Extracorporeal membrane oxygenation in the adult patient: experience in a medical ICU

Introduction

Extracorporeal membrane oxygenation (ECMO) is a technology that provides gas exchange and supports cardiac function in patients with ARDS or cardiac failure. We report on the experience with ECMO in our medical ICU, a tertiary centre.

Patients

ECMO was started in 20 patients (14 males/six females) failing conservative treatment with life-threatening respiratory (13 patients), cardiac (two patients) or combined failure (five patients). Bypass surgery was performed bedside. For respiratory failure, veno-venous (v/v) access was used; for cardiac failure, veno-arterial (v/a) access was preferred. The mean age was 45.3 years. Nine apparently immunocompetent patients presented with community-acquired pneumonia (CAP). Two of these later appeared immunocompromised and had opportunistic infections. Eight other immunocompromised patients received ECMO. The remaining three patients had ARDS due to sepsis, cardiogenic shock and nosocomial pneumonia.

Results

The average APACHE II score was 24.5 and SOFA score was 11.5. The Murray score before the start of ECMO averaged 3.2. The mean duration of ventilation was 32.5 hours and the average PaO₂/FIO₂ was 53.8 mmHg. In 13 patients the bypass was initially v/v, in seven patients v/a. In one patient v/v access was changed to v/a as cardiac failure developed. In another patient the v/a bypass was switched to v/v for insufficient oxygenation of the upper body. The mean duration of ECMO was 6.4 days (range 0.5–18), and mean duration of mechanical ventilation was 13.1 days (range 0.5–36). Overall survival was 50%. All patients that survived weaning from ECMO were also discharged and are still alive with a mean follow up of 804 days. Seven out of nine patients with CAP survived. Only 3/10 immunocompromised patients survived. All three are still alive after 2, 23 and 34 months. Ten out of 20 patients died. Twelve technical complications occurred, two of which were fatal (massive bleeding).

Discussion and conclusion

ECMO is a potentially life-saving technology. Our overall survival was 50%. Unfavourable factors such as low pH and low pO₂/FIO₂ do not exclude a successful ECMO intervention as our two patients with the lowest pH (6.89 and 6.95) survived, as did four out of seven patients with PaO₂ /FIO₂ < 40 mmHg. Predictive factors therefore cannot be used as exclusion criteria. Patients who develop intractable acute respiratory insufficiency due to CAP without underlying disease seem to benefit most from ECMO. Most series of ECMO reported in the literature exclude immunocompromised patients. We confirm that these patients stand a poor prognosis (survival of 30%). However, long-term and good functional survival appears to be possible in selected patients. v/a bypass seems to carry a higher risk for major and potentially fatal technical complications. v/a bypass is only indicated if cardiac support is required. Increasing experience from the ECMO team probably reduces the incidence of technical complications.