Saturday, September 19, 2009

The ECMO Option



# 3754



ECMO or Extracorporeal Membrane Oxygenation is a specialized heart-lung bypass machine used to take over the body’s heart and lung function – for days or weeks if necessary – while the body heals from injury or illness.


ECMO is a highly specialized, and technically demanding life support option which is not available a most hospitals around the globe.  It is most commonly used in neonatal intensive care units for newborns in respiratory distress, although it is also used for pediatric and adult patients with severe heart or respiratory deficits.


One of the disturbing hallmarks of the novel H1N1 `swine’ flu virus is that it produces – in a very small percentage of victims – severe lung damage resulting in ARDS (Acute Respiratory Distress Syndrome).  


Over the summer, a number of these flu patients have been placed on ECMO machines, to give their damaged lungs time to heal, as demonstrated in the CBS Evening News Video below (hat tip mcphilbrick on FluTrackers).





Normally, patients with ARDS are placed on mechanical ventilation in ICUs, and treated with a variety of pharmacological agents to reduce infection (antibiotics) and lung inflammation (corticosteroids, Nitric Oxide, etc.).  


Despite these measures, ARDS is generally fatal in 50% of patients.


With H1N1 viral pneumonia, mechanical ventilation often does not result in adequate oxygenation, as the lungs are too congested to allow oxygen exchange in the alveoli.


(Image adapted from Wikipedia)


With ECMO, the burden of pumping and oxygenating the blood is taken from the heart and lungs, and they are given time to heal. 



A more detailed explanation is available in this emedicine article on ECMO (above image from that article).


In a Lancet Study, published earlier this week, UK researchers determined that ARF (Adult Respiratory Failure) patients that received ECMO support as opposed to conventional ventilation have a greater survivability without disability.


Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial



ECMO resources are extremely limited of course, and are not available in many regions of the world.  


Even in places where it is available, triage decisions regarding which severely affected H1N1 patients will get this sort of life support – and for how long – will become tougher as we progress into this flu season.


The number of staffed ECMO support beds available in the US appears to number in the low-to-mid hundreds. 


While ECMO can improve a patient’s odds of surviving, it is by no means a sure thing. Complications, including infection at the site of cannulation, are not uncommon.


This is a last ditch, heroic measure, reserved for those who cannot survive without it.   But for those with severe H1N1 induced ARDS, it may be their last, best option.