Comparison of Changes in Total Oxidant and Total Antioxidant Capacities in Low-Flow and High-Flow General Anesthesia Protocols
Conditions: Oxidative Stress, Anesthesia
Sponsor: Duzce University

 
 
 
REPUBLIC OF TÜRKİYE 
DUZCE UNIVERSITY 
FACULTY OF MEDICINE 
DEPARTMENT OF ANESTHESIOLOGY AND REANIMATION 
 
 
Comparison of Changes in Total Oxidant and Total Antioxidant Capacities 
in Low-Flow and High-Flow General Anesthesia Protocols: Study Protocol 
(NCT05590312) 
 
 
 
 
 
DUZCE-2022 
(Translation in English: 16.01.2025) 
 
 
 
 
 
Comparison of Changes in Total Oxidant and Total Antioxidant Capacities in Low-Flow 
and High-Flow General Anesthesia Protocols  

 
General Information/ Background 
General anesthesia is a complex physiological state characterized by reversible loss of 
consciousness, whole-body analgesia, amnesia, and muscle relaxation. The term low-flow 
anesthesia describes inhalation anesthesia techniques that are administered with a semi-closed 
rebreathing system and have a rebreathing rate of at least 50%. The high standard of anesthesia 
machines, the existence of monitors that analyze the anesthetic gas composition continuously 
and in detail, and the increased knowledge about the pharmacodynamics and pharmacokinetics 
of inhalation anesthetics have greatly facilitated the safe administration of low-flow anesthesia. 
The terminology associated with low-flow anesthetic techniques may be based on rebreathing 
or fresh gas flow rates. The fresh gas flow rate is the most critical factor determining the 
rebreathing rate. Most patients can have low-flow anesthesia when modern re-breathing 
systems are used; the fresh gas flow rate is reduced to less than 2 L/min. Oxidative stress is 
accepted as a pathological mechanism. Oxidative stress is a state of oxidative damage that 
occurs when the critical balance between free radical production and antioxidant defense 
systems is disrupted. Oxidative stress is beneficial in certain physiological conditions. For 
example, it can strengthen biological defense mechanisms during appropriate physical exercise 
and ischemia. However, its benefits are limited to these specific situations, and in many other 
cases, high levels of oxidative stress cause cell death and, thus, cell and tissue damage through 
necrotic or apoptotic mechanisms. If damage continues at the cell and tissue level, it causes 
various organ damage and disease onset and progression. In our study, the amount of inspired 
oxygen is expected to be low due to keeping the gas supplied to the system low in low-flow 
anesthesia applications. Accordingly, the oxidative stress will be less. Therefore, this study will 
investigate whether low-flow anesthesia positively contributes to the total oxidant/antioxidant 
balance. 
Keywords: General anesthesia, low flow anesthesia, oxidative stress 
 
Introduction 
It is reported that the use of high-flow anesthesia in operating room practice is still over 80%. 
Low-flow anesthesia is associated with a less inflammatory response in the postoperative period 
than high-flow anesthesia. In addition, the low-flow anesthesia technique maintains the 
temperature and humidity of the respiratory system with less effect on mucociliary clearance. 
It preserves tracheobronchial physiology better than high-flow anesthesia. This technique also 
reduces the amount of waste gases released into the environment and atmospheric pollution, as 
well as health risks for operating room personnel, and better preserves the ecological balance. 
One of the most essential advantages of using low current is cost reduction.  
Many risk factors can cause oxidative stress, including alcohol, drugs, environmental 
pollutants, intense exercise, inflammation, and sepsis. Biological targets most exposed to 
oxidative damage include enzymes, cell membranes, and DNA. Oxygen radicals have been 
implicated as an essential cause of mechanisms that can lead to the rapid degradation of 
proteins. Free radical-induced changes in proteins increase the degradation of enzymes. 
Oxidative damage to protein products can affect the activity of enzymes, receptors, and 
transporter proteins. Oxidatively damaged protein products may contain reactive groups that 

can damage the cell membrane and many cellular functions. Peroxidation of lipids occurs when 
biological membranes react with unsaturated fatty acids and proceed by radical chain reaction. 
Oxidative events cause changes in the physical-chemical properties of membranes and thus 
alter fluidity and permeability, with membranes disintegrating with swelling of intracellular 
organelles.  DNA and RNA are sensitive to oxidative damage. DNA is thought to be the main 
target, especially in aging and cancer. Oxidative nucleotides such as glycol, thymidine glycol, 
and 8-hydroxy-2- deoxyguanosine have increased during oxidative damage to DNA by UV 
radiation or free radical damage. Mitochondrial DNA has been reported to be more susceptible 
to oxidative damage in many diseases, including cancer. 
In our study, two groups will be formed: low flow group and high flow group. Vitamin D, 
albumin, CRP, TAS, and TOS values will be checked from all patients before and during the 
operation. During the operation, 1 L/min fresh gas flow will be given to the low-flow group, 4 
L/min fresh gas flow will be given to the high-flow group, and the processed EEG values of all 
patients will be monitored, and the same depth of anesthesia will be ensured. Albumin, CRP, 
TAS, and TOS values from the postoperative blood samples of the patients taken to the ward 
after the operation will be rechecked, and these values will be compared with the previous 
values. 
Our study will compare the changes in total oxidant and total antioxidant systems in general 
anesthesia methods applied with 1 lt/min and 4 lt/min flows. Studies show patient-based 
advantages of low-flow anesthesia, such as respiratory functions and inflammatory response in 
the postoperative period. However, very few studies show its effects on oxidative stress, and a 
comprehensive study evaluating total oxidant/antioxidant systems was not found in our 
literature review. Therefore, our study will contribute to the literature. 
Material and Methods 
Inclusion criteria:  
Patients older than 18 years and younger than 60 years to be operated under general anesthesia 
Patients in the I and II risk groups, according to the American Society of Anesthesiologists 
(ASA) classification 
Exclusion criteria:  
ASA III and above patients, 
Patients for whom an Intensive Care Unit (ICU) indication is foreseen 
Chronic obstructive pulmonary disease, 
A personal or family history of malignant hyperthermia, 
Morbid obesity, 
Alcohol or drug addiction, 
History of liver or kidney disease, 
With coronary artery disease or heart failure, 
Significant anemia or hemoglobinopathy, 

Hypotension, hypovolemia, sepsis. 
After the patients who meet the specified criteria are informed about the study, volunteers who 
agree to participate and sign an informed consent will be included. Vitamin D, albumin, CRP, 
Total Antioxidant Status (TAS), and Total Oxidant Status (TOS) levels will be measured in the 
blood samples obtained from all volunteers' preoperative routine blood samples. After all 
volunteers are admitted to the operation room, they will be monitored with electrocardiography, 
pulse oximetry, non-invasive blood pressure, end-tidal carbon dioxide, temperature probe, and 
processed electroencephalogram- -bispectral index (BIS) without any medication. Baseline 
peak heart rate (HR), peripheral oxygen saturation (SpO2), systolic (SBP) and diastolic blood 
pressure (DBP), end-tidal carbon dioxide (ETCO2), body temperature, and BIS will be 
recorded. All measurements will be repeated and recorded at 5-minute intervals during the 
operation.  
Volunteers will be divided into low-flow group (D) and high-flow group (Y). D group will 
receive 1 L/min fresh gas flow, and Y group will receive 4 L/min fresh gas flow. Processed 
EEG values of all patients will be monitored during the operation and ensured they are at the 
same depth of anesthesia. Albumin, CRP, TAS, and TOS values will be rechecked in the 
postoperative blood samples of the patients during and after the operation and compared with 
the previous values.  
Management Scheme 
Executive Researcher: Ass. Prof. Dr. ÖEK: Contacting the volunteers, explaining the study, 
obtaining informed consent, keeping records, evaluating the data, interpreting statistical 
analysis, and converting the results into an article.  
Researcher: Dr. GS: Contacting the volunteers, explaining the study, obtaining informed 
consent, evaluating the data, interpreting the statistical analysis, and converting the results into 
an article.  
Success Criteria and Alternative Plan  
The project will be considered successful when all procedures of 6 volunteers are completed 
each week. Since the researchers will carry out all measurements if the operation dates of the 
volunteers change or there is disruption due to the work intensity/excuse of the researcher, the 
disrupted time will be compensated by performing the procedures of more than 6 volunteers 
per week. 
Statistical Analysis Plan 
The Shapiro-Wilk test will be used to check the normal distribution of the numerical data, and 
the kurtosis and skewness coefficients will also be examined. Variance homogeneity will be 
analyzed using Levene's test. Independent samples t-test, Welch test, or Mann-Whitney U test 
will compare the groups depending on the data distribution. Depending on the expected value 
rule, categorical variables will be analyzed using Pearson chi-square, Fisher's exact, or Fisher-
Freeman-Halton tests. A comparison of the values measured at different periods during the 
operation will be performed using repeated measures ANOVA. Pearson correlation or 
Spearman's rho will be used in correlation analyses depending on the data distribution. 
Descriptive statistics will be given as mean±standard deviation or median, quartiles, and 
minimum-maximum values depending on the data distribution, and categorical variables will 

be summarized as numbers and percentages. Statistical analyses will be performed using SPSS 
v.22 (IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, 
NY: IBM Corp.) package program, and the significance level will be taken as 0.05.  
Ethical Board Approval 
Duzce University Non-Invasive Health Research Ethics Committee; Date: 25.04.2022; 
Number: 2022/61 
Funding 
Duzce University Scientific Projects Coordination Office; Project Number: 2022.04.02.1335