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anesthesia.malignant-hyperthermia.core.v1PRODUCTION
anesthesia.malignant-hyperthermia.core.v1

Malignant Hyperthermia Crisis

critical_careacuteadultpediatric
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Detailed

Confirm perioperative MH crisis scope — pharmacogenetic hypermetabolic syndrome after halogenated volatile or succinylcholine in genetically susceptible patient (MHAUS 2023)

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volatile or succinylcholine exposure with hypermetabolic signs

Patient inputs (13)

Pediatric dantrolene dosing identical mg/kg; total cumulative dose differs (MHAUS 2023)

Sinus tachycardia / dysrhythmia track hypermetabolism (Larach 2010)

Mixed respiratory + metabolic acidosis confirms hypermetabolism (MHAUS 2023)

Hyperkalemia from rhabdomyolysis drives arrhythmia + dialysis decision (MHAUS 2023)

CK peak documents rhabdomyolysis severity (Larach 2010)

Temperature trajectory drives severity grading and cooling threshold (Larach 2010)

Hypercarbia is earliest sign; minute-ventilation-adjusted EtCO2 trend critical (MHAUS 2023)

Sevoflurane / isoflurane / desflurane / halothane are triggers — must STOP (MHAUS 2023)

Succinylcholine is a trigger — masseter spasm is hallmark; document timing (MHAUS 2023)

Dantrolene initial 2.5 mg/kg IV bolus; mg/kg-based throughout (MHAUS 2023)

Family RYR1/CACNA1S history changes preop trigger-free anesthetic plan (Riazi 2018)

Myoglobinuria drives renal protection / mannitol / bicarb plan (MHAUS 2023)

DIC is a late complication; screen at presentation and serial (MHAUS 2023)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (4)

4 need judgement
  • informationallife_threateningmh_fulminant_crisis
    Larach Clinical Grading Scale rank "almost certain" or "very likely" — hypercarbia + acidosis + rigidity + temperature >39C + rhabdomyolysis (Larach 2010)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateninghyperkalemia_with_arrhythmia_in_mh
    K+ >=6.5 with hyperkalemic ECG changes (peaked T, widened QRS, sine wave) during MH crisis (MHAUS 2023)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseveremasseter_muscle_rigidity_post_sux
    Masseter muscle rigidity after succinylcholine — early MH warning, especially in pediatric (MHAUS 2023)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseveremh_recrudescence
    Recurrence of MH signs within 24h of initial crisis (occurs up to 25%) (MHAUS 2023)
    Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

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Recommended regimen

Malignant Hyperthermia Crisis — MHAUS 2023 sequence: STOP triggers, dantrolene 2.5 mg/kg, treat hyperkalemia + acidosis + dysrhythmia + myoglobinuria
axis: mh_crisis_treatment_pathwaystep 1 - Step 1 — Trigger discontinuation + activate MH protocol (single most important action)
Selected step "Step 1 — Trigger discontinuation + activate MH protocol (single most important action)" — MH suspected during anesthesia (hypercarbia + tachycardia + masseter or generalized rigidity + acidosis)
  • discontinue_volatile_anesthetics_immediately
    first line
    trigger_discontinuation
    STOP all sevoflurane/isoflurane/desflurane/halothane • inhaled • immediate
    triggers: MH_suspected
    Removing trigger gas halts ongoing calcium release at the ryanodine receptor (MHAUS 2023)
  • discontinue_succinylcholine_and_avoid_redose
    first line
    trigger_discontinuation
    DO NOT redose succinylcholine • IV • immediate
    triggers: MH_suspected
    Succinylcholine is a depolarizing trigger; switch to non-depolarizing NMB (rocuronium/vecuronium) (MHAUS 2023)
  • switch_to_tiva_propofol_remifentanil
    first line
    trigger_free_anesthetic
    Propofol infusion + opioid (remifentanil or fentanyl) • IV • continuous
    triggers: MH_suspected
    Maintain anesthesia without halogenated agents (MHAUS 2023)
  • hyperventilate_100_percent_o2_clean_circuit
    first line
    ventilation_supportive
    100% FiO2 at >=10 L/min flush; consider activated charcoal filters on anesthesia circuit • inhaled • continuous
    triggers: MH_suspected
    Wash out residual volatile; supports increased metabolic O2 demand (MHAUS 2023)
  • call_mhaus_hotline_24_7
    first line
    expert_consultation
    MHAUS Hotline 1-800-644-9737 (US/Canada) • phone • once
    triggers: MH_suspected
    Live expert MH guidance during crisis (MHAUS 2023)

inpatient playbook — drug actions (7)

  1. 1. STOP volatile anesthetics + STOP succinylcholine + switch to TIVA
    discontinue • inhaled/IV • immediate
    trigger: MH suspected (MHAUS 2023)
    Remove inciting trigger first (MHAUS 2023)
  2. 2. dantrolene
    rxcui 3105
    2.5 mg/kg IV bolus, repeat q5-10 min until signs resolve • IV • q5-10 min titrated
    trigger: MH suspected (MHAUS 2023)
    Definitive RYR1 antagonist (MHAUS 2023)
  3. 3. sodium bicarbonate
    rxcui 36676
    1-2 mEq/kg IV titrated to pH • IV • PRN pH<7.2
    trigger: Severe metabolic acidosis (MHAUS 2023)
    Acidosis correction + K+ shift (MHAUS 2023)
  4. 4. insulin + dextrose
    rxcui 253182
    10 units IV regular + 25 g (50 mL D50) • IV • q15-30 min PRN
    trigger: K>5.5 OR hyperkalemic ECG (MHAUS 2023)
    Intracellular K+ shift (MHAUS 2023)
  5. 5. amiodarone
    rxcui 703
    150 mg IV bolus + 1 mg/min infusion • IV • continuous post-bolus
    trigger: VT/VF (MHAUS 2023)
    Preferred antiarrhythmic; AVOID CCB with dantrolene (MHAUS 2023)
  6. 6. mannitol
    rxcui 6628
    0.25 g/kg IV • IV • PRN UOP<2 mL/kg/h
    trigger: Myoglobinuria / oliguria (MHAUS 2023)
    Force myoglobin diuresis (MHAUS 2023)
  7. 7. furosemide
    rxcui 4603
    20-40 mg IV • IV • PRN
    trigger: Volume-overloaded oliguria refractory to mannitol (MHAUS 2023)
    Selective add-on diuretic (MHAUS 2023)

Auto-drafted A&P note

inpatient

Subjective

- Possible entry pathways: Unexplained rising EtCO2 despite increased minute ventilation (MHAUS 2023); Masseter muscle rigidity / generalized rigidity after succinylcholine (MHAUS 2023); Rapid rise in core temperature (>=1-2C in 5 min, late finding) (MHAUS 2023).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Malignant Hyperthermia Crisis** (anesthesia.malignant-hyperthermia.core.v1).
Phenotype framing: Distinguish MH from thyroid storm, pheochromocytoma, neuroleptic malignant syndrome, sepsis, serotonin syndrome, iatrogenic overheating, light anesthesia, inadequate ventilation (MHAUS 2023)
Scope: Confirm perioperative MH crisis scope — pharmacogenetic hypermetabolic syndrome after halogenated volatile or succinylcholine in genetically susceptible patient (MHAUS 2023)

No severity triggers fired against current inputs.

Plan

Regimen axis: **Malignant Hyperthermia Crisis — MHAUS 2023 sequence: STOP triggers, dantrolene 2.5 mg/kg, treat hyperkalemia + acidosis + dysrhythmia + myoglobinuria** — step "Step 1 — Trigger discontinuation + activate MH protocol (single most important action)".
1. discontinue_volatile_anesthetics_immediately STOP all sevoflurane/isoflurane/desflurane/halothane inhaled immediate (trigger_discontinuation, first line) — Removing trigger gas halts ongoing calcium release at the ryanodine receptor (MHAUS 2023)
2. discontinue_succinylcholine_and_avoid_redose DO NOT redose succinylcholine IV immediate (trigger_discontinuation, first line) — Succinylcholine is a depolarizing trigger; switch to non-depolarizing NMB (rocuronium/vecuronium) (MHAUS 2023)
3. switch_to_tiva_propofol_remifentanil Propofol infusion + opioid (remifentanil or fentanyl) IV continuous (trigger_free_anesthetic, first line) — Maintain anesthesia without halogenated agents (MHAUS 2023)
4. hyperventilate_100_percent_o2_clean_circuit 100% FiO2 at >=10 L/min flush; consider activated charcoal filters on anesthesia circuit inhaled continuous (ventilation_supportive, first line) — Wash out residual volatile; supports increased metabolic O2 demand (MHAUS 2023)
5. call_mhaus_hotline_24_7 MHAUS Hotline 1-800-644-9737 (US/Canada) phone once (expert_consultation, first line) — Live expert MH guidance during crisis (MHAUS 2023)

Setting playbook (inpatient) — Intraoperative recognition + immediate trigger discontinuation + dantrolene 2.5 mg/kg + supportive care; call MHAUS hotline (MHAUS 2023)
6. STOP volatile anesthetics + STOP succinylcholine + switch to TIVA discontinue inhaled/IV immediate — MH suspected (MHAUS 2023) (Remove inciting trigger first (MHAUS 2023))
7. dantrolene 2.5 mg/kg IV bolus, repeat q5-10 min until signs resolve IV q5-10 min titrated — MH suspected (MHAUS 2023) (Definitive RYR1 antagonist (MHAUS 2023))
8. sodium bicarbonate 1-2 mEq/kg IV titrated to pH IV PRN pH<7.2 — Severe metabolic acidosis (MHAUS 2023) (Acidosis correction + K+ shift (MHAUS 2023))
9. insulin + dextrose 10 units IV regular + 25 g (50 mL D50) IV q15-30 min PRN — K>5.5 OR hyperkalemic ECG (MHAUS 2023) (Intracellular K+ shift (MHAUS 2023))
10. amiodarone 150 mg IV bolus + 1 mg/min infusion IV continuous post-bolus — VT/VF (MHAUS 2023) (Preferred antiarrhythmic; AVOID CCB with dantrolene (MHAUS 2023))
11. mannitol 0.25 g/kg IV IV PRN UOP<2 mL/kg/h — Myoglobinuria / oliguria (MHAUS 2023) (Force myoglobin diuresis (MHAUS 2023))
12. furosemide 20-40 mg IV IV PRN — Volume-overloaded oliguria refractory to mannitol (MHAUS 2023) (Selective add-on diuretic (MHAUS 2023))

Non-pharmacologic actions:
- STOP all volatile anesthetics; flush circuit with 100% O2 >=10 L/min (MHAUS 2023)
- Switch to TIVA (propofol + opioid) (MHAUS 2023)
- Switch from succinylcholine to non-depolarizing NMB (rocuronium / vecuronium) (MHAUS 2023)
- Call for HELP — additional anesthesia team, MH cart, cooling supplies (MHAUS 2023)
- Call MHAUS Hotline 1-800-644-9737 (US/Canada) (MHAUS 2023)
- Active cooling: cold IVF, gastric/bladder/rectal lavage, surface ice; STOP at 38C (MHAUS 2023)
- Place arterial line + Foley + additional IV access (MHAUS 2023)
- Activated charcoal filters on anesthesia circuit if available (MHAUS 2023)
- Defer surgery / abort case if feasible; complete only urgent steps (MHAUS 2023)

AVOID / contraindication checks:
- Avoid_calcium_channel_blockers_with_dantrolene_hyperkalemia_collapse (MHAUS 2023)
- Do_not_use_lidocaine_or_procainamide_for_MH_dysrhythmia (MHAUS 2023)
- Dantrolene_compatibility_sterile_water_only_not_saline (MHAUS 2023)
- Succinylcholine_contraindicated_in_known_MH_susceptible (MHAUS 2023)
- Halogenated_volatiles_contraindicated_in_known_MH_susceptible (MHAUS 2023)
- Central_line_for_dantrolene_preferred_due_to_tissue_irritation (MHAUS 2023)

Monitoring

Regimen monitoring:
- continuous core temperature (MHAUS 2023)
- continuous etco2 (MHAUS 2023)
- ABG q1 to 2h during crisis (MHAUS 2023)
- BMP with potassium q1h during crisis then q6h (MHAUS 2023)
- CK q6h for 24 to 36h (Larach 2010)
- urine output q1h target >=2 mL per kg per h (MHAUS 2023)
- urine myoglobin color q1h (MHAUS 2023)
- coags for DIC screen q6h (MHAUS 2023)
- icu monitoring >=24h post stability for recrudescence (MHAUS 2023)

Setting (inpatient) monitoring:
- Continuous core temp + EtCO2 + ECG (MHAUS 2023)
- ABG q1-2h during crisis (MHAUS 2023)
- BMP / K+ q1h during crisis (MHAUS 2023)
- CK q6h x 24-36h (Larach 2010)
- Hourly UOP + urine color (MHAUS 2023)
- Coags / fibrinogen for DIC q6h (MHAUS 2023)

Follow-up plan: Referral to MH Diagnostic Center (CHCT / IVCT or RYR1/CACNA1S sequencing); MedicAlert bracelet; family counseling; future anesthetic plan (trigger-free TIVA); MHAUS registry case report (MHAUS 2023, Riazi 2018)
- Close-out criterion: referral + family counseling documented

Monitoring phase: Continuous core temp, EtCO2, ABG q1-2h, BMP + CK q6h, urine output >=2 mL/kg/h, urine color (myoglobin), coags (DIC screen) (MHAUS 2023)

Disposition

Current setting: inpatient — Intraoperative recognition + immediate trigger discontinuation + dantrolene 2.5 mg/kg + supportive care; call MHAUS hotline (MHAUS 2023)

Disposition criteria:
- ICU admission >=24h post crisis with dantrolene maintenance (MHAUS 2023)
- Step-down only after >=24h without recrudescence + CK trending down + UOP adequate (MHAUS 2023)

Escalation triggers (move to higher acuity):
- Refractory dysrhythmia / cardiac arrest -> ACLS with amiodarone (avoid CCB and lidocaine) + continue dantrolene (MHAUS 2023)
- Refractory hyperkalemia despite insulin/dextrose/bicarb -> emergent hemodialysis (MHAUS 2023)
- Compartment syndrome from massive rhabdomyolysis -> fasciotomy (MHAUS 2023)
- Persistent oliguria + rising creatinine -> nephrology + CRRT (MHAUS 2023)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Larach Clinical Grading Scale rank "almost certain" or "very likely" — hypercarbia + acidosis + rigidity + temperature >39C + rhabdomyolysis (Larach 2010)
- [LIFE_THREATENING] K+ >=6.5 with hyperkalemic ECG changes (peaked T, widened QRS, sine wave) during MH crisis (MHAUS 2023)
- [SEVERE] Masseter muscle rigidity after succinylcholine — early MH warning, especially in pediatric (MHAUS 2023)

Citations

- MHAUS (Malignant Hyperthermia Association of the United States) Recommendations for Diagnosis and Treatment of Malignant Hyperthermia 2023 + Larach Clinical Grading Scale (Anesth Analg 2010) + Riazi RYR1 post-genomics review (Anesthesiology 2018) [PMID:20081135](https://pubmed.ncbi.nlm.nih.gov/20081135/)
- Cited evidence (PMID 28902675) [PMID:28902675](https://pubmed.ncbi.nlm.nih.gov/28902675/)
- Cited evidence (PMID 9523799) [PMID:9523799](https://pubmed.ncbi.nlm.nih.gov/9523799/)
- Cited evidence (PMID 9579517) [PMID:9579517](https://pubmed.ncbi.nlm.nih.gov/9579517/)

Last reconciled with current guidelines: 2026-05-26.
References
  • MHAUS (Malignant Hyperthermia Association of the United States) Recommendations for Diagnosis and Treatment of Malignant Hyperthermia 2023 + Larach Clinical Grading Scale (Anesth Analg 2010) + Riazi RYR1 post-genomics review (Anesthesiology 2018) — PMID:20081135
  • Cited evidence (PMID 28902675) — PMID:28902675
  • Cited evidence (PMID 9523799) — PMID:9523799
  • Cited evidence (PMID 9579517) — PMID:9579517