A second dose of intraoperative antibiotic is indicated in which scenario?

• A. Significant blood loss
• B. Surgery longer than 2 hours
• C. Immunocompromise
• D. Renal failure

Answer: (B)

Intraoperative antibiotic prophylaxis aims to keep the drug level in the tissues high enough to prevent surgical site infection throughout the operation. After the initial dose is given before the incision, the drug concentration falls as it distributes and is cleared from the body. If the operation lasts long enough that those levels would drop below a protective threshold, a second dose is given to re-establish effective tissue concentrations. For many standard prophylactic regimens, this re-dosing is indicated when the surgery extends beyond about two hours, ensuring continuous protection during the period of greatest infection risk. While factors like heavy blood loss or renal function can influence dosing strategies, the scenario that most directly triggers a second intraoperative dose in this context is a procedure lasting longer than two hours.