A 13-year-old girl in her usual state of health presents from home with a history of hemoglobin SS (HbSS) for laparoscopic cholecystectomy. The patient has had a history of multiple sickle cell crises, with her most recent episode of acute chest syndrome occurring 6 months ago.
Laboratory: Hematocrit is 26.
Sickle cell disease results from an inherited structural disorder of the hemoglobin β-globin chain. There is a wide range of severity and speed of progression, with clinical consequences ranging from benign sickle trait to severe symptomatology in homozygous HbSS patients. Patients with severe disease may have a history of chronic hemolytic anemia, frequent vaso-occlusive crises, and chronic organ damage, including cardiomegaly, pulmonary hypertension, and ischemic strokes. These patients are at higher risk for perioperative complications.
HbSS patients are at risk of having their red blood cells form distorted sickle cells when the patient is exposed to hypoxia; this is exacerbated by acidosis, dehydration, or hypothermia with vasoconstriction. Hypoxia with a PaO2 below 40-50 mm Hg typically results in the formation of sickle cells, but sickling can be seen even in well-oxygenated SS cells. Increased age or the presence of infection can also increase the risk of sickling.
Preoperative transfusion regimens range from aggressive (lowering the HbS to less than 30%), to conservative (correcting only the anemia), to not transfusing at all. Some studies have shown that for low- to moderate-risk procedures, maintaining a Hb of 10 g/dL results in no outcome differences from a more aggressive technique and has the added benefit of reducing transfusion-related complications. As a result, the trend in perioperative transfusions has been moving toward a more conservative approach. The decision to transfuse, however, needs to be made based on the risk factors of each individual patient, and consultation with a hematologist is recommended for complicated patients. The cross-matching of blood for patients who have had multiple transfusions may be a problem, and blood availability should be addressed prior to the start of surgery. An additional consideration is that preoperative medications that can depress spontaneous ventilation should be used with caution and supplemental oxygen should be considered.
In the case of this child, a blood transfusion would be recommended as well as a consultation with the patient’s hematologist to determine her baseline hematocrit and transfusion goals.
Anesthetic goals include maintaining oxygenation and normothermia while avoiding hypovolemia, acidosis, infection, and stasis.
The use of tourniquets for orthopedic surgery is controversial, and the risk of precipitating an acute event must be weighed against the benefit of decreased bleeding.
Controversy exists over the use of general versus regional anesthesia, with some studies showing worsened outcomes with regional anesthesia, while others show no difference.
In cases requiring contrast dye, the use of hypertonic dye has been thought to induce sickling, so ...