Implantable Morphine Pumps:
A System for Delivering Pain Medication Directly to the Spinal Cord

Note: I do not have a morphine pump of my own. My only experience with them are the trial injections I have had lately; I'm now awaiting insurance approval for implantation of the morphine pump. This page is a synthesis of the research I have done, but I do not have personal experience with this device.

One way of controlling chronic pain is to implant a medication pump inside the body. Much smaller dosages of morphine are needed when it is delivered directly to the spinal cord. As you can see, the pump itself is inserted under the skin in the flank area. A catheter (tube) runs from the pump to the spinal cord. Although it is not obvious in this image, the catheter actually delivers medication to the spinal cord in the area of the 12th thoracic vertebra (2/3rds of the way down your back). Anatomically, the "spinal cord" ends near this vertebra; beyond this point the nerves continue down the spinal column in fairly discrete bundles, exiting at their appropriate locations. This is an important thing to realize. Many people who have heard of morphine pump implantation for pain relief have a mental image of a catheter delivering pain medication "directly to the pain site", this is not the case. The anatomy and physiology of the central nervous system (spinal cord + brain) generally limit the action of morphine to the central nervous system itself. Morphine taken orally or injected into a limb is dispersed throughout the entire body. The concentration in your big toe is the same as it is in your central nervous system. Since the main place the morphine works to kill pain is the central nervous system (spinal cord and brain), the morphine in the rest of your body is wasted, putting extra stress on your liver, making your head foggy, etc. The upshot is that morphine from an implanted pump deadens the lumbar pain-conducting nerves in a specific area at the lower end of your spinal cord so that you don't have to take huge doses to saturate your whole body.
 
 

Above is the pumping device with its associated morphine reservoir, refill site, dose controller, battery, and connections. This device is roughly 1" by 3" (about the size of a can of chewing tobacco). The size an placement of these pumps vary. Some are placed on the side of the stomach, others rest upon the lower ribs (I assume these would be smaller...). Morphine can be administered gradually or in pulses at various times of the day. Some pumps are controlled by the patient, either by hand-held radio devices or by buttons accessed by pushing on the overlying skin. The reservoirs are refilled hypodermically every few weeks.

The tube which delivers the morphine can be implanted just outside the spinal cord or it can be buried in the spinal cord. A tube which delivers morphine to the outside of the spinal cord requires 10 times as much morphine as does a tube delivering morphine to the inside of the spinal cord. The disadvantage of inserting a tube into the spinal cord is that the risk of spinal cord infection is much higher. Diseases such as meningitis and arachnoiditis are small but distinct possibilities. These pumps are usually recommended and installed by neurosurgeons at pain management centers. When the pain management center decides you are a good candidate, they then do some test injections. These injections deliver morphine to the site where the tube is to be implanted. If you respond well to the test injections, they generally proceed with pump implantation.

I underwent a trial spinal injection of morphine in December, 1999. It did reduce the pain markedly, but not enough to get me out of bed more than 1/2 hour per day. Significant side effects I suffered were nausea, itching, and urine retention; I am told these side effects diminish with prolonged use of spinal morphine. My experiences with spinal morphine were not good enough to make it a more appealing option than SI joint fusion.

For some individuals, implanted morphine pumps will not be a permanent fix. Eventually these patient may enough tolerance to the morphine that the pump will have to be removed. For other patients, tolerance is less of an issue, and pain control can last for years or even a lifetime.