Validation of the Confusion Assessment Method in the Intensive Care Unit in the Post-Anesthesia Care Unit

Abstract

Introduction: Patients who develop delirium while hospitalized are increasingly recognized as at risk for the development of long term cognitive impairment. We became interested in the contribution of delirium to the development of post-operative cognitive dysfunction (POCD) when we found that patients at Mayo Clinic in Arizona, compared to patients at the Mayo facilities in Rochester, MN, were 17 times more likely to receive the drug physostigmine (Antilirium®) for the treatment of delirium in the Post Anesthesia Care Unit (PACU). However, before we could examine the relationship between delirium and POCD we needed to validate a tool we could use to quickly assess the presence of delirium in patients emerging from anesthesia in the PACU. Hypothesis: The Confusion Assessment Method in the Intensive Care Unit (CAM-ICU) can be used in the PACU to identify patients with delirium. Methods: Patients 65 years of age or greater who were going to have a standardized general anesthetic for a surgical procedure were identified on the day of surgery and consent to participate in the study was obtained. The CAM-ICU was used preoperatively to determine study eligibility (patients who scored less than 7 [scale of 1-10], indicating delirium, on the test were not followed further) and postoperatively, one hour after the patient was admitted to the PACU, to assess for delirium. The CAM-ICU was administered after we asked the patient’s nurse whether or not he or she had determined that the patient was delirious. Results: 168 patients, mean age 75 ± 7 (SD) with the majority of participants having urologic or orthopedic procedures were assessed pre- and post-operatively with the CAM-ICU, and post-operatively by a nursing assessment for delirium. The CAM-ICU took little time to administer and was easy for patients to understand and use. The nurse at the bedside identified 5 of 168 patients as delirious (prevalence of 2.98%). The CAM-ICU was positive for delirium in 11 of 168 (6.55%). The CAM-ICU had a sensitivity of 60% (3/5) and a specificity of 95% (155/163). Conclusion: In this investigation, the CAM-ICU was easy to use and had a high specificity for identifying post-operative delirium.