Scenario: The nurse (working 7 AMto 7 PM) retrieves heparin from the medication room to flush a client's heparin lock but does not check the label for concentration. The nurse flushes the client's heparin lock with 1 mL of the heparin 1,000 units per mL solution. The client received an IV antibiotic at 10:00 AM, 2:00 PM, and 6:00 PM. The nurse flushed the IV with 1 mL of heparin 1,000 units per mL solution each time following the infusion of the antibiotic. By the end of the nurse's shift at 7:00 PM, the client was complaining of blood in the urine and an increase in her menstrual flow (soaked through pajamas and sheets on the bed). A review of the nurse's actions revealed the client had received 4,000 units during the shift. (a) What error occurred here? (b) What could the nurse have done to prevent the error?