May/June 2007
Volume 3, Issue 3

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Ultrasound Guided Intrathecal Pump Refill: A New and Improved Approach to Intrathecal Delivery Systems

An Original Contribution by Michael S. Slobasky, D.O.

Intrathecal drug delivery systems have been used to deliver very small quantities of medications to the spinal fluid for many years now. Medications — such as morphine, dilaudid, ziconotide, and baclofen — have been used for a variety of conditions to include, but not limited to, intractable pain and spasticity. Intrathecal delivery of these medications minimizes side effects since the total amount of medicine required to achieve efficacy is minimal compared to the oral route.

Depending on the patients dosing and concentration, these pumps need to be refilled with their medications in periodic intervals. The current technique for refilling these pumps involves a template method that is supplied in the refill kit by the manufacturer.

The pump head is accessed by placing a clean needle through sterilized skin, into the filling port which is located in the middle of the pump. The filling port is located by using a specially designed shape template placed on the skin overlying the pump head.

This invasive technique includes a risk of infection, bleeding, and most importantly for this study, subcutaneous/intramuscular injection of medication. Risk of infection is low with and technique as long as sterile procedure is used.

Patient discomfort also is a factor. Depending on patient height, weight and body habitus, accessing the port using the template may become difficult and in turn very uncomfortable for the patient. Some patients may require multiple needle sticks even in the hands of a skillful, experienced physician.

The purpose of this prospective study was to compare the old template technique to accessing intrathecal drug delivery systems with a new ultrasound guided technique.

Methods
Patients at our spine center returned for their required intrathecal pump delivery refill dates. All patients that needed intrathecal refills were included in the study, regardless of height, weight, body habitus, and manufacturer of pump. Both Codman and Medtronic manufacturers were included.

Patients were most frequently placed in the prone position on a regular examination table. The template was used for comparison with the position assumed to be accurate for the port location was marked using the old template technique. After this was marked, a 2D GE logic book XP ultrasound machine was used to locate the port.

The probe was placed in the region of the pump, a modest amount of gel was applied and the port was identified using an intersection of both the longitudinal and transverse views under ultrasound guidance. Access was confirmed by the withdrawal of remaining medication from the pump.

Pictures were taken for the record-see figure 1 and 2. A recording was made of how many needle sticks were required to access the port using the ultrasound marked location. The distance was measured in cm.between the original templated mark and the US mark. The patient’s height and weight was also recorded.

Results
Thirty-three ultrasound guided injections were performed. Eighteen of the injections were females and 15 were males. Patient’s heights ranged from 60 inches to 74 inches with an average of 67.6 inches. Weights ranged from 125 lbs. to 320 lbs. with an average of 211.8. Out of the 33 refills that were required, a total of 35 attempts under ultrasound guidance were required. There were two missed injections in the entire group. This gives and accuracy rating with ultrasound guidance of 94%. The distance from the templated location to ultra-sound location ranged from 0cm to 3cm with and average of .78cm.

Discussion
Ultrasound guidance is an improved way to perform intrathecal pump delivery system refills. Whether the patient comes in each month or every three months, U.S. guidance gives more accuracy to the pump refill process. In addition to lowering bleeding and infection risk with multiple needle stick attempts, the patient satisfaction rating is dramatically higher in the patients who underwent U.S. guided injections.

The patients used in this study are all patients that have had their pumps refilled in the past using the templated method. Many of them have had numerous attempts at port access during a single injection. Having to only stick the patient one time leads to increased patient satisfaction, improved efficiency, and decreased patient anxiety.

There were two missed attempts during the U.S. guided injection. We attribute this to the patient’s movement while on the exam table after ultrasound marked location was already identified and to very difficult pump location (slanted/ oblique position).

Conclusion
From this study, it is obvious that U.S. guided intrathecal pump delivery refills are superior to the old templated method. Regardless of patient weight, height and body habitus, the ultrasound technique is both patient and practitioner preferable to using the template.