you should do so.
Saving lives is one of the noblest of deeds in Islam; as such, your work merits numerous rewards. So, if you need to postpone iftar to do so, it does not in any way diminish your rewards for fasting as saving lives has precedence – since it is one of the fundamental objectives of the Shari`ah.
Almighty Allah knows best.