title: Intestinal and sublingual microcirculation are more severely compromised in hemodilution than in hemorrhage.
abstract: The alterations in O2 extraction in hemodilution have been linked to fast red blood cell (RBC) velocity, which might affect the complete release of O2 from Hb. Fast RBC velocity might also explain the normal mucosal-arterial Pco2 (ΔPco2). Yet sublingual and intestinal microcirculation have not been completely characterized in extreme hemodilution. Our hypothesis was that the unchanged ΔPco2 in hemodilution depends on the preservation of villi microcirculation. For this purpose, pentobarbital-anesthetized and mechanically ventilated sheep were submitted to stepwise hemodilution (n = 8), hemorrhage (n = 8), or no intervention (sham, n = 8). In both hypoxic groups, equivalent reductions in O2 consumption (V̇o2) were targeted. Microcirculation was assessed by videomicroscopy, intestinal ΔPco2 by air tonometry, and V̇o2 by expired gases analysis. Although cardiac output and superior mesenteric flow increased in hemodilution, from the very first step (Hb = 5.0 g/dl), villi functional vascular density and RBC velocity decreased (21.7 ± 0.9 vs. 15.9 ± 1.0 mm/mm(2) and 1,033 ± 75 vs. 850 ± 79 μm/s, P < 0.01). In the last stage (Hb = 1.2 g/dl), these variables were lower in hemodiution than in hemorrhage (11.1 ± 0.5 vs. 15.4 ± 0.9 mm/mm(2) and 544 ± 26 vs. 686 ± 70 μm/s, P < 0.01), and were associated with lower intestinal fractional O2 extraction (0.61 ± 0.04 vs. 0.79 ± 0.02, P < 0.01) but preserved ΔPco2 (5 ± 2 vs. 25 ± 4 mmHg, P < 0.01). Therefore, alterations in O2 extraction in hemodilution seemed related to microvascular shunting, not to fast RBC velocity. The severe microvascular abnormalities suggest that normal ΔPco2 was not dependent on CO2 washout by the villi microcirculation. Increased perfusion in deeper intestinal layers might be an alternative explanation.
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Ferrara
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Vanina Siham
authors.initials: VS
authors.lastname: Kanoore Edul
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Enrique
authors.initials: E
authors.lastname: Martins
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Héctor Saúl
authors.initials: HS
authors.lastname: Canales
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Carlos
authors.initials: C
authors.lastname: Canullán
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Gastón
authors.initials: G
authors.lastname: Murias
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Mario Omar
authors.initials: MO
authors.lastname: Pozo
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and.
authors.forename: Elisa
authors.initials: E
authors.lastname: Estenssoro
authors.affiliation: Academic Medical Center, Department of Translational Physiology, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Can
authors.initials: C
authors.lastname: Ince
authors.affiliation: Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina; and arnaldodubin@gmail.com.
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Dubin
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism; D006438:Hemodilution / Q000379:methods; D006470:Hemorrhage / Q000378:metabolism / Q000473:pathology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000098:blood supply* / Q000503:physiopathology*; D008833:Microcirculation / Q000502:physiology*; D009060:Mouth Floor / Q000098:blood supply* / Q000378:metabolism / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000502:physiology; D012121:Respiration, Artificial / Q000379:methods; D012756:Sheep
chemical_list: D002245:Carbon Dioxide
keywords: Pco2; anemia; hemorrhage; hypoxia; microcirculation