Br. J. Anaesth. (1975), 47,113
THE MANAGEMENT OF POSTOPERATIVE PAIN P. G. M. WALLACE AND W. NORMS
Incidence and severity of postoperative pain. Pain after operation is largely a result of direct trauma caused to tissues by surgery, but may be further aggravated by associated reflex muscular spasm or visceral distension. It is of two characteristic types: a dull steady pain at rest, and a more severe stabbing pain associated with movement. The latter is more distressing to the patient and is also much more difficult to relieve adequately. Postoperative pain is a self-limiting phenomenon, most severe during the first day following surgery, diminishing over the next 24 hr, and minimal after P.
G.
M.
WALLACE, M.B.,
CH.B.,
D. OBST., R.C.O.G.,
F.F.A.R.C.S.; W. NORRIS, M.D., F.F.A.R.c.s.; Division of Anaesthesia, Royal Infirmary, Glasgow G4 OSF.
3 or 4 days. It is most marked after operations in the upper abdomen and thorax with decreasing severity in lower abdominal operations, herniorrhaphy and surgery on head, neck and limbs (Parkhouse, Lambrechts and Simpson, 1961; Loan and Morrison, 1967). It does not invariably follow surgery, however, and even after thoracic or abdominal operations about 20% of patients may not complain of significant pain (Papper, Brodie and Rovenstine, 1952). Many other factors affect the incidence and severity of postoperative pain. In the elderly or the very young, analgesic requirements appear to be reduced (Forrest, 1968; Swafford and Allan, 1968), but there is litde difference between the sexes. Personality variations do contribute greatly however. Stable patients with low neuroticism may be expected to suffer less from postoperative pain than highly neurotic patients (Parbrook, Steel and Dalrymple, 1973; Dalrymple, Parbrook and Steel, 1973). Many patients will defend themselves against the normal psychological stress of surgery by denial, failing realistically to face the situation and its implications. Patients with this personality pattern can be expected to suffer more and have poorer response to therapy in the period after operation than those who admit to anxiety (Quimby, 1968). Beecher (1959) has described two components of pain: the initial stimulus, and the psychological processing of this sensation—the reaction component. Although the stimulus may be constant in regard to the number of pain endings injured, the degree of pain experienced varies with the individual and occasion. The suffering experienced is dependent on the reaction component, which differs between individuals due to characteristics such as personality and previous conditioning, and more significantly in each individual with changing emotion, mood and situation (Beecher, 1956). The fact that placebos may relieve severe pain in 35% of patients, and that this action will vary with the presence of anxiety (Beecher, 1962, 1969), further emphasizes that emotion may alter the severity of pain experienced.
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"For all the happiness mankind can gain, is not in pleasure, but in rest from pain." John Dryden (1631-1701). The past century has seen revolutionary changes in anaesthesia during the intraoperative period. However, most patients who benefit from contemporary anaesthetic practice face postoperative pain relief by methods which have changed little since the 19th century. The most common treatment for postoperative pain remains a standard intramuscular dose of an opiate, administered at the discretion of a nurse, on demand by a patient whose pain tolerance has been exceeded. This therapeutic programme has not remained in practice because of its overwhelming success. Recent work suggests that some 40% of patients complain of inadequate pain relief following all but minor surgery (Morrison, Loan and Dundee, 1971; Keeri-Szanto and Heaman, 1972). Over 50% of a group of patients who had undergone upper abdominal surgery and "on demand" narcotic analgesia classified their pain as "very unpleasant indeed; I would be very upset if I had to go through this again" (Cronin, Redfern and Utting, 1973). This is a chillingly euphemistic indictment of the neglect which patients suffer in the period after an operation.
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The importance of pain relief. Although postoperative pain demands relief on humanitarian grounds alone, in many cases treatment also reduces significantly physical morbidity following operation. Patients with upper abdominal wounds have the most severe postoperative pain and it has long been recognized that they suffer from an increased incidence of pulmonary complications after surgery (Pooler, 1949; Palmer, 1967; Collins, Darke and Knowelden, 1968). They are frightened to move, to take deep breaths, or to cough and expectorate secretions, for fear of aggravating their pain. Respiration is shallow and grunting, and reflex abdominal muscle spasm holds the chest in an expiratory pattern with a small tidal ventilation at low lung volume. Vital capacity may be reduced by 70% (Churchill and McNeill, 1927; Bromage, 1955) and functional residual capacity, peak expiratory flow rate and timed forced expiratory volume are also reduced. Even without hypoventilation or obvious radiological abnormalities in the lungs, hypoxaemia may follow surgery. Diament and Palmer (1966) showed that this hypoxaemia was worst after upper abdominal surgery, less after
lower abdominal surgery, and not significant after non-abdominal surgery. Although greatest in the early postoperative period, it is still present 5 days following upper abdominal surgery (Knudson, 1970; Alexander et al., 1973). The presence of pain plays a considerable part in the aetiology of this hypoxaemia (Spence and Alexander, 1971). Relief of pain may cause improvement of such pulmonary dysfunction. By abolishing pain following upper abdominal surgery, with extradural blockade, Simpson et al. (1961) and Bromage (1967) obtained significant improvements in vital capacity. An increase in arterial oxygen tension during the period of postoperative hypoxaemia may also result from pain relief with extradural spinal blockade (Muneyuki et al., 1968; Spence and Smith, 1971). Postoperative lung complications will not only be reduced by improvement in ventilatory function, but the mobility encouraged in patients by pain relief will also reduce the incidence of venous thrombosis and subsequent pulmonary emboli. In addition, adequate pain relief will not discourage the patient from further surgery in future, and will minimize possible misconceptions held by the public concerning routine surgical procedures. MANAGEMENT
The management of postoperative pain is not restricted to treatment only after operation. A considerable amount can be done to minimize the pain following surgery by sensible management of the patient preoperatively and during anaesthesia itself. Prophylaxis. Psychological. The patient who is calm and who has gained an understanding of and confidence in his medical treatment through personal contact and relationship with his medical supervisors, may face the postoperative period with optimism and equanimity. Enthusiastic personal preparation before operation is of the greatest importance, and has been shown to have a marked beneficial effect on postoperative progress. Egbert et al. (1964) explained to their patients the implications of their surgery and anaesthesia. They were informed of the pain to expect, that its presence was normal, and that they would receive treatment if required. Deep breathing and coughing techniques were taught and in the period following surgery their doctors visited,
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The recognition and assessment o} pain. Pain is such a subjective experience that it is extremely difficult to convey or assess its severity. In clinical practice Bishop's (1959) definition that "pain is what the subject says hurts" allows recognition and treatment after operation in the large majority of patients. Attempts to quantify the experience, however, are much more difficult. In clinical pain, two basic approaches are possible: the introspective method, in which the patient or a trained observer may attempt to assess pain; or the behaviourist method, in which some physical parameter which is altered in the presence of pain is objectively measured, the changes being correlated with the severity of pain (Loan and Dundee, 1967). Thus, changes in pulmonary function tests following upper abdominal surgery have been studied extensively, as a fall in vital capacity (VC) associated with pain, and an improvement with analgesia (Bromage, 1955; Masson, 1962; Parkhouse and Holmes, 1963). In the mechanically ventilated postoperative patient who is unable to communicate or make skeletal movements, autonomic responses—most commonly cardiovascular changes or sweating—may be used to recognize the presence of pain (Campbell, 1967).
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THE MANAGEMENT OF POSTOPERATIVE PAIN
The relief of flatulence, urinary retention, nausea and vomiting, and the immobilization of fractures, will help to raise the patient's threshold to his primary wound pain as well as remove a specific cause of complaint. Lack of sleep, or fear of the unfamiliar hospital environment, may also lower tolerance to pain. Minor discomforts such as i.v. infusions, intragastric tubes, or frequent record-taking may become greatly resented and concentrate the patient's mind on his pain and suffering. Careful attention to minimize these apparently small points can be rewarding. TREATMENT OF PAIN
Relief from pain may be obtained by various therapeutic methods: (1) Parenteral and oral agents: (a) Analgesics (b) Other drugs (2) Inhalational agents (3) Regional nerve blockade (4)
Other techniques
(1) Parenteral and oral agents. (a) Analgesics. Morphine remains the most common analgesic in use to combat severe pain; no modern substitute has been universally accepted as having overall advantages. Morphine raises the threshold of pain perception, and also alters the mental response to pain. Lasagna and Beecher (1954) consider the optimum i.m. dose to be morphine 10 rag/10 kg body weight, beyond which there is no commensurate increase in analgesia, although side effects are markedly increased. At this dose, morphine can be expected to relieve about 75% of steady wound pain, but less than 50% of the sharp pain of movement (Keats, 1956). The pharmacology of morphine and other potent analgesics has been reviewed elsewhere (Swerdlow, 1967). The individual anaesthetist must examine the evidence on the available drugs (Banister, 1974; Morrison, Loan and Dundee, 1971; Masson, 1967) and decide for himself which analgesic suits his patients' requirements. The most notable side effects of these drugs are respiratory depression, suppression of coughing, nausea and vomiting, and addiction. In the treatment of postoperative pain of about 48 hr duration addiction should not prove troublesome, unless the
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assisted and encouraged the patients and participated in their therapeutic programme. These patients required significantly less narcotic drugs and were discharged home 2 or 3 days earlier than a control group. Roe (1963) and Ulert (1967), similarly using a preoperative period of instruction, encouragement and reassurance continued into the postoperative period, also reduced significantly the amount of narcotics used. In the period following cholecystectomy, Finer (1970) produced significant improvement in the pulmonary function tests of a group of patients by encouraging them during the performance of these manoeuvres. This approach requires understanding, patience, time and effort from the anaesthetist. That anaesthetists do not concentrate sufficiently on establishing this contact has been indicated by Sheffer and Greifenstein (1960), 38% of whose patients could not even remember their anaesthetist, while 26% felt that he had not had an adequate discussion with them. More time spent on this approach will not only be personally satisfying to the anaesthetist, but will bring considerable benefit to the patient. Pharmacological. It has been shown that with prolongation of the period between termination of anaesthesia and the first requirement of postoperative pain relief, the effect of a dose of analgesic is more marked and the total quantity of analgesic in the recovery period is reduced (Swerdlow, Murray and Daw, 1963). It is advantageous, therefore, to design a technique of anaesthesia which will provide residual analgesia in the postoperative period. Preoperative medication with narcotics has little effect on postoperative requirements, but intravenous analgesics during operation will significantly delay the time until analgesia is first required after surgery, and significantly reduce the total quantity of analgesic employed (Dundee et al., 1969; Ferrari, Fuson and Dent, 1969). Similarly, the use of neuroleptanalgesia will provide a prolonged period of postoperative analgesia (Martin et al., 1967). The extension of this technique to "sequential analgesic anaesthesia" (Rifat, 1972), in which the respiratory depression associated with fentanyl analgesia is reversed by pentazocine at the end of operation, may provide pain relief for many hours after surgery. Supportive therapy. In the management of postoperative pain, the main concern is with wound pain and its direct associations. However, the patient may have other indirect causes of suffering for which specific treatment is required.
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patient is undergoing frequent and repeated surgery the period following surgery (Kay, 1973; Knape, when pentazocine is indicated because of low risk 1971). of abuse. The effects on pulmonary function are of The milder analgesics — dihydrocodeine, cogreatest importance, however. In postoperative pain deine, aspirin and paracetamol — should be used relief, it is hoped to strike a compromise above the more widely following minor surgery and for the dose level which provides adequate analgesia but residual discomfort and mild pain in the third or below that at which unacceptable side effects occur. subsequent days after major surgery. The routine postoperative prescription of parenBrief mention should be made of the use of conteral analgesic drugs seldom satisfies this criterion. tinuous i.v. infusion of local analgesic agents to Indeed, a significant fall in arterial oxygen tension provide pain relief (Bartlett and Hutaserani, 1961); has been found in upper abdominal cases following and of the more effective use of ketamine in "subpain relief with narcotics (Muneyuki et al., 1968; dissociative" doses (Yusuke, 1974). Gildea (1968) Hollmen and Saukkonen, 1972). has suggested the use of dilute solutions of ethanol The sensitivity of each subject varies to a given i.v. to provide basal analgesia with psychic condose of narcotic, and the amount required should tentment and useful postoperative calories. All be carefully titrated on an individual basis to pro- methods of continuous i.v. analgesia require vide pain relief at the minimum dose. This is extremely careful supervision to prevent overdosage arranged most easily by incremental small intra- and subsequent toxic side effects. venous doses, say morphine 1-2 mg. Careful addi(b) Other drugs. All patients undergoing surgery .tion can be made to maintain the drug level suffer anxiety to a greater or lesser extent, which just above that required for pain relief, and may have a detrimental effect on the reaction apparatus has been described by which the patient component of pain. Therefore, the recognition of may inject himself automatically as required excessive anxiety requires direct treatment by (Sechzer, 1971). The i.m. route results in much anxiolytic drugs. larger variations in drug effects, but may provide The phenothiazines have been used widely, alone satisfactory analgesia if tailored by observation of and in combination with analgesics, especially in the needs of the individual patient. The inflexible the management of pain of a chronic nature regime of a set dose of analgesic every 6 hr is (Merskey and Hester, 1972). Chlorpromazine, usually inadequate; some patients will be under- promazine and trimeprazine may have analgesic dosed and some overdosed. The effect of a dose of activity (Dundee and Moore, 1961) and methoanalgesic must be carefully assessed and subsequent trimeprazine has been shown to have a potent doses revised accordingly. It is recommended that analgesic effect (Minuck, 1972). Their value to the relief of pain be managed by shortening the time agitated patient after operation is limited by the between injections, rather than by increasing associated depression of cerebral state and cardioindividual dosage. The anaesthetist must ensure vascular function. The benzodiazepines have been that an adequate supply of analgesic is available to reviewed by Dundee and Haslett (1970). They the patient in the period following an operation. appear to have no analgesic effect, but their Although the use of routine narcotic analgesia anxiolytic and amnesic action, with minimal physimay increase postoperative lung dysfunction in cal depression, is safe for use following surgery. comparison to regional blockade, it appears that Chlordiazepoxide and diazepam have each been more frequent doses of narcotic, for example mor- used as the sole therapeutic agent in the treatment phine 10 mg, 4 hourly, do not further increase this of surgical pain (Derrick, Wette and Hill, 1967; dysfunction (Collins, Darke and Knowelden, 1968; Bruce, 1968), and have provided satisfactory relief Alexander, Parikh and Spence, 1973). Thus, anal- in a large majority of patients. This emphasizes gesic drugs may safely be given more frequently the importance of emotional factors in aggravating than in traditional practice, if indicated in the pain experience, and the wider use of these agents is to be recommended to elevate patients' individual patients. Few of the potent analgesics are active reliably pain tolerance and reduce the quantity of potenby mouth, the most useful exceptions being penta- tially toxic narcotic required (Marks, 1967). The zocine, dextromoramide and bezitramide. In suit- use of the newer tranquillizer oxypertine, in comable dosage these drugs offer effective relief of bination with pentazocine (Ward-McQuaid, Chowsevere pain, and have had considerable success in dhury and Zaman, 1973), has been shown similarly
THE MANAGEMENT OF POSTOPERATIVE PAIN
(2) Inhalational analgesic agents. Nitrous oxide. Entonox, the premixed 50% mixture of nitrous oxide and oxygen, is readily available for pain relief in the general hospital environment (Baskett and Bennett, 1971), either from cylinders or from pipeline in more recently built units. Fifty per cent nitrous oxide in oxygen for extended periods is associated with somnolence, and the use of this and higher concentrations in the period after operation (Petrovsky and Yefuni, 1965) is in effect an extension of die anaesthetic state and results in immobility and failure of cooperation. However, lower concentrations of nitrous oxide (20-25%), may provide postoperative analgesia equivalent to routine use of narcotics (Parbrook, Rees and Robertson, 1964), with little sedation. This basal analgesia may be supplemented safely by the use of additional parenteral narcotics. Parbrook (1967, 1972) has described how entonox given directly through an "MC" or "Edinburgh" type oxygen mask will be air-diluted to provide 10-25% nitrous oxide in 25-35% oxygen, depending on gas flow. In upper abdominal cases, or in patients who would be receiving routine oxygen therapy after operation, the substitution of entonox will provide oxygen supplementation and significant analgesia without marked cerebral depression. Marrow depression may occur with prolonged use of nitrous oxide, and its use after surgery must be restricted to 36 or 48 hr. Unpleasant dreams or nausea may also complicate its administration in a minority of cases. Pure entonox may be used on an intermittent basis to cover movement, wound-dressing or physiotherapy. Nitrous oxide has the added advantage of being rapidly effective and excreted. Trichloroethylene and methoxyflurane. These volatile agents have had considerable use in subanaesthetic concentrations for the relief of pain in
labour, the usual levels employed being 0.35% methoxyflurane and 0.50% trichloroethylene. In the postoperative period, attention has been focused on their use as supplementary analgesia during "stir-up" procedures such as wound dressings or physiotherapy. Self administered through drawover vaporizers, they may provide analgesia equivalent to that obtained by the usual doses of narcotics, without significant respiratory depression (Hovell, Masson and Wilson, 1967; Yakaitis, Cooke and Redding, 1972). Their odour is resented by many patients and their prolonged use may cause clouding of conscious level with subsequent "hang over". Methoxyflurane has recently been implicated as a cause of renal dysfunction (Desmond, 1974) but short intermittent low dosage is considered safe (Rosen, Latto and Asscher, 1972). The volatile agents are therefore largely restricted to short intermittent use after surgery to provide extra analgesia, but nitrous oxide deserves considerably more application in the management of postoperative pain. When pain is at its worst and most deleterious to the patient, in the first 36 hr following upper abdominal or thoracic surgery, nitrous oxide with supplementary oxygen may provide convenient, cheap, safe and easily reversed analgesia with little change to basic postoperative practices. (3) Sensory nerve blockade. While the systemic analgesics offer imperfect pain relief, the use of local analgesic agents to block transmission of afferent impulses in sensory nerves may completely abolish pain. (a) Extradural blockade. In the general surgical patient, extradural analgesia has developed slowly despite enthusiastic reviews (Bromage, 1967; Simpson et al., 1961). Following upper abdominal surgery, as has been noted, the patient has most to gain from complete pain relief—he can become mobile, take deep breaths and cough. Extradural blockade offers considerable improvement in respiratory function in these cases (Spence, Smith and Harris, 1970). Complications are rare but may be serious. Dawkins (1969) has made a classic review of over 350 papers; the most notable side effects were accidental dural puncture (2.5%), total spinal analgesia (0.2%), intravascular injection (2.8%), and substantial hypotension (1.8%). Relief of pain following upper abdominal incisions requires analgesia to the nipple line
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to reduce patients' anxiety and their subsequent analgesic requirement. It was hoped that premixed combinations of narcotic and antagonist would provide analgesia without respiratory depression. The analgesic effect itself is also antagonized, however (Campbell, Masson and Norris, 1965), and these mixtures are of little value. The combination of morphine with the respiratory stimulant doxapram (Gupta and Dundee, 1974) promises a reduction in respiratory depression and subsequent pulmonary complications with unaffected analgesia.
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(4) Other techniques. Hypnosis. Finer (1972) has defined hypnosis,
which has long been used in the relief of pain, as "a state of selective concentration and detachment which can be learned under deep muscular and mental relaxation". The hypnotic trance may be divided into three stages (Lauer, 1968). Varying degrees of analgesia may be present in the medium trance, and complete analgesia and amnesia can be provided by deep trance. Probably only about 15-20% of the population can reach the third stage even with skilled practitioners. It is of interest to note that suggestion determines the area of analgesia, and not normal anatomical or physiological considerations. Unlike the other methods of pain control there are no physical toxic side effects but psychiatric disturbances may occur. However, its unreliability compared to chemical analgesia, and a paucity of trained practitioners, make hypnosis a rarely used technique in the management of postoperative pain. Acupuncture. This Chinese medical art is not understood despite considerable present-day interest (Dimond, 1971; Cheng and Ding, 1973). It has been suggested that hypnosis plays a major part, or that the explanation lies in diminution of pain transmission by nocireceptor stimulation of the Gate Control Mechanism. Enthusiasts claim a much higher reliability in the provision of analgesia than by hypnosis alone (Spoerel and Leung, 1974). Its use and investigation is again limited by a lack of suitably trained medical practitioners. Although the above techniques may have limited application for most patients, the care and time that is taken with them in selection, in explanation, and in the provision of a meaningful doctor-patient relationship may be most usefully applied to all management of pain in the period following surgery. CONCLUSION
The increasing involvement of anaesthetists in the recovery area and in the intensive care unit has made them more aware of the inadequacies of present-day attitudes to pain control. With the techniques available at the moment, although they may be far from perfect, it should be possible to reach a much higher standard of management of postoperative pain. The narcotic analgesics will remain the mainstay of treatment for the majority of patients. The amount of these drugs required may be greatly reduced, however, by compassionate psychological support of patients before and after operation,
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(thoracic 4-5) and if benefits are to include mobility, the danger of postural hypotension from concomitant sympathetic blockade must be minimized. Therefore, smaller volumes of analgesic by the thoracic approach are more efficient, by intermittent injection or continuous infusion (Dawkins and Steel, 1971). Lignocaine has been superseded by the longer acting bupivacaine as the agent of choice, although Bromage (1972) suggests that carbonated local analgesics may reduce the incidence of unblocked segments. This technique will provide complete analgesia from the chest down but requires special training and skill, scrupulous asepsis, and vigilant observation during the period of analgesia. Although impracticable for all cases, it is the technique of choice in the period after operation for selected abdominal cases with severe respiratory embarrassment. (b) Intercostal nerve blockade. Sensory transmission from the body wall, from the sternal notch to just above the pubis, may be interrupted by local analgesic blockade of the intercostal nerves serving appropriate dermatomes. Analgesia for any incision in this area may be provided by a block which includes an extra nerve below and above the relevant dermatomes. The techniques of injecting analgesic below each rib have been described by Moore and Bridenbaugh (1962), and Ablondi et al. (1966). There is a danger of pneumothorax but in comparison with extradural blockade there should be little fall in arterial pressure as the block is lateral to the sympathetic outflow. This is particularly advantageous where pain relief is required above the level of thoracic 5 where the cardiac sympathetic nerves lie. Intercostal block has been compared favourably to the opiates in the management of thoracic and upper abdominal cases (Bridenbaugh et al., 1973). The visceral afferent nerves are not affected by the above technique, and patients may continue to complain of deep pain. These visceral sensory inflows may be included with the intercostal nerves by paravertebral block, which involves injection of local analgesic close to the exit of the nerve trunks from the intervertebral foramina. Infiltration of the surgical wound with local analgesic solutions has been largely abandoned due to increased sepsis and delayed healing.
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Bromage, P. R. (1967). Extradural analgesia for pain relief. Br. J. Anaesth., 39, 721. (1972). Unblocked segments in epidural analgesia for relief of pain in labour. Br. J. Anaesth., 44, 676. Bruce, I. S. (1968). Postoperative use of diazepam; in Diazepam in Anaesthesia (eds. Knight, P. F., and Burgess, C G.), p. 89. Bristol: Wright. Campbell, D. (1967). Pain relief in patients on ventilators. Br. J. Anaesth., 39, 736. Masson, A. H. B., and Norris, W. (1965). The clinical evaluation of narcotics and sedative drugs. I I : A re-evaluation of pethidine and pethilorfan. Br. J. Anaesth., 37, 199. Cheng, S. B., and Ding, L. K. (1973). Practical application of acupuncture analgesia. Nature (Lond.), 242, 559. Churchill, E. D., and McNeffl, D. (1927). The reduction of vital capacity following operations. Surg. Gynecol. Obstet., 44, 483. Collins, C. D., Darke, C. S., and Knowelden, J. (1968). Chest complications after upper abdominal surgery: their anticipation and prevention. Br. Med. J., 1, 401. Cronin, M., Redfern, P. A., and Utting, J. E. (1973). Psychometry and postoperative complaints in surgical patients. Br. J. Anaesth., 45, 879. Dalrymple, D. G., Parbrook, G. D., and Steel, D. F. (1973). Factors predisposing to postoperative pain and pulmonary complications. Br. J. Anaesth., 45, 589. Dawkins, C. J. M. (1969). An analysis of the complications of extradural and caudal block. Anaesthesia, 24, 554. Steel, G. C. (1971). Thoracic extradural (epidural) block for upper abdominal surgery. Anaesthesia, 26. 41. REFERENCES Derrick, W. S., Wette, R., and Hill, D. B. (1967). Ablondi, M. A., Ryan, J. F., O'Connell, C. T., and Librium in the recovery room. Anesth. Analg. (Cleve.), Haley, R. H. (1966). Continuous intercostal nerve 46, 171. blocks for postoperative pain relief. Anesth. Analg. Desmond, J. W. (1974). Methoxyflurane nephrotoxicity. (Cleve.), 45, 185. Can. Anaesth. Soc. J., 21, 294. Alexander, J. I., Parikh, R. K., and Spence, A. A. (1973). Diament, M. L., and Palmer, K. N. V. (1966). PostPostoperative analgesia and lung function: a comparioperative changes in gas tensions of arterial blood and son of narcotic analgesic regimens. Br. J. Anaesth., in ventilatory function. Lancet, 2, 180. 45, 346. Spence, A. A., Parikh, R. K., and Stuart, B. (1973). Dimond, E. G. (1971). Acupuncture anesthesia. J.A.M.A., 218, 1558. The role of airway closure in postoperative hypoxDundee, J. W., Brown, S. S., Hamilton, R. C . and aemia. Br. J. Anaesih., 45, 34. McDonell, S. A. (1969). Analgesic supplementation of Banister, E. H. D'A. (1974). Six potent analgesic drugs: light general anaesthesia: a study of its advantages a double blind study in postoperative pain. Anaesusing sequential analysis. Anaesthesia, 24, 52. thesia, 29, 158. Haslett, W. H. K. (1970). The benzodiazepines: Bartlett, E. E., and Hutaserani, O. (1961). Xylocaine for a review of their actions and uses relative to anaesthe relief of postoperative pain. Anesth. Analg. (Cleve.), thetic practice. Br. J. Anaesth., 42, 217. 40, 296. Baskett, P. J. F., and Bennett, J. A. (1971). Pain relief Moore, J. (1961). The myth of phenothiazine in hospital: the more widespread use of nitrous oxide. potentiation. Anaesthesia, 16, 95. Br. Med. J.. 2, 509. Egbert, L. D., Battit, G. E., Welch, C. E., and Bartlett, Beecher, H. K. (1956). Relationship of significance of M. K. (1964). Reduction of postoperative pain by wound to pain experienced. J.A.M.A., 161, 1609. encouragement and instruction of patients. N. Engl. J. (1959). Measurement of Subjective Responses. New Med., 270, 825. York: Oxford University Press. Ferrari, H. A., Fuson, R. L., and Dent, S. J. (1969). The relationship of the anesthetic agent to post(1962). Pain placebos and physicians. Practitioner, operative analgesic requirements. South. Med. J., 62, 189, 141. 1201. (1969). Anxiety and pain. J.A.M.A., 209, 1080. Bishop, G. H. (1959). In Measurement of Subjective Finer, B. (1970). Studies of the variability in expiratory efforts before and after cholecystectomy. Acta AnaesResponses, Beecher, H. K., p. 6. New York: Oxford thesiol. Scand. [Suppl.], 38, 7. University Press. (1972). The use of hypnosis in the clinical manageBridenbaugh, P. O.. Dupen, S. L., Moore, D. C , ment of pain; in Pain (eds. Payne, J. P.. and Burt, Bridenbaugh, C. D., and Thompson, G. E. (1973). R. A. P.), p. 168. London: Churchill Livingstone. Postoperative intercostal nerve block analgesia versus Forrest, W. H. (1968). Treatment of postoperative pain. narcotic analgesia. Anesth. Analg. (Cleve.), 52, 82. Mod. Treat., 5/6, 1154. Bromage, P. R. (1955). Spirometry in assessment of analgesia after abdominal surgery; a method of com- Gildea, J. (1968). The relief of postoperative pain. Med. paring analgesic drugs. Br. Med. J., 2, 589. Clin. N. Am., 52, 81. and by the increased concurrent use of non-toxic tranquillizing drugs. The wider use of nitrous oxide is also recommended, especially in the first 24 hr following abdominal surgery. The problem of patients to whom narcotic pain relief may be contraindicated, such as those with chronic respiratory insufficiency scheduled for abdominal surgery, may be managed by the more complex techniques of regional blockade. Each patient must be viewed individually not only to gain meaningful contact but also to design personal analgesic therapy. This will require that more time will be spent with postoperative patients by suitably trained personnel. The development of recovery areas will improve the situation as will the suggestion by Masson (1971) of a "pain nurse" or doctor, whose main functions would be to visit patients after their operation to assess their pain before it is intolerable, and to arrange necessary treatment. There remains a certain acceptance that postoperative pain is inevitable; the occurrence of pain may be inevitable, but the suffering and morbidity caused by it need never be so.
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Parbrook, G. D. (1972). Entonox for postoperative analgesia. Proc. R. Soc. Med., 65, 8. Rees, G. A. D., and Robertson, G. S. (1964). Relief of postoperative pain: comparison of 25% nitrous oxide and oxygen mixture with morphine. Br. Med. J., 2, 480.
Steel, D. F., and Dalrymple, D. G. (1973). Factors predisposing to postoperative pain and pulmonary complications. Br. J. Anaesth., 45, 21. Parkhouse, J., and Holmes, C. M. (1963). Assessing postoperative pain relief. Proc. R. Soc. Med., 56, 579. Lambrechts, W., and Simpson, B. R. J. (1961). The incidence of postoperative pain. Br. J. Anaesth., 33, 345. Petrovsky, B. V., and Yefuni, S. N. (1965). Therapeutic inhalational anaesthesia. Br. J. Anaesth., 37, 42. Pooler, H. E. (1949). Relief of postoperative pain and its influence on vital capacity. Br. Med. J., 11, 1200. Quimby, C. W. (1968). Preoperative prophylaxis of postoperative pain. Med. Clin. N. Am., 52, 73. Rifat, K. (1972). Pentazocine in sequential analgesic anaesthesia. Br. J. Anaesth., 44, 175. Roe, B. B. (1963). Are postoperative narcotics necessary? Arch. Surg., 87, 912. Rosen, M., Latto, P., and Asscher, A. W. (1972). Kidney function after methoxyflurane analgesia during labour. Br. Med. J., 1, 81. Sechzer, P. H. (1971). Studies in pain with analgesic— demand system. Anesth. Analg. (Cleve.), 50, 1. Sheffer, M. B., and Greifenstein, F. E. (1960). Emotional responses of patients to surgery and anesthesia. Anesthesiology, 21, 502. Simpson, B. R. J., Parkhouse, J., Marshall, R., and Lambrechts, W. (1961). Extradural analgesia and the prevention of postoperative pulmonary complications. Br. J. Anaesth., 33, 628. Spence, A. A., and Alexander, J. I. (1971). Mechanisms of postoperative hypoxaemia. Proc. R. Soc. Med., 65, 12. Smith, G. (1971). Postoperative analgesia and lung function: a comparison of morphine and extradural block. Br. J. Anaesth., 43, 144. Harris, R. (1970). The influence of postoperative analgesia and operative procedure on postoperative lung function: a comparison of morphine with extradural block. Anaesthesia, 25, 126. Spoerel, W. E., and Leung, C. Y. (1974). Acupuncture in a pain clinic. Can. Anaesth. Soc. J., 21, 221. Swafford, L. I., and Allan, D. (1968). Pain relief in the paediatric patient. Med. Clin. N. Am., 52, 131. Swerdlow, M. (1967). General analgesics used in pain relief: pharmacology. Br. J. Anaesth., 39, 699. Murray, A., and Daw, R. H. (1963). A study of postoperative pain. Acta Anaesthesiol. Scand., 7, 1. Ulert, I. A. (1967). Narcotics in the postoperative period: a reappraisal. South. Med. J., 60, 1289. Ward-McQuaid, J. N., Chowdhury, M. I., and Zaman, S. A. (1973). Postoperative pain and anxiety: a comparison of pentazocine alone and pentazocine combined with oxypertine. Br. J. Anaesth., 45, 1075. Yakaitis, R. W., Cooke, J. E., and Redding, J. S. (1972). Self-administered methoxyflurane on postoperative pain: effectiveness and patient acceptance. Anesth. Analg. (Cleve.). 51, 208. Yusuke, I. (1974). Postoperative pain relief with ketamine infusion. Anaesthesia, 29, 222.
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Gupta, P. K., and Dundee, J. W. (1974). Morphine combined with doxapram or naloxone: a study of postoperative pain relief. Anaesthesia, 29, 33. Hollmen, A., and Saukkonen, J. (1972). The effects of postoperative epidural analgesia versus centrally acting opiate on physiological shunt after upper abdominal operation. Ada Anaesthesiol. Scand., 16, 147. HoveU, B. C , Masson, A. H. B., and Wilson, J. (1967). Trichlorethylene for postoperative analgesia. Anaesthesia, 22, 284. Kay, B. (1973). A study of strong oral analgesics: the relief of postoperative pain using dextromoramide, pentazocine and bezitramide. Br. J. Anaesth., 45, 623. Keats, A. S. (1956). Postoperative pain: research and treatment. J. Chronic Dis., 4, 72. Keeri-Szanto, M., and Heaman, S. (1972). Postoperative demand analgesia. Surg. Gynecol. Obstet., 134, 647. Knape, H. (1971). Further experiences with bezitramide. Br. J. Anaesth., 43, 76. Knudson, J. (1970). Duration of hypoxaemia after uncomplicated upper abdominal and thoraco-abdominal operations. Anaesthesia, 25, 372. Lasagna, L., and Beecher, H. K. (1954). The optimum dose of morphine. J.A.M.A., 156, 230. Lauer, J. W. (1968). Hypnosis in the relief of pain. Med. Clin. N. Am., 52, 217. Loan, W. B., and Dundee. J. W. (1967). The clinical assessment of pain. Practitioner, 198, 759. Morrison, J. D. (1967). The incidence and severity of postoperative pain. Br. J. Anaesth., 39, 695. Marks, M. M. (1967). Talwin (pentazocine), a new nonnarcotic analgesic in rectal surgery: a three year evaluation. Int. Surg., 48, 519. Martin. S. J., Murphy, J. D., Colliton, R. J., and Zeffiro, R. G. (1967). Clinical studies with Innovar. Anesthesiology, 28, 458. Masson, A. H. B. (1962). Clinical assessment of analgesic drugs: spirometry trials. Anesth. Analg. (Cleve.), 41, 615. (1967). The role of analgesic drugs in the treatment of postoperative pain. Br. J. Anaesth., 39, 713. (1971). Postoperative analgesia; in Pharmacological topics in anesthesia (ed. Millar, R. A.). Int. Anesthesiol. Clin., 9, 235. Boston: Little, Brown and Co. Merskey, H , and Hester, R. A. (1972). The treatment of chronic pain with psychotropic drugs. Postgrad. Med. J., 48, 594. Minuck, M. (1972). Postoperative analgesia—comparison of methotrimeprazine and meperidine as postoperative analgesic agents. Can. Anaesth. Soc. J., 19, 87. Moore, D. C , and Bridenbaugh, C. D. (1962). Intercostal nerve blocks in 4333 patients: indications, techniques and complications. Anesth. Analg. (Cleve.), 41, 1. Morrison, J. D., Loan, W. B., and Dundee, J. W. (1971). Controlled comparison of the efficacy of 14 preparations in the relief of postoperative pain. Br. Med. J., 3, 287. Muneyuki, M., Ueda. Y., Urabe, N., Takeshita, H., and Inamoto, A. (1968). Postoperative pain relief and respiratory function in man. Anesthesiology, 29, 304. Palmer, K. N. V. (1967). Postoperative pulmonary complications. Br. J. Surg., 54, 479. Papper, E. M., Brodie, B. B., and Rovenstine, E. A. (1952). Postoperative pain: its use in the comparative evaluation of analgesics. Surgery, 32, 107. Parbrook, G. D. (1967). Techniques of inhalational analgesia in the postoperative period. Br. J. Anaesth., 39, 730.
BRITISH JOURNAL OF ANAESTHESIA
THE MANAGEMENT OF POSTOPERATIVE PAIN P. G. M. WALLACE AND W. NORMS
Incidence and severity of postoperative pain. Pain after operation is largely a result of direct trauma caused to tissues by surgery, but may be further aggravated by associated reflex muscular spasm or visceral distension. It is of two characteristic types: a dull steady pain at rest, and a more severe stabbing pain associated with movement. The latter is more distressing to the patient and is also much more difficult to relieve adequately. Postoperative pain is a self-limiting phenomenon, most severe during the first day following surgery, diminishing over the next 24 hr, and minimal after P.
G.
M.
WALLACE, M.B.,
CH.B.,
D. OBST., R.C.O.G.,
F.F.A.R.C.S.; W. NORRIS, M.D., F.F.A.R.c.s.; Division of Anaesthesia, Royal Infirmary, Glasgow G4 OSF.
3 or 4 days. It is most marked after operations in the upper abdomen and thorax with decreasing severity in lower abdominal operations, herniorrhaphy and surgery on head, neck and limbs (Parkhouse, Lambrechts and Simpson, 1961; Loan and Morrison, 1967). It does not invariably follow surgery, however, and even after thoracic or abdominal operations about 20% of patients may not complain of significant pain (Papper, Brodie and Rovenstine, 1952). Many other factors affect the incidence and severity of postoperative pain. In the elderly or the very young, analgesic requirements appear to be reduced (Forrest, 1968; Swafford and Allan, 1968), but there is litde difference between the sexes. Personality variations do contribute greatly however. Stable patients with low neuroticism may be expected to suffer less from postoperative pain than highly neurotic patients (Parbrook, Steel and Dalrymple, 1973; Dalrymple, Parbrook and Steel, 1973). Many patients will defend themselves against the normal psychological stress of surgery by denial, failing realistically to face the situation and its implications. Patients with this personality pattern can be expected to suffer more and have poorer response to therapy in the period after operation than those who admit to anxiety (Quimby, 1968). Beecher (1959) has described two components of pain: the initial stimulus, and the psychological processing of this sensation—the reaction component. Although the stimulus may be constant in regard to the number of pain endings injured, the degree of pain experienced varies with the individual and occasion. The suffering experienced is dependent on the reaction component, which differs between individuals due to characteristics such as personality and previous conditioning, and more significantly in each individual with changing emotion, mood and situation (Beecher, 1956). The fact that placebos may relieve severe pain in 35% of patients, and that this action will vary with the presence of anxiety (Beecher, 1962, 1969), further emphasizes that emotion may alter the severity of pain experienced.
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"For all the happiness mankind can gain, is not in pleasure, but in rest from pain." John Dryden (1631-1701). The past century has seen revolutionary changes in anaesthesia during the intraoperative period. However, most patients who benefit from contemporary anaesthetic practice face postoperative pain relief by methods which have changed little since the 19th century. The most common treatment for postoperative pain remains a standard intramuscular dose of an opiate, administered at the discretion of a nurse, on demand by a patient whose pain tolerance has been exceeded. This therapeutic programme has not remained in practice because of its overwhelming success. Recent work suggests that some 40% of patients complain of inadequate pain relief following all but minor surgery (Morrison, Loan and Dundee, 1971; Keeri-Szanto and Heaman, 1972). Over 50% of a group of patients who had undergone upper abdominal surgery and "on demand" narcotic analgesia classified their pain as "very unpleasant indeed; I would be very upset if I had to go through this again" (Cronin, Redfern and Utting, 1973). This is a chillingly euphemistic indictment of the neglect which patients suffer in the period after an operation.
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The importance of pain relief. Although postoperative pain demands relief on humanitarian grounds alone, in many cases treatment also reduces significantly physical morbidity following operation. Patients with upper abdominal wounds have the most severe postoperative pain and it has long been recognized that they suffer from an increased incidence of pulmonary complications after surgery (Pooler, 1949; Palmer, 1967; Collins, Darke and Knowelden, 1968). They are frightened to move, to take deep breaths, or to cough and expectorate secretions, for fear of aggravating their pain. Respiration is shallow and grunting, and reflex abdominal muscle spasm holds the chest in an expiratory pattern with a small tidal ventilation at low lung volume. Vital capacity may be reduced by 70% (Churchill and McNeill, 1927; Bromage, 1955) and functional residual capacity, peak expiratory flow rate and timed forced expiratory volume are also reduced. Even without hypoventilation or obvious radiological abnormalities in the lungs, hypoxaemia may follow surgery. Diament and Palmer (1966) showed that this hypoxaemia was worst after upper abdominal surgery, less after
lower abdominal surgery, and not significant after non-abdominal surgery. Although greatest in the early postoperative period, it is still present 5 days following upper abdominal surgery (Knudson, 1970; Alexander et al., 1973). The presence of pain plays a considerable part in the aetiology of this hypoxaemia (Spence and Alexander, 1971). Relief of pain may cause improvement of such pulmonary dysfunction. By abolishing pain following upper abdominal surgery, with extradural blockade, Simpson et al. (1961) and Bromage (1967) obtained significant improvements in vital capacity. An increase in arterial oxygen tension during the period of postoperative hypoxaemia may also result from pain relief with extradural spinal blockade (Muneyuki et al., 1968; Spence and Smith, 1971). Postoperative lung complications will not only be reduced by improvement in ventilatory function, but the mobility encouraged in patients by pain relief will also reduce the incidence of venous thrombosis and subsequent pulmonary emboli. In addition, adequate pain relief will not discourage the patient from further surgery in future, and will minimize possible misconceptions held by the public concerning routine surgical procedures. MANAGEMENT
The management of postoperative pain is not restricted to treatment only after operation. A considerable amount can be done to minimize the pain following surgery by sensible management of the patient preoperatively and during anaesthesia itself. Prophylaxis. Psychological. The patient who is calm and who has gained an understanding of and confidence in his medical treatment through personal contact and relationship with his medical supervisors, may face the postoperative period with optimism and equanimity. Enthusiastic personal preparation before operation is of the greatest importance, and has been shown to have a marked beneficial effect on postoperative progress. Egbert et al. (1964) explained to their patients the implications of their surgery and anaesthesia. They were informed of the pain to expect, that its presence was normal, and that they would receive treatment if required. Deep breathing and coughing techniques were taught and in the period following surgery their doctors visited,
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The recognition and assessment o} pain. Pain is such a subjective experience that it is extremely difficult to convey or assess its severity. In clinical practice Bishop's (1959) definition that "pain is what the subject says hurts" allows recognition and treatment after operation in the large majority of patients. Attempts to quantify the experience, however, are much more difficult. In clinical pain, two basic approaches are possible: the introspective method, in which the patient or a trained observer may attempt to assess pain; or the behaviourist method, in which some physical parameter which is altered in the presence of pain is objectively measured, the changes being correlated with the severity of pain (Loan and Dundee, 1967). Thus, changes in pulmonary function tests following upper abdominal surgery have been studied extensively, as a fall in vital capacity (VC) associated with pain, and an improvement with analgesia (Bromage, 1955; Masson, 1962; Parkhouse and Holmes, 1963). In the mechanically ventilated postoperative patient who is unable to communicate or make skeletal movements, autonomic responses—most commonly cardiovascular changes or sweating—may be used to recognize the presence of pain (Campbell, 1967).
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U5
THE MANAGEMENT OF POSTOPERATIVE PAIN
The relief of flatulence, urinary retention, nausea and vomiting, and the immobilization of fractures, will help to raise the patient's threshold to his primary wound pain as well as remove a specific cause of complaint. Lack of sleep, or fear of the unfamiliar hospital environment, may also lower tolerance to pain. Minor discomforts such as i.v. infusions, intragastric tubes, or frequent record-taking may become greatly resented and concentrate the patient's mind on his pain and suffering. Careful attention to minimize these apparently small points can be rewarding. TREATMENT OF PAIN
Relief from pain may be obtained by various therapeutic methods: (1) Parenteral and oral agents: (a) Analgesics (b) Other drugs (2) Inhalational agents (3) Regional nerve blockade (4)
Other techniques
(1) Parenteral and oral agents. (a) Analgesics. Morphine remains the most common analgesic in use to combat severe pain; no modern substitute has been universally accepted as having overall advantages. Morphine raises the threshold of pain perception, and also alters the mental response to pain. Lasagna and Beecher (1954) consider the optimum i.m. dose to be morphine 10 rag/10 kg body weight, beyond which there is no commensurate increase in analgesia, although side effects are markedly increased. At this dose, morphine can be expected to relieve about 75% of steady wound pain, but less than 50% of the sharp pain of movement (Keats, 1956). The pharmacology of morphine and other potent analgesics has been reviewed elsewhere (Swerdlow, 1967). The individual anaesthetist must examine the evidence on the available drugs (Banister, 1974; Morrison, Loan and Dundee, 1971; Masson, 1967) and decide for himself which analgesic suits his patients' requirements. The most notable side effects of these drugs are respiratory depression, suppression of coughing, nausea and vomiting, and addiction. In the treatment of postoperative pain of about 48 hr duration addiction should not prove troublesome, unless the
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assisted and encouraged the patients and participated in their therapeutic programme. These patients required significantly less narcotic drugs and were discharged home 2 or 3 days earlier than a control group. Roe (1963) and Ulert (1967), similarly using a preoperative period of instruction, encouragement and reassurance continued into the postoperative period, also reduced significantly the amount of narcotics used. In the period following cholecystectomy, Finer (1970) produced significant improvement in the pulmonary function tests of a group of patients by encouraging them during the performance of these manoeuvres. This approach requires understanding, patience, time and effort from the anaesthetist. That anaesthetists do not concentrate sufficiently on establishing this contact has been indicated by Sheffer and Greifenstein (1960), 38% of whose patients could not even remember their anaesthetist, while 26% felt that he had not had an adequate discussion with them. More time spent on this approach will not only be personally satisfying to the anaesthetist, but will bring considerable benefit to the patient. Pharmacological. It has been shown that with prolongation of the period between termination of anaesthesia and the first requirement of postoperative pain relief, the effect of a dose of analgesic is more marked and the total quantity of analgesic in the recovery period is reduced (Swerdlow, Murray and Daw, 1963). It is advantageous, therefore, to design a technique of anaesthesia which will provide residual analgesia in the postoperative period. Preoperative medication with narcotics has little effect on postoperative requirements, but intravenous analgesics during operation will significantly delay the time until analgesia is first required after surgery, and significantly reduce the total quantity of analgesic employed (Dundee et al., 1969; Ferrari, Fuson and Dent, 1969). Similarly, the use of neuroleptanalgesia will provide a prolonged period of postoperative analgesia (Martin et al., 1967). The extension of this technique to "sequential analgesic anaesthesia" (Rifat, 1972), in which the respiratory depression associated with fentanyl analgesia is reversed by pentazocine at the end of operation, may provide pain relief for many hours after surgery. Supportive therapy. In the management of postoperative pain, the main concern is with wound pain and its direct associations. However, the patient may have other indirect causes of suffering for which specific treatment is required.
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patient is undergoing frequent and repeated surgery the period following surgery (Kay, 1973; Knape, when pentazocine is indicated because of low risk 1971). of abuse. The effects on pulmonary function are of The milder analgesics — dihydrocodeine, cogreatest importance, however. In postoperative pain deine, aspirin and paracetamol — should be used relief, it is hoped to strike a compromise above the more widely following minor surgery and for the dose level which provides adequate analgesia but residual discomfort and mild pain in the third or below that at which unacceptable side effects occur. subsequent days after major surgery. The routine postoperative prescription of parenBrief mention should be made of the use of conteral analgesic drugs seldom satisfies this criterion. tinuous i.v. infusion of local analgesic agents to Indeed, a significant fall in arterial oxygen tension provide pain relief (Bartlett and Hutaserani, 1961); has been found in upper abdominal cases following and of the more effective use of ketamine in "subpain relief with narcotics (Muneyuki et al., 1968; dissociative" doses (Yusuke, 1974). Gildea (1968) Hollmen and Saukkonen, 1972). has suggested the use of dilute solutions of ethanol The sensitivity of each subject varies to a given i.v. to provide basal analgesia with psychic condose of narcotic, and the amount required should tentment and useful postoperative calories. All be carefully titrated on an individual basis to pro- methods of continuous i.v. analgesia require vide pain relief at the minimum dose. This is extremely careful supervision to prevent overdosage arranged most easily by incremental small intra- and subsequent toxic side effects. venous doses, say morphine 1-2 mg. Careful addi(b) Other drugs. All patients undergoing surgery .tion can be made to maintain the drug level suffer anxiety to a greater or lesser extent, which just above that required for pain relief, and may have a detrimental effect on the reaction apparatus has been described by which the patient component of pain. Therefore, the recognition of may inject himself automatically as required excessive anxiety requires direct treatment by (Sechzer, 1971). The i.m. route results in much anxiolytic drugs. larger variations in drug effects, but may provide The phenothiazines have been used widely, alone satisfactory analgesia if tailored by observation of and in combination with analgesics, especially in the needs of the individual patient. The inflexible the management of pain of a chronic nature regime of a set dose of analgesic every 6 hr is (Merskey and Hester, 1972). Chlorpromazine, usually inadequate; some patients will be under- promazine and trimeprazine may have analgesic dosed and some overdosed. The effect of a dose of activity (Dundee and Moore, 1961) and methoanalgesic must be carefully assessed and subsequent trimeprazine has been shown to have a potent doses revised accordingly. It is recommended that analgesic effect (Minuck, 1972). Their value to the relief of pain be managed by shortening the time agitated patient after operation is limited by the between injections, rather than by increasing associated depression of cerebral state and cardioindividual dosage. The anaesthetist must ensure vascular function. The benzodiazepines have been that an adequate supply of analgesic is available to reviewed by Dundee and Haslett (1970). They the patient in the period following an operation. appear to have no analgesic effect, but their Although the use of routine narcotic analgesia anxiolytic and amnesic action, with minimal physimay increase postoperative lung dysfunction in cal depression, is safe for use following surgery. comparison to regional blockade, it appears that Chlordiazepoxide and diazepam have each been more frequent doses of narcotic, for example mor- used as the sole therapeutic agent in the treatment phine 10 mg, 4 hourly, do not further increase this of surgical pain (Derrick, Wette and Hill, 1967; dysfunction (Collins, Darke and Knowelden, 1968; Bruce, 1968), and have provided satisfactory relief Alexander, Parikh and Spence, 1973). Thus, anal- in a large majority of patients. This emphasizes gesic drugs may safely be given more frequently the importance of emotional factors in aggravating than in traditional practice, if indicated in the pain experience, and the wider use of these agents is to be recommended to elevate patients' individual patients. Few of the potent analgesics are active reliably pain tolerance and reduce the quantity of potenby mouth, the most useful exceptions being penta- tially toxic narcotic required (Marks, 1967). The zocine, dextromoramide and bezitramide. In suit- use of the newer tranquillizer oxypertine, in comable dosage these drugs offer effective relief of bination with pentazocine (Ward-McQuaid, Chowsevere pain, and have had considerable success in dhury and Zaman, 1973), has been shown similarly
THE MANAGEMENT OF POSTOPERATIVE PAIN
(2) Inhalational analgesic agents. Nitrous oxide. Entonox, the premixed 50% mixture of nitrous oxide and oxygen, is readily available for pain relief in the general hospital environment (Baskett and Bennett, 1971), either from cylinders or from pipeline in more recently built units. Fifty per cent nitrous oxide in oxygen for extended periods is associated with somnolence, and the use of this and higher concentrations in the period after operation (Petrovsky and Yefuni, 1965) is in effect an extension of die anaesthetic state and results in immobility and failure of cooperation. However, lower concentrations of nitrous oxide (20-25%), may provide postoperative analgesia equivalent to routine use of narcotics (Parbrook, Rees and Robertson, 1964), with little sedation. This basal analgesia may be supplemented safely by the use of additional parenteral narcotics. Parbrook (1967, 1972) has described how entonox given directly through an "MC" or "Edinburgh" type oxygen mask will be air-diluted to provide 10-25% nitrous oxide in 25-35% oxygen, depending on gas flow. In upper abdominal cases, or in patients who would be receiving routine oxygen therapy after operation, the substitution of entonox will provide oxygen supplementation and significant analgesia without marked cerebral depression. Marrow depression may occur with prolonged use of nitrous oxide, and its use after surgery must be restricted to 36 or 48 hr. Unpleasant dreams or nausea may also complicate its administration in a minority of cases. Pure entonox may be used on an intermittent basis to cover movement, wound-dressing or physiotherapy. Nitrous oxide has the added advantage of being rapidly effective and excreted. Trichloroethylene and methoxyflurane. These volatile agents have had considerable use in subanaesthetic concentrations for the relief of pain in
labour, the usual levels employed being 0.35% methoxyflurane and 0.50% trichloroethylene. In the postoperative period, attention has been focused on their use as supplementary analgesia during "stir-up" procedures such as wound dressings or physiotherapy. Self administered through drawover vaporizers, they may provide analgesia equivalent to that obtained by the usual doses of narcotics, without significant respiratory depression (Hovell, Masson and Wilson, 1967; Yakaitis, Cooke and Redding, 1972). Their odour is resented by many patients and their prolonged use may cause clouding of conscious level with subsequent "hang over". Methoxyflurane has recently been implicated as a cause of renal dysfunction (Desmond, 1974) but short intermittent low dosage is considered safe (Rosen, Latto and Asscher, 1972). The volatile agents are therefore largely restricted to short intermittent use after surgery to provide extra analgesia, but nitrous oxide deserves considerably more application in the management of postoperative pain. When pain is at its worst and most deleterious to the patient, in the first 36 hr following upper abdominal or thoracic surgery, nitrous oxide with supplementary oxygen may provide convenient, cheap, safe and easily reversed analgesia with little change to basic postoperative practices. (3) Sensory nerve blockade. While the systemic analgesics offer imperfect pain relief, the use of local analgesic agents to block transmission of afferent impulses in sensory nerves may completely abolish pain. (a) Extradural blockade. In the general surgical patient, extradural analgesia has developed slowly despite enthusiastic reviews (Bromage, 1967; Simpson et al., 1961). Following upper abdominal surgery, as has been noted, the patient has most to gain from complete pain relief—he can become mobile, take deep breaths and cough. Extradural blockade offers considerable improvement in respiratory function in these cases (Spence, Smith and Harris, 1970). Complications are rare but may be serious. Dawkins (1969) has made a classic review of over 350 papers; the most notable side effects were accidental dural puncture (2.5%), total spinal analgesia (0.2%), intravascular injection (2.8%), and substantial hypotension (1.8%). Relief of pain following upper abdominal incisions requires analgesia to the nipple line
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to reduce patients' anxiety and their subsequent analgesic requirement. It was hoped that premixed combinations of narcotic and antagonist would provide analgesia without respiratory depression. The analgesic effect itself is also antagonized, however (Campbell, Masson and Norris, 1965), and these mixtures are of little value. The combination of morphine with the respiratory stimulant doxapram (Gupta and Dundee, 1974) promises a reduction in respiratory depression and subsequent pulmonary complications with unaffected analgesia.
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(4) Other techniques. Hypnosis. Finer (1972) has defined hypnosis,
which has long been used in the relief of pain, as "a state of selective concentration and detachment which can be learned under deep muscular and mental relaxation". The hypnotic trance may be divided into three stages (Lauer, 1968). Varying degrees of analgesia may be present in the medium trance, and complete analgesia and amnesia can be provided by deep trance. Probably only about 15-20% of the population can reach the third stage even with skilled practitioners. It is of interest to note that suggestion determines the area of analgesia, and not normal anatomical or physiological considerations. Unlike the other methods of pain control there are no physical toxic side effects but psychiatric disturbances may occur. However, its unreliability compared to chemical analgesia, and a paucity of trained practitioners, make hypnosis a rarely used technique in the management of postoperative pain. Acupuncture. This Chinese medical art is not understood despite considerable present-day interest (Dimond, 1971; Cheng and Ding, 1973). It has been suggested that hypnosis plays a major part, or that the explanation lies in diminution of pain transmission by nocireceptor stimulation of the Gate Control Mechanism. Enthusiasts claim a much higher reliability in the provision of analgesia than by hypnosis alone (Spoerel and Leung, 1974). Its use and investigation is again limited by a lack of suitably trained medical practitioners. Although the above techniques may have limited application for most patients, the care and time that is taken with them in selection, in explanation, and in the provision of a meaningful doctor-patient relationship may be most usefully applied to all management of pain in the period following surgery. CONCLUSION
The increasing involvement of anaesthetists in the recovery area and in the intensive care unit has made them more aware of the inadequacies of present-day attitudes to pain control. With the techniques available at the moment, although they may be far from perfect, it should be possible to reach a much higher standard of management of postoperative pain. The narcotic analgesics will remain the mainstay of treatment for the majority of patients. The amount of these drugs required may be greatly reduced, however, by compassionate psychological support of patients before and after operation,
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(thoracic 4-5) and if benefits are to include mobility, the danger of postural hypotension from concomitant sympathetic blockade must be minimized. Therefore, smaller volumes of analgesic by the thoracic approach are more efficient, by intermittent injection or continuous infusion (Dawkins and Steel, 1971). Lignocaine has been superseded by the longer acting bupivacaine as the agent of choice, although Bromage (1972) suggests that carbonated local analgesics may reduce the incidence of unblocked segments. This technique will provide complete analgesia from the chest down but requires special training and skill, scrupulous asepsis, and vigilant observation during the period of analgesia. Although impracticable for all cases, it is the technique of choice in the period after operation for selected abdominal cases with severe respiratory embarrassment. (b) Intercostal nerve blockade. Sensory transmission from the body wall, from the sternal notch to just above the pubis, may be interrupted by local analgesic blockade of the intercostal nerves serving appropriate dermatomes. Analgesia for any incision in this area may be provided by a block which includes an extra nerve below and above the relevant dermatomes. The techniques of injecting analgesic below each rib have been described by Moore and Bridenbaugh (1962), and Ablondi et al. (1966). There is a danger of pneumothorax but in comparison with extradural blockade there should be little fall in arterial pressure as the block is lateral to the sympathetic outflow. This is particularly advantageous where pain relief is required above the level of thoracic 5 where the cardiac sympathetic nerves lie. Intercostal block has been compared favourably to the opiates in the management of thoracic and upper abdominal cases (Bridenbaugh et al., 1973). The visceral afferent nerves are not affected by the above technique, and patients may continue to complain of deep pain. These visceral sensory inflows may be included with the intercostal nerves by paravertebral block, which involves injection of local analgesic close to the exit of the nerve trunks from the intervertebral foramina. Infiltration of the surgical wound with local analgesic solutions has been largely abandoned due to increased sepsis and delayed healing.
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