Protocol Understanding and Anxiety in Perioperative Clinical Trial Patients Approached for Consent on the Day of Surgery

OBJECTIVE: To determine whether approaching patients for consent on the day of surgery impairs understanding or produces unacceptable anxiety compared with obtaining consent before the day of surgery. PATIENTS AND METHODS: We assessed the effect of the timing of obtaining consent for a moderate- to high-risk factorial trial of clonidine and aspirin in patients having noncardiac surgery. Between February 1, 2011, and November 31, 2011, 2 study personnel used the same standardized script to recruit patients before the day of surgery or on the day of surgery. Patients eligible for the trial were preferentially approached to obtain consent before the day of surgery in the preoperative clinic. Patients who did not attend the preoperative clinic or could not be approached that day were approached for consent on the day of surgery. We evaluated anxiety before and after the trial was discussed, protocol knowledge, consent rates, and perceived obligation to participate. All comparisons were adjusted for differences in potentially confounding variables using inverse propensity score weighting. RESULTS: Patients approached on the day of surgery compared with before the day of surgery had noninferior understanding of the comprehension score (adjusted mean difference, -0.19; 90% CI, -0.47 to 0.10; P<.001 for noninferiority) and a noninferior mean increase in the postapproach anxiety score (adjusted mean difference, 0.19; 90% CI, -0.29 to 0.68; P=.003 for noninferiority). Perceived obligation to participate was not greater on the day of surgery (adjusted mean difference, 0.09; 95% CI, -0.21 to 0.40; P=.57 for superiority); however, consent rates were significantly lower (31% vs 59%; odds ratio, 0.49; 90% CI, 0.33 to 0.72; P=.46 for noninferiority). CONCLUSION: Approaching patients to obtain consent to participate in a perioperative interventional trial on the day of surgery does not compromise essential elements of the consent process. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01082874.