Differential Diagnosis of Thyroid Crisis and Malignant Hyperthermia in an Anesthetized Porcine Model

Abstract

The intra-operative differential diagnosis between thyroid crisis and malignant hyperthermia can be difficult. Also stress alone can trigger MH. The purposes 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 crisis can trigger MH in susceptible individuals. We studied MH susceptible and normal swine. Two groups of animals (MH susceptible and normal) were induced into thyroid crisis (critical core hyperthermia, sustained tachycardia and increase in oxygen consumption) by pretreatment with intraperitoneal triiodothyronine (T3) followed by large hourly intravenous injections of T3. Two similar groups were given intravenous T3 but no pretreatment. These animals did not develop thyroid crisis and served as controls. Thyroid crisis did not result in metabolic changes or rigidity characteristic of an acute episode of MH. When the animals were subsequently challenged with MH triggering agents (halothane plus succinylcholine) dramatic manifestations of 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 animals it did decrease the time to trigger MH (14.1 +/- 7.2 minutes versus 47.2 +/- 17.7 minutes, p < 0.01) in susceptible animals. Hormone induced elevations in temperature and possibly other unidentified factors during thyroid crisis may facilitate the triggering of MH following halothane and succinylcholine challenge.

The heat is on: Molecular mechanisms of drug-induced hyperthermia

“…However, unlike sympathomimetic hyperthermia, where activation of the SNS is the primary culprit behind massive heat generation, whether or not SNS and serotonergic modulation is causal or merely correlative in MH is not clear. Similar to what has been observed with MDMA toxicity in rodent models, MH susceptible adrenalectomized pigs were also more resistant to MH toxicity, 109 and treatment with thyroid hormone led to an earlier onset of MH in pigs, 110 implicating activation of the hypothalamic-pituitary-adrenal and -thyroid axes in MH. Despite the similarities, a recent study done by Schutte et al 111 .…”

Rhabdomyosarcoma Associated with Core Myopathy/Malignant Hyperthermia: Combined Effect of Germline Variants in RYR1 and ASPSCR1 May Play a Role

“…Thyrotoxicosis during surgical manipulation is a differential diagnosis of MH. Both present with tachycardia, tachypnea, and hyperthermia; however, typically only MH presents with hypercarbia, muscle rigidity, acidosis/hyperkalemia, and rhabdomyolysis due to excessive calcium release from the SR [5,6,17,18].…”

Perioperative temperature elevation: not all hyperthermia is malignant hyperthermia

“…In a swine model, thyroid storm was demonstrated to have a gradual rise in ETCO2 and temperature and did not trigger MH. The authors hypothesized that hormonally induced rises in temperature may ease the likelihood of triggering MH .…”