Pharmacogenomics: General Anesthesia Susceptibility in Genetic Variations
Author
Ty Barnes
Instructor
Dr. Hawthorne
Methodology
PRISMA Guidelines
Databases
NIH · PubMed · Google Scholar
Introduction
Anesthesiologists, certified registered nurse anesthetists (CRNAs), and certified anesthesiologist assistants (CAAs) must remain continuously aware of the diverse anesthetic responses that can arise during procedures. Genetic influences — particularly polymorphisms — are especially significant, accounting for 20–95% of atypical reactions to medicinal anesthesia.
DNA mutations often target enzymes and cellular receptors responsible for normal neuromuscular function and efficient drug metabolism. Some mutations cause severe, direct responses — including Malignant Hyperthermia (RyR1) and Pseudocholinesterase Deficiency (BCHE). Others produce subtler, broader effects on a range of anesthetic medications, including CYP450 and MC1R variants.
"The foremost goal is to promote individual and personalized dosages, drug options, and supervision — ensuring every patient receives care tailored to their genetic profile."
Genetic Mutations & Clinical Implications
Irregular calcium discharge in skeletal muscle when volatile anesthetics are present, causing hyperthermia, cardiac arrhythmias, and muscle rigidity. The RyR1 protein — one of the body's largest ion channels with 100+ exon variants — loses its ability to regulate calcium when the Ala4893 gene variant is present.
Trigger
Volatile anesthetics (halothane, sevoflurane, desflurane)
Management
IV propofol, chilled saline infusion, dantrolene sodium. Early detection via end-tidal CO₂ >51 mmHg and lactate >3.2 mmol/L.
Autosomal recessive mutation on chromosome 3 reduces butyrylcholinesterase production in the liver. This enzyme normally degrades succinylcholine; deficiency causes prolonged neuromuscular blockade. Four inherited variants exist, each producing different durations of paralysis.
Trigger
Succinylcholine (depolarizing neuromuscular blocker)
Management
Neuromuscular stimulation monitoring; avoidance of succinylcholine; biochemical screening via dibucaine or fluoride inhibition testing.
Cytochrome P450 enzymes (CYP2B6, CYP2C9, CYP3A4) and UGT1A9 metabolize propofol and lidocaine in the liver. Polymorphisms can increase or decrease enzyme activity — CT heterozygotes for UGT1A9 require less propofol; CC homozygotes require more. CYP3A4*22 creates lidocaine hypersensitivity.
Trigger
Propofol, lidocaine, and a broad range of analgesics and sedatives
Management
Delayed consciousness or premature awareness as indicators; preoperative genotyping and blood sampling beneficial.
Melanocortin-1 receptor gene variants — commonly associated with red hair — have been correlated with higher volatile anesthetic requirements and altered mu-opioid analgesia in both mice and humans.
Trigger
Volatile anesthetics; opioid analgesics
Management
Dose titration; increased monitoring for awareness; consideration during preoperative anesthetic planning.
Conclusions & Future Directions
Polymorphisms in RyR1, BCHE, CYP450, and UGT1A9 each impact anatomical responses to anesthetics in distinct ways. RyR1 mutations reduce calcium channel retention and create hypersensitivity to inhaled agents. BCHE variants decrease enzymatic activity of anesthetic metabolizers in the liver. CYP450 and UGT1A9 mutations produce both sensitive and resistant responses to general and local anesthesia.
Pharmacogenetic clinical measures — including preoperative genotyping — are currently limited largely to research settings. The Clinical Pharmacogenetics Implementation Consortium (CPIC) is being expanded, though it currently lacks the ability to identify the BCHE succinylcholine susceptibility mutation. The Pharmacogenomics Knowledgebase (PharmGKB) is becoming increasingly utilized among anesthetists for personalized care planning.
Computational modeling may eventually enable individualized anesthetic approaches unique to each patient's genetic variability — a significant step toward eliminating preventable adverse anesthetic events.
References
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