[Sudden syncope during spinal block under sitting position: a report of three cases]

We reported 3 cases of sudden syncope during saddle block under sitting position. Patients were healthy and had no history of fainting. Syncope occurred following hypotension and bradycardia during difficult lumbar dural punctures under sitting position. Patients were treated successfully by changing position to supine, elevating both legs and giving vasopressors. Neurocardiac syncope due to the activation of afferent cardiac C-fiber has been suggested as a possible explanation in sudden syncope, which follows head-up position or emotional change. The first sign of syncope was hypotension and bradycardia due to cardiac C-fiber reflex. How to prevent this NCS under saddle block are as follows; 1. vigorous search for history of syncope, 2. pay attention to the patients during spinal tap, 3. skillful technique in spinal tap, and 4. proper premedication including anticholinergic agents. Treatments include 1. changing position to supine, 2. elevation of both legs to increase ventricular end-diastolic pressure, and 3. use of vasopressors including phenylephrine.