Hemolysis During Pediatric Extracorporeal Membrane Oxygenation: Associations With Circuitry, Complications, and Mortality

Transcription

1 Hemolysis During Peditric Extrcorporel Membrne Oxygention: Associtions With Circuitry, Complictions, nd Mortlity Heidi J. Dlton, MD 1 ; Ktherine Cshen, DO 2 ; Ron W. Reeder, PhD 3 ; Robert A. Berg, MD 4 ; Thoms P. Shnley, MD 5 ; Christopher J. L. Newth, MD 6 ; Murry M. Pollck, MD 7 ; Dvid Wessel, MD 7 ; Joseph Crcillo, MD 8 ; Rick Hrrison, MD 9 ; J. Michel Den, MD 2 ; Kthleen L. Meert, MD 2 ; for the Eunice Kennedy Shriver Ntionl Institute of Child Helth nd Humn Development Collbortive Peditric Criticl Cre Reserch Network (CPCCRN) 1 Deprtment of Peditrics, Inov Firfx Hospitl, Flls Church, VA. 2 Division of Criticl Cre, Deprtment of Peditrics, Children s Hospitl of Michign/Wyne Stte University, Detroit, MI. 3 Deprtment of Peditrics, University of Uth, Slt Lke City, UT. 4 Deprtment of Anesthesiology nd Criticl Cre, Children s Hospitl of Phildelphi, Phildelphi, PA. 5 Deprtment of Peditrics, Ann & Robert H. Lurie Children s Hospitl of Chicgo/Northwestern University Feinberg School of Medicine, Chicgo, IL. 6 Deprtment of Anesthesiology nd Criticl Cre Medicine, Children s Hospitl Los Angeles, Los Angeles, CA. 7 Deprtment of Peditrics, Children s Ntionl Medicl Center, Wshington, DC. 8 Deprtment of Criticl Cre Medicine, Children s Hospitl of Pittsburgh, Pittsburgh, PA. 9 Deprtment of Peditrics, Mttel Children s Hospitl UCLA, Los Angeles, CA. Supplementl digitl content is vilble for this rticle. Direct URL cittions pper in the printed text nd re provided in the HTML nd PDF versions of this rticle on the journl s website ( Supported, in prt, by the following coopertive greements from the Eunice Kennedy Shriver Ntionl Institute of Child Helth nd Humn Development, Ntionl Institutes of Helth, Deprtment of Helth nd Humn Services: U10HD050096, U10HD049981, U10HD049983, U10HD050012, U10HD063108, U10HD063106, U10HD063114, nd U01HD The content is solely the responsibility of the uthors nd does not necessrily represent the officil views of the Ntionl Institutes of Helth. Drs. Dlton s, Reeder s, Berg s, Shnley s, Wessel s, Hrrison s, Den s, nd Meert s institutions received funding from the Ntionl Institutes of Helth (NIH). Drs. Dlton, Reeder, Berg, Shnley, Newth, Pollck, Wessel, Crcillo, Hrrison, Den, nd Meert received support for rticle reserch from the NIH. Dr. Dlton received funding from Innovtive Extrcorporel membrne oxygention (ECMO) Concepts nd Mquet spekers bureu, nd she disclosed off-lbel product use of ECMO equipment. Dr. Shnley received funding from Springer Publishing, Peditric Acdemic Societies Operting nd Executive Committees, nd Interntionl Peditric Reserch Fund. Dr. Newth received funding from Philips Reserch North Americn (consulting services for dt nlysis). Dr. Crcillo s institution received funding from the Ntionl Institute of Child Helth nd Humn Development Collbortive Peditric Criticl Cre Reserch Network U10. Dr. Cshen hs disclosed tht she does not hve ny potentil conflicts of interest. For informtion regrding this rticle, E-mil: kmeert@med.wyne.edu Copyright 2018 by the Society of Criticl Cre Medicine nd the World Federtion of Peditric Intensive nd Criticl Cre Societies DOI: /PCC Objectives: To describe fctors ssocited with hemolysis during peditric extrcorporel membrne oxygention nd the reltionships between hemolysis, complictions, nd mortlity. Design: Secondry nlysis of dt collected prospectively by the Collbortive Peditric Criticl Cre Reserch Network between December 2012 nd September Setting: Three Collbortive Peditric Criticl Cre Reserch Network-ffilited hospitls. Ptients: Age less thn 19 yers nd treted with extrcorporel membrne oxygention. Interventions: None. Mesurements nd Min Results: Hemolysis ws defined bsed on pek plsm free hemoglobin levels during extrcorporel membrne oxygention nd ctegorized s none (< g/l), mild (0.001 to < 0.5 g/l), moderte (0.5 to < 1.0 g/l), or severe ( 1.0 g/l). Of 216 ptients, four (1.9%) hd no hemolysis, 67 (31.0%) hd mild, 51 (23.6%) hd moderte, nd 94 (43.5%) hd severe. On multivrible nlysis, vribles independently ssocited with higher dily plsm free hemoglobin concentrtion included the use of in-line hemofiltrtion or other continuous renl replcement therpy, higher hemoglobin concentrtion, higher totl bilirubin concentrtion, lower men heprin infusion dose, lower body weight, nd lower pltelet count. Using multivrible Cox modeling, dily plsm free hemoglobin ws independently ssocited with development of renl filure during extrcorporel membrne oxygention (defined s cretinine > 2 mg/dl [> μmol/l] or use of in-line hemofiltrtion or continuous renl replcement therpy) (hzrd rtio, 1.04; 95% CI, ; p < 0.001), but not mortlity (hzrd rtio, 1.01; 95% CI, ; p = 0.389). Conclusions: Hemolysis is common during peditric extrcorporel membrne oxygention. Hemolysis my contribute to the development of renl filure, nd therpies used to mnge renl filure such s in-line hemofiltrtion nd other forms of continuous renl replcement therpy my contribute to hemolysis. Hemolysis ws not ssocited with mortlity fter controlling for Peditric Criticl Cre Medicine

2 Dlton et l other fctors. Monitoring for hemolysis should be routine prt of extrcorporel membrne oxygention prctice, nd efforts to reduce hemolysis my improve ptient cre. (Peditr Crit Cre Med 2018; 19: ) Key Words: child; extrcorporel membrne oxygention; hemolysis; neonte; plsm free hemoglobin Extrcorporel membrne oxygention (ECMO) is n invsive tretment modlity used for ptients with respirtory nd crdic filure refrctory to mximl medicl therpy. Despite technologic dvnces, hemosttic complictions remin common during peditric ECMO (1). Hemolysis, the lysis of RBCs nd subsequent relese of hemoglobin into the plsm, remins mjor problem (1 5). Hemolysis is mesured by elevted plsm free hemoglobin (PFH) concentrtion. Hemolysis occurs due to mechnicl trum nd complement ctivtion during ECMO (6 9). The frequency of hemolysis is likely underrecognized nd underreported becuse PFH is not routinely mesured t mny centers (10). In the Collbortive Peditric Criticl Cre Reserch Network (CPCCRN) Bleeding nd Thrombosis during ECMO (BATE) study, 32.9% of the entire cohort hd hemolysis, nd t sites where PFH ws routinely mesured, 57.5% hd hemolysis (1). Free hemoglobin in the plsm is cytotoxic, cuses endothelil dysfunction, nd consumes nitric oxide leding to vsoconstriction (9, 11). Hemolysis during ECMO hs been ssocited with renl injury, need for renl replcement therpy, thrombotic events, need for circuit component chnge, nd mortlity (1, 5, 8, 9). Risk fctors for hemolysis re likely multifctoril but reports delineting these fctors hve been inconsistent. Concerns hve been rised bout pump-relted fctors (oxygentor type, venous inlet pressure, pump speed, cvittion, priming solution) (5, 8, 9, 11 14) nd ptient-relted fctors (high hemoglobin) (15, 16). Most reports of hemolysis during peditric ECMO re in vitro lbortory simultions, retrospective single-center udits, or bsed on Extrcorporel Life Support Orgniztion (ELSO) registry dt. Prospective, multicenter dt re needed to gin more ccurte nd generlizble knowledge. The objectives of this study were to describe fctors ssocited with hemolysis during peditric ECMO nd the reltionships between hemolysis, complictions, nd mortlity. METHODS Design nd Setting The study ws secondry nlysis of dt from the BATE study (1) which described the frequency of bleeding nd thrombosis in neontl nd peditric ECMO ptients. The BATE study collected prospective observtionl dt t eight CPCCRN-ffilited hospitls between December 2012 nd September Of these eight sites, only three routinely mesured PFH during ECMO on t lest 80% of study dys; therefore, only these three sites were included in this nlysis. The Institutionl Review Bords for ech hospitl nd the Dt Coordinting Center t the University of Uth pproved the study with wiver of prentl permission. Study Subjects All ptients less thn 19 yers old treted with ECMO in neontl, peditric, or crdic ICU were included in the BATE study (n = 514) (1). Only the initil ECMO course ws included for ptients who required multiple courses of ECMO. The three sites contributing dt to this nlysis recruited 218 ptients. Two of these ptients hd no PFH mesurements nd were excluded, leving 216 ptients. Dt Collection Reserch coordintors collected dt dily vi direct observtion, discussion with bedside clinicins, nd review of medicl records. Pre-ECMO dt included demogrphics; body weight; history of premturity; cute nd chronic dignoses; occurrence of n opertive procedure or crdiopulmonry bypss (CPB) in the 24 hours prior to ECMO initition; primry indiction for ECMO; plcement on ECMO directly from CPB or vi n ex utero intrprtum tretment procedure; nd clinicl site. Demogrphics included ge t ECMO initition, sex, rce, nd ethnicity. Age ws ctegorized s neonte less thn or equl to 30 dys, infnt greter thn 30 dys to less thn or equl to 12 months, child greter thn 1 yer to less thn or equl to 12 yers, nd dolescent greter thn 12 yers to less thn 19 yers. Premturity ws less thn 37 weeks gesttionl ge t birth nd collected for neontes only. Primry indiction for ECMO ws ctegorized s respirtory, crdic, or extrcorporel crdiopulmonry resuscittion (ECPR). ECMO setup nd mngement dt included mode of ECMO; type of pump; use of venous reservoir; circuit or oxygentor biocomptibility coting; circuit priming method; heprin bolus dose for cnnultion; totl dily heprin dose; ECMO flow rtes; use of therpeutic hypothermi; trnsfusion volumes; use of plsmpheresis; use of in-line hemofiltrtion or other continuous renl replcement therpy (CRRT); nd loction of ECMO within the hospitl. Mode of ECMO ws ctegorized s venorteril or venovenous. Venovenous ECMO tht ws converted to venorteril ws ctegorized s venorteril ECMO. Type of pump ws ctegorized s roller hed or centrifugl. Circuit priming method ws ctegorized s blood or nonblood (cler) prime. ECMO flow rte nd core body temperture were collected dily t 7 m. Becuse the use of therpeutic hypothermi ws not recorded in the BATE study, therpeutic hypothermi ws defined s core body temperture less thn or equl to 34 C for two consecutive dys during the first 3 dys of ECMO (17). Trnsfusion volumes included dily volumes of RBCs, pltelets, nd fresh frozen plsm dministered. Loction of ECMO ws neontl, peditric, or crdic ICU. Lbortory dt included rteril blood gses, complete blood count, blood ure nitrogen, cretinine, totl bilirubin, lctte, prothrombin time, prtil thromboplstin time, interntionl November 2018 Volume 19 Number 11

3 Extrcorporel Support normliztion rtio (INR), fibrinogen, ctivting clotting time, ntithrombin III, ntifctor X, nd PFH. Bseline lbortory vlues were obtined closest nd prior to ECMO initition; dily lbortory vlues were obtined closest to 7 m on ech ECMO dy. Hemolysis ws defined bsed on pek PFH levels nd ctegorized s none (< g/l), mild (0.001 to < 0.5 g/l), moderte (0.5 to < 1.0 g/l), or severe ( 1.0 g/l). Outcomes included complictions during ECMO; durtion of ECMO, ICU, nd hospitl sty; nd inhospitl mortlity. Complictions included bleeding events, thrombotic events, neurologic events, heptic dysfunction, renl filure, nd new infection. Bleeding events were defined s blood loss requiring trnsfusion or intrcrnil hemorrhge. Thrombotic events included intrcrnil infrction, limb ischemi, pulmonry embolus, intrcrdic thrombus, ortopulmonry shunt thrombus, other sites of thrombosis, nd circuit thrombosis requiring replcement of circuit component. Neurologic events included seizures, intrcrnil hemorrhge or infrction, nd brin deth. Heptic dysfunction ws defined s n INR greter thn 2. Renl filure ws defined s cretinine greter thn 2 mg/dl (> μmol/l) or use of in-line hemofiltrtion or other form of CRRT. New infection ws defined s new culture- or polymerse chin rection-proven infection dignosed fter ECMO initition. Sttisticl Anlysis Demogrphics, pre-ecmo sttus, ECMO system setup nd mngement, nd outcome vribles were summrized by pek level of hemolysis (Tbles 1 4). Counts nd percentges re reported for ctegoricl vribles wheres the medin nd interqurtile rnge re reported for continuous vribles. Percentges re bsed on row totls. p vlues for the ssocitions of vribles with pek hemolysis level were bsed on sttisticl tests tht tke dvntge of the ordered nture of the pek hemolysis ctegories. The Cochrn-Armitge trend test ws used for binry vribles, the Kruskl-Wllis test for nominl vribles with more thn two levels, nd the Jonckheere- Terpstr test for continuous vribles. Multivrible models for dily PFH, renl filure, nd mortlity on ECMO re presented in Tbles 5 7. A multivrible model ws developed for ech of these three outcomes independently. Multivrible model selection ws done in two steps. First, univrible models were creted for ech cndidte predictor. Vribles were considered potentil predictors TABLE 1. Demogrphics by Pek Level of Hemolysis Pek Hemolysis Vribles None (n = 4) Mild (n = 67) Moderte (n = 51) Severe (n = 94) p Age, n (%) < b Preterm neonte 0 (0.0) 8 (27.6) 3 (10.3) 18 (62.1) Full-term neonte 0 (0.0) 14 (17.3) 25 (30.9) 42 (51.9) Infnt 1 (1.8) 19 (33.3) 14 (24.6) 23 (40.4) Child 3 (10.3) 14 (48.3) 6 (20.7) 6 (20.7) Adolescent 0 (0.0) 12 (60.0) 3 (15.0) 5 (25.0) Mle, n (%) 3 (2.4) 36 (28.8) 26 (20.8) 60 (48.0) c Rce, n (%) d Asin 0 (0.0) 0 (0.0) 3 (23.1) 10 (76.9) Blck or Africn Americn 2 (4.5) 18 (40.9) 11 (25.0) 13 (29.5) White 2 (1.9) 32 (30.5) 21 (20.0) 50 (47.6) Unknown or not reported 0 (0.0) 17 (31.5) 16 (29.6) 21 (38.9) Ethnicity d Hispnic or Ltino, n (%) 1 (2.6) 13 (33.3) 11 (28.2) 14 (35.9) Not Hispnic or Ltino, n (%) 3 (2.4) 38 (30.9) 30 (24.4) 52 (42.3) Unknown or not reported, n (%) 0 (0.0) 16 (29.6) 10 (18.5) 28 (51.9) Weight (kg), medin (IQR) 13.2 ( ) 6.7 ( ) 3.7 ( ) 3.2 ( ) < b IQR = interqurtile rnge. Vribles reported hd no missing vlues. b Jonckheere-Terpstr test. c Cochrn-Armitge trend test. d Kruskl-Wllis test. Peditric Criticl Cre Medicine

4 Dlton et l TABLE 2. Preextrcorporel Membrne Oxygention Sttus by Pek Level of Hemolysis Pek Hemolysis Vribles, b None (n = 4) Mild (n = 67) Moderte (n = 51) Severe (n = 94) p Primry ECMO indiction, n (%) c Respirtory 1 (1.0) 34 (34.3) 16 (16.2) 48 (48.5) Crdic 2 (2.2) 24 (25.8) 33 (35.5) 34 (36.6) Extrcorporel crdiopulmonry resuscittion 1 (4.2) 9 (37.5) 2 (8.3) 12 (50.0) Meconium spirtion syndrome, n (%) 0 (0.0) 3 (17.6) 4 (23.5) 10 (58.8) d Congenitl diphrgmtic herni, n (%) 0 (0.0) 2 (9.1) 1 (4.5) 19 (86.4) < d Persistent pulmonry hypertension of the newborn, n (%) Opertive procedure in the 24 hr prior to ECMO initition, n (%) 0 (0.0) 3 (10.0) 10 (33.3) 17 (56.7) d 1 (1.2) 30 (34.9) 27 (31.4) 28 (32.6) d CPB in the 24 hr prior to ECMO, n (%) 1 (1.4) 21 (30.4) 24 (34.8) 23 (33.3) d Plced on ECMO directly from CPB, n (%) 0 (0.0) 6 (17.6) 12 (35.3) 16 (47.1) d Plced on ECMO vi ex utero intrprtum tretment procedure, n (%) 0 (0.0) 1 (100.0) 0 (0.0) 0 (0.0) d Bseline ph in rteril blood, medin (IQR) 7.3 ( ) 7.3 ( ) 7.3 ( ) 7.3 ( ) e Bseline lctte (mmol/l), medin (IQR) 3.6 ( ) 4.0 ( ) 3.0 ( ) 5.4 ( ) e Bseline cretinine (mg/dl), medin (IQR) 0.6 ( ) 0.6 ( ) 0.7 ( ) 0.5 ( ) e Bseline cretinine, (μmol/l), medin (IQR) 53 (26 62) 53 (44 88) 62 (44 79) 44 (35 71) Bseline blood ure nitrogen (mg/dl), medin (IQR) 28 (7 30) 15 (10 24) 18 (13 23) 17 (9 26) e Bseline blood ure nitrogen (mmol/l), medin (IQR) 10.0 ( ) 5.3 ( ) 6.4 ( ) 6.0 ( ) CPB = crdiopulmonry bypss, ECMO = extrcorporel membrne oxygention, IQR = interqurtile rnge. Percentges reported re bsed on row totls. b ph, blood ure nitrogen, cretinine, nd lctte hd missingness rtes of 13%, 19%, 19%, nd 17%, respectively; other vribles hd no missing vlues. c Kruskl-Wllis test. d Cochrn-Armitge trend test. e Jonckheere-Terpstr test. if they were ssocited with the outcome being modeled in univrible nlysis (p < 0.10) nd vilble for t lest 90% of the study dys (Supplementl Tble 1, Supplementl Digitl Content 1, Supplementl Tble 2, Supplementl Digitl Content 2, PCC/A743; nd Supplementl Tble 3, Supplementl Digitl Content 3, Second, the finl model for ech outcome ws selected using bidirectionl stepwise selection on the potentil predictors with significnce criterion of p vlue of less thn 0.05 to enter nd sty in the finl model. PFH ws forced into the finl multivrible models of renl filure nd mortlity on ECMO, but no vribles were forced into the finl multivrible model of dily PFH. Dily PFH ws modeled with liner regression using the identity link function, Gussin errors, nd robust error estimtes (Tble 5). In order to ccount for the temporlity of predictor vribles with PFH, PFH ws considered s dily outcome nd ws modeled bsed on ptient fctors nd sttus on tht dy. For exmple, we demonstrted tht PFH ws 16.3 mg/dl higher on dys when hemofiltrtion or CRRT ws used. An utoregressive covrince structure of order 1 ws specified to ccount for correltion between PFH on different study dys from the sme subject. In prticulr, this ccounts for higher correltion between PFH mesurements on study dys tht re temporlly close together but reltively lower correltion between PFH mesurements on study dys tht re fr prt. Mortlity nd renl filure modeling lso incorported the temporlity of predictor vribles by using timevrying covrites in the Cox models. This llows the models to ccount for mortlity nd renl filure hzrds tht chnge from dy to dy corresponding with chnges in the predictor vribles (Tbles 6 nd 7). Dily dt collection ws discontinued fter decnnultion, which leds to censoring in the model of mortlity. In prticulr, deths occurring fter the clendr dy of decnnultion re not considered by this model. All reported p vlues were bsed on two-sided lterntives nd considered sttisticlly significnt if less thn Anlyses were performed using SAS 9.4 (SAS Institute, Cry, NC) November 2018 Volume 19 Number 11

5 Extrcorporel Support TABLE 3. Extrcorporel Membrne Oxygention System Setup nd Mngement by Pek Level of Hemolysis Pek Hemolysis Vribles None (n = 4) Mild (n = 67) Moderte (n = 51) Severe (n = 94) p ECMO system setup Mode of ECMO, n (%) b Venorteril 3 (1.6) 56 (29.9) 50 (26.7) 78 (41.7) Venovenous 1 (3.4) 11 (37.9) 1 (3.4) 16 (55.2) Type of pump, n (%) b Roller hed 0 (0.0) 0 (0.0) 7 (46.7) 8 (53.3) Centrifugl 4 (2.0) 67 (33.3) 44 (21.9) 86 (42.8) Setup includes bldder/venous reservoir, n (%) 4 (2.9) 39 (27.9) 31 (22.1) 66 (47.1) b Oxygentor biocomptibility coting, n (%) 4 (1.9) 64 (30.8) 49 (23.6) 91 (43.8) b Circuit tubing biocomptibility coting, n (%) 4 (3.2) 33 (26.8) 28 (22.8) 58 (47.1) b Method for priming the circuit b Nonblood (cler), n (%) 1 (5.6) 10 (55.6) 3 (16.7) 4 (22.2) Blood, n (%) 3 (1.5) 57 (28.8) 48 (24.2) 90 (45.5) Heprin bolus for cnnultion, n (%) 4 (2.2) 61 (33.3) 39 (21.3) 79 (43.2) b Heprin bolus dose (IU/kg) c, medin (IQR) 50.0 ( ) ECMO mngement e ( ) 75.0 ( ) 89.0 ( ) d Plsmpheresis, n (%) 0 (0.0) 4 (21.1) 5 (26.3) 10 (52.6) b In-line hemofiltrtion, n (%) 1 (1.5) 7 (10.8) 17 (26.2) 40 (61.5) < b Continuous renl replcement therpy, n (%) 0 (0.0) 10 (15.9) 16 (25.4) 37 (58.7) < b Therpeutic hypothermi, n (%) 0 (0.0) 3 (30.0) 2 (20.0) 5 (50.0) b Men dily ECMO flow rte (ml/kg/min), medin (IQR) Men dily RBC trnsfusion (ml/kg), medin (IQR) Men dily heprin dose (U/kg/min), medin (IQR) Men dily pltelet trnsfusion (ml/kg), medin (IQR) Men dily plsm trnsfusion (ml/kg), medin (IQR) 62.3 ( ) 12.9 ( ) ECMO = extrcorporel membrne oxygention, IQR = interqurtile rnge. Vribles reported hd no missing vlues. b Cochrn-Armitge trend test. c Heprin bolus dose (IU/kg) is summrized only for those who receive heprin. d Jonckheere-Terpstr test. e A limittion is tht the timing of intervention in reltion to hemolysis is not considered ( ) 27.3 ( ) 93.3 ( ) 35.5 ( ) ( ) 35.8 ( ) < d d 0.4 ( ) 0.3 ( ) 0.3 ( ) 0.4 ( ) < d 3.1 ( ) 8.7 ( ) 16.2 ( ) 19.8 ( ) < d 6.4 ( ) 5.3 ( ) 8.7 ( ) 8.8 ( ) d RESULTS Of 216 ptients, four (1.9%) hd no hemolysis, 67 (31.0%) hd mild, 51 (23.6%) hd moderte, nd 94 (43.5%) hd severe hemolysis during ECMO. Neontl ge group, Asin rce, nd lower body weight were ssocited with incresed pek level of hemolysis (Tble 1). Congenitl diphrgmtic herni nd persistent pulmonry hypertension of the newborn were lso ssocited with incresed pek level of hemolysis (Tble 2). Peditric Criticl Cre Medicine

6 Dlton et l TABLE 4. Complictions nd Outcomes by Pek Level of Hemolysis Pek Hemolysis Vribles, b None (n = 4) Mild (n = 67) Moderte (n = 51) Severe (n = 94) p Thrombocytopeni, n (%) 0 (0.0) 21 (25.6) 21 (25.6) 40 (48.8) c New documented infection, n (%) 1 (1.7) 17 (29.3) 14 (24.1) 26 (44.8) c Bleeding event, n (%) 3 (1.7) 47 (26.9) 42 (24.0) 83 (47.4) c Thrombotic event, n (%) 0 (0.0) 19 (17.9) 28 (26.4) 59 (55.7) < c Neurologic orgn filure, n (%) 1 (1.4) 15 (20.5) 17 (23.3) 40 (54.8) c Renl orgn filure, n (%) 1 (1.1) 13 (14.0) 22 (23.7) 57 (61.3) < c Heptic orgn filure, n (%) 1 (1.2) 20 (23.3) 21 (24.4) 44 (51.2) c Durtion of extrcorporel membrne oxygention (d), medin (IQR) Length of ICU sty (d), medin (IQR) 33.3 ( ) Length of hospitl sty (d), medin (IQR) 40.7 ( ) 4.3 ( ) 3.7 ( ) 5.4 ( ) 8.6 ( ) < d 29.6 ( ) 46.1 ( ) 29.9 ( ) 41.6 ( ) 29.4 ( ) 36.4 ( ) d d Inhospitl mortlity, n (%) 1 (1.0) 24 (23.3) 26 (25.2) 52 (50.5) c IQR = interqurtile rnge. Vribles reported hd no missing vlues. b A limittion in this tble is tht the timing of some outcomes reltive to hemolysis is not considered. c Cochrn-Armitge trend test. d Jonckheere-Terpstr test. Regrding ECMO system setup, use of roller hed pump nd blood circuit prime ws ssocited with incresed pek level of hemolysis (Tble 3). Regrding ECMO mngement, use of inline hemofiltrtion or other form of CRRT, higher men dily ECMO flow rte, higher men dily heprin dose, nd higher men dily RBC, pltelet, nd plsm trnsfusion volumes were ssocited with incresed pek level of hemolysis (Tble 3). Complictions nd outcomes by pek level of hemolysis re shown in Tble 4. Bleeding events, thrombotic events, neurologic events, heptic dysfunction, nd renl filure were ssocited with incresed pek level of hemolysis. Longer durtion of ECMO nd inhospitl mortlity were lso ssocited with incresed pek level of hemolysis. Univrible ssocitions with dily PFH during ECMO re shown in Supplementl Tble 1 (Supplementl Digitl Content 1, On multivrible nlysis, vribles independently ssocited with higher dily PFH (Tble 5) included the use of in-line hemofiltrtion or CRRT, higher hemoglobin, higher totl bilirubin, lower heprin infusion dose, lower body weight, lower pltelet count, presence of n cute neurologic condition, nd bsence of cute nonseptic shock, chronic immune dysfunction, nd chronic neurologic conditions. Univrible Cox models of renl filure re shown in Supplementl Tble 2 (Supplementl Digitl Content 2, links.lww.com/pcc/a743). On multivrible Cox nlysis, vribles independently ssocited with renl filure during ECMO included higher PFH, higher hemoglobin, higher lctte, nd loction of ECMO in PICU (Tble 6). Univrible Cox models of mortlity re shown in Supplementl Tble 3 (Supplementl Digitl Content 3, A744). Vribles independently ssocited with mortlity included ECPR s the indiction for ECMO, higher RBC trnsfusion volume, lower heprin infusion dose, nd lower ph (Tble 7). Mortlity ws not ssocited with PFH on multivrible nlysis. DISCUSSION Nerly ll peditric ptients in our ECMO cohort hd some degree of hemolysis, nd 67.1% hd moderte to severe hemolysis (PFH 0.5 g/l). Using the ELSO registry, O Brien et l (18) reported hemolysis (PFH > 0.5 g/l) occurring in 10.6% of peditric ECMO runs between 2010 nd In singlecenter retrospective review, Lou et l (5) reported hemolysis ( 0.5 g/l) in 19.3% of peditric ECMO ptients between 2005 nd Differences in study design, nd the frequency nd consistency of obtining PFH mesurements likely ccount for the differences in rtes observed. Ptient-relted fctors, ECMO setup nd mngement fctors, nd vrious lbortory vlues were found to be ssocited with the severity of hemolysis during ECMO in our study. Hemolysis ws lso found to be ssocited with severl complictions during ECMO including renl filure. Whether hemolysis results in renl filure or occurs s consequence of tretment modlities such s CRRT could not be determined. Hemolysis ws not ssocited with mortlity fter controlling for other fctors November 2018 Volume 19 Number 11

7 Extrcorporel Support TABLE 5. Multivrible Cox Model of Renl Filure TABLE 6. Multivrible Cox Model of Mortlity Vribles Renl Filure Hzrd Rtio (95% CI) p Vribles Mortlity Hzrd Rtio (95% CI) p Plsm free hemoglobin (for ech 0.1 g/l increse) Loction of extrcorporel membrne oxygention cre 1.04 ( ) < PICU 1.28 ( ) Neontl ICU 0.36 ( ) Crdic ICU Reference Hemoglobin (g/dl) (10 g/l) 1.20 ( ) Lctte (mmol/l) 1.06 ( ) Rtes of missingness for ll predictors considered for modeling re included in Supplementl Tble 2 (Supplementl Digitl Content 2, com/pcc/a743). The outcome, renl filure, ws never missing. This nlysis includes only the 184 subjects without renl filure t bseline; of those, 59 developed renl filure. In ddition to the vribles used in the model for plsm free hemoglobin, this lso uses dily bleeding nd thrombosis s potentil predictors nd forces plsm free hemoglobin in s predictor. Importntly, need for in-line hemofiltrtion nd continuous renl replcement therpy is not considered s potentil predictor. Among ptient-relted fctors, lower body weight ws independently ssocited with higher dily PFH in our study. This finding on multivrible nlysis is consistent with the neontl nd infnt ge groups being ssocited with higher dily PFH on univrible nlyses. Lower body weight is likely ssocited with incresed fetl RBCs which show greter susceptibility to mechnicl stress thn dult RBCs (19). The mechnism for greter hemolysis with lower body weight my lso be relted to more sher stress with flows through smller cliber cnnuls nd blood vessels (19 21). Other ptient-relted fctors such s vrious cute nd chronic dignoses were lso found to Plsm free hemoglobin (for ech 0.1 g/l increse) Primry extrcorporel membrne oxygention indiction Respirtory Reference 1.01 ( ) Crdic 1.56 ( ) Extrcorporel crdiopulmonry resuscittion 5.35 ( ) Heprin (0.01 U/kg/min) 0.94 ( ) < RBCs trnsfused (10 ml/kg) 1.02 ( ) ph in rteril blood (0.05 increse) 0.72 ( ) Rtes of missingness for ll predictors considered for modeling re included in Supplementl Tble 3 (Supplementl Digitl Content 3, com/pcc/a744). The outcome, mortlity, ws never missing. In ddition to the vribles used in the model for plsm free hemoglobin, this lso uses dily bleeding nd thrombosis s potentil predictors nd forces plsm free hemoglobin in s predictor. The popultion t risk consists of subjects while on extrcorporel membrne oxygention (ECMO) nd thus does not cpture deth occurring fter the lst dy of ECMO. be independently ssocited with dily PFH levels. Estblishing resons for these ssocitions is outside the scope of this report; some my represent spurious findings. Aspects of ECMO setup nd mngement were ssocited with PFH levels. Lower heprin infusion dose djusted for body weight (U/kg/min) ws independently ssocited with higher dily PFH. Higher heprin infusion doses could reflect more TABLE 7. Multivrible Model for Plsm Free Hemoglobin Vribles Plsm Free Hemoglobin (0.01 g/l) Effect (95% CI) p Chronic neurologic condition ( to 1.81) Chronic immune dysfunction ( to 13.29) < Acute nonseptic shock ( to 15.72) < Acute neurologic condition ( ) Hemofiltrtion or continuous renl replcement therpy ( ) Totl bilirubin (mg/dl) (17.10 μmol/l) 4.15 ( ) < Hemoglobin (g/dl) (10 g/l) 6.01 ( ) < Weight (kg) 0.34 ( 0.51 to 0.17) < Heprin (U/kg/min) ( to 13.18) Pltelets (10 3 /μl) 0.15 ( 0.27 to 0.03) Rtes of missingness for ll predictors considered for modeling re included in Supplementl Tble 1 (Supplementl Digitl Content 1, PCC/A742). The outcome, plsm free hemoglobin, ws missing on 8% of study dys. Peditric Criticl Cre Medicine

8 Dlton et l ggressive mngement style with some centers titrting heprin dose to higher levels to chieve better nticogultion or to be consistent with lbortory monitoring lgorithms. Another possibility is tht the nonnticogulnt effects of heprin including nti-inflmmtory properties, inhibition of rective oxygen species genertion, tissue protection nd repir properties, nd crdiovsculr protective effects lso decrese hemolysis (22, 23). Use of in-line hemofiltrtion or other forms of CRRT ws independently ssocited with higher dily PFH levels. These therpies my contribute to hemolysis by diverting venous flow wy from the ECMO circuit thereby contributing to negtive inlet pressure (5), providing dditionl res of turbulent flow t connector sites, or incresing red cell destruction by mechnicl stresses within the CRRT system. CRRT itself is ssocited with hemolysis (24). Unlike previous reports we did not find cler ssocition between hemolysis nd use of centrifugl or roller hed pumps (18, 25); however, roller hed pumps were used in only 15 ptients (6.9%). Of 201 ptients with centrifugl pumps, over 60% hd moderte to severe hemolysis bsed on pek PFH levels. Using the ELSO registry, O Brien et l (18) found more hemolysis with centrifugl thn roller pumps lthough hemolysis ws reported less frequently in the ELSO registry overll. Other potentil fctors for differences include the type of centrifugl pump used (older versions were known to be ssocited with hemolysis), nd the fct tht mny ptients during the time period in the ELSO report received centrifugl support following crdic rrest or crdic surgery. Such fctors my lso influence hemolysis regrdless of pump type. Higher hemoglobin concentrtion during ECMO ws independently ssocited with higher dily PFH consistent with recent single-center report (16). Higher hemoglobin levels increse blood viscosity (26 28) which my result in more red cell dmge s blood trverses the ECMO pump hed nd oxygentor. In dults, incresed hemoglobin nd blood viscosity hve been ssocited with crdiovsculr nd cerebrovsculr ischemic events (26 28). Although hemoglobin level ws n independent predictor of PFH in our study, the volume of RBCs trnsfused ws not n independent predictor. Hemoglobin level nd red cell trnsfusion volume re cliniclly interrelted; however, our findings suggest tht hemoglobin level is the stronger predictor of hemolysis. On the other hnd, the volume of RBCs trnsfused nd not dily PFH level ws n independent predictor of mortlity. Red cell trnsfusion likely contributes to mortlity by mechnisms other thn or in ddition to hemolysis such s trnsfusion-relted immune dysfunction or lung injury (29 31). The optiml hemoglobin level for peditric ECMO ptients is uncler but dditionl studies focused on trnsfusion thresholds my improve rtes of hemolysis nd mortlity. Higher bilirubin concerttion nd lower pltelet count were independently ssocited with higher dily PFH levels. Hyperbilirubinemi is known compliction of ECMO nd hemolysis contributes to n increse in bilirubin production (32 34). At high levels, bilirubin cn induce poptosis, inflmmtion, nd oxidtive stress which cn led to thrombocytopeni (32, 35). In ddition, hemoglobin-medited nitric oxide scvenging nd reduced plsm nitric oxide cn cuse thrombocytopeni (11, 36). Therefore, wheres higher hemoglobin my predispose to hemolysis, higher bilirubin level, nd lower pltelet count likely occur s result of hemolysis. Our findings suggest tht hemolysis is ssocited with complictions during ECMO including renl filure. PFH in sufficient mounts cn be dmging to the kidney nd other orgns becuse of its biorectivity nd prooxidnt effects (37). Similr to our findings, others hve shown tht PFH predicts cute renl filure during venorteril ECMO (36, 38). Hemolysis during combined ECMO nd CRRT hs been shown to be incresed compred with ECMO lone (10). These reciprocl reltionships suggest tht use of in-line hemofiltrtion or CRRT my contribute to worsening renl filure by promoting hemolysis, lthough the extent is difficult to determine. Our findings lso suggest ssocitions between hemolysis nd bleeding nd thrombotic events, other orgn filures, nd durtion of ECMO. Thrombosis my lso be cuse of elevted PFH complicting our understnding of the reltionship between hemolysis nd thrombotic events. Hemolysis ws not n independent predictor of mortlity in our multivrible Cox model; this is in contrst to other reserch suggesting n ssocition between hemolysis nd mortlity (5). PFH ws not routinely monitored cross ll eight CPCCRNffilited centers. Consistent monitoring nd further inspection of site-specific fctors such s circuit setup, lbortory testing, or nticogultion lgorithms my identify best prctices tht cn be prospectively evluted. The bility to refine ECMO prctices to reduce hemolysis nd ssocited morbidities would benefit the field. Strengths of this study include the multicenter design nd dily prospective collection of dt. Limittions include recording the PFH levels nd other dily dt (i.e., lbortory studies, body temperture, nd ECMO flow rte) tht were obtined closest to 7 m rther thn ll vlues nd the lck of stndrdized protocol for the timing nd frequency of PFH levels. Although our definition of renl filure ws cretinine level of greter thn 2 mg/dl (> μmol/l), it lso included the use of in-line hemofiltrtion, which some prctitioners employ to mnge fluid sttus even in the bsence of renl filure. This fctor is nother potentil limittion. Missing dt for some vribles prevented their inclusion in multivrible models. Although mny vribles were evluted, potentil unmesured confounders exist. Importntly, this is n observtionl study nd the ssocitions observed do not infer custion. CONCLUSIONS Our findings suggest tht nerly ll peditric ptients undergoing ECMO hve some degree of hemolysis. Hemolysis my contribute to the development of renl filure, nd therpies used to mnge renl filure such s in-line hemofiltrtion nd CRRT my contribute to hemolysis. Hemolysis ws lso ssocited with other morbidities. Our findings suggest tht November 2018 Volume 19 Number 11

9 Extrcorporel Support monitoring for hemolysis should be routine component of ECMO prctice, nd efforts to reduce hemolysis my improve ptient cre. ACKNOWLEDGMENTS We cknowledge the contributions of the following reserch coordintors nd dt coordinting center stff: Stephnie Bisping, BSN, RN, CCRP, Aleci Peterson, BS, nd Jeri Burr, MS, RN-BC, CCRC, from University of Uth, Slt Lke City, UT; Mry Ann DiLiberto, BS, RN, CCRC nd Crol Ann Twelves, BS, RN, from The Children s Hospitl of Phildelphi, Phildelphi, PA; Jen Rerdon, MA, BSN, RN nd Elyse Tomnio, BSN, RN, from Children s Ntionl Medicl Center, Wshington, DC; Aimee Lbell, MS, RN, from Phoenix Children s Hospitl, Phoenix, AZ; Mrgret Vill, RN nd Jeni Kwok, JD, from Children s Hospitl Los Angeles, Los Angeles, CA; Mry Ann Nyc, BS, from UCLA Mttel Children s Hospitl, Los Angeles, CA; Ann Pwluszk, BSN, RN nd Melnie Lulic, BS, from Children s Hospitl of Michign, Detroit, MI; Monic S. Weber, RN, BSN, CCRP nd Luren Conlin, BSN, RN, CCRP, from University of Michign, Ann Arbor, MI; Aln C. Abrhm, BA, CCRC, from University of Pittsburgh Medicl Center, Pittsburgh, PA. We lso cknowledge the contributions of Robert Tmburro, MD, nd Tmmr Jenkins, MSN, RN, from the Eunice Kennedy Shriver Ntionl Institute of Child Helth nd Humn Development Collbortive Peditric Criticl Cre Reserch Network. REFERENCES 1. Dlton HJ, Reeder R, Grci-Filion P, et l; Eunice Kennedy Shriver Ntionl Institute of Child Helth nd Humn Development Collbortive Peditric Criticl Cre Reserch Network: Fctors ssocited with bleeding nd thrombosis in children receiving extrcorporel membrne oxygention. Am J Respir Crit Cre Med 2017; 196: Annich GM, Meinhrdt JP, Mowery KA, et l: Reduced pltelet ctivtion nd thrombosis in extrcorporel circuits coted with nitric oxide relese polymers. 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10 Dlton et l 33. Misels MJ, McDongh AF: Phototherpy for neontl jundice. N Engl J Med 2008; 358: Abbsi S, Stewrt DL, Rdmcher P, et l: Nturl course of cholestsis in neontes on extrcorporel membrne oxygention (ECMO): 10-yer experience t single institution. ASAIO J 2008; 54: Somnthpur K, Kumr N, Thushr RM, et l: Unconjugted bilirubin exerts proapoptotic effect on pltelets vi p38-mapk ctivtion. Sci Rep 2015; 5: Lyu L, Long C, Hei F, et l: Plsm free hemoglobin is predictor of cute renl filure during dult venous-rteril extrcorporel membrne oxygention support. J Crdiothorc Vsc Anesth 2016; 30: Trcz MJ, Alm J, Nth KA: Physiology nd pthophysiology of heme: Implictions for kidney disese. J Am Soc Nephrol 2007; 18: Lv L, Long C, Liu J, et l: Predictors of cute renl filure during extrcorporel membrne oxygention in peditric ptients fter crdic surgery. Artif Orgns 2016; 40:E79 E November 2018 Volume 19 Number 11