Apparently, at night:

There is a delay, on average, of 15 minutes in administering life-saving treatment to patients who arrive at night or on weekends by comparison with those who arrive at regular hours. Since it is known that a delay of 30 minutes, irrespective of time of arrival at hospital, results in an increased death rate of 30 percent, the findings of the paper are likely to be real and not just a statistical artefact…