Gross tissue appearances following hemorrhage, low-pressure stabilization, and resuscitation
McCarty, Bryan M.
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In a severe prolonged hemorrhage and resuscitation protocol, when do gross abnormalities become apparent? Hypothesis: Gross tissue abnormalities will be more obvious in those animals that survive longer. Methods: 8 anesthetized, ventilated dogs were hemorrhaged (H, 90min mean arterial pressure [MAP]=35-40mmHg or MAP<30mmHg>10min or MAP<25mmHg>1min), hypotensively stabilized (S, 120min enalaprilat 0.01mg/kg/hr + hemoglobin based oxygen carrier [HBOC] or 7.8% hypertonic saline dextran 70 [HSD] for MAP=40-45mmHg), resuscitated (60min lactated Ringer’s for MAP=75-80mmHg), monitored (60min no fluids), and euthanized. Every animal was necropsied, and the internal organs were examined for visible abnormalities. Results: There were 2 early non-survivors: 1 of 5 HBOC died 117min into S and 1 of 3 HSD died 9min into S. The rest survived to euthanasia (331min). No damage to the heart was visible in any animal. No lungs looked normal. On cross section, some of the renal cortices were much darker than normal, but this was not restricted to treatment group or non-survivors. Gastric, small and large intestinal mucosae were not normal in any animal, but the 2 early non-survivors were among those with the least abnormal intestines. Conclusions: Grossly visible changes in appearance occurred in most organs. Similar abnormalities in organ appearances (except possibly the intestines) in the 2 non-survivors versus survivors suggest that damage developed during hemorrhage rather than during resuscitation. This suggests that improvements in strategies for resuscitation from severe, prolonged hemorrhage should target repair of already damaged tissues in addition to prevention of additional tissue damage.