Dynamic Characteristics of Myocardial Depression After Severe Bupivacaine-Induced Local Anesthetic Systemic Toxicity: A Case Report

Technical Summary: Dynamic Characteristics of Myocardial Depression After Severe Bupivacaine-Induced LAST

Problem Statement
Bupivacaine-induced local anesthetic systemic toxicity (LAST) is a critical clinical emergency that can precipitate severe myocardial depression, circulatory collapse, and cardiac arrest. While 20% lipid emulsion therapy and advanced life support are established interventions, some patients develop refractory cardiogenic shock requiring venoarterial extracorporeal membrane oxygenation (VA-ECMO). A significant gap exists in the literature regarding the dynamic evolution of cardiac function in these cases. Most existing reports focus on resuscitative measures and final outcomes, lacking serial, visually interpretable data on the timing of the functional nadir (lowest point of function) and the specific trajectory of recovery during ECMO support. Consequently, the optimal timing for ECMO weaning in bupivacaine-induced cardiotoxicity remains difficult to determine based on current evidence.

Methodology
This study presents a detailed case report of a 32-year-old pregnant woman (38 weeks gestation) who developed severe LAST following the inadvertent intrathecal administration of 2.0 mL of 0.5% bupivacaine during combined spinal-epidural anesthesia. The patient rapidly progressed from neurological symptoms (tremors, convulsions) to refractory circulatory failure.

The clinical management and data collection involved:

• Intervention: Administration of 20% lipid emulsion, vasoactive agents, and the urgent initiation of VA-ECMO due to hemodynamic instability.
• Diagnostics: Serial bedside echocardiography was performed daily to monitor left ventricular (LV) function. Coronary angiography was used to rule out obstructive coronary artery disease.
• Monitoring: Continuous tracking of hemodynamic parameters, including stroke volume (SV), cardiac output (CO), and left ventricular ejection fraction (LVEF), alongside plasma bupivacaine concentration and cardiac biomarkers (troponin, myoglobin, CK-MB).
• Weaning Protocol: A pump-controlled retrograde flow trial was utilized to assess readiness for ECMO decannulation.

Key Results
The patient exhibited a distinct, delayed pattern of myocardial depression and recovery:

• Initial Presentation: Upon ICU admission, the patient presented with refractory shock requiring high-dose vasopressors. Echocardiography revealed diffuse LV wall motion abnormalities (sparing the apex) with an initial LVEF of approximately 27%.
• Functional Nadir: Contrary to immediate recovery expectations, cardiac function continued to deteriorate. The nadir was reached 24 hours after symptom onset, with SV dropping to 10.4 mL, CO to 0.79 L/min, and LVEF to 13.2%.
• Plateau Phase: Following the nadir, cardiac function remained at a low-level plateau for several days (Days 2–5), with SV stabilizing between 25–28 mL and LVEF between 23%–33%.
• Recovery Phase: Significant recovery began on Day 6 (approx. 120 hours) post-onset. SV increased to 40.1 mL, CO to 3.49 L/min, and LVEF to 49%.
• Outcome: The patient met weaning criteria on Day 6, was successfully decannulated, extubated, and transferred to the obstetrics department. Post-decannulation monitoring showed continued improvement (LVEF 49.4% on Day 10).

Significance and Claims
The authors claim that this case provides a unique reference for the management of severe bupivacaine-induced cardiotoxicity by characterizing its specific temporal dynamics:

1. Delayed Nadir: The study suggests that severe bupivacaine-induced myocardial depression is not characterized by immediate stabilization but rather by a delayed functional nadir occurring approximately 24 hours after onset, followed by a transient plateau.
2. Reversibility: The case demonstrates that even profound myocardial depression (LVEF <15%) can be fully reversible if supported by VA-ECMO, bridging the patient to recovery.
3. Role of Serial Echocardiography: The authors emphasize that serial bedside echocardiography is critical for visualizing this dynamic trajectory. It serves as a tool to distinguish between the "delayed nadir/plateau" pattern of bupivacaine toxicity and the earlier recovery patterns seen in other conditions (e.g., post-cardiac arrest or Takotsubo syndrome).
4. Weaning Guidance: The specific recovery timeline observed (significant improvement by Day 6) provides a clinical reference for determining the optimal timing for ECMO weaning in similar refractory cases, moving beyond static assessments to dynamic trend analysis.

The paper concludes modestly, noting that while these findings offer a valuable reference, they are derived from a single patient, and the fixed time window for recovery cannot be universally generalized without further study.