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

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.