Hyperoxic ventilation at the critical haematocrit

Hyperoxic Ventilation in Critical Dilutional Anemia: Intestinal O2 Transport and Tissue Oxygenation

“…Our methods and criteria to determine Hct crit have been previously discussed. 9 However, as far as validity is concerned, we also observed both myocardial ischemia and global/intestinal tissue hypoxia to prove a critical level of hemodilution. The latter is documented by global and intestinal O 2 consumption, by intestinal tissue O 2 partial pressure and by intramucosal pH in our data.…”

“…86-23, revised 1985). Detailed anesthetic and surgical procedures have been described previously 9 and are therefore only briefly referred to.…”

“…8,10,37 Despite these potentially unfavorable effects, these authors report that hyperoxic ventilation was however followed by improved peripheral, 9,35,36 cerebral, 10 and myocardial oxygenation 9 as well as improved cerebral and myocardial function. 9,10 Since hyperoxic ventilation is capable to restore organ function in extreme anemia, 37 it is extremely unlikely that additional physically dissolved O 2 is merely shunted to the venous side of the circulation. Although we observed an increase of systemic vascular resistance and a reduction of cardiac output during hyperoxic ventilation, intestinal bood flow was not significantly reduced.…”

“…[8][9][10] On the other hand, hyperoxic ventilation has been shown to induce peripheral vasoconstriction, and thereby to alter microvascular blood flow and impair tissue oxygenation at normal Hct values. [11][12][13] Therefore, the question arises whether hyperoxic ventilation is actually beneficial in terms of improvement of intestinal oxygenation when initiated under the conditions of extreme hemodilution to Hct crit .…”

Haemoglobin, oxygen carriers and perioperative organ perfusion

“…It has been observed that haemoglobin solutions with different O 2 affinity caused different degrees of vasoconstrictions [61,62]. However, the hypothesis of autoregulatory vasoconstriction due to relative hyperoxic state caused by better O 2 unloading is in contradiction with multiples observation of better tissue PO 2 during hyperoxic ventilation [63][64][65][66][67][68].…”