# Postoperative Antibiotic Escalation After Major Free-Flap Reconstruction Requiring ICU Admission: Associations with Day-1 Procalcitonin, Shock, and Microbiological Positivity

## TL;DR

This study finds that shock and higher procalcitonin levels on day 1 after surgery are linked to increased antibiotic use in ICU patients following major reconstructive surgery.

## Contribution

The study identifies shock and day-1 procalcitonin as early indicators of antibiotic escalation in ICU patients after free-flap surgery.

## Key findings

- Antibiotic escalation occurred in 71.4% of ICU admissions after major free-flap surgery.
- Shock was more common in patients who required antibiotic escalation.
- Patients with escalation had longer ventilation times and higher rates of positive cultures.

## Abstract

Major reconstructive free-flap surgery often requires ICU admission, yet early signals associated with postoperative antibiotic escalation remain poorly characterized. We conducted a single-center retrospective cohort study of 119 consecutive postoperative ICU admissions after major free-flap reconstruction. Exposures were postoperative day-1 procalcitonin (PCT) and documented postoperative shock; the primary endpoint was clinician-initiated antibiotic escalation (“upgrade”), and secondary endpoints were documented microbiological positivity and ICU mechanical ventilation duration. Escalation occurred in 85/119 admissions (71.4%). Day-1 PCT was higher with escalation (median 0.25 vs. 0.135 ng/mL; p = 0.033), and shock was more frequent (59/85 [69.4%] vs. 13/34 [38.2%]; p = 0.003). Escalation was associated with longer ventilation (median 3515 vs. 2170 min; p < 0.001) and higher rates of any positive culture (54/85 [63.5%] vs. 8/34 [23.5%]; p < 0.001). In multivariable logistic regression adjusting for operative time and intraoperative IV volume, shock remained independently associated with escalation (adjusted OR 3.52, 95% CI 1.48–8.36; p = 0.004), whereas log-transformed PCT was not (p = 0.224). PCT showed modest apparent discrimination for escalation (AUC 0.63), improving to 0.71 when combined with shock. These findings should be interpreted as observational associations with escalation behavior, supporting prospective evaluation of physiology-plus-biomarker stewardship approaches.