THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY ORIGINAL Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. Published online 22 February 2015 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/rcs.1640
ARTICLE
Carbon footprint of robotically-assisted laparoscopy, laparoscopy and laparotomy: a comparison Demetrius L. Woods1* Thomas McAndrew2 Nicole Nevadunsky2 June Y. Hou2 Gary Goldberg2 Dennis Yi-Shin Kuo2 Sara Isani3 1
Emory University School of Medicine, Department of Obstetrics and Gynecology, Emory Midtown Hospital, Atlanta, GA 30308, USA
2
Albert Einstein College of Medicine, Division of Gynecologic Oncology, Montefiore Medical Center, Department of Obstetrics and Gynecology and Women’s Health, Bronx, NY, USA
3
Robert Wood Johnson Medical School, Division of Gynecologic Oncology, Department of Obstetrics, Gynecology and Reproductive Science, New Brunswick, NJ, USA *Correspondence to: D. L. Woods, Emory University School of Medicine, Department of Obstetrics and Gynecology, Emory Midtown Hospital, 550 Peachtree St NE, 8th Floor, Medical Office Tower, Atlanta, GA 30308, USA. E-mail: [email protected]
Accepted: 18 December 2014
Copyright © 2015 John Wiley & Sons, Ltd.
Abstract Background To date there have been no comprehensive, comparative assessments of the environmental impact of surgical modalities. Our study seeks to quantify and compare the total greenhouse gas emissions, or ’carbon footprint’, attributable to three surgical modalities. Methods A review of 150 staging procedures, employing laparotomy (LAP), conventional laparoscopy (LSC) or robotically-assisted laparoscopy (RA-LSC), was performed. The solid waste generated (kg) and energy consumed (kWh) during each case were quantified and converted into their equivalent mass of carbon dioxide (kg CO2e) release into the environment. The carbon footprint is the sum of the waste production and energy consumption during each surgery (kg CO2e). Results The total carbon footprint of a RA-LSC procedure is 40.3 kg CO2e/ patient (p < 0.01). This represents a 38% increase over that of LSC (29.2 kg CO2e/patient; p < 0.01) and a 77% increase over LAP (22.7 kg CO2e/patient; p < 0.01). Conclusions Our results provide clinicians, administrators and policymakers with knowledge of the environmental impact of their decisions to facilitate adoption of sustainable practices. Copyright © 2015 John Wiley & Sons, Ltd. Keywords
robotic surgery; gynaecology; sustainability; endometrial cancer
Introduction The ’carbon footprint’ is a quantitative measure of the direct and indirect total greenhouse gas emissions attributable to a process, product, institution or industry (1). The process of carbon footprinting yields a quantifiable output expressed in the equivalent mass (kilograms, kg) of carbon dioxide (CO2) release into the environment [CO2 equivalents (CO2e)]. Assessment methodologies and standards for the carbon footprinting process are maturing in the transportation, construction, manufacturing and technology industries (2–4). The healthcare industry is responsible for 7% of the total US CO2 gas emissions
407
Carbon footprint comparison of laparoscopic procedures
(6103 million metric tons CO2e), yet little quantitative research exists on the environmental impact of its component processes (5). Existing carbon footprinting research in healthcare has focused largely on the transport-associated greenhouse gas (GHG) emissions from supply procurement, waste disposal, patient and healthcare staff travel (6–10). Travel to and from healthcare facilities, excluding any direct healthcare activities that occur within, accounts for as much as 38% of the GHG emissions associated with healthcare services (7,9). Energy consumption and landfill waste production, however, account for the majority of the environmental effect of the healthcare industry (12–19). Of US energy, 9% is consumed by the healthcare industry to support energy-intensive medical equipment, including high-intensity lighting and 24 h operating schedules (14). Operating rooms contribute 20–30% of hospital waste production and, together with labour and delivery units, account for 70% of the 6600 tons of waste produced by US hospitals each day (14,18,20,21). Packaging materials alone account for up to 40% of regulated medical waste from operating rooms (22–24). Collectively, these studies are useful in their ability to quantify the carbon footprint of healthcare delivery but the field lacks comparative data on different methods available to achieve a clinical outcome. The paucity of data regarding the environmental impact of the 48 million surgical procedures performed annually prompted our comparison of the carbon footprint of three specific surgical modalities for endometrial cancer staging: laparotomy, conventional laparoscopy and robotic-assisted laparoscopy (25). Our research intends to quantify the carbon footprint of the procedures based on their energy consumed and waste produced. We hypothesized that a significant difference in the carbon footprint exists between the three surgical modalities.
Methods
Administration and previous carbon footprinting studies, such that disposal of 1 kg waste in a municipal landfill is considered equivalent to 1 kg CO2 greenhouse gas (CO2e) release into the environment (26–28). Energy consumption in kWh was converted to CO2e using the National Energy Foundation (NEF) calculator conversion factor of 0.54 kg CO2e/kWh (27).
Patient selection A retrospective review of the 50 consecutive and most recent patients to have undergone a staging procedure for endometrial cancer was conducted for three surgical modalities: robotically-assisted laparoscopy (RA-LSC), conventional laparoscopy (LSC) and laparotomy (LAP). This study received exemption from the Institutional Review Board of the Albert Einstein College of Medicine of Yeshiva University. Clinical data from those 150 staging procedures spanning the years 2008–2011 were then abstracted from patient charts, operating room records and anaesthesia records. Information collected included patient age, body mass index (BMI), procedure type, operative time, history of prior abdominal surgery, length of stay, uterine weight and instruments used. Waste production and energy expenditure were determined and used to calculate the primary outcome measure, total carbon footprint, for each surgical modality, expressed in kg CO2e. Our investigation calculated the carbon footprint as the sum of each procedure’s associated solid waste production (kg) and energy consumption (kilowatt-hours, kWh), using the methodology described in Figure 1.
Waste production Waste is categorized by production source and quantified in the manner described in Figure 1. Waste production was determined based on operating room instrument data specific to each modality, and is assumed to be identical within a modality but differ across modalities.
Carbon audit
Energy consumption
Standards, definitions and assessment methodology for the carbon footprinting process described in our analysis are adapted from the British Standards Institute Publicly Available Specification 2050 (BSI PAS 2050) and the Greenhouse Gas Protocol published by the World Business Council for Sustainable Development and the World Resources Institute (3,4). Data on energy and waste greenhouse gas equivalents were obtained from the National Energy Foundation, the US Energy Information
The energy consumption/unit time (kwh) for every energy-consuming device utilized during the surgery was calculated based on independent source data, as described in Figure 1. All energy consumption was categorized as environmental, equipment, instrument and robotic system, based on function. The operative time (min) was determined from individual operative reports. Operative time was then multiplied by the total energy consumption/unit time of all four categories to
Copyright © 2015 John Wiley & Sons, Ltd.
Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
D. L. Woods et al.
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Figure 1. Methodology for carbon footprint determination
establisha unique energy consumption value for each of the 150 surgeries.
Statistical analysis All tests of continuous variables were compared via Student’s t-test, Kruskal–Wallis test or ANOVA methodology where appropriate. Multiple comparisons were controlled for via Bonferroni’s method. Categorical variables were compared using Pearson’s χ 2 test. BMI and uterine weights differed significantly and their effect on operative time was controlled for, due to possible confounding. Association between length of procedure and co-variables were modelled using ANOVA methodology. All tests were held at α-level of 0.05. Copyright © 2015 John Wiley & Sons, Ltd.
Results The total carbon footprint for all 150 endometrial staging procedures, including solid waste produced and energy consumed, was equivalent to 4498 kg CO2e, averaging 30 kg CO2e/patient (p < 0.01). Age and history of prior abdominal surgery did not differ significantly between groups (p = 0.33; p = 0.72). Uterine weight and body mass index (BMI) differed significantly between groups and were analysed using logistic regression (p < 0.05; p < 0.05). The characteristics of the study population by surgical modality are described in Table 1. We determined that the total carbon footprint of an RALSC for endometrial cancer staging was 40.3 kg CO2e/patient (p < 0.01). This represents a 38% premium over laparoscopy (LSC) at 29.2 kg CO2e/patient and a 77% increase over laparotomy (LAP) at 22.7 kg CO2e/patient (p < 0.01; p < 0.01). Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
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Carbon footprint comparison of laparoscopic procedures Table 1. Characteristics of the study population by surgical modality
Age (years) 2 BMI (kg/m ) Prior abdominal surgery (%) Uterine weight (g)
RA-LSC (n = 50)
LSC (n = 50)
LAP (n = 50)
63.0 36.2 28/50 (56%) 205.1
60.3 31.5 26/50 (52%) 166.31
62.7 35.3 30/50 (60%) 495.47
p* 0.33* < 0.05* 0.72** < 0.05*
*Student’s t-test. 2 **Pearson’s χ test.
of the total energy in those cases, while LAP equipment consumed 4% of the total energy. In the RA-LSC group, equipment (excluding the da Vinci Surgical System) consumed 5.2% of the total energy in each case. The da Vinci surgical system (Intuitive Surgical; Sunnyvale, CA, USA) equipment, however, accounted for 41% of each RA-LSC procedure’s energy carbon expenditure (Figure 2). In each modality, the instrument energy consumption was considered negligible, accounting for < 1% of energy usage in each staging procedure.
Energy
Waste
The three surgical modalities were comparable in the relative contribution of energy consumed to the total carbon footprint, with RA-LSC energy consumption accounting for 61% of each procedure’s total carbon footprint, LSC at 61.5% and LAP at 63.4%. The absolute energy consumption, however, differed between the approaches. RA-LSC equated to 26 kg CO2e/patient compared to LSC, which equalled 18 kg CO2e/patient, and LAP, at 14.4 kg CO2e/patient (ANOVA p < 0.01). The operative times for each procedure were as follows: RA-LSC, 375.2 ± 92.96 min, LSC 409.06 ± 90.6 min and LAP 243.9 ± 65.07 min (p < 0.01) (Table 2). Energy consumption was categorized and quantified as defined in Figure 1. The environmental energy use was comparable among the three types of cases: RA-LSC, 26 kg CO2e/patient; LSC, 18 kg CO2e/patient; and LAP, 14.4 kg CO2e/patient. Environmental energy was also the largest area of consumption: 95% of total LAP energy, 85% of LSC and 53% of RA-LSC energy consumption (Table 2). The LSC group had the highest equipment energy use, at 4.77 kg CO2e/patient. This was followed by RA-LSC, at 2.62 kg CO2e/patient, and LAP, with 1.12 kg CO2e/ patient (Table 2). The LSC equipment consumed 14.05%
The average solid waste production/patient was 11.27 kg CO2e for all surgical modalities combined (Table 2). The LAP group produced the least amount of solid waste, 8.3 kg CO2e/patient, when compared to RA-LSC (14.3 kg CO2e/patient) and LSC (11.24 kg CO2e/patient). The solid waste production of RA-LSC represented a 74% premium over LAP and a 36% increase over LSC. Waste production was assumed to be the same among all 50 surgeries within a modality but to differ across surgical modalities (Figure 2). For that reason, our analysis reports no standard deviation (SD) for this variable. Consumable waste Consumable waste was similar in all three modalities: RA-LSC, 6.90 kg CO2e/patient; LSC, 6.03 kg CO2e/patient; and LAP, 5.86 kg CO2e/patient (Table 2). Consumable waste was the largest contributor to solid waste: RA-LSC, 48.3%; LSC, 53.6%; LAP, 70.8%. Single-use device LSC generated the largest amount of single-use device waste, at 3.35 kg CO2e/patient; RA-LSC produced 2.47 kg CO2e/patient with LAP at 0.82 kg CO2e/patient. RA-LSC single-use device waste accounted for 16.7% of total waste, LSC 29.7% and LAP 9.7%.
Table 2. Total kg CO2e equivalents produced by surgical modality
Energy kWh (SD) Environmental (kWh) da Vinci (kWh) Equipment (kWh) Instrument (kWh) Operative time (min) (SD) Energy CO2 (kg) Waste (kg) Infection control (kg) Single-use device (kg) Consumable (kg) Sterile wrap (kg) Waste CO2 (kg) Total CO2 (kg)
RA-LSC
LSC
LAP
All types
p
49.6 (± 11.9) 26.68 20.30 2.62 0.00 375.2 (± 92.96) 26 14.3 4.03 2.47 6.90 0.88 14.3 40.3
33.95 (± 7.7) 29.08 – 4.77 0.1 409.06 (± 90.6) 18 11.2 1.60 3.35 6.03 0.99 11.2 29.2
27.41 (± 7.3) 26.19 – 1.12 0.1 243.9 (± 65.07) 14.4 8.3 1.60 0.82 5.86 0.44 8.3 22.7
36.98 27.31 – 2.83 0.06 242.72 19.46 11.26 2.41 2.21 6.26 0.77 11.26 30.72
< 0.01
Copyright © 2015 John Wiley & Sons, Ltd.
< 0.01 < 0.01
< 0.01
Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
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Figure 2. Contribution to operating room waste production by source
Infection control RA-LSC generated 4.035 kg CO2e/patient of infection control waste, 66% more than either LSC or LAP. Infection control-related waste accounted for 19.2% of LAP total solid waste, 14.2% of LSC and 28.2% of RA-LSC (Figure 2).
Discussion We identified an increased environmental impact of robotically-assisted laparoscopy and traditional laparoscopy over laparotomy for endometrial cancer staging. Our findings identify choice of surgical modality – a clinical decision – as another input in the determination of the carbon footprint of healthcare delivery. Surgeons should continue to make decisions based on what is in the best interest of the patient and available evidence. Our work simply highlights the need to further inform those decisions with environmental data. One focus of previously published sustainability research has been on individual components of the healthcare delivery process (e.g. anaesthesia gas release, patient travel, electronic medical records utilization). These studies are useful in their ability to quantify the carbon footprint of a single clinical outcome, but lack comparative data on different methods of accomplishing that outcome. Morris et al. (6), for example, calculated the carbon footprint associated with cataract surgery, including GHG release resulting from travel, procurement of materials and building energy; the assumption that each completion of a clinical process (in that case, cataract surgery) uses the same amount of energy, time Copyright © 2015 John Wiley & Sons, Ltd.
and resources, was inferred. Our study is novel in its determination that the carbon footprint of a clinical process (here endometrial cancer staging) can differ significantly based on surgical modality. Surgical modality is both an individual surgeon’s clinical decision and a determinant of the carbon footprint of a healthcare process. Our study is the first to establish that association. The scope of other healthcare carbon footprinting studies has been an all-encompassing audit of healthcare delivery that, again, assumes the environmental effect of individual clinical processes to be equivalent (6,8–10,29). This subset of research consistently finds the aggregate contribution of clinical processes to be one factor in assessments that also include non-clinical processes (e.g. transportation, information technology). While useful in the carbon footprinting of healthcare delivery on a systems level, these studies provide no useful data on patient-level variances. Those patient-level variances are attributable to a myriad of clinical factors, including unit assignment, length of stay, co-morbidities, ancillary services utilized, imaging and frequency of follow-up. The direct role of physicians’ clinical decision making in determining these factors underscores the importance of our findings. The choices of the care team have both direct and indirect effects on the carbon footprint of a clinical process, and our research is the first to provide comparative data that may be used to inform decision making about one of those choices, namely surgical modality. A limitation of our analysis may be the exclusion of data regarding the carbon footprint of postoperative hospital stays, despite an established reduction in length of stay associated with minimally invasive surgery (30). Accounting for differences in length of stay between Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
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Carbon footprint comparison of laparoscopic procedures
surgical modalities requires a comprehensive assessment of the variations in energy consumption and waste production between intensive care, medical–surgical and postanaesthesia care unit beds. Future research to determine those differences must account for every ventilator, monitor, disposable supply item and staffing difference between those unit beds. We acknowledge the importance of a thorough length-of-stay carbon audit; this was beyond the intention and scope of the current analysis. The decision to focus on a single clinical process, surgery, in great depth is both a strength and a shortcoming of this analysis. We quantify the energy consumed and waste produced by the operative suite and equipment within while excluding the environmental impacts of their transport, manufacture and storage. Operating room equipment and supplies are composed of plastic, rubber, metal and, in some cases, precious metals or exotic composite materials. Every item in the operating room, including the surgeon, is transported there largely by fossil fuel-consuming vehicles. The environmental effect of that transport and procurement has been thoroughly addressed in previous research (6,8–10,29). Our analysis also excludes the GHG emissions arising from the manufacture of capital goods used in the life cycle of the clinical process, as outlined in the BSI PAS 2050 guidelines. Our study is limited in that it was conducted at a single facility and combined data from surgeons with varying levels of robotically-assisted laparoscopy experience. Our findings suggest that, while technological advancements in healthcare abound, the unlimited increases in expenditure of capital and natural resources for only marginal improvements in efficiency or effectiveness is not a sustainable model. The use of electronic health records (EHRs) have been shown to reduce both the environmental impact of healthcare delivery and, when computerized physician order entry (CPOE) is included, mortality (31,32). Similarly, Oliviera et al. (11) found that the use of an emerging video consultation technology, teleconsultation (or telehealth), decreased the environmental impact of care delivery. Research-proven clinical utility (i.e. decreased mortality) and environmental sustainability support the adoption and continued use of those technologies where appropriate. Minimally invasive surgical modalities, such as robotically-assisted laparoscopy, should be subjected to a similar scrutiny before their resource premiums can be justified. To that end, prior research has identified a cost premium of roboticallyassisted laparoscopy over laparoscopy and laparotomy (33,34). Our study highlights energy and waste disposal premiums associated with minimally invasive surgery that cannot be ignored at a time when healthcare costs account for 17.9% of GDP, hospitals contribute 6600 tons of landfill waste/day and energy demands are projected Copyright © 2015 John Wiley & Sons, Ltd.
to increase 28% by 2040 (20,28,35,36). A 30% reduction in the energy efficiency of hospitals would save $1 billion in healthcare costs and reduce carbon dioxide emissions by 11 million tons – equivalent to taking 2 million cars off America’s roads (37). For these reasons, we posit that future healthcare sustainability research include development of strategies to mitigate the environmental effects of healthcare while improving safety, quality and costeffectiveness. Clinicians and administrators empowered by objective data can begin to advocate for changes within the healthcare delivery system and its associated manufacturing industry.
Acknowledgements We wish to thank Tammy L. Loucks, MPH, DrPH, Michelle Glasgow, MD, and the Albert Einstein College of Medicine Weiler Division surgical services staff.
Author contributions D.W. designed the study and data collection tools, collected data for the study, wrote the statistical analysis plan, cleaned and analysed the data, and drafted and revised the paper, and he is the guarantor; S.A. collected data, cleaned and analysed data and revised the paper; T.M. wrote the statistical analysis plan, cleaned and analysed the data and revised the paper; N.N., J.H. and G.G. wrote the statistical analysis plan and revised the draft paper; and D.K. designed the study, revised the data collection tools, wrote the statistical analysis plan, and revised the draft paper.
Conflict of interest The authors declare no potential conflicts of interest.
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412 5. US Environmental Protection Agency. Inventory of US greenhouse gas emissions and sinks, 1990–2007 (April 2009, EPA 430-R-09–004): http://epa.gov/climatechange/emissions/ downloads09/InventoryUSGhG1990–2007.pdf (accessed 18 May 2009). 6. Morris DS, Wright T, Somner JEA, et al. The carbon footprint of cataract surgery. Eye 2013; 27(9): 495–501. 7. Pollard AS, Taylor TJ, Fleming LE, et al. Mainstreaming carbon management in healthcare systems: a bottom-up modeling approach. Environ Sci Technol 2013; 47: 678–686. 8. Blanchard IE, Brown LH. Carbon footprinting of North American emergency medical services systems. Prehosp Emerg Care 2011; 15: 23–29. 9. Subaiya S, Hogg E, Roberts I. Reducing the environmental impact of trials: a comparison of the carbon footprint of the CRASH-1 and CRASH-2 clinical trials. Trials 2011; 12(31): 1–5. 10. Lim AE, Perkins A, Agar JW. The carbon footprint of an Australian satellite haemodialysis unit. Aust Health Rev 2013; 37(3): 369–374. 11. Oliviera TC, Barlow J, Goncalves L, et al. Teleconsultations reduce greenhouse gas emissions. J Health Serv Res Policy 2013; 18(4): 209–214. 12. Power NE, Silberstein JL, Ghoneim TP, et al. Environmental impact of minimally invasive surgery in the United States: an estimate of the carbon dioxide footprint. J Endourol 2012; 26: 1639–1644. 13. Esaki R, Macario A. Wastage of supplies and drugs in the operating room. Medscape Anesthesiol 21 October 2009. Medscape website: http://www.medscape.com/viewarticle/ 710513_2 (accessed 12 November 2012). 14. Kwakye G, Brat GA, Makary MA. Green surgical practices for health care. Arch Surg 2011; 146(2): 131–136. 15. World Health Organization (WHO). Waste from health-care activities. Fact Sheet No. 253 (accessed November 2011). 16. Sutherland L. Green from the get-go. Mater Manag Health Care 2008; 17(8): 14–19. 17. Wong KV, Narashimhan R, Kashyap R, et al. Medical waste characterization. J Environ Health 1994; 57(1): 19–25. 18. DiConsiglio J. Reprocessing SUDs reduces waste, costs. Mater Manag Health Care 2008; 17(9): 40–42. 19. Hu SC, Chen JD, Chuah YK. Energy costs and consumption in a large acute hospital. Int J Architect Sci 2004; 5(1): 11–19. 20. Schule R. Look for fresh ways to ’green up’ the SPD. Mater Manag Healthcare 2008; 17(9): 46. 21. Medical waste incinerator waste management plan. Malcolm Grow Medical Center, Building 1056, Andrews Air Force Base, MD, USA, June 2001. US Air Force Institute for Environment, Safety and Occupational Health Risk Analysis website: http:// airforcemedicine.afms.mil/idc/groups/public/documents/afms/ ctb_033957.pdf (accessed 29 November 2011).
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D. L. Woods et al. 22. Gaskill M. Going green: RNs tackle hospital waste, 24 April 2006. NurseWeek website: http://www2.nurseweek.com/ Articles/article.cfm?AID=20660 (accessed 20 March 2012). 23. Hutchins DCJ, White SM. Coming round to recycling. Br Med J 2009; 338: b609. 24. Lee BK, Ellenbecker MJ, Moure-Eraso R. Analyses of the recycling potential of medical plastic wastes. Waste Manag 2002; 22: 461–470. 25. DeFrances CJ, Cullen KA, Kozak LJ. National Hospital Discharge Survey: 2005 annual summary with detailed diagnosis and procedure data, National Center for Health Statistics. Vital Health Stat 2007; 13(165). 26. Carbon footprint evaluation of municipal solid waste disposal options. Report for Charleston County, SC, USA. GEL Engineering, LLC, December 2008. Charleston County website: http:// media.charleston.net/2009/pdf/montenaystudy_030609.pdf (accessed 20 February 2012). 27. National Energy Foundation. Simple carbon calculator. NEF website: http://www.nef.org.uk/greencompany/co2calculator. htm (accessed 30 January 2013). 28. US Energy Information Administration. Annual energy outlook 2013: http://www.eia.gov/forecasts/aeo/MT_electric.cfm (accessed 12 May 2013). 29. Andrews E, Peasron D, Kelly C, et al. Carbon footprint of patient journeys through primary care: a mixed methods approach. Br J Gen Pract 2013; 63(614): e595–603. 30. Yu HY, Hevelone ND, Lipsitz SR, et al. Use, Costs and comparative effectiveness of robotic-assisted, laparoscopic and open urological surgery. J Urol 2012; 187(4): 1392–1399. 31. Turley M, Porter C, Garrido T, et al. Use of electronic health records can improve the health care industry’s environmental footprint. Health Aff 2010; 30(5): 938–946. 32. Longhurst CA, Parast L, Sandborg CI, et al. Decrease in hospitalwide mortality rate after implementation of a commercially sold computerized physician order entry system. Pediatrics 2010; 126(1): 14–21. 33. Bolenz C, Gupta A, Hotze T, et al. Cost comparison of robotic, laparoscopic and open radical prostatectomy for prostate cancer. Eur Urol 2010; 57(3): 453–458. 34. Wright JD, Burke WM, Wilde ET, et al. Comparative effectiveness of robotic versus laparoscopic hysterectomy for endometrial cancer. J Clin Oncol 2012; 30(8): 783–791. 35. World Bank. World Health Organization National Health Account database. World development indicators. Health expenditure, total (% of GDP): http://data.worldbank.org/ indicator/SH.XPD.TOTL.ZS (accessed November 2013). 36. DiConsiglio J. Reprocessing SUDs reduces waste, costs. Mater Manag Health Care 2008; 17(9): 40–42. 37. Cotton RT, Cohen AP. Eco-conservation and healthcare ethics: a call to action. Laryngoscope 2010; 120: 4–8.
Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
ARTICLE
Carbon footprint of robotically-assisted laparoscopy, laparoscopy and laparotomy: a comparison Demetrius L. Woods1* Thomas McAndrew2 Nicole Nevadunsky2 June Y. Hou2 Gary Goldberg2 Dennis Yi-Shin Kuo2 Sara Isani3 1
Emory University School of Medicine, Department of Obstetrics and Gynecology, Emory Midtown Hospital, Atlanta, GA 30308, USA
2
Albert Einstein College of Medicine, Division of Gynecologic Oncology, Montefiore Medical Center, Department of Obstetrics and Gynecology and Women’s Health, Bronx, NY, USA
3
Robert Wood Johnson Medical School, Division of Gynecologic Oncology, Department of Obstetrics, Gynecology and Reproductive Science, New Brunswick, NJ, USA *Correspondence to: D. L. Woods, Emory University School of Medicine, Department of Obstetrics and Gynecology, Emory Midtown Hospital, 550 Peachtree St NE, 8th Floor, Medical Office Tower, Atlanta, GA 30308, USA. E-mail: [email protected]
Accepted: 18 December 2014
Copyright © 2015 John Wiley & Sons, Ltd.
Abstract Background To date there have been no comprehensive, comparative assessments of the environmental impact of surgical modalities. Our study seeks to quantify and compare the total greenhouse gas emissions, or ’carbon footprint’, attributable to three surgical modalities. Methods A review of 150 staging procedures, employing laparotomy (LAP), conventional laparoscopy (LSC) or robotically-assisted laparoscopy (RA-LSC), was performed. The solid waste generated (kg) and energy consumed (kWh) during each case were quantified and converted into their equivalent mass of carbon dioxide (kg CO2e) release into the environment. The carbon footprint is the sum of the waste production and energy consumption during each surgery (kg CO2e). Results The total carbon footprint of a RA-LSC procedure is 40.3 kg CO2e/ patient (p < 0.01). This represents a 38% increase over that of LSC (29.2 kg CO2e/patient; p < 0.01) and a 77% increase over LAP (22.7 kg CO2e/patient; p < 0.01). Conclusions Our results provide clinicians, administrators and policymakers with knowledge of the environmental impact of their decisions to facilitate adoption of sustainable practices. Copyright © 2015 John Wiley & Sons, Ltd. Keywords
robotic surgery; gynaecology; sustainability; endometrial cancer
Introduction The ’carbon footprint’ is a quantitative measure of the direct and indirect total greenhouse gas emissions attributable to a process, product, institution or industry (1). The process of carbon footprinting yields a quantifiable output expressed in the equivalent mass (kilograms, kg) of carbon dioxide (CO2) release into the environment [CO2 equivalents (CO2e)]. Assessment methodologies and standards for the carbon footprinting process are maturing in the transportation, construction, manufacturing and technology industries (2–4). The healthcare industry is responsible for 7% of the total US CO2 gas emissions
407
Carbon footprint comparison of laparoscopic procedures
(6103 million metric tons CO2e), yet little quantitative research exists on the environmental impact of its component processes (5). Existing carbon footprinting research in healthcare has focused largely on the transport-associated greenhouse gas (GHG) emissions from supply procurement, waste disposal, patient and healthcare staff travel (6–10). Travel to and from healthcare facilities, excluding any direct healthcare activities that occur within, accounts for as much as 38% of the GHG emissions associated with healthcare services (7,9). Energy consumption and landfill waste production, however, account for the majority of the environmental effect of the healthcare industry (12–19). Of US energy, 9% is consumed by the healthcare industry to support energy-intensive medical equipment, including high-intensity lighting and 24 h operating schedules (14). Operating rooms contribute 20–30% of hospital waste production and, together with labour and delivery units, account for 70% of the 6600 tons of waste produced by US hospitals each day (14,18,20,21). Packaging materials alone account for up to 40% of regulated medical waste from operating rooms (22–24). Collectively, these studies are useful in their ability to quantify the carbon footprint of healthcare delivery but the field lacks comparative data on different methods available to achieve a clinical outcome. The paucity of data regarding the environmental impact of the 48 million surgical procedures performed annually prompted our comparison of the carbon footprint of three specific surgical modalities for endometrial cancer staging: laparotomy, conventional laparoscopy and robotic-assisted laparoscopy (25). Our research intends to quantify the carbon footprint of the procedures based on their energy consumed and waste produced. We hypothesized that a significant difference in the carbon footprint exists between the three surgical modalities.
Methods
Administration and previous carbon footprinting studies, such that disposal of 1 kg waste in a municipal landfill is considered equivalent to 1 kg CO2 greenhouse gas (CO2e) release into the environment (26–28). Energy consumption in kWh was converted to CO2e using the National Energy Foundation (NEF) calculator conversion factor of 0.54 kg CO2e/kWh (27).
Patient selection A retrospective review of the 50 consecutive and most recent patients to have undergone a staging procedure for endometrial cancer was conducted for three surgical modalities: robotically-assisted laparoscopy (RA-LSC), conventional laparoscopy (LSC) and laparotomy (LAP). This study received exemption from the Institutional Review Board of the Albert Einstein College of Medicine of Yeshiva University. Clinical data from those 150 staging procedures spanning the years 2008–2011 were then abstracted from patient charts, operating room records and anaesthesia records. Information collected included patient age, body mass index (BMI), procedure type, operative time, history of prior abdominal surgery, length of stay, uterine weight and instruments used. Waste production and energy expenditure were determined and used to calculate the primary outcome measure, total carbon footprint, for each surgical modality, expressed in kg CO2e. Our investigation calculated the carbon footprint as the sum of each procedure’s associated solid waste production (kg) and energy consumption (kilowatt-hours, kWh), using the methodology described in Figure 1.
Waste production Waste is categorized by production source and quantified in the manner described in Figure 1. Waste production was determined based on operating room instrument data specific to each modality, and is assumed to be identical within a modality but differ across modalities.
Carbon audit
Energy consumption
Standards, definitions and assessment methodology for the carbon footprinting process described in our analysis are adapted from the British Standards Institute Publicly Available Specification 2050 (BSI PAS 2050) and the Greenhouse Gas Protocol published by the World Business Council for Sustainable Development and the World Resources Institute (3,4). Data on energy and waste greenhouse gas equivalents were obtained from the National Energy Foundation, the US Energy Information
The energy consumption/unit time (kwh) for every energy-consuming device utilized during the surgery was calculated based on independent source data, as described in Figure 1. All energy consumption was categorized as environmental, equipment, instrument and robotic system, based on function. The operative time (min) was determined from individual operative reports. Operative time was then multiplied by the total energy consumption/unit time of all four categories to
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Figure 1. Methodology for carbon footprint determination
establisha unique energy consumption value for each of the 150 surgeries.
Statistical analysis All tests of continuous variables were compared via Student’s t-test, Kruskal–Wallis test or ANOVA methodology where appropriate. Multiple comparisons were controlled for via Bonferroni’s method. Categorical variables were compared using Pearson’s χ 2 test. BMI and uterine weights differed significantly and their effect on operative time was controlled for, due to possible confounding. Association between length of procedure and co-variables were modelled using ANOVA methodology. All tests were held at α-level of 0.05. Copyright © 2015 John Wiley & Sons, Ltd.
Results The total carbon footprint for all 150 endometrial staging procedures, including solid waste produced and energy consumed, was equivalent to 4498 kg CO2e, averaging 30 kg CO2e/patient (p < 0.01). Age and history of prior abdominal surgery did not differ significantly between groups (p = 0.33; p = 0.72). Uterine weight and body mass index (BMI) differed significantly between groups and were analysed using logistic regression (p < 0.05; p < 0.05). The characteristics of the study population by surgical modality are described in Table 1. We determined that the total carbon footprint of an RALSC for endometrial cancer staging was 40.3 kg CO2e/patient (p < 0.01). This represents a 38% premium over laparoscopy (LSC) at 29.2 kg CO2e/patient and a 77% increase over laparotomy (LAP) at 22.7 kg CO2e/patient (p < 0.01; p < 0.01). Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
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Carbon footprint comparison of laparoscopic procedures Table 1. Characteristics of the study population by surgical modality
Age (years) 2 BMI (kg/m ) Prior abdominal surgery (%) Uterine weight (g)
RA-LSC (n = 50)
LSC (n = 50)
LAP (n = 50)
63.0 36.2 28/50 (56%) 205.1
60.3 31.5 26/50 (52%) 166.31
62.7 35.3 30/50 (60%) 495.47
p* 0.33* < 0.05* 0.72** < 0.05*
*Student’s t-test. 2 **Pearson’s χ test.
of the total energy in those cases, while LAP equipment consumed 4% of the total energy. In the RA-LSC group, equipment (excluding the da Vinci Surgical System) consumed 5.2% of the total energy in each case. The da Vinci surgical system (Intuitive Surgical; Sunnyvale, CA, USA) equipment, however, accounted for 41% of each RA-LSC procedure’s energy carbon expenditure (Figure 2). In each modality, the instrument energy consumption was considered negligible, accounting for < 1% of energy usage in each staging procedure.
Energy
Waste
The three surgical modalities were comparable in the relative contribution of energy consumed to the total carbon footprint, with RA-LSC energy consumption accounting for 61% of each procedure’s total carbon footprint, LSC at 61.5% and LAP at 63.4%. The absolute energy consumption, however, differed between the approaches. RA-LSC equated to 26 kg CO2e/patient compared to LSC, which equalled 18 kg CO2e/patient, and LAP, at 14.4 kg CO2e/patient (ANOVA p < 0.01). The operative times for each procedure were as follows: RA-LSC, 375.2 ± 92.96 min, LSC 409.06 ± 90.6 min and LAP 243.9 ± 65.07 min (p < 0.01) (Table 2). Energy consumption was categorized and quantified as defined in Figure 1. The environmental energy use was comparable among the three types of cases: RA-LSC, 26 kg CO2e/patient; LSC, 18 kg CO2e/patient; and LAP, 14.4 kg CO2e/patient. Environmental energy was also the largest area of consumption: 95% of total LAP energy, 85% of LSC and 53% of RA-LSC energy consumption (Table 2). The LSC group had the highest equipment energy use, at 4.77 kg CO2e/patient. This was followed by RA-LSC, at 2.62 kg CO2e/patient, and LAP, with 1.12 kg CO2e/ patient (Table 2). The LSC equipment consumed 14.05%
The average solid waste production/patient was 11.27 kg CO2e for all surgical modalities combined (Table 2). The LAP group produced the least amount of solid waste, 8.3 kg CO2e/patient, when compared to RA-LSC (14.3 kg CO2e/patient) and LSC (11.24 kg CO2e/patient). The solid waste production of RA-LSC represented a 74% premium over LAP and a 36% increase over LSC. Waste production was assumed to be the same among all 50 surgeries within a modality but to differ across surgical modalities (Figure 2). For that reason, our analysis reports no standard deviation (SD) for this variable. Consumable waste Consumable waste was similar in all three modalities: RA-LSC, 6.90 kg CO2e/patient; LSC, 6.03 kg CO2e/patient; and LAP, 5.86 kg CO2e/patient (Table 2). Consumable waste was the largest contributor to solid waste: RA-LSC, 48.3%; LSC, 53.6%; LAP, 70.8%. Single-use device LSC generated the largest amount of single-use device waste, at 3.35 kg CO2e/patient; RA-LSC produced 2.47 kg CO2e/patient with LAP at 0.82 kg CO2e/patient. RA-LSC single-use device waste accounted for 16.7% of total waste, LSC 29.7% and LAP 9.7%.
Table 2. Total kg CO2e equivalents produced by surgical modality
Energy kWh (SD) Environmental (kWh) da Vinci (kWh) Equipment (kWh) Instrument (kWh) Operative time (min) (SD) Energy CO2 (kg) Waste (kg) Infection control (kg) Single-use device (kg) Consumable (kg) Sterile wrap (kg) Waste CO2 (kg) Total CO2 (kg)
RA-LSC
LSC
LAP
All types
p
49.6 (± 11.9) 26.68 20.30 2.62 0.00 375.2 (± 92.96) 26 14.3 4.03 2.47 6.90 0.88 14.3 40.3
33.95 (± 7.7) 29.08 – 4.77 0.1 409.06 (± 90.6) 18 11.2 1.60 3.35 6.03 0.99 11.2 29.2
27.41 (± 7.3) 26.19 – 1.12 0.1 243.9 (± 65.07) 14.4 8.3 1.60 0.82 5.86 0.44 8.3 22.7
36.98 27.31 – 2.83 0.06 242.72 19.46 11.26 2.41 2.21 6.26 0.77 11.26 30.72
< 0.01
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< 0.01 < 0.01
< 0.01
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Figure 2. Contribution to operating room waste production by source
Infection control RA-LSC generated 4.035 kg CO2e/patient of infection control waste, 66% more than either LSC or LAP. Infection control-related waste accounted for 19.2% of LAP total solid waste, 14.2% of LSC and 28.2% of RA-LSC (Figure 2).
Discussion We identified an increased environmental impact of robotically-assisted laparoscopy and traditional laparoscopy over laparotomy for endometrial cancer staging. Our findings identify choice of surgical modality – a clinical decision – as another input in the determination of the carbon footprint of healthcare delivery. Surgeons should continue to make decisions based on what is in the best interest of the patient and available evidence. Our work simply highlights the need to further inform those decisions with environmental data. One focus of previously published sustainability research has been on individual components of the healthcare delivery process (e.g. anaesthesia gas release, patient travel, electronic medical records utilization). These studies are useful in their ability to quantify the carbon footprint of a single clinical outcome, but lack comparative data on different methods of accomplishing that outcome. Morris et al. (6), for example, calculated the carbon footprint associated with cataract surgery, including GHG release resulting from travel, procurement of materials and building energy; the assumption that each completion of a clinical process (in that case, cataract surgery) uses the same amount of energy, time Copyright © 2015 John Wiley & Sons, Ltd.
and resources, was inferred. Our study is novel in its determination that the carbon footprint of a clinical process (here endometrial cancer staging) can differ significantly based on surgical modality. Surgical modality is both an individual surgeon’s clinical decision and a determinant of the carbon footprint of a healthcare process. Our study is the first to establish that association. The scope of other healthcare carbon footprinting studies has been an all-encompassing audit of healthcare delivery that, again, assumes the environmental effect of individual clinical processes to be equivalent (6,8–10,29). This subset of research consistently finds the aggregate contribution of clinical processes to be one factor in assessments that also include non-clinical processes (e.g. transportation, information technology). While useful in the carbon footprinting of healthcare delivery on a systems level, these studies provide no useful data on patient-level variances. Those patient-level variances are attributable to a myriad of clinical factors, including unit assignment, length of stay, co-morbidities, ancillary services utilized, imaging and frequency of follow-up. The direct role of physicians’ clinical decision making in determining these factors underscores the importance of our findings. The choices of the care team have both direct and indirect effects on the carbon footprint of a clinical process, and our research is the first to provide comparative data that may be used to inform decision making about one of those choices, namely surgical modality. A limitation of our analysis may be the exclusion of data regarding the carbon footprint of postoperative hospital stays, despite an established reduction in length of stay associated with minimally invasive surgery (30). Accounting for differences in length of stay between Int J Med Robotics Comput Assist Surg 2015; 11: 406–412. DOI: 10.1002/rcs
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Carbon footprint comparison of laparoscopic procedures
surgical modalities requires a comprehensive assessment of the variations in energy consumption and waste production between intensive care, medical–surgical and postanaesthesia care unit beds. Future research to determine those differences must account for every ventilator, monitor, disposable supply item and staffing difference between those unit beds. We acknowledge the importance of a thorough length-of-stay carbon audit; this was beyond the intention and scope of the current analysis. The decision to focus on a single clinical process, surgery, in great depth is both a strength and a shortcoming of this analysis. We quantify the energy consumed and waste produced by the operative suite and equipment within while excluding the environmental impacts of their transport, manufacture and storage. Operating room equipment and supplies are composed of plastic, rubber, metal and, in some cases, precious metals or exotic composite materials. Every item in the operating room, including the surgeon, is transported there largely by fossil fuel-consuming vehicles. The environmental effect of that transport and procurement has been thoroughly addressed in previous research (6,8–10,29). Our analysis also excludes the GHG emissions arising from the manufacture of capital goods used in the life cycle of the clinical process, as outlined in the BSI PAS 2050 guidelines. Our study is limited in that it was conducted at a single facility and combined data from surgeons with varying levels of robotically-assisted laparoscopy experience. Our findings suggest that, while technological advancements in healthcare abound, the unlimited increases in expenditure of capital and natural resources for only marginal improvements in efficiency or effectiveness is not a sustainable model. The use of electronic health records (EHRs) have been shown to reduce both the environmental impact of healthcare delivery and, when computerized physician order entry (CPOE) is included, mortality (31,32). Similarly, Oliviera et al. (11) found that the use of an emerging video consultation technology, teleconsultation (or telehealth), decreased the environmental impact of care delivery. Research-proven clinical utility (i.e. decreased mortality) and environmental sustainability support the adoption and continued use of those technologies where appropriate. Minimally invasive surgical modalities, such as robotically-assisted laparoscopy, should be subjected to a similar scrutiny before their resource premiums can be justified. To that end, prior research has identified a cost premium of roboticallyassisted laparoscopy over laparoscopy and laparotomy (33,34). Our study highlights energy and waste disposal premiums associated with minimally invasive surgery that cannot be ignored at a time when healthcare costs account for 17.9% of GDP, hospitals contribute 6600 tons of landfill waste/day and energy demands are projected Copyright © 2015 John Wiley & Sons, Ltd.
to increase 28% by 2040 (20,28,35,36). A 30% reduction in the energy efficiency of hospitals would save $1 billion in healthcare costs and reduce carbon dioxide emissions by 11 million tons – equivalent to taking 2 million cars off America’s roads (37). For these reasons, we posit that future healthcare sustainability research include development of strategies to mitigate the environmental effects of healthcare while improving safety, quality and costeffectiveness. Clinicians and administrators empowered by objective data can begin to advocate for changes within the healthcare delivery system and its associated manufacturing industry.
Acknowledgements We wish to thank Tammy L. Loucks, MPH, DrPH, Michelle Glasgow, MD, and the Albert Einstein College of Medicine Weiler Division surgical services staff.
Author contributions D.W. designed the study and data collection tools, collected data for the study, wrote the statistical analysis plan, cleaned and analysed the data, and drafted and revised the paper, and he is the guarantor; S.A. collected data, cleaned and analysed data and revised the paper; T.M. wrote the statistical analysis plan, cleaned and analysed the data and revised the paper; N.N., J.H. and G.G. wrote the statistical analysis plan and revised the draft paper; and D.K. designed the study, revised the data collection tools, wrote the statistical analysis plan, and revised the draft paper.
Conflict of interest The authors declare no potential conflicts of interest.
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