From carbon cost to climate care: Greening our intensive care units

Abstract

Healthcare systems are major contributors to global greenhouse gas emissions, with intensive care units (ICUs) among the most carbon-intensive environments due to continuous energy demand, extensive reliance on single-use medical devices, and high pharmaceutical consumption. This narrative review examines the environmental footprint of ICUs, synthesising contemporary life-cycle evidence and international case studies describing feasible and clinically safe sustainability interventions in critical care. We outline practical strategies for ICU decarbonisation, including energy-efficient infrastructure, sustainable procurement, waste reduction, digital optimisation, and re-evaluation of low-value clinical practices. Importantly, many of these interventions align with established quality-improvement principles and are associated with clinical co-benefits such as reduced iatrogenic harm, improved patient comfort, and enhanced staff wellbeing. Broader policy frameworks, including the Sustainable Development Goals and national net-zero healthcare commitments, are discussed as enabling levers for system-level adoption. Greening ICUs should therefore be viewed not as a competing priority, but as an opportunity to deliver safer, more resilient, and patient-centred critical care while advancing planetary health.

Key Words: Intensive care unit; Carbon footprint; Sustainable healthcare; Green intensive care unit; Environmental sustainability; Climate change; Decarbonisation; Hospital waste; Critical care

Core Tip: Intensive care units (ICUs) are vital to modern healthcare, but they are also disproportionately resource-intensive. This review outlines the carbon footprint of critical care and offers a blueprint for transformation that balances clinical excellence with environmental responsibility. By embedding sustainability into equipment procurement, clinical workflows, energy management, and policy alignment, the ICU can evolve into a space that heals both patients and the planet. The path forward demands coordinated action across sectors. Hospitals must commit resources, policymakers must provide incentives, and clinicians must lead cultural shifts. The tools and knowledge exist. What remains is the collective will to act decisively. Greening our ICUs is no longer a luxury; it is a necessity for ethical, effective, and future-ready healthcare.

INTRODUCTION

Climate change is no longer a distant or future concern; it is an unfolding public health emergency with immediate and far-reaching consequences. The World Health Organization has identified climate change as “the greatest threat to global health in the 21^st century”[1]. Ironically, the healthcare sector, tasked with protecting human health, is itself a substantial contributor to this crisis. Contemporary estimates indicate that healthcare systems account for approximately 4%-5% of total global greenhouse gas emissions[2]. If considered a nation, the global health sector would rank as the fifth-largest emitter worldwide[2]. In high-income countries, the contribution is even greater, reaching 8%-10% of national emissions in settings such as the United States[3,4].

This paradox presents a profound ethical challenge. While modern medicine is grounded in the principle of primum non nocere (first, do no harm), healthcare delivery unintentionally amplifies climate-related health risks at a planetary scale. There is increasing recognition that this foundational ethical obligation must now extend beyond individual patients to encompass environmental stewardship and climate accountability[5].

Within hospitals, intensive care units (ICUs) represent a uniquely high-leverage focus for sustainability efforts. Although they occupy a small proportion of inpatient beds, ICUs concentrate the most carbon-intensive processes in healthcare: Continuous heating, ventilation, and air-conditioning (HVAC) operation; dense deployment of energy-dependent technologies; high procedural intensity; and extensive use of single-use consumables and pharmaceuticals[6]. Recent life-cycle analyses estimate that a single ICU bed may generate approximately 138 kg of carbon dioxide-equivalent (CO₂e) emissions per day, nearly three times that of a general ward bed[7,8]. In high-income settings, the daily carbon footprint of a critically ill patient may exceed the per-capita emissions of individuals in low-income countries over several weeks or months[7-11].

These emissions are not abstract statistics. They translate directly into accelerated climate change, air pollution, and ecosystem disruption, with well-documented downstream effects on cardiovascular, respiratory, infectious, and heat-related morbidity and mortality[12]. The paradox is sobering: The very interventions that preserve life in the ICU may simultaneously contribute to long-term population-level harm through environmental degradation.

This review provides a comprehensive synthesis of the environmental footprint of critical care and examines emerging evidence-based strategies for sustainable ICU practice. We evaluate emissions across major domains-including energy systems, consumables and waste, pharmaceuticals and medical gases, equipment, and diagnostic imaging-and review international models demonstrating that decarbonisation can be achieved without compromising patient safety or clinical outcomes. We further propose a pragmatic implementation framework grounded in quality-improvement principles and aligned with policy-level net-zero commitments for the health system (Figure 1). By embedding environmental stewardship into routine critical care practice, ICUs can play a pivotal role in advancing a healthcare system that protects current patients and future generations[13].

Figure 1 The green intensive care unit framework: From emission hotspots to sustainable critical care. Conceptual framework illustrating the major emission hotspots in intensive care units, the 5 Rs implementation framework (replace/avoid, reduce, reuse, recycle, rethink), associated clinical co-benefits, and downstream system-level outcomes. The framework demonstrates how targeted interventions in high-impact domains can simultaneously reduce environmental footprint, improve quality of care, and support health-system sustainability. A: Emission hotspots; B: Rs framework; C: Clinical co-benefits; D: System outcomes. ICU: Intensive care unit; HVAC: Heating, ventilation and air conditioning.

ENVIRONMENTAL FOOTPRINT OF THE ICU

ICUs are among the most resource-intensive environments in modern healthcare systems and account for a disproportionate share of healthcare-related environmental impact. This footprint arises from the convergence of continuous energy demand, complex technological infrastructure, high pharmaceutical throughput, and extensive reliance on disposable medical supplies. Unlike most hospital areas, ICUs operate without interruption and are designed around redundancy and safety margins—features essential for patient survival but that inherently amplify resource consumption.

Life-cycle assessment (LCA) studies provide the most comprehensive estimates of ICU-associated emissions by capturing both direct operational energy use and indirect upstream supply-chain contributions. Across diverse health systems, reported emissions range from 88 kg to 178 kg of CO₂e per patient-day, with substantial variability driven by local energy sources, infrastructure efficiency, and clinical practice patterns[7,9,11]. These estimates place ICU care among the most carbon-intensive activities within hospital systems and highlight the concentration of emissions within a limited number of high-acuity care processes (Figure 2).

Figure 2 Carbon hotspots in the intensive care unit. Approximate contribution of major emission sources to the total intensive care unit (ICU) carbon footprint, based on published healthcare life-cycle assessment and sustainability reports. Energy use-predominantly heating, ventilation, and air conditioning systems-accounts for the largest share, followed by medical gases, single-use devices and consumables, pharmaceuticals, and waste disposal. Ranges are illustrative as they are derived from heterogeneous studies with different system boundaries, energy mixes, allocation methods, and included emission categories; they should not be interpreted as components of a single universal ICU carbon-footprint profile. HVAC: Heating, ventilation and air conditioning.

From an accounting perspective, healthcare-related greenhouse gas emissions are commonly classified using the Greenhouse Gas Protocol into three categories. Scope 1 emissions arise from direct on-site sources such as fuel combustion and medical gases. Scope 2 emissions reflect indirect emissions from purchased electricity, heating, and cooling. Scope 3 emissions encompass upstream and downstream supply-chain activities, including pharmaceuticals, medical devices, consumables, capital equipment, and waste treatment. In most healthcare systems, scope 3 emissions account for the largest proportion of total emissions, often exceeding those from direct energy use[3,4,7]. This distinction is particularly relevant in intensive care, where high pharmaceutical consumption, reliance on single-use devices, and complex equipment substantially amplify supply-chain-related environmental impact.

Energy consumption and infrastructure

Energy consumption constitutes the dominant contributor to ICU-related greenhouse gas emissions across most health systems. Across published ICU assessments, energy-related emissions have accounted for approximately 19%-80% of the total ICU carbon footprint, depending on the local energy mix, infrastructure, system boundaries, and assessment methodology[3,7,11].

A principal driver of this demand is HVAC infrastructure. ICUs require high air-exchange rates, stringent temperature and humidity control, and continuous filtration to meet infection-prevention and patient-safety standards. Although these requirements are non-negotiable, their implementation varies widely. Comparative analyses reveal substantial differences in energy intensity between ICUs that cannot be explained solely by patient acuity, implicating infrastructure design, commissioning quality, and maintenance practices as key determinants of emissions[2,4].

Empirical ICU-specific studies illustrate the scale of energy-related emissions. In a comparative LCA of septic shock care, daily energy-related emissions accounted for approximately 155 kg CO₂e (87%) in a United States ICU and 67 kg CO₂e (76%) in an Australian ICU, with differences driven primarily by the underlying electricity generation mix rather than by clinical practice patterns[11]. Similarly, French hospital LCAs indicate that electricity and thermal energy contribute approximately 29% of total hospital and ICU-related emissions[14]. Together, these findings underscore the central importance of both energy efficiency and energy decarbonisation as foundational strategies for sustainable critical care.

Consumables, waste, and circularity

Beyond energy use, a substantial proportion of the ICU environmental footprint arises from consumables and waste, driven by upstream manufacturing, packaging, transportation, and downstream disposal processes[7]. High procedural intensity and stringent infection-prevention requirements favour the extensive use of single-use medical products, resulting in high material throughput and increased waste generation.

Material-flow analyses and waste audits consistently demonstrate that ICUs generate disproportionately large quantities of solid waste per patient-day, typically ranging from 6 to 8 kg per ICU bed per day, exceeding those of general medical wards[15]. Much of this waste comprises plastics, paper, and packaging associated with syringes, tubing, dressings, personal protective equipment, and procedural kits[15]. LCAs further indicate that consumables contribute several kilograms of CO₂e per patient-day, underscoring their relevance within the overall ICU footprint[11].

A recurrent finding across studies is the over-classification of waste as infectious or regulated, leading to disposal via energy-intensive pathways, such as incineration, rather than recycling or general waste streams[16]. Regulated medical waste processing carries a markedly higher carbon footprint than non-hazardous waste management, making segregation practices a critical determinant of emissions. Observational studies suggest that mis-segregation is more often driven by risk aversion, unclear bin placement, and limited staff training than by true contamination risk[17,18].

Increasing attention has therefore shifted toward circularity, defined as reducing material input, extending product life, and recovering value at the end of use. Several high-volume ICU consumables, including textiles, underpads, and other selected instruments, have viable reusable alternatives when supported by appropriate sterilisation and logistics pathways. Comparative LCAs consistently demonstrate lower environmental impact for reusable products once processing systems reach sufficient scale, although outcomes remain sensitive to local energy sources, transport distances, and adherence to workflows. Certified device reprocessing and manufacturer take-back programmes have similarly been associated with reductions in waste generation and embedded emissions in settings where regulatory and governance frameworks permit their use[19].

Pharmaceuticals and medical gases

Pharmaceuticals and medical gases contribute significantly to the ICU footprint through both direct use and upstream supply-chain emissions, including energy-intensive manufacturing, cold-chain transport, packaging, and disposal[7,20]. In ICU-specific carbon-accounting studies, pharmaceuticals frequently represent a major scope 3 contributor, reflecting the high turnover of injectable agents, continuous infusions, and frequent therapy changes characteristic of critical illness[7,20,21]. Medication wastage-driven by partial vial discard, preparation losses, therapy escalation and de-escalation, and expiry-further increases environmental impact and represents a practical target for stewardship interventions[20,21].

Analyses that disaggregate ICU emission “hotspots” consistently identify sedation and analgesia, vasoactive infusions, antimicrobials, and parenteral therapies as major drivers of drug-related emissions, driven by both volume and frequency of administration[20,21]. In a French ICU carbon-footprint evaluation, medications emerged as one of the leading contributors to per-patient-day emissions, alongside energy consumption, reinforcing the importance of pharmacy-centred strategies such as vial-size optimisation, standardised concentrations, closed-loop inventory systems, and waste audits[20].

Medical gases introduce a distinct emissions profile. Although oxygen is not itself a greenhouse gas, it carries a measurable upstream footprint related to production, compression or liquefaction, storage, and distribution, with carbon intensity highly dependent on electricity mix and delivery logistics[7,20,22,23]. Demand-side optimisation and energy decarbonisation are therefore both relevant to reducing oxygen-associated emissions.

Inhaled anaesthetic agents and nitrous oxide warrant particular attention due to their high global warming potential[24]. The 100-year global warming potentials of commonly used volatile agents are orders of magnitude higher than those of carbon dioxide; for example, desflurane (with a 100-year global warming potential of approximately 2540) far exceeds those of sevoflurane and isoflurane[25]. Nitrous oxide is likewise a potent greenhouse gas whose atmospheric persistence extends far beyond its clinical use, and its combination with volatile agents further amplifies climate impact. Accordingly, although intravenous sedation remains the dominant modality in most ICUs, the increasing use of volatile-based sedation technologies extends the relevance of anaesthetic-gas stewardship beyond the operating theatre[26].

Medical equipment, capital goods, and diagnostic imaging

Medical equipment and capital goods contribute to ICU emissions through two principal pathways: Embedded emissions from manufacturing and global supply chains, and operational emissions from electricity consumption during active use and standby[7,27]. Although less visible than consumables, capital equipment has a substantial life-cycle impact because ICU technologies are complex and material-intensive, and are replaced on predictable procurement cycles.

Within healthcare-related scope 3 emissions, medical devices and capital equipment represent an important component, reflecting energy-intensive manufacturing processes, international transport, and packaging[3,7]. In the ICU, ventilators, monitors, infusion pumps, dialysis machines, ultrasound platforms, and extracorporeal support systems all carry embedded carbon costs that accumulate across device fleets and replacement cycles[3].

Operational practices further shape equipment-associated emissions. Devices maintained in continuous standby for safety and readiness consume electricity even when not actively used, creating a persistent baseline energy load. Consequently, utilisation patterns, preventive maintenance, and power-management settings-where clinically appropriate-can meaningfully influence unit-level emissions[7,27].

Procurement and replacement strategies increasingly determine the life-cycle footprint of ICU equipment. Device longevity, repairability, modular component replacement, and access to refurbishment or manufacturer take-back programmes strongly influence cumulative emissions over time. Procurement frameworks that incorporate environmental criteria alongside safety, performance, and cost provide a mechanism to shift from acquisition-focused decision-making toward life-cycle-informed stewardship[3,28].

Although not physically located within the ICU, diagnostic imaging is an important downstream contributor to the environmental footprint of critical care, as imaging utilisation is frequently driven by ICU decision-making. LCAs demonstrate that computed tomography (CT) and magnetic resonance imaging (MRI) are among the most energy-intensive diagnostic modalities. In a comprehensive Australian analysis, a single CT examination generated approximately 9-20 kg CO₂e, while MRI examinations frequently exceeded 17 kg CO₂e per scan, depending on scanner type, utilisation rates, and electricity mix[29]. These findings highlight imaging stewardship as a relevant decarbonisation strategy, with potential co-benefits including reduced patient transport, radiation exposure, and workflow disruption (Table 1).

Table 1 Major contributors to the environmental footprint of intensive care units.

Component	Relative contribution	Principal drivers
Energy and infrastructure	Dominant	Heating, ventilation, and air-conditioning, continuous power demand
Consumables and waste	High	Single-use devices, regulated waste
Pharmaceuticals	Moderate-high	Injectables, wastage
Medical gases	Lower but non-trivial	Oxygen supply chain, N2O
Equipment and capital goods	Sustained background	Manufacturing, standby power

Relative contribution varies by setting and is influenced by local infrastructure, clinical practice, and energy mix.

GLOBAL EVIDENCE AND EMERGING GREEN ICU MODELS

Over the past decade, sustainability in critical care has evolved from isolated institutional initiatives to a more coordinated, evidence-informed international movement. A growing body of observational studies, life-cycle analyses, quality-improvement reports, and professional society statements now demonstrates that environmentally responsible ICU practices can be implemented without compromising patient safety, clinical outcomes, or operational reliability (Table 2)[30-38]. Rather than converging on a single prescriptive model, existing approaches reflect context-specific adaptations shaped by local infrastructure, resource availability, regulatory environments, and governance structures.

Table 2 Illustrative international examples of emerging green intensive care unit models.

Country/region	Health system/initiative	Scope of sustainability action	Key features relevant to ICU practice
United Kingdom	National Health Service	System-wide net-zero strategy	National commitment to net-zero emissions; phase-down of high-global-warming-potential inhaled anaesthetics; ICU-level initiatives focusing on waste segregation, procurement reform, and infrastructure optimisation
United States	Integrated healthcare systems (e.g., kaiser permanente)	Organisation-wide sustainability programs	Carbon-neutral operations; ICU-led “Green Teams”; device reprocessing; transition to reusable patient care items; energy-efficient building systems
Australia	Clinician-led ICU sustainability programmes	Multicentre research and practice initiatives	Life-cycle assessments in ICUs; adoption of reusable gowns and underpads; reduction in low-value blood testing; incorporation of sustainability into ICU redesign
New Zealand	Public hospital networks	Medical gas and equipment optimisation	Elimination of nitrous oxide use in selected ICUs; transition to alternative analgesia and sedation strategies; waste reduction initiatives
Netherlands	National ICU sustainability networks	Policy-supported institutional change	Circular procurement practices; waste reduction strategies; integration of sustainability within national critical care frameworks
Low- and middle-income settings	Institution-level ICU practices	Resource-constrained adaptations	Emphasis on equipment reuse and repair, extended device lifespan, and supply resilience, often driven by necessity rather than environmental intent

Examples are illustrative and reflect heterogeneous, context-specific approaches rather than uniform national practice. ICU: Intensive care unit.

In high-income health systems, professional societies and national organisations have played a central role in legitimising sustainability as a core component of quality critical care. The European Society of Intensive Care Medicine recently published a Green Paper outlining practical directions for environmentally sustainable ICU practice, emphasising the identification of emission hotspots, the integration of sustainability into quality-improvement programmes, and explicit alignment with infection-prevention and patient-safety frameworks[31]. Similar priorities are reflected in sustainability task forces, consensus statements, and clinician-led initiatives across Australia, New Zealand, and North America[33-36].

Country-level initiatives provide further empirical support. In Australia, multicentre ICU LCA have quantified emissions and informed targeted interventions, particularly in energy optimisation, waste segregation, anaesthetic stewardship, and reduction of low-value testing[36]. In Canada, climate-conscious recommendations embedded within the Choosing Wisely framework have reframed sustainability as an extension of reducing low-value care rather than rationing, facilitating clinician engagement and acceptance[37]. Dutch intensive care networks have similarly collated best practices in circular procurement, waste reduction, and sustainable device management, supported by national policy alignment.

Evidence also emerges from institution-level programmes that embed sustainability into routine ICU governance. Hospitals with dedicated “Green ICU” working groups report sustained reductions in regulated medical waste volumes, energy consumption, and supply use when environmental metrics are integrated into established structures such as infection-control committees, pharmacy stewardship programmes, and quality-improvement cycles. These initiatives typically prioritise incremental change, continuous data feedback, and frontline engagement rather than disruptive system redesign, enhancing both feasibility and durability of implementation.

Across low- and middle-income settings, published evidence remains limited but highlights distinct opportunities and alternative models of sustainability[39,40]. Resource constraints frequently necessitate equipment reuse, repair, and extended device lifespans, practices that align closely with circular-economy principles[41,42]. Emerging reports suggest that formalising such approaches within safety and quality frameworks may yield dual benefits for environmental impact and health-system resilience, particularly in settings vulnerable to supply-chain disruption and climate-related shocks.

Collectively, global experience demonstrates that sustainable ICU practice is feasible across diverse health systems when interventions are aligned with existing clinical priorities, governance structures, and professional cultures. At the same time, wide variation in scale, scope, and pace of adoption underscores the persistent challenges that continue to impede widespread implementation. These observations provide a clear rationale for examining the structural, organisational, and behavioural barriers that limit translation of sustainability evidence into routine critical care practice.

BARRIERS TO TRANSLATING SUSTAINABILITY EVIDENCE INTO ROUTINE ICU PRACTICE

Despite growing recognition of the substantial environmental footprint of critical care and the emergence of robust evidence supporting sustainable practice, integration into routine ICU workflows remains uneven and highly variable. This implementation gap reflects not a lack of technical feasibility, but a fundamental misalignment between environmental objectives and the safety imperatives, organisational architectures, economic incentives, infrastructural legacies, and professional cultures that shape decision-making in high-acuity care[35,43,44].

Primacy of patient safety and risk asymmetry

Critical care is uniquely governed by a culture in which redundancy, over-preparation, and near-zero tolerance for error are not inefficiencies but core safety principles. In this context, even low-probability risks associated with sustainability initiatives, whether related to infection control, equipment availability, medication supply, or workflow redesign, are amplified by the potentially catastrophic consequences of failure and therefore approached with disproportionate caution, even when evidence demonstrates clinical equivalence[35,45].

This tension is reinforced by a pronounced asymmetry in risk perception. The harms of environmental degradation are diffuse, delayed, and probabilistic, whereas adverse clinical events are immediate, visible, and directly attributable to individual decisions at the bedside. As a result, sustainability interventions are often held to a higher evidentiary threshold than many established ICU practices, particularly when their benefits accrue at system or population levels rather than to the individual patient in front of the clinician[3,43].

Organisational inertia and competing priorities

Sustainability initiatives compete for attention within an ICU environment already saturated by staffing shortages, regulatory oversight, infection-prevention mandates, and expanding quality and reporting requirements. In such settings, environmental performance is rarely perceived as a clinical priority, but rather as an administrative or institutional aspiration subordinate to accreditation, reimbursement, and short-term outcome targets[42,43].

Organisational architecture further fragments responsibility for environmental performance across facilities management, procurement, and executive leadership, while many of the principal drivers of emissions remain embedded within routine clinical decisions. This disconnect limits unit-level ownership and reinforces the perception that sustainability lies outside the professional remit of intensivists and ICU teams[35,46].

Economic framing and procurement structures

Economic barriers extend beyond absolute cost and reflect how value is defined and operationalised within healthcare systems. Environmental externalities are seldom internalised within departmental budgets, rendering emissions largely invisible in routine clinical and managerial decision-making. Consequently, procurement processes continue to prioritise unit price, contractual conformity, and immediate availability over life-cycle environmental performance[47,48].

This misalignment is compounded by a temporal disconnect between costs and benefits. While environmental gains typically accrue over long time horizons or at system-wide scales, the financial and operational pressures facing ICUs are immediate and local. In the absence of aligned incentives, sustainability considerations remain peripheral to daily clinical and managerial choices[44,47].

Infrastructure, legacy, and data limitations

The physical infrastructure of many ICUs constrains sustainability by design. Legacy heating, ventilation, medical gas, and electrical systems were optimised for reliability and infection control rather than energy efficiency, limiting operational flexibility and obscuring the environmental consequences of routine practice[2,45].

A persistent lack of granular, unit-level environmental data compounds these constraints. Energy consumption, waste generation, and supply utilisation are rarely measured at the bedside and, when available, are often delayed, aggregated, or difficult to interpret. In the absence of timely, actionable feedback, sustainability remains an abstract institutional ambition rather than an operational performance metric integrated into routine quality improvement[43,46].

Professional culture, education, and behaviour

Sustainability also encounters deeply rooted cultural and behavioural barriers within critical care. Environmental impact remains largely absent from undergraduate and postgraduate medical curricula, leaving clinicians without a conceptual framework for integrating sustainability into clinical reasoning, professional identity, or leadership roles[49].

At the bedside, the cognitive demands and time pressure of ICU practice reinforce reliance on standardised, high-redundancy workflows prioritising speed, predictability, and risk minimisation. In such high-stakes environments, deviation from established routines-even for non-clinical reasons-may be perceived as introducing uncertainty, fostering resistance to change and reinforcing the status quo[35,45].

Together, these barriers explain why sustainable ICU practices, despite compelling evidence and successful institutional models, have not yet achieved widespread routine adoption. Importantly, they arise not from an inherent incompatibility between sustainability and critical care, but from a misalignment between environmental objectives and the safety, organisational, economic, and cultural structures that govern ICU delivery. Effective implementation, therefore, requires strategies explicitly designed to address the realities of high-acuity care, aligning climate stewardship with patient safety, workflow integrity, professional identity, and institutional incentives. This alignment forms the conceptual foundation for the pragmatic implementation framework outlined below.

IMPLEMENTATION FRAMEWORK: INTEGRATING SUSTAINABILITY INTO ROUTINE ICU PRACTICE

Integrating environmental sustainability into intensive care practice requires an implementation framework that safeguards patient safety, respects the realities of critical illness, and avoids adding cognitive or operational burden to already stretched teams. Emerging evidence demonstrates that environmentally responsible ICU practices are not incompatible with high-quality care; rather, they frequently align with core principles of safety, efficiency, and evidence-based medicine[6-8,11,12,31,32].

To translate this alignment into routine practice, this review applies a pragmatic framework based on the “5 Rs” of sustainable critical care-replace (or avoid), reduce, reuse, recycle, and rethink-providing a clinically intuitive and operationally feasible structure for intervention design and sequencing (Figure 3)[31,32,35,44]. The “Rs” framework originates from environmental science and waste-management hierarchies and has been widely adopted across sustainability disciplines, including healthcare and anaesthesia practice. Here, this established conceptual model is adapted specifically to the ICU context, explicitly aligning each principle with critical care-specific clinical workflows, safety constraints, and operational realities.

Figure 3 Conceptual representation of the 5 Rs framework (replace/avoid, reduce, reuse, recycle, rethink) for sustainable intensive care unit practice. The framework integrates bedside clinical decision-making, operational resource stewardship, and system-level redesign to support environmentally responsible critical care without compromising patient safety or care quality. ICU: Intensive care unit.

Replace/avoid: Eliminating low-value and unnecessary care

The most powerful sustainability intervention in the ICU is often avoiding interventions that provide little or no clinical benefit. Every diagnostic test, disposable item, and therapeutic intervention carries an embedded environmental cost through material consumption, energy use, and waste generation[3,7,9,11,14].

Long-standing routine practices, such as default daily laboratory panels, automatic chest radiography, and liberal arterial blood gas sampling, persist largely because of habit rather than evidence. Multiple randomised and quality-improvement studies demonstrate that reducing routine chest radiography and laboratory testing in stable ICU patients does not worsen clinical outcomes and can be safely implemented using education, audit-and-feedback, and clinical decision support tools[49,50].

Avoiding low-value care aligns directly with established de-implementation and patient-safety initiatives, including choosing wisely, by reducing iatrogenic harm, patient discomfort, and cognitive burden while simultaneously lowering healthcare emissions[28,37,41,51]. Importantly, this principle reframes sustainability not as rationing but as precision in care delivery, providing the right intervention for the right patient at the right time[28,31,35].

Reduce: Optimising resource use within necessary care

When interventions are clinically indicated, their resource intensity can often be reduced without compromising outcomes. Practical bedside strategies include minimising overfill in intravenous infusions, rationalising medication preparation and batching, avoiding overstocking of supplies in patient rooms, and consolidating care activities to reduce repeated room entry and waste generation[15,16,18,43].

At the systems level, ICUs remain among the most energy-intensive hospital environments. Incremental efficiency measures such as optimised lighting, equipment power-management protocols, temperature set-point adjustment within safe ranges, and preventive maintenance of high-load devices can yield substantial cumulative reductions in emissions[20,21,29-31,34]. Importantly, such gains are most durable when efficiency is embedded into system design and default workflows rather than reliant on individual behavioural vigilance[3,6,19].

Reduction strategies target inefficiency rather than care itself, reinforcing the distinction between waste and value and preserving readiness and safety margins in high-acuity environments[28,31,35].

Reuse: Leveraging durable and reprocessable resources

Where infection-prevention standards and regulatory frameworks permit, reusable and reprocessable equipment offers substantial environmental and economic advantages. Examples include durable gowns and linens, metal surgical instruments, reusable laryngoscope blades, and reprocessable bronchoscopes[19,27,31,35,44].

Evidence from multiple healthcare systems demonstrates that such strategies can be safely integrated into ICU workflows when supported by appropriate sterilisation infrastructure, logistics pathways, and governance mechanisms. Comparative LCAs consistently show lower environmental impact for reusable products once processing systems reach sufficient scale. However, outcomes remain sensitive to local energy mix, transport distances, and adherence to return workflows[19,27,38,42,44]. Beyond emissions reduction, reuse represents a cultural shift away from disposability as the default toward stewardship of material resources, reinforcing professional responsibility for sustainable care delivery[27,45].

Recycle: Improving waste segregation and material recovery

A substantial proportion of ICU waste is technically recyclable but is diverted into regulated medical waste streams due to misclassification, risk aversion, or unclear protocols. Improving waste segregation, particularly for uncontaminated packaging, plastics, and paper, offers immediate environmental and financial benefits without affecting patient care[15,16,18,43].

Successful recycling programmes share several core features: Clearly labelled bins at the point of use, infection-control-approved protocols, consistent staff education, and regular audit with feedback[15,18,31,32]. Although recycling alone cannot offset the carbon footprint of critical care, it plays an important role in engaging frontline staff, reinforcing environmental awareness, and linking sustainability to everyday workflow[28,31,37].

Rethink: Redesigning systems and care environments

Sustainability ultimately requires re-examining entrenched assumptions about how ICU care is organised and delivered. Routine practices such as automatic daily linen changes, paper-based documentation, decentralised monitoring, and redundant patient transport are increasingly being questioned in favour of approaches that reduce resource use while maintaining safety and comfort[31,32,39,44].

At the systems level, digital workflows, centralised monitoring, and tele-ICU models can reduce duplication, unnecessary transfers, and travel-related emissions while maintaining or improving clinical outcomes[51-53]. Infrastructure-level interventions, including energy-efficient building design, heat-recovery systems, renewable-energy integration, and non-potable water reuse, reduce operational emissions while strengthening resilience in continuously operating high-acuity environments[20,21,30,34].

Together, the 5 Rs provide a bedside-friendly implementation framework that embeds sustainability within routine clinical reasoning, operational stewardship, and system redesign (Table 3). Rather than competing with patient safety, many green ICU interventions reinforce high-reliability care by reducing low-value testing, unnecessary disposables, avoidable patient transport, excessive noise and light exposure, and inefficient workflows, thereby lowering iatrogenic harm, improving patient comfort, and supporting staff wellbeing (Figure 4).

Figure 4 Clinical co-benefits of sustainable intensive care practices. Selected sustainability interventions in the intensive care unit are associated with direct patient-centred and safety-related benefits. Reducing low-value testing, optimising energy and noise exposure, rationalising oxygen and medical gas use, minimising unnecessary disposables, and streamlining workflows not only lower environmental impact but also improve clinical outcomes, staff wellbeing, and system resilience. This figure illustrates how sustainability initiatives frequently align with established quality-improvement goals, challenging the perceived trade-off between environmental responsibility and high-quality critical care.

Table 3 The 5Rs of sustainability in the intensive care unit: Practical applications and clinical benefits.

Principle	ICU application	Clinical benefit
Replace/avoid	Avoid non-evidence-based tests (e.g., routine daily imaging or laboratory panels). Replace high-impact therapies where appropriate[31,35,37,44]	Prevents overtreatment. Reduces iatrogenic harm and patient discomfort. Lowers cognitive load
Reduce	Optimise medication preparation and overfill. Minimise overstocking, reduce unnecessary energy use and room entries[28,31,35,44]	Improves efficiency without compromising readiness. Reduces error risk and staff workload
Reuse	Use durable gowns and linens, metal instruments, reusable laryngoscope blades, reprocessable bronchoscopes[19,27,31,35,44]	Lowers waste and cost while maintaining infection-control safety and procedural reliability
Recycle	Segregate clean packaging, plastics, PVC items. Reduce red-bag waste through improved classification[15,16,18,31,35]	Reduces hazardous-waste costs, improves compliance. Engages frontline staff
Rethink	Re-evaluate routines, adopt tele-ICU and digital workflows, redesign care environments and infrastructure[31,35,44,52]	Enhances patient comfort, staff wellbeing, system resilience and innovation

Adapted from published intensive care unit sustainability consensus guidance and health-system decarbonisation frameworks. ICU: Intensive care unit; PVC: Polyvinyl chloride.

In parallel, infrastructure-focused interventions allow institutions to decarbonise critical care without altering bedside decision-making. Examples include on-site renewable-energy generation, building-efficiency retrofits, and wastewater-treatment systems for non-potable reuse-measures that reduce emissions while enhancing operational resilience in resource-intensive care environments (Figure 5).

Figure 5 Infrastructure-level sustainability interventions at a tertiary-care hospital in New Delhi, India (Holy Family Hospital). A: Rooftop solar photovoltaic installation providing on-site renewable electricity generation; B: Hospital wastewater treatment and reverse-osmosis system enabling treatment and non-potable water reuse; C: On-site biogas facility for organic waste conversion.

GOVERNANCE, SEQUENCING AND MEASUREMENT

While the 5 “Rs” provide a clinically intuitive framework, durable implementation depends on governance structures, appropriate sequencing of interventions, and robust mechanisms for measurement and accountability. Experience from health-system decarbonisation programmes shows that sustainability initiatives succeed when responsibility is distributed across clinical, institutional, and policy stakeholders and when interventions are staged across realistic implementation horizons rather than introduced as isolated projects[28,30,31,35,44]. To facilitate translation into practice, Table 4 provides a concise overview of short-, medium-, and long-term sustainability interventions across key stakeholder groups, while Supplementary Table 1 offers a detailed operational roadmap specifying bedside actions, institutional workflows, and policy levers.

Table 4 Timeline of sustainable intensive care unit interventions across implementation horizons.

Timeframe	Clinician actions	Administrator actions	Policymaker actions
Short (3-6 months)	Energy conservation, waste segregation, reusables, green teams	Recycling infrastructure, minor HVAC optimisation, audits	Guidance, pilot funding
Medium (6-18 months)	De-implementation of low-value care, protocol updates	Formal green plans, energy upgrades, procurement reform	Accreditation standards, infrastructure funding
Long (> 18 months)	Sustainability embedded in training, clinical leadership	Net-zero infrastructure, renewables, circular supply chains	Net-zero mandates, regulation

HVAC: Heating, ventilation and air conditioning.

At the clinical level, frontline teams can initiate rapid, low-risk changes, such as waste segregation, reducing unnecessary testing, and adopting reusable devices where appropriate. At the institutional level, administrators enable scale through procurement reform, infrastructure investment, workforce training, and integration of sustainability within routine quality-improvement and infection-control programmes. At the policy level, professional societies and regulators create the enabling environment through standards, accreditation criteria, reporting requirements, and financial incentives that normalise sustainable practice across health systems (Figure 6).

Figure 6 Implementation pathway for sustainable intensive care unit practice. Conceptual framework illustrating the staged integration of environmental sustainability into intensive care, progressing from clinician-led bedside actions (short term), to institutional and system-level integration (medium term), and finally to policy-level reinforcement (long term). The pathway is iterative, with early clinical data enabling institutional adoption and policy frameworks scaling and sustaining impact.

Effective sequencing is essential to maintain momentum while safeguarding patient safety. Early phases should prioritise low-regret actions with immediate co-benefits, followed by medium-term strategies such as formal ICU green plans, protocol integration, and device reprocessing pathways. Long-term transformation requires infrastructure redesign, decarbonisation of energy supply, circular procurement, and incorporation of sustainability metrics into executive governance and accreditation frameworks[28,31,35,44].

Measurement and continuous feedback underpin accountable implementation. Environmental indicators, including carbon footprint per ICU bed-day, energy and water consumption, compliance with waste segregation, and pharmaceutical waste, should be assessed alongside core clinical outcomes to preserve trust and clinical legitimacy (Table 5). Sub-metering, routine audits, and transparent reporting enable benchmarking and inter-institutional learning[7,20,21,31,35,43].

Table 5 Proposed outcome domains and measurement indicators for evaluating green intensive care unit initiatives.

Outcome domain	Indicator (examples)	Unit of measurement	Suggested frequency	Comments/rationale
Environmental impact	Carbon footprint per ICU bed-day	Kg CO2e/bed-day	Quarterly	Normalised to occupancy; life-cycle-based estimates where feasible
	Energy consumption	kWh/patient-day	Monthly	Adjust for seasonal variation and case-mix
	Water consumption	Litres/patient-day	Monthly	Includes dialysis, sterilisation, and cleaning processes
	Waste segregation compliance	% correctly segregated	Monthly audit	Proxy for staff adherence and training effectiveness
Pharmaceuticals and consumables	Drug wastage rate	% discarded doses	Monthly	Prioritise high-cost and high-volume medications
	Single-use device utilisation	Devices/patient-day	Quarterly	Tracks opportunities for rationalisation or substitution
Clinical safety and quality	Adverse event rate	Events/1000 patient-days	Quarterly	Sustainability initiatives must remain non-inferior to baseline outcomes
	ICU mortality and length of stay	% mortality; days	Quarterly	Ensures environmental actions do not compromise care
Economic sustainability	Cost savings from green initiatives	Local currency/year	Annual	Encouraged reinvestment into patient care or infrastructure
	Energy and waste disposal costs	Currency/bed-day	Quarterly	Captures financial co-benefits of sustainability measures
Organisational and cultural outcomes	Staff trained in green practices	% of ICU workforce	Annual	Proxy for institutional engagement and culture change
	Participation in green programmes	% participation	Annual	Reflects leadership support and behavioural adoption
Governance and scalability	Number of audits/reviews conducted	Count/year	Annual	Indicator of continuous improvement cycles
	Inter-institutional benchmarking	Yes/no	Annual	Facilitates knowledge sharing and policy integration

CO₂e: Carbon dioxide equivalents; ICU: Intensive care unit.

Finally, sustainability governance must be institutionalised to ensure durability beyond individual champions. Embedding environmental targets within executive performance indicators, quality dashboards, and accreditation standards signals that sustainable critical care is a core dimension of healthcare quality rather than an optional adjunct.

RESEARCH AGENDA AND KNOWLEDGE GAPS

Important evidence gaps remain that limit optimisation and large-scale adoption of sustainable ICU practice. ICU-specific LCAs are scarce and heterogeneous, with limited data from low- and middle-income countries and few diagnosis- or pathway-specific analyses. Standardised methodologies for estimating carbon footprint per ICU bed-day are needed to enable benchmarking and international comparison[7,9,11,20,21].

Prospective evaluation of safety, clinical outcomes, and cost-effectiveness is required for many interventions, particularly reuse, device reprocessing, and de-implementation strategies. Implementation science remains underdeveloped in this field, with limited understanding of behavioural, organisational, and governance determinants of sustained adoption in high-acuity environments[35,43,44,49].

Equity considerations warrant greater attention. Sustainable ICU models must be adapted for resource-constrained settings, where frugal innovation, repairability, and supply-chain resilience may offer both environmental and access benefits[39-42]. Addressing these gaps will be critical to establishing an evidence-based, globally relevant science of sustainable critical care.

CONCLUSION

ICUs are indispensable to modern healthcare, yet they represent among the most resource-intensive and carbon-intensive environments within hospital systems. This review demonstrates that meaningful reductions in the environmental footprint of critical care are feasible without compromising patient safety, clinical outcomes, or operational reliability. By identifying major emission hotspots, synthesising international experience, and proposing a pragmatic implementation framework grounded in the 5 “Rs”, we provide a blueprint for integrating sustainability into routine ICU practice.

The path forward requires coordinated action across clinical, institutional, and policy domains. Clinicians must lead stewardship of high-impact resources and de-implementation of low-value care. Hospital leaders must invest in infrastructure, procurement reform, and workforce engagement. Policymakers and professional societies must embed sustainability within accreditation, reporting, and financing mechanisms to normalise environmentally responsible care.

Importantly, sustainable ICU practice should be viewed not as a competing priority, but as an extension of high-quality, patient-centerd critical care. In the coming decades, the excellence of critical care may be judged not only by survival and safety, but also by how responsibly it delivers care within the planetary boundaries on which all future health depends.

ACKNOWLEDGEMENTS

The authors acknowledge Holy Family Hospital, New Delhi, for institutional support and permission to use hospital infrastructure-related images (including energy and water sustainability initiatives) for illustrative purposes in this manuscript.