The carbon footprint of treating patients with septic shock in the intensive care unit

Objective: To use life cycle assessment to determine the environmental footprint of the care of patients with septic shock in the intensive care unit (ICU). Design, setting and participants: Prospective, observational life cycle assessment examining the use of energy for heating, ventilation and air conditioning; lighting; machines; and all consumables and waste associated with treating ten patients with septic shock in the ICU at Barnes-Jewish Hospital, St. Louis, MO, United States (US-ICU) and ten patients at Footscray Hospital, Melbourne, Vic, Australia (Aus-ICU). Main outcome measures: Environmental footprint, particularly greenhouse gas emissions. Results: Energy use per patient averaged 272 kWh/day for the US-ICU and 143 kWh/day for the Aus-ICU. The average daily amount of single-use materials per patient was 3.4 kg (range, 1.0–6.3 kg) for the US-ICU and 3.4 kg (range, 1.2–8.7 kg) for the Aus-ICU. The average daily particularly greenhouse gas emissions arising from treating patients in the US-ICU was 178 kg carbon dioxide equivalent (CO₂-e) emissions (range, 165–228 kg CO₂-e), while for the Aus-ICU the carbon footprint was 88 kg CO₂-e (range, 77–107 kg CO₂-e). Energy accounted for 155 kg CO₂-e in the US-ICU (87%) and 67 kg CO₂-e in the Aus-ICU (76%). The daily treatment of one patient with septic shock in the US-ICU was equivalent to the total daily carbon footprint of 3.5 Americans’ CO₂-e emissions, and for the Aus-ICU, it was equivalent to the emissions of 1.5 Australians. Conclusion: The carbon footprints of the ICUs were dominated by the energy use for heating, ventilation and air conditioning; consumables were relatively less important, with limited effect of intensity of patient care. There is large opportunity for reducing the ICUs’ carbon footprint by improving the energy efficiency of buildings and increasing the use of renewable energy sources.