Ultrasound Assessment of Gastric Residual Volume in Children Scheduled for Elective Surgery After Clear Fluids Fasting for One Versus Two Hours: a Comparative Study
Condition: Gastric Emptying
Study type: Interventional

Summary: 
      Ultrasound guided comparison of gastric residual volume after clear fluid fasting for one
      versus two hours in pediatrics scheduled for elective surgery.
    

Detailed description: 
      Introduction:

      The traditional 2-hour clear fluid fasting time was recommended by almost all anesthesia
      societies [1-3] to decrease the risk of pulmonary aspiration. However, these recommendations
      are based on historical adult literature [4,5] that may not be applicable to the pediatric
      population. Moreover, recent studies have shown that these recommendations may not be
      properly applied, and many children could have been starving for long intervals before
      surgery with the current guidelines [6-8] which was associated with increased risk of post
      induction hypotension during surgical preparation [9,10] There is a growing evidence that
      more liberal clear fluids intake does not result in significant increase in the risk of
      pulmonary aspiration [11,12] while children may have less thirst, hunger, anxiety,
      postoperative nausea and vomiting[13-15] also, limiting the fasting time may improve the
      perioperative inflammatory response in children [16].

      Hence, a consensus statement was issued by the Association of Pediatric Anesthetists of Great
      Britain and Ireland (APAGBI), the European Society of Pediatric Anesthetists and the
      French-Language Society of Pediatric Anesthesiologists; encouraging clear fluids to be given
      up to 1 hour before elective general anesthesia [17] which was followed by the Canadian
      Pediatric Anesthesia Society (CAPS) statement in 2019 [18], however, these statements have
      not been translated into guidelines to date until further evidence is released.

      Gastric residual volume GRV can be used as a preoperative tool for assessment of the risk of
      perioperative pulmonary aspiration in clinical practice [19]. Many methods have been used to
      assess gastric volume in pediatrics including nasogastric aspiration [20] , magnetic
      resonance imaging (MRI) and ultrasound[19,21]. Of these, only ultrasound is of clinical
      utility because it is simple, bedside, reliable [22], safe tool and allows both qualitative
      and quantitative assessment of gastric contents [19,23,24].

      So, we aim to assess GRV in pediatrics having clear fluids fasting for one hour before
      elective surgery. We hypothesize that clear fluids fasting for one hour will not result in a
      clinically significant increase in GRV compared to two hours fasting for children scheduled
      for elective surgery under general anesthesia.

      Methods:

      Following approval from Research and Ethics Committee of anesthesia department, Faculty of
      Medicine, Cairo University. An informed consent will be obtained from parent/care giver prior
      to commencement of the study.

      Inclusion criteria are children aged 3-10 years of both sexes, ASA physical state I and II,
      scheduled for non-gastrointestinal (GIT) elective day-case surgery under general anesthesia
      and fasting for 6 to 8 hours or more for solids. Exclusion criteria are parent or care giver
      refusal, children with gastro-esophageal reflux disease or any disease that impairs gastric
      motility and children scheduled for emergency surgery.

      Patients will be randomly allocated by a computer-generated table into one of the two study
      groups; the randomization sequence will be concealed in sealed envelopes. Patients and
      anesthetist doing the ultrasound examination will be blinded to group assignment. The sealed
      envelopes will be opened in the preparation room by an anesthesia nurse responsible for
      preparation and offering the fluid to the children depending on the group allocation but not
      involved in the study data collection. Children fasting for 6 to 8 hours or more for solids
      only are allowed to drink 3 mL/kg to a maximum of 250 ml of apple juice one hour before
      surgery in (1-hour group) and two hours before surgery in (2-hours group) .Volume of given
      "apple juice" will be calculated by a 50 mL scaled clean syringe then poured into a clean
      cups and offered to the children. Parent/ care giver will be allowed to accompany her/his
      child during the examination period to alleviate anxiety and ensure compliance of children.

      After appropriate time passed, children will be allowed to assess their level of thirst on a
      10 cm VAS scale where 0 point is no thirst which will be clarified by laughing face and 10
      point is the worst thirst and will be clarified by a crying face. In addition, the parents
      will grade their child's thirst on a scale of 0-10. Eligible children weight and height will
      be then measured prior to the examination by a scale and a measuring tape.

      Ultrasound examination will be performed using a high frequency (5-10 MHz) ultrasound probe
      (S-NerveTM; SonoSite Inc., Bothell, WA, USA) or a curvilinear (2-5 MHz) probe as appropriate
      depending on the child weight and age. Children in both groups will be scanned in two
      positions: supine position and right lateral position (RLP) exactly one and two hours
      following the clear fluid intake and before admission to the operation room in groups 1H and
      2H respectively. All gastric ultrasound assessments will be completed by the same
      investigator, who is an anesthetist with 3 years' experience in ultrasound for vascular
      access and regional anesthesia in pediatric patients. Gastric antrum will be located in the
      sagittal plane with simultaneous identification of left lobe of the liver and the descending
      abdominal aorta or inferior vena cava.

      According to its shape and contents, the antrum will be considered to be either empty (if it
      was flat with juxtaposed anterior and posterior walls), fluid-containing (if it was
      distended, with thin walls and hypoechoic content), or solid-containing (if it was distended
      with a content of mixed echogenicity).

      The antral cross-sectional area (CSA) will be calculated after measuring the two dimensions
      of the antrum (D1 and D2) according to the following equation: π [D1 × D2] /4, where D1 and
      D2 are the anteroposterior and craniocaudal diameters, respectively. Measurements will always
      done from the outer layer of the gastric wall, and all images were obtained between
      peristaltic contractions. Three measurements will be collected, and average values were used.

      The gastric residual volume (GRV) will be calculated using a mathematical model previously
      validated in the pediatric population [25] as follows :

      Gastric residual volume (ml/kg) = [-7.8 + (0.035 ×RLP CSA (mm2) + 0.127 × age (months)]/ body
      weight (kg)

      For quantitative assessment of the risk of aspiration, we will use the classification
      previously settled by (Van de Putte and Perlas 2014) [24] as follows:

        -  Low risk of aspiration: children with empty antrum and or children with gastric residual
           volume less than 1.5 mL/Kg.

        -  High risk of aspiration: children with solid contents and or children with gastric
           residual volume more than 1.5 mL/Kg.

      If the child has high risk of aspiration, the surgery would be postponed for one hour before
      another reassessment of the antrum and gastric residual volume.

      Anesthetic management:

      Upon arrival to the operation room; continuous electrocardiography (ECG), pulse oximetry,
      non-invasive arterial blood pressure will be applied then general anesthesia will be induced
      by an experienced pediatric anesthetist who is blinded to the patient group using a
      controlled rapid sequence induction RSI technique (children in a 20° head up position during
      preoxygenation and Induction, rapid hypnosis, non-depolarizing muscle relaxant, gentle mask
      ventilation using Ayres T piece, laryngoscopy, and finally intubation when full motor
      blockade occurred) [26]. If the patient had no intravenous (IV) cannula; anesthesia will
      start using titration of 4-8% sevoflurane and 50% air in oxygen using Ayres T piece without
      positive pressure until the child was put to sleep, peripheral venous cannula will then
      inserted and anesthesia waill be completed using 0.5-1 mg/kg of propofol. If a patient had an
      (IV) cannula in place, induction will be performed using 1.5-2.5 mg/kg propofol, in both
      situations atracurium at a dose of 0.5 mg/kg will be given intravenously to facilitate
      endotracheal intubation and fentanyl at a dose 2 µg/kg was given to abolish stress response
      of intubation. The trachea will be then intubated when full motor blockade occurred.
      Aspiration will be defined as any documentation of vomiting, gastric material in the airway
      during induction till intubation and confirmation of the endotracheal tube ETT using
      capnography.

      The primary outcome of study will be GRV in right lateral position after one-hour clear fluid
      intake.

      Secondary outcomes are antral cross-sectional area in supine and RLP after one-hour clear
      fluid intake, antral cross-sectional area in right lateral and supine positions after two
      hours clear fluid intake, frequency of high risk and low risk of aspiration and qualitative
      grading for assessment of gastric antrum: three-point as follows: Grade 0: empty antrum,
      Grade 1: minimal fluid detected in right lateral position only, Grade 2: distended antrum in
      both semi-sitting and right lateral positions [27]. Incidence of aspiration and or vomiting
      during induction of anesthesia.
    

Intervention name(s): gastric ultrasound; the clear fluid intake
Intervention type(s): Device; Other
Intervention description(s): Children in both groups will be scanned in two positions: supine position and right lateral position (RLP) one and two hours following the clear fluid intake and before admission to the operation room in groups 1 and 2 respectively. Gastric antrum will be located in the sagittal plane with simultaneous identification of left lobe of the liver and the descending abdominal aorta or inferior vena cava.; the clear fluid intake
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: Gastric residual volume; children; ultrasound; fasting