"Surgery cancelled"

My parent was supposed to have surgery recently. They had been advised to fast from midnight and to stop drinking any liquid early morning. We arrived on time at the hospital and waited for about an hour at the Day Surgery admission reception. We were finally called in to go through the admission process an hour after we arrived, checking blood pressure and health history, etc. Things went well and by around half an hour later we were put at the lounge/waiting room with the other patients and were just waiting for my parent to go into theatre. 

We waited and waited. 5 hours from when we arrived passed, no news. 6 hours passed, no news.

7 hours passed, my parent was feeling hungry, in pain, exhausted, weary and stressed. 

I asked a nurse for an update and was told there's a bit of a delay due to emergencies.

8 hours passed, my parent still was not called into theatre.

After 8.5 hours passed, all of us (my parent and family members) who had been waiting since early morning, were fed up. I went to the nurse again who advised that the doctor is coming to see us soon. With this, I knew that my parent's surgery would not go ahead. We waiting around 20 mins until the doctor came, so it was 9 hours of waiting. 

I was right, my parent's surgery had been postponed. 

It was kind of the doctor to apologise for the delay, but I feel it is unacceptable and incredibly unprofessional of the hospital management not to advise us earlier that the procedure had been cancelled. Did my parent really need to wait 9 hours, fast for 17 hours and have a very little sip of water all day? Couldn't they have been told earlier in the afternoon that they were not going into theatre? 

Now my parent is incredibly stressed and worried that their cancer will spread while waiting for their surgery to be rescheduled, and their back pain is getting worse. We weren't told how long we have to wait to be notified of the rescheduled date.

All of us (except my parent) had all taken the day off work. I had also planned leave off work for the next month to care for my parent post-surgery and planned for extra daycare days for my child which I won't be able to get a refund for unless I've given 2 weeks' notice.  This whole thing made me realise how inconsiderate I feel hospital staff are to people's lives.