Environmental impact and life cycle financial cost of hybrid (reusable/single-use) instruments versus single-use equivalents in laparoscopic cholecystectomy

We included in our analysis three types of instrument routinely used in laparoscopic cholecystectomy (Table 1): laparoscopic clip appliers, laparoscopic scissors, and ports (small diameter 5 mm ports, and large diameter 10–11 mm ports). These instruments have both disposable and hybrid versions available on the market. The ‘functional unit’ (unit of analysis) was defined as the number of these three types of instruments typically required to perform one laparoscopic cholecystectomy: two small diameter ports, two large diameter ports, one laparoscopic scissor, and one laparoscopic clip applier.

Hybrid instruments were supplied by Surgical Innovations Ltd. (Leeds, UK) and Microline Surgical Inc. (Beverly, USA). Equivalent single-use instruments were identified from the catalogue of the UK National Health Service (NHS) Supply Chain. We determined raw material composition of each instrument and associated primary packaging using information provided by manufacturers through personal correspondence, or expert knowledge where manufacturers were unable to provide sufficient detail. Weight of component materials was determined using Fisherbrand FPRS4202 Precision balance scales (Fisher Scientific, Loughborough, UK).

An LCA was modelled using SimaPro v9.10 (PRé Sustainability, Amersfort, Netherlands), drawing upon ISO 14044 Guidelines [16]. We performed a ‘cradle to grave’ analysis, including raw material extraction, manufacture, transport, and disposal, plus decontamination for reusable components of hybrid instruments (system boundary outlined in Supplementary Fig. 1). Other reusable instruments and consumables used to perform a laparoscopic cholecystectomy were beyond the scope of this analysis.

Material-specific global average environmental impact of raw material extraction, production, and transportation to the ‘end user’ (in this case the manufacturer) of instruments and packaging was determined through matching materials identified with the closest processes within Ecoinvent v3.6, or where unavailable in Industry data v.2.0 (both databases integrated within SimaPro).

Environmental impact of instrument manufacture was approximated using global average metal working processes for all metal components of instruments and injection moulding processes for plastic components of instruments (as modelled in Ecoinvent v3.6). The mode and distance of international transportation from site of manufacture to the UK was determined through discussion with instrument suppliers (Supplementary Table 1), and we also assumed 80 km of travel by road using a heavy goods vehicle both within country of origin and in the UK, with the first and last 8 km at either end of this journey by courier.

All reusable components were assumed to be decontaminated and re-used 500 times, in accordance with manufacturer guidance on typical usage, with energy and material inputs for decontamination modelled using our own data presented elsewhere [17]. The metrics of the washer/disinfector and sterilisation cycle will vary according to a number of factors, including the loading of machines, electricity source, and constitution of instrument sets. We assumed that reusable components of hybrid instruments were integrated into a general laparoscopic set, as is common practice (Supplementary Table 2a). The typical weight of instruments on a general laparoscopic set was 730 g (data from our local hospital) and the weight of hybrid reusable components was 594 g. Thus, hybrid instruments within a set comprise 45% of total weight (594/1324 g), and so we also apportioned 45% of environmental harm from decontamination of the set to the reusable components of hybrid instruments. At the end of their life, all items were assumed to be disposed of as clinical waste via high-temperature incineration.

Processes selected from SimaPro databases are detailed in Supplementary Table 3.

Following development of the LCA inventory within SimaPro (which identifies flow of energy, materials, and water to and from nature resulting from relevant processes), we used the ReCiPe v1.1 Midpoint Hierarchist method (integrated within SimaPro) to characterise such emissions and to combine these into environmental impacts. This method evaluates eighteen midpoint impact categories (each relating to a single environmental problem): global warming, stratospheric ozone depletion, ionising radiation, ozone formation (on human health, and terrestrial ecosystems), fine particulate matter formation, terrestrial acidification, eutrophication (freshwater and marine), ecotoxicity (terrestrial, freshwater, and marine), human toxicity (carcinogenic and non-carcinogenic), land use, resource scarcity (mineral and fossil), and water consumption. We performed deeper analysis of global warming impact and conducted hotspot analysis to determine processes contributing most to carbon footprints. We used the ReCiPe v1.1 Endpoint Hierarchist method to aggregate midpoint impact categories to calculate endpoint factors for damage to human health, the natural environment, and resource scarcity. Finally, we used ReCiPe v1.1 Hierarchist normalisation factors to compare total midpoint and endpoint impacts to mean average contributions to each of those impacts from a global average person’s daily routine activities [18].

To determine sensitivity of results to allocation methods and key assumptions, we modelled five alternative scenarios:

First, we determined the impact of altering the number of uses of instruments and through this also identified the threshold at which the carbon footprint of reusables became lower than using single-use equivalents.

Laparoscopic clip appliers are not used across all laparoscopic operations performed in a given surgical department (but laparoscopic scissors and ports typically are), and clip appliers are therefore not always integrated into general laparoscopic sets. In our second scenario, we modelled decontamination with the clip applier decontaminated separately in a flexible double-wrapped polyethylene pouch (Supplementary Table 2b). Here, we assumed that total weight of items in the laparoscopic general set was 1.1 kg, with decontamination of surgical scissors and ports apportioned accordingly (366/1096 g = 33%).

Third, we modelled the impact of switching the electricity source for decontamination to that typical of Australia, a country using a lower proportion of renewable energy.

Fourth, we modelled impact of changing overseas transport of single-use instruments to shipping by sea, with distances determined using the online Pier2Pier tool [19] and alternative road distances using Google maps [20] (Supplementary Table 1).

Finally, we modelled the carbon footprint of using three 5 mm ports and one 10/11 mm port, as this is a commonly used alternative port configuration for laparoscopic cholecystectomy. In the baseline scenario, we modelled 5 mm single-use ports based upon a dual pack (containing two cannulas, one syringe, and one trocar), and for this alternative scenario, a single-pack was modelled based on removal of duplicate components (Table 1).

Our baseline analysis uses standard practice of an attributional approach to LCA [21], where products are allocated a proportion of the total lifecycle material and energies required for processes shared with other products. We performed alternative analysis of our base scenario using the consequential approach to LCA, which examines consequences of a change [21]. Specifically, when switching from single-use to hybrid laparoscopic instruments, hybrid components are integrated into surgical sets already destined for decontamination, meaning under the consequentialist model, there is no additional impact from decontamination.

The cost of instruments reported in the NHS Supply Chain database [22] was equated to cost of manufacture and distribution. Disposal at the end of instrument life was costed at £617.22 per tonne, based on the price of clinical waste incineration reported by the NHS Digital Estates Returns Information Collection dataset [23]. Cost of decontaminating reusable components of hybrid instruments was based on the charge made by our hospital sterilisation services per instrument set, apportioned according to the weight of hybrid reusable components (here 45%).

This work was funded by Surgical Innovations Ltd. who manufacture hybrid laparoscopic instruments, but the company played no part in scientific conduct, analysis, or writing of this manuscript. This study did not require ethical approval or consent as there were no patients or participants involved in this research.

Table 1 details material composition and life-span assumptions for the laparoscopic instruments. The carbon footprint per operation of a laparoscopic hybrid instrument compared to its single-use equivalent was 17% for a clip applier (445 g vs 2559 g CO₂e), 33% for scissors (378 g vs 1139 g CO₂e), and 27% for four ports (933 g CO₂e vs 3495 g CO₂e/ operation) (Fig. 1). When combined, the carbon footprint of using hybrid versions of all three instrument types for an operation was 24% of that of single-use equivalents (1756 g CO₂e vs 7194 g CO₂e), saving a total of 5.4 kg CO₂e. This equates to the normal activities of a global average person over 6 h (normalised results).

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Hotspot analysis indicated that the majority of the carbon footprint of hybrid instruments was due to the single-use components (mean 62%, range 43–79%), followed by decontamination of reusable components (mean: 37%, range 21–56%) (Supplementary Table 4). For single-use instruments, raw material extraction and manufacture (including transportation between these two processes) was a major contributor (mean 57%, range 52–61%), followed by onward transportation (mean 29%, range 24–36%) and waste (mean 14%, range 12–16%).

The environmental impact of using a combination of hybrid laparoscopic clip appliers, scissors, and ports for an operation was lower than using single-use equivalents across all 18 midpoint environmental impacts except for marine eutrophication (Supplementary Fig. 2), with mean average reductions in environmental impact of 60% (range − 32% to 84%). Disaggregated data for each instrument showed midpoint environmental impact categories to be lower for each hybrid product, with a small number of exceptions (Table 2). Contribution analysis (Supplementary Figs. 3 and 4) indicated that the 3% higher freshwater ecotoxicity and 7% higher marine ecotoxicity impacts for hybrid compared to single-use laparoscopic scissors were principally due to aluminium within the single-use component of the hybrid scissors (38% for freshwater ecotoxicity, and 37% for marine ecotoxicity) and due to copper assumed to be used within the metal working process (contributing 50% to both categories). Higher marine eutrophication impacts for the hybrid laparoscopic clip applier (38% higher) and ports (76% higher) were largely attributable (89% and 85%, respectively) to the handling of wastewater from decontamination (Supplementary Fig. 5 and 6). The ionising radiation impact of hybrid laparoscopic scissors and ports (Supplementary Fig. 7 and 8) was higher than single-use equivalents (14% and 32%, respectively) due to the electricity used in the decontamination process (accounting for 55% and 78% of the impact, respectively).

For endpoint categories, using a combination of hybrid laparoscopic clip appliers, scissors, and ports for a single laparoscopic cholecystectomy saved an estimated 1.13 e⁻⁵ DALYs (disability adjusted life years), 2.37 e⁻⁸ species.year (loss of local species per year), and US $ 0.6 impact on resource depletion, representing reductions of 74%, 76%, and 78%, respectively, compared to single-use equivalents (Table 3, Supplementary Fig. 9).

For all hybrid instruments, carbon footprint was lower than single-use equivalents when the reusable component was used more than twice. Impact on carbon plateaued at around 10 uses of reusable components, with little additional gain (< 1%) after using laparoscopic scissors 60 times, ports 70 times, and clip appliers 100 times (Supplementary Fig. 10). However, continued use of these saves the additional carbon burden of obtaining new instruments.

When packaged and decontaminated separately, the carbon footprint of the hybrid laparoscopic clip applier increased 3.7-fold to 1650 g CO₂e per use (Supplementary Table 5). There were small accompanying increases for laparoscopic scissors (to 394 g CO₂e per use, 4% increase) and ports (999 g CO₂e per use, 7% increase), due to a greater proportional weight in the instrument set. Nevertheless, in this alternative model, the carbon footprint of all hybrid instruments remained lower than single-use equivalents (36% less for laparoscopic clip appliers, 65% less for laparoscopic scissors, and 71% less for ports).

The carbon footprint of the decontamination process itself was 54% higher when Australian electricity was modelled, which increased carbon footprint of the hybrid instruments by 11–30% (Supplementary Table 6), but this remained lower (63–77%) than single-use equivalents.

Shipping in place of air-freight for international transport of single-use instruments reduced carbon footprint by 22–33% relative to the baseline single-use items (Supplementary Table 7), but the hybrid baseline instruments remained lower than the shipped single-use equivalents: by 74% for the clip applier, 55% for scissors, and 65% for ports.

Finally, using three hybrid 5 mm ports and one 10 mm port (635 g CO₂e/ operation) resulted in a 32% reduction in carbon footprint relative to the base scenario hybrid port setup (Supplementary Table 8). The use of single-use ports with this alternative port configuration was associated with six-fold increase in carbon footprint compared with use of hybrids (3613 g CO₂e), constituting a 3% increase relative to the base scenario single-use port setup.

Under the consequential approach to LCA, carbon footprint of a hybrid laparoscopic clip applier was 198 g CO₂e (7% of single-use equivalent of 2559 g CO₂e), for scissors this was 299 g CO₂e (26% of single-use equivalent of 1139 g CO₂e), and for four hybrid ports was 614 g CO₂e (18% of single-use equivalent of 3495 g CO₂e). When combined, under the consequentialist approach, the carbon footprint of using hybrid versions of all three instruments types for an operation was 15% of that for single-use equivalents (1110 g vs 7194 g CO₂e), saving a total of 6083 g CO₂e.

Per operation, the cost of hybrid compared to single-use instruments (Table 4) was 33% for a clip applier (GBP £ 52 vs £ 156), 83% for scissors (GBP £ 20 vs £ 24), and 58% for ports (GBP £ 59 vs £ 102). Most of these costs (≥ 87% contribution in all cases) were from single-use items or components, with smaller contributions from decontamination (≤ 10%), reusable components (≤ 4%), or waste (≤ 0.2%). For a single laparoscopic cholecystectomy, cost of using a combination of hybrid laparoscopic clip appliers, scissors, and ports was 47% of that of single-use equivalents (GBP £ 131 vs £ 282).