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

Overview

Delirium is considered to be acute failure of central nervous system. It is acute confusional state characterized by decline from baseline mental level, attention deficit and disorganized thinking. Postoperative delirium is known to prolong length of stay in hospital, cause functional decline and dementia, increase all-cause mortality and increase the medical cost. It is also associated with other outcomes like cardiac arrest, ventricular tachycardia or fibrillation, myocardial infarction, pulmonary edema, pulmonary embolism, bacterial pneumonia, respiratory failure requiring intubation, renal failure requiring dialysis and stroke. There are well known predisposing and precipitating factors related to its etiology. However, the effect of type of anesthesia is not very clear. There have been no major clinical trials in this part of the world to delineate the incidence of immediate postoperative delirium (IPD). The investigators have undertaken this prospective observational study to determine the incidence of IPD and its etiological factors in adult patients during their stay in the Post-Anesthesia Care Unit (PACU) following surgery under different types of anesthesia (general anesthesia, regional anesthesia and monitored anesthesia care). The study was done over a period of about three months. Assessment for delirium was done using Confusion Assessment Method-Intensive Care Unit (CAM-ICU score, English/Arabic version). Sedation and Agitation were assessed using Richmond Agitation Sedation Score (RASS). Pain was assessed using Numeric Pain Score (NPS). Assessment was done within 24 hours prior to surgery and was repeated at three different intervals in PACU. Details of perioperative management were recorded and analyzed. The incidence of IPD and its etiologic factors were identified thereby leading to corrective action.

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.