QUANTITATIVE DETERMINATIONOF THE VISCERAL PAIN

The development of synthetic analgesics and derivatives of morphine has focused much attention on analgesic testing methods (1). Goetzl, Burrill and Ivy in 1943 abstracted from the literature 75 different methods of quantitative measurement of the pain threshold (2). Pain producing stimuli were divided into mechanical, thermal, chemical and electrical, and all have been used on experimental animals as well as human volunteers. These various stimuli have been applied only to integumental structures, such as skin, lips, teeth and cornea (3, 4). It is generally recognized that visceral pain is a different sensation, elicited only by a special set of stimuli and mediated to the central nervous system through different pathways (5). Little work has been done in the field of visceral algesimetry. Our present evaluation of the effectiveness of various analgesic drugs is based partly on clinical impressions and partly on the assumption that an analysis of response to superficial pain provides an evaluation which also holds true for "deep" or visceral pain (6, 7). Many of the notorious difficulties of integumental pain threshold determination apply equally to visceral pain. Added to these is the obvious difficulty of inaccessibility of visceral organs. Furthermore, viscera do not respond to the more easily quantitated thermal and electrical stimuli. They respond to only one special mechanical stimulus, that of stretch. From available data it is apparent that visceral pain responses, when obtained, vary a great deal more in intensity, quality and localization than pain responses from integumental structures. In spite of this, a number of valuable investigations has been made concerning localization of pain produced by distention of various portions of the gastro-intestinal tract with balloons. Quantitative studies of deep analgesia were conducted by Wolff, Hardy and Goodell (6) and Harrison and Bigelow (7) using the method of Lewis, Pickering and Rothschild (8) by which pain is produced by the rhythmic contraction of ischemic muscle of the forearm. From these studies it was concluded that the effects of analgesics on deep pain are similar to those on superficial pain. The threshold raising effects of narcotics on visceral pain were noted in trained dogs by Yonkman (9). Wolff, Hardy, and Goodell have studied qualitative effects of opiates on visceral pain in man by distending balloons in the duodenum for 40 minutes (6). The gall bladder and biliary tract, though ordinarily inaccessible, become a fertile region for visceral pain studies after surgical drainage and intubation of any portion of this system. Localization of referred pain from the gall bladder has been studied by distending this organ during cholecystectomy (10, 11), by distending the gall bladder and common bile duct during abdominal operations under local anesthesia or after general anesthesia had worn off (12), and by faradic stimulation of the common bile duct through an electrode incorporated in a common duct catheter (13). Layne and Bergh studied the duration of biliary pain as related to biliary spasm by increasing the intrabiliary pressure with saline solution through a common duct tube (14), and White using the same technique investigated the effect of splanchnicectomy on biliary pain ( 15 ). McGowan and associates observed intrabiliary pain and pressures in patients after choledochostomy by connecting the T-tube in the common bile duct to a manometric system filled with sterile saline solution (16, 17). From these studies they evolved criteria for removal of the T-tube. One of