Intrathecal (subarachnoid)Drastic Drugs Infusion

Dimitris Papadopoulos MD Fellow Of Interventional Pain Practice (FIPP)

Updated 25 January, 2011

GENERAL

The continuous subarachnoid injection of drastic drugs is a neuromodulation technique. The term “neuromodulation” refers to therapies which stimulate, inhibit or coordinate the activity of neurons or neuronal networks through the electric or chemical change of signal transmission to the nervous system.

WHO ARE CANDIDATES FOR NEUROMODULATORY THERAPIES (1,2,3,11,12)

Neuromodulation therapies are indicated for carefully selected patients suffering from chronic pain
- who are not effectively relieved with pharmacotherapy or other less invasive methods,
- who present considerable drug side-effects,
-  for whom surgery is contra-indicated or is not expected to have satisfactory results
- who are still in pain after surgery
These are reversible therapies. They are applied after a testing period during which the patient has observed significant pain relief. SUBARACHNOID INJECTION OF DRASTIC DRUGS


Description of the method (12)

Subarachnoid injection is performed through a catheter which is placed in the subarachnoid space (between  pia and arachnoid mater of the spinal cord containing cerebrospinal fluid) and is subcutaneously connected with a controlled pump, usually implanted subcutaneously in the abdominal region. In this way, small doses of opioids are delivered straight to the cerebrospinal fluid. This means more effective analgesia and fewer side-effects. It is characteristic that if a patient needs 300 mg of morphine administered per os, s/he needs only 1mg of morphine if administered subarachnoidally. Thus, the opioid side-effects are reduced to the least. If someone needs to start opioids, it is recommended to take the lowest dose.

The pump contains the prescribed drug and records all parameters, such as the infusion rate which can be either stable or fluctuating. The entire implantation procedure is conducted under total anaesthesia. Any change in the dosage and mode of infusion is controlled telemetrically by the therapist physician, with the use of a remote control.

There is also the potential for the patient to deliver small additional drug doses, in cases of pain exacerbation, with safety by using a special remote control. The amount and overall number of these doses during the day are predetermined by the therapist physician.

The outcome of subarachnoid infusion can be pre-evaluated (before the implantation) by administrating  a small amount of drug subarachnoidally with lumbar spinal puncture. As long as the patient experiences significant relief, a subarachnoid infusion system can be implanted.

INDICATIONS (3,5,6,7)

Subarachnoid drug injection is mainly used in the treatment of patients with nociceptive pain. However, it can be also applied to patients with neuropathic pain who do not respond to neurostimulation, to patients to whom neurostimulation is not possible, who are not sufficiently relieved by taking opioids systemically or who experience serious side-effects of opioids.

LITERATURE

1. Lazorthes et al., Handbook Clin Neurol 2006
2. Boswell et al., Pain Phys 2005
3. Oakley. Neurosurg Clin N Am 2003
4. Mannheimer et al. European Heart Journal 2002 (23), 355-370
5. Amann et al. Eur J Vasc Endovasc 2003;26:280-6
6. Krishna Kumar et al. Pain 132 (2007) 179-188
7. North et al., Neurosurg 2005
8. Leg et al. Cochrane Database Syst Rev;3:CD002000
9. De Jongste et al. JACC 1994;23:1592-1957
10. Hautvast et al. American Heart Journal. 1998;136:1114-1120
11. Sanderson et al. Eur Heart J 1994;15:810-814
12. Pain Physician 2009; 12:345-360 • ISSN 1533-3159