Extracorporeal membrane oxygenation (ECMO) has been widely used for cardiopulmonary mechanical support throughout the last three decades. Its indications have evolved from respiratory failure1 to cardiac failure2 as a bridge to recovery or transplant. In surgery for congenital heart disease, ECMO support is specially indicated for lesions and procedures in which a physiologic adaptation or a transient myocardial dysfunction is expected. The most common clinical practice in postcardiotomy ECMO technique involves the replacement of the conventional extracorporeal circuit with a special closed ECMO circuit and oxygenator. We previously described our initial experience with a modification of the cardiopulmonary bypass (CPB) circuit to create a closed ECMO circuit for short-term support, by using the standard parts of a conventional CPB circuit.3 In this article, we present our 4-year experience with the use of immediate postcardiotomy ECMO at Ricardo Gutierrez Children’s Hospital.
Patients and Methods
From November 2001 to December 2004, a specially designed CPB circuit was indicated in 25 patients in whom the need of postoperative ECMO was expected. The indications were the diagnosis of anomalous left coronary artery arising from pulmonary artery, hypoplastic left heart syndrome, transposition of the great arteries in patients older than 4 weeks of life, and preoperative severe heart failure with inotropic use and assisted ventilation. Eight patients (Table 1) who could not be reliably weaned from CPB because of severe low cardiac output received short-term cardiac ECMO with this technique.
The CPB circuit was modified to allow its use postoperatively as an ECMO circuit. A bypass containing an ECMO bladder (VRECMOS, Gish Biomedical, Rancho Santa Margarita, CA, or R 1/4, R 3/8, Medtronic Inc., Minneapolis, MN) was inserted in the venous line, bypassing the cardiotomy reservoir (Figure 1). The bladder was not primed to allow resterilization. A longer S-70 PVC tube was used for the raceway. The hemofilter was placed in the arterial line (Figure 1). A pump console with interchangeable pump modules was used to allow removal and placement of the module on the ECMO cart (CINCO, Wakefield, MA). Medtronic Minimax Plus oxygenators (Medtronic Inc.) were use in patients 1, 2, and 3. Patients 4, 5, 7, and 8 received Polystan Safe oxygenators (Polystan AS. Værløse. Denmark). Patient 6 was supported with a Braile Oxygenator (Braile Biomédica, São José do Rio Preto, SP, Brazil).
Cardiopulmonary bypass and ECMO were conducted in the usual fashion via right atrial and aortic cannulation. Patient 3 required left atrial cannulation through the superior right pulmonary vein.
Extracorporeal Membrane Oxygenation Technique
After ruling out residual lesions by direct exploration and transesophageal echocardiography, the patient was weaned from CPB by high-dose inotropic support for at least 10 minutes for full heparin reversal administration and platelet administration. Meticulous exploration of bleeding and hemostasis was then performed. When placement on ECMO was mandatory, the patient went back on CPB without heparin administration. Using this method, the activated clotting time (ACT) dropped from a mean (SD) of 590 ± 77 to a mean of 250 ± 34.
The line containing the bladder was then blood-primed, the line to the cardiotomy reservoir was closed, and the line to the ECMO bladder was opened (Figure 2). The ACT was then dropped to 200 seconds by adding protamine sulfate to the ECMO prime, and heparin infusion at 20 U kg/h was started. While the surgical team worked on hemostasis, the pump team placed the ECMO bladder in the ECMO bladder box and connected its electrical output to the pump module. The pump module was then removed from the pump console and placed with the bladder box in a battery-operated two-level ECMO cart. The cardiotomy reservoir was removed and discarded and its in and out lines secured (Figure 2). Additionally, the oxygenator and the ECMO bladder box were mounted on the ECMO cart. When bleeding control was achieved, the sternum was left open, and conventional dressings were applied in the wound. Patients were transported to the intensive care unit using the top level of the ECMO cart as a bed. ACT levels were kept at 180 seconds during the first postoperative day and subsequently raised to 200 seconds. A bleeding of more than 15 ml·kg–1·h–1 was considered as an indication for re-exploration. All re-explorations and decannulations were performed in the cardiac intensive care unit.
Support and Survival
The support time ranged from 12 hours to 6 days, with a mean of 3.1 days. Six patients recovered function, and five were weaned and decannulated. Four patients (50%) survived to hospital discharge, without late deaths and with normal growth and development according to their pediatricians. One of the survivors underwent a bidirectional Glenn Shunt as part as the staged pathway for hypoplastic left heart syndrome.
Four patients presented severe bleeding requiring re-exploration. Three patients presented seizures, and two of them advanced to brain death. One patient presented fungal sepsis due to Candida albicans and did not survive.
Fate of Conventional Oxygenators
The durability of conventional oxygenators was strongly associated with the extent of anticoagulation level used. When the ACT was kept above 200 seconds, these oxygenators have lasted up to 5 days. Because of severe bleeding, three patients required an ACT level below 180 seconds. Within hours plasma leakage and poor oxygenation function developed, and oxygenator replacement was required (Table 1).
At present, ECMO continues to be the mainstay support device in congenital heart surgery, unless there is isolated left ventricular dysfunction. Postcardiotomy ECMO has shown a dramatic improvement in survival, with a hospital survival of 50% in large series.4 The survival rate of ECMO has been more favorable for patients with transient myocardial dysfunction in absence of residual lesions.5
However, the cost of ECMO continues to prevent the increased use of this lifesaving technique in programs with limited resources, particularly in developing countries. The specific ECMO pack and oxygenator and hardware have a cost of approximately US $2,000 per patient. The opportunity of using the same circuit that was used in the extracorporeal circulation allows a significant drop in expenses reaching an extra cost of only US $200, which is the price of the ECMO bladder. Furthermore, if the ECMO circuit is not used, the bladder is not primed and can be re-sterilized. Thus, ETO resterilization of the ECMO bladder when ECMO is not needed is the only extra cost of this technique.
Unlike respiratory ECMO, cardiac ECMO has shown a much faster recovery of function, with a mean support time of 3 to 5 days in most series.5 With this in mind, we thought that we might have a window of opportunity by using conventional oxygenators. Conventional membrane oxygenators, such as the Medtronic Minimax Plus, have been used for short-term ECMO with the required durability.6 This technique has several advantages other than cost itself: it decreases the use of blood products, increases hemodynamic stability because there is no need for reconnecting cannulas to the ECMO circuit, and eases transportation. Another advantage of the method is the possibility of performing hemofiltration on conventional CPB and on ECMO using the same hemofilter.
In conclusion, this method simplifies the ECMO technique for cardiac support after reparative heart surgery, minimizing cost and hardware use, and may contribute to its widespread use in the less privileged areas of the world.
Dardo Fernandez Aramburu, MD, undertook surgical care of patient 3.
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