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Effects of small concentrations of isoflurane on some psychometric measurements
J Yoshizumi1, R W Marshall, L D Sanders
1Department of Anaesthetics, University of Wales College of Medicine, Health Park, Cardiff.
Abstract:
We have investigated the effects of 9.5% and 14.1% MAC concentrations of isoflurane on some psychometric measurements. Both concentrations depressed peak saccadic velocity (P < 0.01), choice reaction time (P < 0.05) and visual analogue scores for sedation (P < 0.05), but not the critical flicker fusion threshold. The incidence of errors in saccade tasks increased in a dose-related fashion, which made analysis of peak saccadic velocity less accurate at more than 10% MAC. The percentage error itself was an indicator of the depth of sedation. All the objective measures correlated highly with the estimated brain tension of isoflurane (r2 = 0.86-0.96), but not the visual analogue score for sedation (r2 = 0.51). This suggests that a combination of peak saccadic velocity, percentage error and choice reaction time is a potentially useful batch of tests to measure recovery from anaesthesia.
Insights
Isoflurane anesthesia impairs psychometric tests like saccadic velocity and reaction time. Objective measures, unlike sedation scores, effectively indicate anesthetic depth and recovery.
Area of Science:
- Anesthesiology
- Neuroscience
- Psychology
Background:
- Isoflurane is a common inhalation anesthetic.
- Assessing anesthetic depth and recovery is crucial for patient safety.
- Psychometric measurements offer objective ways to evaluate cognitive function under anesthesia.
Purpose of the Study:
- To investigate the effects of different isoflurane concentrations on psychometric performance.
- To determine the utility of objective tests in measuring anesthetic depth and recovery.
- To compare objective measures with subjective sedation scores.
Main Methods:
- Evaluating psychometric measurements including peak saccadic velocity, choice reaction time, and critical flicker fusion threshold.
- Administering isoflurane at 9.5% and 14.1% MAC concentrations.
- Correlating objective test results with estimated brain tension and visual analogue sedation scores.
Main Results:
- Both isoflurane concentrations significantly depressed peak saccadic velocity, choice reaction time, and visual analogue sedation scores.
- Error rates in saccade tasks increased with isoflurane dose, impacting accuracy.
- Objective measures showed high correlation with estimated brain isoflurane tension (r2 = 0.86-0.96).
Conclusions:
- Peak saccadic velocity, percentage error, and choice reaction time are sensitive indicators of isoflurane's effects.
- Objective psychometric tests are more reliable than subjective sedation scores for assessing anesthetic depth.
- A combination of these objective tests may serve as a valuable tool for monitoring recovery from anesthesia.