The Effects of Anesthesia and Surgery on Thyroid Function Tests in Dogs

Background: Many non-thyroidal factors affect thyroid function tests. Anesthesia and surgery have been documented to affect thyroid function tests in humans but have not been extensively studied in dogs. Hypothesis: Anesthesia alone and anesthesia combined with surgery will affect thyroid function tests in dogs. Animals: 15 euthyroid mongrel dogs. Methods: Dogs were assigned to one of three groups: control, general anesthesia, and general anesthesia plus abdominal exploratory surgery. Blood samples were collected from each dog immediately prior to pre-medication, 20 minutes after pre-medication, 55 minutes after anesthesia induction, once daily for an additional 6 days, and 14 days post-procedures. Sampling was performed at identical times in the control group. Thyroxine (T4), free T4 (fT4) by equilibrium dialysis, triiodothyronine (T3), reverse T3 (rT3) and thyroid-stimulating hormone (TSH) concentrations were measured in all samples. Results: Results of all thyroid function tests were not significantly different between control and anesthesia groups. Serum T3 for the surgery group decreased significantly from baseline compared to the control and anesthesia groups at multiple times. Serum T4 and rT3 for the surgery group increased significantly from baseline compared to the control and anesthesia groups at multiple times. Serum fT4 for the surgery group increased significantly from baseline compared to the control and anesthesia groups at 48 hours only. Conclusions and Clinical Importance: Surgery has a significant effect on thyroid function tests, while the anesthetic protocol used in this study does not. Because serum T4 and fT4 concentrations increased rather than decreased, evaluating these hormones following surgery is unlikely to lead to a misdiagnosis of hypothyroidism in euthyroid dogs.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biomedical and Veterinary Sciences

Department dc:contributor.department

Biomedical and Veterinary Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2007

Author dc:creator

• Wood, Melinda Anne

Chair dc:contributor.committeechair

• Panciera, David L.

Committee members dc:contributor.committeemember

• Berry, Stephanie H.
• Monroe, William E.

• non-thyroidal illness
• isoflurane
• hypothyroidism
• Thyroxine

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-07122007-163551

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43705