Preoperative Evaluation of IVC Collapsibility Index and Caval Aorta Index for Prediction of Hypotension After Induction of General Anesthesia in Patients Undergoing Craniotomy Surgeries
Conditions: Inferior Vena Cava, Collapsibility Index, Caval Aorta Index, Induction, General Anesthesia, Craniotomy
Sponsor: Ain Shams University

 
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Protocol of a Thesis for Partial Fulfillment of M.D. degree in Anesthesia 
 
Title: 
Preoperative Evaluation of IVC Collapsibility Index and Caval Aorta Index for 
Prediction of Hypotension after Induction of General Anesthesia in patients 
Undergoing Craniotomy Surgeries 
 
Postgraduate Student:  
Verina Fares Zaref Bekheet 
Degree: M.B.B.CH- assistant-lecturer in department of Anesthesia, Intensive Care and Pain 
Management- Faculty of Medicine -Ain Shams University   
 
Supervisor:  
Prof. Dr. Sherif Wadie Nashed Sarguios  
Academic Position: Professor of Anesthesia, Intensive Care and Pain Management   
  
Department:  
Anesthesia, Intensive Care and Pain Management - Faculty of  
Medicine Ain Shams University   
 
Co- Supervisor:     Ass.Prof. Dr. Dalia Ahmed Ibrahim Mohamed 
Academic position: 
Assistant Professor of Anesthesia, Intensive Care and Pain Management   
Department:  
Anesthesia, Intensive Care and Pain Management - Faculty of  
Medicine Ain Shams University   
 
 
Co- Supervisor:  
 Dr. Noha Mohammed Abdel-Aziz EL-Tobgy 
Academic position: 
lecturer of Anesthesia, Intensive Care and Pain Management   
Department:  
Anesthesia, Intensive Care and Pain Management - Faculty of  
Medicine Ain Shams University   
 
 
Co- Supervisor: 
Dr. Mai Mohamed Othman Elhefny 
Academic Position: lecturer of Anesthesia, Intensive Care and Pain Management   
Department:  
Anesthesia, Intensive Care and Pain Management - Faculty of  
Medicine Ain Shams University   
 
Faculty of Medicine  
Ain Shams University 
2023 
 
 

 
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What is already known on this subject? AND          
What does this study add? 
Intraoperative hypotension has been the most frequent side effect after 
anesthesia, with an incidence of 15.3% to 33%. Hypotension can be severe 
(incidence 5.4%) and may cause systemic hypoperfusion and ischemic events.       ( 
Jor, O., Maca J., Koutna J., et al.2018) 
The caval aorta index (IVC/Ao) compares the maximum diameter of the IVC 
with the abdominal aorta (Ao).  
This study is to assess the accuracy, repeatability, and reproducibility of 
preoperative evaluation of IVC Collapsibility Index and Caval Aorta Index for 
prediction of hypotension after induction of general anesthesia. 
1.INTRODUCTION 
Post- anesthesia hypotension is of common occurrence, and it hampers tissue 
perfusion. The magnitude of hypotension is determined by the preoperative 
volume status, which varies depending on ASA physical status, preoperative 
comorbidities, preoperative medications, and fasting. (Bajawa S, Jindal R , 
Kulsherestha A. 2013) 
Intraoperative hypotension may solely be responsible for unfavorable 
consequences during or after surgery, including myocardial infarction, stroke, 
acute kidney injury, extended hospital stay, and higher death rates after one year in 
both cardiac and non-cardiac operations. (Monk TG , Saini V , Weldon BC , et 
al . 2005) 
General anesthesia causes significant alterations in hemodynamics, as both 
inhalational and intravenous anesthetics cause bradycardia, decrease in systemic 
vascular resistance and vasodilatation, and decrease in myocardial contractility, 
cardiac output and stroke volume, with the absence of surgical stimulus, making 
induction of anesthesia is the most crucial period at which hypotension occurs. 
There are non-modifiable factors for post general anesthesia hypotension as ASA 
III & IV, old age, and the inevitable use of propofol and fentanyl, however there 
are modifiable factors and preoperative intravascular volume is one of the most 
important of them. (Kouz K , Hoppe P , Briesenick L , et al , 2020) 
There is no uniform definition for intra-operative hypotension. It even remains 
unknown whether intra-operative hypotension should be defined based on absolute 
arterial pressure thresholds or on relative thresholds considering a decrease from 

 
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baseline arterial pressure. Frequently used definitions include systolic arterial 
pressure below 80 mmHg, a decrease in systolic arterial pressure of more than 20% 
below baseline, and a combination of definitions consisting of an absolute SAP 
below 100 mmHg and/or 30% decrease below baseline.( Saugel B , Reuter DA, 
Reese PC , 2017). 
Due to different definitions of hypotension and diverse patient populations, the 
effect of volume preload on prevention of hypotension is still controversial. Many 
recommendations to identified sonographic determination of inferior vena cava 
(IVC) collapsibility index (IVCCI) as non-invasive, and easy technique for 
evaluating volume status. Recent guidelines from the American Society of 
Echocardiography support the general use of IVCCI in assessing volume 
status.(Dipti A , Soucy Z , Surana A, et al 2017) 
The etiology of intra-operative hypotension is multifactorial. Intra-operative 
hypotension can, among other factors, be caused by vasodilation (anaesthetic 
drugs, systemic inflammation), intravascular hypovolaemia (bleeding), low 
cardiac output (bradycardia or low stroke volume), high intra-thoracic pressure 
(mechanical ventilation), impairment of sympathetic nervous system or 
compromised baroreflex regulation. (Kouz K , Hoppe P , Briesenick L , et al , 
2020). 
With some individual variation, autoregulation of cerebral blood flow  (CBF) 
typically occurs within a mean arterial pressure( MAP) range of 60 to 150 mmHg 
. Outside of this range, the brain is unable to compensate for changes in perfusion 
pressure, and thecerebral blood flow (CBF) increases or decreases passively with 
corresponding changes in pressure, resulting in the risk of ischemia at low 
pressures and edema or hemorrhage at high pressures. We aim for a MAP above 
the lower limit of autoregulation.(Lassen NA.) 
 
 
 
 
 
 
 
 
 
 

 
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2.AIM /OBJECTIVES  
 Primary aim: Assessment of the accuracy, repeatability, and reproducibility of 
preoperative evaluation of IVC collapsibility index and Caval Aorta Index for 
prediction of hypotension after induction of general anesthesia. 
 Secondary aim: to compare values of both IVCCI and Aorto-Caval Index in 
prediction of post general anesthesia induction hypotension. 
 
3.METHODOLOGY: 
Subjects and Methods 
 Type of Study:  Prospective cohort study. 
 Study Setting: the study will be conducted at Ain-Shams University Hospitals. 
 Study Period: the study will take place till reaching the target sample size. 
 Study Population: 
Selection criteria: 
Inclusion Criteria: 
 Patients aging 18-40 years. 
 BMI < 40 kg/m². 
 ASA I, II. 
 Fasted according to the ASA guidelines: 2 hours for clear fluids, 6 
hours after light meal, 8 hours after a full meal with high calorie or fat 
content. 
 Scheduled for elective craniotomy surgeries before induction of 
general anesthesia. 
 
- Exclusion Criteria: 
 Patients < 18 or >40 years. 
 BMI > 40 kg/m². 
 ASA III, IV. 
 Current or recent pregnancy (within 3 months). 
 Pre-existing cardiac disease or hypertension. 
 On medications affecting blood pressure (BBs, CCBs,..) . 
 Refusing to undergo the study. 
 

 
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 Sample Size Calculation: 
Using PASS 11 program for sample size calculation ; setting power at 80% , 
error at 5%, incidence of hypotension among patients undergoing general 
anesthesia at 78.43% (Omar et al.,2023), and sensitivity and specificity of 
ultrasound guided Aorto-Caval index (IVC-AO) for prediction post general 
anesthesia hypotension at 77.5% and 63.6% , respectively, (Omar et al.,2023) , 
so a sample size of 32 patients undergoing craniotomy surgeries under general 
anesthesia will be needed. 
Assuming that a drop out is of 10% , a sample size of at least 36 patients 
undergoing craniotomy surgeries under general anesthesia will be needed. 
 
 Ethical Consideration: 
-Approval from the research Ethics committee of faculty of medicine ,Ain shams 
university is mandatory and will be obtained before start in this study. 
-Obtaining an informed consent: Written signed and dated informed consent will be 
obtained from patients or legal guardian of each participant before being entered 
into the study. 
-Patients can withdraw from the study at any time and still get the full medical 
service within the facility. patients can refuse to participate and still get the 
standard care. 
-Patients, privacy and confidentiality with the right to know the research results are 
ensured. 
 
 Sample size: 40 cases 
 Study Tools: Ultrasound curvilinear array, low - frequency (2- 5 MHz) 
 Study Procedure 
Pre-operative: All patients will be subjected to: 
1- Detailed medical history taking with special emphasis on: 
- History of cardiac disease or anti-hypertensive medications. 
- Demographic data (age, sex, weight, height, body mass index). 
2- Thorough clinical examination including: 
- General and local examination. 
- American Society of Anesthesiologists (ASA) physical status classification. 
3- Laboratory investigations: 
o Complete blood picture (CBC). 
o Prothrombin time (PT), INR and activated partial thromboplastin time 
(aPTT). 

 
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o Liver functions tests. 
o Cardiac enzymes. 
o Kidney function tests. 
4- Electrocardiogram (ECG). 
 
Intra-operative: 
-On the day of surgery, pre-operative fasting for 8 hours will be 
confirmed. 
- Upon arrival to the operating room, routine monitors in the form of pulse 
oximetry, electro-cardiogram and non-invasive blood pressure monitors 
will be applied. Intravenous line will be secured. 
- central venous line and invasive arterial line will be applied. 
- Systolic blood pressure, diastolic blood pressure, MAP, and HR at 
baseline will be recorded. 
- After obtaining informed consent, the patient is placed in the supine 
position with the head of the bed elevated 30 degrees. 
 
- The ultrasound transducer is placed in the right subcostal position to 
visualize the IVC. 
- The maximum (expiratory) and minimum (inspiratory) IVC diameters 
are measured. 
- The IVCCI is calculated using the following formula: 
 
IVCCI = (maximum IVC diameter - minimum IVC diameter) / maximum 
IVC diameter * 100 
 
- To the left of the IVC, the abdominal aorta is visualized 10 mm above 
the coeliac trunk. 
- The aortic diameter is measured at maximum diameter during systole 
- The IVC : Ao index will be derived by taking the ratio of the maximum 
IVC diameter during expiration and the maximal abdominal aortic 
diameter during systole. 
- The IVC/Ao index is calculated using the following formula: 
 
IVC/Ao index = IVC diameter / aortic diameter. 
- The measurements are repeated three times and the average is 
calculated.(Finnerty NM, Panchal AR , Boulger C, et al 2017) 
 
- The patients will be induced as per a standard protocol. They will be 
given midazolam 0.05–0.1 mg.kg − 1, and fentanyl 2–3 μg.kg − 1 before 

 
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induction. Patients will be induced with propofol 1–2 mg.kg − 1, till loss of 
response to verbal commands. They will then mask ventilated with 100% 
oxygen and isoflurane 1.0%–1.2%. Atracurium (0.5 mg.kg − 1) will be 
given for muscle relaxation. Three minutes after atracurium, patients will 
be intubated by performing a gentle and quick laryngoscopy lasting not 
more than 15 s. In males, 8 mm or 8.5 mm internal diameter endotracheal 
tube will be used. In females, 7 mm or 7.5 mm internal diameter 
endotracheal tube will be used.(Chowdhury SR, Datta PK, Maitra S, et 
al ,2023) 
 
- Measurement tools - Mean arterial blood pressure will be measured in 
supine position in one of the upper limbs in the operating room at 1-minute 
intervals starting from the baseline preoperative reading until skin incision 
as follows: 1-minute post-induction reading, 2-minutes post-induction 
reading, pre-intubation reading & post-intubation readings until skin 
incision. Taking in consideration that the maximum time for recording the 
readings of the blood pressure is 15 minutes because if hypotension occurred 
after this time it is unlikely to be due to the effect of induction of anesthesia. 
- Heart rate will be recorded at 1-minute intervals starting from the baseline 
pre-operative reading until skin incision as follows: 1-minute post-induction 
reading, 2-minutes post-induction reading, pre-intubation reading & post-
intubation readings until skin incision. Any episode of hypotension (defined 
as mean arterial pressure < 80% of the baseline reading or or MAP less than 
60 mmHg) will be managed by ephedrine 5 mg every 2 min to increase SBP 
to 80% of the baseline or MAP more than 70 mmHg. If the hypotensive 
episode persisted for 2 minutes, another bolus of norepinephrine will be 
administered.  
 
 
- The strength of the association between different parameters and post-
anesthesia hypotension was calculated. To find out the value of the optimal 
cut-off for the prediction of post-anesthesia hypotension. 
 
 Statistical Method: 
Data collection: Demographic, clinical data, investigations, imaging, ECG 
and echocardiographic data will be obtained and recorded in special 
registration form. 
 
Statistical analysis: 
Statistical data will be tabulated, and Statistical analysis is to be performed 
using the latest available version of SPSS. 

 
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4.REFERENCES:  
 
1. Bajwa S, Jindal R, Kulshrestha A. (2013).Co-loading or preloading for 
prevention of hypotension after spinal anesthesia! a therapeutic dilemma. 
Anesthesia Essays and Researches 7:155–159. 
 
2. Chowdhury SR, Datta PK, Maitra S.et al (2023) The use of preoperative 
inferior vena cava ultrasound to predict anaesthesia-induced hypotension: 
a systematic review. Anaesthesiology Intensive Therapy ;55(1):18-31.  
 
3. Dipti A, Soucy Z, Surana A, et al. (2012).Role of inferior vena cava 
diameter in assessment of volume status: a meta-analysis. American 
Journal of Emergency Medicine.  
 
4. Finnerty NM, Panchal AR, Boulger C. et al.(2017) Inferior Vena Cava 
Measurement with Ultrasound: What Is the Best View and Best Mode? 
Western Journal of Emergency Medicine. 
 
5. Kouz K, Hoppe P, Briesenick L, et al.(2020). Intraoperative hypotension. 
Pathophysiology, clinical relevance, and therapeutic approaches. Indian 
Journal of Anesthesia 64(2):90. 
 
6. LASSEN NA. Cerebral blood flow and oxygen consumption in man. 
Physiology Rev. 1959 Apr;39(2):183-238. 
 
7. Monk TG, Saini V, Weldon BC, et al. (2005).Anesthetic management and 
one-year mortality after noncardiac surgery. Anesthesia Analgesia;100:4–
10. 
 
 
8. Omar H ,Moamen A, Abdelhamid BM , et al (2023) . Accuracy of 
preoperative evaluation of inferior vena cava collapsibility index and caval 
aorta index for prediction of hypotension after induction of general 
anesthesia. 
 
9. Saugel B, Reuter DA, Reese PC.(2017). Intraoperative mean arterial 
pressure targets: Can databases give us a universally valid “magic number” 
or does physiology still apply for the individual patient? 
Anesthesiology;127:725–6. 
 

 
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10. Jor, O., Maca, J., Koutna, J. et al.(2018) Hypotension after induction of 
general anesthesia: occurrence, risk factors, and therapy. A prospective 
multicentre observational study. Journal of Anesthesia 32, 673–680 .