# Does the addition of fentanyl premedication impact brown fat uptake in children undergoing a warming protocol for FDG PET?

## TL;DR

This study found that fentanyl premedication does not significantly reduce brown fat uptake in warmed children during FDG PET scans.

## Contribution

The study provides evidence that fentanyl premedication does not impact brown fat uptake in warmed pediatric patients undergoing FDG PET.

## Key findings

- Brown fat uptake frequency was similar between fentanyl-premedicated and non-premedicated groups (5.4% vs. 5.0%).
- Age and BMI were significantly associated with brown fat uptake, but not premedication status.
- No differences in brown fat intensity or location were observed based on premedication.

## Abstract

Fentanyl is used in some pediatric practices with a goal of suppressing 18F-fluorodeoxyglucose (18F-FDG) uptake in brown fat.

The purpose of this study was to examine the frequency, intensity, and distribution of brown fat uptake in warmed children undergoing 18F-FDG PET/CT with and without premedication with fentanyl.

This retrospective study included children (< 18 years old) who underwent 18F-FDG-PET from 2014 to 2024 at a center that routinely warms patients and uses intravenous fentanyl for brown fat suppression for most patients. Three radiologists assessed the presence, intensity, and location of brown fat uptake. Chi-square test and two-sample t-test were used to compare the demographics and brown fat uptake between premedication and non-premedication groups.

Among 873 18F-FDG-PETs, 595 (68%) were performed with fentanyl premedication and warming and 278 (32%) were conducted with warming alone. Brown fat uptake was observed in 46 (5.3%) FDG-PETs, 32/595 (5.4%) in the premedicated group and 14/278 (5.0%) in the non-premedicated group (P = 0.83). No differences were found in brown fat intensity or location based on premedication status. Age (14.5 vs. 8.5; P < 0.001) and BMI (20.1 vs. 17.7; P < 0.001) were significantly associated with brown fat uptake.

Fentanyl premedication does not significantly affect brown fat uptake frequency, intensity, or location in warmed children undergoing 18F-FDG-PET.

The online version contains supplementary material available at 10.1007/s00247-025-06381-5.