Local Anesthetic Systemic Toxicity in Pregnancy: A Retrospective Cohort Analysis.

Introduction Local anesthetic systemic toxicity (LAST) is a rare complication of regional anesthesia. Pregnancy is a risk factor due to gestational physiologic changes. Labor and disorders of pregnancy can mask or delay symptoms of LAST, slowing appropriate intervention. This study examines LAST within a larger cohort and identifies features that help distinguish LAST in pregnant women from LAST in nonpregnant patients. Methods The TriNetX database was used to compare pregnant and nonpregnant patients with LAST from 2013 to 2023. Cohorts were matched on age, race, obesity status, diabetes, metabolic disorders, local anesthetic type, and cardiovascular, liver, kidney, and respiratory disease. Outcomes included prodromal symptoms of LAST and symptoms of cardiac and central nervous system excitation and depression. Results Matching occurred for 276 pregnant and 276 nonpregnant patients. Pregnant cohorts had a significantly higher risk of cardiac depression (risk ratio (RR)=1.96 (95% confidence interval (CI): 1.44-2.66), p<0.01) and significantly lower risk of cardiac excitation (RR=0.38 (95% CI: 0.22-0.63), p<0.01), prodromal symptoms (RR=0.17 (95% CI: 0.09-0.33), p<0.01), central nervous system excitation (RR=0.44 (95% CI: 0.21-0.90), p=0.02), and central nervous system depression (RR=0.24 (95% CI: 0.13-0.48), p<0.01) than nonpregnant cohorts. Conclusion Pregnant patients with LAST were more likely to exhibit cardiac depression and less likely to manifest prodromal symptoms, cardiac excitation, and central nervous system excitation and depression than nonpregnant patients. Physiological changes during pregnancy and prompt detection and treatment may explain these differences. These findings highlight the variable nature of LAST and how pregnancy may influence its clinical presentation.