Assessment of Immediate Postoperative Delirium (IPD) in Adult Patients: Incidence and Etiologic Factors

Decision to perform this observational study was made due to the lack of information on the local incidence and risk factors for the development of immediate postoperative delirium (IPD).

A literature review was done to study the already implicated perioperative causative factors as well as other significant perioperative factors.

A consultant neurologist was contacted to confirm the appropriateness of using CAM-ICU, RASS and NPS as assessment tools for the study. Doctors and nurses were trained on the proper use of the assessment tools using educational material at www.icudelirium.org. Permission was obtained from the author who has done validation of arabic version of CAM-ICU score. A proforma was prepared and local Ethical committee approval was obtained.

A pilot study of 24 cases showed the incidence of IPD to be about 25%. The investigators expected to have a total of 600 adult cases undergo anesthesia during the study period of three months. Based on a population size of 600 patients, a level of confidence of 95% and an error of 10% on either side, the optimum sample size was calculated as 395 patients.

The details of the study were explained to each patient with help of information sheet by a dedicated nurse and a doctor well versed in local language. After patient agreement, a written informed consent was obtained. The preoperative scoring of pain, anxiety and agitation and delirium was done by a dedicated nurse under supervision of a doctor who was not involved in providing anesthesia to the patient. Pain was assessed using NPS, sedation/agitation/anxiety using RASS and delirium using CAM-ICU score.

Patient identity was concealed and names were not written in the master chart. The data were entered and identified by the hospital medical registration number (MRN) as well as code number. The patient data were kept locked with password protected file by principal investigators. The premedication choice, anesthetic technique and intraoperative management were carried out in the usual way and recorded on proforma.

Further patient specific data were obtained using the Hospital Information System and Operating Room record. The following data were recorded for each patient:

Demographic Data: Age, gender of the patient

Comorbidity Data: All co-morbidities of patient like diabetes, hypertension, bronchial asthma, ischemic heart disease, jaundice, carcinoma, liver disease, kidney disease, drug addiction, alcoholism, sickle cell disease, medication details and any other co-morbidities.

Laboratory Data: hemoglobin level, creatinine, electrolyte levels, serum albumin, ammonia level and any blood work done preoperative, intraoperative or postoperative in PACU.

Surgical Data: diagnosis, urgency and name of surgery

Peri-operative Anesthetic Data: American Society of Anesthesiologists (ASA) class, premedication, pre-operative medications, hydration status, anesthetic method, analgesics, prophylactic anti-emetic drugs, intraoperative hemodynamic parameters, oxygen saturation, ventilation status, acid-base status, presence of sepsis, fluid and electrolyte imbalance, pain, myocardial infarction, hypo/hyperthermia, alcohol withdrawal and other significant conditions.

Presence of an airway, urinary catheter or a surgical drain at admission to PACU was also recorded.

At the end of anesthesia, all patients were transferred to PACU. The management of the patient was done in the usual manner as prescribed by the involved anesthetist and carried out by allocated PACU nurse. Patients were assessed for pain, agitation, sedation and delirium using NPS, RASS and CAM-ICU score by another trained staff nurse who was not involved in patient management. Scoring was done at fifteen minutes from end of anesthetic, thirty minutes from end of anesthetics and just prior to discharge from PACU (up to 120 minutes from end of anesthetic).

Postoperative course (presence of delirium, requirement of treatment for delirium, length of stay, postoperative complications, admission to high dependency unit or Intensive care unit) was followed via electronic patient record and recorded by concerned anesthetist on the proforma.

The proforma were handed over to the principal investigator and were kept locked. The recorded patient data except the name were entered by one of the assigned co-investigator into the master chart. A copy of master chart without MRN was sent to statistician for analysis.