Anästhesie und klinische Forschung
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The Impact of Routine Norepinephrine Infusion on Hemodilution and Blood Transfusion in Cardiac Surgery

David J Canty, Martin Kim, Colin F Royse, David T Andrews, Stephen Bottrell and Alistair G Royse

Background: Hemodilution and blood transfusion are associated with poor outcome after cardiac surgery. We hypothesized that routine norepinephrine infusion commenced prior to anesthesia induction during on-bypass cardiac surgery would reduce intraoperative hemodilution and red cell transfusion.

Methods: Two cohorts of consecutive cardiac surgery patients at different time periods were retrospectively reviewed for perioperative hemoglobin, creatinine concentrations and units of red cells transfused. Patients in group NE (n=72, in 2010) all received standardized hemodynamic management by a single anesthesiologist with low dose norepinephrine infusion commenced at 3-5 μg.min-1 (18-30 nmol.min-1, 0.24-0.4 nmol.kg-1.min-1) commencing prior to anesthetic induction and continued into the postoperative period. In the absence of blood loss, hemodynamic stability was achieved using vasopressors and inotropes rather than fluid administration, in an attempt to reduce hemodilutional anemia and trigger for red cell transfusion. Controls (n=94, in 2005) received selective norepinephrine infusion post cardiopulmonary bypass for persistent hypotension and vasodilation. There were no major changes to surgical or perfusion technique in the time period between cohorts, and the transfusion trigger remained the same at Hb<70 g/L.

Results: Intraoperatively, hemoglobin concentrations were higher in group NE compared with controls (p<0.0001) despite lower baseline values (139 ± 19 vs 133 ± 15, P=0.028). Additionally, fewer units of red cells were transfused in the NE group intraoperatively (0.2 ± 0.6 units/patient) compared with controls (0.53 ± 1.47, p=0.041). Maximum postoperative rise in serum creatinine concentration (μmol.L-1) was not significantly different (NE 26 ± 32, controls 30 ± 57, p=0.49 and at discharge 3 ± 53 vs. 5 ± 30, p=0.39). NE group patients were at increased risk of bleeding, having received more extensive surgery (p=0.042), longer clamp-time (p=0.009) and no aprotinin compared to 74% of controls.

Conclusions: This study shows proof of concept that during on-bypass cardiac surgery, routine low dose norepinephrine infusion is associated with reduced hemodilution and intraoperative red cell transfusion without increasing postoperative serum creatinine.