Effect of four sedative and anesthetic protocols on quantitative thyroid scintigraphy in euthyroid cats.
OBJECTIVE
To determine the effect of sedation and anesthesia on thyroid and salivary gland uptake of technetium Tc 99m pertechnetate ((99m)TcO(4)) in euthyroid cats.


METHODS
6 euthyroid cats.


METHODS
Thyroid scintigraphy was performed by use of a high-resolution low-energy parallel-hole collimator after IV injection of 117 to 133 MBq (3.16 to 3.59 mCi) of (99m)TcO(4)(-). The procedure was performed 4 times on each cat during different sedative and anesthetic protocols in a rotating schedule as follows: propofol, ketamine-midazolam-atropine, ketaminemidazolam, and medetomidine. Regions of interest were drawn around thyroid and salivary glands and counts corrected for background and decay. Percentage of (99m)TcO(4)(-) uptake in salivary and thyroid glands and thyroid-to-salivary gland (99m)TcO(4)(-) uptake ratio were calculated at 20 and 40 minutes. Relative effects of anesthesia and sedation on salivary and thyroid gland (99m)TcO(4)(-) uptake were compared.


RESULTS
Significant differences among sedativeanesthetic protocols were found for thyroid gland (99m)TcO(4)(-) uptake, salivary gland (99m)TcO(4)(-) uptake, and thyroid-to-salivary gland (99m)TcO(4)(-) uptake ratio. Thyroid gland (99m)TcO(4)(-) uptake for the ketamine-midazolam protocol at 20 and 40 minutes after (99m)TcO(4)(-) administration was significantly higher than for the propofol protocol. A significant difference in salivary gland(99m) TcO(4)(-) uptake was found between ketamine-midazolam and ketamine-midazolam-atropine protocols at 40 minutes. The thyroid-to-salivary gland (99m)TcO(4)(-) uptake ratio for the ketamine-midazolam protocol was significantly higher at 40 minutes than for propofol or ketamine-midazolam-atropine protocols.


CONCLUSIONS
Sedation and anesthesia have a significant effect on thyroid and salivary gland (99m)TcO(4) uptake in euthyroid cats that may interfere with thyroid scintigraphic image interpretation.
Schaafsma
Irene A
IA
Division of Diagnostic Imaging, Department of Clinical, Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 10, NL-3508 TD, Utrecht, The Netherlands.
Pollak
Yvonne W E A
YW
Barthez
Paul Y
PY
D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D005260:Female; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007649:Ketamine / Q000494:pharmacology; D008297:Male; D020926:Medetomidine / Q000494:pharmacology; D008874:Midazolam / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology; D011877:Radionuclide Imaging / Q000662:veterinary*; D019275:Radiopharmaceuticals; D012469:Salivary Glands / Q000033:anatomy & histology / Q000187:drug effects; D013670:Sodium Pertechnetate Tc 99m; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000187:drug effects* / Q000378:metabolism
D000777:Anesthetics; D006993:Hypnotics and Sedatives; D019275:Radiopharmaceuticals; D007649:Ketamine; D001285:Atropine; D013670:Sodium Pertechnetate Tc 99m; D020926:Medetomidine; D008874:Midazolam; D015742:Propofol