Effect of delirium motoric subtypes on administrative documentation of delirium in the surgical intensive care unit

Abstract

This study compares the proportions of surgical intensive care unit (ICU) patients with delirium detected using the Confusion Assessment Method for the ICU (CAM-ICU) who received administrative documentation for delirium using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, stratified by delirium motoric subtypes. This retrospective cohort study was conducted at a surgical ICU from 06/2012 to 05/2013. Delirium was assessed twice daily and was defined as having ≥1 positive CAM-ICU rating. Delirious patients were categorized into hyperactive/mixed and hypoactive subtypes using corresponding Richmond Agitation Sedation Scales. Administrative documentation of delirium was defined as having ≥1 of 32 unique ICD-9-CM codes. Proportions were compared using Pearson's Chi-square test. Of included patients, 40 % (423/1055) were diagnosed with delirium, and 17 % (183/1055) had an ICD-9-CM code for delirium. The sensitivity and specificity of ICD-9-CM codes for delirium were 36 and 95 %. ICD-9-CM codes for delirium were available for 42 % (95 % CI 35-48 %; 105/253) of patients with hyperactive/mixed delirium and 27 % (95 % CI 20-34 %; 46/170) of patients with hypoactive delirium (relative risk = 1.5; 95 % CI 1.2-2.0; p = 0.002). ICD-9-CM codes yielded a low sensitivity for identifying patients with CAM-ICU positive delirium and were more likely to identify hyperactive/mixed delirium compared with hypoactive delirium.

Keywords: CAM-ICU; Delirium; Delirium motoric subtypes; ICD-9-CM; Surgical ICU.