Chapter 170 Blood Loss Management
Preoperative Evaluation
Medication History
Patients with a history of transient ischemic attack, stroke, deep venous thrombosis (DVT), heavy bleeding after minor trauma, alcoholism, hepatic dysfunction, neuromuscular scoliosis, cerebral palsy,1 and cardiac disease have an increased risk of bleeding. Many patients who undergo spinal surgery take nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibit platelet function and may increase bleeding times. The bleeding time often returns to normal within 24 hours of cessation of some NSAIDs, whereas others require a full 18 days for the drug to be eliminated and normal platelet function restored. Antiplatelet drugs, such as ticlopidine hydrochloride (Ticlid), clopidogrel (Plavix), dipyridamole (Persantine), and aspirin may prolong the bleeding time and must be discontinued before surgery.2 Patients who take warfarin (Coumadin) may require cessation or reversal of the anticoagulation (Table 170-1). Those rare patients with congenital coagulation deficits may undergo surgery after factor replacement and consultation with a hematologist.3
Patients treated with the anticonvulsant valproic acid (Depakote) appear to have increased blood loss during spinal surgery. This is thought to be related to an inhibition of platelet function. If possible, another antiepileptic drug should be used in the immediate preoperative and postoperative periods for such patients.4
Preoperative Estimation of Blood Loss
Factors associated with increased blood loss with spinal surgery include tumor, low preoperative hemoglobin level, numbers of levels fused, history of pulmonary disease, suboptimal autologous blood availability, the use of operating tables other than dedicated spine surgery tables, and antiplatelet drugs.5–7 When surgery is contemplated for reconstruction in cases of spinal metastasis from renal cell carcinoma, preoperative embolization has been shown to significantly reduce intraoperative blood loss. Therefore, embolization should at least be considered as a preoperative adjunct in all vascular spinal tumors.8
The blood loss for a particular operation should be estimated and plans generated to ensure that such can be replaced if needed. An estimate of 200 mL of blood lost per fused segment can be made before surgery to plan the amount of blood that will be required for replacement.8 Patients can usually tolerate a loss of 15% of the blood volume before transfusion.9 In a 70-kg patient, estimating 70 mL blood/kg body weight, a volume of 735 mL would reflect a 15% blood loss.
Autologous Blood Use
Autologous blood donation can be instituted if the estimated blood loss exceeds 15% of the blood volume. Autologous blood can be obtained in three ways: preoperative donation, intraoperative salvage, and postoperative salvage. Although each requires expensive specialized equipment, a reduction in the potential for the development of chronic liver disease and infection transmission may be well worth the cost.10 One unit of blood can be donated per week if the hematocrit remains above 34%.11 Other guidelines for autologous donation include a patient age range of 12 to 70 years11 and a hemoglobin of at least 11 mg/dL.12 Full units can be taken from patients weighing more than 50 kg and half units from those between 25 and 50 kg. Supplemental iron should be administered when appropriate. In some instances, recombinant erythropoietin can be administered to facilitate increased blood volume for autologous donation.13–16 This has been shown to increase blood production significantly both in animal and clinical studies.13,17
Consideration should be given as to whether autologous packed red blood cells or whole blood should be transfused. The patient donates whole blood, and in autologous donation it may be best to return whole blood to the patient. Whole blood contains platelets, plasma, and cryoprecipitate, all of which are lacking in packed cells, and these components may help lessen bleeding.13 Using autologous blood in a community hospital, 95% of the transfusion needs were met for 1600 patients who underwent major orthopaedic procedures.18 Other studies have shown that autologous blood can supply approximately 70% to 80% of the transfusion needs.10,12 Autologous blood may be cryopreserved or preserved with a storage solution.19 Cryopreserved blood has a longer shelf life, and the in vitro survival of red blood cells is equivalent to that of fresh erythrocytes. Also, no preoperative effect on the hemodynamic status of the patient exists.20 Oga et al.19 used cryopreserved cells in patients who underwent scoliosis surgery and solution-stored blood for patients who underwent other spine procedures. More blood was collected for the scoliosis patients, and the less costly storage method was used for other patients.19 There are risks to autologous blood transfusion, which include septicemia from bacterial contamination of the unit, nonimmune hemolytic transfusion reactions, febrile reactions, volume overload, and the possible risk of clerical error resulting in the administration of the wrong unit of blood.21
The criteria for returning autologous blood may vary. Albert et al.22 found that the transfusion of blood during surgery was beneficial for the early postoperative hemoglobin and postoperative patient mobilization. There are different indications for homologous versus autologous blood return. Hemoglobin of less than 7 g/dL for homologous transfusions and less than 10 g/dL for autologous transfusions is a common indicator.12,22
Indications for transfusion of homologous blood include a hemoglobin of less than 7 g/dL in a medically healthy but symptomatic patient, a hemoglobin of less than 10 mg/dL in a critically ill patient, and a patient with medical risk factors such as cardiovascular disease, cerebrovascular disease, or active hemorrhage. Symptoms indicating hypovolemia, such as tachycardia, tachypnea, or low venous oxygenation, also indicate the need for transfusion.12,22,23 Other transfusion requirements have been published. They include hemoglobin less than 8 g/dL in an otherwise healthy patient, hemoglobin less than 11 g/dL in patients with increased risk of ischemia, acute blood loss with 15% of blood volume lost, diastolic pressure less than 60 mm Hg, systolic blood pressure decrease of greater than 30 mm Hg, tachycardia, oliguria, symptomatic anemia with tachycardia, mental status changes, cardiac ischemia, and dyspnea. General transfusion requirements for coagulation products have been provided. Platelet transfusion for platelet dysfunction or thrombocytopenia is an effective strategy in such cases. Fresh-frozen plasma may be administered for evidence of coagulation factor deficiencies with prothrombin time or activated partial thromboplastin time greater than 1.5 times the upper limit of normal. Cryoprecipitate is administered for suspected specific factor deficiencies or fibrinogen less than 100 mg/dL.5
Homologous Blood Use
Since the early 1980s, there has been an increasing concern about the risks of blood transfusions. Although transmission of HIV has been the primary concern, allergic reactions, isosensitization, and the transmission of hepatitis are far more serious in terms of the number of patients affected. Hepatitis following transfusion has been reported to occur in as many as 10% of patients after homologous transfusion, with 3.3% developing chronic liver disease.10
The risks of allogeneic blood transfusion have decreased over the past several decades. Currently, transfusion-related acute lung injury (TRALI), hemolytic transfusion reactions (HTRs), and transfusion-associated sepsis are the leading causes of allogeneic blood transfusion–related fatalities. TRALI appears clinically similar to acute respiratory distress syndrome, but in TRALI the infiltrates typically clear in 96 hours, and the case fatality rate is only 5%. Fresh-frozen plasma is the most frequently implicated transfused component. White blood cell antibodies in the transfused component appear to be the most frequent trigger for TRALI. HTR occurred at a rate of 1 per 76,000 units transfused with a case fatality rate of 2% in a recent 10-year New York state study. These cases of HTR are largely attributable to clerical error or undetected non-ABO antibodies.24 Since the introduction of tests in 1990 for the detection of hepatitis C, the incidence of transfusion-acquired hepatitis has significantly decreased. The predominant risk is from donors in the “window period” of their infection who have donated blood before they have developed antibodies to the virus, rendering it impossible to detect the infection.
The current risk of hepatitis C transmission is 1 in one million units transfused, and the current risk of hepatitis B transmission is 1 in 100,000 units transfused. The current risk of HIV transmission in tested blood varies with the region of the United States, but is approximately 1 in one million units transfused.24 This estimate of risk assumes a safe, plentiful, well-regulated, and tested blood supply; unfortunately, this is not universally the case in developing countries.25
Anesthetic Techniques for Lessening Intraoperative Blood Loss
Randomized, controlled trials have shown no difference in the amount of blood loss in patients who received desmopressin compared with those who did not.26 Other studies have shown desmopressin to reduce blood loss in spine surgery by 32.5%.23 It is administered immediately before surgery at a dose of 10 μg/m2 of body surface area, up to a maximum dose of 20 μg. It is prepared by diluting it to a concentration of 0.5 μg/mL in normal saline and infusing over 20 minutes. Desmopressin does lessen bleeding in some subsets of patients, such as those with acquired platelet dysfunction from aspirin administration, von Willebrand disease, and uremia.5,27 Desmopressin has been found to decrease the partial thromboplastin time, whereas factor VIII coagulant activity and von Willebrand antigen concentrations increased the partial thromboplastin time. A Cochrane review found no convincing evidence that desmopressin minimizes perioperative allogeneic red blood cell transfusion in patients who do not have congenital bleeding disorders.28 Potential postoperative problems include oliguria, which usually responds to furosemide, and hyponatremia due to its potent antidiuretic hormone activity.29
Randomized, controlled trials of aprotinin (Trasylol) in dorsal spinal fusion reveal significant reductions in autologous but not homologous blood transfusion. Aprotinin has been shown to reduce blood transfusion requirements in cardiac surgery, liver resection, and some orthopaedic surgical procedures.30 Aprotinin has been found to increase mortality in cardiac surgery patients and was relabeled by the U.S. Food and Drug Administration (FDA) for use only in high-risk cardiac patients. It was removed from the U.S. market in November 2007.31
ε-Aminocaproic acid (Amicar) is an antifibrinolytic agent that has been shown to reduce blood loss in cardiac surgery.32 It has been tested in lumbar spinal fusion and has been shown to reduce autologous blood transfusion in a prospective, nonrandomized study by approximately 50%. No complications were noted, including thromboembolism or DVT. ε-Aminocaproic acid was given in an initial dose of 100 mg/kg, not to exceed 5 g over 15 minutes, followed by a continuous infusion of 10 mg/kg/hr over the remainder of the case, with the infusion terminating at skin closure.33
Tranexamic acid is a synthetic antifibrinolytic agent that has been studied as a means to reduce blood requirements in scoliosis surgery. In a double-blinded, prospective, placebo-controlled study, tranexamic acid, given in an initial dose of 10 mg/kg at the time of patient positioning and in a maintenance infusion of 1 mg/kg/hr, reduced blood transfusion requirements by 28%.34 A recent study of tranexamic acid using a loading dose of 2 g, followed by a continuous infusion of 100 mg/hr in adults and 1 mg/kg/hr in children, resulted in a 49% reduction of blood loss.35 Because tranexamic acid is an antifibrinolytic agent, it does not change the blood’s intrinsic clotting ability but rather slows the breakdown of preexisting clots. Tranexamic acid has also been studied for use in reducing blood loss in metastatic spine tumor surgery and unfortunately did not significantly reduce blood loss in a retrospective study.36
Recombinant coagulation factor VIIa has shown promise in reducing blood loss in spinal surgery. Factor VIIa has been used in trauma management, craniotomy, and to reverse the effects of warfarin. Factor VIIa is approved by the FDA for use in patients with hemophilia with inhibitors to replacement factor VIII or IX. Use for hemostasis in other conditions is considered off-label at this time. The drug has a short half-life and is given as hourly bolus doses or by continuous infusion. Until more data are available, the drug should be used only as an agent of last resort in the event of bleeding when all other measures have failed. The drug is available in 1200-μg vials, and doses have been given in a wide range, from 16 μg/kg to 212 μg/kg, with no reported incidence of untoward events.17,24,25,29,37,38 One multicenter, randomized, controlled trial of factor VIIa used in spine surgery demonstrated no adverse events and significantly reduced blood loss.39
Acute hemodilutional autotransfusion is another technique used to reduce the need for homologous blood transfusion. After the induction of anesthesia, a venesection is performed and 15% to 25% of the patient’s blood volume is withdrawn into a sterile bag containing the anticoagulant citrate. The blood volume withdrawn is then replaced with colloid, on a milliliter-for-milliliter basis, or crystalloid, on a three-to-one basis. At the conclusion of surgery, the autologous blood is returned to the patient. The patient is then diuresed of excess fluid.35,40 Patients with type O blood have lower concentrations of factor VIII and von Willebrand factor than patients with other blood types. Type O patients are at increased risk for development of disseminated intravascular coagulation (DIC) when blood is replaced with the colloid 6% hydroxyethyl starch.41
