Final answer:
The nurse should complete an incident report if the patient experiences decreased blood pressure after administering ceftazidime due to a severe penicillin allergy.
Step-by-step explanation:
The nurse should identify decreased blood pressure as an indication to complete an incident report. Ceftazidime is a cephalosporin antibiotic and individuals who have a severe penicillin allergy may also have cross-reactivity with cephalosporins. This can lead to allergic reactions, such as anaphylaxis, which can cause a drop in blood pressure.