Hematologic Disorders

Reduced hemoglobin concentration and compromised oxygen delivery form the physiologic basis for understanding anemia, a condition defined as hemoglobin below 12 g/dL in women and 13 g/dL in men. The body compensates through increased cardiac output and rightward shift of the oxyhemoglobin dissociation curve, yet the evidence base now favors restrictive transfusion strategies maintaining hemoglobin between 7 and 8 g/dL for most patients, with exceptions for those with active coronary disease who may require higher thresholds. Microcytic anemias including iron deficiency and thalassemia present distinct anesthetic challenges, particularly when skeletal malformations from severe thalassemia complicate airway management and when iron overload threatens organ function. Normocytic hemolytic conditions such as hereditary spherocytosis and glucose-6-phosphate dehydrogenase deficiency demand careful avoidance of oxidative stressors including specific medications, infection, and hypothermia. Sickle cell disease management has evolved away from mandatory exchange transfusion toward achieving hematocrit targets of 30% for moderate to high-risk procedures, while macrocytic anemias from vitamin B12 or folate deficiency can be worsened by nitrous oxide exposure. Polycythemia vera, often driven by JAK2 mutations, creates dual bleeding and clotting risks necessitating phlebotomy to reduce hematocrit below 45% preoperatively. Hemostasis disorders reflect a modern understanding of coagulation as a cell-based process involving initiation, amplification, and propagation phases rather than the older cascade model. Factor VIII and IX deficiencies require preoperative correction to 80 to 100% activity for major surgery, while von Willebrand disease responds to desmopressin in many cases. Heparin-induced thrombocytopenia type 2 represents a medical emergency requiring immediate heparin discontinuation and transition to alternative anticoagulants such as bivalirudin or argatroban. Hypercoagulable disorders span heritable conditions like Factor V Leiden and antithrombin deficiency alongside acquired states from malignancy, pregnancy, and antiphospholipid syndrome, each demanding distinct perioperative anticoagulation strategies. Warfarin management typically involves discontinuation 5 to 7 days preoperatively with bridging reserved for high-risk patients, whereas direct oral anticoagulants with shorter half-lives require no bridging but specific interruption intervals. Neuraxial anesthesia requires precise timing between anticoagulant dosing and needle placement or catheter removal to prevent spinal hematoma.