Eur J Cardiothorac Surg 1998;14:527-529
© 1998 Elsevier Science NL
Cardiopulmonary bypass in sickle cell anaemia without exchange transfusion
K. Frimpong-Boateng,
A.G.B. Amoah,
H-M. Barwasser,
C. Kallen
National Cardiothoracic Centre, Korle Bu Teaching Hospital, Post Office Box 77, Korle Bu, Accra, Ghana
Received 23 March 1998;
received in revised form 22 June 1998;
accepted 30 June 1998.
Corresponding author. Tel.: +233 21 780551; fax: +233 21 667196; e-mail: ctu@africaonline.com.gh
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Abstract
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To minimize sickling during cardiopulmonary bypass, exchange transfusion is frequently recommended peri-operatively for patients with homozygous sickle cell anaemia to reduce the circulating concentration of HbS. We report the successful management of two children both aged 12 years with sickle cell anaemia (homozygous SS), several sickle cell crises and multiple blood transfusions who underwent cardiopulmonary bypass for mitral valve replacement. No pre- or intra-operative exchange transfusions were employed in the two cases. Furthermore, moderate hypothermia in both cases was not associated with adverse sequelae.
Key Words: Cardiopulmonary bypass • Sickle cell anaemia • Exchange transfusion • Haemoglobinopathy
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Introduction
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The majority of cases of successful cardiopulmonary bypass surgery in patients with sickle cell haemoglobinopathies have sickle cell trait or sickle cell anaemia without significant history of sickle cell crises
[1]
[2]
[3]. To minimize sickling during cardiopulmonary bypass, exchange transfusion is frequently recommended peri-operatively for patients with homozygous sickle cell anaemia to reduce the circulating concentration of HbS
[4]
[5]
[6]
[7]. We report two cases with homozygous SS with repeated crises requiring multiple transfusions, who underwent successful mitral valve replacement using cardiopulmonary bypass without pre- or intra-operative exchange transfusion.
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Case report 1
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A.B., a 12-year-old Nigerian boy homozygous for Hb S gene (father AS; mother AS) with several hospital admissions for sickling crises, four of which had necessitated blood transfusions was found, on Doppler echocardiography with colour flow mapping, to have increased left ventricular end diastolic and systolic volumes and severe mitral regurgitation.
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Case report 2
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R.O. was a 12-year-old Ghanaian girl with sickle cell anaemia (SS genotype; father AS; mother AS) and several episodes of sickling crises and four previous blood transfusions. Evaluation with Doppler echocardiography with colour flow showed enlarged left atrium, increased LV end diastolic dimension and severe rheumatic mitral regurgitation.
Anaesthesia, cardiopulmonary bypass and surgery
In both cases, general anaesthesia was induced with ethomidate, fentanyl, midazolam and pancuronium and pre-bypass anaesthesia was maintained with isoflurane, oxygen (2 l/min) and nitrous oxide (2 l/min). Fentanyl and norcuron were administered intermittently to maintain analgesia and relaxation during surgery.
The cardiopulmonary bypass circuit was constructed with a MASTERFLOW bubble oxygenator, cardiotomy reservoir, filters, tubing sets and other accessories from DEDICO S.P.A. The heart-lung-machine (HLM) was primed with Ringer's Lactate (500–1000 ml), 5% dextrose (500 ml), 1 unit of blood and 8.4% sodium bicarbonate (40 mmol). Pre-bypass systemic heparinization was achieved by the administration of 300 units/kg heparin. The subjects were then connected to the HLM through aortic and bicaval cannulation. Cold St. Thomas cardioplegic solution was infused into the root of the cross-clamped aorta to achieve cardiac arrest and myocardial protection. Systemic hypothermia was maintained at nasopharyngeal and rectal temperatures of 28.4°C and 25.6°C (case 1) and 28°C and 25°C (case 2), respectively.
The haemoglobin and haematocrit during hypothermic bypass were 5.2 g/dl, 15.6% and 7.33 g/dl, 22% for cases 1 and 2, respectively. The mean arterial pressures were between 50 and 70 mm Hg and the partial pressure of oxygen during bypass ranged between 378 and 430 with a mean saturation of 99.8%. Blood pH was around 7.4 and bicarbonate level was 24.2–25.6 mmol/l.
In both cases, the mitral valve was approached through the atrial septum. The thickened and retracted or redundant valve tissue was excised and 29 mm, 27 mm Sorin bicarbon bileaflet mechanical prostheses implanted in the mitral area using 2–0 Cardiofil mattress sutures for cases 1 and 2, respectively.
Both subjects were weaned off cardiopulmonary bypass without difficulty. Exsanguinated blood in the oxygenator was discarded and not transfused. Instead, each subject received, post-operatively, two units of banked blood and post-transfusion haemoglobin levels were 10.0 gm/dl and 11.1 gm/dl, respectively. Anticoagulation was initiated with heparin, overlapped with warfarin on the third day and the heparin was withdrawn on the sixth post-operative day. The post-operative periods in both cases were uneventful and AB and R.O were discharged home three weeks later. On review a year after surgery, both patients were well on anticoagulant therapy and monthly benzyl penicillin and both had had no sickling crises or blood transfusions.
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Discussion
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To prevent sickling and its sequelae of haemolysis and vaso-occlusive crises during cardiopulmonary bypass, pre- and intra-operative exchange transfusion to reduce the percentage of sickle cells, have been recommended. Indeed, the majority of cardiac patients undergoing cardiopulmonary bypass have received pre-operative or intra-operative exchange transfusion
[1]
[2]
[3]
[4]
[5]
[6]
[7]. In the case of the two patients reported in this communication, no pre-bypass or intra-bypass exchange transfusions were performed and no adverse sequelae ensued in either case. Meticulous care was, however, taken to avoid dehydration, hypoxia and acidosis during pump bypass. It must be noted that, in the series of Metras et al., with sickle-cell hemoglobinopathies no pre-operative exchange transfusion was employed
[8]. In their series however, thirteen subjects had only sickle cell trait and none had the SS genotype. The use of hypothermia remains controversial in subjects with sickle cell disease undergoing cardiopulmonary bypass. Hypothermia can cause vasoconstriction and slugging of red cells and can therefore potentially increase capillary transit time and the risk of sickling of red cells. In view of this potential complication of hypothermia, some workers have avoided using hypothermia during cardiopulmonary bypass in sickle cell anemia
[9]. There is, however, evidence that hypothermia appears in vitro to slow polymerization of Hb S and delay the onset of sickling of the red blood cells. Indeed, a number of studies have employed hypothermia successfully in patients with sickle cell trait and sickle cell anaemia undergoing cardiopulmonary bypass during cardiac surgery
[1]
[5]
[6]. Moderate hypothermia did not adversely affect our two patients.
In order to avoid prosthetic valve-associated haemolysis, the use of prolonged anticoagulant therapy in chronically anaemic patients, and re-operation for degenerated bioprostheses, some workers have advocated the use of valve repair instead of valve replacement in sickle cell anaemia
[9]. On review a year after surgery, both patients with Sorin mitral valve prostheses were well on anticoagulant therapy and both had had no sickling crises and did not require blood transfusions. It is worthy to note that, in the first reported case of mitral valve replacement in sickle cell anaemia by Craenen et al.
[10], the patient had experienced no sickling crisis on coumadin two years after the operation. It appears anticoagulation may protect against haemolysis and vaso-occlusive crises. Increased cardiac performance and improved oxygenation may, however, be partly responsible for the absence of sickling crises in these patients. Furthermore, the frequency of sickling crises is known to decrease with age. In summary, we report two cases of successful mitral valve replacement with cardiopulmonary bypass and moderate hypothermia performed safely in sickle cell anaemia patients with a history of repeated sickling crises without pre- or intra-operative exchange transfusion.
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References
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Abstract
Introduction
