The opportunity to limit blood loss in the OR can begin months before an elective spinal procedure through appropriate patient screening and optimization. This starts with a detailed history and physical exam, assessing for signs and symptoms of anemia, including fatigue, weakness, dizziness, pallor, and shortness of breath. A complete blood count should be ordered for every patient, as much as 4 weeks prior to surgery to allow for potential medical treatment of anemia.¹⁵ As defined by the WHO, anemia is a hemoglobin concentration <11.0-13.0 g/dL, with thresholds stratified by gender and age.¹⁶ Rates of preoperative anemia in the orthopedic literature vary due to inconsistent definition of anemia and can range from 11% to 35%.⁵,⁶,¹⁵,¹⁷ Lasocki et al.⁵ found that anemic adult patients undergoing elective orthopedic surgery in Europe were more likely to undergo intraoperative transfusion and had significantly higher rates of postoperative complications. In spine patients, low preoperative hemoglobin can significantly increase the risk for perioperative allogenic transfusion.⁸,¹⁸,¹⁹

There are several options for treating preoperative anemia, increasing red blood cell mass, and diminishing the risk of acute intraoperative blood loss anemia and the need for allogenic transfusion. In a population of adolescent idiopathic scoliosis (AIS) patients, van Popta et al.¹⁸ recommended an ideal hemoglobin value of 5.0 g/dL higher than the surgeon’s transfusion threshold, as patients had an average decrease in hemoglobin value of 4.1 g/dL after posterior instrumented spinal fusion. Neuromuscular patients without adequate oral intake may be, at baseline, dehydrated and therefore have artificially elevated hemoglobin concentration; upon induction, vasodilation, and hydration in the OR, these patients become seemingly anemic.

Effective treatment of anemia requires determination of its etiology via further laboratory testing and evaluation to rule out any blood loss due to serious illness or neoplastic process.¹² Iron deficiency as determined by ferritin levels is a common cause of anemia and can be treated by 4 weeks of oral iron supplementation¹²,²⁰ or a single dose of intravenous iron administered 2-3 weeks prior to surgery.¹⁵ Adjunctive erythropoietin (EPO) can also be used to directly stimulate red blood cell differentiation from progenitor cells in the bone marrow. Colomina et al.²¹ found that administration of 40 000 IU of EPO weekly for 3 weeks to adult spine patients resulted in higher hemoglobin concentration and decreased allogenic
blood transfusion. In pediatric spine patients, preoperative administration of EPO was shown to increase hemoglobin concentration, decrease the need for allogenic blood transfusion, and decrease hospital stay in idiopathic scoliosis patients.²²,²³ However, using EPO routinely in healthy patients is not indicated due to its high cost but could be discussed in certain situations where transfusion is likely or conscientiously objected. In addition to iron deficiency, anemic patients may also be deficient in vitamin B12 and folic acid leading to macrocytic anemia, requiring supplementation.¹⁵,²⁰ Patients of Mediterranean origin may have thalassemia and should be screened for anemia.

In addition to anemia, special attention must also be paid to identification of any blood dyscrasias or history of bleeding disorders. To identify previously undiagnosed coagulopathies, prothrombin time (PT), activated partial thromboplastin time (aPPT), and international normalized ratio (INR) should be ordered. In children, Bhasin et al.²⁴ found that a simple screen of personal or family history of a bleeding disorder identified 60% of those patients with a significant coagulation abnormality determined by routine preoperative lab testing. Routine screening of blood dyscrasias may not be necessary in healthy patients but is variable among anesthesia departments. Any patient with coagulopathy, such as von Willebrand disease, or abnormal lab values should be referred to a hematologist to assess for possible preoperative treatment and perioperative management strategies.

Increased bleeding is also associated with several classes of medications, and while many surgeons engage primary care providers to help optimize surgical patients, it is important to be familiar with these medications to provide adequate counseling. Patients living with cardiovascular or cerebrovascular disease are often treated with anticoagulants or antiplatelet agents, which increase the risk of bleeding during spine surgery. Clear communication is essential when considering surgery for patients requiring long-term anticoagulation with medications such as warfarin, rivaroxaban and apixaban, as holding them results in subtherapeutic treatment with increased risk of thromboembolism. For patients on warfarin, recommendations are to hold medication 4-6 days prior to surgery and restarting therapy immediately after surgery, which results in 8-10 days of subtherapeutic anticoagulation.²⁵ This calculated risk of thromboembolism must be weighed against the benefit of spine surgery for each patient, and shared decision-making regarding timing and the need for postoperative bridging therapy must include discussion with the patient’s primary care provider, cardiologist, and previous surgeons.⁹

Antiplatelet agents like aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and clopidogrel raise bleeding risk by impairing platelet function and thrombus formation. Aspirin impairs platelet aggregation by irreversibly binding both cyclooxygenase enzymes (COX-1 and COX-2), leading to decreased thromboxane A2 production and impaired platelet aggregation. In a prospective, randomized trial of 10 000 patients undergoing noncardiac surgery, perioperative use of low-dose aspirin was found to significantly increase the risk of major bleeding, without any increase in mortality or myocardial infarction in patients taking a placebo.²⁶ Similarly, meta-analysis by Burger et al.²⁷ demonstrated that cessation of aspirin prior to invasive procedures in 500 patients on chronic aspirin therapy increased bleeding complications by a factor of 1.5. The authors also noted that stopping aspirin was not without its own risks and was the preceding event in 10.2% of
patients who developed acute myocardial infarction, stroke, or peripheral arterial occlusion.²⁷ While continuation of low-dose aspirin has not been well studied in spine surgery, a recent survey of 145 spine surgeons found that 66% believed low-dose aspirin placed patients at increased risk of perioperative hemorrhage, and consensus was that patients should stop aspirin 7 days prior to spine surgery.²⁸ Conversely, nonselective NSAIDs, like ibuprofen and naproxen, reversibly inhibit COX-1 and COX-2, resulting in quicker return of normal platelet function after discontinuation. While NSAIDs vary in length of half-lives and duration of action, cessation of NSAIDs 3 days prior to surgery is sufficient for most NSAIDs with the exception of piroxicam, which requires 7 days.⁹

Platelet blocker clopidogrel has also been shown to increase the risk in noncardiac surgery, with up to 50% increase in surgical bleeding and transfusion rate.²⁹ Clopidogrel is commonly prescribed for complex patients with a history of stroke or acute coronary syndrome requiring stenting. To avoid stent thrombosis, cardiologists recommend up to 12 months of continuous antiplatelet therapy following placement of drug-eluting stents, which can be justification to delay elective spine surgery until antiplatelets can be safely discontinued.⁹ Clopidogrel should be stopped 7 days prior to surgery for full return of platelet function in patients where appropriate consultation has confirmed the safety of cessation of therapy.³⁰

Special consideration must be given to patients with seizure disorders who are treated with valproic acid. Pediatric patients with progressive neuromuscular scoliosis are known to present with higher risk of intraoperative bleeding at baseline.³¹ When they are treated with valproic acid, platelet dysfunction leads to increased bleeding times, increased intraoperative bleeding, and higher rates of postoperative blood transfusion.³² Effective seizure management is an important component of perioperative care, and Chambers et al.³² suggest substituting another anticonvulsant for valproic acid 1 month prior to surgery if possible.

Preoperative autologous blood donation allows patients to have blood drawn and stored for their use on the day of surgery. Hypothetically, autologous blood circumvents the need for allogenic blood transfusion and the associated risks. The protocol for donation varies by institution, but blood is usually collected within 1 month of surgery, with one unit collected every 4-7 days, up until 3-7 days prior to surgery.³³,³⁴ Blood donation must be timed to ensure that patients do not arrive to their surgery with iatrogenic anemia, leading many practitioners to limit the number of units donated and recommend iron supplementation. Boniello et al.³³ limited their AIS patients to donate two units or less of autologous blood up until 3 days prior to surgery and found no difference in preoperative hematocrit compared to controls. In adult orthopedic patients, the use of EPO at the time of blood donation allowed patients to donate an average of 5.4 units of blood within 1 month of surgery without developing anemia.³⁵

While several early studies³⁶,³⁷ showed preoperative autologous blood donation to be effective in avoiding allogenic blood transfusions, with >90% of scoliosis patients avoiding the need for allogenic blood transfusion, enthusiasm has waned due to concern over efficacy and cost. In a multicenter retrospective study of spine patients, Garcia-Erce et al.³⁸ found that while autologous blood donation avoided allogenic transfusion in 78.8% of patients, donated blood was wasted in 38% of surgeries. A recent propensity-matched cohort analysis of 60 adult patients included in
the International Spine Study Group found that autologous blood donation did not protect against allogenic blood transfusion and that 30% of patients had all of their donated blood wasted.³⁹ In AIS patients, Bess et al.⁴⁰ reported that 51% of patients either had one or more units of blood wasted or were unnecessarily transfused for hematocrit >30%. Considering the rates of wasted autologous blood, it is important to consider the associated cost. Compared to allogenic blood from a blood bank, the labor-intensive process of preparing and storing an individual’s preoperatively donated blood is 30% more expensive.⁴¹ When factoring in the number of preoperatively donated units that are wasted, Etchason et al.41 found that the difference in cost increased to hundreds of dollars, making preoperative autologous blood donation cost-ineffective for most patients. In the face of high cost and concerns over efficacy, many surgeons seem to have turned their attention to other modalities of blood conservation, with the rate of preoperative autologous blood donation in pediatric idiopathic scoliosis between 2000 and 2009 dropping from 9.7% to 2.6%.⁴²

Prone positioning for posterior-approach spine surgery can help limit blood loss by decompressing the abdomen and decreasing inferior vena caval pressure. Modern spine tables, such as the Jackson Table (Mizuho OSI, Union City, CA), support the patient without midline pressure between the sternum and iliac crests, allowing the abdomen to expand ventrally. Lee et al.⁴³ found that prone positioning on a spine table allowed the abdominal viscera to hang freely with significant reduction in pressure within the inferior vena cava. In turn, pressure decreases in the epidural venous plexus, resulting in decreased intraoperative blood loss from epidural veins and decorticated cancellous bone during surgery. Using two randomized groups of spine patients positioned prone with and without constriction of the abdomen, Park et al.⁴⁴ found that patients positioned with the abdomen free had significantly less intra-abdominal pressure and lower total blood loss. Any patient undergoing spine surgery amenable to prone positioning should use this technique to limit blood loss.

Perioperative hypothermia (core temperature <36°C) can result from a combination of low OR temperature, cutaneous heat loss due to patient exposure during positioning, heat radiation from the surgical field, administration of intravenous fluids, and anesthesia-induced changes in thermoregulation. Michelson et al.⁴⁵ demonstrated that coagulopathy can result from reversible hypothermia-induced inhibition of platelet function. Even utilizing modern forced-air warming techniques, general anesthesia causes redistribution of body heat from the core to the periphery, resulting in hypothermia during the first hour of surgery in up to 64% of patients.⁴⁶ In a meta-analysis of all types of surgical patients by Rajagopalan et al.⁴⁷, even mild hypothermia of <1°C (below 36°C) increased blood loss by ˜16%, with a 22% increase in relative risk for blood transfusion.

Limited data exist on the effect of hypothermia on blood loss during spine surgery specifically; Guest et al.⁴⁸ found no association between mild hypothermia and
blood loss in their small series. In light of the existing evidence, clinical practice in many institutions is to maintain normothermia throughout a spine procedure. Initial cutaneous heat loss can be limited by increasing the ambient temperature of the OR and using blankets to minimize skin exposure, which can be significant during intubation, placement of neuromonitoring leads and Foley catheter, and patient positioning. Further losses can be prevented through the use of warmed intravenous fluids and forced-air warming blankets applied to the upper or lower extremities. Prone positioning also allows for warming blankets to be placed beneath the patient.

Acute normovolemic hemodilution (ANH) involves withdrawing autologous blood from the patient prior to incision, followed by volume replacement using warmed isotonic crystalloid at 3:1 ratio, with re-infusion of blood at the end of surgery, or within 6 hours of collection.⁴⁹ The volume of blood collected is based upon the preoperative hematocrit, and temporarily dilutes the blood by ˜30%, which in vitro has been shown to induce a mild hypercoagulable state and decrease bleeding.⁵⁰ The purpose of ANH is to maintain intravascular volume while diluting the concentration of red blood cells, in turn reducing overall blood loss. Epstein et al.⁴⁹ found that ANH was successful in avoiding allogenic blood transfusions in 76% of patients undergoing posterior lumbar laminectomy and fusion. In children with AIS, Copley et al.⁵¹ also reported that use of ANH significantly decreased the risk of blood transfusion compared to their control (37% vs 79%). While ANH has generally fallen out of favor relative to techniques like intraoperative blood salvage and antifibrinolytic medications, it remains a viable option for blood conservation in spine surgery.