SA1 - Beyond Surgical Site Infection: Redefining Readmission Drivers in Head and Neck Free Flap Reconstruction

Abstract: Statement of the Problem: Thirty-day readmission following head and neck free flap reconstruction remains a significant quality metric and financial burden. In the ACS-NSQIP database, nearly half of readmissions are classified under "Other" diagnoses, limiting meaningful interpretation and obscuring potentially preventable, head-and-neck-specific complications. Without systematic characterization, these diagnoses cannot inform targeted quality improvement efforts. This study aimed to decode the "Other" readmission category to identify clinically actionable drivers of readmission following free tissue transfer.

Materials and Methods: We performed a retrospective cohort study using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2012 to 2022. Adult patients undergoing head and neck free tissue transfer were identified using CPT codes 15756, 15757, and 21045. The primary outcome was 30-day readmission. Readmission diagnoses categorized by NSQIP as "Other" were extracted using associated ICD-9 and ICD-10 codes. These codes were systematically reviewed and grouped into clinically relevant organ system categories. This was an objective database analysis; no subjective clinical interpretation beyond ICD code classification was performed.

Method of Data Analysis: The total sample included 5,160 patients. Study duration spanned 11 years (2012-2022). Descriptive statistics were used to calculate readmission rates, timing of readmission, and frequency of diagnostic categories. Continuous variables were reported as medians with interquartile ranges (IQR). Categorical variables were expressed as frequencies and percentages. Comparisons were performed using chi-square testing for categorical variables and appropriate nonparametric testing for continuous variables. Statistical significance was defined as P < .05. All analyses were conducted using Stata version 18.5 (StataCorp, College Station, TX).

Results: The overall 30-day readmission rate was 8.2% (424/5,160). Median time to readmission was 12 days (IQR 8-18). The highest incidence occurred during postoperative days 7-14, accounting for 42% of readmissions. Traditional NSQIP-defined complications comprised 50.5% of readmissions, including surgical site infection (27.6%), wound disruption (6.6%), sepsis (3.3%), and pneumonia (3.3%).

However, 49.5% of readmissions (210/424) were categorized as "Other," representing the single largest classification group. Systematic analysis of these ICD codes identified 3 predominant categories:

1. Fluid/Metabolic (38%) – dehydration, electrolyte disturbances, and acute kidney injury.
2. Respiratory (21%) – aspiration pneumonia and respiratory failure.
3. Post-procedural (32%) – wound complications not meeting strict SSI criteria, hematoma, and seroma.

Fluid/metabolic and respiratory complications together accounted for more than 60% of "Other" readmissions. These diagnoses are closely associated with postoperative dysphagia, impaired oral intake, and aspiration risk; common sequelae of head and neck reconstruction.

Outcomes and Data: Nearly half of all readmissions were attributable to complications not captured by traditional NSQIP surgical metrics. The majority occurred within two weeks of discharge, suggesting a critical early post-discharge vulnerability window. The predominance of dehydration and aspiration-related events indicates potentially modifiable risk factors directly related to swallowing dysfunction and postoperative nutritional management.

Conclusions: The NSQIP "Other" readmission category conceals a substantial burden of clinically meaningful, head-and-neck-specific complications. Dehydration and aspiration represent leading drivers of readmission and are not adequately reflected in standard surgical quality metrics. Implementation of structured swallow evaluations prior to discharge, enhanced nutrition and hydration protocols, early outpatient follow-up within 7-10 days, and remote hydration monitoring may significantly reduce preventable readmissions. Reframing quality assessment to incorporate procedure-specific complications is essential for improving outcomes in head and neck free flap reconstruction.