Central angiotensinergic system and hypertonic resuscitation from severe hemorrhage.

Single injections of 4 ml/kg hypertonic NaCl (7.5%) resuscitate dogs from severe blood loss (40-45 ml/kg). Mechanisms involve osmolarity-dependent volume expansion, increased myocardial contractility, and vasodilation. The role of central angiotensinergic pathways in the hemorrhage-hypertonic resuscitation interaction was investigated through experiments performed on male pentobarbital sodium-anesthetized dogs bled to, and held at, 40 mmHg for 30 min. Dogs were treated with 4 ml/kg of 7.5% NaCl or 32 of 0.9% NaCl iv preceded by intracerebroventricular (ICV) injections of 150 micrograms saralasin, 20 micrograms arginine vasopressin inhibitor (AVPI), or 10 micrograms morphine. ICV saralasin and morphine inhibited the full recovery response to hypertonic NaCl, whereas AVPI had no such effect. Saralasin did not inhibit the recovery from hemorrhagic shock produced by large volume isotonic saline reexpansion. These data demonstrate an interaction between the central angiotensin system and small volume hypertonic resuscitation from severe hemorrhagic shock but not between this central system and large volume isotonic reexpansion of circulatory volume. In contrast, the central vasopressinergic system does not appear to be similarly involved.