Does intravenous induction dosing among patients undergoing gastrointestinal surgical procedures follow current recommendations: a study of contemporary practice

Study objective: It is recommended to correct intravenous induction doses by up to 50% for patients older than 65 years. The objectives were to determine (a) the degree to which anesthesia providers correct induction doses for age and (b) additionally adjust for American Society of Anesthesiologists physical status (ASA-PS) class (severity of illness) and (c) whether postinduction hypotension is more common among patients aged >65.

Design: Retrospective chart review.

Setting: Academic medical center.

Patients: A total of 1869 adult patients receiving general anesthesia for GI surgical procedures from February 2013 to January 2014.

Measurements: Patients were divided into 3 age groups (age <65, 65-79, ≥80 years) and then further stratified into ASA-PS class (I/II vs III/IV). Multiple pairwise comparisons were conducted using Welch t tests for continuous variables to determine whether dosing was different for the older groups vs the younger group; separate analyses were performed within and across ASA-PS class. This approach was also used to determine differences in mean arterial pressure change in the older groups vs the younger group, whereas the rates of hypotension among different age groups were compared by Cochran-Armitage trend test.

Main results: No significant decrease in dosing between age groups was observed for fentanyl and midazolam. For propofol, there was a significantly lower dosing for older patients: 17% for patients aged 65-79 and 29% for those aged >80, which was still in less than the recommendations. An inverse relationship was observed between propofol dosing and ASA-PS class, but no consistent relationship was noted for fentanyl and midazolam. There were a significantly larger drop in mean arterial pressure and a greater likelihood of hypotension following induction in patients aged 65-79 years and >80 years as compared with those aged <65 years.

Conclusions: This study shows that the administered dose of anesthetic induction agents is significantly higher than that recommended for patients older than 65 years. This failure to age-adjust dose may contribute to hypotensive episodes.