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Malignant Hyperthermia

Homepage: EMNote.org ■ 🚩Membership: https://tinyurl.com/joinemnote 🚩ACLS Lecture: https://tinyurl.com/emnoteacls Malignant Hyperthermia Severe reaction triggered by specific anesthesia drugs. Main cause: specific anesthesia drugs. Inherited skeletal muscle issue. Runs in families (MHS - Malignant Hyperthermia Susceptibility). Stems from gene mutation. Most often involves RyR1 gene. Mechanism & Symptoms Timing Mechanism: uncontrolled calcium release in skeletal muscle cells. Leads to sustained muscle contraction (muscles can't relax). Depletes ATP energy stores. Overall metabolic activity skyrockets. Symptoms appear during procedure or delayed postoperatively. Hallmarks & Early Signs Hallmarks: rapid temperature increase, muscle rigidity, fast heart rate. Rapid temperature increase = Hyperthermia (can be later sign). Muscle rigidity / severe stiffness / spasms. Tacocardia (fast heart rate) often presents early. Breathing difficulties: rapid/shallow breathing. Oxygen levels drop, carbon dioxide levels rise. High end tidal CO2 often earliest sign. Irregular heart rhythms possible (arrhythmias). Other Signs & Rarer Triggers Excessive sweating. Patchy skin color / modeling. Rarer triggers: intense physical activity (heat/humidity), viral illness, certain statin medications (less common). Diagnosis Definitive test: Caffeine Halothane Contracture Test (CHCT). Involves muscle biopsy (fresh skeletal muscle sample). Tests muscle reaction to caffeine and halothane. Increasingly used: Genetic testing. Looks for mutations in RyR1, CACNA1S, STAC3 genes. Genetic testing can be expensive, access not universal. High clinical suspicion based on signs/symptoms vital for timely diagnosis. Immediate Treatment (Suspected MH) Number 1: Intravenous Dantrolene right away. Stop triggering anesthetic agent immediately. Turn off volatile anesthetics. Stop succinylcholine. Hyperventilate patient with 100% oxygen. Immediate Treatment (Suspected MH) Flush out inhaled agents, manage high CO2. Switch to safe non-triggering anesthetics if surgery must continue. Use IV agents: propofol, opioids, non-depolarizing muscle relaxants (if needed). TVIA (Total Intravenous Anesthesia) the way to go. Finish surgery as quickly as safely possible. Supportive Care Active cooling essential for high body temperature. Cooling blankets, cold IV fluids, gastric lavage with cold water (if needed). Correct metabolic chaos: treat acidosis (sodium bicarbonate based on blood gases). Address hypoxemia. Supportive Care Manage cardiac arrhythmias (standard ACLS). Avoid calcium channel blockers. Calcium channel blockers contraindicated - can worsen hyperkalemia, cause CV collapse. Amiodarone or lidocaine preferred for ventricular arrhythmias. Maintaining kidney function critical. Aim for urine output at least 2 ml/kg/hour. Supportive Care Dantrolene formulation (Revonto) has mannitol which helps urine flow. Rhinoex (newer formulation) has less mannitol, need attention to hydration/output. Severe Complications (Untreated) If not treated quickly, complications severe. Major concern: Rhabdomyolysis (muscle breakdown). Releasing damaging substances. Leads to kidney damage / acute renal failure. Blood clotting issues: DIC (Disseminated Intravascular Coagulation) - clotting and bleeding problems. Severe Complications (Untreated) Potential brain damage from hypoxia or ischemia. Cardiac arrest, heart failure. Pulmonary edema (fluid in lungs). Skeletal muscle degeneration longer term. Ultimately, death is real possibility if not managed aggressively.