Background

While people of all ages receive emergency and critical care services across the world, the elderly population continues to exhaust a greater proportion of these services [1]. The complexity and acuity of care have heightened with greater prevalence of chronic illness and multimorbidity among older adults [2]. Correspondingly, the demand for emergency and critical care services has increased [1], alongside a concomitant increase in the forecasted workforce requirements for such services [3]. The Accreditation Council for Graduate Medical Education regulations in 2006 in the United States of America (USA) recommends a high-intensity model of care involving 24-h physician coverage [3, 4]. This implementation accentuates inadequacies of the healthcare workforce to provide emergent and critical care services. In the USA, it is predicted that, compared to healthcare system’s demands, there will be a 22% shortfall of critical care physicians by 2020 and a subsequent 35% shortfall by 2030 [1].

With the impending rise in demand for health services, an effective utilization of the workforce is paramount to ensure high-quality yet cost-effective health service delivery [5]. Across some countries, healthcare workers’ wages account for approximately 50% of the total healthcare expenditure [6]. Hence, cost containment strategies will inevitably involve the workforce [7]. Efforts are underway for measures to enhance productivity through increasing the capacity of the workforce.

One potential measure is a greater utilization of nurses in advance practice. The global annual growth of the nurse practitioner (NP) workforce has been estimated to be between three to nine times greater compared to physicians; therefore, of interest to health policymakers is the utilization of NPs and advanced practice nurses (APNs) [8, 9]. The nomenclature varies internationally. The “NP” title is used in Australia, Belgium, Canada, Sweden, the United Kingdom (UK), and the USA whereas the “APN” title is used in Switzerland, Singapore, and South Korea [10]. Nonetheless, NPs and APNs (NP/APNs) are registered nurses “who acquired the expert knowledge base, complex decision-making skills and clinical competencies for expanded practice” ([4], p. 26) and enter the workforce with a master’s degree [11].

This advanced practice role was first introduced in the 1960s as a solution to the lack of primary care physicians, to meet the primary care needs of the rural and underserved populations [12]. Primary care has first contact with patients and, subsequently, provides continuity of care within the healthcare system through the coordination of care according to patients’ needs [13]. Studies to evaluate the quality of primary care provided by NP/APNs have been shown to be comparable to that of physicians in terms of effectiveness and safety [14]. To fulfill primary care needs, NP/APNs in this setting are trained generalists who have a breadth of knowledge to render a wide scope of care.

Since the inception of advanced nursing practice in primary care, its role has extended to other healthcare settings such as the acute care. Acute care provides short-term restorative stabilization to patients in unstable chronic conditions and with complex acute and critical illnesses. Acute care encompasses emergency and critical care [15]. Emergency and primary care advanced nursing practice do share similarities in that they serve as first-contact access to healthcare, but the acuity of the patient manifestations delineates the two. Unlike in primary care NP/APNs, emergency NP/APNs are trained to manage patients with acute life- or limb-threatening conditions [15]. In the past decade, greater practice autonomy has been given to NP/APNs in emergency and critical care. This expanded practice allows nurses to assume some medical tasks typically performed by physicians, aiming at not only increasing the access to healthcare and service efficiency but also eventually mitigating the cost of health services.

The development of advanced nursing practice contributed to a service model aiming to respond flexibly to the ever-changing needs of patients [16]. Systematic reviews of studies on the effectiveness and safety of NP/APN-led primary care have reported positive effects of NP/APN service on clinical outcomes, patient satisfaction, and costs [14, 17] These reviews focused on the primary care setting, it may be inappropriate to extrapolate their findings to the emergency and critical care settings since the patient acuity and clinical needs differ among settings.

Nonetheless, reviews evaluating NP services in the emergency and critical care settings exist. However, they have three shortcomings, the first of which concerns their generalizability. Over the past decade, studies have evaluated whether the delegation of medical tasks to NP/APNs in the emergency and critical care settings was feasible and safe. A review of 31 studies on the impact of NPs and physician assistants in such settings reported that their practice was safe and, in some cases, the quality of care was higher than that of physicians [18]. However, only two of the studies were randomized controlled trials (RCTs) [19, 20] whereas the rest had small sample sizes and questionable study methodology; these limit the generalizability of the review. A more recent review [21] also reported that NPs do have a positive impact on the quality of care. Nonetheless, the reviews included both NPs and non-nursing healthcare providers, thereby introducing heterogeneity in the synthesis of evidence, making it difficult to assess the true effect of NPs in the intensive care settings [18, 21].

The second shortcoming centers on the inconclusiveness of the reviews. One review suggested although NP services in the emergency setting did reduce waiting time and provide care comparable to that of a midgrade physician, the cost of NP services was higher than that of resident physicians [22]. In contrast, another review concluded that the use of NPs reduced the cost of emergency and intensive care services. Further complicating the picture is a recent systematic review that reported an inadequacy of evidence to determine the cost-effectiveness of NP services in emergency departments (EDs) [23]. Consequently, the cost-effectiveness of advanced nursing practice in the emergency and critical care settings has remained inconclusive. Lastly, all existing reviews [18, 21,22,23] elucidating advanced nursing practice in the emergency and critical care settings included only studies published before January 2013, which may be dated.

Considering the existing literature, it is of interest to undertake an updated systematic review on the latest evidence to determine whether advanced practice nursing in emergency and critical care have an impact on the quality of care, clinical outcomes, patient satisfaction, and cost savings. If NP/APNs can indeed provide competent and safe care in these settings, greater access to emergency and critical care services will be available, thereby strengthening the workforce to fulfill the escalating healthcare demands.

Therefore, the main objective of this systematic review is to present, critically appraise, and synthesize the best available evidence on the impact of advanced nursing practice on patients’ length of stay, time to treatment or consult, mortality, patient satisfaction, and cost in emergency and critical care settings.

Methodology

Design

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adhered to in the conduct and reporting of this systematic review [24].

Study selection

Published studies and studies which have yet to be published were searched using PubMed, CINAHL, The Cochrane Library, Scopus, Embase, Web of Science, ScienceDirect, Wiley Online Library, and ProQuest Dissertations and Theses Global databases from January 2006 up to September 2016. Only English studies were considered. The search strategy included the keywords, as shown in Table 1, in various combinations for a systematic database search. The search terms and search strategies for each database are included in Additional file 1. The reference lists of all identified studies were also screened. Corresponding authors were contacted for additional information where necessary.

Table 1 Summary of the themes and key words employed in the systematic review
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Study eligibility

This review included RCTs, quasi-experimental studies, prospective and retrospective cohort studies. Cross-sectional studies and studies without comparison groups were excluded.

The PICO (Population-Intervention-Comparison-Outcome) framework guided the selection process [25]. This review considered studies that included the following:

  • Patients: at least 16 years of age, presenting in EDs, trauma centers, intensive care unit (ICU), or high dependency units, requiring emergency or critical care

  • Nurses: registered nurses in advanced practice role, i.e., APNs or NPs

  • Physicians: emergency physicians, intensivists, residents, medical officers, hospitalists, or house officers in the ED or ICU or high dependency units

Excluded from the review were studies that examined both adult and pediatric patients requiring emergency or critical care services. Excluded from the review were also studies that examined services provided by physician assistants. This review included studies with interventions which compared the outcomes of the APN-/NP-directed emergency or critical care services with those of the physician-directed care. This review also included studies with interventions which compared the physician-only model of care with APN-physician or NP-physician collaborative model of care.

Studies that had the following outcome measures were included:

  • Patients’ length of stay in the emergency or critical care setting

  • Patient mortality

  • Time to consultation or treatment

  • Patients’ satisfaction

  • Cost of care

The selection of studies was done independently by two of the authors (BW and JL) based on the eligibility criteria. Disagreement during selection was resolved by discussion with a third-party arbiter (WT). The selection process is illustrated in the flow diagram in Fig. 1.

Fig. 1
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Systematic review search flow diagram

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Data extraction

Data was extracted by one author (BW) and crosschecked by another (JL) for accuracy. Resolution of disagreement was done by discussion with a third-party arbiter (WT). The Joanna Briggs Institute’s (JBI) “Data Extraction Form for Experimental/Observational Studies” [26] was adapted to tabulate the characteristics and findings of the studies.

Quality assessment

Two authors (BW and JL) performed the methodological quality assessment independently, based on the “JBI Critical Appraisal Checklist for Randomized Controlled Trials,” and “JBI Critical Appraisal Checklist for Cohort Studies” [21]. The RCTs were assessed for their randomization methods, treatment allocation, concealment of treatment groups, and homogeneity of the participants’ baseline demographics upon entry of the study. In addition, all studies were appraised for their control of confounding factors, reliability of outcome measures, and suitability of statistical analyses. For this review, a low methodological quality refers to a score assigned to a study of less than 40%, a medium quality refers to one between 40 and 70%, and a high quality refers to one greater than 70%. The findings of any systematic review are only as reliable as the primary data source, upon which the review is based [27]. Hence, studies rated to have low methodological quality (see Additional file 2) were excluded to avoid potentially erroneous conclusions based on the synthesis of poorly conducted studies.

Synthesis

Given the heterogeneity of the interventions and findings in the studies, no meta-analysis was performed. Instead, a narrative synthesis of the studies was done: the analysis was conveyed in prose, alongside tables to outline and explain the results.

Results

Study characteristics

This review included 15 studies with 23 681 participants across five countries including Australia [28,29,30], Canada [31, 32], New Zealand [33], UK [34], and USA [35,36,37,38,39,40,41], where the nomenclature for nurses in advanced practice was “NP.” A total of 14 studies [28,29,30,31,32,33,34,35,36,37,38,39,40,41] were published while one was an unpublished manuscript (Roche T, Gardner GE, Jack L: The effectiveness of emergency nurse practitioner service in the management of patients presenting to rural hospitals with chest pain: a multisite prospective longitudinal nested cohort study. In preparation.) at the point of the search. The previously unpublished manuscript was subsequently published in 2017 [42]. All included studies were conducted between 2006 and 2016. As regards the setting, six studies [28,29,30, 32, 33] focused on the EDs, six [31, 34, 35, 37, 38, 41] on the ICU, two [36, 40] on the trauma centers, and one on the stroke center [39]. The sample sizes ranged from 103 [31] to 9066 [38]. The characteristics of the studies are detailed in Table 2.

Table 2 Characteristics of study
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Methodological quality

The assessment details of each study’s methodological quality are presented in Table 3. In this review, only three studies were RCTs [29,30,31] whereas 12 were cohort studies [28, 32,33,34,35,36,37,38,39,40,42]. The included studies had low to medium risk of bias.

Table 3 Summary of methodological quality of included studies
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In two of the three RCTs, true randomization was used to assign patients to study groups by using computer-generated sequence, thus incurring only low risk of selection bias. In the other RCT, a triage coordinator was present to randomly assign the patients at a planned ratio to either NP-directed care or physician-directed care. Two of three RCTs, took measures to blind the outcome assessors to treatment assignment, minimizing detection bias. Out of the 15 studies, 14 measured their outcomes in a reliable and valid manner using pre-decided criteria, minimizing reporting bias. The presence of confounding factors was acknowledged in 11 of the 12 cohort studies but only five of them described strategies to deal with it. All the included studies fared poorly in reducing attrition bias. Only three of the 15 studies had complete follow-up or strategies to address incomplete follow-up. Appropriate statistical analyses were chosen in all included studies.

Findings

The study results and statistical conclusions are summarized in Table 4. The details of the individual studies can be found in Table 5. The findings were categorized according to the studies’ setting. Studies conducted in emergency and critical care settings measured outcomes such as length of stay, waiting, and patient satisfaction. Outcomes such as mortality and cost were measured only in the critical care setting.

Table 4 Summary of study results and statistical conclusions by outcome
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Table 5 Findings of studies
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Emergency setting

Length of stay

Four out of the 15 studies examined the impact of the advanced nursing practice roles on the length of stay in the emergency setting [28, 32, 33, 42].

NP-directed management of care

Two studies [28, 33] reported a significant reduction in the length of stay in EDs of patients who were reviewed and treated by NPs when compared to those seen by physicians. However, the shorter time was attributed to the baseline difference in patients’ acuity between the groups. The physicians handled patients of higher acuity and complexity than NPs. On the contrary, a multisite study [42], with comparison groups of similar baseline patient acuity, found comparable lengths of stay in EDs when patients with chest pain were managed by either NPs or physicians.

Length of stay in collaborative care involving nurse practitioners

One study [32] compared NP-physician collaborative model of care with usual physician-only model of care and found similar lengths of stay in ED between the comparison groups.

Waiting time

Of the 15 studies, six studies [28,29,30, 32, 33] examined the impact of advanced nursing practice roles on waiting time in the emergency setting.

Time to consultation

Only one study [33] reported that patients with minor injuries experienced shorter waiting time (median 14 min) when reviewed by emergency NPs than those reviewed by physicians (median 50 min). The other three studies [28, 30] comparing NP-directed care with physician-only care found similar waiting time to consultation in EDs. Another study [32] comparing the NP-physician collaborative care with physician-only care also found similar waiting time to consultation in EDs.

Time to treatment

One RCT [29] illustrated that a greater proportion of patients (15.4%) managed by emergency NPs received analgesia within 30 min of arrival at the ED compared to patients managed by physicians (1.6%) (P < 0.001).

Patient satisfaction

Of the 15 studies, two examined patient satisfaction in the emergency setting [30]. The two used previously validated questionnaires to measure patient satisfaction. One of which [42] found similar patient satisfaction scores when comparing NP-directed care with physician-only care while the other [30] reported NPs to receive higher patient satisfaction scores than physicians (NP median score 23 [IQR 20–24] vs. physician median score [IQR 16–24]; P = 0.002).

Critical care setting

Length of stay

Seven out of the 15 studies examined the impact of the advanced nursing practice roles on the length of stay in the critical care setting [31, 35,36,37,38, 40, 41].

NP-directed management of care

Comparable lengths of stay in a trauma center was reported in one study [40] where the comparison groups had similar baseline patient acuity. A RCT [31] conducted in a post-cardiac surgery unit where patients required critical care found comparable lengths of stay in hospital between the comparison groups (NP-directed care versus physician-only care). Despite the higher acuity of care required by patients under NP-directed care than those under physician-only care, the discharge outcomes were similar. In addition, a large cohort study [38] reported a significantly shorter length of stay in medical ICUs for patients whose management were led by NPs than those under physician-only management. Patients in the NP-directed group also had lower odds (odds ratio 0.87, P < 0.001) of longer hospital stays. Interestingly, a higher patient-to-provider ratio was observed in the NP-directed group but the authors [38] were judicious in inferring greater efficiency in NP-directed care given the differences in the patients’ characteristics between comparison groups.

Collaborative care involving nurse practitioners

All included studies that compared NP-physician collaborative model of care with usual physician-only model of care found similar lengths of hospital stay [35,36,37, 41] between the comparison groups. However, in one study [36], after subgroup analysis, a significantly shorter length of stay was found in the physician-NP collaborative group for patients transferred from another service (mean difference 6.54 days, P < 0.0001), patients discharged to rehabilitation facility (mean difference 2.63 days, P = 0.0024), patients older than 60 years (mean difference 1.80 days, P = 0.0369), or patients discharged on intravenous antibiotics/wound therapy (mean difference 3.93 days, P = 0.0171). The management of such patients warrants greater communication with multidisciplinary teams, discharge planning, care coordination, and administrative work were required; in this niche, NPs are familiar with such tasks and can competently perform them [43].

Waiting time

Time to treatment

Only one study [39] examined the impact of advanced nursing practice roles on waiting time in the critical care setting. The study [39] demonstrated that a 24/7, on-site coverage with an acute care NP as first responders for acute ischemic stroke significantly reduced the time to treatment (median 45 min; IQR 35–58 min) in comparison to the usual service model (median 53 min; IQR 45–73 min) (P < 0.001).

Mortality

Five [34, 37,38,39, 41] out of the 15 studies analyzed the impact of the advanced nursing practice roles on hospital and ICU mortality. Two studies [38, 39] comparing NP-directed care with physician-only care found comparable patient mortality. One of them, a large cohort study (n = 9066) conducted in the medical ICU [38], suggested NP-directed care had the same quality as physician-only care. The patients under NP-directed care had lower ICU mortality (6.3%) than those under physician-only care (11.6%; adjusted OR 0.77; 95% CI 0.63–0.94; P = 0.01) whereas hospital mortality between groups were similar (10 vs. 15.9%; adjusted OR 0.87; 95% CI 0.73–1.03; P = 0.11). This finding was consistent with that in the other three studies conducted in ICUs [34, 37, 41] which compared the NP-physician collaborative care with physician-only care.

Patient satisfaction

Of the 15 studies, only one examined patient satisfaction in the critical care settings [31]. The study developed a new self-reported tool to measure patient satisfaction and found similar scores when comparing NP-directed care with physician-only care. Nonetheless, the study [31] reported that NPs performed better than physicians in teaching, answering questions, listening, and pain management. This finding was akin to the study [30] conducted in the ED which assessed the healthcare provider for completeness of care, politeness of service provider, explanation and advice given, waiting time, and comprehension of discharge instruction.

Cost

Three of the 15 studies reviewed the impact of the advanced nursing practice roles on cost [34, 36, 41], all of which compared NP-physician collaborative care with physician-only care in the critical care setting. One study [41] reported that despite a longer ICU stay for patients in the NP-physician group than for those in physician-only group, there was no significant difference in the observed charges between them. This supports the contention that involving NPs in the management of the critically ill can lead to cost savings. The other two studies [34, 36] had results that demonstrated cost savings in the NP-physician group compared to physician-only group. One of them concluded that an annual staffing cost of approximately £170 000 could be saved when physicians worked with NP in managing ICU patients.

Discussion

With population aging and the consequent global epidemic of chronic diseases, healthcare demands will only rise. Accordingly, nurses in advanced practice can add value and increase access to healthcare by, potentially strengthening the healthcare workforce. Nonetheless, the expansion of role and autonomy of nurses will lead to concerns of patient safety and clinical outcomes. Through the narrative synthesis of the available evidence from Australia, Canada, New Zealand, UK, and USA, nurses in advanced practice appear to generate clinical outcomes comparable to those of physicians in the emergency and critical settings.

Generally, in the ICU setting, the involvement of NPs in managing the critically ill allowed for greater continuity of care [37], as NPs did not have to be on frequent rotation coverage as junior physicians. Hence, NPs developed greater familiarity with the environment and patient demands than the physicians who were constantly on rotation. The involvement of NPs also provided the unit’s staff with a consistent point of contact for the multidisciplinary team [35]. When daily multidisciplinary rounds were initiated by NPs, the coordination of care was shown to improve [40]. Providing effective care coordination is a forte of nurses [10]. Care coordination requires interpersonal communication and collaboration. As nurses can establish more personal and tangible relationships with patients than do physicians [44], they perform better in care coordination. The value of NPs was exemplified when the patient care required cross-disciplinary communication, discharge planning, follow-up care, and administrative work. With NPs’ involvement, patients’ length of stay was shortened [36]. Apart from delivering efficient care, nurses in advanced practice will get to develop expertise for managing specific groups of patients through assigned responsibilities [35].

One of the prioritized quality-of-care indicators in the emergency setting is the time from arrival to first assessment by physician [45]. This review has demonstrated that NPs were capable of rendering emergency care services as timely [28, 32] as, if not faster [33] than, physicians. The addition of nurses in advanced practice in the emergency settings enabled physicians to pay greater attention to patients of higher complexity and acuity, thereby, improving access to prompt emergency care.

Time to treatment is also a priority in emergency care. The time to first administration of analgesia is an important quality-of-care indicator in EDs [45]. There are national targets in place to improve this aspect of care. In Australia, New Zealand, and the USA, the national target for time to analgesia is 30 min from time of arrival [46, 47] and, in the UK, it is 20 min [48]. When compared with physicians, NPs were observed to have greater adherence to the recommended targets for administering analgesia in a timely fashion [29]. In their provision of a hybrid model of care amalgamating nursing and medical tasks, NPs are trained to perform patient assessment and, in some countries, have prescription rights. These factors contributed to a shortened time to treatment in the emergency setting for patients [29].

The experience of the patient is highly valued in the healthcare system [49]. This review showed that patients’ level of satisfaction was not dependent on whom but how the care was delivered [30, 31]. NPs were rated to perform better at patient education, answering queries, listening, and pain management than physicians [31]. These are the strengths of NPs, consistent with the NP goals and education, which are grounded in nursing [43, 50].

Cost savings are an important outcome measure in evaluating the feasibility of any new service model [51]. Findings from this review suggest greater cost savings with the implementation of the advanced nursing practice role in emergency or critical care [34, 36, 41]. However, judicious interpretation of the evidence is recommended. A fair synthesis of the cost savings in the included studies could not be performed as they had been done in different countries. The varying financial and funding models make it difficult to synthesize the findings. Furthermore, none of the studies in this review performed any cost-effectiveness analysis.

The existing evidence has demonstrated the positive impact of advanced nursing practice roles in the emergency and critical setting, it is then of benefit to examine the necessary conditions for its implementation and receptivity. According to Pettigrew et al.’s “receptive contexts for change” framework (Fig. 2), there are eight dynamically linked factors which influence the receptivity to change [52]. Three of which are especially apparent in the studies featured in this review. They are namely the presence of environmental pressure, supportive organizational culture, and managerial-clinical relations.

Fig. 2
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Receptive contexts for change framework

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Environmental pressure can be especially pivotal in creating favorable conditions for change. When considering environmental pressure, besides the entire healthcare system, the political context of the country has an integral role in defining the environment [53]. Political influence, a large environmental pressure, was evident in the studies conducted in the USA [35,36,37,38,39,40,41] and UK [34]. In the USA, the implementation of the Affordable Care Act in 2010 was a catalyst for the development of more efficient healthcare delivery models to cope with the projected influx of new patients. In the UK study [34] featured in this review, political influence was also observed. The enactment of provisional immigration laws for physicians outside of the European Union and the European Working Time Directive has make it more difficult to support safe staff-to-patient ratios in the critical care setting. The political context of the country created an environmental pressure which consequently compelled the institutions [34,35,36,37,38,39,40,41] cited in this review to capitalize on nurses in advanced practice and experiment with new models of care delivery.

The environmental pressures trigger the development of a supportive organizational culture to effect change to ease the pressure [52]. A supportive organizational culture strives to promote staff engagement [53]. Staff engagement involves autonomy to be extended, and it was apparent in the included studies. In this review, the NPs were given greater autonomy to either practice independently [28,29,30,31, 33, 34] or collaborate [32, 35,36,37,38,39,40,41] with physicians at greater extents in the emergency and critical care settings. In these studies, the institutions’ willingness to take risks and evaluate new workforce utilization strategies possibly led to the successful implementation of the advanced practice nursing role [53].

Effective managerial-clinical relations is also a crucial factor in leveraging institutional change [53]. In the study conducted in Canada [31], the authors attributed the success observed in the NP role implementation in the post-operative cardiac surgery unit to the support from and collaboration between the administrators and clinical staff. As the NP role was fairly new in the study’s [31] setting then, it was necessary to involve individuals at all levels in the NP role implementation to optimize its success [54]. One approach to facilitate effective managerial-clinical relations is through adopting a distributed model of leadership [55], which encourages collaboration between the administrators and clinical staff. The distributed leadership approach is known to be most efficacious where job roles are mutually dependent [56]. The implementation of advanced practice nursing roles in the emergency and critical care settings involves mutually dependent job roles and so will benefit from the distributed leadership approach. The distributed leadership approach utilizes a bottom-up process, where individuals working in the setting-of-interest participates in decision-making [55]. Using this approach creates the notion of co-construction, which avoids the overreliance on a dominant individual, increasing the likelihood for sustainable change [54].

The quality and coherence of policy is one factor in the receptive context framework [52] which was not discussed in the included studies but is vital in the implementation of the NP/APN role. The lack of coherent policy to define the roles and professional boundaries of advanced nursing practice can cause healthcare administrators to be apprehensive about the implementation of healthcare models where NP/APNs are given more autonomy and responsibilities [57,58,59]. State law governs advanced nursing practice and define supervisory requirements [60]. Often, the legal frameworks lack clarity on the legal accountability of physicians, should nurses under the physicians’ supervision commit errors harmful to patients [61, 62]. Professional indemnity is closely associated to legislative boundaries [63]. The successful implementation of the NP/APN role hinges on the institution of relevant regulatory frameworks and credentialing systems to guide policy implementations and educational establishments [64]. It, therefore, reiterates the importance of having coherent policies to define roles and professional independence of nurses in advanced practice.

Limitations

The meta-analysis of the outcomes was not done to present the combined effect of estimates on the impact of advanced nursing roles in the emergency and critical care settings. Yet, to perform a meta-analysis would be inappropriate as the included studies were heterogeneous in designs, interventions, and outcome measures. The heterogeneity of studies was expected as the professional boundaries of nurses differ across countries. However, a review of the impact of advance nursing practice across countries is still valuable.

A limitation in all studies is the poor definition and description of the scope of advanced nursing practice. In addition, preparatory training for nurses to assume advanced practice was rarely discussed. The level of theoretical knowledge and clinical competence of the nurses might differ across the studies; hence, the comparison might not have been fair.

Finally, despite the search across nine international databases, this review included papers in only English; relevant papers not published in English might have been omitted.

Conclusion

Capitalizing on nurses in advanced practice to increase patients’ access to emergency and critical care is appealing and beneficial. This review suggests that the implementation of the NP/APN role in the emergency and critical care settings improves patient outcomes. The transformation of healthcare delivery through effective utilization of the workforce may alleviate the impending rise in demand for health services. Nevertheless, it is necessary to first prepare a receptive context to effect sustainable change.