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Characterization of patients transported with extracorporeal

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.