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 pregnancy from 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 (RR, 1.96 [95% 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.

Key Messages Local anesthetic systemic toxicity, a rare complication of regional anesthesia, has variable manifestations within the cardiovascular and central nervous systems. This study identifies local anesthetic systemic toxicity in a larger cohort relative to previous literature, revealing a distinct presentation in pregnant patients compared to their nonpregnant counterparts. These findings emphasize the diverse nature of local anesthetic systemic toxicity and indicate severe complications in pregnancy. Recognition of subtle clinical manifestations in pregnant patients receiving local anesthesia aids accurate diagnosis and timely intervention in the event of toxicity. The present study provides additional insight into local anesthetic systemic toxicity and sets the stage for further investigations in pregnant patients.

The authors have declared no competing interest.

This study did not receive any funding.

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