Blood Utilization in ECMO Patients Omar Alsuhaibani Transfusion Medicine Journal Club

Background EXTRACORPOREAL MEMBRANE OXYGENATION (ECMO) is a technique, pioneered by Bartlett et al., for the treatment of severe respiratory failure, especially in neonatal patients. The procedure permits oxygenation of blood while bypassing the lungs, thereby allowing resolution of the primary pulmonary pathology. A modified heart-lung machine is used. Bartlett et al., Surgery, 1982;92:425-33

Background In veno-arterial ECMO, blood is collected from the right atrium via the external jugular vein, passed through a membrane oxygenator and heat exchanger, and returned to the systemic circulation through a perfusion cannula, usually via the right common carotid artery. Venovenous ECMO, in which blood is returned through a perfusion cannula via the femoral vein, has been attempted but is not the method of choice. McCoy-Pardington et al., Transfusion , 1990;30:307-309

Background ECMO has particular application for infants with impaired pulmonary function associated with: congenital diaphragmatic hernia (CDH) meconium aspiration (MA) persistent fetal circulation (PFC) respiratory distress syndrome (RDS) sepsis. McCoy-Pardington et al., Transfusion , 1990;30:307-309

Background While ECMO has been employed most widely for treatment of severe respiratory failure in neonatal patients, it more recently has been utilized also to treat respiratory failure in adults. In both age groups, the goal of the procedure is to oxygenate the blood without involving the lungs. Butch et al., Transfusion,1996;36:61-63

Background As in the pediatric group, pulmonary dysfunction in adults has been the clinical condition occasioning ECMO. These patients are considered to have an estimated 90% risk of mortality with conventional treatment.

Background ECMO in neonatal patients does not impose a significant burden on a hospital transfusion service. In contrast to the situation with neonates, it seemed that ECMO performed on adult patients imposed a considerably greater burden on hospital blood banks and required a much greater level of blood component support. Butch et al., Transfusion,1996;36:61-63

Objectives Primary objectives (i) describe the red blood cell, platelet, fresh-frozen plasma (FFP) and cryoprecipitate requirements of adult patients in our institution while they were undergoing ECMO. (ii) determine independent clinical variables that may be associated with increased red blood cell, platelet and FFP transfusions during ECMO. Secondary objectives assess the mortality of adult patients who underwent ECMO and to evaluate if this procedure helped to improve overall survival.

Patient Selection All patients aged 16 years and above who had undergone ECMO at the National Heart Centre, Singapore, between June 2003 and September 2006. Patients with incomplete transfusion or clinical records were excluded. Exclusion criteria included active uncontrollable bleeding or potential for severe bleeding, poor quality of life, septic shock and morbid obesity.

ECMO Guidelines Severe respiratory failure refractory to conventional treatment and support. (2) Post-cardiotomy shock: ECMO is instituted in patients who have undergone cardiac surgery and have good chances of recovery, but are unable to be weaned off cardiopulmonary bypass (CPB) despite conventional inotropic support and intra-aortic balloon pump. ECMO will be replaced with a long-term device, for example, ventricular assisted device (VAD), if myocardial recovery does not occur within the short term and if the patient is a heart transplant candidate. cont.

ECMO Guidelines (3) Acute cardiogenic shock resulting from myocardial infarction, myocarditis, intractable cardiac arrhythmia, etc. as a bridge to VAD implantation, cardiac transplantation, other intervention or myocardial recovery. (4) Massive PE as a bridge to surgical pulmonary embolectomy. (5) Heparin to maintain an activated clotting time of 180–220 seconds. (6) Patients’ haemoglobin (Hb) and platelet counts should be kept at a minimum of 10 g/dl and 100 × 109/l, respectively.

Clinical and transfusion information A retrospective review of the clinical and transfusion records of all selected patients. Information on the total number of red blood (RBC) cell units, random platelet units, single-donor aphaeresis platelet concentrates, FFP and cryoprecipitate received by each patient during the days of ECMO was obtained. Universal leucoreduction is not practiced in Singapore. The average daily RBC, platelet, FFP and cryoprecipitate, as well as the maximum daily RBC and platelet received by each patient were also calculated.

Clinical and transfusion information Demographic and clinical variables that may influence RBC, platelet and FFP requirements were recorded for each patient. Demographic variables included - age - gender - ethnic group - body surface area (BSA)

Clinical and transfusion information Clinical variables included - co-morbidities - underlying diseases necessitating ECMO - renal failure - sepsis during ECMO - bleeding during ECMO - sites of bleeding - ECMO indications and types - overall mortality - mortality during ECMO - whether surgeries were performed before and/or during ECMO - Hb and platelet counts before and during ECMO

Statistical analysis All categorical variables were compared using Fischer-exact test or χ2-test Continuous variables (except BSA) were analysed using Mann–Whitney U-test. Correlation between two continuous variables (except BSA) was assessed using Spearman’s correlation coefficient. BSA was the only continuous variable that fulfilled tests of normality, and was analysed using two sample t-test or Pearson’s correlation coefficient when relevant. All analyses was done using SPSS

Results Forty-one patients (median age 50 years) underwent 42 ECMO sessions for respiratory failure (16·7%), cardiogenic shock (76·2%) or massive pulmonary embolism (7·1%). They received 569 red blood cells, 852 platelets, 126 fresh-frozen plasma (FFP) and 220 cryoprecipitate in total during median ECMO duration of 5 (1–15) days. On multivariate analysis, average daily red blood cell transfusion increased with nadir haemoglobin (Hb) during ECMO (Hb nadir) of < 7·5 g/dl (P < 0·001).

Results Average daily platelet transfusion increased with - recent antiplatelet agents (P = 0·015), and - maximum Hb decline of > 5·5 g/dl during ECMO (P = 0·011). Average daily platelet transfusion > 3 units was also associated with increased ECMO duration (P = 0·024).

Results Average daily FFP transfusion was increased in patients with hypertension (P = 0·007) and Hb nadir < 7·5 g/dl (P = 0·050). Patients with sepsis (P = 0·009) or without surgery (P = 0·009) had increased ECMO duration, which correlated positively with total transfusion requirements during the entire ECMO session. ECMO improved mortality of patients with fulminant myocarditis, respiratory failure and massive pulmonary embolism.

Conclusion Adult ECMO patients with lower Hb nadir require more daily red blood cell and FFP. Hypertension increases daily FFP requirements. Recent antiplatelet agents, larger Hb decline and longer ECMO duration increase daily platelet requirements. Patients with sepsis or on ECMO for medical reasons have longer ECMO duration, which is associated with total transfusion requirements.

Conclusion The transfusion demands of adult ECMO patients are high. Measures may be instituted earlier, and close cooperation between the managing clinician and the transfusion physician is necessary to ensure good transfusion support for these patients without adding excessive burden to the blood bank.

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