Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3609_Библиотеки_им_академика_М_И_Перельмана
.pdf
10
a
b
c
https://t.me/medicina_free
A. Hertault
Fig. 2.1 When the X-ray beam passes through the tissue, three types of
situations are possible. The beam can pass through the material without
interaction, and therefore without energy loss (a). The beam can interact with electrons at the atomic level and be reected in another direc-
Fig. 2.2 At the output of the
X-ray generator, the beam is
uniform. As it passes through
the tissue, scattering and
absorption mechanisms come
into effect. When it reaches
the detector, the beam is
inhomogeneous and allows
the formation of the X-ray
image
tion, with or without energy transfer (b). In case of energy transfer
(Compton effect), an electron is ejected with an ionisation phenomenon. Finally, the entire energy of the beam can be absorbed at the
atomic level, again with ionisation (c). This is the photoelectric effect
In caregivers, the main deterministic effect found is
radiation- induced cataract, responsible for the appearance of
typical posterior subcapsular opacities. Previously, this complication was considered to occur after intense exposures (>5Gy),
but in recent years it has been considered that it could occur at
much lower thresholds (around 0.5 Gy) [6]. Observational
studies suggest that between interventional and non-interventional cohorts of cardiologists, the risk of observing posterior
subcapsular opacities would be up to 6 times greater [7, 8].
The incidence of deterministic effects following a medical procedure is estimated to be between 1/10,000 and
1/100,000 cases, but the true incidence is unknown due to
underdiagnosis and underreporting of this complication [9].
Stochastic Eects
Stochastic effects are related to DNA alteration. Unlike
deterministic effects, they are not triggered above a certain
threshold, which means that they can be induced even by
2 Principles andGuidelines forRadiation Protection
https://t.me/medicina_free
11
small exposures. On the other hand, it is known that their
probability of occurrence increases with life expectancy and
that a young subject will be at greater risk of developing a
complication related to a stochastic effect than an elderly
subject. Similarly, the severity is not correlated with the
intensity of the exposure. They can occur years after an
exposure. The main complications related to stochastic
effects are solid cancers, leukemia and transmission of
genetic abnormalities to offspring.
The possibility of stochastic effects is of particular concern for caregivers, who are repeatedly exposed to small
doses of radiation. Available data suggest an increased incidence of thyroid, breast, brain, and skin melanomas in occupationally exposed personnel [10–12]. With some studies
even reporting a risk of cancer that could be 20% higher in
exposed professionals compared to their unexposed colleagues [13, 14]. Unfortunately, the lack of large-scale cohort
follow-up of exposed workers over a long period makes it
impossible to assess the real risk of developing complications related to stochastic effects. The precautionary principle must therefore be applied.
What are theKey Principles ofRadiation
Protection?
The “As Low As Reasonable Achievable” or ALARA rule
governs the principles of radiation protection [15]. It can be
broken down into three main items:
– Justication: any use of X-rays must have an expected
benet greater than the theoretical risk incurred, which in
medicine overlaps with the traditional benet/risk bal-
ance. Thus, since exposure of a young subject is associ-
ated with a greater stochastic risk than for an elderly
subject, examinations or procedures requiring X-rays
should be avoided as much as possible. Similarly, when-
ever possible, an examination or technique that does not
require the use of X-rays should be preferred when simi-
lar results can be expected (e.g., ultrasound should be pre-
ferred to CT in the diagnosis of acute appendicitis). It is
interesting to note here that the benet/risk balance is less
clear for caregivers who are exposed to the risk but for a
collective rather than individual benet.
– Optimization: This principle brings together all the ele-
ments that will make it possible to reduce exposure when
it is necessary. It is often broken down into three parts: (1)
time: limiting as much as possible the exposure time, (2)
distance: increasing as much as possible the distance with
the source, and (3) shielding: protecting oneself. In daily
practice, it is based on the combination of good practices
and the optimization of the performance of imaging
equipment.
– Dose limits: This principle aims to set annual doses that
are considered “acceptable” for exposed workers.
Focus onOptimization: Tips andTricks
forDaily Practice
X-rays are odorless, colorless and soundless. Understanding
that one is exposed and at risk therefore requires increasing
one’s awareness to radiation. In this respect, passive and
active dosimeters are of considerable interest. Retrieving
monthly or annual dosimetry reports and comparing them
to the data available in the literature allows for a better
understanding of the potential for progress in radiation protection. It is also interesting to compare the radiation
reports provided by the imaging equipment and to compare
them to the data in the literature for a given type of procedure. In recent years, active dosimeter systems have been
available for tting over lead shielding. These dosimeters
provide real time information on the exposure of the operators during the procedures, thanks to a simple color code,
and thus allow to adjust one’s behavior in order to limit
one’s exposure [15]. Dose archiving softwares (DACS) are
also commercialized and allow a more detailed analysis of
the use of imaging systems in order to improve their settings and usage [16].
Methods to reduce the use of X-rays during interventional
procedures can be grouped into two main categories: On the
one hand, tricks that will allow to limit the number of images
produced, and on the other hand, those that will allow to
reduce the amount of X-rays necessary to produce an image.
Limit theNumber ofProduced Images
Limit Fluoroscopy Time
The operator must be trained to acquire images only during
times of interest and know how to release the pedal as soon
as it is possible. It is also necessary to remain vigilant not to
acquire images when not looking at the monitors. Modern
imaging technologies, such as image fusion, allow the positioning of the C-arm, the choice of working angulations or
the adjustment of collimation without having to resort to
image acquisition, which makes it possible to signicantly
reduce the number of images acquired, and thus the irradiation during a procedure [16–19].
Use Pulse Mode
The use of a continuous scopy mode should be avoided, in
favor of a pulsed scopy mode, i.e. based on the production of
X-rays over short periods, interspersed with free intervals.
Any procedure should be started in pulsed mode, with the
12
https://t.me/medicina_free
A. Hertault
lowest possible image rate to allow the procedure to be performed safely. If necessary, the image rate can be temporarily increased during the procedure to increase the image
resolution but be sure to return to the lowest image rate as
soon as possible. Reducing pulse rates from 30 to 15 or 7.5
pulses/s decreases uoroscopy dose by 47% and 72% respectively [20, 21].
Have theMain Operator Control theImaging
Equipment
Errors in communication or understanding can lead to unnecessary acquisitions or non-optimised use of X-rays. It is
advised that the primary operator keep control of the image
production to avoid this [22].
Limit theDose Required toProduce Images
Set UptheImaging Equipment
Imaging systems are equipped with an image quality
adjustment algorithm, called Automatic Exposure (or
Brightness) Control (AEC or ABC), allowing it to maintain a constant image quality, if necessary by increasing
the amount of X-rays delivered [9, 23, 24]. When the
W-ray beam crosses more esh (in obese patients or in
steep angulations for example) or when radiodense materials, such as surgical tools, are in the eld, the algorithm
will automatically increase the beam energy, without the
operator control, to maintain image quality. To make the
best use of an imaging device, it is necessary to dene
with the supplier the use that will be made of the imaging
equipment, and to set up the device so that the ABC algorithm with the best compromise between image quality
and delivered dose can be chosen for each type of
procedure.
Use Low Dose or Half Dose Settings
Imaging systems are equipped with options to modulate the
delivered dose, usually called low-dose (or half-dose) modes.
It is recommended to always start a procedure in low-dose
mode, and temporary revert to normal mode for the most
complex procedure times if necessary [25, 26].
Use Collimation
Collimation limits the size of the eld of view (FOV) to the
area of interest by using metal apertures to adjust the beam
size, thus limiting the exposure of surrounding tissue to
X-rays. It is generally considered that the reduction in radiation generated by collimation is equivalent to the area hidden, which means that a 30% reduction in FOV allows a 30%
reduction in delivered dose. In addition, it improves image
quality by limiting the background noise related to scattered
radiation [20, 27–29].
Limit C-Arm Angulation
As the C-arm is moved from anteroposterior to lateral incidence, the thickness of tissue to be penetrated generally
becomes greater, resulting in increased attenuation of beam
power and decreased image quality. However, imaging systems are congured to maintain constant image quality, so
the system will increase the beam power and delivered dose
in compensation. It is therefore essential to return to an
anteroposterior position as soon as possible [28, 30] and to
dene the least extreme working angles during the procedure. In this respect, 3D workstations are particularly useful
for planning these angulations before the procedure [31].
Optimize theImage Chain Geometry
To make the best use of the X-ray beam characteristics, it is
necessary to raise the operating table as high as possible and
lower the detector as close to the patient as possible. In this
conguration, the beam can widen enough to have a larger
FOV and a delivered dose spread over a broader area of skin
[32] (knowing that the FOV can then be adjusted by collimation). In addition, the closer the detector is to the patient, the
less chance the scattered radiation has of reaching it and generating background at that level [24, 32].
Limit Use ofDigital Subtraction Angiography
(DSA) (and Other Angiographic Modes)
The imaging system can produce images in uoroscopy and
angiography modes. Fluoroscopy is an image quality mode
adapted to allow guidance during interventional procedures,
with a reasonable delivered dose. Angiography modes,
including subtraction, are diagnostic modes requiring a more
powerful X-ray beam. It is therefore recommended that the
use of angiography modes be limited as much as possible
and that uoroscopy modes be preferred [9, 27, 33]. Modern
imaging systems allow subtraction in uoroscopy, as well as
digital storage of uoroscopy loops.
Avoid Magnication
Magnication is the action of focusing the X-ray beam on a
smaller area, in order to deliver more energy and thus obtain
a better image quality. This will increase the dose delivered
to the patient’s skin, as well as the scattered radiation for the
operators. It is generally recommended to avoid magnication if possible, or to use it only at specic times during the
procedure. Modern imaging systems are equipped with a
digital zoom option, which allows the image size to be
increased without increasing the radiation dose, but at the
cost of a decrease in image quality.
Impact ofEquipment
Modern imaging systems are equipped with technology that
allows for better image quality at a lower radiation cost.
Compared to traditional analogue image intensier, digital
2 Principles andGuidelines forRadiation Protection
https://t.me/medicina_free
13
at panel detectors offer a much higher sensitivity to X-rays
with a better signal-to-noise ratio and limited geometric distortion [34]. Digital image processing also makes it possible
to reduce irradiation through the use of software, some of
which have been mentioned above, such as image fusion,
digital zoom, subtraction and registration of uoroscopy
sequences, etc.
Individual Protection Measures
andShielding
The measures outlined above can reduce the intensity of the
primary X-ray beam and scattered radiation. However, it is
necessary to complement this with individual protective
measures to minimize exposure.
The Inverse Square Law
The energy carried by the scattered radiation decreases in
inverse proportion to the distance, the so-called inverse
square law where X=1/d2 (X=exposure, d=distance). The
rst measure to reduce exposure is therefore to move away
from the source of the radiation (i.e., the patient who acts as
the source of the scattered radiation for operators) [27].
Thus, it is recommended to take a few steps back when possible, to perform angiography sequences from the control
room using a power injector or to work with long sheaths
when appropriate.
Wearable Aprons
Leaded aprons are the most common form of personal protective equipment and can reduce by up to 90% the operator’s exposure [35]. For most interventional procedures, an
apron offering at least 35mm lead equivalent protection on
the front and 25mm on the back is sufcient. It is imperative
that the aprons are properly tted to the operator’s body to
avoid large gaps in the neck, back or underarms that would
leave entire areas of the body unprotected. In order to achieve
a more acceptable weight, most aprons use the overlap area
to provide adequate protection. For example, an apron with a
lead equivalent of 0.25 mm provides protection of
0.25+0.25= 0.50 mm lead equivalent at the overlap. It is
therefore imperative that the apron closes properly, otherwise the lateral parts of the abdomen are less well
protected.
Wearing a two-piece apron (skirt and top) allows for better weight distribution, improved comfort and tolerance, and
reduced osteoarticular complications.
Lead and its equivalents can crack or split if folded, considerably altering the effectiveness of the protection. It is
therefore essential to ensure that aprons are stored carefully
and that their condition must be checked regularly.
Thyroïd Collar
Although the radiosensitivity of the thyroid and the risk of
cancer decreases after the age of 20, the thyroid collar also
protects other potentially radiosensitive organs in the neck
such as the trachea or carotid arteries. It should be worn systematically [36] and quality control should be carried out
annually.
Positioning Around theTable
The scattered radiation is most intense at the point of beam
entry, i.e. in the normal working position under the operating
table. According to the same principle, when working with
lateral angles, the radiation received is more important on the
side of the generator, for example at the left oblique angle for
an operator located at the right groin of the patient [32].
When possible, another oblique angle should be used or the
operator should move.
Shielding
Personal or collective protective equipment uses X-ray ltering materials, such as lead, to attenuate the scattered radiation. As lead is relatively heavy, most modern equipment is
made of a composite alloy of other lighter attenuating metals
(barium, aluminum, tungsten, etc.). Their protection efciency is expressed in lead thickness equivalent.
Leg Shields
DNA alterations can be found in circulating cells of operators after an endovascular procedure without a table-mounted
shield or additional tibial protection [37]. Therefore, the use
of table-mounted shields (on both sides of the table), leaded
trolley or additional leg protection is necessary. This type of
protection can reduce the scattered radiation reaching the
lower part of the body by >90% [38].
Eye andUpper Body Protections
Given the specic risk of radiation-induced cataract, dedicated eye protection is essential. Eye protection includes
glasses with or without a corrective lens, t-over glasses that
can be positioned over the prescription glasses and visors.
Regardless of the type of protection chosen, it is important to
understand that scattered radiation generally arrives from the
side, so lead eyewear must cover the side of the eye toward
the temple to be effective [39].
The operator’s skull and body can also act as a secondary source of radiation by reecting some of the scattered
14
https://t.me/medicina_free
A. Hertault
radiation back to the eye, making it useful to place a larger
screen between the operator and the patient. Ceilingmounted lead shields can reduce up to 80% of the scattered
radiation to the upper part of the operator’s body during
femoral access procedures [38]. Their use should therefore
be systematic.
Controversial Protections
Leaded protective caps with a lead thickness of 0.5mm are
heavy (>1kg) and their discomfort limits their use. The new
generation of composite caps have shown inconsistent results
in terms of radiation protection effectiveness in the literature
[40, 41] and their use remains infrequent.
The protective drapes to be placed on the patient are sterile and contain a bismuth or tungsten alloy. They are placed
directly on the sterile eld, in order to block the scattered
radiation emanating from the patient. They make it possible
to partially limit the diffusion to the operator, in particular in
unprotected areas such as the hands [42]. Their main limitation remains that they must be positioned at a distance from
the acquisition eld, so as not to be in the FOV (which would
lead the auto-exposure algorithm to increase the dose in
compensation).
Leaded gloves are not commonly used because of their
stiffness and discomfort. They theoretically reduce radiation
to the hands, with an attenuation efciency of 15–30% [43,
44]. Their use is debated because the radiation passing
through them may end trapped between the layers, which
would result in an increased delivered dose to the hand.
Furthermore, it is essential to be careful never to position
them in the primary beam, as their attenuation would cause
the auto-exposure algorithm to increase the power of the
beam.
What YouShould Denitely Remember
X-rays are used in medicine for diagnostic or therapeutic
purposes. However, the contact between X-rays and tissues
is responsible for ionization phenomena that cause biological complications. Patients, located in the primary beam, are
at risk of radiation dermatitis in case of excessive exposure.
Health care workers, regularly exposed to scattered radiation, are at risk of cancer and radiation-induced cataract.
Because of these risks, it is essential to apply the benet/risk
balance to any use of X-rays.
During X-ray guided procedures, every effort should be
made to limit the number of images acquired, to adjust the
power of the primary beam, to reduce the exposure of the
health care workers and to protect themselves in an optimal
way. Together, these measures signicantly reduce patient
and staff exposure and create a safer working
environment.
References
1. Hall EJ, Giaccia AJ.Radiobiology for the radiologist. Philadelphia:
Lippincott Williams & Wilkins; 2006. https://books.google.fr/
books?id=6HhjwRyqBzgC
2. Bushberg JT. The essential physics of medical imaging.
Philadelphia: Lippincott Williams & Wilkins; 2002. p.965.
3. Russo P. Handbook of X-ray imaging: physics and technology.
Boca Raton: CRC Press; 2017. p.2926.
4. Hendee WR, Ritenour ER.Medical imaging physics. NewYork:
Wiley; 2003. p.535.
5. Koenig TR, Wolff D, Mettler FA, Wagner LK.Skin injuries from
uoroscopically guided procedures: part 1, characteristics of radiation injury. AJR Am J Roentgenol. 2001;177(1):3–11.
6. Chodick G, Bekiroglu N, Hauptmann M, Alexander BH, Freedman
DM, Doody MM, etal. Risk of cataract after exposure to low doses
of ionizing radiation: a 20-year prospective cohort study among US
radiologic technologists. Am J Epidemiol. 2008;168(6):620–31.
7. Elmaraezy A, Ebraheem Morra M, Tarek Mohammed A, Al-Habaa
A, Elgebaly A, Abdelmotaleb Ghazy A, et al. Risk of cataract
among interventional cardiologists and catheterization lab staff: a
systematic review and meta-analysis. Catheter Cardiovasc Interv.
2017;90(1):1–9.
8. Karatasakis A, Brilakis HS, Danek BA, Karacsonyi J, MartinezParachini JR, Nguyen-Trong PKJ, etal. Radiation-associated lens
changes in the cardiac catheterization laboratory: results from the
IC-CATARACT (CATaracts attributed to RAdiation in the CaTh
lab) study. Catheter Cardiovasc Interv. 2018;91(4):647–54.
9. Hertault A, Maurel B, Midulla M, Bordier C, Desponds L, Kilani
MS, etal. Editor’s choice—Minimizing radiation exposure during
endovascular procedures: basic knowledge, literature review, and
reporting standards. Eur J Vasc Endovasc Surg. 2015;50(1):21–36.
10. Zielinski JM, Garner MJ, Band PR, Krewski D, Shilnikova NS,
Jiang H, et al. Health outcomes of low-dose ionizing radiation
exposure among medical workers: a cohort study of the Canadian
national dose registry of radiation workers. Int J Occup Med
Environ Health. 2009;22(2):149–56.
11. Preston DL, Kitahara CM, Freedman DM, Sigurdson AJ, Simon
SL, Little MP, et al. Breast cancer risk and protracted lowto- moderate dose occupational radiation exposure in the US
Radiologic Technologists Cohort, 1983–2008. Br J Cancer.
2016;115(9):1105–12.
12. Rajaraman P, Doody MM, Yu CL, Preston DL, Miller JS, Sigurdson
AJ, etal. Cancer risks in U.S.Radiologic Technologists working
with uoroscopically guided interventional procedures, 1994–
2008. AJR Am J Roentgenol. 2016;206(5):1101–8. quiz 1109
13. Andreassi MG, Piccaluga E, Guagliumi G, Del Greco M, Gaita F,
Picano E.Occupational health risks in cardiac catheterization laboratory workers. Circ Cardiovasc Interv. 2016;9(4):e003273.
14. Wang JX, Zhang LA, Li BX, Zhao YC, Wang ZQ, Zhang JY, etal.
Cancer incidence and risk estimation among medical X-ray workers in China, 1950–1995. Health Phys. 2002;82(4):455–66.
15. Murat D, Wilken-Tergau C, Gottwald U, Nemitz O, Uher T,
Schulz E. Effects of real-time dosimetry on staff radiation exposure in the cardiac catheterization laboratory. J Invasive Cardiol.
2021;33(5):E337–41.
16. Hertault A, Rhee R, Antoniou GA, Adam D, Tonda H, Rousseau
H, et al. Radiation dose reduction during EVAR: results from a
prospective multicentre study (the REVAR study). Eur J Vasc
Endovasc Surg. 2018;56(3):426–33.
17. Maurel B, Martin-Gonzalez T, Chong D, Irwin A, Guimbretière G,
Davis M, etal. A prospective observational trial of fusion imaging
in infrarenal aneurysms. J Vasc Surg. 2018;68(6):1706–1713.e1.
18. McNally MM, Scali ST, Feezor RJ, Neal D, Huber TS, Beck
AW. Three-dimensional fusion computed tomography decreases
2 Principles andGuidelines forRadiation Protection
https://t.me/medicina_free
15
radiation exposure, procedure time, and contrast use during fenestrated endovascular aortic repair. J Vasc Surg. 2015;61(2):309–16.
19. Ahmad W, Obeidi Y, Majd P, Brunkwall JS. The 2D–3D registration method in image fusion is accurate and helps to reduce the used
contrast medium, radiation, and procedural time in standard EVAR
procedures. Ann Vasc Surg. 2018;51:177–86.
20. Ketteler ER, Brown KR.Radiation exposure in endovascular procedures. J Vasc Surg. 2011;53(1 Suppl):35S–8S.
21. Miller DL, Balter S, Noonan PT, Georgia JD. Minimizing
radiation- induced skin injury in interventional radiology procedures. Radiology. 2002;225(2):329.
22. Peach G, Sinha S, Black SA, Morgan RA, Loftus IM, Thompson
MM, et al. Operator-controlled imaging signicantly reduces
radiation exposure during EVAR. Eur J Vasc Endovasc Surg.
2012;44(4):395–8.
23. Kim KP, Miller DL, Balter S, Kleinerman RA, Linet MS, Kwon D,
etal. Occupational radiation doses to operators performing cardiac
catheterization procedures. Health Phys. 2008;94(3):211–27.
24. Lipsitz EC, Veith FJ, Ohki T, Heller S, Wain RA, Suggs WD,
et al. Does the endovascular repair of aortoiliac aneurysms pose
a radiation safety hazard to vascular surgeons? J Vasc Surg.
2000;32(4):704–10.
25. Dias NV, Billberg H, Sonesson B, Törnqvist P, Resch T,
Kristmundsson T. The effects of combining fusion imaging,
low-frequency pulsed uoroscopy, and low-concentration contrast agent during endovascular aneurysm repair. J Vasc Surg.
2016;63(5):1147–55.
26. Bicknell CD. Occupational radiation exposure and the vascular
interventionalist. Eur J Vasc Endovasc Surg. 2013;46(4):431.
27. Killewich LA, Falls G, Mastracci TM, Brown KR.Factors affecting
radiation injury. J Vasc Surg. 2011;53(1 Suppl):9S–14S.
28. Panuccio G, Greenberg RK, Wunderle K, Mastracci TM, Eagleton
MG, Davros W. Comparison of indirect radiation dose estimates with directly measured radiation dose for patients and
operators during complex endovascular procedures. J Vasc Surg.
2011;53(4):885–894.e1. discussion 894
29. Tonnessen BH, Pounds L. Radiation physics. J Vasc Surg.
2011;53(1 Suppl):6S–8S.
30. Kirkwood ML, Arbique GM, Guild JB, Timaran C, Chung J,
Anderson JA, etal. Surgeon education decreases radiation dose in
complex endovascular procedures and improves patient safety. J
Vasc Surg. 2013;58(3):715–21.
31. Stahlberg E, Planert M, Panagiotopoulos N, Horn M, Wiedner
M, Kleemann M, et al. Pre-operative simulation of the appropriate C-arm position using computed tomography post-processing
software reduces radiation and contrast medium exposure during
EVAR procedures. Eur J Vasc Endovasc Surg. 2017;53(2):269–74.
32. Haqqani OP, Agarwal PK, Halin NM, Iafrati MD. Minimizing
radiation exposure to the vascular surgeon. J Vasc Surg.
2012;55(3):799–805.
33. Durán A, Hian SK, Miller DL, Le Heron J, Padovani R, Vano
E.Recommendations for occupational radiation protection in interventional cardiology. Catheter Cardiovasc Interv. 2013;82(1):29–42.
34. Livingstone RS, Chase D, Varghese A, George PV, George
OK. Transition from image intensier to at panel detector in
interventional cardiology: impact of radiation dose. J Med Phys.
2015;40(1):24.
35. Badawy MK, Deb P, Chan R, Farouque O.A review of radiation
protection solutions for the staff in the cardiac catheterisation laboratory. Heart Lung Circ. 2016;25(10):961–7.
36. National Council on Radiation Protection and Measurements.
Radiation dose management for uoroscopically-guided interventional medical procedures. NCRP Report No. 168. Bethesda,
Maryland: National Council on Radiation Protection and
Measurements.
37. El-Sayed T, Patel AS, Cho JS, Kelly JA, Ludwinski FE, Saha P,
et al. Radiation-induced DNA damage in operators performing
endovascular aortic repair. Circulation. 2017;136(25):2406–16.
38. Fetterly KA, Magnuson DJ, Tannahill GM, Hindal MD, Mathew
V. Effective use of radiation shields to minimize operator dose
during invasive cardiology procedures. JACC Cardiovasc Interv.
2011;4(10):1133–9.
39. Kirkwood ML, Klein A, Guild J, Arbique G, Xi Y, Tsai S, etal.
Novel modication to leaded eyewear results in signicant operator eye radiation dose reduction. J Vasc Surg. 2020;72(6):2139–44.
40. Reeves RR, Ang L, Bahadorani J, Naghi J, Dominguez A,
Palakodeti V, etal. Invasive cardiologists are exposed to greater left
sided cranial radiation: the BRAIN study (BRAIN radiation exposure and attenuation during invasive cardiology procedures). JACC
Cardiovasc Interv. 2015;8(9):1197–206.
41. Kirkwood ML, Arbique GM, Guild JB, Zeng K, Xi Y, Rectenwald
J, et al. Radiation brain dose to vascular surgeons during uoroscopically guided interventions is not effectively reduced by wearing lead equivalent surgical caps. J Vasc Surg. 2018;68(2):567–71.
42. Vlastra W, Delewi R, Sjauw KD, Beijk MA, Claessen BE, Streekstra
GJ, et al. Efcacy of the RADPAD protection drape in reducing
operators’ radiation exposure in the catheterization laboratory. Circ
Cardiovasc Interv. 2017;10(11):e006058.
43. Wagner LK, Mulhern OR. Radiation-attenuating surgical gloves:
effects of scatter and secondary electron production. Radiology.
1996;200(1):45–8.
44. Kamusella P, Scheer F, Lüdtke CW, Wiggermann P, Wissgott C,
Andresen R. Interventional angiography: radiation protection for
the examiner by using lead-free gloves. J Clin Diagn Res JCDR.
2017;11(7):TC26–9.
Principles ofAnaesthesia
https://t.me/medicina_free
inEndovascular Procedures
N.Khan, P.Banugo, andH.Bidd
3
Case Study
A 73-year-old male patient with a history of hypertension,
type 2 diabetes, and peripheral vascular disease presented for
elective repair of a 6.5cm juxtarenal aneurysm. The plan was
to perform a fenestrated endovascular aneurysm repair
(FEVAR).
After placement of the stent graft, and following removal
of the femoral sheaths, the patient suddenly became hypotensive, with a fall in systolic blood pressure from 110 to
85 mmHg. Immediate management included intravenous
administration of a 250mL uid bolus and boluses of metaraminol to restore his blood pressure. An arterial blood gas
sample revealed a stable haemoglobin level, a potassium of
5.6mmol/L (previously 4.2mmol/L), a lactate of 2.7mmol/L,
and an elevated PaCO2 level. This picture was assumed to be
consistent with an ischaemic-reperfusion event following
lower limb reperfusion. The ventilation rate on the anaesthetic machine was increased, from 12 to 18 breaths/min, to
facilitate carbon dioxide removal, and uid resuscitation was
continued.
Within 20min, all parameters had normalised. The patient
was subsequently woken up and extubated without event.
Introduction
The ever-increasing scope of interventional radiology has
facilitated more complex patients being treated and managed
with an endovascular technique. Where previously vascular
disease, in particular arterial, was treated with an open technique, endovascular approaches can now be used to stabilise
and treat major pathology, often being reserved for patients
deemed high-risk and not suitable for an open approach.
Naturally, the anaesthetic approach has also evolved to match
the surgical insult. In this chapter, we will discuss the anaesthetic considerations for patients undergoing endovascular
procedures, both arterial and venous, and peripheral compared to central pathology.
Pre-operative Assessment
In the pre-operative setting, it is important to evaluate the
burden of disease and work towards risk factor modication
to reduce perioperative morbidity and mortality.
Peripheral vascular disease represents signicant systemic illness and is likely associated with other comorbidities, such as coronary artery disease, diabetes, renal
impairment, and frailty. From the data we can see common
co-morbidities can increase mortality by 3% up to 9%
(Table3.1).
Table 3.1 Outcome by comorbidities [1]
30-day
Comorbidity
Respiratory disease 3.7 1810
Ischaemic heart
disease
Cancer 3.8 1417
Arrhythmia 5.7 1029
Diabetes
(non-insulin)
Cerebrovascular
accident
Diabetes (insulin) 4.1 386
Congestive cardiac
failure
Documented cirrhosis 8.9 123
Data from a UK prospective audit of 13,513 patients having inpatient
surgery, March 1–7, 2010 (several patients had more than one
comorbidity)
mortality (%)
3.8 1457
2.9 1005
4.4 591
8.2 243
Number of patients with
comorbidity
N. Khan (*) · P. Banugo · H. Bidd
Guy’s and St Thomas’ NHS Foundation Trust, London, UK
e-mail: nazia.khan@gstt.nhs.uk; pele.banugo@gstt.nhs.uk;
heena.bidd@gstt.nhs.uk
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_3
17
18
https://t.me/medicina_free
N. Khan et al.
Cardiac Morbidity
Coronary artery disease has been seen in up to 50% of
patients having vascular surgery, with cardiac complication
rates as high as 13.5% [2]. Comprehensive guidelines from
the American College of Cardiology/American Heart
Association (ACC/AHA) recommend a stepwise approach
through a targeted history, assessing stability of disease, routine investigations such as pro-BNP levels and electrocardiogram (ECG) and risk stratication using the Duke Activity
Status Index [3]. Invasive investigations such as coronary
angiography, though useful in accurately quantifying coronary ow, are not readily available and unlikely to be warranted in asymptomatic patients. Multiple studies have
shown no benet in performing prophylactic angioplasty.
Unstable angina, signicant heart failure, poorly controlled atrial brillation or hypertension can be managed
with pharmacological intervention in both the acute and
elective setting. However, any optimisation programme is
likely to take 6–12weeks and therefore needs to be weighed
up against the urgency of surgery [4–6].
Endocrine Morbidity
day before their surgery to minimise haemodynamic instability caused by anaesthesia and dialysis. It is essential that
uid and electrolyte balance is as near to normal as possible.
Careful consideration must be given to patients having stuloplasty or thrombectomy of their stula as there is an associated rise in potassium on improving blood ow thus it is
vital to aim for a low to normal potassium level
pre-operatively.
Frailty
Frailty refers to a “distinctive health state related to the ageing process in which multiple body systems gradually lose
their in-built reserves”. The incidence of frailty in patients
aged 65years or more is about 10%, rising to between 25 and
50% after the age of 85years. The clinical impact of frailty
has less favourable outcomes in almost all studies compared
to the non-frail group, with studies showing longer hospital
stays, higher readmission rates, and decreased survival rates
[4, 10].
Understanding Risk
Prevalence of peripheral arterial disease (PAD) in diabetic
patients is estimated at 20% in the over 40-year-olds, increasing to 29% in the over 50s [7]. Though there have been no
specic studies in diabetic patients having endovascular procedures, when comparing all surgical patients, the diabetic
group continues to have a higher incidence of post-operative
complications and longer length of stay than the non-diabetic
group. Adequate diabetic control, measured through HbA1c
<8.5% is imperative in the elective scenario. For those having time critical surgery, diabetes control remains a priority
and can be achieved through a variable rate infusion if the
patient is likely to miss more than one meal. Often, these
patients present with critical limb ischaemia needing limb
revascularisation and each admission should be used as an
opportunity to improve diabetic control and reduce the risk
of further complications [8].
Renal Morbidity
Pre-morbid renal failure, pre-operative elevated creatinine
and post-operative acute kidney injury are all independent
risk factors for post-operative complications. In endovascular practise, measured volumes of contrast and avoidance of
nephrotoxic medication should be used in patients identied
as at risk of renal impairment [9]. Patients with known endstage renal disease should have their dialysis appropriately
timed with their endovascular repair. It is best performed the
Risk stratication tools can vary from a simple graded tool,
such as the American Society of Anaesthesiologists’ Physical
Status Score (ASA-PSS), to the Physiological and Operative
Severity Score for the enUmeration of Mortality and
Morbidity or POSSUM score. Some are disease specic, i.e.,
STOPBANG score for obstructive sleep apnoea, whilst others are predictors of 30-day mortality, like the SORT scoring
system [1, 11, 12].
Risk refers to the likelihood of a complication or adverse
outcome occurring during or after the procedure. Vascular
patients are likely to have a plethora of medical problems
thus the benets of any intervention needs to be balanced
against this. Though there is no single tool that can accurately predict the risk of endovascular procedures, it can be
estimated using scoring systems whilst bearing in mind the
level of surgical insult and burden of disease. Any discussion
should be centred on these three elements and balanced
against the urgency of the case.
Peripheral Limb Revascularisation
Peripheral limb revascularisation can refer to angioplasty,
venoplasty, thrombectomy, or stuloplasty in the elective,
urgent or acute setting. When planning the anaesthetic technique for patients requiring limb revascularisation, it is
important to consider: the site and duration of the procedure,
position of the patient, pre-morbid state of the patient, degree
3 Principles ofAnaesthesia inEndovascular Procedures
https://t.me/medicina_free
19
of symptoms the patient is suffering with, and the urgency of
the case.
Site andDuration
For both upper and lower limb work, the more distal the site
of stenosis, the more amenable it is to a regional technique.
The use of single shot nerve blocks is becoming common
practise. Insertion of a catheter (centrally or peripherally)
through which local anaesthesia can be continuously infused,
offers intra-operative anaesthesia and better post-operative
pain relief and side effect prole, then the analgesic options
available on the ward.
The use of regional anaesthesia must take into consideration what anticoagulant medications the patient is currently
taking, the patient’s coagulation prole, and the use of intraoperative heparin. In extremely high-risk patients, the balance of risk may favour a regional approach over a general
anaesthetic.
The sole use of regional anaesthesia lends itself well to
procedures less than 2h in duration. If it is anticipated that
the procedure will last several hours, the addition of sedation
or general anaesthesia should be considered as the limiting
factor for patient cooperation becomes discomfort in nonoperated sites, e.g., neck and leg stiffness and pain.
Position
Most endovascular repairs are done with the patient in the
supine position. However, if the patient is required to be
prone, general anaesthesia may be required to tolerate this
position for prolonged periods of time.
Symptomatology
In patients with peripheral arterial disease, rest pain is a common symptom. Patients often manage these symptoms by
hanging their foot off the end of the bed, which can make
performing any endovascular procedure quite challenging.
Revascularisation can also give rise to reperfusion pain.
Options for management of these symptoms are primarily
regional nerve block. Alternatively, the patient may require a
general anaesthetic to facilitate the procedure.
Endovascular Aneurysm Repair
The rst successful endovascular aneurysm repair (EVAR)
was performed in Buenos Aires in 1990, by Dr. Juan
C.Parodi and Dr. Julio Palmaz, under local anaesthesia [13].
As device design has improved, and expertise has developed,
more complex and technically challenging aneurysms are
being treated endovascularly, accounting for almost 80% of
elective abdominal aortic aneurysms treated.
Surgical Access
Irrespective of the level of aortic disease (infrarenal, juxtarenal, supra-renal, thoracic, or aortic arch), the surgical
approach is via either percutaneous or standard surgical incisions in one or both groins, although brachial access, and
less commonly subclavian access, is occasionally necessary.
Anaesthetic Technique
Since exposure of the diseased aorta and aortic-cross clamping is not needed, the endovascular approach is much less
invasive than open repair and widens the options for anaesthesia to include local anaesthesia, central neuraxial blockage (spinal or epidural anaesthesia), and sedation, in addition
to general anaesthesia.
Local Anaesthesia
An awake approach is appropriate for only a select cohort of
patients. Suitability should be assessed during the preoperative assessment and is inuenced by patient-related
factors, such as the ability to lie at for a prolonged period
and the ability to follow breathing commands intraoperatively. Combining a short-acting local anaesthetic (e.g.
lidocaine) with a long-acting drug (e.g. bupivacaine) allows
for rapid-onset loss of sensation at the surgical site followed
by prolonged action lasting several hours. Haemodynamic
instability is negligible with this approach. In an emergency
situation, e.g. ‘ruptured AAA’, local anaesthetic can be considered in especially unstable patients as a starting point,
with conversion to a general anaesthetic, if needed, once the
patient is more stable. Patients should be warned about the
possibility of ischaemic pain in the buttocks and legs. This is
due to prolonged occlusion of femoral and iliac arteries.
Central Neuraxial Blockade
Endovascular aneurysm repair can be performed under either
spinal anaesthesia or epidural anaesthesia, although a combined spinal epidural approach may be the preferred. The
onset of the spinal component takes 10–15min and provides
effective anaesthesia for approximately 90–120 min. For
longer surgery, a combined spinal epidural approach can be
used with the epidural component being ‘topped up’ with
bupivacaine to extend the period of anaesthesia. The epidural
component can further be used to provide analgesia in the
post-operative period, if necessary. It is important to follow
20
https://t.me/medicina_free
N. Khan et al.
the latest guidance on central neuraxial procedures in patients
on anticoagulants. Adherence to this reduces the risk of epidural haematoma formation. At least 60min should elapse
between the performance of neuraxial blockade and administration of unfractionated heparin intraoperatively [14].
Sedation
Sedation is a technique that uses pharmacological agents to
make a patient comfortable enough to tolerate minor or minimally invasive procedures. Sedation can be delivered on a
spectrum from light to deep, titrating to the desired effect.
There are many contributing factors to the effectiveness of
sedation; the choice of pharmacological agent used, the theatre environment, and the willingness of the patient, are all
vital elements that need to be carefully balanced to achieve
optimal sedation. A single agent, or multiple agents, can be
administered as a bolus dose or via an infusion, inuenced
by the type of procedure and severity of pain likely to be
experienced. Sedation can also be used in conjunction with
regional anaesthesia to enhance the patient experience.
General Anaesthesia
This approach should be reserved for procedures that are
likely to take in excess of 3–4h, or if a patient is unable to
tolerate the procedure under alternative options. Total intravenous anaesthesia (TIVA) with tracheal intubation works
well, allowing for stable intraoperative conditions with
smooth, rapid emergence from anaesthesia.
Simple Versus Complex EVAR
sidered with the more complex procedures. Invasive blood
pressure monitoring, patient warming, and urinary catheter
insertion should always be instituted.
Intra-operative blood loss is minimal for simple infrarenal EVARS but the risk increases with increased complexity of the procedure, thus it is vital to have cross matched
blood available and access to a rapid infusion device. The
need for brachial access should be discussed at team brief
and peripheral lines placed on the contralateral side. Aim for
a rapid wake up post procedure to allow early assessment of
neurological function, especially if spinal cord ischaemia is
a risk.
Aortic Arch Branched Repairs andThoracic
Endovascular Aortic Repair (TEVAR)
In patients not suitable for an open arch repair and cardiopulmonary bypass, or deep circulatory arrest, an endovascular method can be used. To assist this approach, rapid
ventricular pacing may be necessary [16]. Rapid pacing is
performed through insertion of a temporary pacing wire
into the internal jugular or subclavian vein to the right ventricle. A short period of rapid pacing will cause profound
hypotension, limiting blood ow through the aortic arch
and facilitating deployment of the endograft into the
ascending aorta.
Similarly, some thoracic endovascular aneurysm repairs
(TEVAR) may also need graft deployment into the arch of
aorta and rapid ventricular pacing, in certain
circumstances.
Procedure complexity and duration, patient comorbidities
and patient preference all inuence the choice of anaesthetic
technique. Complex EVARs are likely to take 3–4h and are
typically performed under general anaesthesia unless the
patient is considered to be frail and high-risk, when local
anaesthetic with sedation may be considered more
appropriate.
The risk of contrast-induced nephropathy increases with
the dose of contrast used. Patients at risk include those with
preoperative renal impairment, cardiac failure, patients having para-renal stents sited, and patients undergoing prolonged, complex procedures [15]. Every effort should be
made to limit the amount of contrast used. The patient must
continue to be hydrated well into the post-operative period
and nephrotoxic drugs should be avoided. No other treatments have been proven to reduce the risk of acute kidney
injury.
Large bore venous access is mandatory for all EVARs.
Central venous access is rarely necessary but should be con-
Spinal Cord Ischaemia
Spinal cord ischaemia refers to the loss of perfusion to the
spinal cord during thoraco-abdominal aneurysm repair. This
rare, but devastating, risk is more commonly associated with
an open surgical approach, however, the incidence during
TEVAR remains at 0–10.3%, average of 4.5% [17, 18].
Patients typically present with symptoms of incontinence
and impaired motor function with some preserved sensory
function in the immediate post-operative period. It is possible to mitigate some of this risk through staging surgery,
maintaining physiological parameters, and insertion of a spinal drain.
In patients having a complex thoracic repair, a staged
approach to surgery over several months allows collateral
blood supply to form and provides extra protection to the
spinal cord if it should suffer from signicant aortic blood
loss or ischaemia intra-operatively.
Соседние файлы в папке Библиотека им академика М.И. Перельмана