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SICKLE CELL DISEASE
A) Pathophysiology
Hemoglobin has four types of globin chains in its molecules: Alpha, Beta, Delta and Gamma. Hb A
accounts for 97% of the human hemoglobin and it contains two Alpha and two Beta chains.
Hemoglobin A2 accounts for the remainder 3% and has two Delta and 2 Alpha chains. Patients with
sickle cell anemia have predominantly HbS and no HbA. This is because Valine replaces Glutamic
acid in the sixth position of the B chain. Sickle cell anemia is seen in 0.5 to 1% of the American
black population. Sickle cell trait occurs in 5-10% of the American black population. HbS has a
tendency to sickle when the SpO2 drops below 85%. Desaturated HbS being 50 times less soluble
than HbA aggregates into long stacks called tactoids which alter the shape of the red cell and cause it
to sickle. Survival of sickle cells in vivo is 5 -15 days (120 days for HbA). The oxyhemoglobin
dissociation curve is shifted to the right in patient’s with sickle cell disease.
B) Hemodynamic changes in sickle cell disease
a.
b.
c.
d.
e.
f.
Hemolytic anemia with HCt’s commonly being about 18-25%
Jaundice
Cerebrovascular accidents
High cardiac output, cardiomegaly
Pulmonary infarcts
Aseptic necrosis of the femur in 10% of patients
C) Anesthetic considerations of Sickle Cell Disease
a. Surgeries commonly performed include splenectomy, cholecystectomy, and hip arthroplasty (
for aseptic femoral necrosis)
b. Preop. Testing may include ECG, ECHO or radionucleotide cardiac imaging
c. Preoperative transfusion to keep HCT > 30 % thereby keeping HbS to less than 40% for
major surgeries and tonsillectomies if possible .The RBC transfusion would help prevent
endogenous erythropoieses of HbS cells.
d. Goals of anesthetic care include avoidance factors that induce sickling- hypoxia, acidosis, low
flow states such as vascular clamping, dehydration, hemorrhage , tourniquet application
hypothermia, hyperthermia and stress. Hyperventilation to avoid hypercarbia. Consider
keeping FIO2 above 40% (higher for thoracic and upper abdominal surgery)
Management of patients with Sickle Cell Trait
These patients have at least 50% HbS and the rest of the Hb is HbA. These patients rarely sickle.
Hypoxia stasis and hypercarbia should be avoided though sickling occurs with an SpO2 less than
40% in these patients.
Questions
Choose the best answer or answers1. The 4 crises of sickle cell disease area) Vaso-occlusive crises- acute chest syndrome, stroke, priapism
b) Hemolytic crises- anemia
c) Sequestration syndrome – liver and splenic sequestration of red cell causing massive
hepatomegaly, splenomegaly and resultant anemia
d) Aplastic crises with bone marrow suppression
(Answer: all the above)
2. Postoperative complications include
a) Sickling crisis from hypoxemia
b) Sequestration syndrome with crises in postpartum patients
c) Heart failure in patients with cardiomegaly
d) Prolongation of drug effects in patients with hepatic dysfunction
(Answer: all the above)