Changes in visual and auditory response time during conscious sedation with propofol.

Area of Science:

• Anesthesiology
• Pharmacology
• Neuroscience

Background:

• Investigated the relationship between increasing sedation and response times to visual or auditory stimuli.
• Assessed the Observer's Assessment of Alertness/Sedation (OAA/S) scale at loss of response.
• Utilized a push-button device for response time measurements.

Purpose of the Study:

• To determine if visual or auditory response time increases with sedation.
• To compare the point of loss of response to visual versus auditory stimulation.
• To evaluate the OAA/S score at the first loss of response.

Main Methods:

• Experiment 1: Increased propofol target plasma concentration (CPT) and applied simultaneous visual/auditory stimulation to 19 patients.
• Experiments 2 & 3: Infused propofol in 30 patients, increasing effect-site concentration (CE) and applying visual or auditory stimulation.
• Measured visual response time (VRT), auditory response time (ART), propofol CE, total propofol dose, and OAA/S score.

Main Results:

• Visual response was lost before auditory response in 84.2% of patients.
• Both VRT and ART linearly increased with increasing propofol CE.
• Loss of visual response occurred at a lower CE (1.2 μg/mL) and propofol dose (57.9 mg) than auditory response (1.4 μg/mL, 71.6 mg).
• Median OAA/S scores at loss of response were 4 for visual and 3 for auditory stimuli.

Conclusions:

• Response times to both visual and auditory stimuli are prolonged linearly with increasing sedation.
• Visual response appears to be lost earlier than auditory response during propofol-induced sedation.
• Visual response monitoring may be a valuable tool for assessing conscious sedation levels.