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Differences between the VAS scores for anticipated, experienced and recalled pain were assessed by repeated measure analysis of variance.

Stepwise multiple regression assessed the predictive power of anticipation on experienced and recalled pain.

Relationships between the anticipated, experienced and recalled pain measures,

preoperative state anxiety, the PRQ scores and outcome measures were assessed by product moment correlations.

Further analysis included partial correlation and analysis o f covariance of the pain measures with state anxiety.

Results

Sim pl ee f f e c t s o fa n t ic ip a t io no fp a ino ne x p e r ie n c e d a n d r e c a l l e dp a in

Overall the patterns of mean VAS values for pain intensity and pain distress are different, (Table 6:2). Pain intensity is anticipated and recalled fairly accurately, paired T tests revealed no significant differences between the scores. Pain distress is exaggerated when anticipated and recalled, the difference between experienced pain and recall 3 days post- operatively is significant, 't' 2.1; p<0.05.

Table 6:2: M ean Values of the VAS Scores for Anticipated, Experienced and Recalled Pain

pain VAS scores (N)

Anticipated pain Experienced pain Recalled pain

1 day preop day of op postop day of op 3 days postop 30 days postop

128 99 112 90 59

intensity mcm(sd) 45.6 (24) 48.53 (24.49) 4S.6S (30.11) 46.97 (28.19) 47.47 (30.44) distress mean (sd) 39.43(27.19) 44.74 (26.76) 39.32 (29.13) 46.88 (30.22) 44.82 (33.23)

Repeated measures analysis of variance revealed a similar pattern of mean VAS values, although only 51 subjects returned sufficient data, (Table 6:3).

Table 6:3: Repeated M easures Analysis of V ariance: Anticipated, Experienced and Recalled Pain

anticipated pain experienced pain recalled pain

pain VAS scores 1 day preop day of op postop day of op 3 days postop 30 days postop intensity meanfjûfl 45.10(26.35) 1 48.77 p 5 .5 /; 46.26 (28.43) 43.32(25.74) | 48.78 (29.9%) distress mean (sd) 43.S2 (29.41) ^ 44.51 (27.04) 39.45 (28.17) 43.49 (29.29) | 45.43 (31.57)

sd. standard deviation.

The overall pattern of mean VAS values suggests that pain intensity is recalled accurately but that pain distress is not. The VAS values for anticipation and recalled pain distress are very similar, suggesting that anticipation of pain distress is influencing recall. Hierarchical multiple regression was employed to assess the predictive power of anticipation on recall. Analysis was performed using SPSS* regression, stepwise. The variables, anticipated pain on the day of operation, experienced pain and recalled pain (3 days post-operatively) were entered as respective dependent variables.

Mu l t ip l e Re g r e s s io n: An t ic ip a t e d, e x p e r ie n c e da n dr e c a l l e dp a in

The pattern of mean pain VAS values (Table 6:3) suggest that:

1) anticipation of the pain experience one day pre-operatively would predict the anticipation of pain on the day of operation.

2) The anticipation o f pain on the day of operation would predict the pain experience and in part the recalled pain experience.

3) Pain experience would predict memory.

This model is illustrated in Figure 6:2.

Figure 6:2: M ultiple Regression: M ain Effects Model

1 day pre-op. day of op. day of op. 3 days post-op. anticipated anticipated experienced recalled

p ain P; 0.32 ^ a i n p; 0 .3 4 ^ .p a in P; 0.34 ^ pain

P; 0.20

2 ) Dis t r e s s

1 day pre-op. day of op. day of op. anticipated anticipated experienced pain P;0 60 ^ p a in — P; 0 .3 9 -^ pain--- P;0.66- 3 days post-op. recalled ->pain P;0.32 p = regression coefficient.

In the case of pain our hypothesis has been met, both measures of pain were predicted by subjective anticipation.

The pattern of the regression coefficient, p (Table 6:4), indicates a significant linear effect for intensity and distress as predicted. The anticipated pain one day pre-operatively predicts anticipated pain on the day of operation which predicts the experienced pain that in turn predicts recalled pain. A difference emerges, however, between intensity and distress for the effect o f anticipation o f pain and recalled pain, the p value for intensity fails to reach

significance. In the case of pain distress the p value 0.32, between anticipation o f pain and recalled pain is of similar magnitude as that between anticipated and experienced pain, p; 0.39. (P values are illustrated on the model. Figure 6:2). For pain distress the anticipated pain is as predictive of recalled pain as experienced pain.This suggests that subjects anticipation o f pain has influence on their subsequent recall but that the effect is only important for pain distress.

Table 6:4 Multiple Regression, M ain Effects: C orrelation Coefficient, Regression Coefficients a n d ’t ’ Values

1 day pre-op. day of op.

anticipated pain anticipated pain experienced pain

pain intensity R: _P ‘t’ value R: _P ‘t’ value R: _P ‘t’ value

anticipated -1 0.32 0.57 6.12** experienced 0.08 0.21 1.29 0.07 0.34 2.62** recalled +3 0.34 0.04 0.31 0.37 0.20 1.90 0.34 0.54 6.5** pain distress anticipated -1 0.35 0.60 6.0** experienced 0.14 -0.22 -0.10 0.12 0.39 3.56** recalled +3 0.48 0.01 0.08 0.47 0.32 3.28** 0.39 0.66 7.23** *p<0.05, ♦*p<0.01

anticipated -1; anticipated pain Iday pre-op. recalled +3: recalled pain 3 days post-operative

However, when the correlation coefficient, Revalues (Table 6:4) are examined the variance accounted for is greater between anticipation o f pain on the day of operation and recalled

pain (R^ int. 0.37, R^dis. 0.47) than between anticipation o f pain and experienced pain (R^ int 0.07, R^ dis. 0.12), for both intensity and distress. This implies a more important

relationship between anticipation and recall than between anticipation and experience for both intensity and distress. Correlation coefficient (R^) values are listed in (Table 6:4).

Full factorial multiple regression revealed no significant interactions for the pain intensity model. For the distress model only one interaction, between anticipated pain on the day of operation by experienced pain, reached significance, adjusted R^ 0.48, p; 0.01, 'f 2.13**, with recalled pain as the dependent variable. This confirms that for pain distress the recalled pain is composed of experience and anticipation.

In t e r a c t iv ee f f e c t sb e t w e e nt h ep a inv a r ia b l e s, t r a ita n x i e t y, a f f e c ta n d

RECOVERY

Product moment correlations were calculated between the pain ratings, and recovery, trait anxiety, pre and post-operative state anxiety.

The pattern of correlations between anticipated pain ratings and the other pain ratings is interesting. Anticipated pain on both pre-operative occasions has stronger consistent correlations with recalled pain than with experienced pain. The pattern o f correlations between anticipation on the day o f operation and early and delayed recall is particularly strong (Table 6:5). This measure is taken at a similar time, in relation to the surgery as that reported by Kent (1986) and yields similar results.

Table 6:5 Correlations Between the Pain Measures

pain scores

anticipated experienced recalled

1 day pre-op. day of op. day of op. 3 days post-op. anticipated int 11 dis

1

int I dis ...int 1...j dis int 11 dis

1 day pre-op. dis 0.44** 11 1

1

...1 1

1 1

day of op. int 0.57** 1 0.36**1 1

1 1 1 1 dis 0.54** 1 0.58**1 0.54** 11 1 1 1 1 experienced ■ I₁ 1₁ 1₁ 1₁

day of op. int 0.37** 1 0.111 0.27** 1 0.32**1 1 1 1 1 dis 0.18 11 0.10 0.13 j 0.421 1 0.77** j r 1 recalled 1₁ 1₁ 1₁ I₁

3 days post-op. int 0.32** 1 0.26**1 0.34** 1 0.26**1 0.50** 1 0.51**1 1 1 dis 0.26** 1 0.24*1 0.42** I 0.49**1 0.53** 1 0.61**1 0.88** 11 30 days post-op. int 0.22 11 0.23 0.40** 1 0.30**1 0.40** 1 0.32**1 .... 0.50** 1 0.53**1

dis 0.23 11 0.12 0.31* I1 0.26 0.39** 1 0.38**1 .... 0.39** 1 0.47**1 *p<0.05, **p<0.01 Pain measures; int : intensity, dis : distress

Taken together the pattern of mean values, results of the multiple regression and the pattern o f correlations implicates anticipation as an important influence on pain experience

confirming the hypothesis. These results also implicate anticipation measured immediately preoperatively as an important variable influencing recall. Experienced pain also yielded strong correlations with recalled pain.