Intravenous subhypnotic propofol in central pain - A double-blind, placebo-controlled, crossover study

Objective: To validate IV subhypnotic propofol, a gamma-aminobutyric acid A (GABA-A) agonist, as a diagnostic test for central pain. Methods: The efficacy of systemic propofol (0.2 mg/kg IV bolus) was evaluated in a double-blind, placebo-controlled and crossover fashion on both spontaneous ongoing pain and allodynia in 44 patients with chronic central pain of both brain and cord origin. Results: Propofol was significantly superior to the placebo (Intralipid, Kabi Pharmacia) in reducing the intensity of spontaneous ongoing pain for up to 1 hour after the injection: 24 of 44 patients (55%) receiving propofol showed a significant reduction in spontaneous pain, whereas only 6 patients showed this after the placebo. Propofol also significantly reduced the intensity of both mechanical and cold allodynia. In a few cases, only the evoked components were abolished but not the spontaneous pain. In general, the side effects were minimal and consisted mainly of transitory burning upon injection of both propofol and placebo and slight lightheadedness in a few cases. Conclusions: Systemic propofol induces analgesic effects on all studied components of central pain and highlights the key role of GABA modulation in central pain.