Effect of Therapeutic Hypercapnia on Systemic Inflammatory Responses in Hemorrhagic Shock in Rats

ABSTRACT

PURPOSE: This study was performed to investigate whether therapeutic hypercapnia could attenuate systemic inflammatory responses in hemorrhagic shock in rats. METHODS: Male Sprague-Dawley rats were mechanically ventilated and underwent pressure-controlled (mean arterial pressure 38+/-1 mmHg) hemorrhagic shock. At 10 minutes after the induction of hemorrhagic shock, the rats were divided into the normocapnia (PaCO2=35-45 mmHg, n=10) and the hypercapnia (PaCO2=60-70 mmHg) groups. The PaCO2 concentration was adjusted by using the concentration of inhaled CO2 gas. After 90 minutes of hemorrhagic shock, rats were resuscitated with shed blood for 10 minutes and were observed for 2 hours. The mean arterial pressure (MAP) and the heart rate were monitored continuously, and the results of arterial blood gas analyses, as well as the plasma concentrations of interleukin (IL)-6, IL-10, and nitrite/nitrate were compared between the normocapnia and the hypercapnia groups. RESULTS: The MAP and the heart rate were not different between the two groups. The plasma concentration of IL-6 was significantly lower in the hypercapnia group than in the normocapnia group (p<0.05). The IL-10 concentration was not different and the IL-6 to IL-10 ratio was significantly lower in the hypercapnia group compared to the normocapnia group. The plasma nitrite/nitrate concentration of the hypercapnia group was lower than that of the normocapnia group. CONCLUSION: Therapeutic hypercapnia attenuates systemic inflammatory responses in hemorrhagic shock.