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The combined effect of age and premedication on the propofol requirements for induction by target-controlled infusion
M Olmos1, J A Ballester, M A Vidarte
1Servicio de Anestesiología y Reanimación, Unidad de Investigación, Hospital de Basurto, Bilbao, Spain.
Insights
Age and premedication significantly impact propofol anesthesia requirements. Combining midazolam and fentanyl reduced propofol needs, especially in older patients, highlighting the importance of these factors in anesthesia delivery.
Area of Science:
- Anesthesiology
- Pharmacology
Background:
- Propofol is a common anesthetic induction agent.
- Patient age and premedication influence anesthetic drug requirements.
Purpose of the Study:
- To investigate the combined effects of patient age and premedication on propofol requirements for anesthesia induction.
- To assess the hemodynamic effects of varying propofol doses based on age and premedication.
Main Methods:
- Prospective study of 180 patients divided into three age groups (20-39, 40-59, >59 years).
- Patients were randomized to receive no premedication, fentanyl, or midazolam plus fentanyl.
- Target-controlled infusion of propofol was used, with measurements of dose, time, and plasma concentration at hypnosis.
- Hemodynamic parameters (heart rate, blood pressure) were recorded.
Main Results:
- Propofol requirements and hemodynamic effects varied significantly with age and premedication.
- The combined effect of age and premedication was additive but not interactive.
- Midazolam-fentanyl premedication significantly reduced propofol needs across all age groups.
- Older patients (>60 years) receiving premedication required less propofol compared to other groups.
Conclusions:
- Age and premedication are crucial factors influencing propofol requirements for anesthesia induction.
- Target-controlled infusion systems should account for the combined effects of age and premedication for precise anesthesia delivery.
Abstract:
In this prospective study, we evaluated the combined influence of age and premedication on propofol requirements for the induction of anesthesia and their hemodynamic effects using a target-controlled infusion. We studied 180 patients separated into three age groups: 20-39 yr, 40-59 yr, and more than 59 yr. In each age group, patients were randomly allocated to receive either no premedication (n = 20), fentanyl (2 microg/kg) (n = 20), or midazolam (0.03 mg/kg) plus fentanyl (2 microg/kg) (n = 20). The concentration of propofol targeted for the induction was 5 microg/mL, to be reached in 2 min. The dose, time, and predicted plasma concentration of propofol at hypnosis were measured. Baseline and postinduction heart rate and arterial blood pressure were registered. Computer simulation was used to calculate the effect site propofol concentration at hypnosis. The concentration of propofol, effect site propofol concentration, time, and induction dose and their hemodynamic effect were significantly different among groups with respect to age and premedication. The combined effect of the two factors was additive, but without significant interaction. The propofol requirements were significantly less in the midazolam-fentanyl groups, regardless of age, and among the premedicated patients older than 60 yr compared with the other age groups. We conclude that the combined effect of age and premedication on the requirements of propofol for the induction of anesthesia should be considered when the concentration is targeted with a target-controlled infusion system.