Background and Objectives: Patients have right to receive complete information before any operation. There was no such study in Thailand. This study aimed to determine prevalence and its affecting factors of the patients receiving complete information before signing in preoperative informed consent.

Methods: This descriptive study had study population as operative patients at a tertiary hospital in Khon Kaen province. Random samples of 80 patients were interviewed with oral questionnaire. Completeness of information was defined to cover all six components in the preoperative informed consent (surgical method, benefit, adverse effect, risk, alternative treatment and possibility of emergency-additional-surgical procedure during the operation).

Results: Response rate was 100.0%. The patients were 38.8% male with average age of 51.9 years. They got operation at department of surgery, gynecology and orthopedics for 47.5%, 26.3% and 26.3% respectively. Prevalence of the patients receiving complete information was 17.5% (95%CI: 10.2%, 28.0%). The patients were informed about surgical method, benefit, adverse effect, risk, alternative treatment and possibility of emergency-additional-surgical procedure during the operation for 93.8%, 65.0%, 60.0%, 57.5%, 57.5% and 45.0% respectively. Factors that might associate with the completeness were patient's capability to remember the received information (p-value = 0.039), department of operation (p-value = 0.059) and duration of explaining (p-value = 0.062).

Conclusion: Less than one-fifth of the patients received complete information before signing in preoperative informed consent. So a physician should check components of giving information with the preoperative informed consent. Duration of explanation should be adjusted to condition of each patient.

Keywords: preoperative informed consent, completeness, information, signing