Malignant hyperthermia (MH) is a rare but life-threatening surgical complication that seems to turn the effects of general anesthesia upside down. Instead of relaxing, muscles become rigid, releasing large amounts of acid and potassium into the blood. Instead of a normal slowing of breathing, respirations quicken, and end-tidal CO2 rises. Other signs include tachycardia and a spike in body temperature that can reach over 110°F. Without rapid treatment, MH can lead to cardiac arrest and death.