Impact of Oxygen Saturation Levels on Anastomotic Leakage and Postoperative Complications in Colorectal Surgery
Conditions: Colorectal Anastomosis Leak
Sponsor: Yasir Musa Kesgin

 
 
 
 
 
 
 
 
Official Title: Impact of Oxygen Saturation Levels on Anastomotic 
Leakage and Postoperative Complications in Colorectal Surgery 
NCT number: Not yet assigned 
Document date: 10.04.2026 
 
 
 

 
Study Protocol 
 
Aim of the Study 
This study aimed to evaluate the effect of postoperative oxygen saturation (SpO₂) levels on anastomotic 
leakage and postoperative complications in colorectal surgery. Additionally, the study sought to assess the 
predictive value of oxygen saturation levels for the development of complications and to determine 
potential cut-off values. 
 
Materials and Methods 
This single-center retrospective study included patients who underwent colorectal resection with 
anastomosis between 2017 and 2021. 
Patients were divided into two groups according to the presence or absence of anastomotic leakage. 
Postoperative oxygen saturation (SpO₂) values during the first four postoperative days were compared 
between the groups. 
In addition, patients who developed postoperative overall complications, severe complications, and 
mortality were identified, and the relationship between these outcomes and oxygen saturation levels was 
further analyzed. 
Cut-off values of SpO₂ were also investigated for predicting anastomotic leakage and severe 
postoperative complications. 
 
1. Study Design 
This study was designed as a retrospective, single-center observational study. 
 
2. Study Setting and Period 
The study was conducted at a single tertiary care center, University of Health Sciences Turkey, Bakırköy 
Dr. Sadi Konuk Training and Research Hospital, Department of General Surgery. Patients who 
underwent colorectal resection with anastomosis between January 2017 and January 2021 were 
evaluated. 
 
 
 

3. Study Population 
3.1 Inclusion Criteria 
 
Patients who underwent elective or emergency colorectal resection with anastomosis during the study 
period.  
3.2 Exclusion Criteria 
 
Age under 18 years  
 
Incomplete or insufficient clinical data  
 
4. Study Groups 
Patients were divided into two groups according to the presence of anastomotic leakage: 
 
Anastomotic leakage group  
 
No anastomotic leakage group  
 
5. Data Collection 
Data were retrospectively obtained from hospital electronic records and patient files. The following 
variables were recorded: 
 
Demographic data (age, sex)  
 
Comorbidity burden (Charlson Comorbidity Index, CCI)  
 
Body Mass Index (BMI)  
 
Type of surgery (elective/emergency)  
 
Duration of surgery  
 
Length of hospital stay  
 
Overall post-op complications  
 
Severe post-op complications  
 
Mortality  
 
Oxygen saturation (SpO₂) levels 
 
Presence of anastomotic leakage 
 
6. Exposure Assessment (Oxygen Saturation Levels) 
Postoperative peripheral oxygen saturation (SpO₂) values during the first four postoperative days were 
analyzed. 
SpO₂ measurements were obtained from: 
 
Bedside monitors in continuously monitored patients  
 
Routine vital sign recordings in non-monitored patients (minimum four measurements/day)  
 

Mean SpO₂ values were defined as: 
 
PO1: Postoperative Day 1 mean SpO₂  
 
PO2: Postoperative Day 2 mean SpO₂  
 
PO3: Postoperative Day 3 mean SpO₂  
 
PO4: Postoperative Day 4 mean SpO₂  
 
POg: Overall mean SpO₂ (first 4 postoperative days)  
 
7. Outcomes 
Primary Outcome 
 
Occurrence of anastomotic leakage  
Secondary Outcomes 
 
Overall post-op complications  
 
Severe post-op complications  
 
8. Statistical Analysis 
Statistical analyses were performed using SPSS (Statistical Package for the Social Sciences; SPSS Inc., 
Chicago, IL) version 22.0. 
Categorical variables were expressed as numbers and percentages (n, %), while continuous variables were 
presented as mean ± standard deviation (mean ± SD) or median (min–max), as appropriate. 
The Chi-square test (Pearson Chi-square) was used for comparisons of categorical variables between 
groups. 
Normality of continuous variables was assessed using the Kolmogorov–Smirnov test. 
 
Student’s t-test was used for normally distributed variables  
 
Mann–Whitney U test was used for non-normally distributed variables  
A p-value < 0.05 was considered statistically significant. 
 
9. Ethical Considerations 
This study was conducted in accordance with the Declaration of Helsinki. As a retrospective study, no 
intervention was performed and no additional patient risk was present. Patient confidentiality was strictly 
maintained, and all data were anonymized prior to analysis. 
 
10. Research Questionnaire 
None. 

Informed Consent Form 
We are conducting a study titled “Impact of Oxygen Saturation Levels on Anastomotic Leakage and 
Postoperative Complications in Colorectal Surgery” Anastomotic leakage is defined as the disruption of the 
newly created anastomosis during surgery, resulting in the leakage of gastrointestinal contents into the 
abdominal cavity. It is an important clinical condition in colorectal surgery that increases morbidity and 
mortality, worsens oncological outcomes, and prolongs hospital stay. 
Adequate oxygenation of anastomotic tissues plays a critical role in healing. It has been reported 
that the rate of anastomotic leakage requiring re-operation increases 2.5-fold when oxygen saturation falls 
below 92%. With this study, we aim to investigate this important relationship. 
No identifying personal information will be included in the recorded data or created database. 
The study covers the period between January 2017 and January 2021, and approximately 200 
patients’ data from our clinic will be retrospectively reviewed. No changes, additions, or modifications 
will be made to your treatment during this process. No interventional or experimental procedures will be 
performed. There are no anticipated risks or discomforts associated with participation in this study. If 
there is no expected direct clinical benefit for the participant, this will be clearly explained to the 
participant. 
Participation in this study is entirely voluntary. Participants may refuse to participate or withdraw 
from the study at any time without any penalty, sanction, or loss of rights. Participant identity records will 
be kept confidential and will not be disclosed to the public. Even if the study results are published, the 
identity of participants will remain confidential. 
Monitors, auditors, ethics committee members, institutional representatives, and other relevant 
health authorities may have direct access to the participant’s original medical records; however, this 
information will remain confidential. By signing this informed consent form, the participant or their legal 
representative agrees to such access. 
If new information arises during the study that may affect the participant’s willingness to 
continue participation, the participant or their legal representative will be informed in a timely manner. 
No compensation or payment will be provided, as no additional responsibility is expected from 
participants. No new tissue, blood, or body fluid samples will be collected other than imaging and 
laboratory data stored in hospital archives. For further information regarding the study, rights, or any 
adverse events, you may contact Dr. Yasir Musa Kesgin at +90 212 414 71 71, available 24 hours a day. 
In situations requiring termination of participation, the participant’s involvement will be 
discontinued. 
Declaration 
I have read all the explanations in the “Informed Consent Form.” I have been informed verbally and in 
writing about the purpose and content of the study by the physician named below. I voluntarily agree to 
participate in this study and give permission for my medical data to be used. I understand that my 
treatment will not be affected if I refuse to participate. I am aware that my participation is entirely 
voluntary and that I may withdraw from the study at any time with or without reason. I agree to 
participate in this study of my own free will, without any pressure or coercion. 
PARTİCİPANT 
 
 
 
 
 
RESEARCHER 
 
 
 
 
 
 
 
 
 
Yasir Musa Kesgin, M.D. 
   
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