Vasovagal Pre-Syncope Induced by Epidural Electrical Stimulation Test: A Rare Case Report in a 61-Year-Old Woman Undergoing Ventral Hernia Repair

Objective: Challenging differential diagnosisBackground: Thoracic epidural analgesia is a commonly applied technique for perioperative pain management in major thoraco-abdominal surgery, but is complicated by high failure rates. The epidural electrical stimulation test (EEST) or "Tsui test" is a safe and effective method whereby low electrical current is used to confirm correct epidural catheter position and decrease the variability in analgesic effectiveness of the neuraxial technique.Case Report: We present the case of a 61-year-old woman with no prior cardiac or pulmonary comorbidities who was scheduled to undergo a ventral and parastomal hernia repair with component separation. The patient was offered a low thoracic epidural for perioperative analgesia. Technical aspects of the siting of the epidural catheter were uneventful and a confirmatory Tsui test was planned. At the initiation of electrical stimulation via the epidural catheter to confirm optimal catheter positioning, the patient experienced symptomatic bradycardia and hemodynamic instability that persisted despite terminating the electrical stimulation, and required pharmacologic intervention.Conclusions: This report describes a rare case of vasovagal pre-syncope associated with the EEST or Tsui test. Although vasovagal reactions can be commonly associated with neuraxial procedures due to augmented venous return or severe emotional stress, we raise the possibility that through direct electrical stimulation in the epidural space, the EEST may have the potential to trigger such a physiologic response.