The Impact of Preoperative Positive Suggestions on Dreaming With Intravenous Sedation: A Randomized Controlled, Blinded Trial

BACKGROUND: Drug-induced dreams during intravenous sedation vary by pharmacological agent and influence patient experiences, yet the role of preoperative positive suggestions in modulating these dreams is unclear. This study aimed to investigate the impact of preoperative positive suggestions on drug-induced dream recall (DIDR) frequency, dream content, and subjective perceptions during sedation with propofol or ketamine. METHODS: This prospective, randomized, controlled, double-blinded trial with a 2 × 2 factorial design was conducted at a single tertiary university hospital in South Korea from September 2024 to January 2025. A total of 188 adults (American Society of Anesthesiologists [ASA] physical status I-III), aged 20 to 65, undergoing elective upper extremity surgery with sedation via brachial plexus block were enrolled, excluding those with cognitive or psychiatric disorders or recent sedative use. Patients were randomly assigned to 4 groups: propofol with suggestions (P-S; n = 47), propofol without suggestions (P-NS; n = 47), ketamine with suggestions (K-S; n = 47), and ketamine without suggestions (K-NS; n = 47). The suggestion intervention involved providing 8 pleasant dream scenarios preoperatively. The primary outcome was DIDR frequency (binary: yes/no). Secondary outcomes included dream content, subjective dream perceptions, and predictors of DIDR. RESULTS: In the intention-to-treat analysis (n = 188), DIDR frequencies were 21.3% (P-NS), 25.5% (P-S), 36.2% (K-NS), and 44.7% (K-S), with a significant difference between K-S and P-NS ( P = .010). Factorial analysis showed a significant main effect of drug type (ketamine versus propofol: odds ratio [OR] = 2.14, 95% confidence interval [CI], 1.23-3.72; P = .007), but no main effect of suggestions (OR = 1.16, 95% CI, 0.67-2.01; P =.598) or interaction ( P = .818). DIDR frequencies were 23.4% (propofol groups: P-NS and P-S) vs 40.4% (ketamine groups: K-NS and K-S) ( P = .002), and 35.1% (suggestion groups: P-S and K-S) vs 28.7% (no-suggestion groups: P-NS and K-NS) ( P = .308). A significant difference was noted between K-S and P-NS (44.7% vs 21.3%; P = .010). Ketamine increased emotional intensity ( P = .0071 versus P-NS; P = .003 vs P-S) and dream strangeness ( P = .0071 versus P-NS; P = .0071 versus P-S) versus propofol. Suggestions enhanced dream pleasantness in both drug groups ( P = .002 versus P-NS; P = .001 versus K-NS; P = .0071 versus K-S). CONCLUSIONS: Preoperative suggestions did not increase DIDR frequency or alter dream content but improved dream pleasantness, indicating potential psychological benefits during sedation.