The Effect of Preoperative Heart Rate and Anxiety on the Propofol Dose Required for Loss of Consciousness

BACKGROUND: Conflicting results have been reported on the effect of anxiety on the propofol dose required for inducing loss of consciousness (LOC). The hemodynamic effects of anxiety, increased heart rate (HR), and cardiac output may account for these discrepancies. We therefore designed this study to address, first, the effect of perioperative HR on propofol dose required for LOC and, second, the effect of perioperative anxiety on HR. METHODS: Forty-five ASA physical status I-II female patients undergoing gynecological surgery were studied. Anxiety was assessed in the operating room with the State-Trait Anxiety Inventory (STAI)-state Spielberger scale (situational anxiety). After HR recording, anesthesia was induced with a 200-mL/h 1% propofol infusion with the Base Primea (R) pump (Fresenius-Vial, Brezins, France) until LOC. The propofol dose was recorded at the time of LOC. Relationships between STAI-state and HR versus propofol dose at LOC were tested with the Spearman test with a P value of 0.01. RESULTS: A significant relationship was observed between HR and propofol dose at LOC (rho = 0.487, P = 0.0012) but not between STAI-state and propofol dose (rho = 0.330, P 0.0306). However, a significant relationship was observed between STAI-state and HR (rho = 0.462 and P = 0.0054). CONCLUSION: Increased perioperative HR is associated with increased propofol dose required for LOC. Perioperative anxiety accounts for increased HR. (Anesth Analg 2010;110:89-93)