What is the use of dantrolene after succinylcholine (succinylcholine) in patients with a family history of malignant hyperthermia or certain muscular dystrophies?

Dantrolene After Succinylcholine: Treatment of Malignant Hyperthermia

Dantrolene is used after succinylcholine to treat malignant hyperthermia (MH), a life-threatening hypermetabolic crisis that succinylcholine can trigger in susceptible individuals, requiring immediate administration at 2-2.5 mg/kg IV every 10 minutes until symptoms resolve. 1

Primary Indication: Malignant Hyperthermia Crisis

Dantrolene is the only specific treatment for malignant hyperthermia, which presents as a potentially fatal hypermetabolic state of skeletal muscle triggered by succinylcholine (with or without volatile anesthetics). 2, 3, 4

Clinical Recognition of MH

The syndrome presents with specific warning signs that demand immediate dantrolene administration:

• Masseter spasm or jaw rigidity progressing to generalized muscle rigidity 3
• Profound hyperpyrexia with rapidly rising core temperature 3
• Tachycardia and tachypnea that fail to respond to deepening anesthesia 3
• Elevated end-tidal CO2 despite normal minute ventilation 1
• Metabolic acidosis with elevated serum potassium 3
• Skin mottling and later coagulopathies 3

Critical Dosing Protocol

The initial dose is 2-2.5 mg/kg based on actual body weight (not ideal body weight), up to a maximum of 300 mg per dose. 1 This dosing is critical because dantrolene is hydrophobic and under-dosing increases morbidity and mortality. 1

Repeat doses of 2-2.5 mg/kg every 10 minutes until signs of MH regress. 1 Treatment delay dramatically increases complications—every 10-minute delay worsens outcomes, reaching 100% complication rate with 50-minute delays. 5

Post-Crisis Management

After initial resolution, continuous infusion or routine intermittent boluses of dantrolene are NOT recommended. 1 The rationale is compelling:

• Therapeutic plasma concentrations persist for approximately 6 hours after loading dose 1
• Continuous infusion causes high incidence of thrombophlebitis 1, 6
• Dose-dependent muscle weakness may compromise weaning from mechanical ventilation 1

If recrudescence occurs, give additional 2-2.5 mg/kg doses every 10 minutes until MH signs regress again. 1

Monitor for recurrent signs of MH for at least 24 hours after initial resolution. 1

Why Succinylcholine Triggers MH

Succinylcholine can trigger fulminant MH reactions even without volatile anesthetics. 1 The mechanism involves:

• Intrinsic skeletal muscle abnormality in susceptible individuals 2
• Elevated myoplasmic calcium activated by the triggering agent 2
• Acute cellular catabolic cascade leading to the hypermetabolic crisis 2

Dantrolene works by inhibiting calcium release from the sarcoplasmic reticulum, reestablishing normal myoplasmic calcium equilibrium and reversing the physiologic, metabolic, and biochemical changes of MH. 2

Dantrolene Availability Requirements

Dantrolene must be immediately available (within 5 minutes) wherever succinylcholine is used routinely. 1, 7 This is based on evidence that:

• Succinylcholine alone (without volatile anesthetics) can trigger fulminant MH requiring dantrolene treatment 1, 5
• 24 documented MH cases were triggered by succinylcholine without volatile agents, with 13 requiring dantrolene 5
• Overall MH mortality is 1-10%, with 15 U.S. deaths including 4 in freestanding facilities 5

Typical stock levels: 36 vials immediately available, or 48-60 vials if additional supplies cannot be obtained within 30-60 minutes. 1

Exception to Availability

Pre-hospital emergency settings may be exempt from stocking dantrolene despite succinylcholine use, because it is impractical to carry, MH recognition is less likely, and insufficient resources exist for administration. 1 However, this should not prevent stocking succinylcholine for emergency airway rescue. 1

Common Pitfalls and Complications

Dantrolene-Related Complications

The most frequent complications from dantrolene administration include:

• Muscle weakness (14.6-21.7%) which may delay extubation 6
• Phlebitis (9-9.2%) from IV administration 6
• Gastrointestinal upset (4.1-4.3%) 6

Risk of complications increases 25-29% when total dantrolene dose doubles, but these complications are rarely life-threatening and the benefit of treating MH far outweighs these risks. 6

Critical Monitoring Parameters

• Continuous temperature and expired CO2 monitoring aids early MH recognition 3
• Serum creatine kinase and potassium to prevent myoglobinuric renal failure and dysrhythmias 7
• Adequate urinary output and measures to control rising temperature 3

Outcome Data

When dantrolene is administered promptly with supportive measures, recovery occurs in virtually 100% of MH patients. 8 There is rapid resolution of hyperthermia, dysrhythmias, muscle rigidity, tachycardia, hypercapnia, and metabolic acidosis. 8

Without dantrolene availability, MH morbidity ranges from 20-37%, emphasizing the critical importance of immediate access to this life-saving medication. 5, 9