What Causes Numbness In Finger Tips While On Treatment For Back Injury?

i am 25 years old and rather healthy went to hospital other day for passsing out after i had went to hospitaql the night befofre for a back injury....while i wwas ther e they did an ekg and found out i had a heart attack in the past????? NOw for two days i have had random numbness in my finger tips and am very lethargic as i am sure the is from the meds i am on for my back injury but i want to know what the numbness could be when it happens it last anywhere from 20 mins to an hour...what could this be? sincerly woried wife/mom