Objective:
Free flap transfer for defects in the head and neck region after cancer ablation surgery or trauma has gained worldwide acceptance but total failure of the flap still caused the devastating result. Therefore, many studies have dedicated to find the potential risk factors and renal failure was one possible etiology. Furthermore, the crude incidence rate of dialysis showed increased trend in Taiwan from 2000 to 2017. Thus, we conducted this study to clarify whether end stage renal disease (ESRD) is a risk factor which will jeopardize flap survival in microsurgical head and neck reconstruction.

Material and Methods:
This retrospective study enrolled patients who received free flap reconstruction of the head and neck region at Hualien Tzu Chi Hospital from January 2010 to December 2019. The cases who have been declared the medical expenses from National Health Insurance (NHI) by using "Specific Diagnosis and Treatment Code” will be sorted to dialysis group. On the other hand, non-dialysis group was randomly selected at a ratio of 1:10. Both dialysis and non-dialysis groups were frequently matched by age and gender. The primary outcomes were flap survival rate, take-back rate, and salvage rate for the dialysis group and non-dialysis group. Risk evaluation of flap failure was also conducted. Finally, post-operative one-year cumulative survival rate was also measured.

Results:
There are 14 cases in dialysis group and 140 cases in non-dialysis group. The median age in the dialysis and non-dialysis group were 57.5 and 58, respectively. No significant differences were noted in terms of comorbidities except diabetes mellitus, hypertension and coronary artery disease. About postoperative outcomes, the flap survival rate was 100% and 92.9% in the dialysis and non-dialysis groups, respectively (p = 0.6). There were total 23 patients received take-back surgery, including 2 in the dialysis group and 21 in the non-dialysis group (14.3% versus 15.0%; p = 1.000). Successful salvage was achieved in nine patients in the non-dialysis group (60%). Besides, the ratio of pneumonia (14.3% vs. 0.7%) were significantly greater in dialysis group than non-dialysis group. The ratio of prolonged ICU stay between dialysis group (42.9%) and non-dialysis group (10.7%) showed significant difference. Multivariate logistic regression analysis showed that dialysis was not independent predictor of flap failure (OR: 0.83; p = 0.864). The cumulative survival rate between dialysis and non-dialysis group showed significantly different (0.693 vs. 0.886; p = 0.039).

Conclusions:
This single-center study revealed no significant differences in free flap survival rate and successful salvage rate between patients with and without dialysis. Besides, ESRD under dialysis is not a risk factor to jeopardize the flap survival in microsurgical head and neck reconstruction. We suggest that it is necessary to carry out the further prospective, randomized controlled trials.

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