Supraorbital Pressure Versus Jaw Thrust for Assessing the Adequate Depth of Anesthesia for LMA Insertion in Children

The investigators enrolled fifty consecutive participants (aged one to ten years) with ASA physical status I or II scheduled to receive general anesthesia for various surgical procedures. Participants were allowed to have solid food, formula milk or cow's milk up to six hours, mother's milk up to four hours and clear fluid up to two hours before surgery.

On reaching the pre-operative room, when the participant was still on mothers lap or on the bed baseline measurements of non-invasive blood pressure (NIBP), pulse oximeter (SpO2) and electrocardiography (ECG) were taken. Fifteen minutes before induction of anesthesia, all participants were premedicated with ketamine, either 4mg/kg intramuscularly into the gluteal region with 26 G needle, or with 0.5mg/kg intravenously if intravenous (IV) cannula was in place.

Devices for ECG, SpO2 and NIBP monitoring were attached to the participant after arrival in the operating room. IV line was then inserted, if not already present. Pre-oxygenation was done with 100% oxygen using an appropriate size face mask. Anesthesia was induced with IV fentanyl (2mcg/kg), and propofol (2-4 mg/kg) until the loss of response to verbal contact or loss of eyelash reflex. Spontaneous ventilation was first assisted and then controlled manually to maintain an end-tidal carbon dioxide partial pressure of 33-40 mmHg. No neuromuscular blocking agent was administered.

Supraorbital pressure or jaw thrust was performed after loss of response to verbal contact, or absence of body movements. In group SOP, supraorbital pressure was applied over the supraorbital notch for five seconds. In group JT, the jaw thrust was applied gently by lifting the angles of the mandible vertically upward for five seconds. An IV bolus dose of propofol (1 mg/kg) was added if there was a motor response to the supraorbital pressure or the jaw thrust and the test was repeated after ten seconds. A second bolus dose of propofol was repeated if positive motor response was still present. A negative physical response to the test was considered as the end point of induction to perform LMA insertion. A classic LMA of appropriate size was inserted immediately. Ease of insertion and mouth opening, development of coughing, swallowing, movement, laryngospasm, or gross purposeful movements during or within one minute of LMA insertion and additional dosage of propofol if required were recorded. The LMA insertion was considered unsuccessful if LMA could not be inserted after administration of second bolus dose of propofol. The number of attempts and the insertion conditions were recorded using a six variable three points scoring system(31)

• Mouth opening: 1 - Full, 2 - Partial (not ideal but permits easy opening of mouth), 3 - Nil
• Ease of LMA insertion 1 - Easy, 2 - Difficult, 3 - Impossible.
• Swallowing: 1 - Nil, 2 - Mild, 3 - Severe
• Coughing: 1 - Nil, 2 - Mild, 3 - Severe
• Laryngospasm: 1 - Nil, 2 - Mild (relieved by positive pressure ventilation), 3 - Severe (desaturation<90%)
• Movement: 1 - Nil, 2 - Mild (Finger) (some movement but did not affect positioning of LMA), 3 - Severe (Arm/leg) (holding of LMA was required and additional dose of induction agent given).

The investigators summed all the five scores to give a LMA insertion condition summed score which ranged from 0 to 12, a lower summed score indicating more favourable LMA insertion conditions.

Table: Laryngeal mask airway insertion score.

Variables 0 1 2

Mouth opening Complete Partial Impossible Ease of insertion Easy Difficult Impossible Swallowing Nil Partial Complete Coughing Nil Partial Complete Laryngospasm Nil Partial Complete Movement Nil Partial Gross

LMA cuff was inflated with air and was connected to Jackson-Rees modification of the Ayre's T-piece. Effective ventilation was determined by observing chest wall and bag movement, auscultation, and capnography.

Blood pressure, heart rate and percentage saturation of oxygen were recorded in the pre-operative room, immediately after LMA insertion, five, ten and fifteen minutes after LMA insertion.

Anesthesia was maintained with isoflurane in oxygen. After the closure of skin incision, removal of LMA was done when the participant was still in deep plane of anesthesia.