The effect of hemodilution on free flap survival: A systematic review of clinical and experimental studies.

BACKGROUND: Acute normovolemic hemodilution (ANH) has been proposed as a microsurgical technique to improve blood flow in free flaps. OBJECTIVE: Here, we present the first systematic review of clinical and experimental studies on the effect of ANH. METHODS: We performed a systematic literature search of PubMed, Medline, the Cochrane Library, Google Scholar, and ClinicalTrials.gov using search strategies and a review process in agreement with the PRISMA statement and the Cochrane Handbook for systematic reviews of interventions. PICO criteria were defined before bibliometric processing of the retrieved articles, which were analyzed with the SYRCLE RoB tool for risk of bias and the GRADE scale for level of evidence. RESULTS: We retrieved 74 articles from the literature search, and after processing according to PICO criteria, only four articles remained, all of which were experimental. The rating for risk of bias was uncertain according to SYRCLE RoB results, and the level of evidence was low according to GRADE evaluation. CONCLUSIONS: There is no clinical evidence for the effect of ANH on microcirculation in free flaps, and experimental studies provide weak evidence supporting the use of hemodilution in reconstructive microsurgery.