Rise in end tidal CO2 during thyroid surgery can be due to all, EXCEPT:
The anaphylactic reaction stas within minutes after exposure to a specific antigenis manifested by respiratory distress due to laryngeal edema and intense bronchospasm, thus leading to a fall in end tidal CO2 (question is rise in end tidal volume). This often leads to vascular collapse and shock. Ref: A rational basis for anesthesiology By Gianfranco Dal Santo, Page 610 - 612; Anaphylaxis and Hypersensitivity Reactions By Mariana C. Castells, Page 5-10; Interface of neurology and internal medicine By Jose Biller, Page 693 - 694; Complications in Surgery By Michael W. Mulholland, Gerard M. Dohey, Page 117.
Anaphylaxis
Malignant hypehermia
Thyroid storm
Neuroleptic malignant syndrome