Comparing 0.2 ml and 0.5 ml Oral 24% Sucrose Solution for Pain Relief During Heel Prick in Neonates With Historical Controls

Background and Rationale Neonates are capable of perceiving and responding to pain from birth. Heel prick is a common but painful invasive procedure used for newborn screening and clinical monitoring. Repeated or inadequately treated procedural pain may result in physiological stress and adverse short- and long-term developmental and behavioural effects. Effective, safe, and practical pain management is therefore an important component of neonatal nursing care.

Oral sucrose is widely used as a non-pharmacological intervention for procedural pain in neonates. The analgesic effect is thought to be associated with sweet taste stimulation and activation of endogenous opioid-mediated pathways. Although 24% oral sucrose is commonly used, the optimal dose and minimally effective dose remain uncertain. Published recommendations vary considerably, ranging from approximately 0.1 mL to 1.0 mL, and clinical practice differs between institutions.

This study will directly compare two clinically relevant doses: 0.2 mL and 0.5 mL of 24% oral sucrose. The 0.2 mL dose represents a commonly used lower dose, while 0.5 mL has been reported to provide greater analgesic benefit in some studies. Comparing these doses may provide more clinically useful information than comparing 0.5 mL with a theoretical minimum dose that may be difficult or less practical to administer routinely.

A historical control group will also be included to describe the effect of introducing oral sucrose in addition to standard non-pharmacological care. The historical group will consist of eligible neonates who previously underwent heel prick without oral sucrose. Historical data will be obtained from the same clinical unit using the same eligibility criteria and outcome measure, with appropriate statistical adjustment for potential confounding factors.

Study Objectives Primary objective To determine whether administration of 0.2 mL of 24% oral sucrose is non-inferior to 0.5 mL of 24% oral sucrose in reducing procedural pain during heel prick in neonates born at ≥37 weeks of gestation.

Secondary objectives

To compare between the 0.2 mL and 0.5 mL groups:

N-PASS pain scores at the time of heel puncture and during blood collection.

Change in N-PASS pain score from baseline.

Duration of crying during the heel-prick procedure.

Changes in physiological parameters, including heart rate and oxygen saturation.

The proportion of neonates achieving clinically meaningful pain relief.

The study will also compare the two prospective intervention groups with the historical no-sucrose control group as a supplementary analysis.

Study Design This is a prospective and retrospective, randomized, single-blinded, two-arm parallel-group clinical trial with a historical control group.

The prospective randomized component will include 100 neonates. Participants will be randomly allocated in a 1:1 ratio to receive either:

0.2 mL of 24% oral sucrose; or

0.5 mL of 24% oral sucrose.

The historical control component will include 50 eligible neonates who underwent heel prick before implementation of the oral sucrose protocol and received standard non-pharmacological care without sucrose. The total planned sample size is therefore 150 neonates.

Study Setting The study will be conducted in the 54-bed Special Care Baby Unit at Kwong Wah Hospital. The unit has standardized heel-prick procedures, trained neonatal nursing staff, routine physiological monitoring, and access to eligible neonates.

Study Population The prospective study population will comprise neonates admitted to the SCBU from 13 April 2026 to 31 July 2026.

Historical control data will be retrieved from patient records for neonates who underwent heel prick between 1 January 2026 and 31 March 2026.

Eligibility Criteria Inclusion criteria

Neonates will be eligible if they meet all of the following criteria:

Gestational age of ≥37 weeks.

Age from 0 hours to 28 days.

Requiring a routine heel-prick procedure, such as newborn screening or routine monitoring.

Parent or legal guardian able to read and understand Chinese or English.

For prospective participants, written informed consent provided by a parent or legal guardian before enrolment.

Exclusion criteria

Neonates will be excluded if they have:

Severe congenital malformations.

A neurological disorder.

A known metabolic disorder.

Previous administration of sedatives or analgesics relevant to the procedure.

Feeding intolerance or gastrointestinal disease.

Any other clinical condition judged by the clinical team to make participation inappropriate.

Intervention The allocated 24% oral sucrose solution will be administered approximately two minutes before the heel prick. The investigator nurse will slowly deliver the assigned volume onto the anterior surface of the neonate's tongue.

The two intervention doses are:

Group 1: 0.2 mL of 24% oral sucrose solution.

Group 2: 0.5 mL of 24% oral sucrose solution.

All neonates will receive the unit's usual standardized non-pharmacological measures, including appropriate positioning, swaddling where clinically suitable, and non-nutritive sucking according to routine practice.

The heel prick will be performed according to the unit's standard operating procedure.

Historical Control The historical control group will consist of eligible neonates who underwent heel prick during the specified retrospective period before introduction of the sucrose protocol. These neonates received standard non-pharmacological measures but no oral sucrose.

Only existing medical and research records will be reviewed. No additional intervention, examination, or contact with the neonates will occur. Historical data will be collected using the same eligibility criteria and outcome measures as the prospective groups where complete data are available.

Randomization and Allocation Concealment Prospective participants will be randomly allocated in a 1:1 ratio using a computer-generated randomization sequence.

Allocation concealment will be maintained using sequentially numbered, opaque, sealed envelopes. The envelopes will be prepared by an independent investigator who is not involved in participant assessment or intervention administration.

After consent and eligibility confirmation, the next available envelope will be opened by the designated investigator nurse responsible for preparing and administering the study solution.

Blinding This will be a single-blinded study.

The investigator nurse who prepares and administers the sucrose solution will know the treatment allocation. The case nurse conducting the N-PASS assessment, the phlebotomist performing the heel prick, and the data analyst will remain blinded to group allocation.

The study solutions will be prepared in a manner that minimizes disclosure of the allocated dose and will be labelled using neutral identifiers, such as "Solution A" and "Solution B." Parents or legal guardians will not be present during the procedure in order to support blinding of the procedural team.

Blinding will not apply to the historical control group because it is a non-randomized retrospective group.

Outcome Measures Primary outcome The primary outcome will be the change in N-PASS pain score during the heel-prick procedure, with particular emphasis on the difference in pain response between the 0.2 mL and 0.5 mL groups.

N-PASS pain/agitation scores range from 0 to 10, with higher scores indicating greater pain or agitation:

0-2: Adequate pain control.

3-6: Mild to moderate pain.

7-10: Severe pain or agitation.

N-PASS will be recorded at baseline before sucrose administration and during the heel-prick procedure, including at heel puncture and during blood collection.

Secondary outcomes

Secondary outcomes will include:

Duration of crying, measured from the start of heel puncture until crying cessation.

Change in heart rate.

Change in oxygen saturation.

Other routinely recorded physiological parameters, where available.

Proportion of neonates achieving clinically significant pain relief.

Comparison of outcomes with the historical no-sucrose control group.

Study Procedures Screening and enrolment: The research team will identify potentially eligible neonates. Parents or legal guardians of prospective participants will receive an explanation of the study and will provide written informed consent before enrolment.

Baseline assessment: Demographic and clinical information will be collected, including gestational age, birth weight, sex, and Apgar score. Baseline N-PASS and physiological parameters will be recorded.

Randomization: Consented eligible neonates will be assigned to receive either 0.2 mL or 0.5 mL of 24% oral sucrose.

Sucrose administration: The allocated solution will be administered slowly onto the anterior tongue approximately two minutes before heel puncture.

Heel prick: The procedure will be performed by the designated phlebotomist according to the unit's standardized procedure.

Pain assessment: A trained case nurse blinded to treatment allocation will assess and record N-PASS scores at the predefined time points.

Physiological monitoring: Heart rate and oxygen saturation will be continuously monitored using the unit's multi-parameter monitor.

Crying assessment: A timer will be used to record the duration of crying from the start of heel puncture until crying cessation.

Historical data review: Data for eligible historical controls will be retrieved from existing clinical records using a coded data collection form.

N-PASS Training and Standardization All participating nurses will complete standardized training in N-PASS administration. Training will include lectures, demonstrations, and scenario-based practice.

Before participating in data collection, nurses will be required to achieve at least 90% agreement with the assessor on three consecutive practice assessments. Monthly calibration sessions will be conducted throughout the study to reduce inter-rater variability and scoring drift.

Sample Size The prospective randomized comparison will include 100 neonates, with 50 neonates in each sucrose-dose group. The sample size was calculated using G*Power, based on a power of 80%, a two-sided alpha level of 0.05, an assumed effect size of 3, and a standard deviation of 6 for the N-PASS score.

An additional 50 neonates will be included in the historical control group. The planned total sample size is therefore 150 neonates.

The historical control group is intended primarily to provide supplementary contextual information regarding outcomes before implementation of the sucrose protocol and is not part of the primary randomized comparison.

Data Analysis Baseline demographic and clinical characteristics will be summarized using means and standard deviations or medians and interquartile ranges for continuous variables, and frequencies and percentages for categorical variables.

For the primary comparison between the two prospective groups:

Independent-samples t-tests will be used for normally distributed continuous outcomes.

Mann-Whitney U tests will be used when distributional assumptions are not met.

Changes in N-PASS scores and physiological parameters will be analyzed using appropriate paired tests, such as paired t-tests or Wilcoxon signed-rank tests.

Categorical outcomes will be compared using chi-square tests or Fisher's exact tests, as appropriate.

For supplementary comparisons involving the historical control group:

One-way analysis of variance will be used for normally distributed continuous outcomes.

The Kruskal-Wallis H test will be used for non-normally distributed outcomes.

Appropriate post-hoc pairwise comparisons with Bonferroni adjustment will be performed where indicated.

Statistical adjustment for clinically relevant baseline differences and potential confounding variables will be considered because the historical control group is non-concurrent and non-randomized.

All statistical analyses will be conducted using IBM SPSS Statistics for Windows, version 25.0. A p-value of <0.05 will be considered statistically significant. For the primary non-inferiority objective, the final statistical analysis should also specify a clinically justified non-inferiority margin before database lock.

Potential Benefits Participants may experience reduced pain or distress during heel prick. The study may also help establish a consistent and evidence-based oral sucrose dose for routine neonatal procedural pain management.

There may be no direct individual benefit to every participant. However, the findings may improve the future care of neonates undergoing heel-prick procedures in the SCBU and other neonatal care settings.

Potential Risks and Discomforts Oral sucrose is a non-pharmacological intervention commonly used for neonatal procedural pain. Possible risks may include coughing, gagging, choking, vomiting, feeding intolerance, or transient physiological instability. The assigned volume will be administered slowly, and the neonate will be monitored throughout the procedure.

Neonates who have feeding intolerance or gastrointestinal disease, or who have received sedatives or analgesics, will be excluded. The heel prick itself is part of routine clinical care and is not performed solely for research purposes.

If any clinical concern arises, the procedure will be managed according to routine hospital policy and the responsible clinical team will be informed.

Confidentiality and Data Protection Each participant will be assigned a unique study code. Direct identifiers will not be included in the research database or analysis dataset.

Paper records will be stored in locked cabinets within the department or ward. Electronic data will be stored on secure hospital computers with restricted access. Access will be limited to authorized members of the research team.

Research and personal data will be retained for five years after completion of the study in accordance with hospital and Hospital Authority requirements. At the end of the retention period, data will be securely destroyed or erased.

Results will be reported in aggregate form, and individual participants will not be identifiable in presentations, reports, or publications.

Informed Consent and Withdrawal Written informed consent will be obtained from the parent or legal guardian before enrolment in the prospective randomized study.

Participation will be voluntary. Parents or legal guardians may decline participation or withdraw their neonate at any time without affecting the standard of medical or nursing care provided.

For the historical control group, the study involves retrospective review of existing clinical records only, without additional intervention or participant contact. A waiver of consent may be sought from the Research Ethics Committee or Institutional Review Board, subject to institutional requirements and approval.

Ethical and Regulatory Considerations The study will be conducted in accordance with the Declaration of Helsinki, ICH Good Clinical Practice principles, and applicable Kwong Wah Hospital and Hospital Authority policies.

Ethics or institutional review approval will be obtained before commencement of prospective recruitment and data collection. Any protocol amendments will be submitted for prior approval where required.

Expected Contribution This study is expected to provide locally relevant evidence regarding whether 0.2 mL of 24% oral sucrose provides pain relief comparable to 0.5 mL during neonatal heel prick. The results may support development of a standardized sucrose administration guideline, reduce unnecessary variation in nursing practice, and contribute to safer and more consistent neonatal pain management in Hong Kong.