Low dose epidural morphine does not affect non-nociceptive spinal reflexes in patients with postoperative pain.
In order to determine the selectivity of the antinociceptive effect of epidural morphine, the electrophysiological features of a monosynaptic reflex were investigated before and after epidural morphine (2-3 mg) required for pain relief, in 4 patients suffering from postoperative pain. The reflex tested was the H reflex from the soleus muscle. Not only the classical Hmax/Mmax ratio, but also the threshold and the slope of the rising phase of the recruitment curve of H and M responses were analyzed. It was found that epidural morphine did not change significantly any of these parameters, at least during the 60 min post-injection period. By contrast, as usually observed clinically, epidural morphine produced an onset of pain relief by the 25th-30th min following injection. These data support the hypothesis that epidural morphine produced a 'selective spinal analgesia in man.'
Willer
Jean Claude
JC
Lab. Clinical Neurophysiology, Fac. Méd, Saint-Antoine, 75571 Paris Cedex 12 France Dept. of Anesthesiology, Hôpital Rothschild, 75012 ParisFrance.
Bergeret
Sabine
S
De Broucker
Thomas
T
Gaudy
Jean-Henri
JH
D000767:Anesthesia, Epidural; D006801:Humans; D009020:Morphine / Q000008:administration & dosage* / Q000627:therapeutic use; D010149:Postoperative Pain / Q000188:drug therapy* / Q000503:physiopathology; D012023:Reflex, Monosynaptic / Q000187:drug effects*
D009020:Morphine