Effects of Preoperative Hemoglobin on Microsurgical Reconstruction and Perioperative Blood Transfusion Requirement: A Meta-Analysis and Systematic Review of the Literature.

[PURPOSE] Although blood loss in microsurgical reconstruction is rarely large enough to be life-threatening, preoperative anemia can be a particular issue in terms of postoperative morbidity, impaired wound healing, and compromised tissue viability. We seek to review the effect of preoperative hemoglobin (Hgb) levels on perioperative blood transfusion (PBT) requirements and complications to guide management of patients with preexisting anemia undergoing reconstruction.

[METHODS] PubMed, Embase, and Scopus were queried for relevant articles. Inclusion criteria were as follows: original studies investigating outcomes and PBT requirements in flap-based reconstruction based on preoperative Hgb levels. Patient and study characteristics were analyzed using descriptive statistics. A meta-analysis was conducted to assess transfusion requirements across the included studies using Stata (version 18.0 Stata Corp, College Station, Texas, USA). The Fisher method was used to aggregate individual study p values into a single combined value to statistically assess the combined findings, where a p value of < 0.05 was set as statistically significant.

[RESULTS] One thousand three hundred and eighty-nine studies were screened for title and abstract relevance, 14 of which met the inclusion criteria, including a total of 61,116 patients. Meta-analysis of the studies revealed a PBT requirement of 36.2% for anemic individuals, significantly higher than the 20.0% for those with normal preoperative Hgb levels (p < 0.001), with an average 4.9 versus 2.4 units of packed red blood cells being transfused (p < 0.001). The majority of studies concluded that preoperative anemia was associated with medical complications, such as myocardial infarction, stroke, and infection (p < 0.001). While six studies reported a significant relationship between low preoperative Hgb and flap morbidity (flap loss and partial flap necrosis), two studies found no correlation. The overall postoperative complication rate across the studies was 42.2% among patients with low preoperative Hgb levels, whereas the nonanemic group demonstrated a markedly lower rate of 13.9% (p < 0.001).

[CONCLUSION] The existing evidence is strongly suggestive of increased PBT requirement in patients with anemia, highlighting the necessity for preoperative optimization of Hgb levels and intraoperative monitoring. While preliminary evidence demonstrates a relationship between anemia and medical complications, more research is warranted to characterize the specific association between preoperative Hgb levels and flap morbidity.