Download Dr V Naidoo - Anaesthesia and the environment

28 September 2012
No. 32
ANAESTHESIA AND THE ENVIRONMENT
Verushka Naidoo
Commentator: S Jithoo
Moderator: K de Vasconcellos
Department of Anaesthetics
CONTENTS
OBJECTIVES ....................................................................................................... 3
INTRODUCTION ................................................................................................... 4
DRUG WASTAGE IN ANAESTHESIA ................................................................. 5
ANAESTHESIA AND THE ATMOSPHERE .......................................................... 7
THE IMPACT OF GENERAL ANAESTHETICS ON THE ENVIRONMENT .......... 8
Anaesthetics Gases and the Environment ........................................................ 8
Quantifying the Environmental Effect of Anaesthetic Drugs: Life Cycle
Assessment ......................................................................................................... 9
STRATEGIES TO REDUCE OUR ENVIRONMENTAL FOOTPRINT ................. 11
Reducing Environmental Contamination by anaesthetic gases .................... 11
DISPOSABLE AND REUSABLE EQUIPMENT IN ANAESTHESIA ................... 14
CONCLUSION .................................................................................................... 18
REFERENCES.................................................................................................... 19
Page 2 of 19
OBJECTIVES
 To increase awareness on the impact of anaesthesia on the environment
 To suggest appropriate steps to prevent and limit drug wastage in theatre
 To provide an understanding of the impact that volatile agents and nitrous
oxide has on the atmosphere
 To provide an understanding of life cycle assessments
 To discuss the impact that reusable and disposable items have on the
environment
 Promote ways in which we can reduce, reuse and recycle
Page 3 of 19
INTRODUCTION
In our daily practice very little consideration has been given to the effects of
anaesthesia on the environment. The aim of my talk is to increase awareness of
the above mentioned topic and to highlight aspects of anaesthesia that contribute
to environmental pollution and discuss ways in which we can reduce these
impacts. The health care industry contributes to environmental pollution and
global warming [19]. In the United States alone the health care sector contributes
to more than 8% of the total carbon dioxide (CO2) emissions [17].
The negative impact of anaesthesia on the environment is an issue that requires
much attention since environmental resources are limited. As population size and
modern medicine continues to expand so does the number of anaesthetics we
administer. From recent studies it has been shown that hospitals contribute
significantly to CO2 emissions [15]. These findings are worrisome and as
anaesthesiologists it is our responsibility to be aware of the potential harm that we
present to the environment through our daily practices. It is through awareness
that we can promote environmentally friendly policies and programs to reduce the
negative impact of anaesthesia on climate change [15].
To address the environmental impact of anaesthesia this talk is going to focus on
drug wastage in anaesthesia, the environmental effects of the anaesthetics agents
themselves, and the environmental effect of the waste generated by the
equipment necessary to practice anaesthesia.
Page 4 of 19
DRUG WASTAGE IN ANAESTHESIA
One of the factors contributing to environmental contamination is drug wastage.
Drug wastage has significant adverse ecologic effects and the potential to
increase health care costs [1].
In a study conducted by Mankes in New York, drug usage and wastage was
investigated [1].
Fig 1 and Fig 2 below highlight the amount of drug wastage that occurs with common
anaesthetic drugs.
Dispensed (mL)
80000
70000
60000
50000
40000
30000
20000
10000
0
e
in
e
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Bu
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in
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oc
Pr
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of
ain
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e
Dispensed (mL)
Figure 1: Volume of common anaesthetic agents dispensed [1]
Wasted (percentage)
60
50
40
30
20
10
0
e
in
At
ro
p
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ar
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of
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Wasted (percentage)
Figure 2: Percentage of dispensed drug wasted [1]
Page 5 of 19
Propofol was the most used and wasted drug in the facility, making up 45% of the
total drug wastage by millilitre (mL). While propofols impact on the environment
appears low, it does have the ability to accumulate in adipose tissue of aquatic
organisms and under anaerobic conditions is not biodegradable. It is found to be
toxic to aquatic life and may also contribute to adverse long term effects in the
aquatic environment [1]. Since propofol is not biodegradable it has to be
incinerated (>1000 degrees celcius) for no less than two seconds, which in itself is
energy consuming [1]. Propofol is normally incinerated in our facility but it can find
its way into the environment because of inadequate waste disposal by healthcare
professionals.
In the above study it was found that by decreasing the size of propofol vials, drug
wastage was reduced from 29.2mL/day/bin to 2.8mL/day/bin, therefore reiterating
the fact that reduction in waste occurs with feedback of information to healthcare
professionals allowing them to change practice patterns that contribute negatively
to the environment1. A reduction in wastage will in turn decrease hospital
expenditure and the harmful effects of Propofol on the environment.
A study by Chaudhary et al showed that in addition topropofol; rocuronium,
vecuronium and neostigmine contribute significantly to total drug wastage [6]. The
majority of propofol waste was due to the drug being left over in the vial. They
also found that less propofol was wasted when smaller vials where used as in the
study by Mankes et al [1]. In addition discussing the plan of anaesthesia
beforehand prevented unnecessary wastage of drugs [6].
Although controversial from an infection control point of view, drug wastage can
also be reduced by providing accessibility to multi-dose vials for certain drugs. For
example wastage of rocuronium can be limited by loading only the calculated drug
dose based on per kilogram body weight, therefore leaving behind sterile drug in
the multi-dose vial that can be used for other cases.
For drugs such as morphine an effective method to decrease wastage would be to
load the drug in a 10ml syringe and then load into separate syringes for each case
as per body weight. In this way one ampoule of morphine can be used for more
than two cases6. Interventional education in the form of lectures, posters etc is
also an important way to increase awareness and help reduce wastage and in
turn the negative environmental impact it brings.
Page 6 of 19
ANAESTHESIA AND THE ATMOSPHERE
Figure 3: The Atmosphere [2]
The atmosphere consists of five layers: the troposphere, stratosphere,
mesosphere, thermosphere and exosphere. The composition of the atmosphere
gradually changes due to diffusion of gas molecules: it consists of greater
quantities of lighter gases at higher altitudes [2]. The stratosphere (which contains
the ozone layer) and the troposphere are the two most important thermoregulatory
layers of the earth [3, 18]. Life on earth is shielded from harmful ultraviolet radiation
by the stratospheric ozone layer [18]. Shortwave ultraviolet radiation is absorbed
by the ozone in the higher atmospheres [2].
Ozone depleting substances are directed to the stratosphere by air currents in the
tropics. They are then broken down in the stratosphere by ultraviolet radiation and
their by-products form radicals that contribute to ozone destruction. Half the solar
energy is absorbed by the earth’s surface, while the rest is absorbed or reflected
by clouds and atmosphere. Infrared radiation is also emitted from the earth’s
surface [2]. This infrared radiation is absorbed by greenhouse gases in the
troposphere and this energy is directed back to the earth. Studies bring to light
that global warming potential and ozone depletion potential are significant for all
the volatile agents, especially when used with nitrous oxide [3]. They therefore
have the potential to impact negatively on the environment
Page 7 of 19
THE IMPACT OF GENERAL ANAESTHETICS ON THE ENVIRONMENT
Data suggest that in the United States alone fifty million patients have general
anaesthetics administered to them each year [2]. General anaesthetics are not
only administered in the hospital setting but also used extensively by
veterinarians, dentists and in laboratories [1].
Recent studies show that
anaesthetic gases have a significant impact on global warming and depletion of
the ozone layer [2, 8].
In our operating theatres we have scavenging systems that decrease our
exposure to general anaesthetics. These gases however are eliminated directly
into the atmosphere unchanged because they undergo minimal metabolism when
exhaled by patients.
Sevoflurane, isoflurane, halothane, enflurane and
desfluraneare are halogenated compounds and, since they are chemically similar
to chloroflurocarbons, they contribute to depletion of the ozone layer [1,3]. Nitrous
oxide is also an established greenhouse gas that can cause depletion of the
ozone layer.
Anaesthetics Gases and the Environment
The impact that a gas has on the environment is determined by its atmospheric
lifetime, global warming potential and ozone depleting potential.
a) Atmospheric lifetime:
Is the average time in years that a molecule resides in the atmosphere before it is
removed by chemical reaction or deposition [4]. The more resistant a compound is
to breakdown in the environment, the higher the atmospheric lifetime.
Atmospheric lifetimes of more than two years contribute to ozone depletion for
longer periods and tend to cause an imbalance of infrared radiation which, as
discussed earlier, can contribute to global warming.
b) Global Warming Potential:
Is a measure of the total energy absorbed by a gas over a certain time (usually
100 years) in comparison to carbon dioxide [4]. i.e. the heat trapping potential of a
greenhouse gas in the atmosphere [4].
c) Ozone Depletion Potential:
The ozone depletion potential (ODP) is defined as the amount of degradation that
a compound can cause to the ozone layer.
Page 8 of 19
Compound
Chlorofluorocarbons
Carbon dioxide
Nitrous oxide
Halothane
Isoflurane
Sevoflurane
Desflurane
Atmospheric
lifetime (years)
50-100
5-200
114
6.6-7.0
3.2-5.9
1.2-4.0
8.9-21.0
Global warming
potential (GWP)
10900
1
298
510-571
141-218
1525-1746
Ozone Depletion
potential (ODP)
1
0.017
1.56
0.03
0.00
0.00
Table 1: Atmospheric lifetimes, Global warming potential, and Ozone depletion
potential of common anaesthetic gases [3]
All of the volatile agents have atmospheric lifetimes of more than 2 years, with the
exception of sevoflurane. Sevoflurane has a low GWP and atmospheric lifetime.
Desflurane has the largest environmental impact, with the highest atmospheric
lifetime and GWP of all the volatiles. Desflurane’s environmental impact is much
higher than that of CO2. In comparison to the CFCs, halothane is shown to have a
similar ODP. This is due to its bromine atom which is known to damage the
ozone layer. Also of importance is the fact that halothane has a higher ODP than
the CFCs (1.56x more).
Nitrous Oxide and the Environment
Nitrous oxide (N2O) has an atmospheric lifetime of 120 years [2]. Its global
warming potential is about three hundred times that of carbon dioxide but its
ozone depletion potential is lower than that of the chlorofluorocarbons [3]. Nitrous
oxide reacts with oxygen atoms in the atmosphere to produce nitric oxide (NO),
which can, in turn, contribute to ozone depletion. Nitrous oxide has been part of
the atmosphere for millions of year as it is emitted by bacteria on earth.
Agriculture is another source of nitrous oxide production, i.e. from nitrogen
fertilizers, cultivation of soil, and animal waste.
Livestock, burning of fossil fuels and industry also produces a large percentage of
this gas. In 2006 in the USA, N2O use in anaesthesia was estimated to contribute
to 3% of the total N2O emissions [2].According to recent studies nitrous oxide can
contribute to greenhouse gas emissions and when administered with other volatile
agents can increase emissions [2].
Quantifying the Environmental Effect of Anaesthetic Drugs: Life Cycle
Assessment
A tool known as a life cycle assessment is used to evaluate the impact that a
product has on the environment during its life cycle and the resources used in the
process. As medical personnel it is essential in our daily practice to take into
consideration the life cycle of drugs. In doing so we can understand how our drug
choices impact on the environment.
Page 9 of 19
A study by Sherman et al looked at the environmental impact of sevoflurane,
desflurane, isoflurane, nitrous oxide, and propofol by utilizing life cycle
assessments of each drug. They looked at: resource extraction and manufacturing
of the above drugs, transportation to hospitals, clinical use, and disposal or
emission to the environment [8].
Figure 4: Life Cycle Assessment of Anaesthetic Agents [8]
Manufacturing and production of agents
Transport
Use
Disposal
Isoflurane
Production
Extraction Of
raw material
Manufacturing
of industrial
gas
Desflurane
Production
Sevoflurane
Production
Production
of basic
chemicals
Emissions to
Environment
Health Care
Facility
Medical
Waste
Propofol
Production
Emissions to
Environment
Waste
Anaesthetic gases
Emissions to
Environment
Emissions were taken into consideration at each stage of the life cycle. Using
SimaPro Life Cycle Assessment Software they were able to store data and
assessment of impact was performed [8].
From the above study it was found that desflurane contributed more than the other
agents towards life cycle Greenhouse gas emissions [8]. Furthermore the
greenhouse gas emissions increased when administered with N2O/O2 for these
agents. Propofol was found to have a small impact compared to the other agents.
The impact of propofol was found to originate mainly from the energy required to
function the syringe pump and not from the release of propofol to the environment
itself [8]. There are several factors responsible for desflurane’s higher greenhouse
gas emissions compared to the other agents: its rate of metabolism is low
therefore a greater volume of gas is emitted unchanged to the environment, and it
has a higher MAC value and global warming potential (GWP) than the other
agents.
Page 10 of 19
STRATEGIES TO REDUCE OUR ENVIRONMENTAL FOOTPRINT
Reducing Environmental Contamination by anaesthetic gases
a) Closed anaesthesia
Studies have shown that closed circuit anaesthesia can decrease volatile
anaesthetic use by 80% to 90% [2]. Using this technique one is able to limit
environmental contamination. Closed circuit anaesthesia however is found to be
unpopular among many anaesthesiologists due to the perceived difficulty in
gaining reliable control over the concentration of inspired gases administered [9].
Previously, along with this came the added task of injecting anaesthetic liquid
vapours, stringent management of fresh gas flow and estimation of circuit volume
[10]
. Recent developments of more advanced anaesthetic equipment however
have made closed circuit anaesthesia simple and far more feasible for routine
practice [9].
b) Control of Fresh Gas Flow
Control of Fresh Gas Flow (FGF) in a more proficient manner can reduce
environmental contamination intra-operatively. Fresh gas flow can be managed
during all phases of anaesthesia i.e. induction, maintenance and emergence.
Since we are directly responsible for the administration of anaesthetic gases and
FGF, we are in fact directly accountable for the impact it may have on the
environment.
It is essential to understand the influence that FGF has on environmental
contamination. In an article by Feldman et al, GASman simulations were used to
approximate the anaesthetic gases utilized during a general anaesthetic [10].
GASman is a computer simulator used for estimating uptake and distribution of
anaesthetic agents. This simulator is able to allow the user to display the time
course of anaesthesia uptake and distribution in body compartments, the
breathing circuit and the vaporizer.
The user can enter information including patient profiles, FGF, gas delivery, and
breathing circuit type. GASman can then calculate the distribution over time, and
the amount of gas delivered and taken up by the patient. It can therefore estimate
the amount of anaesthetic gases wasted [10, 11].
Page 11 of 19
Vapourizer setting
FGF during Induction
(15mins)
FGFduring Maintenance
(75mins)
Amount Delivered
Amount taken up
Contamination
Anaesthetic 1
2%
Anaesthetic 2
2.5%
8L/min
8L/min
2L/min
1L/min
5.4L
1.3L
4.1L
4.28L
1.26L
3.02L
Table 2: Gasman simulation of a 90 minute general anaesthetic
al
[10].
Modified from Feldman et
Using GASman simulation Feldman was able to demonstrate that by using lower
fresh gas flows, one can decrease the amount of contamination into the
environment.
He then went on further to examine the consequence of
administering these fresh gas flows over a 35 year career (500 anaesthetics per
year over a 35 year period).
It was found that by reducing the FGF from 2L/min to 1L/min during the
maintenance phase, 18,900L of isoflurane was prevented from being wasted into
the atmosphere [10]. We can easily observe that by managing FGF effectively, we
can reduce the amount of contamination into the environment. Reducing FGF
during the maintenance phase is probably the ideal time to do so, but strategies to
reduce contamination during emergence and induction can also be practised.
Page 12 of 19
Figure 5- Recommendations for management of fresh gas flow [10]
c) TIVA/Regional Anaesthesia
Total intravenous or regional anaesthesia can eliminate the need for anaesthetic
gases and therefore decrease the negative impact that they have on the
environment. These techniques however utilize drugs, anaesthetic equipment,
receptacles and energy. The impact that these techniques have on the
environment has not been well investigated. Therefore in order to compare them
with inhalational anaesthesia thorough life cycle assessments will have to be done
[2,3]
.
The potential impact of the reusable/disposable components of intravenous
anaesthesia will also be alluded to below. Strategies to reduce drug wastage also
need to be addressed when employing TIVA as an environmentally friendly
strategy.
Page 13 of 19
d) Silica Zeolite (Deltazite)
Standard anaesthetic gas scavenging systems collect and remove waste gases
and transfer them to the atmosphere. To prevent environmental contamination
new technologies have been developed. Silica Zeolite is a molecular sieve
adsorbent. Trapping of halogenated hydrocarbons from the gas stream is
achieved by passing it through a layer of hydrophobic and organophilic silica
zeolite [12]. The cavities found in the crystal framework of the silica zeolite adsorb
the halogenated hydrocarbons so removing them from the gas stream.
By exposing the exhausted adsorbent to a purging gas stream the trapped agents
can be regenerated [12]. The halogenated agents are extracted from the gas
stream in liquid form and then purified by fractional distillation [12]. In a study by
Doyle et al silica zeolite was effective in removing 1% isoflurane from exhaled
humidified gas containing CO2 for 8 hours [12]. Zeolite filters (Deltasorb) are also
used in scavenging lines to limit the amount of volatile released into the
atmosphere [16]. Studies have shown that each canister can adsorb about two
bottles of halogenated anaesthetics, therefore decreasing the amount released by
40-75% [2, 3].
e) Xenon [2, 3]
Xenon occurs naturally in the atmosphere (0,08 parts per million). It has no toxic
effect on the environment. It can be used in anaesthesia as a substitute to N2O
for its analgesia properties. It also provides some degree of neuroprotection and
haemodynamic stability. It can be used for rapid induction and emergence
because of its low blood gas partition coefficient. It is manufactured through
fractional distillation of liquid air and is very costly.
The high cost therefore limits its use in clinical practice. Also it is not economical
because it consumes large quantities of energy for production (220W/h per 1L
xenon gas). This is more than the energy needed to produce N2O.
f) Other ways to reduce Environmental Contamination
 Selection of gases that have a less negative impact on the environment for
e.g. limiting use of N2O, or choosing to use sevoflurane or isoflurane over
desflurane and halothane [3].
 Developing newer anaesthetic gases with lower environmental impact
 Maintenance and testing of anaesthetic equipment to prevent leaks [5]
DISPOSABLE AND REUSABLE EQUIPMENT IN ANAESTHESIA
There has been a growing interest in the impact that reusable and disposable
equipment and textiles has on the environment. A large proportion of CO 2
emissions are from the health care sector. Reusable equipment requires cleaning
and disinfectants that may be toxic to the environment, whereas disposable items
may add substantially to waste of landfills [15].
Page 14 of 19
In addition disposable items may require incineration that release toxins to the
atmosphere. The environmental impact of manufacturing, disposal and waste
management can be done by conducting life cycle assessments. Using life cycle
assessments one can assess the financial and environmental impacts of such
items therefore aiding decision making when selecting items for use in theatre.
a) Disposable vs Reusable Laryngeal Mask Airways [13]
The first Laryngeal Mask Airways (LMAs) that were used in the late 1980s were
reusable, in the late 1990s disposable LMAsbecame available [13]. Previous
studies conducted have shown no difference between reusable and disposable
LMAs in terms of the way they function and their ability to be user friendly. Due to
an increase in the number of general anaesthetics administered each year and
financial constraints in the health sector, the types of LMAs purchased are
normally dictated by costs.
Eckelman et al conducted a comparative life cycle assessment of disposable and
reusable Laryngeal Mask Airways. A cradle-to-grave study was done which
looked at manufacturing, transportation and usage and wastage of the LMAs. The
impact that the LMAs had on the environment was assessed using SimaPro life
cycle assessment software and the Building for Environmental and Economic
Sustainability impact assessment method [13]
Used LMA +
packaging
Raw
Materials
LMA
Materials
Manufacturing
Reusable LMA
LMA
Materials
Use
Solid Waste
Management
Transport/
Distribution
Disposable LMA
Raw
Materials
Packaging
Used LMA +
Packaging
Transport/
Distribution
Manufacturing
Packaging
Use
Solid Waste
Management
Washing
Autoclave
Wastewater
Treatment
40 Cycles
Figure 6: Comparative Life Cycle Assessment of Disposable and Reusable Laryngeal Mask [13]
The results of the above study have shown that the reusable LMA ClassicTM had
fewer life cycle impacts than that of the disposable LMA UniqueTM. The reusable
LMA contributes 7.4kg CO2e of GHGs over its life cycle, and the equivalent 40
disposable LMAs contribute 11.3kg CO2e, when looking at climate change
Impacts [13].
Page 15 of 19
Figure 7: Comparison of environmental and human health (HH) impacts for disposable and
reusable LMAs, Building for Environmental and Economic Sustainability (BEES) impact
assessment method [13].
There are many factors that may contribute to these environmental impacts.
These include the type of material used in the manufacturing of LMAs.
Disposable LMAs consists of polyvinyl chloride (PVC) plastic whereas reusable
LMAs are made of silicone. PVC has been linked with concerns regarding
health[13] and burning of these plastics has obvious negative impacts on the
environment. Disposable LMAs also require larger quantities of material in total for
packaging. In addition Diethylhexyl phthalate (DEHP) is used in PVC products.
DEHP has been identified as a likely carcinogen and could possibly be implicated
in endocrine disruption [13].
Although the reusable LMAs have less of an impact on the environment than the
disposables there is still some room for improvement. The process of autoclaving
utilises large quantities of energy and water. These environmental impacts can be
reduced by autoclaving more LMAs during a single cycle at once or with similar
equipment [13]. Ordering LMAs in bulk can also reduce environmental impacts, as
there will be less need for transport of LMAs by air which has negative effects on
the atmosphere.
b) Reusable and single-use Central Venous Catheter Insertion Kits [14].
In a study by McGain et al they looked at the impact that Reusable and SingleUse Central Venous Catheter Insertion Kits have on the environment and
financially. The source of energy used for sterilization was examined and the
effect that it has on CO2 emissions. Using SimaPro Software they were able to
perform life cycle assessments on the reusable and single-use central venous
catheter kits. Effects on the environment analysed included CO2 emissions, water
and mineral use, ecotoxicity and solid waste [14].
Page 16 of 19
Sensitivity analyses on the source of electricity was also done on the reusable
kits. These included brown coal, gas cogeneration and the standard electricity
supply.
CVC Kit Type
Reusable kit (brown
coal electricity), total
weight=627g
Single-use CVC kit, total
weight=171g
Total CO2 produced
(grams)
Total Water use (litres)
1211
27.7
407
2.4
Table 3:Comparison of CO2 produced and water used for Reusable and Single-use CVC kits [14]
From the study it was demonstrated that the use of water and energy for the
reusable kits were more than for the single use kits (this was based on the brown
coal electricity). Majority of the CO2 emissions for the reusable kits came from
sterilization (830g) whereas for the single use kits most of the CO2 emissions
where from manufacture of plastics (170g).
It was also demonstrated that the source of energy used in the sterilization
process played an important role in the CO2 emissions produced.
Type of CVC kit
(and energy source)
Single use (European
energy mix)
Reusable: brown coal
Reusable: hospital
cogeneration
Reusable: United States
electricity mix
Reusable: European
electricity mix
CO2 emissions
(grams) with
95% CIs
Water use
(liters) with
95% CIs
407 (379-442)
2.5 (2.1-2.9)
1211 (1099-1323)
27.7 (27.0-28.6)
436 (410-473)
26.0 (25.8-26.2)
764 (509-1174)
46.3 (36.6-62.6)
572 (470-713)
40.5 (36.4-45.8)
Table 4: Modified from McGain F: CO2 Emissions and Water Use for the Single-Use and
Reusable Central Venous Catheter(CVC) Kits Accounting for Different Energy Sources [14].
From the above table it can be seen that by using other sources of electricity
instead of brown coal, CO2 emissions can be reduced. Types of energy sources
with lower CO2 emissions include gas-fired boilers as a source of steam energy
and nuclear powered electricity. In the above study for their hospital that used
brown coal as an energy source and on average 500 CVC insertion kits yearly,
reusable kits would have saved them $1000, however it would have produced
400kg more CO2 and used 12500 more litres of water than compared to the
single-use CVC kits [14].
Page 17 of 19
Therefore when considering reusable kits one would have to examine the source
of energy used for sterilization as it also contributes to increasing CO2 emissions.
CONCLUSION
Climate change has become an important issue for health care industries. The
environmental impact of our actions should not be left unchecked.
As
anaesthesiologist we need to add environmental awareness to our list of
responsibilities. The information provided in this booklet introduces some of the
environmental implications of our clinical practice and offers suggestions on how
to reduce these. As health care professionals we have the opportunity through
education and research to promote environmentally friendly policies and reduce
the negative impact of our actions.
Page 18 of 19
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