Intended for healthcare professionals

Practice Practice Pointer

Towards net zero: critical care

BMJ 2023; 381 doi: (Published 01 June 2023) Cite this as: BMJ 2023;381:e069044
  1. Heather Baid, principal lecturer1,
  2. Eleanor Damm, specialty trainee2,
  3. Louise Trent, intensive care physician3,
  4. Forbes McGain, associate dean sustainable healthcare4
  1. 1School of Sport and Health Sciences, University of Brighton, Brighton, UK
  2. 2Intensive Care Medicine and Anaesthesia, Shrewsbury and Telford Hospital NHS Trust, Shrewsbury, UK
  3. 3Hawke’s Bay Hospital, Te Matau a Māui, Te Whatu Ora, New Zealand
  4. 4Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Carlton, Australia
  1. Correspondence to: H Baid H.Baid{at}

What you need to know

  • Critical care is resource intensive, using large amounts of energy, pharmaceuticals, and single-use consumables, all of which potentially have a harmful impact on the environment

  • We can view environmental sustainability in critical care via the framework: avoid, reduce, reuse, recycle, rethink, and research

  • Reducing the carbon footprint and resource use of critical care will require a committed effort across all healthcare professions, engineering, waste management and procurement services, along with hospital, industry, and government leadership

A 60 year old woman with diabetes and hypertension is admitted overnight to the intensive care unit (ICU) with covid-19 and an unfolding septic shock. She is intubated and mechanically ventilated with associated humidification, piped oxygen, and air. Multiple intravenous infusions are required; nasogastric feeding and continuous renal replacement therapy are initiated. The nurses are in personal protective equipment (PPE). The ICU’s heating, ventilation, and air conditioning (HVAC), lighting, and machines are running. There is a large singular clinical waste bin, as waste segregation has been discontinued since the beginning of the covid-19 pandemic.

Everything mentioned in this scenario, seen in ICUs worldwide, has a carbon, resource, and waste footprint. Not all actions and processes that generate that carbon footprint, resource use, and plastic waste are essential for patient care. With ICUs generating significantly higher amounts of greenhouse gas emissions and solid waste per bed day in comparison with an acute care ward,1 there is a need for the ICU multidisciplinary team to address the environmental sustainability issues raised in this scenario.

What is the problem? Environmental burden and hotspots of critical care

The healthcare sector is responsible for 4-5% of global greenhouse gas emissions2; if it were a country, it would be the fifth highest emitter on the planet.3 ICUs are a considerable contributor to the carbon footprint of hospitals.14Box 1 shows the carbon hotspots (areas with largest carbon emissions) in critical care. Clinicians can lower the ICU’s environmental burden through awareness of these carbon hotspots and by integrating carbon reduction in decision making and activities in clinical practice while continuing to provide high quality care.

Box 1

Carbon footprinting and carbon hotspots in critical care

  • Life cycle assessment (LCA) is a scientific method that analyses the environmental footprint of products and processes, including CO2, energy, water use, and pollution (aquatic, terrestrial, and atmospheric). Carbon and other environmental footprinting of all healthcare practice is a pressing issue.

  • LCAs are becoming more frequent in critical care, with several formal studies specific to the intensive care unit (ICU).145

  • The ICU is a carbon hotspot within the hospital because it is always active, often has higher rates of room airflow (and thus heating, ventilation and air conditioning (HVAC)), and greater consumable use compared with general hospital wards.1

  • Carbon hotspots within the ICU include energy use (particularly HVAC), pharmaceuticals, and medical equipment.

  • ICU machines (ventilators, dialysis, intravenous pumps, etc) use relatively little electricity (<10%) compared with HVAC.

  • Difficulties with LCA studies in critical care include small samples, differing patient treatments, issues with how the carbon footprint of pharmaceuticals and pathology testing are undertaken, and dissimilar energy sources and practices.

Studies that have investigated the carbon footprint of intensive care

  • One study from the UK found that electricity use for ICU machines and lighting was 15 kWh per patient per day (similar to the energy use in a standard four-person household in a higher resource setting).5

  • An LCA of 20 patients with septic shock found that the greenhouse gas emissions were approximately 90 kg and 180 kg CO2 per patient per day for the Australian and US ICUs respectively (that is, equivalent to using 40 and 80 litres of petrol used/day respectively).4 Energy (electricity and gas) for HVAC dominated total ICU energy use (90% total) with lesser contributions from lighting, patient machines, bedside equipment, and computers. More than 75% of these greenhouse gas emissions stemmed from ICU energy with ICU machines, with procurement of consumables and equipment, and waste making up the remainder.

  • A US study used a hybrid life cycle method to compare the environmental footprint of an ICU with a general ward in a single hospital.1 It found that the carbon footprint associated with treating patients in ICU was three times that of a general ward (138 kg CO2e v 45 kg CO2e).


What are the solutions? Avoid, reduce, reuse, recycle, research, rethink

Many different actions can be taken to decrease the environmental footprint of critical care. An individual clinician should consider the balance between the most impactful intervention and taking an action that is feasibly within their control, which may not be the largest carbon footprint. The key to environmental footprint improvement involves avoiding, reducing, reusing, and recycling without compromising safe, quality care, with simultaneous research into best practices and rethinking how ICUs can be more sustainable.6 The infographic summaries these principles and how they can be applied in intensive care departments. This systems based approach is underpinned by the UK Centre for Sustainable Healthcare’s “principles of sustainable clinical practice,” which encourages sustainability through prevention, patient empowerment and self care where possible, lean service delivery, and low carbon alternatives.7

Avoid: prevent unnecessary admissions and readmissions

Primary prevention to avoid illness or injury stems from wider societal changes and public health promotion, which is beyond the immediate scope of those working in ICUs but is an important aspect of sustainability.

Intensivists play a difficult role in assessing patients to ensure that only those who will likely benefit from intensive care interventions are treated in their units and that the care offered is concordant with the patient’s goals and values.8 Prevention of inappropriate intensive care admissions and readmissions is an important aspect of resource stewardship, and improving ICU triage practices may result in more efficient ICU use. Country-specific and hospital-level solutions that optimise ICU supply with demand may reduce costs without negatively affecting patient outcomes.9 Discussions with patients over their goals of care mean that patients are more likely to receive treatment consistent with their wishes to avoid unwarranted and unwanted treatments if they deteriorate. System-focused changes can improve the chances that all patients have an appropriate goal of care decision. This could include clinician education, quality improvement, and development of hospital policies.

Critical Care Outreach services aim to avoid and reduce critical care admissions through earlier detection and treatment of deteriorating patients, and readmissions after ICU discharge with follow-up and conversation over goals of care. However, evidence for the clinical and economic effectiveness of outreach and rapid response teams is of variable quality.1011

Enhanced recovery pathways and pre-habilitation for surgical patients may reduce postoperative complications,12 reducing the need for ICU care. The Getting it Right First Time report for adult critical care highlighted the importance of national postoperative care pathways, 24/7 availability of critical care outreach, advance care planning and shared decision making with patients and carers, multidisciplinary rehabilitation, and follow-up pathways after critical care.13

Another way to avoid ICU admission is to deliver some care traditionally delivered in the ICU in a high dependency, step-down or high acuity ward. In some instances, this can be done safely, although nursing ratios need to be carefully monitored. For example, one US study found that patients managed with non-invasive ventilation for chronic obstructive pulmonary disease outside the ICU had similar outcomes as patients treated in the ICU and reduced invasive interventions.14 Furthermore, the covid-19 pandemic has stimulated innovations for surge beds outside ICU.

Reduce: optimise length of stay

Improving patient outcomes, while also minimising the supplies and equipment needed for organ support, can be achieved through the ABCDEF bundle elements (assess pain; both spontaneous awakening and breathing trials; choice of sedation; delirium management; early mobility; family engagement).15 Use of such an ABCDEF bundle in the ICU has shown clinically meaningful improvements in morbidity and mortality.15 Despite the usual ICU challenges, asking awake patients or families about their preferences and encouraging active participation in decision making and care where possible promotes person-centredness, which in our experience can reduce unnecessary use of resources and lower the ICU’s carbon footprint.

Time-limited trials are when intensive care treatments are trialled for a set period of time; at the end of this time, the treatments are assessed and discontinued if there is no meaningful improvement. Careful time-limited trials in the ICU can successfully reduce ineffective stays in the ICU without increasing mortality.16 Optimising appropriate discharge to prevent an unnecessarily prolonged ICU stay17 also brings patient, financial, and environmental benefits.

Avoid and reduce: tackling low value care

“Less is more in the ICU” is not a novel concept.1819 Individual clinicians daily undertake indirect ICU environmental sustainability efforts based on evidence based medicine guiding us away from unnecessary therapies. There is ongoing need to ensure that other potentially harmful or ineffectual therapies, such as intensive insulin therapies or unnecessary blood transfusions, are not used.18 Likewise, there is some evidence that taking a more restrictive approach to fluid administration might reduce morbidity and mortality, but larger trials are needed.20

As an example of low value ICU care, a US study based in five academic hospitals surveyed critical care specialists daily for three months. It found that 464 treatment days were viewed as ineffective or futile, representing 6.7% of all assessed patient days.21 The treating physician thought that, on the days that patients were receiving ineffective therapy, the burdens grossly outweighed the benefits, the patient would die outside an ICU, the patient was permanently unconscious, the treatment could not achieve the patient’s goals, or death was imminent.21 Avoiding ineffective or futile treatments should, firstly, be for the patient’s benefit; reducing the ICU’s environmental footprint is a co-benefit. Avoidance of ineffective therapy requires medical leadership and excellent communication skills with ICU patients, their families, and other hospital staff.

Similarly, avoiding or reducing ineffective (and possibly harmful) tests and therapies such as daily chest x rays or blood tests leads to wider economic, and environmental gains.22 A meta-analysis showed that reducing routine diagnostic testing when not needed was safe (no significant differences in mortality or adverse events) and lowered costs if chest x rays and blood tests were only done when clinically relevant rather than daily.23 Evidently, there are medical, financial, cultural, and wider societal expectations of what constitutes ineffective therapy necessitating skilful navigation.

Simple “reduce” actions multiplied at scale are impressive and motivating. A 2020 study showed that a safe 30% reduction in total ICU arterial blood gas tests in one Australian ICU could, if extrapolated to all Australian and New Zealand ICUs, result in savings of A$33 million, 4400 L of blood, labour equal to 40 full time staff, and unmeasured environmental benefits.24 In another study, implementation of a new guideline and education package in one department more than halved rates of clotting profile testing.25


It is now rare to see reusable items in ICUs in higher income countries. Critical assessment of all single-use consumables is needed, and analysis of when return to reusables is feasible and safe. Reusables are mostly more economical and become more ecologically favourable when the electricity source shifts to renewables.26 Such a shift from single use to reusable items will be part of healthcare’s transition to low carbon. Discussions with infection prevention colleagues at all levels about how to begin the path to environmental sustainability are urgently necessary.2728

Simple reusable alternatives in ICU include blood pressure cuffs, pulse oximeters, and laryngoscopes.27 As an example, one study found that: “For all use and cleaning scenarios, the reusable blood pressure cuff was environmentally preferable in terms of greenhouse gas (GHG) emissions and other impact categories, in some cases by a factor of 40.”29 Creating procedure packs for central line insertion with reusable metalware, surgical trays, containers, drapes, and gowns will save money and reduce waste.30 However, whether these kits have a reduced carbon footprint depends on the fossil fuel dependency of the hospital,30 highlighting the importance of advocating for a switch to more renewable energy within healthcare settings.

During the covid-19 pandemic there has been expanding interest in replacing disposable personal protective equipment gowns with reusable ones.31 These gowns can provide increased protection and comfort and be economically superior.32 One study found that reusable gowns reduced GHG emissions by approximately two thirds and water consumption and solid waste generation by approximately 80% compared with disposable gowns.33 Medical reprocessing of single-use devices to be patient ready again is another reusable alternative, which the US Food and Drug Administration has stated can in some circumstances be done safely with no increased infection risk.34 Some single use items such as oxygen delivery devices could stay with the patient through their hospital journey.


If “avoid, reduce, or reuse” is not feasible, clinicians should maximise recycling if available. In one pre-covid study, approximately 15% of total ICU waste was recycled, with recycling of a further 15% of waste possible (about half of this 15% being paper or cardboard and at least a third being recyclable plastics).35 Successful ICU recycling requires vigilance; ICU nurses are integral. A waste audit can be one way of measuring success. Make recycling as easy as “wasting”: call for champions, encourage the enthused, educate everyone often about the benefits (environmental, financial, and importantly psychosocial), provide labelled bedside plastics and paper containers, integrate environmental services and cleaners, and remember that behaviour change needs nurturing.

What’s the evidence for change?

Table 1 outlines daily ICU care with sustainability co-benefits. The actions listed in table 1 are to promote “reduce” solutions to improve healthcare sustainability because of the lack of low carbon clinical alternatives, unlike in other specialties (such as choice of anaesthetic). Box 2 offers departmental level suggestions. The content in the table and box was informed by the ANZICS environmental sustainability toolkit,6 which stemmed from efforts and conversations held over several years.

Table 1

Examples of bedside “reduce” actions for intensive care

View this table:
Box 2

Environmental sustainability in the ICU

Behavioural and cultural practice change

  • Create a team culture of rethinking sustainability across all parts of the ICU and beyond and make environmental sustainability the status quo

  • Form, lead, or simply encourage an ICU sustainability committee; network with other ICU green groups

  • Learn from wider hospital sustainability groups and share environmental sustainability gains within the ICU and beyond

  • Embed sustainability into intensive care quality and safety activities

  • Apply a sustainability lens to all ICU quality and safety activities. Quality improvement projects can include evaluation of clinical, environmental, financial, and social resourcing implications.64 Introduce new and improve existing sustainability actions through QI cycles

  • Know the research behind “less is more” in the ICU and integrate it into departmental policies, guidelines, and procedures

  • Encourage departmental sustainability research and review sustainability research and “less is more” publications in journal clubs

  • Create decision-making aids that reduce unnecessary testing and drugs, minimise stock at the bedside, rotate consumables so they do not expire, and make procedure packs as streamlined as possible

  • Be evidenced based with infection prevention and control policies, and reduce, reuse, and recycle PPE where possible

Intensive care procurement and upstream supply

  • Promote intensive care representation in hospital, regional, and nationwide procurement groups and include life cycle assessment and environmental sustainability considerations and targets in the purchasing of equipment and consumables for ICUs

  • Work with government and industry to encourage, then mandate, environmentally preferable ICU purchasing and product stewardship

  • Consider reusable equipment whenever new and replacement items are considered. Develop policies for rational use of single-use devices

  • Choose safe cleaning products and chemicals in the ICU and use biodegradable and reusable products where possible

  • Systematically review ICU consumables list and replace items with more sustainable options, delete items you do not need, and consider circular supply chains and medical device reprocessing. Question why each item needs to be disposable

ICU facility and built environment

  • Work with hospital engineers and standards organisations to encourage, then mandate, renewable electricity

  • Promote ICU energy conservation initiatives, including behavioural (turning off lights and air ventilation in individual rooms and isolation rooms when not in use) and automated (sleep mode on computers and equipment shut-off rather than standby). Share data about energy savings in your ICU

  • Adhere to the highest green building/retrofitting standards, consider biophilic design, use natural lighting, create nature spaces for patients and staff, and design the built environment to reduce waste and recycle easily, taking into account space limitations

  • Optimise bedspace, waste management, and supply storage areas to make sustainable options the most convenient and easily accessible

ICU waste

  • Correct waste segregation through education, and create efficient systems and collection points in ICU or hospital. Do a waste audit. Hospital sustainability and waste minimisation staff can establish meaningful organisational change

Intensive care meetings, training, professional development, education

  • Offer virtual attendance at work and departmental virtual conference subscriptions (consider making an event of it) to prevent unnecessary travel

  • Consider whether each professional development activity needs to be attended in person. If choosing to attend in person, choose the lowest-carbon travel method. For international conferences, consider whether collaboration and socialising at international conferences can be achieved with local offshoot meetings and gatherings

  • Incorporate education about sustainability solutions into curriculum for trainees, staff induction, and regular education cycles

  • ICU conferences and events should strive to be carbon neutral (minimise, measure, and offset) and zero waste, and include sustainability content

Staff wellbeing, advocacy, and job satisfaction

  • Encourage and support active travel and public transport to work

  • Promote staff wellness, including mental health awareness, healthy and planetary diets, exercise, and integrative therapies

  • Create green space for staff, patients, and families and aim for a zero waste staffroom

  • Improve job satisfaction through a sustainable work setting that promotes the health of patients, families, staff, and the planet to create a place where people feel proud to work


Many of the environmental sustainability recommendations in table 1 and box 2 are self-explanatory or supported by standard ICU literature. Research on ICU clinical topics, such as appropriate PPE or oxygen usage, with a sustainability lens will help to establish how to provide safe, high-quality intensive care that optimises clinical outcomes delivered sustainably. Further research is required to clarify the ICU carbon footprint in countries not previously studied and how ICUs can best improve on sustainability.

What next? Areas for further development

Three domains of the planetary health framework2665 could be adapted by ICU clinicians: (i) decarbonise healthcare (including reduce, reuse, recycle), (ii) match healthcare supply with demand, and (iii) reduce healthcare demand. In each domain, there are three action levels: the individual, the hospital, and professional groups, regulators, and government.26

Research funding, health promotion advocacy, and policy development by critical care colleges, societies, and patient and consumer groups are needed. Working with hospital executives and boards, critical care organisations can influence the healthcare industry to urgently move towards providing low carbon alternatives for clinical supplies and circular economy opportunities. The critical care community also needs to facilitate systemic, cultural, and large scale behaviour change to normalise carbon footprint and resource reduction within critical care. For healthcare professionals to have the capability, opportunity, and motivation66 to embed environmental sustainability efforts into their daily clinical practice, education courses, conferences, research, quality improvement, and leadership initiatives will be vital. The time is now for a collaborative, collective approach enabling critical care’s journey towards net zero. All countries should be encouraged to consider their responsibilities to planetary health. This is increasingly becoming a statutory requirement in national healthcare systems.67

Environmentally sustainable critical care in resource limited settings

Low and middle income countries have a high premature death rate of 8.6 million/year from causes that “should not occur in the presence of timely and effective healthcare.”68 A 2015 review found that, more than insufficient access, poor quality care was the biggest barrier to reducing mortality.69 A greater burden of critical illness and worse outcomes have been observed in low resource settings, attributable to fragmented healthcare systems, cost, limited education, and competing healthcare priorities.70 Controversially, healthcare provision in at least some low and middle income countries has a larger carbon intensity, likely due to differences in energy sources.71 As overall provision grows,72 for global healthcare to be sustainable over the long term, it also needs to reduce carbon emissions.

Capacity for critical care in resource limited settings is only 0.1-2.5 beds per 100 000 people, compared with 5-30 beds per 100 000 in higher resource settings.68 The traditional model of intensive care is often unattainable given the restraints in staffing and resources. Equipment cost may be higher because of importation taxes and non-competitive pricing structure.68 Additionally, increased complications in low resource settings from lack of trained staff and limited infection control measures increase morbidity and mortality, cost, and resource use.68 Critical care patients and diseases also differ in lower resource settings, so protocols and practices developed elsewhere may not be relevant. Countries need to study their own population and tailor interventions to local needs to be most effective.73

Staff and fixed asset equipment are the main critical care costs in resource limited settings (as opposed to consumables and medication). The emergence of new technologies (for example, low cost wearable devices such as fitness trackers and hand-held ultrasound devices), increased use of artificial intelligence, and telemedicine may positively transform critical care delivery, allowing for expansion and improved quality while also reducing costs and resource use.68 Difficulty in accessing basic resources such as running water, electricity, and oxygen has seen the move to alcohol hand gels,73 solar powered oxygen concentrators and energy storage,74 and safe reuse of consumables such as non-invasive blood pressure cuffs or ventilator circuits. Lessons learned in higher resource countries can also be implemented, such as switching to LED lights, using low carbon pharmaceuticals (such as propellent-free inhalers), and healthcare professionals’ advocacy.71 The biggest hurdle for quality improvement and critical care expansion in lower income settings lies elsewhere, with up to 77% of critical care units lacking appropriately trained staff.73

How healthcare settings with limited resources can increase quality of care (thereby reducing morbidity, mortality, and economic loss but also ensuring resources available are used efficiently) is laid out in the Lancet Global Health Commission.69 Others have described ways that a low carbon, sustainable healthcare system can be developed alongside this.71 The race is on to provide equitable, safe, high-quality critical care in all countries with maximum effect and minimal resource use.

Patient commentary

When I was an intensive care patient, and on the ward afterwards, I observed staff using large amounts of disposable things like gloves, dressings and little plastic pots for medicine tablets that got thrown out after one use. There seemed to be a huge amount of waste disposed of in the general bins, but I did not see any recycling happening, and I used to wonder if there could have been recycling made possible for the staff in both the ward and intensive care unit. As a patient, you also see a lot of packaging being thrown out rather than being recycled. Obviously, healthcare products do need to be used, and many will be sterile for the necessary hospital treatments, but I wonder if there are alternatives or some way of providing this care in a more environmentally sustainable way.

I was in intensive care for 13 days and did not go outside during that time, plus my bed was facing away from the window, which meant I could not see outside until I went to the ward, where I had a bed next to a window. I was taken outside for physiotherapy while on the ward, and when I went outside for the first time I realised I was still alive and the world was still turning, and it made such a difference to my recovery. I feel that things that helped me to recover faster were fresh air, feeling the sun on my face, and natural light. I wish I could have gotten outside or even been able to look out the window when I became more awake in intensive care. If patients recover from intensive care faster, then they won’t need as many treatments, which create a carbon footprint.

Education into practice

  • How can you set up, or develop further, a team of environmental sustainability champions in your local critical care unit who will educate colleagues and help to normalise the principles of sustainable clinical practice?

  • How can you communicate with your hospital to contribute ideas and suggestions for reducing the environmental footprint and resource use of your local critical care unit by improving sustainability within energy use, procurement of clinical supplies, and waste management?

How this article was created

This article offers a critical care focus within The BMJ series on Towards Net Zero Healthcare drawing from the clinical, research, education, and sustainability experiences of the authors, as well as academic publications found by all authors searching the literature. The ANZICS Sustainability Toolkit6 also informed the practical recommendations within the article.

How patients were involved in the creation of this article

Louise Gallie, as a former critical care patient, provided the patient commentary, contributed to the patient empowerment and self care ideas, and reviewed the draft manuscript.


We acknowledge the assistance of Frances Mortimer for this article’s initial conceptualisation, and also thank The BMJ and the Centre for Sustainable Healthcare for the invitation to contribute to this Towards Net Zero Healthcare series.


  • Contributors: HB, ED, and FM conceived the initial article format, following the Centre for Sustainable Healthcare’s principles of sustainable clinical practice. LT provided a later contribution to the article design. All authors wrote the first draft, with table 1 and box 2 created by FM and LT. HB was the contact for patient involvement; the authors thank Louise Gallie for her patient perspective contribution. All authors contributed to editing, reviewed the final manuscript, and are guarantors.

  • Competing interests: The BMJ has judged that there are no disqualifying financial ties to commercial companies. The authors declare the following other interests: FM has received grants related to healthcare environmental sustainability from the National Health and Medical Research Council, and the Australian and New Zealand College of Anaesthetists and College of Intensive Care; LT and FM were in the working group which developed the ANZICS Sustainability Toolkit; HB has received grants for healthcare environmental sustainability projects that were funded by the University of Brighton Rising Stars award, the British Association of Critical Care Nurses and Research England. Further details of The BMJ policy on financial interests is here:

  • Provenance and peer review Commissioned; externally peer-reviewed.