Malignant Hyperthermia Crisis Management

Immediate Recognition and Trigger Discontinuation

• Early recognition of malignant hyperthermia is essential for patient survival. 1
• Any patient may develop malignant hyperthermia during or shortly after exposure to trigger agents, even after previously uneventful anesthetics. 1
• Immediately discontinue all volatile inhalational anesthetics (e.g., sevoflurane, desflurane, isoflurane, halothane) and succinylcholine at the first suspicion of malignant hyperthermia. 1
• High‑index clinical signs include an unexplained progressive rise in end‑tidal CO₂ > 55 mmHg, masseter spasm after succinylcholine, and generalized muscle rigidity. [2][1]

Initial Emergency Response

• Stop trigger agents, declare an emergency, and hyperventilate with 100 % oxygen at 2–3 × the normal minute ventilation. 1
• Switch immediately to total intravenous anesthesia (TIVA) with propofol, which is completely safe for malignant‑hyperthermia‑susceptible patients. 2

Dantrolene Administration

• Dantrolene is the cornerstone of treatment. [3][4]
• Initial dose: 2–3 mg/kg IV (mix each 20 mg ampoule with 60 mL sterile water). [1][2]
• Repeat dosing: 1 mg/kg IV every 5 minutes until end‑tidal CO₂ < 6 kPa and core temperature < 38.5 °C are achieved. 2
• The total dose may exceed 10 mg/kg, and up to 36–50 ampoules may be required for an adult patient. 1

Comprehensive Monitoring and Support

• Continue routine anesthetic monitoring (SpO₂, ECG, non‑invasive blood pressure, end‑tidal CO₂) and continuous core‑temperature measurement. 1
• Establish wide‑bore IV access; consider arterial line, central venous line, and urinary catheter as needed. 1
• Obtain laboratory samples for potassium, creatine kinase, arterial blood gases, myoglobin, glucose, renal/hepatic function, and coagulation status; monitor for compartment syndrome. 1

Active Cooling Measures

• Administer 2000–3000 mL chilled (4 °C) 0.9 % saline intravenously and apply surface cooling (wet cold sheets, fans, ice packs in axillae and groin). 1
• Discontinue cooling once core temperature falls below 38.5 °C. [1][2]

Management of Specific Complications

• Hyperkalaemia: 50 % dextrose 50 mL with 50 IU insulin plus calcium chloride 0.1 mmol/kg; dialysis may be required in severe cases. 1
• Acidosis: Hyperventilate to normocapnia; give sodium bicarbonate IV if pH < 7.2. 1
• Arrhythmias: Amiodarone 300 mg (≈3 mg/kg) IV; beta‑blockers (e.g., propranolol, metoprolol, esmolol) if tachycardia persists. 1
• Renal protection: Maintain urine output > 2 mL/kg/h; use furosemide 0.5–1 mg/kg, mannitol 1 g/kg, and crystalloid fluids (lactated Ringer’s or 0.9 % saline). [1][5]

Post‑Crisis Observation and Follow‑Up

• Monitor the patient for a minimum of 24 hours in an ICU, HDU, or recovery unit to detect recrudescence. 1
• The attending anesthetist must refer the patient to the national malignant‑hyperthermia assessment unit and inform the patient and primary care physician about the suspected diagnosis and familial implications. 2
• Recommend diagnostic testing (in‑vitro contracture testing) for the patient and first‑degree relatives at designated malignant‑hyperthermia laboratories. 6

Prevention in Known Susceptible Patients

• Completely avoid volatile anesthetics and succinylcholine; prefer regional anesthesia when feasible, or TIVA with propofol if general anesthesia is required. 7
• Prepare the anesthesia machine by purging with 100 % oxygen and consider using activated charcoal filters in the breathing circuit to adsorb trace volatile agents. 2
• Do not administer prophylactic dantrolene before exposure to trigger agents. 7

Practical Safety Measures

• Keep at least 36–50 dantrolene ampoules readily available in the operating suite. 1
• Recognize that malignant hyperthermia is an autosomal‑dominant disorder with a prevalence up to 1 : 3000, underscoring the importance of family counseling. 3

Management of Malignant Hyperthermia Triggers and Safe Anesthetic Practices

Triggering Agents

• The European Malignant Hyperthermia Group identifies only volatile inhalational anesthetics and succinylcholine as agents that can precipitate malignant hyperthermia (MH); all other anesthetic drugs are non‑triggering. 8
• Exposure to any of these triggers can cause an MH crisis during or shortly after anesthesia, even in patients who have previously tolerated uneventful general anesthesia. 9

Non‑Triggering Agents and Preferred Alternatives

• Propofol is safe for patients with known MH susceptibility and is the intravenous agent of choice for total intravenous anesthesia (TIVA). 10
• European guidelines recommend immediate conversion to a non‑triggering technique (TIVA with propofol) when an MH crisis is suspected. 8
• The following drugs are considered safe (non‑triggering) for MH‑susceptible patients:
  
  • Propofol (first‑line for TIVA)
  • Nitrous oxide
  • All intravenous induction agents (except the known triggers)
  • Benzodiazepines (including newer agents such as remimazolam)
  • Opioids
  • Non‑depolarizing muscle relaxants (e.g., rocuronium, vecuronium)
  • Evidence from Anaesthesia (2021) and the British Journal of Anaesthesia (2021). [10][11]8

Guideline Recommendations for Anesthetic Management

• Avoid completely volatile anesthetics and succinylcholine in MH‑susceptible individuals. 10
• Preferred technique when feasible: regional anesthesia. 10
• If general anesthesia is required:
  
  • Use TIVA with propofol as the primary agent. 10
  • Purge the anesthesia machine with 100 % oxygen until residual volatile agent concentration is < 5 ppm. 10
  • Consider activated charcoal filters in the breathing circuit to adsorb trace volatile agents. 11
  • Do not give prophylactic dantrolene before any trigger exposure. 11

Monitoring and Post‑operative Observation

• Standard intra‑operative monitoring plus post‑operative surveillance for at least 24 hours when an MH crisis is suspected or when trigger exposure cannot be ruled out. 8

Clinical Characteristics of Malignant Hyperthermia

• MH is a hypermetabolic crisis characterized by hyperthermia, tachycardia, hypercapnia, metabolic acidosis, muscle rigidity, and rhabdomyolysis. 8
• Recurrence of an MH episode can occur up to 24 hours after the initial event, necessitating prolonged observation. 8

Immediate Management of Malignant Hyperthermia

Critical First Steps (Within Seconds)

• Discontinue all triggering agents immediately—including volatile inhalational anesthetics (e.g., sevoflurane, desflurane, isoflurane, halothane) and succinylcholine—to stop the hypermetabolic cascade. 12
• Hyperventilate aggressively with 100 % oxygen at 2–3 × the normal minute ventilation to rapidly eliminate excess CO₂. 13
• Declare a malignant hyperthermia emergency and summon additional personnel, as the crisis requires coordinated resuscitation. 14
• Switch to total‑intravenous anesthesia (TIVA) with propofol, which is considered safe for MH‑susceptible patients. 12
• Inform the operating surgeon and request immediate termination or postponement of the procedure. 13
• Disconnect the vaporizer promptly; do not waste time changing the entire breathing circuit or anesthesia machine. 14

Dantrolene Administration (Cornerstone of Therapy)

• Dantrolene is the only specific drug that reverses the malignant hyperthermia hypermetabolic state and must be given without delay. 15
• Initial dose: 2–3 mg kg⁻¹ intravenously (each 20 mg ampoule reconstituted with 60 mL sterile water). 16
• Repeat dosing: 1 mg kg⁻¹ IV every 5 minutes until treatment goals are met. 16
• Treatment goals: end‑tidal CO₂ < 6 kPa (≈ 45 mmHg) with normal minute ventilation and core temperature < 38.5 °C. 15
• The recommended maximum dose of 10 mg kg⁻¹ may be exceeded in fulminant cases. 15
• Adult patients may require 36–50 ampoules (≈ 720–1000 mg) of dantrolene to achieve therapeutic effect. 14
• Dantrolene reconstitution is labor‑intensive; assign a dedicated team member to prepare the drug while others continue resuscitation. 12

Active Cooling Measures

• Administer 2 000–3 000 mL of chilled (4 °C) 0.9 % saline intravenously to lower core temperature. 13
• Apply surface cooling (wet cold sheets, fans, ice packs placed in the axillae and groin). 14
• Discontinue active cooling once core temperature falls below 38.5 °C to avoid iatrogenic hypothermia. 13

Monitoring and Vascular Access

• Obtain wide‑bore intravenous access immediately with large‑gauge cannulas. 12
• Consider placement of an arterial line, central venous catheter, and urinary catheter for intensive hemodynamic and renal monitoring. 14
• Continue routine anesthetic monitoring: pulse oximetry, ECG, non‑invasive blood pressure, and end‑tidal CO₂. 14
• Continuously measure core temperature using an esophageal, rectal, or bladder probe. 12

Laboratory Monitoring

• Draw immediate blood samples for potassium, creatine kinase, arterial blood gases, myoglobin, and glucose. 12
• Assess renal and hepatic function and coagulation status. 14
• Vigilantly monitor for signs of compartment syndrome. 12

Management of Life‑Threatening Complications

Hyperkalaemia

• Administer 50 mL of 50 % dextrose together with 50 IU insulin (adult dose). 14
• Give calcium chloride 0.1 mmol kg⁻¹ IV (e.g., 7 mmol ≈ 10 mL for a 70‑kg adult). 14
• Initiate dialysis if hyperkalaemia is refractory to medical therapy. 13

Metabolic Acidosis

• Primary intervention: hyperventilate to achieve normocapnia. 14
• Give intravenous sodium bicarbonate if arterial pH falls below 7.2. 13

Cardiac Arrhythmias

• Administer amiodarone 300 mg IV (≈ 3 mg kg⁻¹ for an adult). 14
• Use β‑blockers (propranolol, metoprolol, or esmolol) if tachycardia persists despite other measures. 13

Renal Protection (Prevent Myoglobin‑Induced AKI)

• Maintain urine output > 2 mL kg⁻¹ h⁻¹. 14
• Give furosemide 0.5–1 mg kg⁻¹ IV as needed. 13
• Administer mannitol 1 g kg⁻¹ IV for osmotic diuresis. 14
• Provide aggressive crystalloid hydration (lactated Ringer’s solution or 0.9 % saline). 13

Post‑Crisis Management

• Monitor the patient for at least 24 hours in an ICU, HDU, or recovery area because recrudescence can occur. 12
• Do not start a continuous dantrolene infusion after the loading dose; therapeutic levels persist for ~6 hours and infusion raises the risk of thrombophlebitis and muscle weakness. 15
• If recrudescence is observed, give additional dantrolene 2–2.5 mg kg⁻¹ every 10 minutes until clinical signs regress. 15

Mandatory Follow‑Up Actions

• The attending anesthetist must refer the patient directly to the national malignant hyperthermia assessment unit (e.g., Leeds Malignant Hyperthermia Unit in the UK). 16
• Inform the patient and their general practitioner about the suspected diagnosis and its familial implications before discharge. 16
• Recommend definitive diagnostic testing (in‑vitro contracture testing) for the patient and first‑degree relatives at accredited MH laboratories. 13

Recognition Triggers (Early Warning Signs)

• An unexplained, progressive rise in end‑tidal CO₂ is the earliest and most sensitive indicator of malignant hyperthermia. 16
• Masseter muscle spasm following succinylcholine administration is a classic early sign. 17
• Generalized skeletal muscle rigidity may develop rapidly. 17
• Unexplained tachycardia and hyperthermia (temperature rise often occurs later). 12
• A rapid increase in CO₂ production despite adequate ventilation should prompt immediate suspicion. 16
• Malignant hyperthermia can occur even in patients with prior uneventful exposures to triggering agents; previous tolerance does not guarantee safety. 17

Malignant Hyperthermia Crisis Management Guidelines

Immediate Recognition and Initial Actions

• Discontinue all volatile anesthetics and succinylcholine at the first suspicion of malignant hyperthermia and hyperventilate the patient with 100 % oxygen at 2–3 × the normal minute ventilation to rapidly eliminate excess CO₂【18】【19】.
• Declare a code, summon additional personnel, switch to total‑intravenous anesthesia with propofol, and inform the surgical team to halt or postpone the procedure【18】【19】.

Dantrolene Therapy

• Administer an initial dose of dantrolene 2–3 mg/kg IV (each 20 mg ampoule reconstituted with 60 mL sterile water) without delay【20】.
• Repeat 1 mg/kg IV every 5 minutes until treatment goals are met【20】.
• Treatment endpoints are end‑tidal CO₂ < 6 kPa (≈ 45 mmHg) with normal minute ventilation and core temperature < 38.5 °C【20】.
• The maximum recommended cumulative dose is 10 mg/kg, but higher doses may be required in fulminant cases【18】【21】.
• Adult patients can require 36–50 dantrolene ampoules (≈ 720–1000 mg) to achieve therapeutic effect【18】【21】.

Aggressive Cooling Measures

• Infuse 2000–3000 mL of chilled (4 °C) 0.9 % saline intravenously to accelerate core‑temperature reduction【18】【21】.
• Apply surface‑cooling techniques such as wet cold sheets, fans, and ice packs placed in the axillae and groin【18】【21】.
• Continue cooling until core temperature falls below 38.5 °C, then stop to avoid iatrogenic hypothermia【18】【21】.

Comprehensive Monitoring

• Establish wide‑bore intravenous access immediately; consider arterial line, central venous catheter, and urinary catheter for intensive monitoring【21】【19】.
• Maintain routine anesthetic monitoring (pulse oximetry, ECG, non‑invasive blood pressure, end‑tidal CO₂) and continuous core‑temperature measurement via esophageal, rectal, or bladder probe【21】【19】.
• Obtain immediate laboratory samples for potassium, creatine kinase, arterial blood gases, myoglobin, and glucose; assess renal and hepatic function, coagulation status, and watch for compartment syndrome【21】【19】.

Management of Life‑Threatening Complications

Hyperkalaemia

• Give 50 mL of 50 % dextrose with 50 IU insulin intravenously, followed by calcium chloride 0.1 mmol/kg IV; initiate dialysis if refractory【18】【21】.

Metabolic Acidosis

• Prioritize hyperventilation to achieve normocapnia; administer intravenous sodium bicarbonate if arterial pH falls below 7.2【18】【21】.

Cardiac Arrhythmias

• Administer amiodarone 300 mg IV (≈ 3 mg/kg for an adult); use β‑blockers (propranolol, metoprolol, or esmolol) if tachycardia persists【18】【21】.

Renal Protection (Prevent Myoglobin‑Induced AKI)

• Maintain urine output > 2 mL/kg/h; give furosemide 0.5–1 mg/kg IV as needed and mannitol 1 g/kg IV for osmotic diuresis; provide aggressive crystalloid hydration with lactated Ringer’s solution or 0.9 % saline【18】【21】.

Post‑Crisis Management

• Monitor the patient for a minimum of 24 hours in an ICU, HDU, or recovery area because recrudescence can occur【21】【19】【20】.
• If recrudescence is observed, give additional dantrolene 2–2.5 mg/kg every 10 minutes until clinical signs regress.
• Refer the patient directly to the national malignant hyperthermia assessment unit (e.g., Leeds Malignant Hyperthermia Unit in the UK)【20】.
• Inform the patient and their general practitioner about the suspected diagnosis and its familial implications before discharge【20】.
• Recommend definitive diagnostic testing (in‑vitro contracture testing) for the patient and first‑degree relatives at accredited MH laboratories【18】【22】【20】.

Prevention in Known MH‑Susceptible Patients

• Completely avoid volatile anesthetics and succinylcholine; preferentially use regional anesthesia or, if general anesthesia is required, total‑intravenous anesthesia with propofol【20】.
• Purge the anesthesia machine with 100 % oxygen until residual volatile‑agent concentration is < 5 ppm and consider activated charcoal filters in the breathing circuit to adsorb trace volatiles【20】.

Additional Clinical Insight

• Malignant hyperthermia can occur even in patients with prior uneventful exposures to triggering agents; previous tolerance does not guarantee safety【22】.