Elevated troponin I level with hemoglobin based oxygen carrying solutions (HBOCs) as a priming solution despite improved left ventricular function.
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.
Loyola University, Chicago Stritch School of Medicine, 2160 S 1st Avenue, Maywood, IL 60153, USA. Sneragi@yahoo.com
Siyamek
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Neragi-Miandoab
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Vlahakes