THE REFERENCE OF CARDIAC PAIN TO A PHANTOM LEFT ARM

A randomized clinical trial on the effect of a lidocaine patch on shoulder pain relief in laparoscopic cholecystectomy

The incidence of laparoscopy-related shoulder pain reaches 90% in women. We evaluated the effect of lidocaine patch 5% on the shoulder pain after laparoscopic cholecystectomy (LC) in female patients. Total 63 female patients were randomly allocated to patch group (n = 31) and control group (n = 32). Patch group received lidocaine patch 5% and dressing retention tape on both shoulder, and control group received only dressing retention tape. Abdominal and shoulder pains were evaluated with rating on numeric rating scale (0 = no pain and 10 = the worst pain) at baseline and at 30 min, 6 h, 24 h, and 48 h after surgery. There were no significant differences in patient characteristics and operation details. The overall incidence of shoulder pain was significantly lower in patch group than in control group (42% vs. 78%, P = 0.005). The severity of shoulder pain also was significantly reduced in patch group compared to control group at 24 h and 48 h after surgery (P = 0.01 and P = 0.015, respectively). Complications related to lidocaine patch were not found except nausea. Lidocaine patch 5% reduced the incidence and severity of postoperative shoulder pain in female patients undergoing LC without complications.

Referred pain is dependent on sensory input from the periphery: A psychophysical study

Muscle pain can be characterized by local pain and pain referred to distant somatic structures with concomitant cutaneous and deep somatosensory changes. The mechanisms responsible for referred muscle pain are poorly understood. The aim of this study was to study the origin of experimentally-induced referred muscle pain by anaesthetizing the skin overlying the referred pain area and to quantify deep somatosensory changes in the area. Fourteen healthy subjects (mean age = 25.1 years, range 22-34 years) were included in a placebo controlled study consisting of two sessions separated by 1 week. Two stimulation needles were inserted into the right anterior tibial muscle. Electrical stimuli (1Q Hz) were delivered by a computer-controlled constant current stimulator. The intensity required to generate referred pain was determined and the circumference of the referred pain area was marked. At the centre of the area, pressure pain threshold and pinprick perception threshold were determined. Either an anaesthetic cream (EMLA, Astra AB, Sweden) or a placebo cream (Astra AB, Sweden) covered by an occlusive dressing was applied to the marked referred pain area for 90 min. Afterwards, a 600-s stimulation at 150% of the referred pain threshold was induced while the VAS score of referred pain was recorded continuously. Pressure pain threshold and pinprick perception threshold were determined before, during and 5 min after the prolonged stimulation. A significantly lower referred pain visual analogue scale (VAS) score was recorded during the interval from 50 to 150s (p=0.04). The area under the referred pain VAS score vs time curve tended to be lower (22.7%) with the application of skin anaesthetic (p=0.07). The mean referred pain threshold and the mean referred pain area did not differ significantly between the two sessions (p>0.6). No difference was found in pressure pain threshold between the two treatments or between the four recordings during each session (p>0.8). Pinprick perception threshold increased significantly after EML application (p<0.04). Decreased referred pain intensity with application of anaesthetic cream at the referred pain site indicates that referred muscle pain depends on input from the periphery (skin) in humans.