Using Recovery Rooms (PACUs) Differently: Addressing the Hidden Pandemic

There is increasing interest in extending PACU-based care in order to better address the growing problem of early postoperative complications and their impact on patient and hospital outcomes. There is promising evidence of benefit in this approach, but still a great deal to be learned, such as the optimal target patient population, the precise value generated, and the structures, processes and specific care needed to generate that value. 

The Problem                     

The landscape of surgical care is undergoing a significant transformation with substantial demographic shifts (ageing populations, chronic disease burden) and increased demand for surgery (Meara et al. 2016; Bagshaw et al. 2017; de Lange et al. 2020; Ludbrook 2022). These older, frailer and more medically complex surgical patients are at risk of developing postoperative complications and their sequelae - prolonging recovery, extended hospital stay, reduced quality of life and mortality (Tevis et al. 2016; Pinto et al. 2016). These complications are costly. Each patient with postoperative complications incurs, on average, an additional US$19,626 in hospital costs, representing nearly 20% of their total surgical expenditure, which threatens the long-term sustainability of hospital systems (Healy et al. 2016).

Postoperative complications remain a leading cause of avoidable harm in surgical care. Their insidious nature and low detection rates on general surgical wards (Khanna et al. 2023) have led to descriptions of a ‘hidden pandemic’ (Ludbrook 2022).

Amid these pressures, a distinct, underserved patient group has emerged: the medium-risk surgical patient. These individuals are often unsuitable for routine ward care yet do not meet intensive care unit (ICU) admission thresholds. In response, specialised high-acuity postoperative care units have been established to bridge the gap between general wards and ICU.

PACU-Based Solutions

Conventional postoperative pathways involve a stepwise transition from operating theatre to recovery room (post-anaesthesia care unit; PACU), to general ward. If needed, a high acuity setting such as a high dependency unit (HDU) or ICU may be used. This model remains largely tradition-driven, with limited supportive evidence (Wong et al. 2019). ICUs, while essential for critically ill patients, are resource-intensive and costly (Anesi et al. 2019). Routine ICU admission for low-acuity patients has not been shown to improve outcomes (De Robertis 2018; Emerson et al. 2023). Furthermore, limited ICU capacity contributes to broader system pressures, including surgical cancellations and strained triage decisions (Groenland et al. 2019; Harris et al. 2018).

Specialised high-acuity postoperative units have emerged as an intermediate care model. First introduced in the UK in the 1980s, often driven in response to ICU bed shortages and hospital congestion (Ziser et al. 2002; Kiekkas and Tzenalis 2022), extended postoperative care units (EPCUs) provide short-term high-acuity care for surgical patients at moderate risk of deterioration (Aps 2004). Compared to the ward, these units offer enhanced nurse-to-patient ratios, continuous monitoring and timely interventions, such as non-invasive ventilation or vasopressor therapy. These focus on the critical window of the first 24-48 hours after surgery when many of the complications arise, and may improve patient outcomes, reduce ICU demand and optimise resource utilisation (Thompson et al. 2003).

In recent years, this concept has evolved to using anaesthesia care in PACUs differently. Simply extending PACU stays, however, can be associated with increased nursing workload, missed care, delays in allied health input and psychological distress for patients and families (Ziser et al. 2002; Nelson et al. 2020). In contrast, highly structured anaesthesia-led models, such as Advanced Recovery Room Care (ARRC), which extend and enhance PACU care, are growing in response to high quality evidence of improved outcomes, resource utilisation, and cost (Ludbrook et al. 2025a; Ludbrook et al. 2023; Leaman and Ludbrook 2023; Koning et al. 2024) (Table 1).

These models appear distinct from ICUs and aim at a lower risk group – mortality of 2% compared to 8% in ICUs (Schockaert et al. 2025). However, they are inconsistent in name, in the patients managed and, in the processes, and procedures provided (Schockaert et al. 2025; Tran et al. 2025).Further, data on effectiveness and cost are relatively sparse, and several important questions remain:

1. Who are optimal candidates for admission?

2. What specific care processes contribute to effectiveness?

3. What are the clinical and economic benefits?

4. Where next? 

1. Who are the optimal candidates for admission?

These Postoperative Care Units (PCUs) provide intermediate-level care for surgical patients at increased risk of complications but not requiring full ICU-level support (Centre for Perioperative Care 2020). They are not substitutes for ICUs and typically lack the resources for invasive organ support, such as mechanical ventilation. The ideal PCU candidates are noncardiac surgery patients at moderate risk of deterioration – those too complex or unstable for general ward care, yet not critically unwell enough to warrant ICU admission.

However, there is no universally accepted framework for categorising surgical patients into low-, medium-, or high-risk groups (Pearse et al. 2011; Sankar et al. 2015). Risk stratification in current practice is variable and often relies on subjective clinical judgement or disparate tools, such as the NSQIP surgical risk calculator, ASA physical status or APACHE-II, all with limitations in accuracy and consistency. In the UK, expert consensus recommends critical care for patients with a predicted 30-day mortality between 1–5%, but there is no standardised method for estimating this risk (Centre for Perioperative Care 2020). A recent systematic review illustrates this heterogeneity, with included studies applying different thresholds of moderate risk ranging from 0.7% to 5% (Tran et al. 2025).

While preoperative scoring systems are useful for estimating risk (usually mortality out to 30 days), they reflect a static assessment. Incorporating clinician judgement and real-time reassessment into triage decisions is therefore essential. Further, it can be argued that it is the risk of identifiable and rapidly treatable early complications which should be considered for triage to early postoperative care. Developing dynamic, evidence-informed models that integrate both objective and evolving clinical data may improve PCU admission practices and optimise resource utilisation (Saugel et al. 2019).

2. What specific care processes contribute to effectiveness?

The effectiveness of PCUs lies in their ability to deliver timely, targeted interventions beyond the capabilities of general surgical wards. Several factors may contribute to this. Preoperatively, risk identification and planning allow early identification of patients who may benefit from higher acuity care. Postoperatively, continuous monitoring and more frequent observations in the PACU onwards enable early detection of deterioration. The first 24 hours after surgery are often termed the 'golden hours' due to the high incidence of complications (Thompson et al. 2003). Accordingly, PCU admissions are typically short, focused, and often limited to 24 hours.

PCUs also offer an expanded capacity to support vital organ systems through use of fluids, vasopressors and inotropes guided by advanced haemodynamic monitoring. Respiratory support varies, but high-flow nasal oxygen and non-invasive ventilation are common limits of care. Importantly, these interventions are delivered by staff with high acuity care expertise in adequate numbers. Nurse-to-patient ratios, for example, typically range from 1:1 to 1:3, compared to 1:4 to 1:7 on general wards (Ludbrook et al. 2023; Stahlschmidt et al. 2022; Costa-Pinto et al. 2023; Falk 2023; McHugh et al. 2020; Clarke et al. 2000). There is ready access to skilled medical staff.

This is supported by a peri-operative culture of active and proactive intervention to achieve early ward readiness (Ludbrook et al. 2025b). This includes precise adherence to Enhanced Recovery After Surgery (ERAS) principles, such as early mobilisation and oral intake (Peden et al. 2023).

The effectiveness of PCUs likely reflects a complex interplay of patient-specific, clinical and systemic factors. Future research should aim to identify which factors most strongly influence postoperative outcomes and resource efficiency.

3. What are the clinical and economic benefits?

Value generation (outcome and cost) from such models can be considered from a range of perspectives. Hospital value can be generated from fewer expensive complications and lower resource utilisation. Short-term measures such as length of stay and 30-day readmissions may show improvement (Koning et al. 2024), although measuring longer-term outcomes may reveal a more comprehensive picture (Leaman and Ludbrook 2023; Brown et al. 2021).

Mortality is a key measure of generating societal value, but short-term improvements can be hard to measure in a medium-risk patient population. A significant mortality reduction out to 18 months has been shown with ARRC (Ludbrook et al. 2025a) and suggests the demonstrated association between early postoperative morbidity and long-term mortality (Moonesinghe et al. 2014) may be preventable.

The business aspect of these units may require different data from academic studies and will be contextual. From a hospital perspective, cost savings may be made from hospital-funded care, but what is funded (such as rehabilitation or new nursing home care) varies across healthcare systems. Further, analyses need to account for evolving approaches to post-discharge care, which may impact length of stay, such as models of supported home care. Measures such as Days at Home (DAH) will be insufficient in such cases unless granular data on patient locations is measured. The financial benefit of sparing bed days will also depend on financial structures. For example, saved bed days in some systems may be used to further generate profit through opportunities to grow high-margin care. 

4. Where next? (Implementation and trials/data; integration into POM)

To ensure that PCUs evolve into a consistently effective model of care, future efforts must focus on integration, data generation and rigorous evaluation. Integration within a broader perioperative medicine (POM) framework is essential (Figure 1). PCUs should function as part of a multidisciplinary continuum, from preoperative risk assessment and shared decision-making to postoperative monitoring and recovery, delivered collaboratively by surgeons, anaesthetists, intensivists, nurses and allied health professionals. The positive impact of preoperative interventions, such as prehabilitation, on some patients will influence both patient triage and the need for enhanced postoperative care.

Equally important is building a stronger evidence base. It would be disappointing to revisit this field in another decade without greater clarity on the value generated and the specific processes that drive effectiveness. Existing units should be encouraged to collaborate - sharing data, benchmark outcomes and embed continuous quality improvement through global collaborative platforms. Randomised controlled trials remain important, although often limited by inter-centre variability, but pragmatic designs such as registry-based studies, stepped-wedge designs, cluster randomised trials, and causal influence from non-randomised studies, may offer practical insights while aligning with routine clinical workflows (Moonesinghe 2016).

The next decade must focus on embedding PCUs within national perioperative strategies, strengthening data capability and fostering multi-institutional collaboration. Through these coordinated efforts, we can refine the PCU model, improve patient outcomes and deliver on the promise of safer perioperative care on a system-wide scale.

Conflict of Interest

None.