respiratory and/or cardiovascular support in the State of São Paulo,
Brazil
INTRODUCTION
The use of extracorporeal membrane oxygenation (ECMO) support has increased in recent
years,(1) especially
following the pandemic of influenza A (H1N1) virus pneumonitis.(2-4) Although the results of previous randomized trials in which
ECMO was used for respiratory support are inconclusive,(5,6) new
technologies(7) associated
with the application of ultraprotective mechanical ventilation(8) have improved survival and the
quality of life when ECMO is used for patients with severe respiratory
failure.(9,10)
The high cost of the training and support required for ECMO use may have a negative
economic impact, especially in developing countries.(11) However, the high cost of the initial
installation of the system is compensated for by its low cost of maintenance and the
good outcomes obtained when ECMO support is used with adequate staff training,
making this therapy cost-effective in developed countries(9,12) and
potentially cost-effective in developing countries.(13)
Considering that ensuring the availability of appropriate staff in health centers
with a relatively small occupancy rate may increase the cost of extracorporeal
support, ECMO-equipped transport to specialized centers has been made available at
an acceptable cost, with high survival rates and improvement in the quality of
life.(4,9)
Considering the importance of transport with ECMO, the objective of this study was to
characterize the transport performed by our team in the State of São Paulo
since 2011.
Statistical analysis
The data were considered nonparametric because of the small sample size and are
reported as the median [25th - 75th
percentile] if quantitative and as the number of occurrences and
percentages if qualitative. The comparisons between the groups presented in the
tables were performed using the Mann-Whitney test for quantitative data and
Fisher's exact test for qualitative data. The confidence interval of the
survivor ratio was calculated according to the method described by the
Association of Public Health Observatories(21) using R software for calculations and graph
creation.(22)
RESULTS
The ECMO program was initiated in 2011, and the transport of ECMO patients began in
the same year.(14) A flowchart of
the 28 requests for extracorporeal support outside the referral hospitals is shown
in figure
1S. The first seven patients in this series were
described in another publication.(15) During the six years of the program, 18 patients in the state
of São Paulo were rescued and transported with ECMO support by our team.
Seventeen patients received exclusive respiratory support (veno-venous - VV
configuration), and one patient received respiratory and cardiovascular support
(veno-arterial - VA configuration). A profile of the patients is shown in table 1. The characteristics of the patients
shortly before initiation of the support are shown in table 2. The Respiratory ECMO Survival Prediction Score (RESP
score) and the tidal volume in pre-ECMO mechanical ventilation differed
significantly in survivors and nonsurvivors. The data on the rescue missions and
complications during transport are shown in table
3. The referral hospitals were Hospital Sírio
Libanês (two patients), Hospital TotalCor (two
patients), and the Hospital das Clínicas of São Paulo
(14 patients).
The data on the extracorporeal support are shown in table 4. Respiratory support was provided using the femoral-jugular
configuration, and veno-arterial support (one case) was provided using the
femoral-femoral configuration. The venous cannulae were 21 - 22 Fr, and the arterial
cannulae were 16 - 19 Fr. Apart from veno-arterial cannulation, anticoagulation was
started upon patient arrival at the referral hospital. Five patients did not use
anticoagulation at any time because of pulmonary hemorrhage (four cases) or the
presence of cerebral vasculitis with hemorrhagic areas (one case). None of the
evaluated patients had a change of itinerary or a change in the support
configuration related to initial cannulation. The final results are shown in table 5. The minimum and maximum duration of
support was 3 and 60 days, respectively. Of the 18 patients, 13 (72%, 95%CI 49 - 88)
survived to hospital admission (Figure 2S). Of the survivors,
only one patient needed dialysis after hospital admission, and none required home
oxygen therapy. The individual patient data are presented in
table
1S.
DISCUSSION
In this case series of 18 severe patients transported to specialized centers with
ECMO support in São Paulo, the rate of complications was low, and hospital
survival was 72%. Of the patients who were discharged from the hospital, only one
needed renal replacement therapy, and none required home oxygen therapy.
Fewer than 2% of the patients admitted to the intensive care unit (ICU) suffered from
severe respiratory failure. Of these, fewer than 0.5% were refractory to protective
mechanical ventilation and salvage therapy for hypoxemia and severe
hypercapnia(23) and
sometimes required ECMO support. The low rate of very severe patients limits the
ability to maintain a team to perform ECMO support in all ICUs. Therefore, in
developed countries, transport with installed ECMO support was used to reduce the
risk of transportation to specialized centers, and the patient survival rate was 62%
(95%CI 57 - 68%).(4,15) In our series, hospital survival was 72% (95%CI
49 - 88%), in agreement with the data reported in the literature.(15)
These results are attributed to two main causes. The first is the use of more
rigorous inclusion and exclusion criteria, which resulted in restricting the use of
ECMO to highly selected patients because ECMO support seems to have a survival
benefit with improved quality of life for patients with few comorbidities and few
acute dysfunctions.(9,24) In addition, the application of
rescue therapy, such as the use of the prone position before ECMO, is essential
whenever possible because this therapy is inexpensive and there is strong evidence
that its use improves patient survival.(25) Second, the use of ECMO support can be optimized by
providing adequate training and experience to the multidisciplinary team(18) and by the involvement of
professionals who possess comprehensive knowledge of emergency care and possible
complications during ECMO support.(26-28)
In our study, the comparison of survivors and nonsurvivors should be considered
preliminary because of the small sample size. However, certain factors should be
considered. The initial tidal volume of the patients who died was lower than that of
those who survived, suggesting greater severity of lung injuries and poorer lung
compliance in the former. The Simplified Acute Physiology Score 3 (SAPS 3) did not
differ in the two groups, and the RESP score,(29) which was used in decision-making, was higher in
survivors. Although the RESP score was developed as a means of predicting patient
survival under ECMO support, other scores that were developed to predict patient
survival better address other organic functions and may therefore be more
accurate.(30) The Survival
After Veno-Arterial ECMO Score (SAVE score) was described, but the effects of using
this score were not analyzed because it was used in only one case.
Another relevant factor in our sample of nonsurvivors was that the partial pressure
decrease in carbon dioxide (PaCO2) from pre- to post-ECMO was critical.
This characteristic is known to be related to higher patient mortality in
ECMO.(31) This factor may
have contributed to the deaths of two patients who progressed to brain death while
in the ICU. This outcome alerted us to the importance of the careful initiation of
extracorporeal ventilation, especially in hypercapnic patients with gas/blood flow
< 1, to ensure a smaller initial decrease in PaCO2.
The most serious problems that arose during transport were addressed as follows. (1)
Energy failure was avoided by using a hand pump for one patient and by turning off
the warning lights for another patient, and the ambulance power inverter was
dedicated to the operation of the pump. (2) Only decreases in oxygen saturation <
85% and > 70% were observed. These dessaturations occurred because of the
severity of lung injury, associated with a cardiac output. Severe hypoxemia may
occur during the acute phase of respiratory support and sometimes needs to be
tolerated by the team;(32)
although this complication may not directly affect survival or cognitive outcome, it
indicates the severity of the patient's condition.(33)
Although the sample described in this study does not provide new data, it represents
the first case series of patients transported in ECMO in Brazil. However, the
results of this study should be viewed with caution for several reasons. First,
because the sample size was small, it was not possible to perform a multivariate
analysis. Second, the results of the analyses are preliminary and should not be used
to change procedures at the bedside. Third, generalization of the results reported
here to other centers should be made with caution because the number of ECMO support
cases per year was low (5 - 10). Fourth, the indications were restricted to a small
subset of patients.
Under certain conditions, ECMO can be an effective and cost-effective therapy. The
results of this case series demonstrate that this approach can be effective when
restrictive indications are followed, adequate intensive care is provided to avoid
complications during hospitalization, and the staff involved in patient care are
continuously trained to enable them to treat life-threatening complications that may
occur during ECMO support. In our opinion, this can only be achieved in a few
centers while maintaining the cost-effectiveness of therapy.
CONCLUSIONS
Transport of severely ill patients with extracorporeal respiratory support in a
Brazilian state was feasible and did not result in severe complications. Despite the
small sample size, patient survival to hospital admission was similar to that
reported in the literature.