Postgrad Med J: first published as 10.1136/pgmj.60.710.897 on 1 December 1984. Downloaded from Postgraduate Medical Journal (December 1984) 60, 897-904 Management of pain with regional analgesia JOHN J. BONICA M.D., D.Sc., F.F.A.R.C.S. Department ofAnesthesiology, University of Washington, Seattle, Washington 98195, U.S.A. Introduction cause of the pain, and in determining the patient's reaction if the Regional analgesia has been used for the manage- pain is eliminated (Bonica, 1953, 1958, ment of acute 1959, 1974). Block of the appropriate nerves helps pain for nearly a century. Local differentiate trigeminal neuralgia from atypical facial analgesia and somatic nerve blocks interrupt noci- neuralgia, neuralgia involving the ceptive input at its source or block nociceptive fibres third division of in peripheral nerves. Blockade also interrupts the trigeminal nerve from glossopharyngeal or vagal afferent limb of abnormal reflex mechanisms that neuralgia, and pain caused by visceral disease from may contribute to the pathogenesis of some pain pain of somatic origin. For example, complete relief syndromes. Moreover, since sympathetic fibres des- of chest or epigastric pain following intercostal nerve tined for somatic structures, particularly the limbs, block at the midaxillary line suggests the pain is of course through somatic spinal nerves, blocking these somatic origin in the chest or abdominal wall, may eliminate the sympathetic hyperactivity that whereas lack of relief suggests it is a pain referred by copyright. often contributes to the pathogenesis of certain pain from viscera (Bonica, 1953). syndromes. Local anaesthetics in low concentration block the unmyelinated C and B fibres and small Prognostic blocks myelinated A delta fibres without blocking somatic Properly applied, certain nerve blocks are used to motor function. On the other hand, in certain predict the effects of prolonged interruption by conditions it may be useful to block somatomotor injection of neurolytic agents or by neurosurgical nerves to relieve severe muscle spasm. By producing section (Bonica, 1953, 1959, 1974). Moreover, prog- one or more of these effects, there is often prompt nostic blocks give the patient an opportunity to pain relief lasting for varying lengths of time experience the numbness and other side effects that depending on the concentration and characteristics of follow surgery or neurolytic block, and help the http://pmj.bmj.com/ the local anaesthetic used. In certain conditions, pain patient decide whether or not to have the procedure. relief outlasts by hours and sometimes days and Although clinical evidence suggests this tool has weeks the transient pharmacological action of local certain limitations in predicting the long term effects anaesthetics. It has been suggested that block of of spinal rhizotomy, it is still useful especially when sensory input for several hours stops the self- prolonged interruption is done in patients with sustaining activity of the neurone pools in the cancer. neuraxis that may be responsible for some chronic on September 30, 2021 by guest. Protected pain states (Bonica, 1953; Melzack and Wall, 1980). Prophylactic blocks Indications for clinical application A variety of nerve blocks are used to prevent pain and the delay of normal functional activity that Regional analgesic techniques can be used as follows trauma, infections or operations. In some diagnostic, prognostic, prophylactic and therapeutic centres, nerve block procedures are considered one of tools (Bonica, 1958, 1974). the most efficient methods to control postoperative or Diagnostic blocks post-traumatic pain. This facilitates earlier functional rehabilitation and helps to prevent complications. Certain nerve blocks are useful to help ascertain Moreover, there is evidence that analgesia achieved specific nociceptive pathways, to differentiate re- with regional block for several days decreases the ferred from local pain, and help determine the incidence of reflex sympathetic dystrophy and other possible mechanisms of chronic pain states. It is also chronic pain syndromes (Bonica, 1953, 1959; useful in the differential diagnosis of the site and Drucken et al., 1959). Postgrad Med J: first published as 10.1136/pgmj.60.710.897 on 1 December 1984. Downloaded from 898 J. J. Bonica Therapeutic blocks haphazard use of this tool, because this may cause more harm than good. Local anaesthesia and nerve blocks using local Another important requisite is that the individual anaesthetics are effective in treating self-limiting must be highly skilled in carrying out the appropriate disease accompanied by severe pain and in breaking procedure and have a thorough knowledge of the up the so-called vicious circle in patients with immediate and long-term effects of the agents used. causalgia and other reflex sympathetic dystrophy, Patients with chronic pain are not good subjects in myofascial syndromes and reflex muscle spasm. It whom to practice nerve blocks. The skill should be provides symptomatic relief to permit other thera- acquired by first observing experts doing the blocks peutic measures or to use as an adjunct to other and performing them under their supervision. In therapeutic modalities. Therapeutic blocks with neu- patients with severe pain, especially complex chronic rolytic agents are usually limited to patients with pain, nerve blocks must be performed carefully with cancer pain, although they may be indicated in meticulous attention to anatomic detail, with utmost selected patients with trigeminal neuralgia, causalgia, gentleness and by using high quality equipment chronic pancreatitis, severe angina pectoris, or other including sharp needles, syringes that are in good chronic disorders. working order and well-fitting, and a block tray adequately stocked with other necessary instruments. It is important to inform the patient what and how Requisites for optimal results the procedure will be done, and what will be In order to obtain good results with nerve blocks, accomplished by it. This information should be the anaesthesiologist or other doctor using these provided during the initial visit and repeated just procedures must assume the responsibility of a prior to the block. If the patient does not realize the physician and not act only as a technician expert at procedure is only to gain information and may inserting needles. Even when acting as a consultant provide only temporary or no relief, he may be skilled in nerve blocks, it is important that the disappointed and may not return for further care. anaesthesiologist has an insight into the pain problem Moreover, the patient should be reassured thatby copyright. (Bonica, 1953, 1958, 1959, 1974). everything will be done to minimize discomfort, that The second requisite is that the physician using this he will be warned before each step ofthe procedure is method must have ample knowledge of various pain carried out, and that he may ask for a brief rest at any syndromes including the mechanisms and nocicep- time he requests it. In addition, if repeated therapeu- tive pathways involved, the pathophysiology and tic blocks are to be done, appropriate sedatives or symptomatology. It is essential to know the advan- narcotics may be used prior and during the block. tages, disadvantages, limitations and complications If the procedure is to be done for diagnostic or of the many therapeutic modalities that may be prognostic purposes depressant drugs should not be applicable for each syndrome. Only with this broad given because the patient must be alert to answer perspective can the best treatment or combination of questions. It is essential to localize exactly the treatments be chosen for each patient with a specific involved nerve or nerves. This can be accomplished http://pmj.bmj.com/ pain problem. by checking the position of the needle with an X-ray Thirdly, the physician must be willing to devote or image intensifier with or without prior injection of the time and effort to examine the patient thoroughly a contrast medium. Moreover, in using diagnostic or and confirm the diagnosis. This is essential even ifthe prognostic blocks three essential principles must be patient is referred by a highly competent colleague adhered to: (1) injecting small (3-4 ml) amounts of who has already made the diagnosis. A detailed solution to avoid diffusion to adjacent segments and history and thorough physical examination not preclude misleading information: (2) no only decision on September 30, 2021 by guest. Protected provide additional information but affords an oppor- should be made until three or more blocks produce tunity to become acquainted with the patient, to consistent responses; and (3) it is best to use local investigate his or her personality and, most impor- anaesthetics of different duration and correlate the tant, to win the confidence of the patient. A careful duration of the block with the duration ofpain relief. neurologic examination provides not only useful Use of "placebo" block may be added to help information, but constitutes a baseline in evaluating determine the diagnosis. the effects of the block. These basic principles apply During and following the block, it is essential to to all patients, particularly those with complex pain assess the results carefully. Observation of the pa- problems. tient's reaction to the insertion of the small needles, Once a tentative diagnosis is made it must be the formation of intracutaneous wheals (for cutane- decided if the blocks are to be used to