Blood volume restitution after hemorrhage in adult sheep

Abstract

Indirect experimental evidence suggested the possibility that the restoration of blood volume to normal hemorrhage in adult sheep may occur more quickly than in other species that have been studied. To test this hypothesis, we studied unanesthetized chronically catheterized adult female sheep 1-2 wk after splenectomy. An average of 19.6 +/- 1.4% (SE) of their initial blood volume was removed over 10 min. Blood volume restitution at 0.5, 1, 3, 5, 7, 24, and 48 h posthemorrhage averaged 12 +/- 3, 34 +/- 3, 41 +/- 3, 50 +/- 4, 62 +/- 10, 79 +/- 10, and 124 +/- 25%, respectively. Arterial pressure decreased during the hemorrhage and returned to normal within 2 h, whereas venous pressure did not change significantly. No change in blood osmolality occurred. There was a highly significant correlation between blood volume and plasma protein mass (r = 0.98, P less than 10(-6)) during and after the hemorrhage. Thus it appears that the posthemorrhage restoration of blood volume in adult sheep occurs over essentially the same time course as in other species and this appears to be mediated by a restoration of plasma protein mass.

Haemodynamic and humoral responses to repeated hypotensive haemorrhage in conscious sheep

“…Apparently, the fluid transfer was not facilitated by concomitant hyperglycaemia, as has been suggested from studies in anaesthetized dogs (Knott et al 1969) and cats (Jarhult 1973), since the plasma osmolality remained unchanged during the experiments. This is in accordance with the observations in the same species by Grimes et al (1987), who also found that during the first h following a rapid haemorrhage of 19% of the blood volume, about one third of the removed volume was spontaneously recovered, partly via a recovery of the total plasma protein mass. With regard to this, and the fact that sheep can release substantial amounts of erythrocytes from the spleen (Torrington et al 1989), it is impossible to calculate fluid shifts from changes in plasma protein concentration and haematocrit.…”

Modeling time variant distributions of cellular lifespans: increases in circulating reticulocyte lifespans following double phlebotomies in sheep

“…By the external removal or addition of cells to the sampling space, the volume of the sampling space can be estimated under the assumption that the total sampling space volume remains constant. Following an acute phlebotomy (i.e., removal of blood cells) the original blood volume is re-established within 24-48 h if no plasma volume expanders are administered [7,25], therefore the assumption of a constant blood volume (i.e., the sampling space) is reasonable when dealing with populations of blood cells and the 24-48 h lag-time for re-establishment of the blood volume is considered. The original blood volume will be reestablished even more rapidly if plasma or other blood volume expander is administered, due to increased osmotic pressure in the vascular system.…”

“…The time invariant "point distribution" cellular lifespan model, is obtained by replacing in Eq. 19 the time variant Weibull distribution with a time invariant dirac delta function, δ (ω − a), which upon simplification gives: (25) where:…”

Sustained stimulation of vasopressin and oxytocin release by ATP and phenylephrine requires recruitment of desensitization-resistant P2X purinergic receptors

“…Information about decreases in blood pressure and/or volume is transmitted to the magnocellular VP and OT neurons in the paraventricular (PVN) and supraoptic nuclei (SON) via the A1 catecholamine pathway, which utilizes ATP and norepinephrine as neurotransmitters (6). Postural changes induce acute elevations in plasma VP (21), while prolonged decreases in blood pressure and/or volume can elicit increases in plasma VP/OT that are sustained for hours to days (3,15,29). The absence of these sustained elevations in plasma VP leads to cardiovascular collapse in hemorrhagic and septic shock (24,27,30).…”