Emergency critical care: closing the gap between onset of critical illness and intensive care unit admission

The outcome effects of critical care interventions provided in the pre-hospital setting have mainly been evaluated in major trauma victims and patients suffering from sudden unexpected cardiac arrest. Severe trauma patients who underwent pre-hospital critical care interventions, including endotracheal intubation, chest decompression, tourniquet use, cricothyroidotomy, and advanced cardiac life support, had a lower mortality than those who did not [50]. The Head Injury Retrieval Trial suggested that critical care interventions delivered in the pre-hospital setting reduced 30-day mortality by 30% (number needed to treat, 6) in adult patients with severe blunt head injury when compared with standard ground paramedic management [51]. In a retrospective cohort study conducted in the United Kingdom, patients who experienced a sustained return of spontaneous circulation following traumatic cardiac arrest received more critical care interventions on scene than trauma victims without a return of spontaneous circulation. Delivery of bag-valve-mask ventilation, rapid sequence induction, blood product administration, and thoracostomies were independently associated with a sustained return of spontaneous circulation [52]. In a French multicentre study including 2703 blunt trauma patients, prehospital interventions delivered by a mobile critical care team (e.g., venous line, crystalloid or colloid infusions, mannitol, catecholamines, tracheal intubation, mechanical ventilation, blood products, chest tube) reduced 30-day mortality [53]. Although controversial data exist [54], prehospital intubation was associated with a lower risk of death and better functional outcome at six months compared to no prehospital intubation in patients with severe traumatic brain injury [55, 56]. The authors of a recent meta-analysis of 19 studies concluded that there is growing evidence that pre-hospital endotracheal intubation in patients with severe traumatic brain injury was beneficial if performed by well-trained, experienced providers in accordance with current guidelines [57].

In a prospective, observational multicentric study conducted in the United Kingdom, prehospital critical care interventions resulted in a higher rate of hospital admission in patients with out-of-hospital cardiac arrest compared to routine advanced life support. However, this did not translate into increased rates of survival to hospital discharge [58]. Delayed arrival of teams able to provide advanced life support at the scene adversely affected neurological outcomes at hospital discharge in adults experiencing an out-of-hospital cardiac arrest [59]. In the pre-hospital setting, even complex procedures such as veno-arterial ECMO therapy can be delivered to selected patients with out-of-hospital cardiac arrest [60]. Following first pre-hospital eCPR systems in Paris [61] and Regensburg/Germany [62], programs systematically implementing pre-hospital eCPR have reported good results with favourable neurological survival rates in 43% of patients at hospital discharge and three months thereafter [63].

Critical care retrieval or retrieval medicine are the terms used to describe the use of an expert team to assess, stabilise and transport critically injured or ill patients from one medical facility to a higher level of care [64]. The term ‘retrieval medicine’ originates from the continent of Australia, where the practice of transferring critically ill patients over long distances is common and highly developed [65]. In other regions of the world, retrieval medicine is also referred to as interhospital transfer of critically ill patients.

Several observational studies indicated that interhospital transports of critically ill patients can safely be accomplished when performed by specialized and adequately staffed critical care transport teams. In a retrospective review of inter-hospital transfers in the United Kingdom, the use of a specialist transfer team improved acute physiology of critically ill patients compared with standard ambulance transport accompanied by a doctor provided by the referring hospital [66]. Similarly, inter-hospital transfers of critically ill patients using a specialized mobile ICU transfer team resulted in less adverse technical events, less deterioration of pulmonary function [67] and a lower 24-hour mortality [68] than standard ambulance transfers. Two studies revealed that the mortality of critically ill patients requiring inter-hospital transfer was not different from non-transferred patients when the inter-facility transport was conducted by a dedicated retrieval team adhering to ICU relocation protocols [69, 70]. Specialized retrieval teams can implant extracorporeal life support systems in the referring hospital before inter-hospital transfer in patients with severe respiratory and/or cardiovascular failure who may otherwise be too unstable for transportation [71‐73], a practice likely associated with mortality benefits [74]. The ability of specially trained critical care teams to safely transport critically injured or ill patients even over long distances (e.g., during intercontinental flights) has been shown both in civilian and military settings [75‐77].

Use of specially trained paediatric critical care transport teams is of particular benefit for neonatal and paediatric inter-hospital transport [78‐80]. Such teams are considered a prerequisite for the policy of centralizing paediatric intensive care services [79]. In this context, an analysis of prospectively collected data in England indicated that paediatric ICU retrieval services often needed to stabilize critically ill children before inter-hospital transport and that the additional time required to do so was not associated with worse outcome [81].

The emergency department is the first point of contact for acutely ill patients presenting to the hospital. Aside from the ICU and operating theatres, it is also the hospital area, where most critically ill patients are encountered. Several models to provide critical care in the emergency department and improve the management of critically ill emergency patients have been published [82]. Such critical care delivery solutions substantially vary from each other and include medical emergency [83] or emergency critical care teams [84] bringing ICU staff to the ED whenever needed, ED-based early intervention teams [85, 86], ICU-led telemonitoring solutions [87], dedicated critical care resuscitation units [88, 89], and emergency physician-staffed emergency department ICUs [40, 90‐94].

Multiple studies reported that critical care delivered to critically ill patients in the emergency department (e.g., short-term non-invasive pressure support ventilation in patients with cardiogenic pulmonary oedema) can rapidly stabilize organ functions, halt or reverse progression of organ dysfunction, and avoid the need for ICU admission in emergency department patients who initially presented with critical illness [95‐97]. Importantly, the time duration critically ill patients stayed in the emergency department before ICU admission was not negatively associated with patient outcomes when appropriate critical care was delivered in the emergency department [98, 99]. The most important evidence-based benefits of critical care delivery in the emergency department are summarized in Table 2 [100]. In patients too old, frail, and/or sick to benefit from any critical care intervention, critical care delivery in the emergency department includes provision of excellent and humane palliative care [101, 102]. Identification of patient preferences in both critically and non-critically ill patients before ICU and hospital admission is another patient-centred and important aspect of critical care delivery in the emergency department. An economic analysis revealed that critical care delivery in the emergency department is cost-effective [103].

Clinical deterioration and cardiac arrest in patients on general wards are frequently preceded by physiologic derangements which can be identified with the use of scores such as the National Early Warning Score [104‐108]. These observations led to the implementation of medical emergency or rapid response systems (Fig. 4). Such teams typically consist of critical care physicians, critical care nurses, physiotherapists and/or respiratory therapists. A systematic review found no relationship between team composition and patient outcomes, but highlighted that mature and dedicated teams which required mandatory activation reported the best results [109]. Hypoxaemia (41%), arterial hypotension (28%), an altered conscious state (23%), tachycardia (19%), tachypnoea (14%), and oliguria (8%) were the most frequent alarm triggers leading to activation of the medical emergency team in an Australian hospital [110]. In a study from Portugal, fluid challenges (40.6%), bag mask ventilation (37.3%), intravenous access (29.8%), manual ventilation (20.1%), endotracheal intubation (15.7%), airway suction (13.6%), and cardiopulmonary resuscitation (12.3%) were the most common critical care interventions delivered by the medical emergency team on the ward. The median on-scene time of the team was 35 (IQR, 20–50) minutes [111]. An Italian study reported that critical care (e.g., helmet continuous positive airway pressure, pharmacological cardiovascular support) provided to critically ill haematological patients on wards allowed for stabilization and avoidance of ICU admission in one third of patients [112]. A retrospective chart review conducted in a US hospital revealed that implementation of a rapid response system was associated with an increase in do-not-resuscitate order placements. Furthermore, medical emergency team activation fostered discussions on goals of care and frequently resulted in transition to a palliative care strategy [113].

A retrospective study from a Swiss tertiary centre found that an increase in the number of medical emergency team calls from 5.2 to 16.5 per 1000 hospital admissions paralleled a decrease in cardiac arrest calls from 1.6 to 0.8 per 1000 admissions [114]. Similarly, a post hoc analysis of a cluster randomized controlled trial reported that an increasing proportion of emergency team calls was inversely related to the rate of cardiac arrests and unexpected deaths [115]. Introduction of a rapid response team decreased unexpected fatalities translating in an estimated 1.5 lives saved per week in a French hospital. Overall, in-hospital mortality decreased from 39.6 to 34.6 per 1000 hospital discharges [116]. Several authors reported on reductions in the rates of unexpected cardiac arrests, unexpected ICU admissions and re-admissions, as well as both short- and long-term mortality following medical emergency or rapid response team implementation [111, 117‐122]. The nationwide implementation of rapid response systems in the Netherlands was associated with a decrease in cardiac arrests, unplanned ICU admissions, and in-hospital mortality in adult ward patients [123]. In line with these results, three meta-analyses reported that implementation of medical emergency or rapid response systems reduced the rates of cardiac arrests outside of the ICU and in-hospital mortality [124‐126]. Late activations of rapid response teams were associated with increased rates of ICU admission, prolonged hospital stays and higher mortality [127]. The European Resuscitation Council Guidelines 2021 recommended rapid response systems as the efferent loop in the modified ‘in-hospital chain of survival’ to prevent in-hospital cardiac arrest [128].