Haemodynamic and humoral responses to repeated hypotensive haemorrhage in conscious sheep

Abstract

Haemodynamic and humoral responses to two subsequent hypotensive haemorrhages, separated by 3 hours and each followed by retransfusion, were studied in unanaesthetized sheep. Haemorrhage was induced by removal of blood from a jugular vein at a rate of 0.7 ml kg-1 min-1 until the mean systemic arterial pressure suddenly decreased by 35 mmHg or more. In addition to the mean systemic arterial pressure, the cardiac output, the mean pulmonary arterial pressure, the central venous pressure and the pulmonary capillary wedge pressure decreased in response to each haemorrhage. The recovery of the systemic and pulmonary arterial pressure was slower and/or less efficient after the second haemorrhage, due to a less pronounced increase of the vascular resistance. Relative bradycardia, in association with the abrupt fall of the mean systemic arterial pressure, was more apparent during the first haemorrhage. The plasma levels of vasopressin, renin activity and angiotensin II were increased by each blood removal, but the vasopressin response to the second haemorrhage was significantly reduced. The plasma noradrenaline concentration was slightly and transiently elevated only in response to the second haemorrhage. The concentration of neuropeptide Y-like immunoreactivity in plasma was unaffected by both haemorrhages. It is suggested that the reduced and delayed increase in the systemic vascular resistance, accompanied by impaired recovery of the arterial pressure, and the relative absence of 'bleeding bradycardia', during the second haemorrhage, were due to the diminished vasopressin response.

Haemodynamic responses to hypotensive haemorrhage in conscious sheep with emphasis on renal and femoral blood flow

“…In these studies the cardiovascular responses exhibited the two characteristic stages outlined above. It was also found that the plasma vasopressin levels were not significantly increased until systemic hypotension occurred (Hjelmqvist et al 1991), which agrees with observations in rabbits (Quail, Woods & Korner, 1987 Surgical preparation was performed in two operative procedures, 3 weeks apart, and performed under general anaesthesia. The second operation was performed at least 2 weeks before the start of experiments.…”

“…This was apparently not the case, which is at variance with results observed after a moderate haemorrhage in humans where RBF was elevated above basal levels by retransfusion (Stone & Stahl, 1970). However, the last portions of the collected blood in the present study could be expected to contain substantial amounts of vasoactive agents, among them vasopressin (Hjelmqvist et al 1991). Provided these substances were not totally metabolized during the period of storage, they may have caused renal vasoconstriction, this is also supported by the slightly increased RVR immediately after retransfusion.…”

“…We have previously studied systemic haemodynamic and humoral responses to acute progressive hypotensive haemorrhage in conscious sheep (Jonasson, Hjelmqvist & Rundgren, 1989;Hjelmqvist, Ullman, Gunnarsson, Lundberg & Rundgren, 1991). In these studies the cardiovascular responses exhibited the two characteristic stages outlined above.…”

“…Post (Hjelmqvist et al 1991). These parameters, as well as MSAP and HR, were monitored via Gould pressure transducers (P23 ID, Gould Instruments, Hato Rey, Puerto Rico) and displayed on a Grass polygraph (Grass Instruments, Quincy, MA, USA).…”

Acid-base disturbance during hemorrhage in rats: significant role of strong inorganic ions

“…This latter may increase the activity of the anaerobic energyproducing systems or decrease aerobic energy-producing systems during hemorrhagic shock, thus raising lactic acid concentration of extracellular fluid and reducing plasma HCO 3 Ϫ concentration ([HCO 3 Ϫ ]) (17). However, hemorrhage also results in changes in the main plasma inorganic ions and proteins (6,10,16,18,(37)(38)(39)41).…”