Efficacy of Transdermal Microneedle Patch for Topical Anesthesia Enhancement in Paediatric Thalassemia Patients

This is a prospective, phase II, randomized, double-blind (participants and care providers), cross-over, negative controlled trial.

Prior to the administration of intervention / control, relevant clinic-demographic profiles (age, gender, ethnicity, anthropometric measurements, presence of comorbidities, thalassemia types etc) will be recorded and entered in the case report forms (CRFs) that are specifically designed for this study.

This research study uses Eutectic Mixture of Local Anesthetics (EMLA) Cream (lidocaine 2.5% and prilocaine 2.5%) as the topical anaesthetic agent. EMLA Cream is a eutectic emulsion mixture of lidocaine and prilocaine at 1:1 ratio (i.e. each gram of EMLA cream contains lidocaine and prilocaine, 25 mg each). A eutectic mixture has a lower melting temperature than each constituent's melting temperature. The anaesthetic efficacy of EMLA cream will be assessed via pain induced by intravenous (IV) cannulation and the primary endpoint is the participant's VAS score measured after applying EMLA Cream (with and without MN application) for 15 and 30 minutes.

The window period given to EMLA Cream for its effect to work will be based on the usual clinical practice observation where it is usually applied for 30 minutes prior to IV catheterization. The rationale behind it is due to logistical issues and for the day care's operational convenience. Nevertheless, in a busy clinical setting, the application time is sometimes shortened to 15 minutes for slight anaesthetic effect. Thus, the study investigators postulate that, with the aid of microneedle, the time to onset of action for EMLA Cream could be greatly reduced, thus requiring less time for EMLA cream to achieve its maximal effects.

According to the routine hospital protocol, all study participants received their blood transfusion based on the Good Clinical Practice (GCP) guidelines. For each participant, the individual will be randomized to one of the 24 treatment sequences and there will be a minimum of 3-weeks washout period before administering the next intervention.

The investigator identified and drew a grid of 1cm × 1cm on the dorsum hand, which served as an ideal site for cannulation. The administrator of intervention (procedurist) will apply either 1 Finger Tip Units (FTUs) of EMLA Cream (approximately 0.68g/cm2) or 0.5 Finger Tip Unit (FTU) (approximately 0.369 g/cm2) over the preparation area. If the patient is subjected to MN patching at his/her visit, the MN patch will be applied by thumb force with the pillar handler pressed firmly against the dorsal hand surface for 5 seconds, mimicking a stamping action, to patch MN to the skin entirely before applying EMLA cream. Otherwise, an empty (i.e without MN) PVA-containing PET sham patch will be applied instead. Besides, the height-to-base ratio (4:1) used for MN will also optimally minimise its adverse effects (pain, redness), thus preserving the masking (blinding) of study participants from knowing the types of interventions received. The preparation area will be covered with an adhesive dressing ( 3M™Tegaderm™, Maplewood, Minnesota, USA) after EMLA cream application. After the allocated application time (15 or 30 minutes), the attending medical officer will set up the transfusion line with a 22-gauge hypodermic needle inserted into the dorsum hand. Throughout the process, the parents/guardians will be allowed to stay by the patient's side at all times.

After the intervention is given to the patients, the participants will be guided on the operating manual for a 10-points, 100mm VAS pain score. The participants will be presented with a ruler that contains 100-mm slots with "No Pain" written on the left side and "Worst Pain" on the opposite right side.

After each procedure, the children then will be asked to move and place the slider in the slot that accurately describes his/her pain at the following time points: 1) right after application of MN/ sham patch or before EMLA Cream application (baseline VAS score); 2) one minute after IV cannulation. The investigator will record the location of the slot where the slider is placed in (millimetres (mm), clearly printed on the ruler's backside) and this will be the participant's VAS score. Throughout the process, there will be a trained nurse standing by at the day-care to assist the verification of the pain scale and to aid the participants who require additional assistance.

Besides, before applying MN patch and EMLA Cream, the patients will be attached with the PainMonitor™ (Med-Storm Innovation AS, Oslo, Norway) device whereby the electrodes will be attached to the hypothenar eminence of the opposite hand not receiving the blood transfusion. The skin conductance peaks (in microSiemens (μS) and the average rise time (in microSiemens per second (μS/s)) will be recorded. Those parameters indicate the skin's sympathetic nerve block induced by the applied EMLA cream.

For skin conductance algesimeter index, the readings right after MN / sham patch application (baseline skin conductance algesimeter index score) and one minute IV cannulation will be obtained from the PainMonitor™ machine.