title: Intraoperative transfusion threshold and tissue oxygenation: a randomised trial.
abstract: OBJECTIVE
  Transfusion with allogeneic red blood cells (RBCs) may be needed to maintain oxygen delivery during major surgery, but the appropriate haemoglobin (Hb) concentration threshold has not been well established. We hypothesised that a higher level of Hb would be associated with improved subcutaneous oxygen tension during major spinal surgery.
  
  
  METHODS
  Fifty patients aged 18 years or older scheduled for spinal fusion with instrumentation were included and randomised to receive RBCs at either a Hb concentration of 7·3 g dL(-1) (restrictive group) or a Hb concentration of 8·9 g dL(-1) (liberal group) (Registration no.: H-C-2009-072). Oxygen tension was measured with a polarographic electrode placed subcutaneously over the left deltoid muscle. The primary endpoint was subcutaneous oxygen tension at the time most patients were still undergoing surgery.
  
  
  RESULTS
  Forty-eight patients were included in the intention-to-treat analysis; 25 patients in the restrictive group and 23 patients in the liberal group. The median change in subcutaneous oxygen tension 60 min after surgical incision was -0·79 and -0·75 kPa in the restrictive and the liberal groups, respectively (P = 0·78). No significant difference was found in the lowest subcutaneous oxygen tension; -2·07 vs. -1·95 kPa in the restrictive and the liberal groups, respectively (P = 0·85).
  
  
  CONCLUSIONS
  A Hb concentration transfusion threshold of 8·9 g dL(-1) was not associated with a higher subcutaneous oxygen tension during major spinal surgery than a threshold of 7·3 g dL(-1), but the trial was compromised by methodological difficulties.
authors.affiliation: Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. Kamilla.nielsen.kn@gmail.com
authors.forename: K
authors.initials: K
authors.lastname: Nielsen
authors.forename: B
authors.initials: B
authors.lastname: Dahl
authors.forename: P I
authors.initials: PI
authors.lastname: Johansson
authors.forename: S W
authors.initials: SW
authors.lastname: Henneberg
authors.forename: L S
authors.initials: LS
authors.lastname: Rasmussen
mesh_terms: D000328:Adult; D000368:Aged; D017707:Erythrocyte Transfusion / Q000379:methods*; D005260:Female; D006454:Hemoglobins; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000032:analysis* / Q000378:metabolism*; D013123:Spinal Fusion / Q000379:methods
chemical_list: D006454:Hemoglobins; D010100:Oxygen