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Introduction

In the literature review (Chaps.2 and 3) post-operative pain was identified as a separate stress to the general stress o f surgery. Several studies had noted that patients separated pain from other variables (Johnstone, 1982; Salmon et. al., 1990), although surgical stress and pain are associated and probably interact. In chapter four the pilot study interviews confirmed the separation of pain and surgery from the patients perception. We have contended that post-operative pain may be legitimately regarded as a separate stress.

Post surgical pain, its duration and its control, is probably the most important factor for the surgical patient. In the pilot study reported above (Chap.4) most patients’ first concern was with pain. While medical techniques and drug therapies for the control o f postoperative pain have improved markedly in the past decade it is clear that pain control is still inadequate. Tigerstedt (1990) reports that in the previous decade seventy five percent o f post-operative patients were reporting moderate to marked pain distress.

Control of post-operative pain has increasingly included psychological factors, most often in combination with drug regimes, with varying degrees of success. Modem clinical practice usually involves the patient in the control of their post-operative pain. Techniques include supplying accurate sensory information (Johnson, 1973. Johnson and Leventhal, 1974) teaching cognitive and behavioural strategies (Tan, 1982 for review) and 'Patient Controlled Analgesia' which incorporates 'self efficacy' with drug administration are. A common factor in all post-operative pain control is that they are discussed or taught pre-operatively and therefore prime the patient to anticipate the post-operative pain.

Anticipation

the individuals perception of the threat (Folkman and Lazarus, 1985. Feifel, Strack and Nagy, 1987) and their response to it (Mathews and Ridgeway, 1981). One o f the factors influencing subjective interpretation o f and responses to stress may be their prior experience o f similar situations and/or their beliefs about the event (Leventhal and Everhart, 1979). Subjects admitted to hospital for elective surgery will have some preconceptions about the event. If not from prior experience then from media coverage, anecdotal evidence from other patients and any preparatory literature supplied by the ward. Given their concern with post-operative pain subjects will undoubtedly have preconceptions about it.

The anticipation of post-operative pain may be important in several ways. Where subject expectation in isolation, has been examined no direct effect on post-operative pain has been found (Wallace, 1985 and Kent, 1986). However changes in pre and post-operative anxiety (Mathews and Ridgeway, 1981. de Groot, Boeke, van der Berge, Duivenvoorde, Bonke and Passcheir, 1997) have been noted in response to pre-operative 'thinking about' surgery and post-operative pain. Heightened pre-surgical state anxiety has been associated with higher levels of postoperative anxiety and pain, (Mathews and Ridgeway, 1981. de Groot, Boeke, van der Berge, Duivenvoorde, Bonke and Passcheir, 1997). In a review article Mathews and Ridgeway (1981) conclude that higher levels of pre-operative affective states are associated with higher levels of post-operative affective state and pain, de Groot and associates (1997) demonstrated that preoperative anxiety predicted o f postoperative anxiety and greater reporting o f post-operative pain in spinal surgery patients. This association was linear and independent of other variables measured. The mechanism of this association is not clear, heightened pre-operative anxiety may result in raised post-operative anxiety levels and thus directly affect pain. However preoperative state anxiety is not necessarily predictive o f early post-operative state anxiety, 'Coping responses to surgical stress' (chap. 5. above). The dissociation between pre and post-operative affective state has been noted before (Salmon et. al ,1988). He and his colleagues also report that pre-operative anxiety is not linearly related to levels of post-operative pain. This apparent paradox may be explained by ‘stress induced analgesia’(Grevert and Goldstein, 1977). In animal studies extreme stress has been associated with loss o f normal responses to pain. Bolles and Fanselow (1980) have

extrapolated the theory of stress induced analgesia to humans. In a review they found no evidence to link fear with increased reporting of pain rather subjects who described

themselves as fearful tended to report less pain. In their ‘perceptual defence model’ o f fear and pain Bolles and Fanslow (1980) suggest that fear induces the 'fight or flight' response and may therefore mask or reduce pain. However the effect of fear of pain itself is not clear. Anticipation ‘thinking about surgery’ may increase or reduce pre-operative anxiety. The studies reported above clearly indicate that pre-operative anxiety/fear is not predictive of post-operative state. The relationship between anticipation of the event and the outcome is far from clear. The implications of the studies above are that high levels o f pre-operative affect may result in a measure o f ‘stress induced analgesia’ and subsequent lower levels of post-operative pain and distress. However other variables must also be considered.

Anticipation of post-operative pain may result in excessive worrying thus heightening the pre-operative affective state and result in increased utilization o f negative coping strategies (see Chapter, 5 above).

A more direct influence of anticipation on pain may be postulated within the theoretical framework o f cognitive processing. Leventhal's 'Processing Model' of personal episodic memory (Leventhal and Everhart, 1979) demonstrates how pain is enhanced and elaborated by emotional state, information, behaviours and memory systems. Where the pain stimulus is of sudden onset the elaboration of the stimulus will occur at encoding i.e. pain onset. However in pre-operative pain the majority o f patients will have considerable time to anticipate the pain. Anticipation of pain by stimulating memory schemata relating to pain intensity and distress may prime the system. Even where the pre-operative preparation to operation time is short, as in 'day surgery’ and comprehensive, well managed and meets each individuals needs there will be some time for elaboration o f the stimulus. Most patients will have had waiting time pre-hospitalisation and subscribe to the prevailing wisdom, operation equals pain, therefore they will be anticipating pain long before any preparation for surgery commences and may thus reduce their effectiveness.

Recall

If preconceptions are related to prior experience it would also be important to assess the accuracy o f recall of the current event. Post-operative pain is easily measured (Chap. 3) and was the variable of choice to assess the effects of anticipation and the accuracy of recall in the surgical patient.

Clearly the memory of pain is important within the processing model since it modifies the experience. It is equally important in facilitating assessment o f any change in clinical pain state which indicate physiological change. Patients use recall to compare current pain with prior pain, a diminution of pain probably indicates healing, while increased pain suggests a worsening of the original condition and or further complications e.g. secondary infection. In either case change of pain state will influence treatment. Pain memory schemata may also be important in non-physiological pain state, e.g. phantom limb pain (Hill et. al., 1996) although it is not clear that recall is accurate. Nikolajsen (1997) and associates

demonstrated a considerable difference in the patients recollection o f pre-amputation pain after amputation. Although their patients believed they felt the same pain in the phantom limb. Clearly accuracy of recall is important, however it has not often been investigated (Erskine et. al., 1990). The effects of other variables, affective and mood states, on accuracy of pain recall is still unclear.

There is some evidence that anticipation of pain influences memory, but the mechanism is not clear. Significant correlations between anticipated (expected) and recalled pain have been reported for dental patients (Kent, 1985) and chronic pain (Linton and Melin, 1982). In both studies over estimation of the pain resulted in overestimation at recall. In the case o f the acute pain anxiety was shown to influence the anticipation and recall, highly anxious subjects tending to overestimate. Interestingly, Bernstein et. al. (1979) cite memory o f past painful experience as a cause o f enhanced dental anxiety. The relationship between

The following study aims to elucidate further the effects of anticipation of pain on post­ operative pain, the recall o f pain and the interactive effect with anxiety.

This study includes the variables not reported in Chapter Five. The sample is that of Chapter Five.