P. Waltz1, J. Luclano1, S. Shiva1, B. Zuckerbraun1,2 1University Of Pittsburg,Pittsburgh, PA, USA 2VA Pittsburgh Healthcare System,Pittsburgh, PA, USA
Introduction: Currently, there is no effective resuscitative adjunct to fluid and blood products to limit tissue injury for traumatic hemorrhagic shock. The objective of this study was to investigate the role of inhaled carbon monoxide (CO) to limit inflammation and tissue injury, and specifically mitochondrial damage, in experimental models of hemorrhage and resuscitation.
Methods: Mice underwent hemorrhagic shock and resuscitation to a mean arterial pressure (MAP) of 20 or 25 mmHg. Mice were resuscitated with Lactated Ringers (2:1 volume of maximal shed blood ) after 90 or 120 minutes of hypotension. Pigs (30-35 kg) were anesthetized and bled to a MAP of 30-40 mmHg for 90 minutes, followed by initial resuscitation with Hextend (1:1 volume of shed blood). Pigs had ongoing resuscitation and support for up to four hours. Data were collected continuously. Primary mouse hepatocytes were used for in vitro studies and murine skeletal muscle was used for ex vivo studies. ANOVA was used for statistical analysis and significance was assumed with a P<0.05.
Results:Inhaled CO (250 ppm for 30 minutes) protected against mortality in severe murine hemorrhagic shock and resuscitation (HS/R) (20% vs. 80%; P<0.01). Additionally, CO limited the development of shock as determined by arterial blood pH (7.25±0.06 vs. 7.05±0.05; P<0.05), lactate levels (7.2±5.1 vs 13.3±6.0; P<0.05), and base deficit (13±3.0 vs 24±3.1; P<0.05). A dose response of CO (25-500 ppm) demonstrated protection against HS/R lung and liver injury as determined by MPO activity and serum ALT, respectively. CO limited HS/R-induced increases in serum tumor necrosis factor-α and interleukin-6 levels as determined by ELISA (P<0.05 for doses of 100-500ppm). Furthermore, inhaled CO limited HS/R induced oxidative stress as determined by hepatic oxidized glutathione:reduced glutathione levels and lipid peroxidation. In porcine HS/R, CO did not influence hemodynamics. However, CO limited HS/R-induced skeletal muscle and platelet mitochondrial injury as determined by respiratory control ratio (muscle) and ATP-linked respiration and mitochondrial reserve capacity (platelets). Furthermore, in vitro and ex vivo, CO limited oxygen consumption to increase oxygen levels under hypoxic conditions, and also limited loss of mtiochondrial membrane potential, oxidative stress, and loss of ATP.
Conclusion: CO therapy limits injury to the metabolic machinery of cells in the setting of HS/R in multiple animal models. These preclinical studies suggest that inhaled CO can be a protective therapy in HS/R, however, further clinical studies are warranted.