Can the normobaric oxygen paradox (NOP) increase reticulocyte count after traumatic hip surgery?

J Clin Anesth. 2013 Mar;25(2):129-34. doi: 10.1016/j.jclinane.2012.06.021. Epub 2013 Jan 17.


Study objective: To determine if the normobaric oxygen paradox (NOP) was effective in increasing reticulocyte count and reducing postoperative requirements for allogeneic red blood cell transfusion after traumatic hip surgery.

Design: Prospective, randomized, double blinded, multi-center study.

Setting: Surgical wards of two academic hospitals.

Patients: 85 ASA physical status 1 and 2 patients undergoing surgery for traumatic hip fracture.

Interventions: Patients were randomly assigned to receive 30 minutes of air [air group (control); n = 40] or 30 minutes of 100% oxygen (O2 group; n = 14) at 15 L/min every day from the first postoperative day (POD 1) until discharge.

Measurements: Venous blood samples were taken at admission and after surgery on POD 1, POD 3, and POD 7. Hemoglobin (Hb), hematocrit (Hct), reticulocytes, hemodynamic variables, and transfusion requirements were recorded, as were hospital length of stay (LOS) and mortality.

Main results: Full analysis was obtained for 80 patients. On hospital discharge, the mean increase in reticulocyte count was significantly higher in the O2 group than the air group. Percent variation also increased: 184.9% ± 41.4% vs 104.7% ± 32.6%, respectively; P < 0.001. No difference in Hb or Hct levels was noted at discharge. Allogeneic red blood cell transfusion was 7.5% in the O2 group versus 35% in the air group (P = 0.0052). Hospital LOS was significantly shorter in the O2 group than the air group (7.2 ± 0.7 days vs 7.8 ± 1.6 days, respectively; P < 0.05).

Conclusions: Transient O2 administration increases reticulocyte count after traumatic hip surgery. Hospital LOS also was shorter in the O2 group than the control group. Allogeneic red blood cell transfusion was reduced in the O2 group but it was not due to the NOP mechanism.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anemia / prevention & control
  • Double-Blind Method
  • Erythrocyte Transfusion
  • Female
  • Hematocrit
  • Hemoglobins / metabolism
  • Hip Fractures / blood
  • Hip Fractures / surgery*
  • Humans
  • Length of Stay / statistics & numerical data
  • Male
  • Oxygen Inhalation Therapy / methods*
  • Postoperative Care / methods*
  • Postoperative Complications / prevention & control
  • Prospective Studies
  • Reticulocyte Count


  • Hemoglobins