Continuous Lumbar Epidural Infusion of Steroid
Lumbar epidural corticosteroid injections have been the treatment of choice in treating a variety of low back conditions, including radiculopathy, for over 50 years. Recent improvements in technique utilizing fluoroscopy with use of a contrast medium, in conjunction with understanding of potential additional risk factors with the procedure,1 have served to both improve efficacy and reduce complications. Unfortunately, despite these ad-vances, there remain several pitfalls with the procedure.
One potential pitfall of therapeutic epidural steroid injections (ESIs) may involve the rapid re-uptake of medication within the epidural space. Over the years of performing ESIs, I have noticed in some cases the contrast may be com-pletely reabsorbed within several minutes of being injected within the epidural space. This being the case, one could postulate the same mechanism of rapid re-absorption takes place with the medication being utilized for the epidural, namely the therapeutic corticosteroid.
This may explain why many physicians I have met over the years believe particulate steroids may be more effective then more water-soluble steroids. The particulates in the steroid may not get reabsorbed as quickly and, by “sticking around” the suspect segment, may give a more timed release of the medication to the inflamed site. Whereas, the more water-soluble, smaller particulate steroid is completely reabsorbed into the bloodstream within minutes of being injected into the epidural space. I have talked personally with several spine surgeons over the years who have seen first hand these steroid particulates used in epidurals when operating on the spine. Unfortunately, I do not know of a study that compares the “efficacy” of utilizing certain steroid preparations over others. Some physicians believe more water-soluble steroids are as effective as more particulate steroids. Some do not. There may be, however, a difference with respect to safety of which steroid is used. Derby et al demonstrated in his recent study1 that, when compared to other particulate steroid solutions, dexamethasone phos-phate had particle size smaller than red blood cells, had the least tendency to aggregate, and the lowest density. These characteristics should significantly reduce the risk of an embolic infarct should intra-arterial injection occur.
Although some of the particulate may “stick around” in the epidural space, the majority is most likely reabsorbed rather quickly, just as the contrast is. This being the case, it may explain in part, why ESIs are not equally effective on all patients. Some patients get no relief, some get partial relief (i.e. 20% better after two ESIs), some get transient relief (i.e. 90% better for three weeks, but back to baseline by week 4), and some get complete relief after 1-3 ESIs. It may be that patients who have a more rapid reabsorption of the steroid may not respond as favorably as those patients who have a slower reabsorption.
What if a more prolonged, continuous infusion of the steroid to the inflammed segment were administered via an indwelling epidural catheter using an infusion pump? Would the patient achieve a greater and more prolonged clinical response versus a single bolus ESI? This is the premise behind the continuous infusion of lumbar epidural corticosteroid to reduce inflammation and pain using the Infusion Catheter Epidural (ICE) (see Figure 1). Prior to further discussion, I believe a short review of the scientific literature would be indicated.
Review of Literature
There have been several studies over the years that have studied continuous infusion of medications for treatment of radiculopathy. In a recent study by Pasqualucci et al,2 one hundred and forty one patients were involved in a clinical trial in which continuous infusion of anesthetic and corticosteroid utilizing an epidural catheter was compared to single bolus injections for treatment of cervical radiculopathy. “The results of this randomized study show a statistically significant efficacy of the treatment of cervicobrachial pain with epidural local anesthetic plus corticosteroids in continuous infusion rather than in single injections, in patients with chronic pain who did not respond to conservative therapies.” Worth noting, the epidural catheter remained in place, on average, for 24.23 +/- 4.82 days in those chronic patients. Six month follow up occurred in this study. Patients received on average 320mg of methylprednisilone over 30 days. No significant complications were reported in the study.
In another clinical trial, Kim et al assessed 46 patients with lumbago and sciatica using continuous epidural block with steroids and local anesthetics using an epidural catheter connected to a multiday infusor, with an infusion rate of 1 ml/hr.3 At the time of discharge, 69.5% of all cases showed excellent or good results. The catheter was removed after 1-2 weeks, on average. Their conclusion was “continuous epidural block is simple and safe in the treatment of lumbago and sciatica, especially in acute phase.” Once again, no significant complications were cited.
Pauza et al, also studied treating radiculopathy with an indwelling lumbar epidural catheter and infusion pump.4 There was no patient morbidity or mortality associated with this treatment. Dr. Pauza noted that “safe and effective treatment of lower extremity radiculopathy may be obtained with this new method.” Two patients in the study had previously experienced brief significant relief with prior transforaminal injections of lidocaine and corticosteroid, but failed to experience sustained relief. In this study, however, they experienced appreciable benefit with an indwelling catheter. In conclusion, Dr. Pauza states,” While affording satisfactory symptom relief with comparatively few surgical facility encounters, administering corticosteroid through an indwelling epidural catheter over three days may be a viable treatment option for radicular pain.” Once again, no significant complications were cited.
Another study looked at continuous epidural block for cervicogenic headache.5 In this study by. HE Ming-Wei et al, a retrospective analysis of 37 patients was performed to investigate the safety and efficacy of a continuous cervical epidural block utilizing a combination of dexamethasone, lidocaine, and saline for 3-4 weeks. Patients received approximately 1mg of dexamethasone per day. Epidural catheters were placed into the cervical epidural space under fluoroscopic or CT guidance utilizing a contrast medium for verification. The catheter was then hooked up to an infusion pump with a flow rate of 5ml/hour over a 3-4 week period. The catheter was removed after 3-4 weeks of treatment. In addition, triamcinolone acetomide 5mg was administered once weekly during this 3-4 period. This retrospective study demonstrated that the continuous epidural administration of corticosteroids and anesthetic is effective and can control chronic cervicogenic headache for at least 6 months. No corticosteroid related adverse events were reported.