Muscle Relaxants in Rhabdomyolysis: Absolute Contraindication
Do not give muscle relaxants, particularly succinylcholine, to patients with rhabdomyolysis—this is an absolute contraindication that can cause life-threatening hyperkalemia and worsen muscle injury. 1
Why Muscle Relaxants Are Dangerous in Rhabdomyolysis
Succinylcholine: Absolutely Contraindicated
Succinylcholine is contraindicated in all cases of primary muscle damage, including rhabdomyolysis, because it induces generalized muscle contraction that worsens rhabdomyolysis and causes life-threatening hyperkalemia. 1
The mechanism involves depolarization of already-damaged muscle membranes with massive potassium efflux from injured myocytes—essentially adding insult to injury in muscles that are already releasing their intracellular contents. 1
This contraindication applies to any condition causing muscle membrane damage or receptor upregulation, which is definitionally present in rhabdomyolysis. 1
The American Academy of Pediatrics and other medical societies recommend avoiding succinylcholine in patients with primary muscle damage due to the high risk of hyperkalemia. 2
Non-Depolarizing Muscle Relaxants: Also Problematic
Patients with muscle damage demonstrate very significant increases in sensitivity to all non-depolarizing agents, requiring substantial dose reductions of 50-75%. 1
Rocuronium shows significantly increased sensitivity in patients with primary muscle damage, with prolonged onset and recovery times. 1
The risk-benefit calculation heavily favors avoiding muscle relaxants entirely unless the patient requires emergency surgery or intubation where alternatives are not feasible. 1
If Neuromuscular Blockade Is Absolutely Unavoidable
Agent Selection (Only in Life-Threatening Emergency)
Use benzylisoquinoline muscle relaxants (atracurium or cisatracurium) as they have organ-independent elimination and are safer in the setting of muscle damage. 1
Reduce doses by 50-75% from standard dosing due to dramatically increased sensitivity. 1
Mandatory Monitoring
Neuromuscular blockade monitoring is mandatory when any muscle relaxant is used in patients with muscle disease or damage. 1
Train-of-four (TOF) ratio monitoring by EMG should be performed to guide dosing and prevent overdosing. 1
If TOF ratio is less than 0.9 before neuromuscular blockade, sensitivity to muscle relaxants is greater and doses must be substantially reduced. 1
Reversal Strategy
Sugammadex is the preferred reversal agent for steroidal muscle relaxants in patients with muscle disease, as neostigmine can cause additional complications including effects on muscle action potential and rhythm disturbances. 1
Neostigmine and atropine are difficult to manage in primary muscle damage due to drying of secretions, potential cardiac conduction disorders, and central effects. 1
Additional Context on Rhabdomyolysis and Muscle Relaxants
Drug-Induced Rhabdomyolysis Considerations
Benzodiazepines and other sedatives have been associated with rhabdomyolysis, particularly in overdose situations or with prolonged immobilization. 3, 4
Cyclobenzaprine (a skeletal muscle relaxant) overdose can cause rare but potentially critical manifestations including neuroleptic malignant syndrome, which itself causes severe rhabdomyolysis. 5
Critical Pitfall to Avoid
The most dangerous mistake is assuming that because a patient with rhabdomyolysis needs intubation, standard rapid sequence intubation with succinylcholine is acceptable—it is not. 1 Even in emergency situations, rocuronium at higher doses (≥0.9 mg/kg) should be used instead, accepting the longer duration of action as a necessary trade-off for safety. 2