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Updated: May 8, 2026

Optogenetic Activation of Afferent Pathways in Brain Slices and Modulation of Responses by Volatile Anesthetics
Published on: July 23, 2020
A simple method for evaluation of the uptake of isoflurane and its comparison with the square root of time model
Ashish Bangaari1, Nidhi Bidyut Panda, Goverdhan Dutt Puri
1Department of Anaesthesiology and Pain Medicine, Fellow Liver Transplant Anaesthesia, Asan Medical Centre, Seoul, Korea.
Background:
The square root of time (SqRT) model had been used to predict the uptake of volatile agents.
Methods:
We studied the rate of uptake of isoflurane in 10 patients using liquid isoflurane infusion through syringe pump into the closed circuit. The infusion rates were titrated to maintain a constant end tidal concentration of isoflurane of 1.5%. The predicted uptake values were also calculated from the square root principle and compared with the derived uptake.
Results:
The observed rate of uptake was higher than predicted from the Lowe and Ernst equation (P<0.001). There exists considerable inter-individual variability in uptake pharmacokinetics and it showed statistically significant correlation with ideal body weight, body weight (P<0.01), body surface area, and body weight¾ from 30 min of start of isoflurane infusion (P<0.05).
Conclusion:
SqRT model is inaccurate in predicting isoflurane uptake and underestimates it during closed circuit anaesthesia.
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