Prolonged severe hemorrhagic shock at a mean arterial pressure of 40 mmHg does not lead to brain damage in rats

Abstract

AimTo examine whether prolonged hemorrhagic shock (HS) at a mean arterial pressure (MAP) of 40 mmHg leads to brain damage.MethodsRats were anesthetized with sevoflurane. The HS model consisted of the following phases: I, pressure‐controlled HS at a MAP of 40 mmHg; II, fluid resuscitation to normalize blood pressure; III, observations with outcome evaluations in terms of survival, overall performance categories, and neurological deficit scores, as well as evaluation of apoptosis in the hippocampus at 96 h. Each group of six rats was randomized into 60 min (group 1) or 75 min (group 2) each of phases I and II. Three sham rats were anesthetized for 150 min, and then awakened during phase III.ResultsThe three sham rats as well as five and two of the six rats in groups 1 and 2 (P < 0.05), respectively, survived for up to 96 h. All survivors were functionally normal with overall performance category = 1 and neurological deficit score = 0 at 96 h. Apoptotic neurons were not found in the hippocampus.ConclusionsThe higher mortality in group 2 suggested a more profound effect of HS compared with group 1. However, prolonged HS for 60 or 75 min did not cause functional damage or apoptosis in the hippocampus. These findings suggest that prolonged HS at a MAP of 40 mmHg, as a level at which cerebral blood flow seems preserved by autoregulatory mechanisms, does not lead to brain damage.

Moderately prolonged permissive hypotension results in reversible metabolic perturbation evaluated by intracerebral microdialysis - an experimental animal study

“…During the period of hemorrhagic shock, MAP decreased to a median value of 39 mmHg (35-42). Accordingly, CPP decreased to low levels of 33 mmHg (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39). Similarly, the brain tissue oxygen tension decreased to near critical levels of 19 mmHg (8-23).…”

“…These findings are also supported in two studies investigating the effect of prolonged and severe hemorrhagic hypotension in rats. The authors found that MAP 40 mmHg for 60-75 min did not cause cognitive damage to the rat, nor was it possible to detect apoptotic areas in the hippocampal area of the brain [28,29]. However, the abovementioned studies only examined the microcirculatory flow and not the presence of oxygen and nutrients in the interstitial space.…”

Higher Concentration of Hypertonic Saline Shows Better Recovery Effects on Rabbits with Uncontrolled Hemorrhagic Shock

“…Restrictive hypotensive fluid resuscitation aims to provide necessary doses of fluid to ensure the basic blood supply to vital organs, maintaining mean arterial pressure (MAP) in a lower range. Mihara et al showed that limiting fluid resuscitation is a relatively safe way to keeping MAP at low levels [9]. Controlling MAP at 50–60 mmHg during UHS effectively reduces blood loss and prolongs survival time [10,11].…”