Fludrocortisone and Midodrine are both medications that can help raise blood pressure. Ask your physician if one of these medications would be right for your situation. People are not generally prescribed medicine for low blood pressure, as it's not often a cause for concern unless it presents with symptoms.
Why do the middle fingers lock up when experiencing pain in neck and shoulders?   One cause could be some kind of impingement (pressure or swelling that applies pressure) of the spinal cord at C7, one of the cervical segments of your spine.
Trigger finger is a snapping or locking condition of any of the digits of the hand when opened or closed. Trigger finger is medically termed stenosing tenosynovitis. Trigger finger is caused by local swelling from inflammation or scarring of the tendon sheath around the flexor tendons. These are tendons that normally pull the affected digit inward toward the palm (flexion). Usually, trigger finger occurs as an isolated condition because of repetitive trauma.