Establishing Routine Preoperative Gastric Ultrasound for Patients With an Increased Aspiration Risk in a Swiss Teaching Hospital: A Prospective Observational Study.
Conditions: Gastric Ultrasound
Sponsor: Kantonsspital Winterthur KSW

 
Establishing routine preoperative gastric ultrasound for patients with an increased aspiration risk in a Swiss teaching hospital:  
A prospective observational study. 
 V3.0, 25.01.2021 
Page 1 of 29   
 
 
 
Establishing routine preoperative gastric ultrasound for patients with an 
increased aspiration risk in a Swiss teaching hospital:  
A prospective observational study. 
 
Project Category: Observational Study - Risk category A 
 
Project Short Title: Gastric sonography before anaesthesia inductions  
 
Sponsor 
Prof. Dr. med. Michael T. Ganter 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15, 8400 Winterthur, Switzerland 
+41 (0)52 266 2790 
michael.ganter@ksw.ch 
mt.ganter@gmail.com  
Principal Investigator 
Dr. med. Roman Meierhans 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15, 8400 Winterthur, Switzerland 
+41 (0)52 266 4846 
roman.meierhans@ksw.ch  
Project Plan Version number 
und Date: 
 
Version 3.0 – 25.01.2021 
Project Identifier: 
2020-02858 
Category 
HFV Project Category A 
CONFIDENTIAL 
The information contained in this document is confidential and the property of the department of An-
aesthesiology of the Cantonal Hospital of Winterthur. The information may not - in full or in part - be 
transmitted, reproduced, published, or disclosed to others than the applicable Independent Ethics 
Committee(s) and Competent Authority(ies) without prior written authorization from department of An-
aesthesiology of the Cantonal Hospital of Winterthur, to the extent necessary to obtain informed con-
sent from those participants who will participate in the project. 

 
Establishing routine preoperative gastric for patients with an increased aspiration risk in a Swiss teaching hospital:  
A prospective observational study. 
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Synopsis 
 
Sponsor 
Prof. med. Michael T. Ganter  
Principal investigator 
Dr. med. Roman Meierhans  
Study Title: 
Establishing routine preoperativ gastric ultrasound for patients with 
an increased aspiration risk in a Swiss teaching hospital: A pro-
spective observational study 
Short Title / Study ID: 
Establishing gastric sonography in a Swiss teaching hospital 
2020-02858 
Protocol Version and Date: 
V3.0 – 25.01.2021  
Trial registration: 
Clinical Trials.gov: to be determined 
Study category and Ra-
tionale 
HFV Project - Category A 
Gastric sonography is a low risk examination. No ionizing radiation 
is used. Theoretical complications including sensation of local pres-
sure or pain, regional exanthema or allergic reactions to ultrasonic 
gel will at most be very minor. The complete examination takes ap-
proximately five minutes, accordingly anaesthesiologic and surgical 
procedures will not be significantly delayed. Patients and interven-
tions where even a minimal delay may provide a potential health 
risk are not included in this study. 
Background and Rationale: 
Aspiration pneumonias still exhibit a significant morbidity and mor-
tality1-6 and are accountable for a significant part of anaesthesia-re-
lated deaths. Various diseases and especially emergency situations 
correlate with prolonged gastric emptying and therefore with a 
higher risk of pulmonary aspiration. In clinical practice the decision 
to perform a Rapid Sequence Induction (RSI) is mostly based on 
clinical and anamnestic findings. Preoperative gastric sonography 
may provide an objective, validated, non-invasive, reliable, fast, and 
cost-efficient approach to assess aspiration risks in both elective 
and emergency patients.  
How this highly sensitive and specific tool may be best introduced 
and implemented in daily clinical practice or anaesthesiologic 
guidelines remains unclear. Structured educational programmes or 
training recommendations for this point-of-care ultrasound applica-
tion rarely exist. 
Objectives: 
1. Establish preoperative gastric sonography before Rapid Se-
quence Induction (RSI) and patients with one or more aspi-
ration risk factors scheduled for a advanced laryngeal mask 
or regional anaesthesia at the Kantonsspital Winterthur, 
Department of Anaesthesiology.   
2. Validation of our structured training/education by comparing 
sonographic estimated and directly measured gastric con-
tent. 
3. Emphasize the importance and effectiveness of this diag-
nostic tool to improve anaesthesiologic management. 

 
Establishing routine preoperative gastric for patients with an increased aspiration risk in a Swiss teaching hospital:  
A prospective observational study. 
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Outcomes: 
Primary Endpoint: 
- Correlation of sonographic estimated gastric volume with volume 
aspirated through a naso- or orogastric tube. 
Secondary Endpoints: 
- Performance over time, improvement of examination technique, 
critical number of examinations to achieve a high quality standard 
(>80% congruece for estimated and aspirated gastric volume in flu-
ids). 
- Association of performance with experience, residents vs. attend-
ings. 
- Number of patients classified as empty -> possible implications for 
management and induction 
- Number of patients with full stomach -> possible implications for 
management and induction 
- Time used for examinations, time used with growing experience. 
- estimated aspiration risk vs. sonographic gastric volume 
- Total number of pulmonary aspirations 
Study design 
A prospective observational study 
Inclusion criteria: 
 
All elective in-hospital Rapid Sequence Inductions (RSI) 
and patients with one or more aspiration risk factors sched-
uled for a advanced laryngeal mask or regional anaesthesia 
with informed consent. 
 
All emergency in-hospital RSI and patients with one or 
more aspiration risk factors scheduled for an advanced lar-
yngeal mask or regional anaesthesia with informed consent 
graded as follows according to the Swiss Society for An-
aesthesiology and Resuscitation (A-QUA): “Notfall 1-6h, 
nicht vital (dringlicher Eingriff)”, “Notfall 6-24h nicht vital 
(aufgeschobener dringlicher Eingriff)” 
Exclusion criteria: 
 
Life threatening/ time critical emergency interventions, 
graded followingly according to the Swiss Society for An-
aesthesiology and Resuscitation (A-QUA): “Notfall <1h, vi-
tal (sofortiger Eingriff notwendig)” 
 
Known Pregnancy 
 
Obstetric surgery 
 
Underage (< 18 years) 
 
Absence of informed consent (missing or inability to pro-
vide) 
 
No anaesthetist with completed structural education in gas-
tric sonography is available. 
 
Contraindications for naso- or orogastric tubes or inability to 
correctly place such.  
Intervention, Measure-
ments and procedures: 
Our study will be performed mainly in the induction rooms of our op-
erating ward and occasionally inside the operating theatre. Stand-
ard care will be given to every patient at the usual location, with our 
usual equipment (anaesthetic machine, monitoring, medication and 
airway devices etc) and by our usual anaesthesiologic team mem-
bers. Sonographic examination and determination of the gastric 
content will be executed on one of our standard ultrasound ma-
chines (Venue and LOQIC e from GE-Healthcare®) with a curved 

 
Establishing routine preoperative gastric for patients with an increased aspiration risk in a Swiss teaching hospital:  
A prospective observational study. 
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array low frequency (2-10 Hz) abdominal probe or portable ultra-
sound devices (IQ+ from Butterfly Network Inc. ®). 
Control Intervention: 
 
Number of Participants 
with Rationale: 
A total number of 2’718 general anaesthesia with Rapid Sequence 
Inductions (RSI) was undertaken at our institution in 2019. Thereof, 
275 were children < 18 years of age. 204 Rapid Sequence Induc-
tions were performed in category: “Notfall <1h, vital, sofortiger 
Eingriff notwendig” and therefore not includable. Therefore, expect 
to include around 1500 - 2200 patients in a one year period. 
Study Duration: 
Estimated duration of the project: 18 months 
Planned start: 01/2021 
Planned project close: 06/2022 
Study Schedule: 
Project specific: 
 
Time period for participant recruitment: 12 months 
Project start (FPFV): 01/2021 
 
Project end (LPLV): 12/2021 
Investigators: 
Michael T. Ganter (Sponsor), Roman Meierhans (PI)  
 
Co-Investigators: 
Sascha J. Baettig, Mark G Filipovic, Daniela Widmer 
 
Sub-Investigators: 
All anaesthesia faculties and residents of the department of Anaes-
thesiology, Kantonsspital Winterthur after completion of our special 
training program in gastric sonography (see Chapter 8) 
 
All investigators are members of: 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
 
Study Centre: 
This study will be conducted at the Department of Anaesthesiology 
at the Cantonal Hospital of Winterthur, a Swiss teaching hospital. In 
our department we care for a total of approximately 18’000 patients 
per year. The anaesthetic physician team consists of 25 quali-
fied/staff anaesthetists and 29 trainee anaesthetists, all with basic 
knowledge of point-of-care-ultrasound (e.g. vascular access, pe-
ripheral nerve blocks). In the past several clinical studies including 
multi- as well as single-centre studies have been successfully con-
ducted at our institution. 
Statistical Considerations: 
Collected Variables 
 
Patient Demographic: Age, sex, gender, height, weight, 
BMI, ASA Classification, patient history, concomittant medi-
cation, concomitant disease, intervention performed, an-
aesthetic risk class of the intervention, surgical department 
of the intervention, urgency of the intervention. 
 
Sonographer Demographic: education level, years of 
anaestesiologic experience, years of sonographic experi-
ence 

 
Establishing routine preoperative gastric for patients with an increased aspiration risk in a Swiss teaching hospital:  
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 
risk factors for pulmonary aspiration 
 
Last meal/ drink before surgery 
 
Subjective estimated aspiration risk (graded by the respon-
sible anaesthetist)  
 
Sonography quality, reasons for poor quality 
 
Sonographic quality of gastric content 
 
Sonographic quantity of gastric content 
 
Time for examination 
 
Effective quantity of gastric content 
 
Theoretical change in anaesthesiologic management 
 
Reason for not performing gastric sonography 
 
Analyses  
 
 
Institution overall success analysis 
 
Interpersonal success analysis 
 
Analysis of theoretical changes in anaesthesiologic man-
agement 
GCP Statement: 
This study will be conducted in compliance with the study protocol, 
the current version of the Declaration of Helsinki, the ICH-GCP di-
rective, the HFG and HFV as well as all other relevant national legal 
and regulatory requirements.   

 
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Study Schedule 
 
 
Expert and Resident Train-
ing in Sonography (11/2020 
– 02/2021) 
Screening (01/2021 – 
12/2021) 
 
Prior to arrival at OR suite 
 
Day of Surgery (01/2021 – 
12/2021) 
= Day 1 
Expert (study core group, faculties) Training 
 
 
 
Anaesthesia resident Training 
 
 
 
Training Participants Demographic and Expe-
rience Data  
 
 
 
Participant Information and Informed Consent 
 
 
 
Inclusion- and Exclusion Criteria 
 
 
 
Demographic Data 
 
 
 
Medical History / Concomitant Diseases / Con-
comitant Medication 
 
 
 
Sonography and Data Collection 
 
 
 
Gastric Volume direct measurement 
 
 
 
Serious Events  
 
 
 

 
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Table of Contents 
 
Page 
1 
Abbreviations .............................................................................................................. 8 
2 
Project Personal and Administration ......................................................................... 9 
3 
Introduction ............................................................................................................... 10 
3.1 
Background and Project Purpose ................................................................................................ 10 
3.2 
Categorisation .............................................................................................................................. 11 
4 
Project Objectives ..................................................................................................... 12 
4.1 
Project Objectives ........................................................................................................................ 12 
4.2 
Project Outcomes......................................................................................................................... 12 
5 
Project Description ................................................................................................... 13 
5.1 
Design .......................................................................................................................................... 13 
5.2 
Number of Project Participants .................................................................................................... 13 
5.3 
Project Schedule .......................................................................................................................... 13 
5.4 
Risk-benefit considerations .......................................................................................................... 13 
6 
Eligibility of the Project Site ..................................................................................... 14 
7 
Recruitment ............................................................................................................... 15 
7.1 
Inclusion Criteria .......................................................................................................................... 15 
7.2 
Exclusion Criteria ......................................................................................................................... 16 
7.3 
Premature Withdrawal Criteria ..................................................................................................... 16 
8 
Project Measures ...................................................................................................... 17 
8.1 
Measures/procedures to collect health related personal data ..................................................... 17 
9 
Safety ......................................................................................................................... 19 
9.1 
Definition Serious Events ............................................................................................................. 19 
9.2 
Assessment and Documentation of SEs ..................................................................................... 19 
9.3 
Reporting of SEs .......................................................................................................................... 19 
9.4 
Reporting of Safety and Protective Measures ............................................................................. 20 
10 
Data - und Quality Management ............................................................................... 21 
11 
Statistical Plan ........................................................................................................... 22 
11.1 
Determination of Sample Size ..................................................................................................... 22 
11.2 
Statistical Methods ....................................................................................................................... 22 
12 
Ethics ......................................................................................................................... 24 
12.1 
Independent Ethics Committee .................................................................................................... 24 
12.2 
Ethical Conduct of the Project ...................................................................................................... 24 
12.3 
Participant Information and Informed Consent ............................................................................ 24 
13 
Confidentiality and Data Protection ......................................................................... 25 
14 
Funding and Support ................................................................................................ 25 
15 
Compensation ........................................................................................................... 25 
16 
Insurance ................................................................................................................... 25 
17 
Publication Policy ..................................................................................................... 26 
18 
Signatures ................................................................................................................. 27 
19 
References ................................................................................................................. 28 
 

 
Establishing routine preoperative gastric for patients with an increased aspiration risk in a Swiss teaching hospital:  
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1 
Abbreviations 
 
HFG 
HFV 
Humanforschungsgesetz 
Humanforschungsverordnung (Ordinance on human research with exception of clini-
cal trials/HRO) 
HRO 
Human Research Ordinance 
ICH 
International Conference on Harmonization 
SE 
Serious Event 
RSI 
Rapid Sequence Induction 
POCUS 
Point-of-care ultrasound 
CSA 
Cross sectional area 
SGAR 
Swiss Society for Anaesthesiology and Resuscitation 
 

 
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2 
Project Personal and Administration 
 
Sponsor 
Prof. Dr. med. Michael T. Ganter 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
+41 (0)52 266 2792 
Michael.Ganter@ksw.ch 
 
Principal Investigator: 
Dr. med. Roman Meierhans 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
+41 (0)52 266 48 46 
roman.meierhans@ksw.ch 
 
Co-Investigators: 
Dr. med. Sascha J. Bättig 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
+41 (0)52 266 38 06 
sascha.baettig@ksw.ch 
 
Dr. med. Mark G. Filipovic 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
+41 (0)52 266 49 88 
mark.filipovic@ksw.ch 
 
Daniela Widmer 
Department of Anaesthesiology 
Kantonsspital Winterthur 
Brauerstrasse 15 
8400 Winterthur, Switzerland 
+41 (0)52 266 27 92 
daniela.widmer@ksw.ch 
 
Biostatistician: 
To be determined 
 
 

 
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3 
Introduction 
 
This project plan describes the conduction of a scientific research project according HFV category A - the 
collection of health related personal data with minimal risks and burdens. 
Aspiration pneumonias still exhibit a substantial morbidity and mortality1-6 and are accountable for a signifi-
cant part of anaesthesia-related deaths.6, 7 Various diseases and especially emergency situations correlate 
with prolonged gastric emptying and therefore with a higher risk of pulmonary aspiration. 1, 4 To minimize the 
risk of aspiration, Rapid Sequence Induction (RSI) with subsequent routine placement of a oro- or nasogas-
tric tube is recognized as the anaesthesiologic procedure of choice in these situations. 16 In clinical practice 
the decision to perform a RSI is mostly based on clinical and anamnestic findings. In contrast, preoperative 
gastric sonography may provide an objective, validated, non-invasive, reliable, fast, and cost-efficient ap-
proach to assess aspiration risks in both elective and emergency patients.  
How this highly sensitive and specific tool may be best introduced and implemented in daily clinical practice 
or anaesthesiologic guidelines remains unclear. Structured educational programmes or training recommen-
dations for this point-of-care ultrasound application rarely exist. We aim to investigate the implementation of 
such a structured learning program in a teaching hospital, validating it’s effectiveness and thus lay ground to 
improve anaesthesiologic management and patient safety. 
 
3.1 
Background and Project Purpose  
 
In 1946, Mendelson8 was first to recognize the potential danger of anaesthesia related pulmonary aspiration, 
defined as the presence of bilious secretion in the tracheobronchial tree, and to describe its detrimental con-
sequences.1 The presence of intestinal fluids in the respiratory system results in a chemical pneumonitis and 
may lead to acute hypoxemia or bronchospasm or end up in an aspiration pneumonia.9 Pulmonary aspiration 
is a relatively rare event, with an incidence ranging from 0.01 up to 0.8 % according to literature.1-5, 10 Despite 
its low incidence, aspiration pneumonias may still exhibit a substantial morbidity and mortality1-6 and are ac-
countable for a significant part of anaesthesia-related deaths.6, 7 
The majority of the perioperative pulmonary aspirations occur shortly before or during laryngoscopy or through-
out extubation.1, 6 In emergency or critical care medicine the risk of pulmonary aspiration seems to be signifi-
cantly increased.10, 11 Further risk factors include gastrointestinal obstruction, recent food intake, lack of coor-
dination of swallowing, obesity, ASA status, pregnancy, age, surgical procedure and other co-morbidities (in-
sulin dependent diabetes, hepatobiliary- or renal dysfunction or cardiorespiratory diseases).1, 4 
Accordingly, strategies to reduce the risk of aspiration have been developed and continuously updated. For 
elective surgeries American12 and European13 guidelines recommend a minimum fasting time of 6 hours for 
solid an 2 hours for clear fluids. Recent guideline updates for paediatric patients resulted in a reduced fasting 
time for clear liquids of 1 hour prior to elective surgery, as prolonged fasting times had been identified as a 
negative predictor for adverse physiological response to surgery and reduced fasting intervals improved pa-
tient comfort and compliance.14, 15 
For emergency surgeries in non-fasten patients or patients with increased risk of aspiration Rapid Sequence 
Induction (RSI) is broadly accepted and executed as a standard procedure.16 However, RSI is accompanied 
by significant risks concerning haemodynamic stability and oxygenation in case intubation and mask ventilation 
fails. 17, 18 Most importantly, evidence of a decreased incidence of pulmonary aspiration after Rapid Sequence 
Induction (RSI) is still lacking.19  

 
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Fast, simple, non-invasive and cost-effective strategies to assess a patient’s risk of aspiration and adapt the 
anaesthetic strategy accordingly are greatly needed. Here, point-of-care sonography (POCUS) with preoper-
ative assessment of the gastric content allows a fundamentally new approach for patients at risk of gastric 
regurgitation by adding an objective tool - not relying on patient history alone.11, 20 Gastric sonography seems 
to be highly sensitive and specific.21, 22 Recent studies, especially highlighted the accuracy for the qualitative23-
27 and quantitative assessment22, 25, 26, 28 of the gastric content. For the quantitative analysis of gastric content, 
present data suggest a strong numerical correlation between an ultrasound-determined antral cross-sectional 
area (CSA) and the total volume of gastric fluid.11, 28 A residual gastric volume of more than 1.5 ml/kg for fluid 
content has been identified to signal an increased risk for gastrointestinal regurgitation and for pulmonary 
aspiration and this cut-off value has been utilized in various studies.20, 29 Consequently, there is an increasing 
consensus in scientific literature that preoperative gastric sonography should be performed in all emergency 
situations and in elective interventions in patients with increased probability of presenting with a full stomach 
and accordingly an increased risk of pulmonary aspiration.30-34 The routine application of gastric POCUS for 
elective surgery with fasted patients without risk factors is still controversial11 although Van de Putte et al.35 
discovered a relevant percentage of full-stomachs in patients without risk factors of delayed emptying of the 
stomach. 
In summary, preoperative gastric sonography may provide a validated, reliable, fast, and cost-efficient ap-
proach to assess aspiration risks in both elective and emergency patients. Practiced sonographers are able to 
perform point-of-care gastric sonography in few minutes11, 27 , thus severe delay in daily clinical practice should 
not be expected. Nevertheless, how this highly sensitive and specific tool should be best established in daily 
clinical practice is further on unclear. There is no existing structural education/training for this specific point-of-
care ultrasound application. Arzola et al. suggest a minimum of 30 ultrasounds an acceptable quality level, but 
evidence is scarce.36 
The aim of this investigation is to validate our structural training and proof the importance and effectiveness of 
this diagnostic tool to lay ground for improvement of anaesthesiologic management and presumably patient 
safety in patients with an increased risk of a pulmonary aspiration. 
 
3.2 
Categorisation 
Category A: collection of health related personal data is associated with minimal risk and burdens only.  
 
Gastric sonography is a very low risk examination. No ionizing radiation is used. Theoretical complications 
including sensation of local pressure or pain, regional exanthema or allergic reactions to ultrasonic gel will at 
most be very minor. The complete examination takes approximately five minutes accordingly anaesthesiologic 
and surgical procedures will not be significantly delayed. Patients and inteventions where even a minimal delay 
may pro-vide a potential health risk are not included in this study. 
 
 

 
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A prospective observational study. 
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4 
Project Objectives 
 
4.1 
Project Objectives  
 
Primary objectives: 
 
Establish preoperative gastric sonography in patients with risk factors for pulmonary aspiration at the 
Kantonsspital Winterthur, Department of Anaesthesiology through a structured training/education - 
validated by comparing sonographic estimated and directly measured gastric content. 
 
Secondary objectives: 
 
Identify possible confounders and variables in individual training. 
 
Emphasize the importance and effectiveness of this diagnostic tool to improve anaesthesiologic 
management and possibly patient safety by identifying the number of possible interventions and 
changes in anaesthesiologic management and correlation of estimated and actual gastric volume in 
fluids.  
 
4.2 
Project Outcomes 
 
Primary Endpoint: 
 
Correlation of sonographic estimated gastric volume with volume aspirated through a naso- or oro-
gastric tube, that was placed by routine. 
 
Secondary Endpoints: 
 
Performance over time, improvement of examination technique, critical number of examinations to 
achieve a high quality standard (>80% congruece for estimated and aspirated gastric volume in fluids). 
 
Association of performance with experience, residents vs. attendings. 
 
Number of patients classified as empty -> possible implications for management and induction. 
 
Number of patients with full stomach -> possible implications for management and induction. 
 
Time used for examinations, time used with growing experience. 
 
Estimated aspiration risk vs. sonographic gastric volume. 
 
Total number of pulmonary aspirations. 
 
 

 
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5 
Project Description 
 
5.1 
Design 
 
Single center, prospective observational study. No intervention groups, one single cohort. 
 
5.2 
Number of Project Participants 
 
We aim to include at least 500 up to 2200 patients. For further informations see below. 
 
5.3 
Project Schedule 
 
Estimated duration of the project:  
 
18 months 
Time period for participant recruitment:  
12 months 
Project start (FPFV): 
 
 
01/2021  
Project end (LPLV): 
 
 
12/2021 
 
5.4 
Risk-benefit considerations 
 
Gastric sonography is as an accuratly investigated and validated tool to assess a patients fasting status and 
thus probably aspiration risk. Some authors recently highlighted its possible impact on anaesthesiologic 
management in finding an appropriate technique for individual patients and thus balance risks and benefits. 
Nevertheless, gastric sonography has not yet found its role in clinical practice. This prospective observa-
tional-study with its large sample size and thorough analysis may help to identify crucial determinants and 
possible obstacals in establishing gastric sonography in daily practice and may thus contribute to patient 
safety. Further, participating medical staff benefit from a structured education in performing this examination 
with high precision and quality. 
With this study being oberservational, non interventional, all patients receive the standard of care in form of a 
predefined, independent anaesthesiologic treatment and do not carry additional risks besides possible side 
effects due to gastric sonography itself, which are minimal. The possible delay in the anaesthesiologic man-
agement ist at maximum a few minutes and patients with time critical interventions will be thoroughly ex-
cluded. In exceptional cases the responsible anaesthesiologist is allowed to upgrade patients from an ad-
vanced laryngeal mask to a RSI (gold standard) after ultrasound performance to ensure patient safety. 
Downgrading from RSI to advanced laryngeal maks on base of the ultrasound results is not allowed. 
  

 
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6 
Eligibility of the Project Site 
 
This study will be conducted at the Department of Anaesthesiology at the Cantonal Hospital of Winterthur, a 
Swiss teaching hospital. In our department we care for a total of approximately 18’000 patients a year. The 
anaesthesiologic physician team consists of 25 qualified/staff anaesthetists and 29 trainee anaesthetists. In 
the past several clinical studies including multi- as well as single-center studies have been successfully con-
ducted at our institution. Commulative experience of the assigned staff are high: They have participated in 
several observational studies as well as interventional studies and Phase III trials. An experienced study co-
ordination team is available at site and involved in coordination and planning. 
 
 

 
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7 
Recruitment 
 
Within a study period of 6 to 12 months, all elective and emergency patients with one or more risk factors for 
pulmonary aspiratipon will be screend for possible participation in this study. The risk factors for pulmonary 
aspiration are previously determined by the responsible anaesthetist and based on patient medical history 
and clinical findings according to department standards. With the given information and in line with depart-
ment policy, the responsible anaesthesiologist will predefine an individual management for the patient, in 
form of an advanced laryngeal mask, a RSI or a regional anaesthesia. No changes in or adaptions of the es-
tablished clinical practice will be made for the sole purpose of this study. 
The responsible anaesthesiologist will work through the list of inclusion and exclusion criteria. Of note, pa-
tients which are of the highest urgency where a delay is medically and ethically not acceptable, will not be 
included in this study. Also, patients where ability to consent is not given due to patient or circumstantial rea-
sons, will be excluded. 
Thereafter, further recruitment and informed consent will be obtained during a regular anaesthesia specific 
discussion, which can take place on the ward, in our preoperative consultation for elective surgery or the 
emergency department. If a patient qualifies for this study according to our inclusion criterias, a qualified 
studyperson will explain the nature of the study to each participant, its purpose, the procedures involved, the 
expected duration, the potential risks and benefits and any discomfort it may entail, according to good clinical 
practice guidelines. Members of the department of anaesthesia will receive a training by the PI and investi-
gators prior to appointment as qualified studyperson with delegated informed consent authorization. Each 
participant will be informed that the participation in the study is voluntary and that he/she may withdraw from 
the study at any time and that withdrawal of consent will not affect his/her subsequent medical assistance 
and treatment. 
After the discussion, an additional information brochure and consent form will be handed to all possible par-
ticipants providing sufficient information to make an informed decision. The patient will be asked to carefully 
read and review the form, clarify possible questions at any time and sufficient time will be provided before 
signing. After the participants signature, the form will also be dated and signed by the study person and re-
tained as part of the study records. If the patient needs further time for consideration the patient may sign the 
informed consent togheter with the responsible anaesthesist on the day of surgery, after a overnight reflec-
tion period. If unanswered questions arise or the patient need further clarifications a special appointment with 
a physican of the study team is available anytime. The participant will receive a copy of the signed informed 
consent.  
The participant will be informed that his/her medical records may be examined by authorised individuals 
other than their treating physician. 
 
7.1 
Inclusion Criteria 
 
Subjects, who will fulfil all the following inclusion criteria, may be included into this project: 
 
All elective in-hospital Rapid Sequence Inductions (RSI) and patients with one or more aspiration 
risk factors scheduled for an advanced laryngeal mask or regional anaesthesia with informed con-
sent. 

 
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 
All emergency in-hospital RSI and patients with one or more aspiration risk factors scheduled for an 
advanced laryngeal mask or regional anaesthesia with informed consent graded as follows accord-
ing to the Swiss Society for Anaesthesiology and Resuscitation (A-QUA): “Notfall 1-6h, nicht vital 
(dringlicher Eingriff)”, “Notfall 6-24h nicht vital (aufgeschobener dringlicher Eingriff)” 
 
7.2 
Exclusion Criteria 
 
If a subject fulfils any of the following exclusion criteria he/she may not be included: 
 
Life threatening/ time critical emergency interventions, graded followingly according to the Swiss So-
ciety for Anaesthesiology and Resuscitation (A-QUA): Notfall <1h, vital (sofortiger Eingriff notwendig) 
 
Known pregnancy 
 
Obstetric surgery 
 
Underage (< 18 years) 
 
Absence of informed consent (missing or inability to provide) 
 
No anaesthetist with completed structural education is available. 
 
Contraindications for naso- or orogastric tubes or inability to correctly place such. 
 
7.3 
Premature Withdrawal Criteria  
 
Premature withdrawal of a participant: 
 
Participants may withdrawal their informed consent at anytime. If gastric sonography has already been 
performed, anonymous analysis of the previously collected data is eligible. 
 
Discomfort of pain experienced by the patient at any time of the sonography. 
 
In case of unability to safely perform the sonography within a maximum of 10 minutes, futher attempts 
will be stopped and the patient excluded. 
 
Arising medical or personal information at any time, increasing the urgency of the intervention. 
 
Premature termination of the project: 
As this study is designed in a observational, non-interventional methodology, and all patients receive the stand-
ard of treatment , no premature termination should occur.  
 

 
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8 
Project Measures  
 
8.1 
Measures/procedures to collect health related personal data  
 
At Kantosspital Winterthur, a mid-size Swiss teaching hospital all residents and attending anaesthesiologists 
will receive a structured training in a period of 1 to 8 weeks before inclusion of the first patient. All participat-
ing staff will give written informed consent to participate in the study.  
To achieve a 90% success rate in correctly recognizing gastric content quality in healthy volunteers, Arzola 
et al.36 postulated an average number of 24 sonographic examinations to be performed. Based on this and 
further scientific studies we designed a structured training for all residents and fellows. Primarily, at least 120 
minutes of self-study is mandatory for all participants, consisting of scientific background literature, a step for 
step guide and educational videos. This is followed by a hands-on course, split into a 30 minute lecture and 
theoretic background introduction and 120 minutes supervised practical training on healthy volunteers. 
Group sizes per ultrasound machine and tutor/expert will range from 2 to 3 participants. First training objec-
tive is a successful differentiation of gastric content into empty, fluid, solid or mixed. An empty stomach 
seems the hardest quality to sonographically visualise, 36 therefore a special effort will be made on identify-
ing this quality. The next objective is the identification and localization of the antral cross-sectional area in a 
supine and right lateral decubitus (RLD) position in the case that fluid gastric content is present. Every partic-
ipant will perform at least 20 examinations during this hands-on course with a direct expert feedback.  
Further, all participants will continue to train their sonographic skills on healthy volunteers and team mem-
bers at our institution. Before including the first patient all the examiners will be tested by a tutor/expert and 
received their approval. In the first month of recruitment, new sonographers will be supervised by our tu-
tor/expert team whenever possible. Individual feedback and support if needed should be available any time. 
Tutors/experts are all expert sonographers on different modalities. They will receive a preceding 240 minutes 
training, consisting of a 60 minutes theoretic introduction and a 60 minutes course by a radiologist and ab-
dominal sonography expert, certified by the Swiss Society for Sonography. The remaining time will consist of 
individual exercise on healthy volunteers and at least 10 trial sonographies with gastric volume calculation 
under supervision of another member of the tutor group.  
Our study will be performed mainly in the induction rooms of our operating unit and occasionally inside the 
operating theatre. Standard care will be given to every patient at the usual location, with our usual equipment 
(anaesthetic machine, monitoring, medication and airway devices and so on) and by our usual anaesthesio-
logic team members. Sonographic examination and determination of the gastric content will be executed on 
one of our standard ultrasound machines (Venue and LOQIC e from GE-Healthcare®) with a curved array 
low frequency (2-10 Hz) abdominal probe or our portable ultrasound devices (IQ+ from Butterfly Network Inc. 
®). 
Before performing the sonographic examination, the responsible anaesthesiologist will be asked to rate the 
estimated risk of pulmonary aspiration, based on personal impression, patient history and clinical finding. All 
anaesthetists are advised to perform the examination only if they could guarantee privacy before they ex-
pose patient abdomen for the examination. Primary, a qualitative assessment of the gastric content should 
be performed in supine and right-lateral decubitus (RLD) position. In low volume states a right-lateral decubi-
tus position (RLD) has the advantage of a gravitational shift to the antrum. That is why we plan to perform 
the examination in both positions. If RLD position is not possible due to patient factors a half sitting position 
can be tried. Gastric content will be classified into empty, fluid, solid or mixed. Examiners will be asked to 
classify sonographic conditions into poor, medium or good and provide a reason in case of limited condi-
tions. If fluid gastric content is detected an estimation of the quantity should be performed as follows.  

 
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After identification, CSA will be measured and gastric content is estimated by implementation of the formula 
described by Perlas et al: 20, 28 
 Gastric Volume (ml) = 27.0 + 14.6 × right-lateral CSA (cm2) − 1.28 × age (years). 
This model is based on gastroscopic fluid assessment and highly validated by several publications. 28 
After placement of the routine naso- or orogastric tube, which is a standard procedure  for both RSIs and ad-
vanced laryngeal masksat our institution - we compare the calculated and effective suctioned volume of the 
gastric content and analyse the difference and quality of the sonographic measurement. In some patient a 
gastric tube is contraindicated or not possible to place correctly. In this case an exclusion of the study is 
mandatory according to our exclusion criteria. Patients planed for an intervention in a regional anaesthesia 
will not receive a gastric tube. 
In exceptional cases the responsible anaesthesiologist is allowed to upgrade patients from an advanced lar-
yngeal mask to an RSI after ultrasound performance to ensure patient safety. Downgrading from RSI to ad-
vanced laryngeal maks on base of the ultrasound results is not allowed. 
All data concerning the sonography will be noted in a password protected Excel sheet only available to insti-
tute members by the responsible anaesthesiologist performing the excamination. Background patient data 
including demographic data are collected during the structured preoperative anaesthesiologic assessment 
according to in house standard procedures and data management. Data will be coded and condensed in a 
password-protected Excel File, only accessible to study personel. A patient identification log will be kept in a 
locked archive for data verification processes only. To guarantee seamless traceability we will create a im-
mutable PDF file after all relevant changes or at least once per month and store it in a separate study folder 
only accessible to study personel. An additional hard copy will be created and printed once per month and 
stored in a locker in our administrative office. 
 
 

 
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9 
Safety 
 
9.1 
Definition Serious Events 
 
A serious event (SE) according to HFV Art. 21 is any unfavorable event for which a causal relationship the 
collection of health related personal data cannot be ruled out, and which:   
 
Requires hospitalization or prolongation of an inpatients’ hospitalization, 
 
results in persistent or significant disability or incapacity, oris life-threatening or results in death 
If a serious event occurs the research project must to be set on hold. 
9.2 
Assessment and Documentation of SEs 
 
 
The assessment by the project leader regarding the causal relationship of the event to the project-specific 
measure is done according to the following definitions:  
 
Unrelated 
 
The event started in no temporal relationship to the project-specific 
measures applied and 
 
The event can be definitely explained by underlying diseases or other situa-
tions. 
Related 
 
 
The event started in plausible time relationship to the project-specific 
measures applied and 
 
The event cannot be definitely explained by underlying diseases or other sit-
uations. 
 
All SEs are to be documented in the subjects´ file and on the SE report form. 
 
9.3 
Reporting of SEs 
 
SEs will be treated according to the Human Research Ordinance (HFV Art. 21). First, the project leader will 
report any occurring SE to the responsible ethics committee within 7 days. He will also submit a report which 
evaluates the relationship between the event reported and the methods of collecting health related personal 
data or sampling of biological material within that project, furthermore proposals how to proceed with the pro-
ject. 
 
 
 
 

 
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9.4 
Reporting of Safety and Protective Measures 
 
The project leader shall notify any immediate safety and protective measures, which have to be taken during 
the conduct of the research project, the ethics committee within 7 days according to the HFV Art. 20. In addi-
tion, the project leader explains the circumstances which necessitated the safety and protective measures.  
 
 

 
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10 
Data - und Quality Management 
 
 
The principal investigator and the whole study team affirm to uphold the principles of the participant's right to 
privacy and that they shall comply with applicable privacy laws. Especially, anonymity of the participants will 
be guaranteed when presenting the data at scientific meetings or publishing them in scientific journals. Indi-
vidual subject medical information obtained as a result of this study is considered confidential and disclosure 
to third parties is prohibited. Subject confidentiality will be further ensured by utilising subject identification 
code numbers to correspond to treatment data in the computer files. For data verification purposes, author-
ised representatives of the Sponsor (-Investigator)or an ethics committee may require direct access to parts 
of the medical records relevant to the study, including participants’ medical history. 
A good-clinical-practice educated member of the study team is responsible for proper, coded and correct 
data management. All patient related electronic data is stored coded in a password-protected folder on our 
institution server. Only dedicated study personel have access. All physical data and patient informed consent 
is stored in a locked folder at our institution’s secretariat. Data storage is only performed in coded form for 
peer-review. For further informations also see Chapter 8. 
 
 

 
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11 
Statistical Plan  
 
11.1 
Determination of Sample Size 
 
Within a study period of 6 to 12 months, all elective and emergency patients scheduled for a Rapid Se-
quence Induction (RSI) will be included in this study. In 2019, a total of 2’718 general anaesthesias with 
Rapid Sequence Inductions (RSI) were undertaken at our institution. 275 thereof were children < 18 years of 
age. Further, 204 Rapid Sequence Inductions were performed in life threatening situations (category: Notfall 
<1h, vital, sofortiger Eingriff notwendig by the Swiss Society for Anaesthesiology and Resuscitation, A-QUA) 
where a delay is medically and ethically not acceptable. Further, we estimate that a number of 1000 patients 
per annum have one or more aspiration risk factors, receiving an advanced laryngeal mask or a regional an-
aesthesia. In conclusion, we aim to include at least 1500 up to 3200 patients in a one year recruitment pe-
riod. On basis of the publication of Arzola et al. 36 individual differences in sonography performance can al-
ready be detected after 30 to 40 examinations. Although our residents will already have perfomed at least 
asmany examinations before first patient inclusion, we postulate, that a similar number of patients per capita 
will be needed to investigate interindividual performance. Given an estimated number of 30 residents and 20 
attendings participating, we aim to include 1500 - 2000 patients. 
 
11.2 
Statistical Methods 
 
Primary Endpoint: 
 
Correlation of sonographic estimated gastric volume with volume aspirated through a naso- or orgas-
tric tube. 
 
Secondary Endpoints: 
 
Performance over time (improvement of examination technique, critical number of examinations). 
 
Association of performance with experience, residents vs. attendings. 
 
Number of patients classified as empty -> possible implications for management and induction. 
 
Number of patients with full stomach -> possible implications for management and induction. 
 
Time used for examinations, time used with growing experience. 
 
estimated aspiration risk vs. sonographic gastric volume. 
 
Total number of pulmonary aspirations. 
 
Collected Variables: 
 
Patient Demographic: Age, sex, gender, height, weight, BMI, ASA Classification, patient history, con-
comittant medication, concomitant disease, intervention performed, anaesthetic risk class of the in-
tervention, surgical department of the intervention, urgency of the intervention. 
 
Sonographer Demographic: education level, years of anaestesiologic experience, years of so-
nographic experience. 
 
RSI Indication. 
 
Last meal/ drink before surgery. 
 
Subjective estimated aspiration risk (graded by the responsible anaesthetist). 
 
Sonography quality, reasons for poor quality. 

 
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 
Sonographic quality of gastric content. 
 
Sonographic quantity of gastric content. 
 
Time for examination. 
 
Effective quantity of gastric content. 
 
Theoretical change in anaesthesiologic management. 
 
Reason for not performing gastric sonography. 
 
Analysis: 
 
Demographic Analysis. 
 
Institution overall success analysis. 
 
Interpersonal success analysis with logistic regression an cumulative sum learning curves. 
 
Analysis of possible changes in anaesthesiologic management. 
 
 
 

 
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12 
Ethics 
 
12.1 Independent Ethics Committee 
 
Before this project will be conducted, the protocol, the proposed participant information and consent form as 
well as other project-specific documents will be submitted to a properly constituted Competent Ethics Commit-
tee (CEC), for formal approval. The decision of the CEC concerning the conduct of the project will be made in 
writing to the Sponsor-Project Leader before commencement of this project. 
Significant changes to an authorised research project must be approved by the ethics committee before being 
implemented. Exempt from this requirement are measures which have to be taken immediately in order to 
protect the participants. 
 
The following are considered to be significant changes: 
a. changes affecting the participants’ safety and health, or their rights and obligations; 
b. a change of research site or conducting the research project at an additional site; or 
c. a change of the project leader or sponsor. 
The Ethics Committee will be informed within 90 days regarding the termination or completion of the project. 
 
12.2 Ethical Conduct of the Project 
 
This project will be carried out in accordance with principles enunciated in the current version of the Declaration 
of Helsinki and Swiss regulatory authority’s requirements.  
 
12.3 Participant Information and Informed Consent 
 
Prior to the project start each participant has to give their written informed consent after he/she was compre-
hensively informed - verbally and in writing - on the nature, relevance and impact of the project. The content 
of this information should be documented on the informed consent. Each participant must be informed that the 
participation in the project is voluntary and that he/she may withdraw from the project at any time and that 
withdrawal of consent will not affect his/her subsequent medical treatment. The participants will be given 
enough time to make their decision whether they would like to participate or not. 
The consent to participate into the research project should be signed and dated by both, the participant andthe 
project leader or a trained study person.  A copy of the signed and dated subject information and informed 
consent form has to be handed out to the participant. 
No project related procedures are to be conducted before a legally accepted written informed consent has 
been given. 
 
 

 
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13 Confidentiality and Data Protection 
 
Data generation, transmission, archiving and analysis of health related personal data within this project; strictly 
follow the current Swiss legal requirements for data protection and according to the Ordinance HFV Art. 5. 
Prerequisite is the voluntary approval of the participant given by signing the informed consent prior start of 
participation of the research project.  
Health related personal data captured during this project from participants are strictly confidential and disclo-
sure to third parties is prohibited; coding will safeguard participants' confidentiality. Confidentiality will be en-
sured by using coded data. The code will be protected against unauthorized access and will be stored appro-
priately by the project leader. All patient related date will be destroyed after project termination.  
The collected project data may be subject to inspection by the CEC. 
14 Funding and Support 
 
No external funding. 
 
15 Compensation 
 
Participants will not be compensated for their participation into this scientific research project. 
 
16 Insurance 
 
Insurance is covered by “Versicherung für klinische Versuche und nichtklinische Versuche“ by Basler Versi-
cherung AG (Policy no.: 30/4.093.845). 
Any damage developed during the course of the project is covered by this insurance. So as not to forfeit their 
insurance cover, the participants themselves must strictly follow the instructions of the project personal. Med-
ical emergency treatment must be reported immediately to the project leader. The project leader must also be 
informed instantly, in the event of health problems or other damages during or after the course of project. 
The project leader will allow delegates of the insurance company to have access to the source data/documents 
as necessary to clarify a case of damage related to project participation. All involved parties will keep the 
subjects’ data strictly confidential. 
 
 
 
 

 
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17 Publication Policy 
 
After the statistical analysis of this trial the sponsor and principal investigator will make every endeavor to 
publish the data in a medical journal. 
 

 
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18 
Signatures  
 
The following persons agree with the content of this project by signing this project plan. Changes concerning 
the responsibilities of every person signing this project plan need to be announced immediately. 
 
 
Sponsor  
This protocol V3.0, 25.01.2021 was subject to critical review and has been approved by the Sponsor-Project 
Leader. The information herein is consistent with the current risk/benefit assessment and the moral, ethical 
and scientific principles governing clinical research as set out in the current version of the Declaration of Hel-
sinki.  
 
Prof Dr. med. Michael Ganter 
 
____________________________________       _________________________________ 
Place, Date  
 
 
Signature 
 
 
Sponsor - Project Leader 
This protocol V3.0, 25.01.2021 was subject to critical review and has been approved by the Sponsor-Project 
Leader. The information herein is consistent with the current risk/benefit assessment and the moral, ethical 
and scientific principles governing clinical research as set out in the current version of the Declaration of Hel-
sinki.  
 
Dr. med. Roman Meierhans 
 
____________________________________       _________________________________ 
Place, Date  
 
 
Signature 
  
 
 
 

 
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19 
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