The effects of cross-linked hemoglobin on regional vascular conductance in dogs

Effect of the blood substitute diaspirin crosslinked hemoglobin in rat mesenteric and human radial collateral arteries

The actions of the blood substitute diaspirin crosslinked hemoglobin (DCLHb) were investigated in rat (small mesenteric artery) and human (radial collateral artery) resistance vessels mounted in a wire myograph for isometric tension recording. DCLHb did not contract resting vessels from rats, but vasoconstrictor responses were observed in isolated arteries and perfused mesenteric beds prestimulated with threshold concentrations of methoxamine. The DCLHb contractile responses were greatly attenuated by N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME) or endothelial removal, whereas BQ-123 (endothelin A receptor antagonist), prazosin (alpha1-adrenoceptor antagonist), or indomethacin (cyclooxygenase inhibitor) had no effect. Endothelium-dependent relaxations to carbachol in both rat mesenteric and human radial collateral artery were inhibited by DCLHb. Relaxations to carbachol were studied in the presence of L-NAME or 25 mM KCl to investigate the effect of DCLHb on endothelium-derived hyperpolarizing factor (EDHF) and nitric oxide, respectively. In both rat and human vessels, EDHF-mediated relaxations were not affected by DCLHb preincubation, whereas the nitric oxide component of carbachol-induced relaxations was practically abolished. In conclusion, inhibition of the effects of basal nitric oxide release underpins the vasoconstrictor effects of DCLHb. DCLHb effectively abolishes the nitric oxide component of carbachol-induced relaxation, with no effect on the EDHF-mediated component in both isolated rat mesenteric and human radial collateral arteries.

Current status of artificial oxygen carriers

Artificial oxygen carriers may be grouped into modified hemoglobin solutions and fluorocarbon emulsions. In animal experiments, both have been shown to be efficacious in improving tissue oxygenation and as substitutes for blood transfusions. Advantages and disadvantages are being discussed in this article as well as the latest steps in the clinical development.

Bovine polymerized hemoglobin increases cardiac oxygen consumption and alters myocardial substrate metabolism in conscious dogs: role of nitric oxide

We investigated the effect of bovine polymerized hemoglobin-based oxygen carrying (HBOC) solution on myocardial oxygen consumption (MVO2) and substrate use. At 15 min after the end of HBOC infusion (20% blood volume, i.v.) in nine permanently instrumented conscious dogs, mean arterial pressure and coronary blood flow were both increased by 41+/-5% and 93+/-20% (p<0.01) without affecting late diastolic coronary resistance and left ventricular dP/dtmax. Administration of HBOC did not affect arterial PO2 or O2 content, but significantly decreased coronary sinus PO2 and O2 content by 21+/-3% and 36+/-3%, respectively. MVO2 was increased from 7.2+/-0.8 to 15+/-1.8 ml O2/min (p<0.01). Despite an increase in triple product from 44+/-2 to 56+/-3 (p<0.01) 15 min after HBOC, the ratio of MVO2 and triple product was markedly elevated by 62+/-19%. Myocardial free fatty acid consumption was decreased from 14+/-1 to 4.5+/-2.2 microEq/min, whereas consumption of lactate increased from 19+/-6 to 69+/-10 micromol/ min and that of glucose increased from 1.0+/-0.5 to 10+/-3 mg/min (all p values, <0.05). These metabolic changes were not observed in dogs that received angiotensin II at a dose used (20-40 ng/kg/min, i.v.) to match those hemodynamic effects of HBOC. These results suggest that administration of HBOC increases coronary blood flow and MVO2 and shifts cardiac metabolism from using free fatty acid to using lactate and glucose in conscious dogs at rest. These metabolic changes are independent of the HBOC-induced change in hemodynamics.