Future of ECMO in Cardiac surgery
VA-ECMO is indicated when patients fail to be weaned off CPB or
clinically deteriorates significantly during the course of staying on
intensive care stay. ECMO provides a longer support for a few days to
allow for recovery of the cardiopulmonary system, compared to a few
hours of support with CPB. VA-ECMO confers several advantages that helps
increasing patient survival and reduce mortality rates. CPB needs a
large amount of unfractionated heparin as it utilises a venous reservoir
which causes blood to stagnate. CPB also causes blood to pool in the
heart chambers and respiratory circulatory system, which result in an
increase in activated clotting time.
Whereas, VA-ECMO does not utilise a venous reservoir and is made of
shorter tubes. There is reduced occurrence of thrombosis allowing for a
reduction in the dosage of unfractionated heparin which can then reduce
bleeding complications. Hence, VA-ECMO use in refractory PCCS has been
shown to provide significant survival benefits without which mortality
would be inevitable. Increased age, renal failure and long use of ECMO
support are the most frequently reported adverse prognostic factors .
Over the recent years, the use of ECMO has greatly increased. According
to ELSO, the use of adult ECMO increased by about tenfold over the past
decade. This is likely following a ground-breaking study, the CESAR
trial, which showed a significant increase in survival without severe
disability when ECMO was used instead of conventional ventilation. Early
initiation of ECMO has been shown to result in higher survival rates and
decreasing the dosage of vasoactive drugs by increasing cardiac output
and rapidly decreasing arterial lactate levels after cardiovascular
surgery. This is shown in a study which compared two groups of patients
where the patients with early initiation ECMO failed to be weaned off
CPB once, while the patients with delayed ECMO failed to weaned off
thrice.This could help provide a guide as to when ECMO should be
initiated in patients after cardiac surgery to improve outcomes.
ECMO technology is constantly evolving and improving, with more compact
and durable components being introduced in recent times. Wearable
ambulatory ECMO has been developed and trialled in patients with severe
cardiopulmonary failure awaiting transplant. Compact ECMO is achievable
by the use of hollow fibre membranes arranged in stacks with centrifugal
pumps. This allows increased patient mobility which helps with
rehabilitation and early mobilisation allowing patients to walk and
exercise, preventing muscle atrophy allowing shorter recovery time and
placing patients in a better physiological state for heart or lung
transplant. It also helps to decrease total costs by about 11% compared
to traditional ECMO use. This could soon be the new future of ECMO,
which is currently still a complex and bulky piece of equipment
resulting in patients being bedbound, slowing recovering.
Unfortunately, ECMO is a very costly form of life support at about
£45,000 per patient. It is also resource intensive, requiring a high
level of expertise to use it. An article states that the National
Specialist Commissioning Group only funds ECMO to certain specialist
centres, restricting its access which is inappropriate and unacceptable
considering its great benefits to patients’ survival rates. Whereas, in
other parts of the world such as the US and Europe, ECMO is routinely
used. It is contentious to say whether the UK has too many restrictions
to use of ECMO or if the UK is being too prudent. VA ECMO is not
commissioned by the National Health Service (NHS) for PCCS and the price
of it is forked out by individual hospitals in the UK. Most recently,
ECMO is being used widely in COVID-19 patients where they may develop
cardiac arrhythmias and shock. About 15% to 30% of patients with the
viral pneumonia developed acute respiratory distress syndrome (ARDS)
where the WHO recommendations included ECMO as a part of the management.
The role of ECMO for COVID-19 patients is still unclear and is dependent
on the mechanism which the virus harms the body. If it causes septic
shock and multiorgan failure, the management will likely shift away from
ECMO as it may be less helpful in these instances. Although
inconclusive, an article brought up concerns about the use of ECMO in
COVID-19 patients, suggesting healthcare professionals evaluate the IL-6
concentration and lymphocyte count before and during ECMO, as ECMO
increases IL-6 levels and decreases lymphocyte count. More studies
should be carried out to determine the usefulness of ECMO in this
situation, especially when they need an emergency cardiac surgery.