Malignant Hyperthermia Crisis Management (AAGBI 2020)

Algorithm Steps

1. ▶

   Start

   Suspect Malignant Hyperthermia

   Clinical signs during/after anesthesia with triggering agents (volatile anesthetics, succinylcholine)

   1. ◆

      Decision

      Clinical Signs Present?

      Early signs: unexplained tachycardia, rising ETCO2, muscle rigidity. Late: hyperthermia, arrhythmias, acidosis

      • Unexplained rapid rise in ETCO2
      • Unexplained tachycardia
      • Masseter muscle rigidity after succinylcholine
      • Generalized muscle rigidity
      • Temperature rise (may be late sign)
      • Arrhythmias, unstable BP
      • Dark blood in surgical field
      • Cola-colored urine (myoglobinuria)
      1. ●

         Action

         STOP All Trigger Agents IMMEDIATELY

         Discontinue volatile anesthetics and succinylcholine

         • Turn OFF vaporizer
         • Increase fresh gas flow to 10+ L/min
         • Do NOT change anesthesia machine/circuit (wastes time)
         • Switch to IV anesthesia (propofol, opioids)
         • Hyperventilate with 100% O2
         1. ●

            Action

            Call for Help

            Activate MH protocol and get dantrolene

            • Declare MH emergency
            • Call MHAUS Hotline: 1-800-644-9737 (US)
            • Assign roles: mixing dantrolene, labs, cooling
            • Send for MH cart/dantrolene immediately
            • Delegate tasks - requires team effort
            1. ●

               Action

               Administer Dantrolene

               Initial dose: 2.5 mg/kg IV bolus

               • Initial: 2.5 mg/kg IV push
               • Mix each 20mg vial with 60mL sterile water (shaken, not stirred)
               • Repeat 1 mg/kg every 5-10 min until signs resolve
               • No maximum dose - continue until effective
               • Typical total: 2.5-10 mg/kg
               • Monitor for muscle weakness, respiratory depression
               1. ⚠

                  Warning

                  ⚠️ CONTRAINDICATION

                  Do NOT give calcium channel blockers with dantrolene - causes severe hyperkalemia and cardiovascular collapse

               2. ●

                  Action

                  Supportive Measures

                  Manage hyperkalemia, acidosis, arrhythmias

                  • Sodium bicarbonate 1-2 mEq/kg for acidosis
                  • Calcium chloride 10-20 mg/kg for hyperkalemia
                  • Insulin/glucose (10U regular + 50mL D50)
                  • Treat arrhythmias (avoid calcium channel blockers with dantrolene!)
                  • Insert Foley - monitor for myoglobinuria
                  1. ●

                     Action

                     Laboratory Monitoring

                     Serial labs every 15-30 minutes initially

                     • ABG (acidosis, hypercarbia)
                     • Potassium (hyperkalemia common)
                     • CK (will rise - peak 12-24 hours)
                     • Myoglobin (serum and urine)
                     • Lactate
                     • Coagulation studies (DIC possible)
                     1. ◆

                        Decision

                        Response to Dantrolene?

                        Signs of improvement: decreasing ETCO2, HR, muscle rigidity

                        1. ●

                           Action

                           Continue Dantrolene

                           Repeat 1 mg/kg every 5-10 min

                           • Continue until all signs resolve
                           • No upper limit - give what's needed
                           • Prepare more dantrolene
                        2. ●

                           Action

                           ICU Admission

                           All MH patients require ICU monitoring

                           • Continue dantrolene 1 mg/kg IV q4-6h x 24-48h
                           • Monitor for recrudescence (25% of cases)
                           • Serial CK, K+, renal function
                           • Urine output >2 mL/kg/hr (prevent AKI)
                           • Mannitol/furosemide if myoglobinuria
                           • Refer for MH susceptibility testing
                           1. ✓

                              Outcome

                              MH Crisis Managed

                              Continue monitoring, arrange genetic testing

               3. ●

                  Action

                  Active Cooling

                  Target temperature <38.5°C

                  • Cold IV saline (not through blood warmer)
                  • Ice packs to groin, axillae, neck
                  • Cooling blanket
                  • Gastric/bladder lavage with cold saline if refractory
                  • STOP cooling at 38°C to prevent overshoot