This interesting retrospective data analysis from a prospective database regarding the outcome of elective spine surgery in approximately 25,000 patients suggests that preoperative anemia should be regarded as an independent risk factor for perioperative and postoperative complications. In congruence with the results of other elective surgical populations, within a thirty-day period anemia increased mortality by 0.4%, surgical redo by 3.1%, length of hospital stay (LOS) by more than 1 day and the complication rate by 7.5%.
Interestingly, these outcomes were worse in moderate anemia as opposed to severe anemia. All levels of anemia were associated with prolonged LOS and poorer postoperative or 30-day outcomes in patients undergoing elective spine surgery. Patients with moderate anemia had the greatest risk for adverse outcomes. These findings persisted after removal from analysis of patients that received intra- and/or postoperative transfusions. The authors discuss the fact that moderate anemia had the highest odds for adverse outcomes (twice as likely than patients without anemia) and come up with three possible explanations: 1) insufficient statistical power due to a low number of patients with severe anemia, 2) physiological adaptation such as ischemic preconditioning to a chronic low level of oxygenation before surgery, or 3) the effect of specially attentive care to anemic patients by providers of care. The fact itself, however, is supported in part by at least two other studies that distinguish the outcome of various levels of preoperative anemia. The outcome depending on the severity of anemia surely deserves attention in further studies.
– Thomas Frietsch