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

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.