See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/293797227 Influence of supraglottic airway device placement on cerebral hemodynamics Article in Minerva anestesiologica · February 2016 CITATION 1 READS 53 8 authors, including: Some of the authors of this publication are also working on these related projects: FGFR1 and cardiomyocytes View project Sedation View project Frank Aanthony Rasulo Università degli Studi di Brescia 44 PUBLICATIONS 1,053 CITATIONS SEE PROFILE Simone Piva Spedali Civili di Brescia 25 PUBLICATIONS 189 CITATIONS SEE PROFILE Arturo Toninelli Spedali Civili di Brescia 5 PUBLICATIONS 10 CITATIONS SEE PROFILE Stefano Calza Università degli Studi di Brescia 121 PUBLICATIONS 3,265 CITATIONS SEE PROFILE All content following this page was uploaded by Simone Piva on 04 July 2016. The user has requested enhancement of the downloaded file.
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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/293797227
Influence of supraglottic airway device placement on cerebral hemodynamics
Article in Minerva anestesiologica · February 2016
CITATION
1
READS
53
8 authors, including:
Some of the authors of this publication are also working on these related projects:
FGFR1 and cardiomyocytes View project
Sedation View project
Frank Aanthony Rasulo
Università degli Studi di Brescia
44 PUBLICATIONS 1,053 CITATIONS
SEE PROFILE
Simone Piva
Spedali Civili di Brescia
25 PUBLICATIONS 189 CITATIONS
SEE PROFILE
Arturo Toninelli
Spedali Civili di Brescia
5 PUBLICATIONS 10 CITATIONS
SEE PROFILE
Stefano Calza
Università degli Studi di Brescia
121 PUBLICATIONS 3,265 CITATIONS
SEE PROFILE
All content following this page was uploaded by Simone Piva on 04 July 2016.
The user has requested enhancement of the downloaded file.
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2 BACKGROUND: Supraglottic airway devices (SGDs) are of current use in anesthesia practice and
in emergency conditions. It has been suggested that cerebral blood flow (CBF) can decrease after
SGD insertion or cuff inflation; however, it is uncertain if this reduction is caused by the SGD or
the anesthetic drugs utilized for the anesthetic procedure. During minor surgery we separated CBF
measurements by an adequate time interval in order to measure the distinctive changes in cerebral
hemodynamics associated with anesthesia induction, SGD insertion and cuff inflation.
METHODS: Patients scheduled for minor surgery requiring general anesthesia and SGD placement
were included. Middle cerebral artery mean flow velocity (FVm-mca) and the pulsatility index (PI)
were measured through use of trans-cranial Doppler (TCD) at baseline, after anesthesia induction,
SGD insertion and cuff inflation, once a steady cardio-circulatory state was reached and end tidal
CO2 (etCO2) was within normal range.
RESULTS: A total of 21 patients were included. Following anesthesia induction, in concomitance
to a reduction in mean arterial pressure (MAP), there was a mean decrease in FVm-mca by 16.60
cm/s, p<0.005 and a mean increase in PI by 0.24, p<0.0015. MAP, FVm-mca and PI did not change
significantly, neither after SGD placement (p>0.05), nor after SGD cuffing (p>0.05).
CONCLUSION: SGD insertion and cuff inflation did not influence cerebral hemodynamics in
anesthetized patients undergoing minor surgery. At normal etCO2 range, the CBF reduction with
transient increase in PI was associated with anesthesia induction and not SGD insertion itself.
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3 Introduction
The Laryngeal Mask Airway device (LMA) was first developed by British Anesthesiologist Dr.
Archie Brain and has been in use since 1981.1 In patients with out-of-hospital cardiac arrest
(OHCA) undergoing cardiopulmonary resuscitation (CPR), although the gold standard for airway
management is represented by endo-tracheal intubation, the SGD has been used as an alternative
due to its rapid placement without the need for CPR interruption.2-6 In fact, pre-hospital
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4 Therefore, it is currently not clear if SGD insertion and/or cuff inflation induce significant
variations of cerebral hemodynamics in humans, or if the observed changes in CBF described in
literature are indeed caused by anesthetic drugs or coincidental systemic ventilatory variations.
We took advantage of minor elective surgical operations, where procedural times are not as
stringent as in major or emergency surgery, to separate CBF measurements by an adequate time
interval in order to measure the distinctive changes in cerebral hemodynamics and to evaluate if
these changes are associated with anesthesia induction or SGD insertion and/or cuff inflation.
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5 Materials and Methods
Approval for the study, was obtained from the Local Ethics Committee on the 2nd of July, 2014 (ID-
1625 n.29) and written inform consent was obtained from all participants. The study was conducted
in the Plastic Surgery and Gastro-intestinal Endoscopy operating rooms of the Spedali Civili
university-affiliated hospital of Brescia, from July 2013 to January 2014. Patients were included if
they were 18 years of age or older, were scheduled for elective plastic or reconstructive surgery or
colonic and rectal endoscopy surgery requiring general anesthesia and SGD placement, were
hemodynamically stable with an ASA Physical Status Classification System of 2 or less, and had a
valid cranial acoustic temporal bone window for Doppler insonation. Patients with known carotid
artery disease, dysautonomic conditions that can be associated with altered CVA status either
caused by central nervous system disease (Shy-Drager syndrome, Parkinson’s disease, Lewy-body
dementia, pure autonomic failure) or peripheral nervous system disease (diabetes, amyloidosis,
Sjogren syndrome, autonomic neuropathies) were excluded from the study.22-25 All patients had the
same type of SGD, (Laryngeal Mask Airway Unique, Le Rocher, Victoria, Mahe, Seychelles)
which was placed by the same anesthesiologist . The SGD size and the cuff inflation volumes were
chosen according to those suggested by the manufacturer; size 3 SGDs (adults up to 50kg) were
inflated with 20 ml room air, size 4 (adults 50-70kg) with 30 ml and size 5 (> 70kg) with 40 ml.
The anesthesia technique was standardized using total intravenous anesthesia, and comprised
induction with propofol 1-2 mg kg-1 and fentanyl 1-2 μg kg-1, and maintenance with propofol 3-6
mg kg-1 hr -1 and remifentanyl 0.05-0.1 μg kg1 min-1. No muscle relaxants were used.
Monitoring included non-invasive ABP, heart rate (Infinity®Delta monitor, Dräger, Lübeck,
Germany), arterial oxygen saturation with pulse oximetry and end-tidal CO2 (etCO2). Mechanical
ventilation (Primus®ventilator, Dräger, Lübeck, Germany) settings were standardized so as to
maintain normal ranges in order to avoid any influence of arterial blood gases on cerebral
vasoreactivity and CBF (tidal volume 6-8ml/kg, respiratory rate set in order to maintain a etC02
between 35 - 40 mmHg and fraction of inspired oxygen at 0.35). After SGD insertion and before
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7
Statistical analysis
We expressed continuous variables as means and standard deviation (SD) or as medians and range
(absolute range or interquartile range [IQR]), and discrete variables as counts (percentage), unless
otherwise stated. Differences of CBF variables at various time points were analyzed by means of
repeated measurement ANOVA fitted by linear mixed models using subject as random effect.
Assuming a minimum effect size (expected difference between group means/standard deviation) of
0.7 (assumed within group standard deviation = 10) and 0.15 (SD = 0.2) respectively for FVm-mca
and PI, power 0.8 and significant level of 0.05 we estimated a sample size of 21.26 Tests were two
tailed, and p<0.05 was considered as significant. The data were analyzed with STATA 8.0 and R
(version 3.1.1 R Development Core Team, GNU General Public License).
Results
A total of 21 consecutive patients undergoing general anesthesia with SGDs were included and
studied within a time-span of three months. Surgical interventions included 12 patients who
underwent plastic surgery and 9 patients colonic and rectal endoscopy surgery.
Patient demographics, including ASA mean = 2 [range 1-3], BMI mean = 24.6 [range 20-37], age
mean = 45.6 [range 18-75], and etCO2 values post-SGD insertion and post-SGD cuffing and the
difference between the readings during these two time frames (p>0.05), are listed in Table 1. The
etCO2 ranged from 35-40 mmHg (mean 36.6 mmHg [SD 2.7]) during the measurements, and the
average cuff inflation volume was 30.7 ml (range 30-40 ml [SD 5.1]) with an average pressure of
57.4 cmH2O [SD 1.7] (range 54 – 60 cmH2O). Anesthesia induction was performed with propofol
and fentanyl, and maintenance with propofol and remifentanil in all patients.
Following anesthesia induction, there was a statistically significantly decrease in mean arterial
pressure (MAP, Figure 1a) from a baseline value of 93.5 mmHg [SD 13.8] to 66.0 mmHg after
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This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher.
9 Another finding of this study was that PI increased concomitantly with the decrease in FVm-mca
and CBF. Several studies support the interpretation of PI as a reflection of the distal cerebro-
vascular resistance, attributing greater PI to higher cerebro-vascular resistance. However, PI may
also increase as a consequence of reduced cerebral perfusion pressure in animals with intact CVA,
such as during hypercapnia31. In order to exclude the influence of CO2 on PI, etCO2 was monitored
immediately following SGD placement and for the rest of the procedure. The difference in etCO2
values immediately post-SGD placement and post-SGD cuffing were not statistically significant
(Table 1). Consequently, the increase in PI was most likely caused by cerebral vasodilation
secondary to ABP reduction with secondary transient increase in cerebral blood volume and
intracranial pressure. These changes, which are transient and likely to be clinically irrelevant in
patients with good general condition and normal brain compliance, support the paradigm of
anesthetic-induced systemic hypotension with secondary cerebro-vascular modification.
In order to exclude the influence of SGD cuff pressure on FV and PI, we maintained cuff pressure
constant throughout the whole procedure at pressures suggested by the manufacturers. The
importance of SGD cuff pressure on the incidence of pharyngo-laryngeal adverse effects has been
recently underlined in a study which confronted the incidence of “pharyngo-laryngeal discomfort”
between a tight control of pressure maintained at 60 cmH2O with a second control group in whom
there were no corrections in cuff pressure but only measurements. Compared to the control group,
there was a reduction in adverse events in the group in whom the cuff pressure was maintained
constant at 60 cmH2O, although the influence on cerebral hemodynamics was not evaluated.32
Some differences compared to a few papers published previously in literature should be pointed out;
our results contradict those of Colbert SA and colleagues who showed that SGD cuff inflation
caused a reduction in the cross sectional area of the carotid artery leading to a reduction in CABF.14
In their study the time intervals used between CABF measurements were not specified, and hence,
it is not certain to what extent the reduction of CABF was due to the reduced cross section area of
the carotid artery or the hypotensive effect of the anesthetic drugs. Furthermore, it is not clear why
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10 cuff deflation lead to a significant increase of carotid cross-sectional area without any significant
variations in blood flow velocity. Compared to the study by Segal N and colleagues, who based
their study on a swine model during CCA, our study was performed in humans, and within a
general anesthesia setting.17 Another difference between the two models may be anatomical; in fact,
the human carotid arteries are found more lateral and further away from the trachea, and the
digestive tract is covered by the deep cervical fascia which may inhibit further changes in the
carotid cross section, rendering the carotid artery less vulnerable to effects caused by SGD insertion
compared to pigs.18
Limitations of the study
First, only a limited number of surgical patients in a hemodynamically stable condition were
studied; therefore, generalizing the results to other patient populations with more severe clinical
conditions such as those with cardiac arrest undergoing cardio-pulmonary resuscitation, is not
warranted. Second, cerebral blood flow velocity is not a direct measurement of CBF and depends
greatly on the radius of the middle cerebral artery that should remain constant for the measurement
to be accurate. Third, we did not test CVA before induction of anesthesia, although we carefully
excluded patients with autonomic dysfunction who are at increased risk of altered CVA alteration.
Future animal studies should replicate our model with steady-state CBF measurements rather than
CABF measurements during attempted resuscitation following cardiac arrest. If the proposed
hypothesis of anesthetic-induced systemic hypotension with induced cerebro-vascular changes
holds true, patients with intact or altered CVA should demonstrate different PI time-trends.
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11 Conclusions
SGD placement and cuffing did not influence cerebral hemodynamics in patients undergoing
general anesthesia for minor elective extracranial surgery. FVm-mca decreased and PI increased as
a consequence of the reduction in ABP following anesthesia induction. The proposed model of CBF
measurement in steady-state condition using TCD or other invasive methods should be replicated in
experimental animal settings of unstable circulatory conditions to separate the differential effects of
multiple explanatory variables of CBF reduction.
Core Messages
1) SGD placement and cuffing do not cause per se variations in cerebral hemodynamics in patients
with intact cerebrovascular autoregulation, and therefore can be safely used for airway
management during general anesthesia for extracranial surgery;
2) Drugs used for general anesthesia induction, such as propofol and remifentanil, cause a drop in
cerebral blood flow and blood flow velocity, most likely due to anesthetic-induced hypotension
and flow/metabolism coupling;
3) Anesthetic induced hypotension may cause an increase in PI in patients with intact CVA;
4) These findings warrant further investigation in patients with brain injury, at risk of having altered
cerebrovascular autoregulation, undergoing general anesthesia.
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12
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This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher.
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Chantzara G, Stroumpoulis K, Alexandrou N, Kokkinos L, Iacovidou N, Xanthos T.
Influence of LMA cuff pressure on the incidence of pharyngolaryngeal adverse effects and
evaluation of the use of manometry during different ventilation modes: a randomized
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Patient Number
ASA BMI (Kg/m2)
AGE etCO2 (mmHg) Differential etCO2
(mmHg) Post-SGD insertion
Post-SGD cuffing
1 2 23 18 36 37 1
2 1 22 38 36 36 0
3 2 31 46 37 36 -1
4 1 25 18 38 40 2
5 2 24 38 40 40 0
6 2 23 18 40 39 -1
7 2 22 52 38 38 0
8 2 20 37 35 36 1
9 2 24 52 38 39 1
10 2 37 60 36 35 -1
11 2 30 63 34 32 -2
12 2 25 68 36 34 -2
13 2 26 65 32 33 1
14 2 24 65 40 38 -2
15 2 23 42 38 38 0
16 1 20 43 32 33 1
17 2 26 41 40 39 -1
18 2 21 47 36 36 0
19 2 22 75 35 34 -1
20 2 24 50 37 37 0
21 2 25 22 38 36 -2
Table 1. Patients ASA (American Society of Anesthesiology physical
status classification system), BMI (body mass index), age, etCO2 (end
tidal carbon dioxide in mmHg) values post-SGD insertion and post-SGD
cuffing (p > 0.05). The last column showing the differential values between
This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher.
This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher.
This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher.