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Elevated troponin I level with hemoglobin based oxygen carrying solutions (HBOCs) as a priming solution despite improved left ventricular function

^a Resident in Cardiothoracic Surgery, Loyola University, Chicago Stritch School of Medicine, 2160 S 1st Avenue, Maywood, IL 60153, USA
^b Division of Cardiac Surgery, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114, USA

*Corresponding author. Tel.: +1 708 327 2503; fax: +1 708 327 2504.

E-mail address: Sneragi{at}yahoo.com (S. Neragi-Miandoab).

Stroma free hemoglobin based oxygen-carrying solutions (HBOCs) have been shown to have the capability to transport oxygen, suggesting their use as a temporary blood substitute to maintain oxygenation of tissue. HBOCs might be the proper priming solution; however, elevated troponin associated with their application might be a major concern, particularly in patients with damaged myocardium. This study was performed in mongrel dogs (n=14). The animals underwent cardiac arrest with cardioplegic solution and aortic clamping using cardiopulmonary bypass (CPB). HBOC was used as a priming solution for CPB in the study group, and Lactated Ringer's in the control group. The extreme hemodilution in the study group was achieved by replacing more than 80% of the animal's blood with HBOC. A right heart bypass was performed to control the cardiac output. The hemodynamic parameters were measured with increasing cardiac output before and after CPB. At a cardiac output of 2500 ml/min, LAP (19±9 mmHg vs. 8.7±1.3 mmHg in the HBOCs group) and LVEDP (22±16 mmHg in the control group vs. 11±2.8 mmHg in the HBOC group) were significantly higher in control animals. The overall coronary sinus flow did not show any significant difference between both groups. The PO₂ in the HBOCs group was slightly higher (534±10 mmHg vs. 494±71 mmHg) at 30 min after removal of aortic clamp compared to PO₂ in control group. Post-ischemic troponin I level was increased in both groups, however, it was significantly higher in HBOCs group (49.64±48.58 ng/ml) compared to its level in control group (28.33±17.2 ng/ml). After the priming was completed and CPB was initiated, the hematocrit in the study group was 5.37±3.7% compared to 15±3.3% in the control group. However, the hemoglobin (Hb) in the study group remained higher throughout the experiment compared to control group, 8.34±1.55 g/dl vs. 5.37±1.04 g/dl, respectively. HBOC based priming permits cardiopulmonary bypass at a very low hematocrit with a better preservation of myocardium and adequate oxygen supply. However, elevated troponin I at the postischemic phase is a serious concern and its significance needs to be addressed before broad clinical application of HBOC.

Key Words: Artificial blood; LVEDP; LAP; Oxygen carrying