- An operating room case record form (CRF) and surgical ward CRF will be completed for every eligible patient who undergoes surgery during the seven day cohort period. Patients will be followed up until hospital discharge. This will be censored at thirty days i.e. patients will be followed up until discharge or for thirty days whichever is the shorter period. If a patient is admitted to critical care at any time during the follow-up period, then a critical care CRF will be completed. The critical care CRF may therefore be completed for patients admitted to critical care after the seven day cohort period is complete.