Do patients with acute medical conditions have the capacity to give informed consent for emergency medicine research?

OBJECTIVE: Because of stress and illness, conscious emergency medicine (EM) patients may be temporarily cognitively impaired and thus incapable of participating in the informed consent process for acute care research. This pilot study sought to assess the mental capacity of ED patients during their evaluation and treatment for acute myocardial infarction (AMI).
METHODS: A prospective observational design at a university tertiary referral center. EM patients with AMI from November 1996 to February 1997 were enrolled. While usual care was delivered, patients were administered three subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) test. Subtest scaled scores range from 1 to 19, with abnormal being less than 5. Demographic, historical, and environmental parameters were recorded. Patients assessed how serious they perceived their conditions; and rated their degrees of pain, nausea, breathlessness, and anxiety on 10-cm visual analog scales (VASs). Testing was repeated prior to hospital discharge.
RESULTS: Twenty-five patients were enrolled. Of these, two (8%) were suspected by their emergency physicians to have insufficient capacity to give informed consent. However, five (20%) scored less than 5 on all of the WAIS-R subtests (kappa = 0.5) and eight (32%) scored less than 5 on at least one of the subtests (kappa = 0.3). The initial median Digit Span, Comprehension, and Similarities subtest scores were 7, 5, and 6. By discharge, these improved to 8, 7, and 8, respectively.
CONCLUSIONS: This pilot study suggests that some patients with AMI may have difficulty processing information necessary to give informed consent for acute care research. Routine clinical evaluation may not detect this cognitive defect.