What Causes A Shock After Taking Lumbar Epidural Injections?
Sympathetic blockage and/or vasovagal response
Detailed Answer:
I read your question carefully and I understand your concern.
In my opinion the two most possible explanations for your episodes are an exaggerated vaso-vagal response possibly combined with the sympathetic block.
Vagal activation leads to dilatation of blood vessels and a drop in the heart rate, hence leading to lowering of blood pressure. It is named after the vagus nerve, the main nerve mediating this response which comes from your brainstem and is the main component of the parasympathetic nervous system.
This reaction when exaggerated is one of the main causes for syncope (vasovagal syncope is one of the most common causes of fainting). It is usually triggered by strong pain and emotional distress which is I believe what the episodes you mention have in common, including the gall stone procedure. At times can be triggered even by a simple puncture of the vein.
During the epidurals, one other trigger apart from pain and fear may also be the anesthetics which are used, which lead to blockage of the sympathetic nervous system located along the spine. The sympathetic nervous system has the completely opposite effect to the vagus nerve, so its blockage has the same effect of blood pressure drop due to slowing of heart rate and vessel dilatation.
The best preventive way for these episodes to reoccur during possible future procedures would be having plenty of salt and fluids both orally as intravenously prior and during the procedure.
I remain at your disposal for further questions.