INTRODUCTION

Extracorporeal Membrane Oxygenation (ECMO) is considered a form of mechanical cardiopulmonary support. It is used in the treatment of severe respiratory failure, heart failure, or both ¹. Initially, this technique was developed to be applied solely during cardiac surgery. However, nowadays, its application has been extended to intensive care. ECMO is currently used as a rescue technique - it can be employed in extreme cases of ARDS (Acute Respiratory Distress Syndrome) which are refractory to conventional ventilation techniques, or even during Cardiorespiratory Arrest (CRA), being named Extracorporeal Cardiopulmonary Resuscitation (ECPR). Certain studies demonstrate that ECPR is more effective than conventional Cardiopulmonary Resuscitation (CPR). According to a document written by the Extracorporeal Life Support Organization (ELSO) ^2)(3)(4, only 28% of the ECPR procedures performed in adults are effective. Nevertheless, the same document highlights that ECPR is associated with a better survival rate, due to various modifiable and non-modifiable factors, such as adequate pre-ECPR resuscitation, efficient implementation of the extracorporeal support and adequate patient selection ^{2)(3)(4)(5)(6}.

The ECMO technique consists of extracting the blood from the body, by means of several cannulae, which are placed in central veins. The extraction is achieved using a mechanical pump - the oxygenator - that also performs the necessary gas exchanges when the blood passes through it, removing carbon dioxide and adding oxygen. After the gas exchanges, the blood returns to the body, by means of other cannulae, inserted in central arteries or central veins, depending on the ECMO modality ¹⁾⁽⁸.

The patient's physiological needs dictate whether the ECMO will perform cardiopulmonary support, or simply pulmonary support. In the first case, it is preferable a veno-arterial (VA) cannulation - extraction of the blood through a vein, usually a femoral vein, followed by the return of the blood through an artery, generally the femoral artery. If the patient only requires pulmonary support, a veno-venous (VV) cannulation is preferred, because, in that case, the ECMO functions as an artificial lung. The patient's heart ensures blood circulation, while blood oxygenation is carried out externally, by the oxygenator, allowing the lungs to rest ⁴⁾⁽⁹.

It should be noted that, like all invasive procedures, ECMO is associated with adverse events, such as clot presence and/or formation, gas embolism, and/or failure of the oxygenator during the technique's execution. Additionally, it has also been reported that patients subjected to ECMO can experience clinical complications, due to interactions between the blood and the circuit's artificial surfaces, as well as changes in blood flow patterns. The prolonged use of the technique has also been related to a greater number of complications. Nonetheless, it is important to stress that the results reported in literature reveal the existence of a reducing factor for all these adverse events, which affects their incidence, their severity, and the consequences of possible mechanical complications - the presence of a team specialized in ECMO, composed of physicians and nurses with appropriate experience and training. These professionals provide daily care to the patients who are subjected to ECMO. Their knowledge allows a more accurate prediction of errors, as well as a care directed both to the patient's needs and to the technique's demands ^{4)(5)(10)(11)(12}. When we were faced with the abovementioned considerations, the following research question emerged: What is the nurses' approach to the critically ill person subjected to ECMO? The present study - through a content analysis using the Scoping Review methodology based on the principles recommended by the Joanna Briggs Institute - aims to map the available scientific evidence about the nurses' approach to the critically ill person subjected to ECMO.

MATERIALS AND METHODS

This study portrays a scoping review, which is organized according to the structure proposed by the Joanna Briggs Institute, in "Methodology for The Joanna Briggs Institute Scoping Reviews" ¹³. Given that the synthesis of evidence, by means of systematic reviews, is at the core of evidence-based practice, there are different review objectives and review questions that require the development of new approaches. These approaches, which include the scoping review, are designed to synthesize the most effective and rigorous evidence ¹⁴. The scoping review model adopts the following main objectives: to map the existing evidence underlying a determined research area; to identify gaps in the existing evidence; and to represent a preliminary exercise that justifies and informs the execution of a systematic literature review. The greatest and most significant particularity of this model is that it not only analyzes the methodological quality of the included studies, but also maps the existing scientific evidence contained in them ¹³⁾⁽¹⁴.

The research question was formulated using the "Population, Concept and Context" (PCC) strategy: the "Population" consisted of critically ill adult patients (ages between 18 and 64 years old); the "Concept" corresponded to the nursing care provided to those patients when subjected to ECMO; the "Context" was not applicable in this particular case.

The following inclusion criteria were established, in order to guide the literature's search and selection according to the intended results and the formulated question: samples consisting of critically ill adult patients (ages between 18 and 64 years old); studies that referred to nursing interventions applied to patients subjected to ECMO; articles available in full text and free of charge, published between June 2009 and June 2019, and written in Portuguese, Spanish, or English. These criteria are summarized in Table 1.

Table 1 -  Inclusion criteria. 

Studies published in other languages, as well as those that referred to interventions performed without the participation of nurses, were excluded. The purpose of the ten-year time span, ending in 2019, was to identify the most recent scientific evidence.

Two researchers carried out the search and selection process. The search strategy encompassed only published studies and consisted of a three-step search. An initial survey was executed using the EBSCO Host Research Platform, with the following databases selected: CINAHL Complete, MEDLINE Complete, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Cochrane Methodology Register. This was followed by a search for these specific words in the titles, abstracts and descriptors: "nursing interventions", "extracorporeal membrane oxygenation", and "critical patient". Subsequently, a second survey was performed, using all the previously identified keywords and descriptors in the selected databases. Finally, some of the references found in the identified articles were analyzed to identify additional studies. The search was conducted in June 2019, using the referred search terms, the Boolean operator "AND", and the previously mentioned PCC strategy components.

The preliminary search results were evaluated and sorted according to their suitability for inclusion, considering only the information available in the respective titles and abstracts. Afterwards, the selected studies were read in full, before their integration into the final sample. The level of evidence and the grade of recommendation were classified according to the "New JBI Levels of Evidence" ¹⁸, which allowed to preliminarily appraise the methodological quality and the accuracy of the evidence found in those works ¹⁷⁾⁽¹⁸.

Both researchers, acting as independent reviewers, also conducted the critical evaluation, extraction and synthesis of data. Concerning the critical evaluation, it was ensured by reading the studies, as well as by assessing their methodological quality through the JBI instrument "Checklist for Diagnostic Test Accuracy Studies" ¹⁹, during the article selection process. Due to some disagreements between the reviewers, the evaluation of a third reviewer was requested. In the end, a consensus was reached - all studies were considered to present high quality and, therefore, none was excluded. Data extraction was carried out by interpreting the articles and highlighting the results that better conveyed an answer to our research question. Last, but not least, we performed a synthesis of the obtained knowledge with respect to the care provided by nurses to critically ill adult patients subjected to ECMO. This synthesis was carried out using an instrument adapted from the one proposed in "The Joanna Briggs Institute Reviewers' Manual: 2015 edition" ¹³.

RESULTS

Through our initial database search, we identified 23 studies that were in agreement with the various key concepts. One of the studies was excluded through the search limiters because it was a duplicate. Of the remaining 22 articles, five were rejected after reading the title, because they did not correspond to research studies and/or only addressed ECMO as a technique. Of the remaining 17 studies, after reading the full text, 12 were excluded because they did not pass the methodological quality assessment and/or did not fully meet the inclusion criteria. The remaining five articles were considered relevant, because they referred to nursing interventions/programs within this work's scope, and were thus included in the review. Figure 1 illustrates this selection process.

Figure 1 -  Flowchart of the process used to select the studies 

Table 2 lists the five studies ^{4)(5)(6)(9)(10} - identified as A1 ⁴, A2 ⁹, A3 ⁵, A4 ⁶ and A5 ¹⁰, respectively - that were included in the review after the selection process, specifying their author(s), the year in which they were published, the research design used in each one, the characteristics of the studied population, and the level of evidence according to the "New JBI Levels of Evidence" ¹⁸. It can be observed that the research efforts are dispersed in time (from 2011 up to 2018) and the ensuing works are essentially of a qualitative nature. Studies A2, A3 and A4 present a "Literature Review" modality and, regarding the level of evidence, were therefore categorized as "Level 4.a" (systematic review of descriptive studies) ¹⁸. On the other hand, A1 and A5 present a "Case Study" modality and were thus categorized as "Level 2.d" (pre-test/post-test, or historical/retrospective, control group study) ¹⁸. With respect to the studied populations, the latter studies resorted to adult individuals who had been subjected to the ECMO technique at some point in time.

Table 2 -  Studies included in the review, organized by year of publication, research design, studied population, and level of evidence. 

Table 3 displays the previous articles according to the studies' purpose, the relevant nursing interventions under analysis, and the main conclusions that were reached. These findings will be subsequently discussed.

Table 3 -  Studies included in the review, organized by purpose, nursing interventions and main conclusions. 

DISCUSSION

The results of this review highlight the nurses' approach to the critically ill patient subjected to ECMO. Although the number of included articles constitutes a small sample, the latter is consistent with the proposed framework. The studies are essentially of a qualitative nature, as stated previously, and exhibit results that are transversal to several practice contexts. Nonetheless, it is noticeable a low geographic variety, since the selected studies were mainly conducted in North and South America.

Our findings show that ECMO is a highly complex technique that also entails high costs. It requires several resources, namely adequate material, a laboratory, technologyical equipment and trained professionals ⁴.

The nurse's approach to the critically ill person subjected to ECMO is perceived as essential to the success of the overall process. It is this professional's responsibility to always be there for the patient, as well as to monitor, supervise and prevent complications ^4)(5)(9, while managing and coordinating the provision of care ¹⁰.

The monitoring task encompasses two facets: (i) monitoring the ECMO technique, namely cannulae care procedures, oxygenator output, oxygenator rotations, oxygenator pressures, oxygenator gasometry, circuit temperature, and coagulation index; (ii) monitoring the patient, which involves the assessment of vital parameters, capillary glycemia, neurological system, diuresis, hematic losses, positioning, and ventilatory and gasometric parameters ^4)(5)(6)(10. At the same time, the support and care provided to the ECMO patient's family is also relevant in the overall care process ^4)(5)(6)(10.

On the subject of the ECMO technique's monitoring, circuit care stands out, particularly with regard to cannulation sites and the integrity of the cannulae themselves ⁴⁾⁽⁶.

With respect to care management, the importance of checklists for the standardization of care, as well as the daily control of all the abovementioned interventions, is highlighted ¹. Such interventions contribute to the standardization of procedures, the establishment of good practices and the improvement of the care provided to critically ill patients subjected to ECMO ⁴⁾⁽⁹.

Nursing professionals who provide care to ECMO patients should be experts ⁶⁾⁽¹⁰.However, the authors argue that, in order to achieve full expertise, nurses need appropriate training, as well as supervised experience, so that they are able to identify the individual's needs and, consequently, to plan specific interventions ⁶⁾⁽¹⁰. It is through this skill acquisition methodology that the professional may become aware of his/her weaknesses regarding the provision of care to critically ill ECMO patients. Continuous training, theme-based discussion within the multidisciplinary team, training the procedure with more experienced professionals and the implementation of protocols based on scientific evidence are decisive tools for an effective, safe and high-quality approach to ECMO patients ⁹⁾⁽¹⁰.

In addition to the above, the literature is consensual on the importance of communication to the technique's success. In this regard, inter-team communication is highlighted - namely with the attending physician, about the person's condition and care planning ^6)(9)(10.

This relatively recent topic in Nursing literature is emerging in health care, due to its growing implementation in the context of critically ill patients ⁷.

The limitations of this study relate to the fact that most of the results obtained in the review focus on medical experiences, and also the fact that nursing literature is scarce.

That scarcity stresses the importance of continuing to conduct primary research in this particular field.

CONCLUSION

This study made it possible to understand the existing scientific evidence with respect to the nurses' approach to critically ill adult patients subjected to ECMO. According to the reviewed studies, we found that ECMO is considered an increasingly present technique in the care provided to critically ill patients that require mechanical cardiopulmonary support, due to severe respiratory failure, heart failure, or even both conditions.

As health professionals, nurses have the responsibility to monitor, supervise and manage all the care provided to critically ill individuals subjected to ECMO, in order to prevent any issues. Nursing teams are in a particularly privileged position to observe, intervene and anticipate complications, either related to the technique itself, or to the patient's adaptation. In this context, benefits have been obtained through the implementation of protocols, since they help nurses to standardize care and, thus, ensure a safe, correct and targeted intervention.

Additionally, to achieve the successful application of the ECMO technique, it is fundamental to guarantee an effective communication within the multidisciplinary team, as well as to provide training to its members. These aspects have a decisive influence on the practice, leading to a faster, more assertive and confident approach, since an adjusted communication and the acquisition of up-to-date practical and scientific knowledge ensure the provision of high-quality care.

Further research on this matter is required and supported by the need for an evidence-based practice. Therefore, we consider that this topic should continue to be a subject of discussion and debate within the scientific community.