A practical method of autotransfusion in the emergency center

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 - 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 mL/kg (approximately 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 (DO2) (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 DO2 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 observaton 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 DO2 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. In the present study, this method resulted in transient but significant hemodynamic changes in the pulmonary circulation. Impairment of oxygen transport was noticed after the end of hemorrhage, but this impairment cannot be attributed to the autotransfusion technique alone, but also to factors such as hemorrhagic shock, surgical trauma, etc.

Autotransfusion in the emergency patient

As the need for blood products increases in the veterinary emergency setting, the technique of autologous transfusion is being re-explored. Analogous transfusions provide an immediate source of blood with known compatibility to the patient. With the advent of passive canister collection systems, the technique is becoming simplified and affordable for the veterinary community. Although complications such as coagulopathies and microemboli have been reported with the procedure, attention to patient selection, technique, and patient monitoring following transfusion greatly minimizes potential drawbacks.

Emergency autotransfusion

Autotransfusion, a technique with more than 160 years of experience behind it, has become a subject of renewed interest in the emergency setting. The technique itself is not much more difficult than the tube thoracostomy or the peritoneal lavage that otherwise might be indicated in the multiple trauma victim and that would be required to start collection of autologous blood. The previously feared complications of hematologic or metabolic embarrassment and of sepsis have not proved to be of clinical significance when appropriate patient selection and careful technique are followed. In addition the use of autologous blood has a number of advantages over the transfusion of stored homologous blood in the emergency patient, including ready availability of compatible blood, homeostasis of core temperature, higher levels of red blood cell 2,3-DPG, and cost effectiveness. A review of the literature reveals that, while it is not totally free of complications, the benefits to be gained from autotransfusing the selected trauma patient outweigh the relatively limited risks of the procedure.

A new, simple method for intraoperative reinfusion

The disposable device for intraoperative reinfusion consists of a polycarbonate container with an antifoam-coated filter. One port is connected to the suction tip; the other port is attached to wall suction. Sodium citrate solution (50 to 100 ml) is aspirated first, followed by 400 ml of shed blood. The full container is passed to the anesthetist who turns the device upside down and starts reinfusion from the bottom, previously the top port of the container. In experiments with dogs, this procedure resulted in only slight hemolysis, a minor drop in platelet count, and no mortality or morbidity. This new method of reinfusion combines the advantages of simplicity, disposable equipment, and low blood trauma.

Experience in the management of 50 consecutive penetrating wounds of the heart

Fifty patients with penetrating wounds of the heart were grouped into three categories, based on the clinical severity of the injuries. Gunshot wounds consistently resulted in a higher mortality than knife wounds. Central venous pressure (CVP) was the single most important means of determining cardiac tamponade. The survival rates in the respective groups were 6, 79 and 100 per cent. The improved survival in our series was due to a rapid transportation system, increased awareness of the significance of cardiac injuries and an aggressive surgical approach.

Autotransfusion following cardiac operations: a randomized, prospective study

To evaluate the safety and effectiveness of the collection and retransfusion of postoperatively shed mediastinal blood as part of a multifaceted approach to blood conservation following cardiac operation, 113 patients were randomized into either an autotransfusion group (54 patients) or a control group (59 patients). Intraoperative and postoperative hemodilution was practiced in all patients. The clinical safety of this technique was confirmed by the lack of septic, hematological, pulmonary, renal, or hepatic complications. However, in this setting where blood conservation is already aggressively practiced, the ability of the technique to further reduce the use of banked blood following cardiac surgical procedures was not demonstrated.