Extracorporeal membrane oxygenation (ECMO) has become the standard of care for life-threatening acute respiratory and cardiac failure in the intensive care unit (ICU). Infections are crucial complications during ECMO treatment.1,2 The high rate of infection in these patients in the ICU is due to their critically ill clinical status and the multiple entry points for pathogens both within the ECMO circuit (including cannulas for ECMO) and catheters, and the maneuvers often needed by the patient (continuous renal replacement therapy, prolonged mechanical ventilation, tracheotomy, etc.). However, several studies report acceptable outcomes in patients presented with severe bloodstream infections.3,4 Apart from infections, frequency and impact of material colonization remain unclear.5
In this issue, the article by Kuehn et al.6 addresses membrane oxygenator (MO) colonization. They used an rDNA gene-based polymerase chain reaction (PCR) test in 19 patients undergoing ECMO support for an average of 16.3 days (2–51 days). This test permits a rapid diagnosis of MO colonization even in patients receiving antibiotics as nine patients (42%) were positive. Staphylococcus species were the most frequent pathogens, concerning 58% of MO episodes, whereas Gram-negative bacteria and fungi accounted for 17% and 8%, respectively, of the episodes. Colonization was caused by mixed pathogens in half of the cases.
The main challenge is to assess the clinical impact of MO colonization. In this study, PCR testing for MO colonization predicted bacteremia with a sensibility of 57% and a specificity of 54%. Positive predictive value in this setting was 44%. The link between colonization and infection thus appears weak in the study and should be analyzed in the future on larger effectives.
Response to MO colonization represents the second challenge in analyzing the results. Membrane oxygenator replacement when colonized, as proposed by authors, needs to be validated in further studies on larger and more homogeneous populations of ECMO recipients. Respiratory (venovenous-ECMO) and cardiac (venoarterial-ECMO) patients, whose clinical profile and risk factors are different, should be analyzed separately. Furthermore, MO replacement does not totally resolve circuit colonization as cannulas remain in place and could largely account for material colonization. Long-term antibiotic prophylaxis, which is also proposed by the authors, seems highly questionable considering the risk of selecting drug-resistant bacteria in those patients.2
The clinical impact of MO colonization remains to be clarified in larger trials, and interventions to prevent or abrogate it remain to be validated. If the prognostic value of MO colonization and the interventional relevance of MO exchange will be clarified from future experiences, PCR could become routine in the management of ECMO.
1. Sun HY, Ko WJ, Tsai PR, et al. Infections occurring during extracorporeal membrane oxygenation use in adult patients. J Thorac Cardiovasc Surg. 2010;140:1125–1132.e2
2. Schmidt M, Bréchot N, Hariri S, et al. Nosocomial infections in adult cardiogenic shock patients supported by venoarterial extracorporeal membrane oxygenation. Clin Infect Dis. 2012;55:1633–1641
3. Rich PB, Younger JG, Soldes OS, Awad SS, Bartlett RH. Use of extracorporeal life support for adult patients with respiratory failure and sepsis. ASAIO J. 1998;44:263–266
4. Brechot N, Luyt CE, Schmidt M, et al. Venoarterial extracorporeal membrane oxygenation support for refractory cardiovascular dysfunction during severe bacterial septic shock. Crit Care Med. Apr 4, 2013 [Epub ahead of print]
5. Müller T, Lubnow M, Philipp A, et al. Risk of circuit infection in septic patients on extracorporeal membrane oxygenation: A preliminary study. Artif Organs. 2011;35:E84–E90
6. Kuehn C, Orszag P, Burgwitz K, et al. Microbial adhesion on membrane oxygenators in patients requiring extracorporeal life support detected by a universal rDNA gene-based PCR test. ASAIO J. 2013;59:XXX