observational study: anesthesia agent...

A special report by Suzanne Thomson, MBChB FRCA

The cost of volatile inhalational anesthetic agents is a

topic of increasing interest within the global hospital

community as medical cost containment strategies are

being discussed and developed in recent years in an

era of increasing expenditure and budget constraints for

health care resources. In the process of evaluating new

anesthesia technology (MAQUET FLOW-i) to replace older

systems (Datex-Ohmeda) in our departments’ five operating

theatres and anesthetic induction rooms, we performed a

retrospective 6 month cost comparison of volatile agent

usage of the older and newer technologies. We estimated

a saving per month of USD 3,486.89, or annual saving

of USD 41,842.76. The new technology was estimated

to result in a 32.99% cost savings in volatile agent

consumption.

Introduction and background

The costs associated with commonly used inhalation

anesthetics such as isoflurane, desflurane and sevoflurane

has been a popular topic for study in recent years. Early

computer prediction models were reported over ten

years ago, followed by pharmacoeconomic modeling

using low fresh gas flow anesthesia as a strategy in an

11-year retrospective analysis of isoflurane, desflurane

and sevoflurane. Most recently, a number of strategies

and policies have been reported to reducing amounts of

sevoflurane consumed during varying surgical procedures3,

as well as for shorter pediatric surgical procedures4,5.

However, in the course of our technology evaluation we

did not observe many study publications on the subject of

anesthetic machine performance in terms of longer term

surgical procedures, in excess of eight hours in length.

In addition to the considerable area of study for cost

containment in the management of inhaled anesthetics,

there are also increasing hospital concerns regarding the

environmental effects and ecological consequences of

these volatile agents6.

Prior to purchasing new technology to replace our aging

fleet of anesthesia machines, we rigorously tested a variety

of anesthetic machines provided by other companies listed

on our national framework. Although we went into the

decision process with a completely open mind, we soon

realized that there were key features that would be an

absolute requirement in our trial evaluation:

OBSERVATIONAL STUDY: ANESTHESIA AGENT CONSUMPTIONExPERIENCE OF VOLATILE AGENT COST SAVINGS wITH NEw ANESTHESIA DELIVERY TECHNOLOGY IN LONGER SURGICAL PROCEDURES

Performance

A significant proportion of our workload involves long

operations, often in excess of eight hours. As part of our

evaluation process, we scored machines based on their

performance during long operations. We felt it important to

do this for all the machines that we evaluated, as none of

the manufacturers provided data on their product’s

performance during extended operating times.

Ergonomics

In the majority of our operations, the surgeons are

working close to the airway of the patient. This requires

the anesthetic machine to be placed towards the foot end

of the table with the monitors facing away from the patient

allowing the anesthetist to view both the patient and the

monitors simultaneously. This is different from the vast

majority of theatre layouts when the anesthetic machine is

placed at the head of the patient alongside the anesthetist.

However, during our cases, there are times that the

anesthesiologist will also be working at the head of the

patient, requiring flexible ergonomics from the anesthesia

technology.

| Critical Care | Observational Study: AA Consumption |

“Anesthesic agent consumption with FLOW-i is significantly lower than with conventional

anesthesia machines”

“FLOW-i was estimated to result in a 32.99% cost savings in volatile agent consumption”

Ease of Use

Ease of use was another important consideration for our

department since our junior anesthetic staff are constantly

rotating through their training program and they are not

based permanently within our department.

Cost-efficiency

As we were replacing an aging fleet of anesthesia

machines, it was a requirement that the newer technologies

should indicate a general improvement in volatile agent

consumption during our prolonged surgical procedures.

Materials and methods

This report is a summary of our department’s experiences

of estimated cost reduction in volatile anesthetics in the

process of evaluating new anesthesia technology within

a five operating theatre suite providing anesthesia for

Neurosurgery & Oral and Maxillofacial Surgery, at Glasgow

Southern General Hospital in the United Kingdom.

The aim of the study was to compare the cost-

effectiveness of the FLOW-i anesthesia machine with our

conventional anesthesia machines, namely Datex-Ohmeda

Excel 210 and Aestiva.

The study was conducted in the Neurosurgery & Oral and

Maxillofacial Surgery Department, at Glasgow Southern

General Hospital in the United Kingdom. It included a

retrospective analysis of volatile agent consumption of

consecutive admitted patients at five operating theatres

and five anesthetic induction rooms between February 2012

and July 2013. We compared 6 months of volatile usage

with the 7 FLOW-i machines and the 3 older machines

during 2013, compared with the same period the previous

year (with the 10 older machines in 2012).

The bulk of the fleet of anesthesia machines in 2012 was in

excess of 15 years old (Datex-Ohmeda, Excel 210) and in

need of replacement, as the manufacturer’s support period

for consumable parts had expired.

In our product evaluation process, we found that the

FLOW-i anesthesia system performed exceptionally well

during long procedures. The system ergonomics and ease

of use provide a new level of flexibility.

During the evaluation period, our first impressions were that

the newer anesthesia delivery systems were significantly

more economical in usage of volatile agents compared

to our conventional anesthetic machines in general, and

that the FLOW-i anesthesia system (MAQUET) in particular

stood out from all the other systems we evaluated. More

specifically, in the FLOW-i system agent usage data is

available, albeit not exclusively. This feature of agent usage

calculation (Picture 1) at the end of each case indicated to

us that significant cost savings would be made.

The supply cost of the inhalational agents remained

unchanged during the study period.

Results

Based on our positive observations and experiences

during the evaluation period, a decision was made to

purchase seven FLOW-i anesthesia systems in 2013: five

of the systems have been installed in every operating

theatre, and two systems have been installed in 2 of the 5

anesthetic induction rooms. The remaining three anesthetic

rooms contain machines that are approximately 10 years

old, with conventional rotameters and Tec® vaporizers (3

Datex-Ohmeda / GE Aestiva machine). Unfortunately at the

time of purchase, financial constraints did not allow us to

replace all 10 anesthetic machines.

Our observations of potential cost-savings of volatile

agents in connection with FLOW-i during the evaluation

period led to a decision to chart anesthetic agent

consumption with the new anesthesia delivery systems

after our purchase in 2013 in order to conduct a

retrospective cost-savings analysis.

The new technology was estimated to result in a 32.99%

cost savings in volatile agent consumption which

significantly exceeded our expectations (Tables 1 & 2).

Picture 1. Agent usage window in FLOW-i (MAQUET)


Gross cost

Anesthesia systems

During Mar-Dec 2012 (9 months)

5 Excel 2105 Aestiva

During Mar-Aug 2013 (6 months)

3 Aestiva7 FLOW-i

Desflurane $ 56,188.88 $ 26,491.02

Isoflurane $ 307.36 $ -

Sevoflurane $ 38,639.59 $ 16,011.48

TOTAL $ 95,135.84 $ 42,502.50

Table 1. Gross cost of agent consumption of the hospital before and after using FLOW-i

Anesthesia systems

During 2012 Cost per month


During 2013 Cost per month

3 Aestiva7 FLOW-i

During 2012 Cost per year*


During 2013 Cost per year*

3 Aestiva7 FLOW-i

Desflurane $ 6,243.20 $ 4,415.18 $ 74,918.51 $ 52,982.03

Isoflurane $ 34.16 $ - $ 409.82 $ -

Sevoflurane $ 4,293.29 $ 2,668.59 $ 51,519.44 $ 32,022.98

TOTAL $ 10,570.65 $ 7,083.76 $ 126,847.77 $ 85,005.01

*Projected data from 10 months 2012 and 6 months 2013

Discussion

The volume reflector functions as a rigid reservoir for

exhaled gases for partial re-use by the patient during the

next inspiration phase (after passing through the CO2

absorber). Volume reflector technology offers rebreathing

up to 95% of all gases including nitrous oxide (N2O) and

fast change of anesthesia gas concentration (fast wash-in

and wash-out), if needed, saves time and anesthetic agent

consumption. This may explain the cost-savings we found

in our retrospective analysis.

Moreover, the volume reflector automatically compensates

the leakage with oxygen, which provides a safer anesthesia

with reduced risk for hypoxic mixtures if a leakage should

occur. This function becomes important especially while

using low fresh gas flows (minimum 0.3 L/min); with the

volume reflector. This is because drive gas oxygen is used

for leakage compensation; and the reflector gas module

supplies the system with oxygen replacing the lost volume

caused by the leak (Picture 1).


Monthly saving $ 3,486.89 Annual saving $ 41,842.76* Saving in percentage 32.99%

Picture 1. Volume Reflector

Table 2. Cost comparison (per month & per year) of before and after using FLOW-i Gross cost of agent consumption of the hospital before and after using FLOW-i

Conclusions

Anesthetic agent consumption with FLOW-i is

significantly lower than with conventional anesthesia

machines. More specifically, we estimated a saving per

month of USD 3,486.89, or annual saving of USD 41,842.76

in the expenditure on inhalational agents. The new

technology was estimated to result in a 32.99% cost

savings in volatile agent consumption. In addition to cost,

environmental impact should be considered when

evaluating new anesthesia technology. The majority of the

newer inhalational anesthesia agents are mostly exhaled

unchanged by metabolism, and the effect of anesthetic

agents on the destruction of the ozone layer is a well-

known fact7. Therefore having a high re-breathing factor is

preferred.

It would be important to assess whether the potential of

the FLOW-i anesthesia system in reducing agent

consumption is translated into improved outcomes on a

broader scale. More research and prospective studies are

needed in this respect.

Legal manufacturer:Maquet Critical Care ABRöntgenvägen 2SE-171 54 Solna, SwedenPhone: +46 8 730 73 00www.maquet.com

US Sales contact:MAQUET Medical Systems USA45 Barbour Pond DriveWayne, NJ 07470www.maquetusa.com

For local contact outside the US:Please visit our websiteswww.maquet.comwww.criticalcarenews.com

MX order number is valid outside USMCV order number is valid for US

Financial & competing interests disclosureThe author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

The views, opinions and assertions expressed are strictly those of the contributing clincian and do not necessarily reflect or represent the views of Maquet Critical Care AB.

About Dr. Suzanne Thomson

Suzanne Thomson MBChB FRCA is a Consultant in Anaesthesia and

Aeromedical Retrieval Medicine based in Glasgow, UK. Her anaesthetic

practice is in a major tertiary center for neurosurgery and oral and

maxillofacial surgery. Her main area of expertise is providing anaesthesia

and critical care for patients undergoing head and neck cancer surgery

involving free flap reconstruction. These procedures frequently have an

operating time in excess of 12 hours requiring prolonged anaesthesia.

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References:

1. Lockwood GG, White DC. Measuring the costs of inhaled anesthetics. Br. J. Anaesth. 87(4), 559-563 (2001).

2. Weinberg L, Story D, Nam J, McNicol L. Pharmacoeconomics of volatile inhalational anaesthetic agents: an 11-year retrospective analysis. Anaesth. Intensive Care 38(5), 849-854 (2010).

3. Ryu Ho-Geol, Lee Ji-Hyun, Lee Kyung-Ku et al. The effect of low fresh gas flow rate on sevoflurane consumption. Korean J. Anesthesiol. 60 (2), 75-77 (2011).

4. Singh PM, Trikha A, Sinha R et al. Phamaco-economics: Minute-based cost of sevoflurane in pediatric short procedures and its relation to demo-graphic variables. J. Anaesthesiol. Clin. Pharmacol. 29(3), 328-332 (2013).

5. Singh PM, Trikha A, Sinha R, Borle A. Measurement of consumption of sevoflurane for short pediatric anesthetic procedure: Comparison between Dion’s method and Dragger algorithim. J. Anaesthesiol. Clin. Pharmacol. 29(4), 516-520 (2013).

6. Feldman JM. Managing fresh gas flow to reduce environmental contami-nation. Anesth. Analg. 114, 1093-1101 (2012).

7. LangbeinT, Sonntag H, Trapp D, Hoffmann A, Malms W, Roth EP, Mors V, Zellner R: Volatile anaesthetics and the atmosphere: atmospheric lifetimes and atmospheric effects of halothane, enflurane, isoflurane, desflurane and sevoflurane. Br J Anaesth 1999, 82:66-73.

Conversion Rates:

The costs detailed in this document are calculated from the original GBP values from Suzanne Thomson into USD at the rate of 1 GBP = 1.585 USD.

Dr. Suzanne Thomson from Glasgow, United Kingdom

observational study: anesthesia agent...

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