Asian Cardiovasc Thorac Ann 2006;14:485-488
© 2006 Asia Publishing EXchange Ltd
Postcardiotomy Extracorporeal Life Support
Hakki Kazaz, MD,
Eyup Hazan, MD1,
Öztekin Oto, MD1,
Nejat Sariosmano
lu, MD1,
Nuran A Dereli, PhD1
Gaziantep University School of Medicine, Department of Cardiovascular Surgery, Gaziantep, Turkey
1 Dokuz Eyliil University School of Medicine, Department of Thoracic and Cardiovascular Surgery 
zmir, Turkey
For reprint information contact: Hakki Kazaz, MD Tel: 90 342 360 1126 Fax: 90 342 360 1126 Email: hakki{at}kazaz.info, Gaziantep University School of Medicine, Cardiovascular Surgery Dept., Universite bul. Kilis yolu, 
ahinbey, Gaziantep, Turkey.
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ABSTRACT
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The need for postcardiotomy mechanical support is uncommon and likely to decline. A mixture of options is necessary to meet the diverse indications for cardiac support in a comprehensive heart failure program. Between January 1997 and December 2000, 29 adult, neonate, and infant cardiac surgical patients were supported on an extracorporeal life support system. Indications for cardiac assist included post-cardiotomy low cardiac output syndrome, and hyperacute rejection after cardiac transplantation. Data for analysis were collected prospectively. Survival on the life support system was 20/29 (69%) and 12 patients (41%) survived to discharge. The mean time to starting extracorporeal life support was longer in survivors than non-survivors. The extracorporeal life support system provides effective cardiopulmonary and end-organ support.
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INTRODUCTION
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Mechanical cardiac assist is an integral component of a multidisciplinary adult heart failure program.1 Indications for cardiac assist include: chronic cardiac support as a bridge to recovery; bridging to transplantation; short-term support in postcardiotomy cardiogenic shock; temporary support for high-risk cardiology interventions; and emergency cardiac resuscitation, especially in neonate foreign body aspiration recovery, congenital diaphragmatic hernia, and acute respiratory distress syndrome.1 Additional indications are hypothermia, pulmonary embolism, and trauma. Fortunately, the need for postcardiotomy mechanical circulatory support is uncommon and likely to decline.1 Postcardiotomy support in the form of intra-aortic balloon pump (IABP) counterpulsation is needed in 4% of patients, and more advanced support is necessary in 0.2% to 1.2%.2,3
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PATIENTS AND METHODS
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Between January 1997 and December 2000, 1,154 patients underwent open heart surgery in our institute, of whom 29 (2.5%) had extracorporeal life support (ECLS). Most of these patients had undergone coronary artery bypass grafting, valve surgery or congenital heart disease repair (Table 1
). Ages ranged from 15 days to 64 years, and 31% were female. The indications for ECLS were: IABP or maximum inotropic support (> 10 µg·kg–1·min–1 dopamine and/or dobutamine, > 0.5 µg·kg–1·min–1 epinephrine) for > 30 min after arrival in the intensive care unit to maintain systolic blood pressure > 75 mm Hg and cardiac index > 2.0 L·min–1·m–2; IABP and inotropic support to avoid rapid falls in blood pressure and cardiac index; cardiac arrest and resuscitation > 15 min; and primary dysfunction or hyperacute rejection in cardiac transplant patients. Those who failed to separate from cardiopulmonary bypass (CPB) were excluded. Extracorporeal life support patients were ventilated with a volume-controlled ventilator at a fraction of inspired oxygen of 50% or less, the respiratory rate was set to 8 breaths·min–1 or less, with a tidal volume of 10 mL·kg–1 and a positive end-expiratory pressure of 5 cm H2O. Ventilator settings were adjusted to maintain peak airway pressure < 35 H2O. All 29 patients had venoarterial ECLS. Cannulation was via a transthoracic or femoral approach, depending on the indications and individual patient characteristics. Peripheral cannulation (common femoral artery and vein) was used in 2 patients, and central cannulation (ascending aorta and right atrium) in 27.
The system comprised a hollow-fiber membrane oxygenator with an integral heat exchanger (< 0.33 m2 Lilliput I, 0.33–0.64 m2 Lilliput II, 0.64–1 m2 Dideco 705 for infants and pediatric patients, > 1 m2 Dideco 708 for adults), a centrifugal pump (Sarns 9000; 3M Health Care, Ann Arbor, MI, USA) for adults and a roller pump (Sarns) for neonates and infants, an oxygen/air blender (original adapted mixer on the Sarns 9000), and a water heater/cooler (Sarns). Flow rates for the pump and membrane oxygenator were maintained at a ratio that ensured efficient oxygenator function. Membrane changes were carried out every 48 hours or sooner if evidence of decreased permeability occurred. Low-dose inotropics were used during the support period to maintain contractility and reduce interventricular blood stasis. An IABP was inserted in most patients to reduce afterload, improve coronary perfusion, and add a pulsatile component to the circulation. During assist, bolus injections of heparin were used to maintain an activated clotting time (ACT) > 160 sec during full flow (an ACT > 180–190 sec was maintained in patients with artificial valves). A continuous drip was used to achieve an ACT > 200 sec during a significant reduction in pump flow in trial weaning. Extracorporeal life support was removed when a weaning trial demonstrated cardiac index > 2.2 L·min–1 and systolic blood pressure > 75 mm Hg. As ventricular recovery progressed, pump flow was gradually reduced. Full flow was promptly re-instituted if necessary. During trial weaning, pump flow was gradually decreased to < 1 L·min–1 for 2–3 min; if the patient tolerated this flow, ECLS was stopped.
Data collection was undertaken during the support period using standardized forms to record medical history, hospital course, laboratory and hemodynamic parameters, and ECLS variables. Statistical analysis was performed with SPSS version 10.0 software (SPSS, Inc., Chicago, IL, USA). Descriptive statistics were summarized as the mean and standard deviation for continuous variables when they were approximately normally distributed. Data that were not distributed normally were represented as median and 25%–75% interquartile range (IQR). Categorical variables were expressed as percentages where independent samples such as the t test and chi-squared test were used to compare population variables.
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RESULTS
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Mean time to starting ECLS after arrival in the intensive care unit was 105.93 ± 105.23 min (range, 14–434 min; IQR, 23.5–175.5 min). Extracorporeal life support start time for survivors was later than for non-survivors (Table 2). Mean perfusion time was 149.14 ± 49.93 min (range, 84–258 min). Perfusion time for survivors was not significantly longer than for non-survivors. Flow on ECLS was 3–4 L·min–1 in both groups. Mean duration of assist was 33.96 ± 24.41 hr (range, 10.75–112.5 hr; IQR, 17.8–40.9 hr), and it was similar in both groups. Mean pH at the start of ECLS was 7.14 ± 0.13 (range, 6.85–7.40) and the difference between the groups was not significant (Table 2). Serum K+ at the start of ECLS was 5.61 ± 1.11 mEq·L–1 (range, 3.8–7.8 mEq·L–1) and was similar in both groups. Serum K+ after ECLS was 4.73 ± 0.46 mEq·L–1 in the survivors. Mean blood requirement on ECLS was 5.41 ± 4.51 units of packed red blood cells and/or fresh frozen plasma. Mean ultrafiltration volume on ECLS was 909.31 ± 721.01 mL (range, 50–3,050 mL). Non-survivors had a significantly greater ultrafiltration volume.
Twenty patients (69%) were weaned from ECLS, and 12 (41%) were discharged from the hospital. The causes of death in non-survivors were: primarily refractory ventricular failure (7/9, 78%); multisystem failure and sepsis (1/9, 11%); and hyperacute transplant rejection (1/9, 11%). The causes of death in survivors who could not be discharged from the hospital were: recurrent hyperacute rejection episode (2/8, 25%); refractory ventilator dependence and sepsis (2/8, 25%); refractory ventricular failure and multisystem dysfunction (3/8, 38%); and infection (1/8, 13%).
Complications occurring while on ECLS included: infection (pneumonia, bacteremia, and sepsis) in 4 (14%) patients; need for dialysis in 2 (7%); neurologic events (intracranial bleeding) in 1 (3%); and limb ischemia in 1 (3%). The infections were unrelated to the ECLS system or cannulation site. The most common microorganisms were Staphylococcus aureus and Klebsiella pneumoniae. In survivors, respiratory complications included refractory ventilator dependence in one (5%; 3% in all ECLS patients), and tracheostomy before ventilator weaning in 4 (20%). The mean time to extubation after weaning from ECLS was 2.7 ± 1.9 days (range, 18 hr to 7 days.) Mean stay in the intensive care unit was 9.4 ± 5.2 days (range, 3.5 to 18 days). Postoperative hospital stay was 16.7 ± 4.1 days (range, 11 to 22 days). Platelet destruction and hemolysis were common during ECLS. Mean platelet count before ECLS was 183.10 ± 48.61 K·µL–1; after 48 hours on ECLS it was 93.62 ± 30.64 K·µL–1. In survivors, these counts were 189.50 ± 52.18 K·µL–1 and 102.50 ± 29.44 K·µL–1, respectively (Wilcoxon signed ranks test: p = 0.001), in the non-survivors, they were 168.89 ± 38.39 K·µL–1 and 73.89 ± 24.34 K·µL–1 ( p = 0.008). The flow in the centrifugal pump was 3.5–4.0 L·min–1.
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DISCUSSION
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The aim of ECLS is to provide circulatory and/or respiratory support over a period of days or a few weeks until the native heart or lungs recover.4,5 Extracorporeal life support was first used successfully in 1972, and was applied in a newborn with respiratory distress syndrome in 1976.6,7 In selected adults with acute respiratory distress, survival on ECLS is approximately 50%. In neonates with respiratory insufficiency, the survival rate is 80%–90%.8 When used for circulatory support following open heart surgery, the survival rate (discharged from hospital) in infants and children is 32.4%–45%.9,10 In adults, survival rates are slightly lower.1,11 The percentage of patients weaned from ECLS is 65%–75%.1 In our study, 69% were weaned from ECLS and 41% were discharged. We have noticed that in high-risk infants and pediatric patients, peritoneal dialysis decreased the need for ECLS. We have had considerable experience with postcardiotomy open-chest management. Thoracic access for cardiac observation, control of bleeding, and resolution of cardiac edema were improved by early peritoneal dialysis for volume overload, and by avoiding the decrease in cardiac output due to compression of the heart. These are important advantages of this approach, especially over short support periods (2–3 days).12
Low cardiac output syndrome (LCOS) is a critical complication during weaning from CPB and in the early period after open heart surgery. Treatment alternatives for LCOS include: managing the circulation in an empty heart during weaning from CPB; administering inotropics; continuing IABP support in those who had preoperative IABP insertion; applying warm blood cardioplegia before aortic declamping; and ensuring optimal myocardial protection during CPB. In normal hearts, a marked reduction in preload and a small increase in afterload produced by arterial inflow from the ECLS system reduces wall stress and results in a smaller end-diastolic left ventricular volume because the heart is able to eject the blood it receives. However, if the heart is dilated and poorly contracting, the left ventricle cannot eject sufficient volume against the increased afterload to reduce either end-diastolic or end-systolic volume. Thus, ECLS may increase left ventricular wall stress and myocardial oxygen consumption unless an IABP or other means is used to mechanically unload the left ventricle.
Usually, the femoral vessels are used for inflow and outflow in ECLS. Peripheral cannulation has been used for ECLS in patients supported for respiratory diseases and for certain minimally invasive cardiac procedures. In those with severe peripheral vascular disease and patients who cannot be weaned from CPB, aortic and right atrial catheters may be used. The external iliac vessels exposed through a small retroperitoneal incision are an alternative peripheral cannulation site. The axillary artery has been used but it is associated with progressive edema of the arm. In our postcardiotomy ECLS experience, aortic and right atrial catheters were used in the majority of patients because: in LCOS due to peripheral collapse, it is difficult to insert percutaneous cannulas and considerable time is required for cutdown; it reduces the infection risk; preparation for the operation takes only 10 to 21 min (mean, 13.59 ± 2.72 min); there is a positive impact on cardiac edema after opening the sternum; and it allows prognostic assessment of heart rate.
A major use of ECLS is as a bridge to transplantation. We applied ECLS in 3 cases of hyperacute transplant rejection; 2 of the patients were weaned from ECLS but died due to rejection and right ventricular insufficiency. As there was no suitable cardiac donor, the remaining patient also died. In our country, it is very difficult to find donors for such patients. Magovern and Simpson1 reported that 7 of 111 patients undergoing cardiac transplantation required support for graft failure in the immediate post-transplant period.
Extracorporeal life support is the only circulatory support system that does not require a thoracotomy, and it can be rapidly implemented in critical care and cardiac catheterization units.13 For this reason, it has been used during high-risk catheterization procedures such as angioplasty or stent deployment.13 Indications for ECLS-supported interventions are refractory unstable angina or congestive heart failure in a patient judged to be at high risk due to left ventricular dysfunction or serious comorbidity (lung disease, end-stage renal disease, peripheral vascular disease, advanced age, obesity, constructive pericarditis, or terminal mediastinal cancer). Other important indications are emergency cardiac resuscitation and embolectomy for massive pulmonary embolism. We applied ECLS in one patient after embolectomy for massive pulmonary embolism. This patient was weaned from ECLS but died from pulmonary infection. Risk factors for ECLS were reported by Smedira and Blackstone.2 Ejection fraction < 20%, emergency surgery, and female sex were found to be strong predictors of LCOS after coronary artery bypass surgery. Diabetes mellitus, age > 70 years, and recent myocardial infarction are additional risk factors. The widespread use of ECLS in recent years shows that it is an effective treatment alternative for LCOS, and the indications for ECLS are increasing. We recommend that ECLS be started as soon as possible before hemodynamic and metabolic deterioration.
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REFERENCES
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- Magovern GJ Jr, Simpson KA. Extracorporeal membrane oxygenation for adult cardiac support: the Allegheny experience. Ann Thorac Surg 1999;68:655–61.[Abstract/Free Full Text]
- Smedira NG, Blackstone EH. Postcardiotomy mechanical support: risk factors and outcomes. Ann Thorac Surg 2001;71(3 Suppl):S60–6.[Abstract/Free Full Text]
- Torchiana DF, Hirsch G, Buckley MJ, Hahn C, Allyn JW, Akins CW, et al. Intraaortic balloon pumping for cardiac support: trends in practice and outcome, 1968 to 1995. J Thorac Cardiovasc Surg 1997;113:758–69.[Abstract/Free Full Text]
- Schoen FJ. Pathologic considerations in the surgery of adult heart disease. In: Cohn LH, Edmunds LH Jr, editors. Cardiac surgery in the adult. New York: McGraw-Hill, 1997:85–144.
- Edmunds LH. Extracorporeal perfusion. In: Cohn LH, Edmunds LH Jr, editors. Cardiac surgery in the adult. New York: McGraw-Hill, 1997:255–94.
- Anderson HL 3rd, Delius RE, Sinard JM, McCurry KR, Shanley CJ, Chapman RA, et al. Early experience with adult extracorporeal membrane oxygenation in the modern era. Ann Thorac Surg 1992;53:553–63.[Abstract]
- Bartlett RH, Gazzaniga AB, Jefferies MR, Huxtable RF, Haiduc NJ, Fong SW. Extracorporeal membrane oxygenation (ECMO) cardiopulmonary support in infancy. Trans Am Soc Artif Intern Organs 1976;22:80–93.[Medline]
- Zwischenberger JB, Nguyen TT, Upp JR Jr, Bush PE, Cox CS Jr, Delosh T, et al. Complications of neonatal extracorporeal membrane oxygenation. Collective experience from the Extracorporeal Life Support Organization. J Thorac Cardiovasc Surg 1994;107:838–49.[Abstract/Free Full Text]
- Raithel SC, Pennington DG, Boegner E, Fiore A, Weber TR. Extracorporeal membrane oxygenation in children after cardiac surgery. Circulation 1992;86(5 Suppl):II305–10.
- Huang SC, Wu ET, Chen YS, Chang CI, Chiu IS, Chi NH, et al. Experience with extracorporeal life support in pediatric patients after cardiac surgery. ASAIO J 2005;51:517–21.[Medline]
- Anderson H 3rd, Steimle C, Shapiro M, Delius R, Chapman R, Hirschl R, et al. Extracorporeal life support for adult cardiorespiratory failure. Surgery 1993;114:161–73.[Medline]
- Furnary AP, Magovern JA, Simpson KA, Magovern GJ. Prolonged open sternotomy and delayed sternal closure after cardiac operations. Ann Thorac Surg 1992;54:233–9.[Abstract]
- Muehrcke DD, McCarthy PM, Stewart RW, Foster RC, Ogella DA, Borsh JA, et al. Extracorporeal membrane oxygenation for postcardiotomy cardiogenic shock. Ann Thorac Surg 1996;61:684–91.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
