In the world, 230 million surgeries are performed every year and US data indicates that more than a third of patients who undergo surgery are older than 65 years, in which between 10 and 70% develop postoperative delirium (POD). Patients who develop POD have poor outcomes, such as a longer hospital stay, a deterioration in functional and cognitive status, high mortality rates, and an increase in health costs.

Delirium is an entity that in a significant percentage is preventable, thus preventing the development of POD is fundamental. In fact, in older adults hospitalized in the no surgical ward, the implementation of non-pharmacological prevention measures of delirium has consistently shown to significantly prevent the development of this condition. However, limited information is available about the usefulness of non-pharmacological intervention protocols applied in the perioperative context to prevent POD.

The main aim of this project is to determine whether the application of non-pharmacological measures during the perioperative period prevents POD in elderly patients undergoing highly complex elective surgeries.

The hypothesis is that the application of these measures decreases the incidence of delirium in this population.

To determine whether non-pharmacological measures decrease the incidence of POD during the perioperative period in elderly patients undergoing highly complex elective surgeries, it will be performed a randomized clinical trial, where two groups of patients older than 75 years undergoing highly complex elective surgeries will be compared:

1. The first group will receive a protocol of non-pharmacological interventions implemented by occupational therapy teams to prevent delirium plus standard non-pharmacological prevention interventions.
2. The second group will only receive standard non-pharmacological prevention interventions.

This study will be carried out in the surgical units of the Hospital Clinico de la Universidad de Chile (HCUCH) and in the Hospital San Jose (HSJ).

The expected result is to demonstrate that the interventions carried out by occupational therapists decrease the incidence of DPO in a significant way in comparison with standard prevention intervention.

Inclusion Criteria:

• Hospital admission for highly complex elective surgery

Exclusion Criteria:

• History of cognitive impairment.
• A low score in Mini-Mental State Examination (MMSE): <23 points if the patient has 6 or more years of schooling, and <18 points if the patient has <6 years of schooling.
• Severe communication disorder and cultural language limitation (language other than Spanish).
• Delirium on admission or prior to the start of the intervention (measured with CAM).
• Patient enrolled in another study

Patients were randomized in 16 blocks of 10 patients and only one investigator has the randomized information. This researcher will not have any role in the recruitment, intervention, and diagnosis of postoperative delirium. Also, the analysis of data will be performed by researchers who will be masked to the randomization information.