“Sensitization”: Is There a Cure?

Puzzling Pain Conditions: How Philosophy Can Help Us Understand Them

CONTEXT

Pain is a complicated area of inquiry. To progress in our scientific understanding of the topic, it may be useful to learn how other disciplines are grappling with the subject. Philosophy is one discipline actively engaged in trying to understand pain.

OBJECTIVE

We present one philosophical view of pain to help broaden the understanding of pain in those who are trained to look at it from a biomedical perspective.

DISCUSSION

One current philosophical theory of pain is the externalist perceptual theory of pain. This theory states that pain is a form of perception and can be likened to other perceptions, for example, visual, tactile, etc. The way a pain feels can be explained as the relationship between this perception and some bodily damage occurring. and just as other perceptions can be mistaken, such as in a visual illusion, pain can also be inaccurate. We explore how the theory deals with puzzling conditions such as phantom limb pain, complex regional pain syndrome, and allodynia. We contrast this view with a competing theory of pain and briefly consider how these philosophical views may impact clinical medicine.

Subanesthetic ketamine infusion therapy: a retrospective analysis of a novel therapeutic approach to complex regional pain syndrome

Complex Regional Pain Syndrome (CRPS) is a disorder that can be accompanied by severe pain that is often both chronic and resistant to conventional therapy. Harbut and Correll previously reported the successful treatment of a 9-year case of intractable Type I CRPS with an intravenous inpatient infusion of ketamine in an adult female patient.

OBJECTIVE

The purpose of this study was to ascertain if indeed the use of subanesthetic inpatient infusions of ketamine provide meaningful improvements in pain scores, and thus, quality of life, in patients suffering from CRPS. To achieve this objective we focused our analysis on the relief of pain obtained by patients undergoing this novel treatment option developed at Mackay Base Hospital, Queensland, Australia.

METHODS

Case notes of 33 patients whose CRPS pain was treated by the inpatient administration of a continuous subanesthetic intravenous infusion of ketamine were reviewed. The dose and duration of ketamine therapy and the degree and duration of relief obtained were recorded. Notable side effects were also recorded. The degree of relief obtained (immediately after the infusion) was assessed using pre- and posttreatment numeric pain scores. The duration of relief obtained (throughout the follow-up period) was analyzed using a Kaplan-Meier cumulative survival curve analysis.

RESULTS

A total of 33 patients with diagnoses of CRPS who had undergone ketamine treatment at least once were identified. Due to relapse, 12 of 33 patients received a second course of therapy, and two of 33 patients received a third. The degree of relief obtained following the initial course of therapy was impressive (N=33); there was complete pain relief in 25 (76%), partial relief in six (18%), and no relief in two (6%) patients. The degree of relief obtained following repeat therapy (N=12) appeared even better, as all 12 patients who received second courses of treatment experienced complete relief of their CRPS pain. The duration of relief was also impressive, as was the difference between the duration of relief obtained after the first and after the second courses of therapy. In this respect, following the first course of therapy, 54% of 33 individuals remained pain free for >/=3 months and 31% remained pain free for >/=6 months. After the second infusion, 58% of 12 patients experienced relief for >/=1 year, while almost 33% remained pain free for >3 years. The most frequent side effect observed in patients receiving this treatment was a feeling of inebriation. Hallucinations occurred in six patients. Less frequent side effects also included complaints of lightheadedness, dizziness, and nausea. In four patients, an alteration in hepatic enzyme profile was noted; the infusion was terminated and the abnormality resolved thereafter.

CONCLUSION

This retrospective review suggests that limited subanesthetic inpatient infusions of ketamine may offer a promising therapeutic option in the treatment of appropriately selected patients with intractable CRPS. More study is needed to further establish the safety and efficacy of this novel approach.