Comparison of the Analgesic Efficacy of Caudal and Quadratus Lumborum Blocks With Pain Monitoring in Lower Abdominal Surgery in Children
Conditions: Regional Anesthesia Success, Pain Monitor During Anesthesia, Quadratus Lumborum Nerve Block, Caudal Block for Postoperative Analgesia, Pediatric Anesthesia
Sponsor: Ankara Etlik City Hospital

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STUDY PROTOCOL  
Study Title: "Comparison of the Analgesic Efficacy of Caudal and Quadratus Lumborum Blocks 
Using a Pain Monitor in Children Undergoing Lower Abdominal Surgery"  
Study Objective and Importance (Primary Objective, Secondary Objectives), Expected 
Benefits and Risks:  
The primary objective of this study is to compare the analgesic efficacy of Caudal and 
Quadratus Lumborum (QL) blocks using a pain monitor (Pain Monitor; PAM).  
Secondary Objectives:  
To evaluate the analgesic efficacy of Caudal and QL blocks in lower abdominal surgeries.  
To compare the postoperative analgesia duration and analgesic requirements between the two 
groups.  
To assess the side effects of Caudal and QL blocks to determine the most suitable method for 
children.  
To evaluate the level of postoperative parental satisfaction.  
We believe our study will contribute to postoperative analgesia management by investigating the 
use of a pain monitor for the objective measurement of pain, which is currently assessed 
subjectively in children.  
Expected Benefits and Risks:  
Benefits:  
If the QL block provides superior analgesia compared to the caudal block, it could be more widely 
used for pain management in pediatric lower abdominal surgeries.  
If the QL block significantly reduces analgesic requirements, it may decrease postoperative side 
effects such as nausea, vomiting, and urinary retention.  
The use of the PAM monitor could provide more reliable pain monitoring, overcoming the 
limitations of subjective scoring, especially in young children.  
This will be one of the few prospective randomized observational studies comparing QL and 
caudal blocks using a PAM monitor in pediatric lower abdominal surgery. The findings could offer 
recommendations for block selection in pediatric anesthesia practice and provide data on the 
reliability of the PAM monitor for pain assessment in children.  
Risks: 
As with all blocks, local anesthetic systemic toxicity (LAST) may occur if dosing adjustments are 
not correctly made.  

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Analgesia may be inadequate due to the technically more challenging ultrasonographic 
application of the QL block or insufficient spread.  
Although very rare, complications such as dural puncture, bleeding, and infection can occur with 
caudal blocks. Similarly, with ultrasound use, there is a very rare risk of peritoneum or kidney 
injury with QL blocks.  
Technical errors related to the PAM monitor may occur; motion artifacts could lead to false 
positive/negative results.  
Satisfaction scoring may not be fully assessed by parents due to socio-cultural factors.  
This study introduces an innovative approach to evaluating pain management in pediatric lower 
abdominal surgery while providing safety and efficacy data for the routine use of the QL block. 
When risks are controlled with methodological rigor, the potential clinical benefits (particularly 
analgesic sparing and objective pain monitoring) will be prominent.  
Study Hypothesis:  
H0: In patients aged 2 months to 6 years undergoing lower abdominal surgery, the 
quadratus lumborum block (QLB) provides more effective analgesia for pain management 
than caudal epidural block.  
H1: QLB significantly reduces nociceptive responses measured objectively by the pain monitor 
(PAM), lowers postoperative FLACC (Face, Legs, Activity, Cry, Consolability) scores, increases 
parental satisfaction, delays the first analgesic requirement, and reduces total analgesic 
consumption.  
Materials (Equipment) – Methods:  
Children aged 2 months to 6 years with ASA I-II status undergoing lower abdominal surgeries 
(e.g., inguinal hernia, orchiopexy, hydrocele) performed by the pediatric surgery unit at Etlik City 
Hospital will be included. Patients will be randomized using the Research Randomizer program 
(https://www.randomizer.org/), and subsequently, QL or caudal blocks will be administered based 
on the assigned sequence. A total of 68 patients will be included in the study, with 34 patients in 
each group.  
Demographic information, anesthesia, and surgical duration will be recorded. Informed consent 
will be obtained from parents/guardians preoperatively. Patients receiving routine oral 
premedication (0.5 mg/kg midazolam) in the preoperative area will be observed. In the operating 
room, after standard monitoring (SpO2, ECG, blood pressure) is established, the PAM monitor 
will be attached. For children under 3 years, a pediatric probe will be placed on the foot; for those 
3 years and older, an adult probe will be placed on the hand. All observed patients will receive a 
standard anesthesia protocol (O2/air, sevoflurane, propofol, LMA, etc.). Under ultrasound 
guidance, a caudal block with 1 ml/kg of 0.125% bupivacaine (maximum volume 20 ml) or a 
bilateral QL block with 0.5 ml/kg of 0.25% bupivacaine (maximum volume 20 ml) will be 

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performed. Following routine awakening, the PAM monitor will be removed, data will be 
recorded, and patients will be monitored for up to 4 hours postoperatively. Any intraoperative 
additional analgesic or anesthetic requirements and their doses will be recorded. The 
anesthesiologists administering anesthesia and performing the blocks will be blinded to the 
study.  
The PAM monitor used is routinely employed in our clinic for many patients and is not specific to 
this study. As indicated, the Medstorm pain probe and device belong to our Anesthesiology and 
Reanimation Clinic and are obtained from the pharmacy's consumables section. The probes used 
are deducted from the pharmacy's consumables stock; therefore, there is no additional cost. For 
this thesis titled "Comparison of the Analgesic Efficacy of Caudal and Quadratus Lumborum 
Blocks (QLB) Using a Pain Monitor in Children Undergoing Lower Abdominal Surgery," the PAIN 
MONITOR (PAM), which operates on the principle of skin conductivity and is used for analgesia 
assessment, will be observed.  
The Painsensor is a pain probe that works on the principle of skin conductivity algometry, 
providing information about the patient's pain and wakefulness states within seconds. It is also 
used in other operating rooms of our hospital to assess block adequacy, wakefulness, and 
analgesic effect. Pain or stressful situations trigger the activation of sweat glands in the palms 
and soles of the feet. Consequently, the skin becomes moist, leading to better skin conductivity. 
The Painsensor detects peaks in skin conductivity. The device uses an algorithm to convert the 
number of peaks into a value between 0-10, called the Pain Index. This Pain Index reflects the 
body's pain or nociceptive response and reacts within 1-2 seconds. It assesses the effect of 
regional anesthesia on unmyelinated sympathetic skin nerves, is unaffected by changes in blood 
circulation or drugs affecting circulation, and is not influenced by the hypotensive effects of 
alpha-2 agonists or the circulatory effects of beta-blockers. It is a nociception response indicator 
usable for all age groups from 23 weeks of gestation. The reason for choosing this probe is that it 
only measures skin conductivity and is not affected by other variable factors like heart rate and 
blood pressure. For children under 3 years, a pediatric probe attached to the sole of the foot will 
be used; for children 3 years and older, an adult probe attached to the hand will be connected to 
the measurement device, and the patient will be monitored throughout the case.  
Intraoperative PAM scores for all patients will be recorded at five time points: during LMA 
insertion, during block performance, during the first surgical incision, 20 minutes after the 
block, and during extubation.  
Postoperative FLACC, PONV (Postoperative Nausea and Vomiting Score), STEWARD 
(Postoperative Recovery Scoring System), and PPPS (Pediatric Anesthesia Parental Satisfaction 
Score) will be assessed at 1, 2, and 4 hours postoperatively.  
Rescue analgesia (IV paracetamol 15 mg/kg) will be administered if the FLACC score is ≥4. The 
time of first administration will be recorded.  
Postoperative PONV scores, awakening scores, and complications will be 
recorded. Postoperative patient data will be obtained from anesthesia files.  
Exclusion Criteria:  
Severe systemic disease (ASA ≥III) 

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Infection at the block site  
Coagulopathy (INR >1.4, platelets <100,000)  
Local anesthetic allergy  
Parental refusal  
Children aged <2 months or >6 years  
Sample Size: A power analysis conducted using G*Power 3.0.10 software determined that a 
total sample size of at least 68 (n1:34 – n2:34) is sufficient with 90% power and a 5% margin of 
error (alpha).  
Test: t-tests - Means: Difference between two independent means (two groups) 
Analysis: A priori: Compute required sample size  
Input: Tail(s) = Two, Effect size d = 0.8, α err prob = 0.05, Power (1-β err prob) = 0.90, Allocation 
ratio N2/N1 = 1  
Output: Noncentrality parameter δ = 3.298485, Critical t = 1.996564, Df = 66, Sample size group 
1 = 34, Sample size group 2 = 34, Total sample size = 68, Actual power = 0.901502  
Statistical Methods:  
Descriptive Statistics: To describe participants' demographic characteristics (age, gender, etc.) 
and other variables.  
Mean and Standard Deviation: To assess the average and distribution of continuous 
variables, such as pain levels.  
Comparative Statistics: T-Test: To compare mean pain levels between the two 
independent groups (Caudal and Quadratus Lumborum blocks).  
Correlation and Regression Analysis:  
Pearson Correlation: To examine the relationship between pain levels and other variables 
(e.g., age, drug consumption).  
Multiple Regression Analysis: To evaluate the effect of multiple independent variables (e.g., block 
type, age, gender) on the dependent variable (pain level).  
The study does not involve providing any biased/misleading information to participants or 
completely concealing the study's purpose. All study information will be explained to participants 
comprehensibly, and consent will be obtained. 
The research does not contain questions or practices that threaten the physical or mental health 

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of participants. It is an observational study aimed at monitoring the outcomes of regional blocks 
routinely applied for postoperative analgesia in the pediatric operating room.  
Participants' personal rights and private information are protected. Personal data will not be 
recorded or shared with any institution.  
The identities of participants will not be identified in the collected raw data/stored data. They 
will not be used anywhere.  
The identities of participants will not be identified in the report content.  
Study Termination Criteria:  
Reasons Related to Patient Safety: Block failure (need for additional analgesia due to pain 
at surgical incision).  
Technical Failure: Inability to perform the ultrasound-guided block due to anatomical 
reasons. Inability to obtain data from the pain monitor (device failure, artifact).  
Protocol Violations: Randomization error or mixing of patient groups.  
Outcome Assessment (Primary and Secondary Endpoints – Outcome Evaluation Criteria):  
Primary Outcome:  
Intraoperative PAM scores (during LMA insertion, during block performance, during the first 
surgical incision, 20 minutes post-block, during extubation). The QL block is expected to provide 
a significant decrease in PAM values compared to the caudal block.  
Secondary Outcomes:  
Lower FLACC scores in the QL group compared to the caudal group at postoperative hours 1, 
2, and 4.  
Later time to first analgesic requirement (IV paracetamol 15 mg/kg administered when FLACC 
≥4) in the QL group compared to the caudal group.  
Lower total consumption of rescue analgesic doses in the QL group.  
The correlation between PAM and FLACC scores will be assessed.  
Lower incidence of postoperative PONV (%) and antiemetic requirement in the QLB 
group. Higher postoperative awakening score (Steward score) in the group receiving QLB.  
Higher postoperative pediatric anesthesia parental satisfaction score (PPPS) in the group 
receiving QLB. 

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Block complications: Local anesthetic systemic toxicity (LAST), hematoma, 
infection. Outcome Evaluation Criteria:  
PAM scores, FLACC scores, Steward score, PPPS score, time to first analgesic, and 
amount (mg/kg).  
PONV (0-none, 1-once, 2-twice, 3-three times or more).  
Successful Block Criterion: No increase in PAM score after surgical incision (nociceptive 
response suppressed).  
Failed Block: FLACC ≥4 or need for intraoperative supplemental analgesia (if block repetition is 
required, the patient will be excluded from analysis).  
Steward awakening score: A score <4 indicates a need for additional observation; a score of 6 
indicates readiness for discharge.  
PPPS (Postoperative Pediatric Parental Satisfaction) will be measured using a Likert scale; each 
item is scored 1-5 (1=not satisfied at all, 5=very satisfied) (pain management, child's comfort, 
medical team's communication, clarity of post-discharge instructions, overall satisfaction; total 
score 5-25).  
Clinical Implications:  
If the superiority of the QL block is proven, it could be recommended as the standard 
regional block technique in pediatric lower abdominal surgeries.  
If the PAM-FLACC correlation is high, objective pain monitors could be integrated into routine use 
in children. 
INFORMED CONSTENT FORM  
INFORMED CONSENT AND VOLUNTEER INFORMATION FORM  
(Physician's Explanation)  
We are conducting a study in the pediatric operating room of our hospital. The title of this study is 
"Comparison of the Analgesic Efficacy of Caudal and Quadratus Lumborum Blocks (QLB) Using 
a Pain Monitor in Children Undergoing Lower Abdominal Surgery."  
In this study, no new medication will be administered to your child, no blood will be drawn, and no 
additional tests will be performed. This is a study comparing two different analgesic techniques 
used to prevent pain after your child's surgery. The study will last approximately six months, and a 
total of 68 patients will be included.  
The potential benefits of this study include reducing postoperative pain, thereby increasing 
comfort, decreasing the need for analgesic medication, and consequently preventing nausea and 

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vomiting. We invite you to participate in this research. However, we must state that participation is 
entirely voluntary. Your decision to participate or not will be respected.  
Before you decide, we wish to inform you about the study. Please read and understand this 
information. If you agree to participate after reviewing it, please sign this form.  
After the regional block is administered to your child, a small adhesive sensor will be placed on 
the sole of the foot or the palm of the hand to measure pain levels. This sensor will be removed 
after your child wakes up from anesthesia. Subsequently, at the 1st, 2nd, and 4th hours 
postoperatively, we will ask you a few questions and assess the child's status.  
If you agree to participate, your child will be evaluated by Dr. Dilara Yiğit or a physician she 
appoints, and the findings will be recorded.  
You will not be charged any fees for participation in this study. You will also not receive any 
payment for participating.  
Your child's medical information will be kept confidential. However, it may be reviewed by quality 
assurance personnel, ethics committees, or official authorities for auditing purposes, as required 
by regulations.  
Your child will be informed about this research in an age-appropriate manner, and their assent will 
be sought for participation.  
You have the right to refuse participation. Participation in this research is entirely voluntary. If you 
decline, it will not affect your child's medical care in any way. You also retain the right to withdraw 
your consent at any stage of the study without any penalty.  
(Declaration of the Participant's Parent(s)) 
I have been informed by Dr. Dilara Yiğit about the above details regarding a medical research 
study to be conducted in the Department of Anesthesiology and Reanimation at Ankara Etlik City 
Hospital. Following this explanation, my child has been invited to participate as a subject in this 
study.  
I trust that the confidentiality of information, which must be maintained between the physician and 
myself, will be respected with great care during this research. I have been sufficiently assured 
that the data will be meticulously protected when used for educational and scientific purposes.  
I understand that I may withdraw my child from the study at any time without providing a reason. 
(However, I am aware that it is appropriate to inform the researchers in advance of my withdrawal 
to avoid inconveniencing them). Furthermore, the investigator may discontinue my child's 
participation in the study, provided it does not harm my child's medical condition.  
I will not incur any financial responsibilities for the expenses related to the research. No 
payment will be made to me.  
I have been assured that in the event of any health problem arising directly or indirectly from the 

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research procedures, all necessary medical intervention will be provided. (I will also not bear any 
financial burden for these medical interventions).  
I understand that if my child encounters any health problem during the research, I can contact 
Dr. Dilara Yiğit at any time at the following numbers: 0312 797 00 00 (work) or 0533 471 92 02 
(mobile), or at the address of the Ankara Etlik City Hospital, Department of Anesthesiology and 
Reanimation.  
My child may choose not to participate in this research. I have not been subjected to any coercive 
behavior regarding my child's participation. I also understand that if I refuse participation, it will 
not adversely affect my child's medical care or my relationship with the physician.  
I have fully understood all the explanations provided to me. After a period of independent 
consideration, I have decided to allow my child to participate as a subject in this research 
project. I accept this invitation with great satisfaction and voluntariness.  
A copy of this signed form will be given to me.  
Parent of the Participant:  
Name, Surname:  
Address:  
Tel.  
Signature  
Witness:  
Name, Surname:  
Address:  
Tel.  
Signature: 
Physician who obtained 
consent: Name, Surname, Title:  
Address:  
Tel.  
Signature  
Date: ... / ... / ...