Thursday May 8, 2008
ECMO update

Extracorporeal membrane oxygenation (ECMO) refers to the technique of providing both cardiac and respiratory support oxygen to patients by draining blood from the venous system and oxygenating it outside of the body. ECMO uses cardio-pulmonary bypass technology to temporarily provide gas exchange to patients with severe, but potentially reversible, respiratory failure. ECMO is a standard practice in neonatal and pediatric ICUs to support pulmonary failure but remained a very last resort in adult ICUs due to the high technical demands, cost, and risk of bleeding (requires anticoagulation). The major reason ECMO remained unused in adult ICUs is a negative study done about 29 years ago. The National Institutes of Health trial of ECMO in severe acute respiratory failure in 1979 showed mortality in excess of 90% .

ECMO could be a bridge till definite therapy is sought or till healing occurs. Technically, VV or VA (veno-veno or veno-arterial) ECMO can provide sufficient oxygenation for several weeks.

One recent trial called CESAR (Conventional Ventilation or ECMO for Severe Adult Respiratory Failure) showed increase survival among adult patients with severe but potentially reversible respiratory failure compared with conventional ventilatory support.

Data from CESAR trial showed that ECMO may increase the rate of survival without severe disability 6 months after randomization and may be cost-effective compared with conventional ventilatory support.

The conventional treatment group was treated with standard clinical practice, with a low-volume ventilation strategy.

The primary outcome measure was death or severe disability 6 months after randomization and included deaths before hospital discharge if occurring after 6 months.

Severe disability was defined as being both "confined to bed" and "unable to wash or dress oneself."

Patients: A total of 180 patients from 68 centers were randomly assigned to receive

• conventional ventilation (n = 90)
• ECMO (n = 90)

Of the 90 patients assigned to receive ECMO, 22 did not receive ECMO, most often because they improved without it.

A significant number of patients had failure of more than 3 organs in both groups (28 in the ECMO group and 27 in the conventional group).

Results:

• Of the patients randomly assigned to receive ECMO, 57 of 90 met the primary endpoint of survival or absence of severe disability at 6 months compared with 41 of 87 evaluable patients in the conventional ventilation group (survival benefit 63% vs 47%).
• There was also a nonsignificant trend toward decreased deaths before 6 months in the ECMO group vs the conventional ventilation group (57 of 90 vs 47 of 87).
• Patients in the conventional group died more quickly than in the ECMO group (5 vs 15 days). One ECMO-related death occurred, which was attributed to a cannulation problem.
  

Conclusion: The benefit of ECMO was seen regardless of several factors including hospital of trial entry, age, presence of hypoxia, duration of high-pressure ventilation, primary diagnosis at trial entry, and number of organs failed.

Initial data presented by Giles J. Peek, MD, FRCS, from the University of Leicester, Glenfield, United Kingdom, at the Society of Critical Care Medicine 37th Critical Care Congress 2008, Hawaii.

Pre-report details can be read here