Introduction
Blood is the carrier of oxygen because of hemoglobin in the red blood cells (RBCs). It also plays an important role in the cessation of bleeding by virtue of its components, that is, platelets, coagulation factors, and fibrinogen. Deficiency and/or loss of functional capability of these components can cause life-threatening bleeding during the perioperative period. Thorough knowledge of blood disorders makes the anesthesia provider confident and efficient in managing such a group of patients.
Anemia
Anemia is defined as a decrease in the oxygen-carrying capacity of blood due to a decrease in red cell mass. It is often encountered in surgical populations preoperatively and can result from iron deficiency, deficiency of vitamin B12, chronic disease states (e.g., tuberculosis, malignancy, etc.), and hemoglobinopathies. It is not simply a laboratory diagnosis but an important predictor of negative clinical outcomes. Preoperative evaluation for the cause of anemia and optimization of the same improves patient’s outcome drastically. WHO defines anemia as follows:
Anesthetic Concerns in Anemia
Preoperative
Rule out hyperdynamic circulation and consequent heart failure in preoperative evaluation.
The optimal cutoff of hemoglobin to post a patient for elective surgery is not known. However, hemoglobin of ≥ 8 g/dL for the normal healthy patient and ≥ 10 g/dL for patients with cardiac morbidities, stroke, and epilepsy is usually considered safe.
Rule out neurological deficit due to vitamin B12 deficiency.
Intraoperative
Minimize blood loss with controlled hypotension.
Estimate blood loss with a visual inspection of the surgical field, drainage container, and number of blood-soaked pads and their weight.
Use restrictive approach to replace blood lost during surgery to avoid complications of allogeneic blood transfusion.
Avoid triggers of increased oxygen demand (e.g., pain, shivering).
Avoid regional anesthesia in patients with documented neurological deficit.
Avoid nitrous oxide in vitamin B12 deficiency because nitrous oxide can cause megaloblastic anemia.
Cautious use of intravenous and inhaled anesthetics in patients with hyperdynamic circulation (vasodilatory effects of anesthetic agents can cause precipitous fall in blood pressure).
Sickle Cell Disease
Sickle cell hemoglobinopathy occurs due to mutation in the β-globin subunit, leading to the abnormal assembly of beta proteins of hemoglobin A and consequent sickling of red cells when exposed to triggers (e.g., dehydration, pain, hypoxia, static blood flow, etc.).
Anesthetic Concerns
Preoperative
Rule out vasoocclusive end-organ damage:
Central nervous system (CNS): Stroke, proliferative retinopathy, peripheral neuropathy.
Pulmonary: Acute chest syndrome, restrictive lung disease.
Gastrointestinal tract (GIT): Liver disease, cholelithiasis.
Hematological: Hemolytic anemia.
Orthopedic: Osteomyelitis, dactylitis.
Cancel or postpone the surgery if the patient is in acute sickle cell crisis.
Avoid preoperative dehydration to prevent sickling. Also, address anxiety and stress with benzodiazepines.
Target hemoglobin of 10 g/dL (hematocrit [HCT] of 30%) with HbS < 30% and prophylactic transfusion in moderate-to-high risk cases.
HbS level < 5% is considered optimal for the patient undergoing cardiac bypass surgery.
Intraoperative
All techniques of regional block appear to be safe in sickle cell disease. Bier’s block is no more an absolute contraindication in patients afflicted with sickle cell disease.
Avoid hypoxia, hypothermia, dehydration, and acidosis in the intraoperative period to prevent sickling.
The use of tourniquets is not absolutely prohibited in sickle cell patients; however, their use is definitely associated with increased risk of complications.
Postoperative
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