Evaluation of the effects of autotransfusion of unprocessed blood on hemodynamics and oxygen transport in anesthetized pigs

Objective : To examine the hemodynamic effects and the oxygen transport pattern of autotransfusion of unprocessed blood on hemodynamics and oxygen transportation. Design : Prospective, observational study. Setting : Research laboratory of a university medical center. Subjects : Six healthy, domestic pigs (20 to 33 kg). Interventions : A left thoracotomy was performed and a 5-mm incision was created in the descending aorta, resulting in a controlled hemorrhage of 30 mUkg (-40% of blood volume) into the thoracic cavity over a 45-min time period. During that period, mean arterial pressure (MAP) was maintained slightly >50 mm Hg, using intravenous lactated Ringers' solution. The blood sample was collected from the open thorax with compresses soaked in citric acid solution and then extracted by manual squeezing, filtered through several layers of gauzes, and stored in glass bottles. Repeat measurements were performed after hemorrhage, after retransfusion of the harvested blood, and thereafter every 15 mins up to 60 mins. The animals were supported for 2 more hrs and were observed for the following 48 hrs. Measurements and Main Results : All animals survived and were in good condition 48 hrs after the experimental hemorrhage. The circulatory and oxygen transport response at the end of hemorrhage and concomitant maintenance of blood pressure at >50 mm Hg resulted in : significant reductions of cardiac index, MAP, and oxygen transport (Do 2 ) (46%, 50%, and 64% reductions, respectively, p <.01), in an increase of heart rate (HR) (+21%, not significant), pulmonary vascular resistance index (+112%, p <.05), and oxygen extraction (+105%, p <.01), as well as in a nonsignificant decrease of systemic vascular resistance index (-8%). After autotransfusion, the basic hemodynamic variables, MAP and HR were corrected, remaining near baseline (not significant) afterward. Cardiac index and Do 2 increased after autotransfusion, but remained below the baseline until the end of the study protocol (p <.05). A significant increase was noticed for pulmonary arterial pressure and pulmonary vascular resistance index immediately after autotransfusion (p <.01). These values were corrected in part after 15 to 30 mins, but remained higher throughout the observation period compared with baseline (29.5% and 89.8%, respectively, p < .05). The recently introduced relationship between cardiac index and oxygen extraction has been proposed to avoid problems of mathematical coupling between oxygen consumption and Do 2 measurements. This relationship followed a similar course in all experiments throughout each phase. A shift downward and to the right represented the endpoint of the hemorrhagic phase. After autotransfusion, a shift toward baseline was noticed. Prothrombin time and partial thromboplastin time remained unchanged after autotransfusion. Free hemoglobin concentrations increased immediately after autotransfusion (+33%, p <.05), but returned to baseline values 48 hrs later. Histologic examination showed no changes in the examined organs. Conclusions : Reinfusion of large amounts of unprocessed blood (up to 40% of blood volume), collected with compresses from a noncontaminated surgical field is a cheap method, which may be of potential benefit in trauma patients, when more sophisticated autotransfusion devices are lacking