Extra Topic 1.2 -- Sickle Cell Disease

Question 1

What is the pathogenesis of sickle cell disease?

(A 24-year-old African-American man is scheduled for a laparoscopic appendectomy. He has a history of increasing abdominal pain over the last 12 hours complicated by nausea and vomiting. Past medical history is significant for sickle cell disease and his hematocrit is 21%.)

Answer 1

Sickle cell disease (SCD) is a well-defined hemoglobinopathy in which a mutation of chromosome 11 results in the substitution of valine for glutamic acid in the beta chains of hemoglobin (hemoglobin S).

In the presence of decreased oxygen tension, hemoglobin S (Hgb S) molecules can polymerize, causing deformation of the red cell membrane into a sickled shape, which leads to –

• hemolysis (average red blood cell life is 12-17 days instead of 120 days),
• microvascular occlusion of capillaries,
• ischemic injury to end organs,
• infarcts, and
• hemolytic crisis.

Question 2

What are the possible comorbidites associated with sickle cell disease?

(A 24-year-old African-American man is scheduled for a laparoscopic appendectomy. He has a history of increasing abdominal pain over the last 12 hours complicated by nausea and vomiting. Past medical history is significant for sickle cell disease and his hematocrit is 21%.)

Answer 2

*Don’t need to memorize. Just Be Aware of them!*

The chronic hypoxia, anemia, and hemochromatosis associated with sickle cell disease may lead to numerous clinical manifestations, including –

• cardiomegaly,
• congestive heart failure,
• pulmonary hypertension,
• neurologic deficits,
• renal insufficiency/failure,
• painful crises,
• acute chest syndrome,
• retinopathy, and
• aseptic necrosis of the femoral head.

In addition, multiple splenic infarcts usually lead to asplenia (via Splenectomy) by adolescence, predisposing these patient’s to – infection from encapsulated organisms.

Xtra Q – What is the typical lifespan of Hgb S?

Question 3

Does this patient need an exchange transfusion prior to surgery?

(A 24-year-old African-American man is scheduled for a laparoscopic appendectomy. He has a history of increasing abdominal pain over the last 12 hours complicated by nausea and vomiting. Past medical history is significant for sickle cell disease and his hematocrit is 21%.)

Answer 3

While in the past, preoperative exchange transfusions were recommended to reduce the Hgb S fraction to less than 40%,

there is growing evidence to suggest that achieving a preoperative hematocrit of 30% for patients undergoing moderate and high risk surgeries is just as effective in decreasing perioperative morbidity (low risk surgery rarely requires preoperative transfusion).

Moreover, aggressive exchange transfusion strategies require more transfusions, significantly increasing the risk of transfusion-related complications.

Therefore, since intra-abdominal procedures are considered moderate risk surgery, I would transfuse this patient to achieve a hamtocrit of 30%, with the goal of increasing oxygen carrying capacity and preventing sickling.

Question 4

How do you plan to prevent sickling in this patient?

(A 24-year-old African-American man is scheduled for a laparoscopic appendectomy. He has a history of increasing abdominal pain over the last 12 hours complicated by nausea and vomiting. Past medical history is significant for sickle cell disease and his hematocrit is 21%.)

Answer 4

Any condition that promotes the dissociation of oxygen from the hemoglobin molecule predisposes to red cell sickling.

Therefore, my anesthetic plan would be to avoid –

• hypoxemia,
• hypotension,
• hypothermia,
• acidosis, and
• hypovolemia.

Specifically I would –

• use supplemental oxygen in the perioperative period,
• avoid hypoventilation,
• assure adequate hydration with IV fluids,
• maintain a hematocrit between 30 and 40%,
• avoid hypothermia by the use of fluid warmers and forced air warming units, and
• provide adequate postoperative pain control.

Question 5

What is the treatment of sickle cell crisis?

(A 24-year-old African-American man is scheduled for a laparoscopic appendectomy. He has a history of increasing abdominal pain over the last 12 hours complicated by nausea and vomiting. Past medical history is significant for sickle cell disease and his hematocrit is 21%.)

Answer 5

The principle treatment of sickle cell crisis includes –

• ensuring adequate pain control
  
  • (note – pt may have narcotic resistance)
• providing intravenous hydration,
• administering supplemental oxygen,
• maintaining adequate hematocrit levels,
• treating infection, and
• considering an exchange transfusion to reduce the fraction of Hgb S to less than 40%.

Xtra Q – Would you perform an exchange transfusion?