Effect of Desflurane Anesthesia on the [¹⁸F]FDG Metabolism in Nude Mice

Objectives:

Dynamic small animal PET studies in mice require often anesthesia to reduce motion related artifacts. The volatile anesthetic with the most rapid onset and offset and with low metabolism is desflurane, which is used for human general anesthesia, however not common in animals. Therefore, we evaluated the [¹⁸F]FDG distribution in awake and desflurane anesthetized NCIH292 tumor bearing nude mice.
Methods:
Fed NCIH292 tumor bearing NMRI nu/nu mice were divided into control mice (CM), which were freely moving in a cage at 27°C, and non-moving anesthetized mice (AM), which were kept under 9% desflurane in 0.2 L/min O2, 0.3 L/min air at 36°C. After 1 h adaption to the experimental setup the CM and AM were injected with [¹⁸F]FDG (5 MBq, i.v. bolus). Blood glucose was measured before the experiment, at 0.5 h and at 1 h. Then all mice were anesthetized and PET was measured over 30 min, the activity concentration data were calculated as SUV median (25%, 75% percentile).
Results:
There was no difference of [¹⁸F]FDG brain uptake between CM 1.9 (1.6, 2.2) and AM 1.9 (1.6, 2.3). An unexpected [¹⁸F]FDG increase was observed in the tumors of AM 2.47 (1.67, 3.17), which was higher than in the CM 0.81 (0.66, 1.14). The [¹⁸F]FDG uptake in the heart was also larger in the AM. As expected was the muscle (gluteus supeficialis, biceps femoris) uptake higher in the CM and the resulting tumor to muscle ratio was therefore in the CM 0.32 (0.28, 0.48) less than in the AM 3.9 (2.5, 6.8). The blood glucose was elevated in the AM only at 30 min post anesthesia induction with 10.3 (7.33, 11.8) mmol/L vs. CM 6.2 (5.8, 7.4) mmol/L.
Conclusions:
Desflurane affects the [¹⁸F]FDG uptake in the NMRI nu/nu mouse tissues. This has to be considered for glucose metabolic explorations with mice under anesthesia. An adaption period of one hour for the mice under anesthesia normalizes the elevated blood glucose often occurring after anesthesia induction stress. Thus, in terms of comparability and correct interpretation of results obtained from PET experiments with mice under anesthesia is a standardized experimental setup mandatory.