TRAUMA-HEMORRHAGE AND RESUSCITATION IN THE MOUSE - EFFECTS ON CARDIAC-OUTPUT AND ORGAN BLOOD-FLOW

Although mice are widely used for the study of immune consequences of hemorrhage, the changes of cardiac output (CO) and blood flow (BF) in response to trauma and hemorrhage in this species have not been well d efined. To study this, nonheparinized C3H/HeN mice (n = 6 per group) u nderwent laparotomy (i.e., trauma induced), were bled to a mean arteri al pressure of 35 mmHg, and maintained for 90 min by withdrawing more blood or returning Ringer lactate. The animals were then resuscitated with four times the volume of maximal bleedout in the form of Ringer l actate over 60 min. Sham-operated mice underwent the same procedure bu t were neither bled nor resuscitated. At the end of hemorrhage, 60 min postresuscitation, or corresponding time after sham operation, CO and BF were determined by radioactive microspheres. Results indicate that CO and BF decreased significantly at the end of hemorrhage. Resuscita tion, however, restored CO and BF in various organs except the brain a nd skeletal muscle. Despite this, 9 of 16 mice died within 6 days post resuscitation, whereas none of sham mice died (n = 16 per group in thi s additional study). Therefore, we have developed a nonheparinized mod el of trauma-hemorrhage and resuscitation in mice that is associated w ith late mortality. Furthermore, the microsphere technique provides a reliable method for assessing CO and BF in mice. Thus it may be possib le to study the correlation between cardiovascular and immunologic alt erations under such conditions.