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J Thorac Cardiovasc Surg 2005;130:932-933
© 2005 The American Association for Thoracic Surgery
Brief Communication |
a Second Propaedeutic Department of Internal Medicine, Aristotle University of Thessaloniki, Hippokration Hospital
b Department of Hematology, St Luke's Hospital, Thessaloniki, Greece
c Thessaloniki Heart Institute, St Luke's Hospital, Thessaloniki, Greece
Received for publication January 23, 2005; accepted for publication February 22, 2005. * Address for reprints: Konstantinos Tziomalos, MD, 63 Solonos St, Thessaloniki, 54248 Greece
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Sickle cell disease presents a multitude of challenges in patients undergoing cardiac operations. In these patients, cardiopulmonary bypass (CPB) may trigger a crisis of profound magnitude. The prevention of sickling of red blood cells and its sequelae of hemolysis and vaso-occlusive crises during CPB is achieved primarily by reducing the level of hemoglobin S before operation.
1,2
Hemoglobin Lepore (
2[
ß]2) is a hemoglobin variant with a ß chain that is a result of fusion of a and a ß globin gene. The hybrid gene is expressed at a roughly intermediate level, between the and the ß globin genes. The phenotype of the heterozygote thus closely resembles the classical thalassemia trait. To date, only 20 cases of compound heterozygotes with hemoglobin Lepore/hemoglobin S have been reported, and they are characterized by hematologic as well as clinical heterogeneity. The hemoglobin S/hemoglobin Lepore combination may have enough hemoglobin S to cause serious sickling, particularly if an excess of chains were to have harmful consequences, as has been asserted.
3
We report a case of mitral valve reconstruction performed safely in a compound heterozygote for sickle cell anemia and hemoglobin Lepore.
Clinical Summary
A 26-year-old Greek man, compound heterozygote for sickle cell anemia and hemoglobin Lepore, came to our department with symptoms of progressive dyspnea and fatigue. His medical history was significant for several hospital admissions for sickling crises, one of which had necessitated blood transfusions.
On physical examination, the patient had a blood pressure of 100/70 mm Hg, a pulse of 90 beats/min, and a respiratory rate of 16 breaths/min. The heart had a regular rhythm, with a 3/6 apical holosystolic murmur radiating to the axilla. Further evaluation, including transesophageal echocardiography, disclosed severe mitral regurgitation, with prolapse of the anterior mitral valve leaflet, accompanied by annular dilatation and significant left atrial and left ventricular enlargement. Left ventricular internal dimensions during diastole and systole were 68 mm and 54 mm, respectively. Catheterization demonstrated a pulmonary artery pressure of 45/21 mm Hg and a left ventricular end-diastolic pressure of 22 mm Hg. The ventriculogram noted global hypokinesis, with an ejection fraction of 0.43. Coronary angiography showed no abnormalities. The patient was referred for mitral valve repair.
Approximately 1 week before the operation, the patient underwent therapeutic phlebotomy and exchange transfusion with leukocyte-depleted, phenotypically matched packed erythrocytes to decrease the level of hemoglobin S. Hemoglobin and hematocrit at that time were 10.2 g/dL and 33.2%, respectively. Hemoglobin electrophoresis demonstrated 77.5% hemoglobin S. After the exchange transfusion, hemoglobin and hematocrit remained stable, but hemoglobin S was only 44.5%.
The procedure was carried out with normothermic (37°C) CPB. After crossclamping of the aorta, intermittent, antegrade, hyperkalemic warm blood cardioplegia supplemented with magnesium was administered in the aortic root.
4
The mitral valve was approached through the superior septal approach. It was found to be a Barlow type of valve, with annular dilatation and excess tissue in both mitral leaflets. It was repaired with a flexible mitral ring (size 36 mm Annuloflex; Sulzer Carbomedics Inc, Austin, Tex). Aortic crossclamp time was 32 minutes. Intraoperative transesophageal echocardiography showed no residual mitral regurgitation.
The patient had an uneventful postoperative recovery. He was discharged from the hospital on the sixth postoperative day.
Discussion
The absolute safe level of hemoglobin S during operations with CPB has not been clearly defined. A growing body of evidence suggests that limited dilution of sickle cells is beneficial. In a pivotal study, a preoperative hemoglobin S level of 30% or less allowed elective surgery to be performed safely in patients with sickle cell disease; these values may represent a suitable aim for patients undergoing CPB.
5
Hemoglobin S reduction can be achieved by simple transfusion for several weeks preoperatively, partial exchange transfusion in the preoperative period, complete exchange transfusion with the CPB circuit, or a combination of these techniques.
1,2
Preoperative exchange transfusion increases the percentage of hemoglobin A relative to that of hemoglobin S and, more importantly, suppresses further production of hemoglobin S.
During an operation, predisposing factors that elicit sickling (including hypoxia, low-flow states, hypovolemia, acidosis and hypothermia) should be avoided.
1,2
Hypothermia can cause vasoconstriction and slugging of red cells and therefore potentially increase capillary transit time and the risk of sickling of red cells. In view of this potential complication of hypothermia, we aimed to perform warm heart surgery with normothermic CPB of the minimum duration.
In conclusion, preoperative exchange transfusion enabled us to perform mitral valve repair uneventfully in a compound heterozygote for sickle cell anemia and hemoglobin Lepore.
References
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