Comparison of Weight-based Versus External Ear-size Based Technique for Selection of Laryngeal Mask Airway in Pediatric Surgical Patients.

Study Overview
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Brief Summary
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Laryngeal Mask Airway (LMA) is widely used in pediatric surgical patients. The manufacturer recommends the size of LMA to be used in children should be based on actual body weight but this method has several limitations. To overcome these concerns, various alternatives have been tried by different researchers, one of them is external ear size for LMA size selection. Investigators therefore would like to know whether the external ear size based method can be used for LMA size selection in pediatric surgical patients in Pakistan.

Detailed Description
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OBJECTIVE: to determine whether external ear-size is non-inferior to weight for LMA size selection in pediatric surgical patients. INTRODUCTION: The Laryngeal Mask Airway (LMA) is widely used in pediatric population. The manufacturer recommends the size of LMA to be used in children should be based on actual body weight. However, this method has several limitations, the range of weight for a particular size is very wide, it may not be appropriate for overweight or underweight children as it is based on actual body weight rather than ideal body weight, in emergency situations where weight of the patient is unknown the correlation between weight and size of LMA is impossible, and finally weight based recommendation may not be suitable as development of the child's oropharyngeal cavity is related to height and age rather than weight. All these factors may lead to inappropriate size selection, which may result in larger sized LMA causing trauma/injury to the airway and smaller ones causing obstruction or insufficient ventilation. To overcome these concerns various alternatives to weight based technique have been tried by different researchers in both adult and pediatric patients, one of them is external ear size. Literature revealed differences in external ear size dimensions in different ethnic population and the investigator's literature search failed to reveal any local data/study in Pakistani pediatric patients where external ear size was compared or used for size selection of the LMA. The investigators therefore would like to know whether the external ear size based method can be used for LMA size selection in pediatric surgical patients in Pakistan. HYPOTHESIS: External ear-size based technique is not inferior to weight based technique for LMA selection in pediatric population.

Official Title
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Comparison of Weight-based Versus External Ear-size Based Technique for Selection of Laryngeal Mask Airway in Pediatric Surgical Patients.

Conditions
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Laryngeal Masks, Minors, Child, Pediatrics

Intervention / Treatment
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* Device: Ear Size Based Method (Ambu® AuraOnce™ Laryngeal Mask Airway)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All children aged between 6 months to 18 years of age of either sex American Society of Anesthesiologist (ASA) Classification I-II Elective surgical procedures in whom an LMA will be indicated Procedure lasting up to 2hrs Exclusion Criteria: Any external ear morphological abnormality Previous external ear surgeries Patient/Parent refusal Children with oropharyngeal lesion Any patient conditions (Gastroesophageal Re-flux Disease [GERD], hiatal hernia, incomplete NPO, bowel obstruction etc.) or procedures requiring rapid sequence induction and intubation History of Upper respiratory tract infection (URTI) within the last 2 weeks

Ages Eligible for Study
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Minimum Age: 6 Months
Maximum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: All Laryngeal Mask Airways (LMA) devices being used in the study will be Ambu® AuraOnce™ (Ambu® A/S Baltorpbakken 13 DK-2750 Ballerup, Denmark) LMA's. LMA Size Selection: will be done for each patient according to group allocation: Group A - Weight based method Group B - Ear Size Based method Randomization technique: Patients will be randomized according to computer-generated blocked randomization (https://www.sealedenvelope.com) with blocks size of 6, by independent statistician (Anaesthesia research cell). Allocation concealment will be ensured by enclosing assignments in sealed, opaque, sequentially numbered envelopes which will be opened by one of the investigator only upon arrival of the patient in the operation room.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Group A - Weight Based Method<br>Body Weight Based method: This is the conventional method for LMA size selection. The patient will be weighed and LMA size corresponding to their weight will be used as follows. (LMA Size - 1 for up to 5 kg of body weight) (LMA Size - 1.5 for 5 to 10 kg of body weight) (LMA Size - 2 for 10 to 20 kg of body weight) (LMA Size - 2.5 for 20 to 30 kg of body weight) (LMA Size - 3 for 30 to 50 kg of body weight) | |
| Experimental: Group B - Ear Size Based Method<br>Ear Size Based method: External ear size will be measured by using a paper ruler and will be recorded in cm as follows: Vertical length: will be measured from the most dependent portion of the lobule to the furthest portion of the auricle. Horizontal length (width): from the tragus to the furthest part of the helix horizontally. Dimension(cm2): Vertical length (L) × Horizontal length (width-W ) Based on these ear measurements, nearest smaller LMA size will be selected. | Device: Ear Size Based Method (Ambu® AuraOnce™ Laryngeal Mask Airway)<br>* The Laryngeal Mask Airway (LMA) is one of the devices used to maintain airway during general anesthesia. Its appropriate size is selected according to patients body weight as recommended by the manufacturer. However its appropriate size can also be selected via several other methods and one of them is patients external ear size. In this study the investigators will compare external ear size based method for LMA selection with the standard weight based method for LMA size selection. Vertical Ear length: will be measured from the most dependent portion of the lobule to the furthest portion of the auricle. Horizontal Ear length (width): from the tragus to the furthest part of the helix horizontally. Dimension(cm2): Vertical length (L) × Horizontal length (width-W) LMA Size LMA Cuff Length (cm) corresponding to vertical ear length. LMA Cuff Width (cm) corresponding to horizontal ear width.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proper Placement | Proper LMA placement will be assessed by chest expansion on positive pressure ventilation, absence of audible leak and a square wave capnograph waveform. | 1 minute | 
| Adequacy of Ventilation | Adequacy of ventilation: will be judged by an oxygen saturation of greater than or equal to 95% at a Fractional Inspired Oxygen concentration (FiO2) less than 0.5 and an end-tidal carbon dioxide (ETCO2) of 35-45 mmHg at a tidal volume of 6- 8 ml/kg Actual Body Weight (ABW) at peak airway pressure less than the oropharyngeal leak pressure (OLP), and by adjusting the respiratory rate (RR). | 1 minute | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Oropharyngeal Leak Pressure (OLP) | Oropharyngeal Leak Pressure (OLP): will be determined at LMA intra-cuff pressure of 60 cmH2O by closing the Adjustable Pressure Limiting (APL) valve of the circle system at a fixed gas flow of 3 Liters per minute and by noting the circuit pressure at which an equilibrium will be reached and then releasing it completely. | 30 seconds | 
| Leak fraction (LF) | Leak fraction (LF): will be determined by comparing the difference between inspired and expired tidal volumes and dividing them by the inspired tidal volume at a tidal volume (TV) of 8 ml/kg actual body weight (ABW) with an I:E ratio of 1:2 and respiratory rate (RR) of 20 breaths per minute. | 1 minute | 
| Incidence of mucosal injury and laryngospasm | Incidence of mucosal injury in the two groups will be assessed by trauma or minor injury to the airway seen as blood on the device after removal. Incidence of laryngospasm will also be noted. | 1 minute | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Ear Size