Author

Jia Liu

Date of Award

January 2015

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

David G. Silverman

Subject Area(s)

Medicine

Abstract

Background:

It has been shown that elderly patients have decreased anesthetic requirements due to age-related changes in pharmacokinetics, pharmacodynamics and drug sensitivity. Previous work has also shown that anesthetic dosing is often not being rigorously corrected for age.

Purpose:

To determine whether the dosing of intravenous (IV) induction anesthetics in patients undergoing gastrointestinal (GI) surgeries are corrected appropriately for age.

Methods:

We retrospectively reviewed the intraoperative electronic anesthetic records of 1868 adult patients (aged ≥ 18 yrs) receiving general anesthesia for GI surgeries from February 2013 - January 2014. Patients undergoing multiple procedures, those requiring temporary abdominal closure or rapid sequence induction were excluded from this study. Change in mean arterial pressure (MAP) was calculated as the difference between pre- and post-induction MAP. Post-induction MAP was measured within the first 10 minutes of induction. Statistical analysis was done using T-test and one-way ANOVA.

Results:

There was a significant decrease in dosing of fentanyl, propofol and midazolam with increasing age (p<0.05). There was a significantly larger drop in MAP following induction of anesthesia in older patients (ages > 70 yrs) despite the decrease in weight-based dosing (p<0.01). Patients aged 70 yrs and under had a mean decrease in MAP of 17.16 ± 19.51 mm Hg, whereas patients over the age of 70 had a mean decrease in MAP of 23.23 ± 25.09 mm Hg. We noted a significant decrease in dosing of fentanyl and propofol with increasing ASA class (p-values <0.01). No significant difference in dosing of midazolam was seen based on ASA class (p=0.47). For ASA III and IV patients (n=792), there was no significant change in dosing of fentanyl based on age.

Conclusion:

The results of this study show that there is a significant age-related decrease in the induction dosing of fentanyl, propofol and midazolam. This change remains significant for propofol after correcting for ASA class. However, the age-corrected doses for these induction anesthetics tend to be either higher, or at the upper limit, of recommended dosing for the elderly patients, which may explain a larger drop in MAP following induction in elderly vs. younger patients.

Comments

This is an Open Access Thesis.

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