Increased tissue PO2 and decreased O2 delivery and consumption after 80% exchange transfusion with polymerized hemoglobin.
The O2-carrying blood substitute based on polymerized bovine hemoglobin (PBH) was used to determine efficacy in maintaining tissue Po2 after an 80% isovolemic blood exchange leading to a hematocrit of 19% [5.4 g Hb/dl from red blood cells (RBCs) and 6.3 g Hb/dl from PBH]. Effects were studied in terms of O2 delivery, O2 extraction, and tissue Po2 at the microcirculatory level at 1, 12, and 24 h after exchange transfusion in awake hamsters prepared with a window chamber model. At 1 h after exchange, arteriolar and venular diameters were decreased compared with baseline. Arteriolar diameter did not fully recover at 12 h after exchange, but venular diameter returned to normal. At 24 h after exchange, arteriolar and venular diameters were not different from baseline. Combining diameter and flow velocity data allowed us to calculate arteriolar and venular flows. At 1 h after exchange, arteriolar and venular flow was reduced compared with baseline. Arteriolar flow was lower at 12 h after exchange and recovered after 24 h. The number of capillaries with RBC passage [functional capillary density (FCD)] at 1 h after exchange with PBH was significantly lower than baseline. FCD remained decreased at 12 h; at 24 h after exchange transfusion, FCD was fully recovered. Tissue Po2 was maximal at 1 h after exchange and decreased progressively at 12 and 24 h after exchange. O2 release to the tissue was minimal at 1 h and increased at 12 and 24 h after exchange. These results suggest the impairment of tissue O2 metabolism after introduction of PBH into the circulation, which is mitigated as PBH concentration declines.
Dept. of Bioengineering, 0412, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0412, USA. pcabrales@ucsd.edu
Pedro
P
Cabrales
Amy G
AG
Tsai
Marcos
M
Intaglietta
D000818:Animals; D001160:Arterioles; D001802:Blood Substitutes / Q000493:pharmacokinetics*; D001803:Blood Transfusion; D002245:Carbon Dioxide / Q000097:blood; D006224:Cricetinae; D006400:Hematocrit; D006454:Hemoglobins; D008647:Mesocricetus; D008706:Methemoglobin / Q000494:pharmacology; D010100:Oxygen / Q000493:pharmacokinetics*; D010101:Oxygen Consumption / Q000502:physiology*; D010313:Partial Pressure
D001802:Blood Substitutes; D006454:Hemoglobins; C079129:hemoglobin polymer; D002245:Carbon Dioxide; D008706:Methemoglobin; D010100:Oxygen