Caudal Epidural Block Simulator

Sean Graves, Emily Lickert, Victoria Turchick, Maxwell Lohss, Brandon Barber, Daniel Yates, Dr. Mihaela Visoiu M.D.

A ultrasound phantom medical trainer was created for medical students and other physicians to practice performing a caudal epidural block on a neonatal baby, a procedure performed on patients to anaesthetize them prior to surgery or for pain relief.

During the project's duration, I have utilized the following skills:

3D printing
Molding and casting
High resolution sketching
Vacuum forming
Rapid prototyping

Overview

A caudal epidural block is a commonly used technique for surgical anesthesia in children and chronic pain management in adults. It is performed by inserting a needle through the sacral hiatus to gain entrance into the sacral epidural space. The blind technique, which consists of palpating the sacral processes to situate needle location, has a high failure rate. The rate is even higher for neonates. To mitigate the risk, clinicians have begun to use ultrasound as a means of guiding needle insertion.

Objectives

Create a trainer that can act as a simulator for this procedure
Clinicians who specialize in ultrasound can navigate the procedure using the trainer
Design essentials:
- Life-like haptic feedback
- High ultrasound fidelity
- Accurate anatomy
- Portable

Ideation

During the early phase of the project, we discussed two important topics. Firstly, what anatomy is pertinent to this procedure and is necessary in the trainer (i.e. spine, dural sac, epidural space). Secondly, what features shall the trainer have (i.e. interchangeable anatomy, replaceable needle insertion pad, drainage system). We consulted the UPMC 3D Print Lab throughout the design process.

Materials Testing

We conducted materials testing to determine what would simulate human skin and fat tissue in terms of haptic feedback and ultrasound fidelity. Variables included varieties of silicone, varieties of scatterers like cellulose and graphite, and the viscosity of the materials itself.

When administering a caudal epidural block, physicians often feel a "pop" when inserting the needle into the epidural space. This haptic feedback is important during the procedure. Additionally, it is important that the physician avoids puncturing the dural sac. If punctured, a cerebrospinal fluid leak occurs. This needed to be simulated as well in the trainer. Using a flexible resin 3D printer, we created an endcap that simulates the entrance to the epidural space and the dural sac (the tube containing red liquid). A user of the trainer will be able to tell if they punctured the dural sac by discovering red liquid upon aspiration.

With the assistance of the UPMC 3D Print Lab, a neonatal spine model was created. Pictured above is the spine with dialysis tubing threaded through it (simulating the epidural space). The endcap was attached to the tubing and placed at the sacral entrance.

Prototyping and Assembly

Assembly of the trainer started with created a 3D printed model of the trainer shape, known as a "plug" or a "buck". From there, we vacuum formed the buck to created the mold. We paint a silicone skin layer, suspend the spinal apparatus in the mold, and pour silicone fat tissue into the mold. Once the silicone is cured, we removed the mold. Prototypes were subjected to ultrasound testing from teammates and clinicians from UPMC Children's Hospital.

Final Iteration

Successes:

Life-like haptic feedback
Portable
Spine, epidural space, and dural sac were differentiable under ultrasound

Future Directions

Replace dialysis tubing with a new material
Distribute to clinics, medical schools, and other training facilities
Determine if those who practice on the trainer decrease the likelihood of error during a live procedure

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