Relationship Between Strabismus and Malignant Hyperthermia
There is no established association between strabismus and malignant hyperthermia susceptibility. 1
Historical Context and Current Understanding
The concern about a potential link between strabismus and malignant hyperthermia (MH) arose decades ago but has been definitively refuted by modern evidence:
- Malignant hyperthermia is no longer considered an issue specifically associated with strabismus. 1
- The historical association was likely based on coincidental case reports rather than true causation, as strabismus surgery is one of the most common pediatric ophthalmic procedures and MH is a rare pharmacogenetic disorder occurring in approximately 1:100,000 to 1:250,000 general anesthetics. 2
True Risk Factors for Malignant Hyperthermia
When evaluating patients for MH susceptibility, focus on these actual risk factors rather than the presence of strabismus:
- Genetic susceptibility is the primary determinant, with MH inherited in an autosomal dominant pattern with variable penetrance and a genetic prevalence of approximately 1:2000 in the general population. 3
- Confirmed genetic variants in RYR1, CACNA1S, or STAC3 genes are significant risk factors, with over 400 variants identified in RYR1 and at least 34 being causal for MH. 3, 4, 5
- Associated neuromuscular disorders such as Duchenne muscular dystrophy, clinical myopathy with genetic etiology involving MH-related genes, history of unexplained rhabdomyolysis, idiopathic hyperCKemia, and unexplained exertional heat illness are true risk factors. 3, 6
- Personal or family history of unexplained anesthetic complications, masseter muscle spasm, or confirmed MH reactions should raise suspicion. 2
Clinical Implications for Strabismus Surgery
While strabismus itself does not increase MH risk, anesthetic management for strabismus surgery requires attention to other considerations:
- Preoperative assessment should focus on identifying associated neuromuscular disorders, congenital syndromes, or cardiac disease that may accompany strabismus, as these conditions—not the strabismus itself—could be associated with MH susceptibility. 1
- Standard MH precautions apply based on the patient's actual risk factors, not the presence of strabismus. 1
- Patients undergoing strabismus surgery are at high risk for postoperative nausea and vomiting and oculocardiac reflex, but these are unrelated to MH susceptibility. 1
Common Pitfall to Avoid
- Do not assume that a patient with strabismus has increased MH risk based solely on the eye condition—this outdated association has been disproven and continuing to act on it may lead to unnecessary anxiety and inappropriate anesthetic planning. 1
- Do assess for the actual risk factors listed above, as a history of uneventful previous anesthesia does not exclude MH susceptibility, and patients can have multiple uneventful exposures before developing a reaction. 2, 3