Point-of-care ultrasound for confirmation of gastric tube placement in pediatric patients requiring mechanical ventilation

Introduction

Severe brain injury patients enter an acute catabolic state and necessitate nutrition to maintain cerebral metabolic homeostasis, skeletal muscle mass, and vital organ function. In an ICU feeding tubes are frequently inserted for critically ill patients and for those who are intubated and require ventilator support. Although the incidence of tube displacement is low serious complications have been reported because of tube displacement, including misplacement of the tube in the tracheobronchial tree pneumothorax pneumomediastinum pneumonia bronchopleural fistula esophageal perforation bleeding aspiration, and even death. Meta-analysis and review studies reported that capnography alone unreliably reflects FT placement, and X-rays will be unavoidable. Therefore, the radiographic confirmation of FT placement is considered the gold standard. However using this method in ICU patients has several disadvantages, including radiation exposure high cost, and extensive labor. Ultrasonography allows for real-time images of the FT passage to be obtained while verifying the tube placement in the esophagus and the stomach. USG may play a new and yet important role in catering to the needs of these patients. While point-of-care ultrasound is currently used to confirm FT insertion reports of its use in the pediatric emergency department are still scarce. We want to conduct this study to estimate the diagnostic accuracy of ultrasound examination at the neck and gastric region in verifying the correct placement of FTs in pediatric patients requiring mechanical ventilation in the NICU.

Aims and objectives

Primary

To assessthe ability of the esophageal and gastric ultrasound to confirm the successful placement of a gastric tube in pediatric head injury patientsrequiring mechanical ventilation.

Secondary

Compare the time to confirm the successful placement of GT using ultrasonography and radiography.

Materials and Methods

Following approval of the Institute Ethics Committee one hundred four pediatric head injury patients admitted to the neuro ICU requiring mechanical ventilation in the JPNTC Centre AIIMS New Delhi will be enrolled for this study. Written informed consent will be obtained from the patient’s legally authorized representative before the study.

Study design- A prospective observational study.

Inclusion criteria

Pediatric patients aged between 1 and 14 years, of either gender, with severe traumatic brain injury admitted to the Neuro ICU requiring an FT placement.

Admitted to the NICU within 72 hours of injury

Exclusion criteria

Patients with a history or confirmed case of esophageal varices with endoscopy.

Patient with blunt trauma abdomen severe thoracic injury with associated hemothorax

Patients with a history of post-gastric bypass surgeries

Patients with a known history of nasopharyngeal, esophagus, or stomach carcinoma

Patients with a history of neck trauma or swelling, including goiter

Patients relative or LAR who do not wish to participate in the study

Nasogastric tube placement

An orogastric ornasogastric tubewill be inserted on admissionto the NICU.Anaesthesiology residents will insert polyvinylchloride FTs. with radio-opaque lines using the nose ear mid-umbilicus method. The length of the NG tube will be established by measuring the distance from the tip of the nose to the tip of the patient’s earlobe and then to the mid-umbilicus process.

In every instance, the end of the tube will be lubricated before being inserted. Once the clinical signs of accurate placement are achieved by either auscultation or aspiration of stomach material, the FT will be fixed to the patient’s nose or cheek using adhesive tape. The clinical team will be blinded to the ultrasonography findings of the study so that it will not influence their standard treatment protocol.

Ultrasonographic verification protocol

A trained anesthesiologist investigator with experience in more than 40 cases of ultrasound confirmation of gastric tubes would perform the ultrasound examination. In the present study a portable ultrasound device Sonosite Edge II Fujifilm Sonosite Inc., Bothell WA USA will be utilized. The device will be equipped with a linear probe of 10-5 MHz and a curved probe of 8-3 MHz.

The child will be placed in a supine with their head facing upward in a sniffing position. The investigator will employ a standardized method by positioning the linear probe horizontally on the front region of the neck, specifically focusing on the portion of the esophagus. Once the feeding tube is identified the probe will be rotated 90 degrees and an attempt will be made to visualize the FT in a longitudinal view. Next, a curved probe will be positioned in the subxiphoid area to acquire a visual portion of the stomach. The probe will be directed towards the left upper abdominal quadrant and angled towards the left subcostal area.

Radiographic confirmation Protocol

All patientswill be ultimately evaluated via direct radiography. X-rays of the chestwill be regarded as the gold standard method.

Primary outcome-** The primary outcome of the study is the accuracy of ultrasonography as determined by the sensitivity and specificity of correctly identifying feeding tubes in pediatric patients as compared with Chest X ray.

Secondary outcome **–**The secondary outcome of the study is the time required to confirm the FT position from the time point of feeding tube insertion.

Definition

Positive USG examination

·        If the FT is observed as a hyperechogenic circle posterior to the left thyroid lobe and adjacent to the trachea as well as a hyperechogenic point in the stomach the USG examination will be deemed positive.

·     Dynamic fogging test- If the NG tube cannot be verified at the subxiphoid region a pine-tipped syringe will be used to administer a mixture of 1 cc per kg of air. Evaluation by the US will be then repeated. At the tip of the NG tube, US operators should watch for dynamic fogging in the stomach.

·     Time of assessment- Total duration from feeding tube insertion to confirmation of FT position.

Sample size calculation

The sample size calculation was based on a previous study by Teo et al. and Yilderium et al. with a sensitivity of 91 percent. Assuming an alpha error of 5 percent and statistical power of 80 percent we would need to enroll 94 subjects. Considering a dropout rate of 10 percent, the final sample size would be 104 patients. The sample size was calculated using R version 4.3.3 with MKMisc packages.

Statistics analysis

Data will be analyzed using STATA 14 software and presented in mean SD and frequency percent. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy will be presented with a 95 percent confidence interval. We will do a subgroup analysis to compare the findings of various levels of experience. Other appropriate statistical analyses will be carried out as per the requirement of the objective at the time of analysis. For all final comparisons, a p-value less than or equal to 0.05 will be considered statistically significant.