QUANTITATIVE DETERMINATION OF THE VISCERAL PAIN THRESHOLD IN MAN

Publisher Website
Google Scholar
Abstract
A quantitative method for measurement of visceral pain threshold by hydrostatic distention of the biliary ducts in patients after surgical exploration of the common duct is described. Of 40 volunteers 47% described sharp or colicky pain and the others a dull pain or ache when the threshold was reached. The initial threshold varied from 90 to 800 mm. of water and often rose during 2 wks. to 7 mos. after operation. During 12 hrs. the S.D for the control thresholds varied from [plus or minus]5.1 to [plus or minus]2.6 mm. and the coeff. of variation was 0.67 to 3.82%. Admn. of analgesics caused an elevation of threshold proportional to the potency and dose of the drug and inversely proportional to the initial threshold level. 157 time-action curves showed the following mean peak threshold elevations: morphine 10 mg., 56%; codeine, 60 mg., 12%; dihydromorphinone, 3 mg., 42%; methyldihydromorphinone, 7.5 mg., 46%; methadone, 7.5 mg., 33%; meperidine, 100 mg., 23%; and acetylsalicylic acid, 0.6 g., no elevation. Duration of action varied from 3 hrs. for meperidine to 6 hrs. for methadone. Total analgesic action varied from 168%-hrs. for methadone to 40%-hrs. for codeine. Total analgesic action did not increase in proportion to dosage. Parenteral injn. of placebos did not cause an elevation of threshold. The severity of biliary and small intestinal spasm due to the analgesics was in proportion to their analgesic activity. The peak threshold raising activity for visceral pain occurred earlier than for superficial pain; duration of action was shorter and intensity of analgesia was lower for visceral than for superficial pain. In contrast to integumental pain,salicylates had no effect on visceral pain.