ECMO in patients with circulatory arrest
Deep hypothermic circulatory arrest (DHCA) is a technique utilised
during procedures requiring circulatory arrest such as surgery involving
the aortic arch for the purpose of organ protection, specifically for
cerebral protection, as hypothermia inhibits injury-inducing ischaemic
pathways driven by hypoxia24-26. DHCA utilises CPB to
maintain perfusion to the rest of the body during the procedure but the
need for prolonged CPB comes with its own complications such as
coagulopathy and failure to wean from CPB, thereby requiring ECMO for
circulatory support.
There is little to no evidence on ECMO use following DHCA in adult
patients but there are a few studies that have looked at outcomes in
paediatric patients who required ECMO following DHCA as part of the
Norwood procedure used for surgical treatment of cardiac defects
characterised by the presence of shunted single-right ventricle
circulation such as hypoplastic left heart syndrome
(HLHS)27-29. Analysis of 549 patients with
single-right ventricle anomalies enrolled in the Pediatric Heart Network
Single Ventricle Reconstruction trial found that post-operative ECMO
requirement was a significant indicator for increased 30-day mortality
(OR 4.38; 95% CI 1.76-10.90; P =0.002) and for hospital mortality
(Hazard ratio 3.41; 95% CI 1.94-5.98;P <0.001)27. The study was carried out
across paediatric cardiac surgery centres with a large volume of cases
annually meaning these findings cannot be generalised to centres with
smaller case volumes. However, similar results were shown in a
retrospective study analysing risk factors for 1-year mortality in 158
patients that underwent the Norwood procedure which demonstrated that
ECMO or VAD support was associated with increased risk of death (OR
17.8; 95% CI 4.4-71.0; P< 0.001)28.
Further separate analysis of subjects enrolled in the Single Ventricle
Reconstruction trial of 461 patients discharged home after undergoing
the Norwood procedure showed that 66 of them (14.3%) developed heart
failure, with 15 of these dying from the heart failure whilst 39 were
listed for transplant29. The study found that need for
ECMO post-operatively, among other factors, was significantly associated
with increased risk of developing heart failure within a year
post-Norwood procedure (Hazard ratio 5.83; 95% CI 1.75-19.46;P =0.004) when compared to those not requiring extracorporeal
support. Outcomes for ECMO instituted following DHCA are summarised in
Table 5.
The little data that does exist on ECMO following DHCA suggests that
those patients requiring post-operative ECMO had an increased mortality
both in hospital and following hospital discharge; though mortality for
PCCS without MCS would be far worse. However, there are very few studies
that have been carried out meaning it may not be appropriate to
generalise these findings to other populations. The gap in research in
this area suggests the need for more to be carried out to see if there
is a survival benefit associated with use of ECMO in patients who have
undergone DHCA.