3.2 Effect of anaemia on outcomes
Question 4 (Aetiological question) (GNQ1)
In patients undergoing surgery, is anaemia an independent risk factor for adverse outcomes?
Anaemia has been defined by the World Health Organization (WHO) as a haemoglobin level <130 g/L in males and <120 g/L in females.
No Level I evidence was identified for cardiac surgery. One fair-quality systematic review was identified for noncardiac surgery. Of the Level II studies identified that investigated the relationship of anaemia as an adverse outcome in patients undergoing surgery, 10 involved cardiac surgery,18–27 and 8 involved noncardiac surgery.19,28–34 A further 14 cardiac35–48 and 11 noncardiac49–59 Level III studies were identified.
Preoperative anaemia is independently associated with an increased risk of morbidity and mortality.
Collectively, these studies provide a good evidence base – in cardiac and noncardiac surgical patients – for an independent relationship between preoperative anaemia and an increased risk of postoperative morbidity and mortality.
As would be expected, preoperative anaemia is associated with an increased likelihood of red blood cell (RBC) transfusion.
| EVIDENCE STATEMENTS – anaemia | Evidence | Consistency | Clinical impact | Generalisability | Applicability |
|---|---|---|---|---|---|
| In patients undergoing cardiac surgery, preoperative anaemia is associated with an increased risk of morbidity and mortality. | |||||
| In patients undergoing cardiac surgery, preoperative anaemia is associated with an increased likelihood of transfusion. | |||||
| In patients undergoing cardiac surgery, preoperative and intraoperative anaemia are associated with increased hospital length of stay. | X | X | |||
| In patients undergoing cardiac surgery, an intraoperative/operative haematocrit level below 20% is associated with an increased risk of morbidity and mortality. | |||||
| In patients undergoing noncardiac surgery, preoperative anaemia is associated with an increased risk of postoperative morbidity and mortality. | |||||
| In patients undergoing noncardiac surgery, preoperative anaemia is associated with an increased likelihood of transfusion and increased hospital length of stay. | X | ||||
| In patients undergoing noncardiac surgery, postoperative anaemia is associated with an increased risk of morbidity and mortality. | X | ||||
| In patients undergoing noncardiac surgery, postoperative anaemia is associated with an increased likelihood of transfusion. | NA |
(See Table 2.2)