Expediting red blood cell transfusions by syringing causes significant hemolysis.

BACKGROUND: Techniques commonly used to expedite blood transfusions include pneumatically pressurizing red blood cell (RBC) bags or manual syringing its contents. We compared these techniques on RBC hemolysis using a simulated transfusion model. STUDY DESIGN AND METHODS: Fifteen warmed RBC units that were 12.3 ± 4.3 (95% confidence interval [CI], 10.1-14.5) days old were each subjected to two experimental rapid transfusion techniques. RBCs from each technique were directed through 18- and 22-gauge cannulas attached to blood administration sets. One technique involved RBC bag pressurization to 300 mmHg. The other employed a 20-mL syringe to effect forceful, manual aspiration from the RBC bag followed by forceful, manual RBC injection. The control group was gravity driven without cannulas. Free hemoglobin (Hb) concentrations were measured and percent hemolysis was calculated. RESULTS: Free Hb concentrations and percent hemolysis (median [95% CI]) were similar in the control (0.05 [0.03-0.08] g/dL and 0.13% [0.09%-0.17%], respectively) and pressurized experiments (0.06 [0.05-0.09] g/dL; 0.14% [0.12%-0.22%]), respectively. Syringing resulted in 10-fold higher free Hb concentrations (0.55 [0.38-0.92] g/dL) and percent hemolysis (1.28% [1.03%-2.15%]) than when employing the control (p < 0.0001) or pressurization (p < 0.0001) techniques. Cannula sizes studied did not affect hemolysis. CONCLUSION: Forceful manual syringing caused significant hemolysis and high free Hb concentrations. Pressurizing RBC bags induced no more hemolysis than after gravity-facilitated transfusions. Syringing to expedite RBC transfusions should be avoided in favor of pneumatic RBC bag pressurization.

Reinfusate Heparin Concentrations Produced by Two Autotransfusion Systems.

OBJECTIVES: Cell saver reinfusate ideally should contain low, clinically insignificant heparin concentrations. The American Association of Blood Banks has defined the clinically insignificant threshold as 0.5 IU/mL. Furthermore, there is uncertainty about the meaning of cell saver "heparin elimination rates." These concerns prompted the authors' independent investigation of reinfusate heparin concentrations of devices used in their institution. It was hypothesized that cell saver reinfusates contain clinically insignificant heparin concentrations. DESIGN: Two prospective, pragmatic, sequential, observational, single-center studies. SETTING: University teaching hospital. PARTICIPANTS: A total of 32 and 31 patients for on-pump cardiac surgery were enrolled in the Sorin (Dideco) Electa and Sorin Xtra studies, respectively. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Postcardiac surgery reinfusate heparin concentrations were measured using a modified anti-Xa chromogenic assay. Heparin concentrations above 0.5 IU/mL were present in 56% (95% confidence interval, 35% to 68%) of Sorin Xtra reinfusates. Heparin concentrations in the Sorin (Dideco) Electa reinfusates were lower than recommended in 29 of 32 reinfusates. Only 3 of 32 Sorin (Dideco) Electa reinfusates (9.4%; 95% confidence interval 3.2% to 24%) exhibited heparin concentrations exceeding 0.5 IU/mL. CONCLUSIONS: Sorin (Dideco) Electa reinfusates contained heparin concentrations below the American Association of Blood Banks recommended threshold in 90.6% of cases, while Sorin Xtra reinfusate heparin concentrations exceeded this recommendation in 56% of cases. Measurement of cell saver reinfusate heparin concentrations necessitates the use of a modified chromogenic assay. Studies explicitly should confirm that such a modification was indeed used. Periodic quality control of reinfusate composition is recommended.

Heparinase thromboelastography compared with activated coagulation time for protamine titration after cardiopulmonary bypass.

OBJECTIVE: The present study is a comparison of two point-of-care (POC) tests as endpoints of protamine titration after CPB. The authors hypothesized that using the heparinase-kaolin thromboelastography (TEG-HK) R-time difference would more readily identify residual heparin necessitating additional protamine than when using activated coagulation time (ACT). The primary endpoint was the between-group difference in protamine dose. Whether this approach would lessen postoperative bleeding and sequelae also was investigated. DESIGN: Single center, blinded, prospective, randomized study. SETTING: University teaching hospital. PARTICIPANTS: Eighty-two adult patients for on-pump coronary artery bypass and/or valve surgery. INTERVENTIONS: Patients were randomized. In the ACT group, protamine was titrated until ACT did not exceed baseline by more than 10%. In the TEG group, a TEG-HK R-time difference less than 20% was targeted. Protamine was repeated to achieve the endpoints. Clinicians in the ACT group were blinded to TEG data and vice versa. MEASUREMENTS AND MAIN RESULTS: There was no between-group difference in total protamine dose (3.9 ± 0.6 and 4.2 ± 0.7; 95% CI of the difference between means: -0.544 to 0.008 mg/kg; p = 0.057) or protamine:heparin ratios (1.3:1 and 1.4:1; 95% CI of the difference between means: -0.05 to 0.03 mg/mg; p = 0.653). In the ACT group, 17% of patients required a second protamine dose, and in the TEG group, 24% of patients required a second protamine dose. No between-group differences in the postoperative transfusion requirements or intensive care unit length of stay were demonstrated. CONCLUSION: No difference was identified in protamine dosing using either ACT or TEG-HK R-time difference as endpoints. Heparinase TEG may be useful for monitoring heparin reversal.

Arterial oxygenation and one-lung anesthesia.

PURPOSE OF REVIEW: In the presence of the obligatory shunt during one-lung ventilation, arterial oxygenation is determined by the magnitude of the shunt in addition to the oxygen content of the mixed venous blood coursing through that shunt. The present discussion aims to heighten awareness of factors determining arterial oxygenation during one-lung anesthesia, other than the magnitude of the shunt and dependent lung low-ventilation perfusion units. RECENT FINDINGS: A convenient way to increase mixed venous and thereby arterial oxygenation is to raise cardiac output. While this approach has achieved some success when increasing cardiac output from low levels, other studies have highlighted limitations of this approach when cardiac output attains very high levels. The effect of anesthesia techniques on the relationship between oxygen consumption and cardiac output could also explain unanswered questions regarding the pathophysiology of arterial oxygenation during one-lung anesthesia. SUMMARY: The effects of anesthesia techniques on oxygen consumption, cardiac output and therefore mixed venous oxygenation can significantly affect arterial oxygenation during one-lung anesthesia. While pursuing increases in cardiac output may, under limited circumstances, benefit arterial oxygenation during one-lung ventilation, this approach is not a panacea and does not obviate the necessity to optimize dependent lung volume.