Physiological and subjective stress responses in surgical patients

Physiological and subjective stress responses in surgical patients

Journal qf Psychoromarrc Primed in Great Bntain. Research, Vol. 30, No. 2, pp. 205-215, PHYSIOLOGICAL $3.00+0.00 0022.3999/86 r’ 1986 Pergamon Pres...

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Journal qf Psychoromarrc Primed in Great Bntain.

Research, Vol. 30, No. 2, pp. 205-215,

PHYSIOLOGICAL

$3.00+0.00 0022.3999/86 r’ 1986 Pergamon Press Lrd.

1986.

AND SUBJECTIVE STRESS IN SURGICAL PATIENTS

RESPONSES

CLAUS V~CELE* and ANDREW STEPTOE? (Received

19 June 1985; accepted

in revised form

28 July 1985)

Abstract-Autonomic responses, mood and psychological coping were assessed in two groups of orthopaedic patients during hospitalisation for major or minor surgery. Eight patients admitted for total hip replacement and seven patients undergoing knee arthroscopy were seen daily for two days before surgery until discharged from hospital. Mood and coping questionnaires were administered on each session, while pain, heart rate, blood pressure, skin conductance level, palmar sweat prints and forearm EMG were also recorded. Heart rate increased from pre- to post-operative assessments, while skin conductance and palmar sweating fell to low levels on the days immediately following surgery, returning to basal values only after several days. Self ratings of anxiety, fatigue, depression and pain were highest on the immediate post-operative days. Patients utilised the coping factors Rational Cognition and Behavioural Action to the greatest extent, but ratings on coping factors fluctuated little over the study period. The interrelations between these measures and possible explanations of the results are discussed.

INTRODUCTION

MANY PATIENTSundergoing surgery experience high levels of stress and anxiety both before and after their operations [l]. Surgery provides a useful model for stress in the real world, in that it combines the intense involvement usually found only in field studies with the stringent controls over movement and activity that are normally available only in the laboratory. A better understanding of stress-related mechanisms may help identify high risk patients, and improve methods of psychological preparation for surgery. The relationship between psychological factors and patients’ experiences during surgery and recovery has been the subject of considerable research [2]. Unfortunately, assessments of outcome have largely been confined to self-report measures of distress or pain, or to clinical variables such as level of analgesic prescription and number of days spent in hospital prior to discharge. Only a few studies have included autonomic, endocrine or immunological parameters, even though these measures may provide important information concerning the mechanisms mediating psychological effects [3-51. The aim of this study was to address two related issues: what autonomic parameters are sensitive to the stress of surgery, and how do autonomic responses relate to psychological reactions and coping processes in this situation. The existing literature shows a paradoxical pattern of autonomic response to major surgery. One rapid and easily measured parameter is the sweat gland count, or palmar sweat index (PSI), assessed using the plastic cast technique. Harrison et al. [6] recorded palmar sweating daily in 40 mixed surgical patients for two days prior to and 14 days following operations. The PSI decreased before surgery, reaching its nadir one or two days following the operation. Recovery back to basal levels took place within three days for women, but not for 13 days in men. This

*Currently at the Department of Psychology, University of Hamburg, FRG. VZorrespondence should be addressed to: Dr Andrew Steptoe, Department of Psychology, Hospital Medical School, University of London, SW17 ORE, U.K. 205

St George’s

observation was unexpected, since sweat gland activity generally increases in anxietyprovoking situations. Close correlations between counts of active sweat glands and skin resistance have been reported by Thomas and Korr [7]. Other investigators have monitored PSI in children undergoing psychological preparation for surgery 18, 91 and in adults flying in small aircraft [9], and have interpreted the measure in the reverse direction, with lower PSI indicating stress reduction. However, Lindeman and Stetzer [lo] found that PSI was reduced to a greater extent postoperatively in controls than in patients undergoing psychological preparation, suggesting that PSI was negatively correlated with psychological distress. A negative association was also observed in an experimental stress paradigm by Martens and Landers [l 11. None of these studies involved simultaneous assessment of conventional electrodermal parameters such as skin conductance level. In the present study, it was therefore decided to assess both PSI and skin conductance level, in order to examine the pattern and interrelationship between these responses. Heart rate and blood pressure were also measured, since they are reported to be sensitive to psychological preparation for surgery [12, 131. In addition, electromyographic activity (EMG) was monitored from the forearm flexor as an indication of muscle tension. An attempt was made to determine whether physiological responses vary with severity of surgery by contrasting patients undergoing major (total hip replacement) and minor (knee arthroscopy) orthopaedic surgery. The second aim of the study concerned the relationship between emotional state, physiological response and psychological coping. Individual differences in anxiety and other emotional variables affect postoperative pain and rate of recovery [2]. Psychological coping style may also affect outcome [14]. The relationship between psychological coping and physiological response is uncertain, although some associations have been reported during minor medical procedures [5, 151. In the present investigation it was decided to assess psychological coping as a state measure repeatedly during hospital admission, in order to see whether patterns of coping change with the different problems confronting patients.

Eight patients admitted to St George’s Hospital for total hip replacement were assessed on the two davs 1) preceding the operation, and then on Days 1, 2, 3, 4, 5, 7, 9, 11 following surgery. No assess((2, ments were conducted on the day of surgery itself, although heart rate and blood pressure were later retrieved from the recovery room notes (Day 0). The sample consisted of four men and four Nomen, ranging in age from 29 to 79 (median 63). The second sample of seve,n patients admitted for knee arthroscopy were moniiored on the two days before surgery until discharge (three days post-surgery). The knee arthroscopy group consisted of four men and three women with an age range of 23 to 62 (median 55). These orthopaedic operations were chosen, since in comparison with other surgical groups, patients were relatively free from endocrine or cardiovascular disorders that might confound the physiological measures studied. Patients admitted consecutively over a nine-week period were asked to participate, and two refused.

Emotional state was assessed with the Profile of Mood States (POMS [16]), scored to derive six mood factors: tension-anxiety, depression, vigour, fatigue, anger and confusion-bewilderment. Psychological coping was assessed with trait and state measures. The trait measure was the Locus of Control questionnaire developed by Levenson [17] from which scores on three subscales were derived, reflecting beliefs in Internal control, control by Powerful Others, and Chance. The state coping measure was the Method\

Stress in surgical

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of Coping scale, an extension of the questionnaire described by Billings and Moos [18]. It consisted of 23 coping statements, preceded by the following instructions: ‘Listed below are a number of strategies people may use when trying to cope with stress. We would like to find out whether you have used these methods when approaching (or since) your operation.’ The inventory devised by Billings and Moos was grouped into different clusters of items, but no data were reported concerning the internal reliability of these derived scales. It was therefore decided to utilise the item clusters identified by Kaloupek et al. [19] through a principal components analysis of responses by 145 blood donors. Using this procedure, five coping factors were identified (some items contibuting to more than one factor): Worry (e.g. ‘I prepare for the worst’, seven items); Suppression (e.g. ‘I try to reduce tension by not thinking about the situation’, seven items); Rational Cognition (e.g. ‘I try to step back from the situation and be more objective’, four items); Behavioural Action (e.g. ‘I have tried to take some positive action to help myself’, three items); and Denial (e.g. ‘I try to go on as if nothing has happened’, eight items). It was decided that measures of pain intensity would be difficult to interpret, owing to the varying schedules of analgesic medication. A measure of pain duration was therefore taken, by asking patients how much of the time they had been in pain over the last day. This was scored on a five-point scale ranging from 1= ‘very little of the time’ to 5 = ‘most of the time’. Preoccupation with the operation was assessed by asking patients how much time they had been thinking about the operation over the last day (five-point scale from 1 = ‘not at all’ to 5 = ‘it has been on my mind most of the time’). Blood pressure was measured using a Hawksley random-zero sphygmomanometer in order to overcome the terminal digit preferences and biases inherent in manual sphygmomanometry. Pulse rate was monitored automatically from a finger photoplethysmograph with a Boso Card II. Palmar sweat prints were obtained using the plastic impression technique. A solution of formvar was applied to the tip of the third finger of the non-preferred hand, and the impression was lifted after a few seconds with adhesive tape. The impression was then mounted on a slide and viewled through a microscope for sweat gland counts. Tonic skin resistance was measured with silver-silver chloride electrodes attached to the second phalanges of the first and second fingers of the non-preferred hand, using a specially prepared 0.05 M NaCl paste as the electrolyte. Resistance was monitored on an Omega I ESR meter. Forearm flexor EMG was recorded from the same arm with surface silver-silver chlorrde electrodes, and monitored on a J& M 56 meter. Procedure Each patient was contacted immediately after hospital admission, and the nature of study, daily testing schedule, and the tests were explained in detail. Patients agreeing to participate gave written consent. All assessments were taken at the bedside at the same time of day in order to ensure uniform environmental conditions. Sessions took place in the morning, and each lasted between 20-30 min. After the transducers had been attached, a first reading of all physiological measures was taken (Sample 1). The psychological assessments were then completed, followed by a second physiological measure (Sample 2). Information concerning premeditation, the operation itself (total time in surgery, anaesthesia, blood loss and cardiovascular variables), and postoperative medications, were retrieved from the medical notes. Dalu reduction and analysis The PSI was assessed by counting the number of active sweat glands within a field of 4 mm2 surrounding the central whorl of the finger. Skin resistance readings were converted to log skin conductance level (SCL) in micromho (pmho) for analysis. Forearm EMG was recorded in microvolts @V). Scores on the five coping factors were standardised to allow for the different number of items contributing to each factor by dividing the score by the maximum possible and multiplying by ten, so that each had a daily maximum of 10 and minimum of 0. Repeated measures analysis of variance was carried out on each variable, with Day and Sample within Day as the within-subject factors. Sex and age were included as grouping factors, but did not materially affect the pattern of results, so are not considered in the Results section. The curvilinear relationship between responses and day of assessment was assessed using the curvilinear (quadratic) correlation, as described by Rosenthal and Rosnow (201.

RESULTS

Hip replacement group Fluctuations in heart rate, SCL and the PSI are summarised in Fig. 1. The main effect for Day was significant in all three analyses (F(lO, 70) = 7.05, p < 0.001 for heart rate, F(9, 63) = 7.84 and 2.30, p < 0.001 and 0.05 for SCL and PSI). Heart rate fell between the morning of admission and the day before surgery, then in-

208

CLAUS V~GELE and ANDRFW

STEPIOC

FIG. 1 .-Mean levels of heart rate, XL and PSI (sweat gland count) over the study period for the hip 0) and knee arthroscopy (0- - -0) groups. Study days are indicated on the replacement (O---horizontal axis.

creased by more than 20 bpm following the operation. Peak heart rates were observed on Day 3. Newman-Keuls analyses confirmed that heart rates monitored presurgery were lower than those recorded on all days following surgery. Heart rates recorded in the postoperative recovery room were reliably lower than those monitored on postoperative Days 1,2, 3 and 9. Both measures of sweat gland activity showed a pattern of response that contrasts with heart rate, in that levels fell from preoperative to immediate postoperative days. Skin conductance level returned to preoperative levels within four days, while the PSI increased gradually throughout the recovery period. Breakdown analyses using the Newman-Keuls test indicated that SCL on Days 1 and 2 differed reliably from Days -2 and - 1, and from the levels recorded from Day 4 onwards. A marginally significant effect for Day was observed in the analysis of systolic blood pressure (F(10, 70)= 1.87, p
Stress in surgical

209

patients

decline over the study period, from a mean of 128.1 (& 26.0) mmHg on Day -2 to 112.25 (? 11.5) mmHg on Day 11. No significant changes across days emerged in the analysis of diastolic blood pressure or forearm flexor EMG. However, the Sample within Day effect was reliable for EMG (F(1, 7) = 17.9, p < O.OOl), since tension declined between samples 1 and 2 from a mean of 4.06 (+- 0.88) /AVto 3.24 (* l.lO)pV. Pain ratings were high preoperatively (mean 3.63 + 1.7), peaked on the first day following surgery (mean 4.50 +- 0.5), and declined to a stable level from Day 3 onwards (mean 2.62 -e 1.3). This was confirmed in the main effect for Day identified in the analysis of variance (F(9, 63) = 4.21, p < 0.01). Breakdown analysis using the Newman-Keuls test showed that ratings on Day 1 were significantly different from all other values. Ratings on Day -2 were higher than all the postoperative values except those taken on Days 1 and 2. o-e

Tenslon-anxiety

c--O

Vigour

16-

14-

12-

0

6t

4L

I -2

FIG.

2.-Mean

-I

OP

I I

I I

1 I

I

I

2

4

7

9

3

5

I II

levels of tension-anxiety, vigour and fatigue from the POMS for the hip replacement group. Study days are indicated on the horizontal axis.

Analysis of the POMS yielded main effects for Day on three of the six factors: tension-anxiety, vigour and fatigue (F(9, 54) = 3.39, 2.16 and 3.43 respectively, p < 0.054.01). The pattern of response is summarised in Fig. 2. Tension-anxiety was at moderate levels preoperative but increased considerably on the first two days postoperatively. Subsequently, ratings declined progressively until the day of discharge. Diametrically opposed patterns of vigour and fatigue were observed. Fatigue showed a peak on Day 2, returning to preoperative levels by Day 9. The lowest levels of vigour were also recorded on Day 2. Although the main effect for Day was not reliable for the other POMS factors, the curvilinear correlation was significant in all three cases (r= -0.82, -0.83 and -0.81 for depression, anger and confusion respectively, df = 8, p < 0.025). Ratings were low preoperatively, rose to a peak on Day 2 (Day 4 for the confusion scale), then declined over the later days of hospitalisation. Data from the coping questionnaire are summarised in Table I. Analysis of variance revealed a main effect for Coping Factor (F(4, 28) = 3.20, p < 0.05), with the highest ratings being consistently observed for Rational Cognition, and the

CLAUS VSGELE and ANDREWSTEPTOF

210

TABLE I.-HIP REPLACEMENTGROUP:MEAN

FLAT~NGSOF THE COPING FACTORS(MAX=

10, MIN= 0)

Day -2

~1

1

2

3

4

worry

3.92

4.99

4.81

4.81

4.63

4.10

Suppression

6.60

6.42

6.60

5.88

4.99

5.53

Rational cognition

6.87

7.50

7.81

7.50

8.12

7.81

Behavioural action

5.78

5.77

7.05

5.78

6.20

Denial

5.46

6.25

6.09

5.78

6.56

5

7

9

II

Mean

4.99

4.63

4.63

4.63

4.61

4.81

4.45

5.35

5.35

5.60

7.18

7.18

7.81

8.43

1.62

7.46

6.63

6.21

7.03

7.05

6.50

5.78

6.09

6.25

6.87

6.25

6.13

lowest for the Worry factor. In addition, the main effect for Day was significant for the Suppression factor (F(9.63) = 2.97, p < 0.01). Scores on the Suppression factor were high preoperatively and immediately following surgery, declining on later assessments. The use of other coping factors remained stable throughout the study period, with no systematic change in ratings over the period of hospitalisation. Preoccupation ratings were highest on Day -2 (mean 3.50), declined over the later days of hospitalisation (mean for Days 7-l 1 = 2.67). However, the main effect for Day was not significant in analysis of variance.

Knee arthroscopy group The heart rate and SCL responses to surgery observed in the hip replacement group were confirmed in subjects undergoing knee arthroscopy (see Fig. 1). For both variables, the main effect for Day was significant (F(5, 30) = 3.06 and F(4, 24) = 2.97, p < 0.05). Heart rate rose postoperatively, although not to the levels found in the hip replacement group. This difference between groups was confirmed in analysis of data collected up to Day 3, since the Group by Day interaction was reliable (F(5, 56) =2.37, p < 0.05). On the other hand, the SCL reactions were similar in the two groups. Subjects undergoing knee arthroscopy showed a reduction in SCL postoperatively, returning to preoperative levels on Day 3. The PSI did not change reliably over Days, although reductions were observed during the perioperative period. No significant effects for Day were recorded in the analysis of blood pressure or forearm EMG. As in the hip replacement group, pain ratings rose from preoperative levels (Day - 1, mean 2.3 2 1.72) to a peak on Day I (mean 3.66 ? 1.03). This effect was not statistically significant however. Similar patterns were also seen in the POMS factors. The main effects for Day were significant for factors vigour and fatigue (F(4, 20) =4.37 and 7.03 respectively, p < 0.01; see Table II). Preoperative vigour levels were higher than those recorded by the hip replacement group, reflecting the greater degree of fitness and flexibility in subjects undergoing the less severe procedure. However, vigour fell substantially following surgery. Fatigue showed the reverse patterns with low preoperative levels succeeded by high ratings on Days l-3. None of the other POMS factors showed significant changes over Days, although increases post-surgery were recorded for tension-anxiety, depression and anger. The coping results are also summarised in Table II. The main effect for Coping Factor was significant (F(4, 20) = 8.10, p < O.Ol), with the lowest ratings again being

Stress in surgical TABLE II.-KNEE

211

patients

ARTHROSCOPYGROUP: MEAN RATINGSON POMS

Vigour Fatigue

Day -2

Day -1

16.2

19.5

3.50

1.30

Day 10.5 10.3

1

FACTORS

Day 2

Day 3

12.8

1I .o

8.83

8.00

Mean ratings on coping factors worry

4.51

Suppression Rational

4.94

cognition

Behavioural

action

Denial

6.50 8.98 5.29.

recorded for the Worry factor. Unlike the hip replacement group, the highest scores were found for Behavioural Action, perhaps reflecting the greater opportunities for effective behavioural coping in patients undergoing this minor operation. None of the variations across days were reliable. Nevertheless, scores were lower on the Suppression factor on Days 2 and 3 compared with earlier assessments. In contrast, Worry increased on Days 2 and 3, perhaps indicating concern about the diagnostic outcome of the surgical procedure. Preoccupation ratings did not fluctuate significantly across days (mean 2.66).

Relationship between mood, coping and autonomic response The interrelationships between subjective and autonomic responses were analysed in the hip replacement group only, since there were insufficient data points in the knee arthroscopy sample to warrant investigation. Product-moment correlations were firstly calculated between variables across days, in order to identify the autonomic parameters that reflected mood change most precisely. The significant correlations are summarised in Table III. The two measures of sweat gland activity showed the most consistent associations with mood, each correlating significantly TABLE III.-HIP

REPLACEMENTGROUP: CORRELATIONSBETWEENPHYSIOLOGICALAND PSYCHOLOGICALMEASURESACROSS DAYS

SCL vs

Tension-anxiety Depression Vigour Fatigue Confusion

I.= r= r= r= r=

-0.84 -0.83 0.73 -0.92 -0.69

Pain

r=

-0.69

Heart

Vigour Fatigue

r= r=

-0.83 0.68

Tension Pain

r= r=

0.83 0.81

rate vs

Systolic blood pressure

vs

df = 8, r > 0.63, p < 0.05 r > 0.77, p < 0.01

PSI vs

Tension-anxiety Depression Anger Fatigue Confusion

r= r= r= r= r=

-0.79 -0.79 -0.64 -0.63 -0.85

Pain

r=

-0.65

212

CLAUS V~GELE and ANDREW STEPTOE

with five of the six POMS factors. Both SCL and PSI were also negatively correlated with pain. These two patterns are not independent, since SCL and PSI correlated with each other at a level approaching statistical significance (r= 0.606, df = 8, p < 0.1). Heart rate was reliably associated with the vigour and fatigue items, while blood pressure responses were related to pain ratings. The autonomic parameters showed no significant correlation across days with any of the coping factors. However, variations in the Suppression coping factor were positively related to pain ratings (r=0.75, df = 8, p < 0.05), presumably since both were highest in the immediate perioperative period. A further set of correlations was computed to investigate inter-relationships between responses across individuals. No significant associations between POMS, autonomic responses, preoccupation ratings and coping factors were identified in this way. However, scores on the Chance subscale of the Locus of Control questionnaire were negatively correlated with reductions in SCL (r= -0.707, df = 6, p < 0.05). Patients who believed that chance had little impact on their lives reacted with greater reductions in SCL than those with high chance ratings. Finally, the two groups were combined for analysis relating preoperative preoccupation ratings with postoperative physiological response. Patients with high preoccupation ratings showed significantly greater peak reductions in SCL than those with low preoccupation scores (F(l, 12) = 6.49, p < 0.05). DISCUSSION

In order to interpret autonomic responses as psychophysiological phenomena, it is necessary to rule out potential confounding factors (such as medication and blood loss) that might account for the pattern of change. The complexity of this issue is reflected in Table IV, where it can be seen that 30 different pharmacological agents were prescribed, often in complex multiple regimens. The long-term autonomic responses to many of these agents (alone or in combination) have not been fully investigated. Nevertheless, some general inferences may be made. Premeditation was carried out within two hours of surgery. Since the preoperative assessments were performed two and one days pre-surgery, these data were unaffected by premedication. Anaesthetics, analgesics, muscle relaxants and anticholinergic agents were given during surgery itself. The endocrine responses to these agents have been reviewed by Walton [21] and Salo [22]. Many of the effects are short-lived, so unlikely to have influenced the pattern of response observed during this study. Postoperatively, patients received analgesics, anti-emetics and tranquillisers in normal clinical dosages. The number of patients taking part in this study was insufficient to make any attempt to partial out different types of medication. However, the existing pharmacological literature suggests it is unlikely that these drugs caused the tonic changes in heart rate, SCL or PSI recorded during this study. The inferences drawn from this study must be tentative, since the number of patients involved was small. The influence of repeated test sessions must also be taken into account. Despite this, it is striking that several of the autonomic parameters showed consistent patterns of response. The reduction in PSI over the days immediately following surgery confirms the observations of Harrison et al. [6]. The significant sex differences reported by these authors did not emerge in the

Stress in surgical TABLE

IV.-MEDICATIONS

PRESCRIBED

213

patients AT DIFFERENT

STAGES OF THE STUDY

Premeditation

lntraoperative medication

Postoperative medication

Diazepam Papaveretum Hyoscine

Papaveretum Pethidine Fentanyl

Papaveretum Dihydrocodeine Pethidine Ibuprofen Diflunisal Paracetamol Meprobamate Aspirin

Midazolam Thiopentone Halothane Enflurane

Tartrate

Prochlorperazine suxamethonium Vecuronium Alcuronium Curare Pancuronium

Perphenazine Metoclopramide Temazepam Diazepam

Atropine Hyoscine Neostigmine Propranolol Hydrocortisone Cephradine

present study, perhaps because numbers were insufficient. The close agreement between changes in PSI and SCL suggests that genuine alterations in sweat gland activity occur, and that the PSI responses are not artefacts of the method. These data indicate that sweat gland activity is reduced by the stress of surgery, closely following the pattern of subjective distress and pain. The interpretation of lower PSI as a decrease in stress is therefore doubtful [8,9]. Heart rate contrasted with the pattern of electrodermal response, since increases were observed in the days immediately following surgery. The discrepancy suggests that psychophysiological responses cannot be accurately gauged on the basis of a single autonomic parameter. Other investigators have observed independent control of heart rate and electrodermal responses under conditions involving pain or preparation for surgery [8]. For example, Dowling [23] reported that heart rate is positively correlated with pain reports during the cold pressor, while SCL shows a negative association. The biological mechanisms responsible for these autonomic responses are unclear. Blood pressure responses were not closely associated with mood changes in this study, although they were correlated with pain. Forearm flexor EMG did not emerge as a useful parameter of physiological response in this context. There is, however, considerable doubt about the ability of a single muscle to reflect general levels of tension, so monitoring from other sites may prove more fruitful [24]. The mood changes observed in this study are consistent with previous findings [I]. Contrary to what might be intuitively expected, anxiety is not highest presurgery, but increases in the days immediately following surgery. The high levels of

214

CLAC.~V&FLE and ANDREW STEPTOE

fatigue (and low levels of vigour) reported in the four days immediately following surgery may reflect the well-known phenomenon of postoperative fatigue [25]. These effects may be modulated by the psychological coping strategies used by patients. Folkman and Lazarus [26] have recently emphasised the importance of envisaging coping as a changing psychological state, fluctuating with the emotional and instrumental demands on the individual. Patients in the hip replacement group tended to utilise Rational Cognition as their preferred coping method throughout the study period, whereas the lowest ratings were observed for the Worry factor. The knee arthroscopy group’s preference for Behavioural Action may seem appropriate, given the diagnostic nature of this surgical procedure. Significant changes over the course of hospital admission were identified for only one of the five coping factors. This was unexpected, since psychological coping is often presumed to be situationally determined in part, and the position of patients pre- and post-operatively is very different. It may be that analyses which combine related items into coping factor scores are inadequate, since a single item may be highly relevant to an individual, and indicate intensive use of a particular strategy. The one factor score that did fluctuate, Suppression, is considered to be related to avoidant cognitions and emotion-focussed coping [18, 191. Patients utilised this method more intensively in the preoperative period and the two days immediately following surgery than for the remainder of their hospital stay. Evidently they chose to cope with the immediate trauma of surgery by trying to keep their minds off the problem. It is not known whether this is adaptive; Kaloupek et al. [27] have shown that Suppression may be related to vasovagal syncope in blood donors. Numbers were too small in the present study to permit consistent relationships between individual differences in coping and psychophysiological response to emerge. Nevertheless, a related finding of interest was the association between preoperative emotional state and postoperative autonomic response. Patients who thought about their forthcoming operation a good deal (high preoccupation ratings) responded postoperatively with greater reductions in SCL. Previous studies have shown that preoperative anxiety and worry are associated with poor adjustment postoperatively, but this has not previously been endorsed at the physiological level [2]. Comparisons between the two samples investigated in this study must be treated with caution, given the differences between groups in age and physical condition. Nonetheless, significant differences in physiological response were apparent only for heart rate, with greater increases in the group undergoing the longer and more intensive surgical procedure. It would therefore appear that as far as sweat gland activity is concerned, the severity of physical trauma is not the major factor determining response magnitude. These data suggest that detailed assessment of physiological parameters may be a valuable adjunct to the investigation of stressful medical procedures. However, many of the tonic adjustments in autonomic activity reported here may be determined by neuroendocrine substances. Future studies should therefore assess neuroendocrine and immunological parameters as well as autonomic variables, while taking rest and activity patterns and nutrition into account. Acknowledgements-This research was supported by a Scholarship from the Studienstiftung des deutschen Volkes to Claus Vbgele. We wish to acknowledge the assistance of Dianne Yarwood in data collection, and the facilities provided by the orthopaedic surgeons R. Bendall, P. R. French and R. H. Vickers, together with the staff and patients of Gunning Ward, St George’s Hospital.

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