Mvs. Kumar et al., Differential diagnosis of thyroid crisis and malignant hyperthermia in an anesthetized porcine model, ENDOCRINE R, 25(1), 1999, pp. 87-103
The intra-operative differential diagnosis between thyroid crisis and malig
nant hyperthermia can be difficult. Also stress alone can trigger MH. The p
urposes of this study were: 1) to investigate the metabolic and hemodynamic
differences between thyroid crisis and MH, 2) determine how thyroid crisis
affects the development of MH, and 3) determine if the stress of thyroid c
risis can trigger MH in susceptible individuals. We studied MH susceptible
and normal swine. Two groups of animals (MH susceptible and normal) were in
duced into thyroid crisis (critical core hyperthermia, sustained tachycardi
a and increase in oxygen consumption) by pretreatment with intraperitoneal
triiodothyronine (T-3) followed by large hourly intravenous injections of T
-3. Two similar groups were given intravenous T-3 but no pretreatment. Thes
e animals did not develop thyroid crisis and served as controls. Thyroid cr
isis did not result in metabolic changes or rigidity characteristic of an a
cute episode of MH. When the animals were subsequently challenged with MH t
riggering agents (halothane plus succinylcholine) dramatic manifestations o
f fulminant MH episodes (acute serious elevation in exhaled carbon dioxide,
arterial CO2, rigidity and acidemia) were noted only in the MH susceptible
animals. Although thyroid crisis did not trigger MH in the susceptible ani
mals it did decrease the time to trigger MH (14.1 rt 7.2 minutes versus 47.
2 +/- 17.7 minutes, p< 0.01) in susceptible animals. Hormone induced elevat
ions in temperature and possibly other unidentified factors during thyroid
crisis may facilitate the triggering of MH following halothane and succinyl
choline challenge.