Increased Precision and Safety in Spinal Tap with PASS – An Ultrasound-Guided Lumbar Puncture Procedure

PASS (Point-Assisted Spinal Sonography), an ultrasound-guided lumbar puncture device from Chula doctors and engineers, helps increase the precision and confidence in spinal tap procedures while reducing risks and pain for patients.

Nobody wants to get jabbed repeatedly with a needle, especially when that needle is poking into the spinal cord.  All of us pray that the doctor can do it precisely in one fell swoop. However, mistakes happen depending on the doctor’s experience and expertise, as well as the physical conditions of the patient.

“A mistake in performing lumbar puncture (LP)  could affect the patient’s entire life! We don’t want to see patients suffering from pain and being harmed by our treatment,” Associate Professor Ketchada Uerpairojkit, M.D., Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, discusses the motivation to design the ultrasound-guided lumbar puncture device or PASS — Point-Assisted Spinal Sonography to raise the standard of care and safety for patients.

This innovation is a collaboration between the Faculties of Medicine and Engineering of Chulalongkorn University which include, apart from  Assoc. Prof. Dr. Ketchada, Associate Professor Dr. Wirinaree  Kampitak, and Dr. Banjobphorn Songthammawat from the Department of Anesthesiology, Faculty of Medicine, Chula, Assistant Professor Dr. Werayut Srituravanich, and Mr. Thiwa Nantapak from the Department of Mechanical Engineering, Faculty of Engineering, Chula.

The Origin of PASSS Innovation

Assoc. Prof. Dr. Ketchada explained that lumbar puncture (LP) or spinal tap is a method used in reducing pain during an operation, also known as epidural or spinal block.  It sedates the sensory nerves by anesthesia through the spinal canal, causing the patient’s body to be immobile and numb from the abdomen to the toes. This method is often used for surgical procedures such as cesarean section, surgery on the uterus, ovaries, hernia, hip, knee, and leg, or blocking the pain from natural childbirth, etc.  Moreover, LP is also used in chemotherapy, and diagnosis of leukemia, meningitis, and so on.

“An anesthesiologist will have the patient lying down in the fetus position, or sitting and bending forward so that he/she can palpate the patient’s spine to find the spot to insert the needle and give a regional block so that the patient does not feel pain during and after surgery. This reduces the use of anesthetics. The patient will feel comfortable during surgery, which is safer and less costly than general anesthesia. It will also reduce the spread of respiratory pathogens, including COVID-19.  Anesthesia can also be given in combination with regional block to accelerate post-op recovery and early discharge.”

Generally, to administer LP, the doctor needs to palpate the iliac crest, and the spine while gauging the direction and depth of insertion of the needle into the spinal canal. Approximating the lumbar spinal canal at levels 2 – 3 or 3 – 4 may not be successful every time.

“Performing spinal tap may not be successful in a single try.  Patients may have to suffer multiple attempts before the procedure is complete as the spinal canal is quite deep and obscured by bones, tissues, and ligaments, so the needle must pass through a small opening that is invisible to the eye.”

According to Assoc. Prof. Dr. Ketchada, the chance of error in LP is approximately 10-50 percent depending on the experience and expertise of the anesthesiologist, as well as the age and physical conditions of patients that may add obstacles to the procedure, like obesity, abnormal spinal curvature, or spinal stenosis.

“With patients being overweight, having spinal deformity, spinal stenosis, or spinal fuse, there is a higher risk for failure and a greater chance of hitting the bone or nerves causing excruciating pain for the patients.  Some may have internal bleeding and also the risk of paralysis.”

Therefore, the introduction of ultrasound to help access the spinal canal is one of the factors that increase the likelihood of success, as it allows for accurate visualization of the position, orientation, and depth of the needle.

PASS precisely defines the LP location, increasing patient safety.

The Point-Assisted Spinal Sonography (PASS) is an ultrasound-guided device designed to engage the ultrasound probe that scans for the precise location, degree, and depth of needle penetration into the spinal canal to reduce the chance of the needle hitting the spine and decrease the pain for the patient.

“Practically, the anesthesiologist cannot insert the needle in the best position from the obtained image because the ultrasound probe is blocking the needle’s position, but PASS makes precise needle insertion possible with less chance of the needle hitting the bone or internal vessels,” says Assoc. Prof. Dr. Ketchada.

PASS has two components: a “frame” designed to fit over the ultrasound probe, and a “needle guide slot” to control the direction of the needle to penetrate the spinal canal. The needle guide slot is disposable to prevent infection, but the frame can be disinfected and reused 10 times.

Assoc. Prof. Dr. Ketchada explained the PASS operation as follows:

1. Assemble the sterilized frame and needle guide slot.
2. Put PASS on the ultrasound probe.
3. Perform an ultrasound scan until the spinal canal is visible.
4. Pause the imaging to measure the location and position of LP from the display.
5. Unscrew the ultrasound probe from the PASS frame
6. Insert the needle through the “needle guide slot”, which will manually guide the needle towards the target (instead of drawing a line on the patient’s skin), it will travel through the skin into the subarachnoid space of the spinal cord until the measured depth is reached.
7. Slowly remove the PASS frame. Be careful not to let the needle move.
8. Aspirate the spinal fluid from the puncture point.

PASS and its 4 distinctive designs

PASS is designed to optimize the performance of anesthesiologists when administering epidural, and general practitioners or neurologists who have to diagnose the disease by spinal tap. Assoc. Prof. Dr. Ketchada summarized the four strengths of PASS as follows:

1. Safety – PASS is made of non-toxic, medical-grade resin for medical devices that are light and safe.
2. Ergonomic design – designed to be easy to use with the ultrasound probe.
3. Accessible price – the PASS frame can be reused after sterilization, thus reducing waste and saving costs, but the needle guide slot, which comes in direct contact with the needle is contaminated and must be disposed of.
4. Distribution – Collaboration with ultrasound equipment companies is possible to design a PASS that fits the various models of ultrasound probes. It is easy to produce.  Production capacity can be increased quickly.

However, PASS has some limitations.

“Each brand of ultrasound machine has different probes, so we have to create a model that fits each probe. We also have to calibrate the device to be more precise, since there are still a few errors,” Assoc. Prof. Dr. Ketchada explained.

Chula Piloting the use of PASS for safe treatment.

PASS was a prototype medical device at the International Conference of Anesthesiologists at the end of 2020. Since then, anesthesiologists at King Chulalongkorn Memorial Hospital have been using PASS in difficult cases. It is also used as a pilot training for 6th-year medical students in the Department of Anesthesiology, Faculty of Medicine, by practicing with cadavers.

Currently, the PASS research and development team plans to expand its use into a business context and is supported by Chulalongkorn University Technology Center (UTC).

“The team has already registered with the FDA and applied for a patent since September 2021.  Medgateways has been entrusted with production and development.  PASS is now available for sale at 2,000 baht/set. One pass consists of 1 frame and 10 needle guide slots,” says Assoc. Prof. Dr. Ketchada.

In the future, the team will be producing ultrasound-guided PASS with mobile phones/tablets connection, which will make it even safer and more convenient for doctors to perform the procedure.  Training for medical students and residents in hospitals and centers will also be organized.

“We hope that PASS will provide physicians with a more accurate tool to help patients and help bridge the gap in access to safe treatment in the future,” Assoc. Prof. Dr. Ketchada said.

For more details, please contact Assoc. Prof. Dr. Ketchada Uerpairojkit, Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, Rattanawithayapat Building, 9th Floor, Rama 4 Road, Pathumwan, Bangkok Tel. +66-2256-4000 ext. 60904-9, email: Ketchada.U@chula.ac.th

Hospitals, medical institutions, or companies interested in using PASS to increase the success of spinal taps and reduce the risk to patients can contact Medgateways, manufacturer, and distributor of PASS, 222/113 Teparak Road Bangplee Yai, Bangplee, Samutprakarn 10540, Tel: +668-4754-9493, http://www.medgateways.com/pass. 

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