Michael Horowitz, Benjamin Bobo, Hieu Le, and Brandon Repko
Background: Blood loss relating to surgical procedures is difficult to predict. Inadvertent vascular injury or insidious loss over time can lead to post-surgical anemia and, in some instances, vascular collapse, cardiac arrest, and death. Replacement of lost blood can be achieved using allogenic donor sources (banked blood) or through preplanned collection and reinfusion of extracorporeal autologous blood collected by means of Cell Saver technologies or pre-surgical autologous donation. Unfortunately, these methodologies require anticipation of blood loss and proactive decisions made prior to the undertaking of a procedure. In addition to necessitating preplanning, donor blood products and Cell Saver technology are expensive, labor intensive, and are often limited by unavailable resources. Packed cell reinfusion also fails to address the need for coagulation factors and proteins while at the same time often increasing the patient’s acidotic state. The latter can worsen a patient’s shock related metabolic lactic acidosis, making physiologic resuscitation even more difficult. These issues, while ubiquitous in the civilian hospital setting are magnified in the setting of Combat Casualty Care (CCC) where field hospital resuscitation is hampered by a paucity of technology and transfusable blood products. Aside from the mortality or major morbidity resulting from unexpected blood loss, post procedure anemia, a condition that frequently affects post-surgical patients, has negative effects on recovery especially in individuals over the age of 65.
Methods: A proof of concept study was conducted to test a novel disposable three stage filtration device to determine: (1) If gravity fed passage of clotted bovine blood through the filter system would exclude thrombus and other particulate such that the filtered product was free of particulate matter, (2) If gravity fed passage of non-clotted porcine and human blood through the system caused red blood cell damage that could preclude safely returning the filtered blood to the donor animal as an autologous transfusion and (3) If gravity filtration altered the coagulation profile of filtered human blood when compared to unfiltered blood. For the porcine portion of the study, unfiltered (control) and filtered (experimental) blood from the same animal was tested for serum (Ca), serum (K), and Hematocrit (Hct), and was also examined micro-histologically to determine if cell morphology was altered by the filtration process. Elevations in ion concentrations in the post filtered sample was felt to be a reliable measure of potential filtration induced hemolysis as was microscopic evaluation of blood smears. For the human portion of the study unfiltered and filtered blood was studied for coagulation anomalies using PT, PTT and INR. RBC integrity was evaluated by measuring LDH, ALT, AST, total bilirubin, K, and Hct. Platelets count and RBC /platelet integrity on blood smear was also performed.
Results: (1) Results after the filtering of thrombosed bovine blood showed no residual thrombus in the final filtrate, (2) When the unfiltered (control) and filtered (experimental) porcine blood samples were compared, no differences in extracellular (Ca) or (K) were detected. Hct remained consistent between the two samples and micro-histologic analysis showed no evidence of red blood cell damage, (3) When unfiltered and filtered human blood was evaluated no differences in coagulation or other hematologic parameters were identified, (4) When unfiltered and filtered human blood was compared, all chemical markers for hemolysis aside from a single LDH level remained normal thus supporting the high likelihood of absent filter induced hemolysis.
Conclusion: Using a novel gravity fed filtration system, processing of a solution containing bovine thrombus and saline showed no residual thrombus in the final filtrate. Extracorporeal processing of extracted porcine and human blood using the same device showed no evidence of red blood cell injury or alteration of coagulation profile when unfiltered and filtered blood samples were compared. While further investigations are needed to determine short and long-term safety of infusion of autologous blood treated in this manner, this proof-of-concept study provides encouraging data that will guide further development of an inexpensive, mobile, disposable and technologically simple device that can be used in every surgical procedure (civilian and military) to recycle any volume of blood loss. Such technology will hopefully reduce health care expense by making autologous blood recycling cost-effective in developed and undeveloped nations.
Adoption of routine filtration and reinfusion may also reduce the incidence of post-surgical anemia, reduce the need for allogenic donor blood, reduce reliance on costly Cell Saver technologies and provide a level of safety that does not currently accompany every invasive procedure that carries the risk of blood loss. Applications in military and disaster settings will provide a degree of care that has long been reserved for established brick and mortar settings. It is our hope that simple recycling of procedural blood loss will establish a new standard of care that no longer considers nonrecycled blood loss a normal consequence of invasive procedures.
Trial Registration: This article does not report intervention results on human participants. Animal use was approved by the State University of New York at Buffalo, Canon Stroke and Vascular Research Center IRB # NSG07123N. Human blood was personally provided by the author (MH) and routine laboratory testing was performed.