Signs of malignant hyperthermia include increased CO2 production or minute ventilation, increased O2 consumption, increased cardiac output, increased HR, increased BP, arrhythmias, rigidity, and temperature elevation.
MH is commonly associated with a mixed metabolic and respiratory acidosis on arterial blood gas. This is caused by increased lactic acid production coupled with inability to increase minute ventilation adequately to remove all CO2. Alterations in skeletal muscle membrane permeability lead to elevations in serum potassium, sodium, calcium, phosphate, myoglobin, and creatine kinase. Unlike MH, thyroid storm is typically not associated with rigidity, elevated CK, or lactic acidosis.
In contrast to MH, hypokalemia is very common in thyroid storm. Also unlike the typical intraoperative presentation of MH, thyroid storm generally develops postoperatively.