doi:10.1510/icvts.010.58384 Interactive CardioVascular and Thoracic Surgery 1 (011) 676 680 www.icvts.org Institutional report - Assisted circulation Extracorporeal membrane oxygenation for acute respiratory distress syndrome: is the configuration mode an important predictor for the outcome? a,1 a,1 a b c Frederik Stöhr, Maximilian Y. Emmert, Mario L. Lachat, Reto Stocker, Marco Maggiorini, a a, Volkmar Falk, Markus J. Wilhelm * a Clinic for Cardiovascular Surgery, University Hospital Zurich, Zurich, Switzerland b Division of Surgical Intensive Care, University Hospital Zurich, Zurich, Switzerland c Department of Internal Medicine, Intensive Care Unit, University Hospital Zurich, Zurich, Switzerland Received 18 October 010; received in revised form 14 January 011; accepted 19 January 011 Abstract Extracorporeal membrane oxygenation (ECMO) is increasingly applied as rescue-therapy for patients with severe acute respiratory distress syndrome (ARDS). Here, we evaluate the effect of different configuration strategies (venovenous vs. venoarterial vs. veno-venoarterial) on the outcome. From 006 to 008, 30 patients received ECMO for severe ARDS. Patients were divided into three groups according to the configuration: veno-venous (vv; ns11), venoarterial (va; ns8) or veno-venoarterial (vva; ns11). Data were prospectively collected and endpoint was 30-day mortality. To identify independent risk factors, univariate analysis was performed for clinical parameters, such as age, body mass index, gender, configuration, low-ph, oxygenation index (poyfio ) and underlying disease. Thirty-day mortality was 53% (ns16) for all comers: 63% (ns7) died in the vv-group, 75% (ns6) in the va-group and 7% (ns3) in the vva-group. Although univariate analysis could not rule out a significant predictor for the outcome, there was a trend visible to decreased mortality in the vva-group when compared to vv- and va-groups (7% vs. 63% vs. 75%; Ps0.057). ECMO provides a survival benefit in patients when considering a predicted mortality rate of 80% in ARDS. The configuration mode appears to impact the outcome as the veno-venoarterial appears to further improve the survival in this subset of patients. 011 Published by European Association for Cardio-Thoracic Surgery. All rights reserved. Keywords: Extracorporeal membrane oxygenation; Acute respiratory distress syndrome; Configuration mode 1. Introduction Extracorporeal membrane oxygenation (ECMO) provides circulatory and respiratory support in patients with acute cardiac and respiratory failure refractory to conventional treatment. Respiratory failure is usually caused by a severe acute respiratory distress syndrome (ARDS) due to different lung pathologies, such as pneumonia, sepsis, cystic fibrosis, chronic obstructive lung disease, lung graft failure, or due to trauma. Patients with respiratory-failure usually have a predicted mortality above 80% w1x. The Extracorporeal Life Support Organisation (ELSO; http:yywww.elso.med.umich.eduy) suggests that ECMO is indicated when the mortality risk reaches 80% which is given at a PaO : FiO-80 on FiO )90% and a Murray score of 3 4. Many centers define slow and fast entry criteria for instituting an ECMO wx with a regular re-evaluation of predefined parameters. 1 Both authors contributed equally. *Corresponding author. Department of Cardiovascular Surgery, University Hospital Zurich, Rämi Strasse 100, 8091 Zurich, Switzerland. Tel.: q41 44-55-398; fax: q41 44-55-4446. E-mail address: markus.wilhelm@usz.ch (M.J. Wilhelm). 011 Published by European Association for Cardio-Thoracic Surgery To date, the venovenous (vv) ECMO is the most commonly applied mode in patients with ARDS. However, if hemodynamic compromise occurs or oxygenation is not sufficient, an upgrade to venoarterial (va) or a veno-venoarterial (vva) ECMO might be necessary w3x. In this study we reviewed our experience in patients who received ECMO for ARDS with a specific focus on the different modes of cannulation.. Patients and methods From 006 to 008, 30 patients received ECMO for severe ARDS at our institution. The ECMO was implanted at the intensive care unit (ICU). Seventeen patients developed ARDS due to direct lung injury: eight patients suffered from pneumonia, four developed graft failure after lung transplantation and five had primary lung disease (two patients with idiopathic pulmonary fibrosis, two with cystic fibrosis, one with interstitial pneumopathy due to radiation). Indirect lung injuries included posttraumatic (ns) and postoperative ARDS (ns7) (one graft replacement of the descending aorta, one CABG, two aortic valve surgeries, one renovisceral rebranching, one resection of an oesophago tracheal fistula, one liver transplantation) as well as
F. Stöhr et al. / Interactive CardioVascular and Thoracic Surgery 1 (011) 676 680 677 Table 1. Patient characteristics Total (ns30) Survivors (ns14) Non-survivors (ns16) A. Demographics Age (years) 47."18.4 17 83 46.1"17 18 65 48.1"19.6 17 83 Maleyfemale (%) 60.0y40.0 43.5y56.5 68.8y30.4 Weight (kg) 67.4"10.5 44.5 100 66.9"15.0 48 100 68.0"16.8 44.5 98 Height (cm) 169.0"10.5 157 187 169."9.4 157 183 168.9"11.3 157 187 BMI (kgym ) 3.6"3.9 18 3.1 3.6"3.3 19 30.5 3.6"4.5 18 3.1 No. (%) No. (%) No. (%) B. Comorbidities COPD (6.7) 0 (1.5) Coronary disease 6 (0.0) 1 (7.1) 5 (31.3) Valvular heart disease (6.7) 0 (1.5) Arterial hypertension 5 (16.7) 3 (1.4) (1.5) PAD 1 (3.3) 0 1 (6.3) Chronic renal disease 8 (6.7) (14.3) 6 (37.5) MI in history 3 (10.0) 0 3 (18.8) CVI in history (6.7) 1 (7.1) 1 (6.3) C. Haemodynamics before ECMO MAP (mmhg) 68"11 35 84 69"10 50 84 65"11 35 8 HR (bpm) 100"5 6 13 99" 6 130 103"9 60 170 Hb (gydl) 9.9".9 6.8 17. 10.3"3.6 7.1 15.7 9.5".1 6.8 14.7 D. Arterial blood gas before ECMO po (kpa) 8.1".9 4.0 15.9 8.".9 4.7 15.9 8."3.1 4.0 16.6 pco (kpa) 9.0"3.9 3.0 16.6 8.7"3.8 4.3 16.7 8.4"5.0 3.0 18.7 poyfio (mmhg) 68"31 19 155 75"37 35 119 65"4 39 131 ph 7.19"0.7 6.90 7.51 7.6"0.09 7.1 7.41 7.13"0.0 6.90 7.51 BMI, body mass index; COPD, chronic obstructive lung disease; PAD, peripheral arterial disease; MI, myocardial infarction; CVI, cerebrovascular insult; MAP, mean arterial pressure; HR, heart rate; Hb, hemoglobin. Work in Editorial New Ideas Progress Report Protocol Institutional Report ESCVS Article Proposal for Bailout Procedure Negative Results Follow-up Paper ARDS due to sepsis (ns) and near drowning (ns1). In one patient, the ECMO was implanted preoperatively before resection of a carcinoma with tracheal necrosis. The baseline characteristics, underlying diseases, configuration modes and upgrades are summarized in Tables 1 3. Before considering patients for ECMO, conventional treatment for ARDS was applied including lung recruitment maneuvers, prone positioning and NO inhalation to minimize the intrapulmonary shunt. Patients who presented with a PaO :FiO-150 or a severe hypercapnea with a ph-7 despite conventional treatment were evaluated for ECMO. Patients were divided into three groups according to their configuration mode: initially, in 18 patients, ECMO was applied in venovenous fashion (ns18), nine were run in the venoarterial mode (ns9), and three were started in veno-venoarterial fashion (ns3) (Fig. 1). The initial configuration was chosen by the surgeon and intenvisit on duty. The configuration was then changed in 11 cases: eight patients were upgraded from veno-venous (ns5) or venoarterial (ns3) to veno-venoarterial ECMO and two patients were switched from vv to va (Tables and 3) resulting in the following groups: venovenous (vv; group A; ns11), venoarterial (va; group B; ns8) and veno-venoarterial (vva; group C; ns11). The most frequent cause for change of configuration was poor oxygenation (ns8), but also hemodynamic compromise (ns1) and insufficient venous drainage (ns). A change of the cannulation site was either necessary for modification of the ECMO configuration or due to hyperperfusion (ns1), hypoperfusion (ns1), insufficient venous drainage (ns) and high pressure in the ECMO circuit (ns1) (Table 3). A venoarterial ECMO was considered initially when the mean pulmonary arterial pressure was )35 mmhg. For venous cannulation, a percutaneous access was preferred via the common femoral veins andyor the internal jugular vein. If sufficient drainage was not achieved, a three-cannula technique was applied, draining blood both from the internal jugular and the femoral vein and returning oxygenated blood via a cannula in the contralateral femoral vein which was positioned in the right atrium. Another approach was to use both common femoral veins for drainage and the internal jugular vein for arterial return. For arterial cannulation, the subclavian or common femoral artery was used. An 8 mm graft (Vascutek, Inchinnan, Renfrewshire, UK) was anastomosed end-to-side to the artery, and a 0F cannula (FemFlex II; Edwards Lifesience, Irvine, CA, USA) was inserted in the graft. State-of-the-art Best Evidence Topic Nomenclature Historical Pages Brief Case Report Communication
678 F. Stöhr et al. / Interactive CardioVascular and Thoracic Surgery 1 (011) 676 680 Table. ECMO cannulation and configuration Total Survivors Non-survivors No. (%) No. (%) No. (%) Number of ECMOs 30 14 (47.0) 16 (53.0) Configuration at beginning v-v 18 9 10 v-a 9 (31.3) 5 5 v-v-a 3 (9.3) 1 Cannula sites Venous 60 3 8 V. femoralis 43 (77.6) 3 (71.9) 18 (71.4) V. jugularis 16 (6.7) 9 (8.1) 7 (5.0) V. subclavia 1 (1.7) 0 1 (3.6) Arterial 16 9 7 A. femoralis 5 (31.) (.) 3 (4.9) A. subclavia 11 (68.8) 6 (77.8) 4 (57.1) Change of cannulation site 13 8 5 Rationale Insufficient oxygenation 8 (61.5) 6 (75.0) (40.0) Hyperperfusion 1 (7.7) 1 (1.5) 0 Hypoperfusion 1 (7.7) 0 1 (0.0) Insufficient venous drainage (15.4) 1 (1.5) 1 (0.0) High pressure in ECMO circuit 1 (7.7) 0 1 (0.0) Change of configuration 11 8 3 Rationale Insufficient oxygenation 8 (7.7) 6 (75.0) (66.7) Haemodynamic instability 1 (9.1) 0 1 (33.3) Insufficient venous drainage (18.) (5.0) 0 Bridge to LTX 1 (3.1) 1 (6.3) 0 ECMO, extracorporeal membrane oxygenation; v-v, venovenous; v-a, venoarterial; v-v-a, veno-venoarterial; LTX, lung transplantation. The whole system including cannulae was coated with heparin and for priming, 1 l Ringerfundin (B. Braun, Melsungen, Germany) and 5000 IU heparin was used. Initially, the blood flow was set to 4 6 lymin depending on the patient s body surface area to achieve a 100 150% of calculated flow. In the vva-setting, the amount of arterial flow directed to the venous and arterial cannula was set such that the best possible oxygenation was achieved, usually at a rate of :3 (arterial:venous). The gas flow was set to 4 6 lymin with a FiO at 100% and the ventilator was set to a positive end-expiratory pressure (PEEP)-10 cm H O, peak inspiratory-pressure -6 cm H O, FiO -0.5, and a respiratory rate between 14 and 0. These settings were adjusted with regards to O -saturation accordingly. Gas exchange was measured by SaO, pao and paco. For anticoagulation, a bolus of 100 IUykg heparin was given before cannulation. Thereafter, the activated clotting time (ACT) was adjusted between 150 and 180. Coagulation was assessed by ACT, thrombin-time (TT), antithrombin III (AT- III) and platelet count. We also measured lactate dehydrogenase (LDH) and hematocrit (Hct) to indentify hemolysis. Both a low platelet count (-50,000yml) and a low Hct (-30%) were corrected by transfusions. For detection of Table 3. Switch of configuration Total (ns11) Survivors (ns8) Non-survivors (ns3) No. No. No. vv va 1 1 vv vva 5 3 va vva 3 3 0 Fig. 1. Configuration mode of ECMO. ECMO was either initiated in a venovenous (vv; 1q), veno-arterial (va; 1q3) or veno-venoarterial (vva; 1qq3) fashion. ECMO, extracorporeal membrane oxygenation. potential hyperperfusion and compartment syndrome, peripheral-pulses and limb circumferences were measured, and both creatinine kinase (CK) and lactate levels were determined. The gas flow into the ECMO circuit and the FiO on the oxygenator were reduced by steps of 0.5 lymin over a period of 1 4 h, to wean a patient from a venovenous ECMO while carefully measuring the po, pco and the ph. Before ECMO explantation, the gas flow with FiO 35% had to be - lymin while sufficient blood gases were present. For weaning a venoarterial or veno-venoarterial ECMO, blood flow rates were decreased by 0.5 lymin over periods of 1 4 h while monitoring hemodynamic parameters (blood pressure, central venous pressure, pulmonary pressures, cardiac index, SvO ). When a flow of 1.5 lymin over 1 h was reached with stable hemodynamics, explantation was performed..1. Statistical analysis All data for this retrospective study were prospectively collected. Primary outcome measure was 30-day mortality. Univariate analysis was applied to identify clinical parameters associated with mortality. Discrete variables were compared using Fisher exact test and continuous variables were analyzed using a Mann Whitney U-test. The survival was analyzed using Kaplan Meier curves. Statistical significance was assumed when P-value-0.05. 3. Results Of the whole cohort, 16 patients died within 30 days after ECMO implantation (53%) of which 15 patients expired while being on ECMO, and one patient seven days after ECMO explantation. In detail, 7% (ns3) died in the vva-group (group C; ns11; including three patients from the beginning and eight patients upgraded), 63% (ns7) died in the vv-group (group A; ns11) and 75% (ns6) died in the vagroup (group B; ns8). Although univariate analysis did not rule out a significant predictor for the outcome wage; Ps0.934ybody mass index; Ps0.71ygender; Ps0.457ylow ph; Ps0.19ylow oxygenation index (poyfio ); Ps0.75yunderlying disease; Ps0.685x, patients who received a veno-venoarterial ECMO
F. Stöhr et al. / Interactive CardioVascular and Thoracic Surgery 1 (011) 676 680 679 Fig.. Configuration-related mortality. The patients who received a venovenoyarterial ECMO displayed a decreased mortality when compared to patients on venovenous or venoarterial mode (7% vs. 63% vs. 75%; Ps0.057). ECMO, extracorporeal membrane oxygenation. displayed a decreased mortality when compared to patients on veno-venous or veno-arterial mode (7% vs. 63% vs. 75%; Ps0.057) (Fig. ). Causes of death were multiorgan-failure (MOF) in 13 patients: six patients due to sepsis, one due DIC, and six due to undefined reasons. The mean time of ECMO was 7.53"7.1 days. The median length of hospital stay was 36.5 days. The median length of ICU stay was 1.5 days. Bleeding was the most frequent complication (7%) (Table 4). In vv-ecmo, bleeding occurred in one patient, whereas in an arterial cannulation-site, bleeding was found in seven cases (ns7). One patient developed a hyperperfusion syndrome while the subclavian artery was cannulated. One patient had a hypoperfusion syndrome of the leg. Both the vena and arteria femoralis were cannulated for va-ecmo. After hypoperfusion was diagnosed an additional cannula for distal perfusion was placed in the femoral artery. Mean follow-up time was 1.1 months. During the followup period three patients died: one due to cardiogenicshock, one due to acute pulmonary-edema two years after lung transplantation and one due to ischemic brain-injury. 4. Discussion ARDS is still associated with a high mortality-rate varying from 15 to 7% depending on the study w4x. A decrease of mortality from ARDS, as seen by some authors over the last decade w4, 5x, is discussed controversially in the literature w6x. The wide variation of mortality rates which are reported may be due to the fact that patients meeting current American European Consensus Conference ARDS criteria may have highly variable levels of lung-injury and outcomes w7x. Table 4. Complications Total Survivors Non-survivors Total 11 8 3 Bleeding 8 6 Hyperperfusion 1 1 0 Hypoperfusion 1 0 1 Wound healing complications 1 1 0 Considering a predicted mortality rate of 80% according to ELSO, our study shows that ECMO therapy in general provides a survival benefit in our patients by reducing the 30-day mortality rate down to 53.3%. These findings are in line with other reports suggesting mortality rates ranging between 46% and 50% w3, 8, 9x. Furthermore, our results demonstrate that the configuration mode of ECMO may have an impact on the outcome as the applied venovenoarterial mode seems to further improve the survival in this subset of patients. However, although the mortality in the veno-venoarterial subgroup was found to be much lower than in the total cohort (7% vs. 53.3%), statistical analysis only revealed a trend to a reduction in mortality, which, however, was close to significance. This is, at least, remarkable, taking into account the small numbers of patients. It reflects our positive clinical experience with the veno-venoarterial mode in our study cohort. Since this configuration is currently favored as initial ECMO mode in our center, we will be able to see in the near future if and to which extent it may provide a survival benefit. So far, according to our knowledge, there are no reports in the literature which focus on survival depending on different modes of configuration. We can only speculate why the veno-venoarterial configuration may provide a survival benefit. With this mode, well-oxygenated blood is provided to the systemic and pulmonary circulation. In the pulmonary circulation, it helps reduce the pulmonary resistance and the existence of intrapulmonary-shunts, which might facilitate pulmonary recovery. In the systemic circulation, it takes care for sufficient oxygen supply to the brain, the coronary circulation and all peripheral organs which might prevent multiorgan dysfunction and adds to hemodynamic stability. Our statistical analysis did not identify independent predictors of outcome. In contrast, other studies found parameters, such as length of mechanical ventilation, ph-value and paoyfio ratio before ECMO implantation as well as age and gender as predictors for outcome w3, 8x. This might be explained by the different size of cohorts. We have reviewed only 30 patients over a period of three years, while the other studies comprise 100 and 55 patients collected over a period of 6.5 and 15 years. Although bleeding complications were much more frequent in patients with arterial cannulation, this did not affect 30-day mortality. Other investigators identified significant surgical site bleeding as patient-related complications associated with outcome w3x. The bleeding rate of 7% in our study is comparable to that reported by others w10, 11x. Bleeding was mainly located at the arterial cannulation sites. With increasing experience, however, we have noted a decreasing frequency of such complications over the study period. In any case, the bleeding rate has declined as compared to earlier years w1x since heparincoated ECMO systems and cannulae require much less anticoagulation. There are several limitations of this study. The patient cohort was small, heterogeneous and due to its retrospective nature, all established disadvantages apply. No algorithm for choosing an ECMO configuration existed when we started the ECMO program. The choice of ECMO configura- Work in Editorial New Ideas Progress Report Protocol Institutional Report ESCVS Article Proposal for Bailout Procedure Negative Results Follow-up Paper State-of-the-art Best Evidence Topic Nomenclature Historical Pages Brief Case Report Communication
680 F. Stöhr et al. / Interactive CardioVascular and Thoracic Surgery 1 (011) 676 680 tion may have been influenced by the preferences of the surgeon and intensive care specialist on duty. As the patients were not randomized, there might be a certain selection bias. The survival is poor as compared to other surgical therapies in medicine. However, increasing experience with this therapy will improve the results and justify the economic costs. ECMO therapy provides a survival benefit in patients when considering a predicted mortality-rate of 80% in ARDS. The configuration mode of ECMO may impact the outcome as the veno-venoarterial mode appears to further improve the survival in this subset of patients. References w1x Vasilyev S, Schaap RN, Mortensen JD. Hospital survival rates of patients with acute respiratory failure in modern respiratory intensive care units. An international, multicenter, prospective survey. Chest 1995; 107:1083 1088. wx Lewandowski K. Extracorporeal membrane oxygenation for severe acute respiratory failure. Crit Care 000;4:156 168. w3x Kolla S, Awad SS, Rich PB, Schreiner RJ, Hirschl RB, Bartlett RH. Extracorporeal life support for 100 adult patients with severe respiratory failure. Ann Surg 1997;6:544 564; discussion 565 566. w4x Zambon M, Vincent JL. Mortality rates for patients with acute lung injuryyards have decreased over time. Chest 008;133:110 117. w5x Erickson SE, Martin GS, Davis JL, Matthay MA, Eisner MD. Recent trends in acute lung injury mortality: 1996 005. Crit Care Med 009;37:1574 1579. w6x Phua J, Badia JR, Adhikari NK, Friedrich JO, Fowler RA, Singh JM, Scales DC, Stather DR, Li A, Jones A, Gattas DJ, Hallett D, Tomlinson G, Stewart TE, Ferguson ND. Has mortality from acute respiratory distress syndrome decreased over time?: a systematic review. Am J Respir Crit Care Med 009;179:0 7. w7x Villar J, Perez-Mendez L, Lopez J, Belda J, Blanco J, Saralegui I, Suarez- Sipmann F, Lubillo S, Kacmarek RM. An early PEEPyFIO trial identifies different degrees of lung injury in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 007;176:795 804. w8x Hemmila MR, Rowe SA, Boules TN, Miskulin J, McGillicuddy JW, Schuerer DJ, Haft JW, Swaniker F, Arbabi S, Hirschl RB, Bartlett RH. Extracorporeal life support for severe acute respiratory distress syndrome in adults. Ann Surg 004;40:595 605; discussion 605 607. w9x Brogan TV, Thiagarajan RR, Rycus PT, Bartlett RH, Bratton SL. Extracorporeal membrane oxygenation in adults with severe respiratory failure: a multi-center database. Intensive Care Med 009;35:105 114. w10x Brown JK, Haft JW, Bartlett RH, Hirschl RB. Acute lung injury and acute respiratory distress syndrome: extracorporeal life support and liquid ventilation for severe acute respiratory distress syndrome in adults. Semin Respir Crit Care Med 006;7:416 45. w11x Meyer A, Struber M, Fischer S. Advances in extracorporeal ventilation. Anesthesiol Clin 008;6:381 391, viii. w1x Egan TM, Duffin J, Glynn MF, Todd TR, DeMajo W, Murphy E, Fox L, Cooper JD. Ten-year experience with extracorporeal membrane oxygenation for severe respiratory failure. Chest 1988;94:681 687.