Purn. 44 (1991) 241-247 (1’ 1991 Elsevier Scxnce Publishers ADONIS 030439599100084Q

241 B.V. 0304-3959/91/$03.50

PAIN 01732

Increased

postoperative

A. Ekblom

pain and consumption acupuncture a, P. Hansson

‘.‘, M. Thomsson

’ and

of analgesics

M. Thomas

’

0 Deprrrtment of Ph_vsrologv II, Karohnska Institute. and h Department of Neurology. Karolmcka Hosplrul, Stockholm and ’ Depur~~nt OJ Oral Surgery, Slider Hospital, Stockholm (Sweden) (Received

6 June 1989. revision

received

13 August

1990. accepted

15 August

following

(Sweden),

1990)

Acupuncture was given to patients before (preoperative-acupuncture group, PRE-ACLJ, n = 25) or Summary after (postoperative-acupuncture group, POST-ACU, n = 25) operative removal of impacted mandibular third molars. Sixty patients did not receive acupuncture and participated as a control group (CG). All patients completed a questionnaire in order to characterize state tension and stress, degrees of neuroticism. extroversion, depression and psychosomatic disorders. We also recorded intraoperative discomfort and pain intensity, postoperative pain intensity and consumption of analgesics for 72 h. The PRE-ACU was significantly more tense following surgery and found the operative procedure more unpleasant than the other two groups. The PRE-ACU further rated intraoperative pain intensity higher than the CG and experienced higher pain intensity immediately postoperatively compared with POST-ACU and CG. Of the PRE-ACU patients 15/24 needed additional local anesthesia intraoperatively while none in the POST-ACU or CG requested extra lidocaine. Postoperatively patients in both PRE- and POST-ACU reported a higher total sum of pain scores (pain intensity) and the PRE-ACU consumed more analgesics compared with the CG. A significantly larger number of patients suffering from “dry socket” (a complication during wound healing) was found in both PRE- and POST-ACU compared with the CG. No correlation was found between assessed personality characteristics and reported postoperative pain/consumption of analgesics in any group and could thus not explain the observed differences between the groups. The reason for our unexpected “negative” findings is unclear but some hypothetical explanations are discussed. Key words: Postoperative

pain;

Acupuncture;

Personality

Introduction Acupuncture as a pain-relieving method has gained much interest in recent years in the West [19]. Different explanations have been put forward regarding the paininhibiting effect of acupuncture. The activation of central inhibitory mechanisms has been emphasized. A few studies have investigated the potential analgesic effect of acupuncture during surgery [e.g., 5,9] but not with respect to the postoperative period concerning pain and consumption of analgesics in relation to personality characteristics.

Correspondence 10: Anders Ekblom. Department of Physiology Karolinska Institutet. Box 60 400, S-104 01 Stockholm. Sweden.

II,

assessment:

Oro-facial

Brief periods of activity in nociceptive afferents from deep tissues produced, for example. by surgery induce excitability changes in central neurons [24]. In an editorial based on these and other results Wall [23] has stressed the importance of pre- and intraoperative measures in trying to reduce/inhibit development of this hyperexcitability of central nociceptive cells which may result in reduced postoperative pain. Two recent studies on postoperative pain have yielded interesting results. The first [18] is a review of the postoperative analgesic requirement after surgery in general anesthesia using additional opiate premeditation and/or preoperative blockades with local anesthetics compared to the requirement without its use. With the former there was a significantly longer period before its need compared to the latter. The second study [3] reported a significant

reduction in phantom limb pain following amputation when lumbar epidural blockade was used to reduce pain prior to the operation. If acupuncture operates by lowering excitability in nociceptive neurons, thereby reducing central nociceptive transmission, it should theoretically be possible to reduce postoperative pain by giving acupuncture before or shortly after the surgical trauma, A prerequisite, at least for acupuncture given preoperatively, is that the effects induced by acupuncture outlast the stimulation period, as found in both experimental and clinical studies [2,19]. In the present study we have compared the pain-reducing effect of preoperative acupuncture with acupuncture given early in the postoperative period in comparison with a control group, with regard to the total postoperative period. The effects of acupuncture have further been correlated with personality characteristics investigated preoperatively, and with the consumption of analgesics during the postoperative period.

Preoperatively the patients completed it qtx:stlvnnaire (see below) aimed at characterizing some personaEity factors. They then received a batch of visual analogue scales (V-AS) and were instructed to rate the pain intensity p~~stoperatively once every hour icxcept for periods of sleep) for 72 h. They were ajso asked to document time and amount of analgesics ingested in the pain diary (on a reserved area next to the corresponding VAS). All patients were provided with 20 tablets. each containing either acetylsalicylic acid (500 mgf -t codeine (30 mg) or acetaminophen (500 mg) + codeine (30 mg). Doses recommended were 1 --2 tablets 1 -4 times .,‘day. Additional analgesics were supplied on demand. All patients were operated on between 8 am. anti 11 ;t.tn. One patient in the PRE-ACU discontinued acupuncture due to discomfort resulting from vaso-vagal symptoms. and was therefore excluded from the study.

Material and methods Putients In total 110 patients participated and were assigned to 1 of 3 groups (see below). Fifty patients, 25 males and 25 females aged 18-50 years (mean age 29.9 years, median age 28.0 years), received acupuncture. Sixty patients, 38 males and 22 females, aged 18-55 years (mean age 30.2 years, median age 31.2 years) participated in a control group. All patients had been referred to the clinic for oral surgery by their local dentist for operative removal of an impacted mandibular third molar tooth. No patient had had any pain from the molar region for less than 3 months before surgery. The patients were informed about the study and asked if they wanted to participate. All patients accepted and were informed that they could end their participation at any time. Only 2 patients had been exposed to acupuncture treatment before entering the study. After examination the patients were randomly assigned into 1 of 3 groups: a preoperative acupuncture group, PRE-ACU (n = 25); a postoperative acupuncture group, POST-ACU (n = 25); and a control group, CC (n = 60). They were informed that acupuncture was being tested in order to evaluate the effect on the postoperative pain normally associated with that type of surgery. Care was taken to avoid any suggestion of a special beneficial effect of acupuncture. The CG was subjected to the same procedures as the two acupuncture groups, except that these patients did not receive any acupuncture. The data from these patients concerning the natural course of pain development and the consumption of analgesics have been extensively presented elsewhere [lo]. The use of a separate control group gave us the possibility to study the extent of

Follow-up After 1 week the patients visited the surgeon for a postoperative examination. On this occasion all data were collected from the patients. One author (Thomsson) examined and operated on all patients. All data collected were primarily evaluated by others than those directly in contact with the patients.

Preoperatively on the day of surgery all patients completed a questionnaire consisting of 4 parts. The intention was to characterize some personality factors as well as to record the patients’ expectations of the surgical procedure and postoperative pain. (1) The degree of state tension and stress (state anxiety was determined by the words tension and stress according to their meaning in the Swedish language) was estimated before acupuncture and operation (PREACU), before operation (POST-ACU and CG) and directly following surgery (all groups). This was performed using a separate VAS for each tested aspect. The VAS consisted of a horizontal line (10 cm) on a card with, for example, the words “no tension at ail” and “worst tension ever” placed at the left and right extreme ends of the line, respectively. In addition, the patients rated the expected overall intraoperative pain intensity. Directly after surgery they scored their present pain intensity, the discomfort experienced during the surgical procedure and the overall pain intensity experienced during surgery. These questions were answered using separate sets of VA%. (2) Eysenck’s short questionnaire was completed for the measurement of two dimensions of personality. i.e.. degrees of extrovertness and neuroticism.

243

-ST 7

ST

Fig. 1. Localization

L.I.

LARGE

ST

STOMACH

INTESTINE

S.I.

SMALL

S.J.

SANJIAO

INTESTINE (TRIPLE

of acupuncture points ing stimulation.

LARMER)

used in all patients

receiv-

(3) World Health Organization collaborative study on strategies for extending mental health care: instrument 2 (General Health Questionnnaire) was completed. This test reflects somatic, psychological and psychosomatic disorders as well as the subjects’ view of themselves. If psychotic symptoms are present these are also roughly investigated by the test. (4) Beck’s Hopelessness Scale, containing 20 questions regarding the subjects view of their future. The answers from the personality tests 2-4 were dichotomized and were recorded as yes (1) or no (2). Technical aspects on acupuncture PRE-ACU. These 25 patients received acupuncture after completing the questionnaires on personality aspects. They received 5 needles in the following locations according to traditional acupuncture points (see Fig. 1): ST 6. ST 7, a point in front of the tragus of the ear (S119) and distally in the hand (LI4), all four ipsilateral to the site of surgery, and at SJ5 contralaterally. The needles were inserted to a depth of approximately 0.661.3 cm using sterile procedures similar to those used for intravenous infusions. All needles were manually stimulated (the needle was rotated backwards and forwards through 180°) every 5 min for about 10 sec. thereby eliciting a non-painful sensation, deQi. This sensation is described in Chinese literature as a local

tenseness or numbness, or other types of discomfort including a radiating sensation, but not amounting to pain. The needles were left in place for 20 min. Surgery was commenced less than 10 min after cessation of acupuncture. POST-ACU. 25 patients were included in this group. Acupuncture was started 2-4 h following surgery (mean time 2.7 & 0.63 h). i.e., when the effect of the local anesthesia had worn off. No patient had any subjective feeling of persisting effect of the local anesthesia, and 12 out of the 25 patients experienced postoperative pain of varying intensity when acupuncture was started. No patient in this group had taken any analgesics before the start of stimulation, an inclusion criterion in this group. The stimulation technique was the same as in the PRE-ACU group. The effect of acupuncture considering the patients’ “response to stimulation” was crudely assessed by the acupuncturist (Thomas), at the time of administration. The degree of state anxiety resulting from the fact that the patients were to receive acupuncture and to be subjected to surgery was recorded as present or not. The response to stimulation, i.e., the ease with which deQi was induced at each acupuncture point during needle insertion/stimulation, was recorded as poor (took > 20 set), fair (lo-20 set), or good ( < 10 set); the sedative effect of acupuncture was recorded by comparing alertness against a degree of drowsiness; the difference in heart rate was determined by counting the pulse before and after acupuncture but prior to the removal of the needles and was expressed in beats/min. Technicul aspects on the operation All teeth were located in the mandible and were covered by bone. No sedatives were used pre- or postoperatively. The local anesthetic used, lidocaine with epinephrine (20 mg + 12.5 pg/ml), was given initially in the amount of 3.6 ml/patient using standard procedures. The operation included gingival and periostal incision, mucoperiosteal flap dissection, bone removal and splitting of the crown/root to facilitate removal. Bone was removed using a drill constantly cooled with physiological saline. The duration of surgery did not exceed 15 min in any patient. The study was approved by the local ethical committee. Statistical methods The obtained data were analyzed using standard methods such as the chi-square test including Fisher’s exact test when appropriate. Student’s t test, and Pearson’s coefficient of correlation (r). The total sum of pain scores/l2 h periods was analyzed using a l-way analysis of variance with repeated measures (ANOVA). A probability level of P < 0.05 (type I error) was considered significant. We arbitrarily considered it reasonable to be able to detect a “true” difference of

50-80s in the measured variables between CG and the other groups having choosen a type II error of 0.20 or less (beta value). This gave us a power of at least 80% (I - beta).

Results

In the questionnaires completed by aI1 patients regarding personality factors, there were no differences between any of the groups except for one aspect. Before operation and before receiving acupuncture, the patients in the POST-ACU were significantly more tense compared to the patients in the CG (Table I). Following surgery the patients’ ratings showed that the PRE-ACU was significantly more tense than the POST-ACU or the CC (Table I& When the change in state tension and stress pre- vs. postoperatively was calculated fur each group it was found that the PRE-ACU did not decrease significantly in tension and stress compared with the other two groups. The patients in the POST-ACU reported a significantly greater decrease in tension compared to the patients in the PRE-ACU (29.8 k 28.93 vs. -2.5 & 43,57, P -c0.004) and the CG (29.8 + 28.93 vs. 9.1 3~ 45.30, P < 0.02). The correlation between the facand “stress” was significant in all 3 tors “ tension” groups (PRE-ACU r = 0.65, P < 0.001; POST-ACU r = 0.59, P c 0.01; CG r = 0.28, P < ct.05).

Before the start of acupuncture there was no difference in state tension and stress between the two acupuncture groups, and the response to stimulation was equal in the two acupuncture groups as assessed by the acupuncturist. There was, however, a significant difference in drowsiness following acupuncture, with a greater effect in the PRE-ACU compared with the POST-ACU (0.6 _C0.51 vs. 0.2 _t 0.44, P +c0.03). In the PRE-ACU there was a significant correlation between and “drowsiness” f r = 0.61, “response to stimulation” P -c 0.01) which was not found in the POST-ACU (P = 0.35). There was no significant difference in heart rate

TABLE

decrease in the PRE-AC’U compared (4.7 i 3.17 vs. 3.1 rt: 3.45. P - 0.07).

to the H)S t‘-.+li‘!

All patients were asked preoperativelv to rate how painful (intensity) they thought the operation would he. There was no significant difference between the 3 groups with VAS ratings varying between 41 and 47 mm. iill patients further rated-the degree of unpleasantness and pain intensity experienced during the surgical proccdure. Interestingly, the patients in the PRE-Ai’U found the procedure significantly more unpleasant than did the patients in both the POST-ACU and the C‘G (Table II). There was no significant difference between the two acupuncture groups regarding intraoperativc pain intensity, but the PRE-ACU reported a significantly higher pain intensity than the CC. There was a significant correlation between unpleasantness during operation and intraoperative pain intensity experienced in the PRE-ACU (,r = 0.57, P < 0.01) and in the CCi- ( r =y~ 0.35s P < 0.01) but not in the POST-AC\! 4 !’ z-r0.01, n.s.1. Directly following surgery all patients rated their pain intensity level. Once more it turned out that the PREACU experienced significantly more pain than the POST-ACU and the CG. The correlation between pain intensity experienced during operation and pain rcported directly following operation was significant in both acupuncture groups (PRE-AC’U r’r=-,0.88, P c’ 0.001; POST-ACU r = 0.52, P ( 0.011, In the PRE-ACU 15/24 patients needed additional local anesthesia due to the pain experienced during surgery: 9 patients were given 1.8 ml extra and 6 patients received 3.6 ml extra. Additional fidocaine was not needed in either of the other two groups. Postoperutiue pain, consumption of mut~esics und wound healing After the operation the patients recorded their present pain intensity hourly for 72 h and the total sum of the pain scores was calculated (Table III>. The tot& sum of pain scores was significantly higher in both the PRE-ACU and the POST-ACU compared Eo the CC;

I

DEGREE QF TENSION AND STRESS (state anxiety) IN THE DIFFERENT (group mean & SD.)

GROUPS OF PATIENTS

BEFORE

AND AFTER -___-.-^

Groups

PRE-ACU POST-ACU CC

Stress

Tension Preop

Postop

Prmp

42.5 + 33.20 53.1 t 26.46 a 37.2 & 30.13

45.0 Ifi 26.clS bs 23.3 -t_19.35 28.1 * 30.04

2&S f 30.47 34.8 * 31.48 24.3 i 30.81

a POST-ACU vs. CG, P -=z0.02. ’ PRE-ACU vs. POST-ACU. P ( 0.002. ’ PRE-ACU vs. CG, P -c 0.03.

UPERA’I’ION

-.I_. ..i--

- .-.

---

____^-..--___._... _ Postop

_._.-__--------17.9 * 27.04 13.0 _t 16.40 13.3 + 18.05 ~_~~_.~-~~~~~~..~~-_~~

245 TABLE

II

INTRAOPERATIVE UNPLEASANTNESS AND SITY AS WELL AS PAIN INTENSITY DIRECTLY SURGERY (group mean values f S.D.)

PAIN INTENFOLLOWING

Intraoperatively Unpleasantness

Pain intensity

Pain intensity

PRE-ACU POST-ACU CC

49.1 + 32.80 a.h 30.2; 31.42 23.8 f 25.72

36.9 k 32.27 ’ 29.X + 30.89 20.9 + 28.80

26.6 f 32.39 ‘.’ 11.4k14.75 11.2t17.88

PRE-ACU PRE-ACU PRE-ACU PRE-ACU PRE-ACU

vs. vs. vs. vs. vs.

POST-ACU, P < 0.05. CC, P < 0.05. CC, P i 0.04. POST-ACU. P < 0.04. CG. P < 0.03.

but there was no significant difference between the two acupuncture groups. The total sum of pain scores for each 12 h postoperative period in each group of patients is seen in Fig. 2. A significant group/time relationship was found (F (10. 535) = 2.4, P < 0.008, ANOVA). The number of patients in each group not reporting any postoperative pain were l/24 (4%) in the PRE-ACU, 2/25 (8%) in the POST-ACU, and 9/60 (15%) in the CC, non-significant differences. The consumption of analgesics was also recorded during these 72 h; the PRE-ACU consumed significantly more analgesics than the CC but no significant difference was found between the acupuncture groups (Table III). The number of patients nof consuming any analgesics at all were 5/24 (21%) in the PRE-ACU, 7/25 (28%) in the POST-ACU, and 28/60 (47%) in the CC (non-significant differences). The correlation between the total sum of pain scores and total amount of consumed analgesics was significant in all 3 groups (Table III). However, no correlation was found between total sum of pain scores/consumption of analgesics postoperatively and preoperative tension and stress, scores on personality inventories (Beck, Eysenck or General Health Questionnaire), expectations on how

TABLE

x POST o CG

Postoperatively

Group

* ’ ’ ’ e

. PRE

111

O-12

13-24

25-36

37-46

49-60

61-72

TIME

(hours)

Fig. 2. Total sum of pain scores/l2 h and number of patients reporting pain in the 3 groups. Vertical bars indicate standard deviation (SD.). Number of patients indicated above vertical bars. Significant differences in total sum of pain scores between groups: * P c 0.05, * * P < 0.04; t test. The dashed line connects 12 h values for the control group (CC).

painful the surgical procedure would be, or experienced intraoperative pain intensity. A complication of wound healing in the type of surgery used is “dry socket.” Its occurrence in the present study was different in the 3 groups (Table IV). The two acupuncture groups differed significantly compared to the CC but there was no significant difference between the acupuncture groups (P < 0.19).

Discussion Acupuncture is a pain-relieving method reported to decrease experimental and clinical pain (2,191 and to induce analgesic effects during oral surgery [5]. In the present study, however, we found an increase in postoperative pain intensity following acupuncture treatment which correlated significantly with an increased consumption of analgesics. It should be noted, however,

POSTOPERATIVE PAIN INTENSITY DURING ENTIRE OBSERVATION PERIOD (TOTAL SUM OF PAIN SCORES) AND CONSUMPTION OF ANALGESICS (group mean f S.D.) WITH INTERCORRELATION INDICATED BY PEARSON’S COEFFICIENT OF CORRELATION (r)

TABLE

Groups

DISTRIBUTION OF PATIENTS WITH DEFECTIVE WOUND HEALING (‘DRY SOCKET’) IN THE DIFFERENT GROUPS

PRE-ACU POST-ACU CG

a PRE-ACU ' PRE-ACU

Total sum of pain scores

Analgesics

573.8 & 515.69 * 485.4 k 521.94 ’ 250.5 * 303.58

4.1 * 3.96 h 3.0 * 3.40 2.0 + 2.86

vs. Cc;. P < 0.01. vs. CC. P < 0.03. ’ POST-ACU vs. CC. P < 0.05.

Correlation

IV

(r) 0.65: P < 0.001 0.43; P < 0.05 0.78; P -c0.001

Group

‘Dry socket’

Normal healing

PRE-ACU POST-ACU CG

7” 3h 0

17 22 60

= PRE-ACU vs. CC. P < 0.0003 ’ POST-ACU vs. CC. P < 0.03.

wound

246

that these findings were detectable because we used a separate control group, which enabled us to compare the effects of acupuncture with “untreated” patients. Thus, the two acupuncture groups did not always differ significantly from each other but they deviated in some respects from the controls. A study including a control group to quantify the natural course of a condition increases the sensitivity of the study. The study was designed to investigate whether we could obtain a more powerful analgesic effect using acupuncture before the trauma or early in the postoperative period. The idea was to activate endogenous paininhibiting mechanisms before or shortly after presenting the nociceptive stimulus, i.e.. surgery. It has been found that a short barrage of impulses in nociceptive afferents due, for example, to operative procedures, could induce prolonged activity and increased responsiveness in central neurons [24]. Preoperative activation of endogenous pain-controlling systems by acupuncture, for example, could hypothetically be supposed to reduce/inhibit such central changes. resulting in less postoperative pain. Since acupuncture has been reported [S] to induce analgesic effects when used during oral surgery, although not in every case 191, acupuncture given before surgery might also be expected to lead to a less painful and more comfortable surgical experience as well as postoperative period for the patient. On the contrary and quite unexpectedly, it turned out that with acupuncture the patients experienced increased intra- and postoperative pain in comparison with the control group. The reason for our “negative” findings is as yet unclear, as discussed below. (1) It has been shown that certain personality characteristics, e.g., state/trait anxiety and the degree of neuroticism, correlate positively with postoperative pain and/or the consumption of analgesics [l&21]. We could not, however, find a significant correlation between the assessed personality characteristics and pain intensity in any of the 3 groups studied, in conformity with an earlier study [lo] and supported by others [13]. Furthermore, there was no difference between the groups concerning preoperative expectations of intraoperative discomfort and pain. These assessments therefore do not indicate any difference in preoperative bias between the different groups. (2) We previously observed a significant drop in state tension and stress (state anxiety) preoperatively compared with postoperatively [lo] which we did not find in the PRE-ACU in the present study. It was our impression, however, although not studied in detail, that there was some mental relaxation induced by acupuncture. With crude observation techniques we noted a significantly higher degree of drowsiness in the PRE-ACU following stimulation but before surgery than in the POST-ACU following stimulation postoperatively. An has also been “acute sedating effect” of acupuncture

reported bt others in pattenth recel\-lrtg t~~atntcnt i’(.:ichronic pain /i6] or tension headache 141 f’ollowing :t single acupuncture treatment. ’ stress was not rated hv the PRE-AC’U patients hetwcen acupuncture and surger!, .4lthough postoperative pain and ~~c:nsut’nptron of analgesics increased in both groups receivrnp acupuncture, there were also significant differences between the groups in their immediate ratings aftcj surgery. The PRE-ACU rated surgery significantI! more unpleasant and more painful and experienced more pain tm-mediately following surgery than did either the POSTACC! or the C’G. is it possible that the PRE-AC’Lr patients actually experienced greater distress during surgery. or was it a reflection of ;LII expectation of benefit from acupuncture being belied? Could ;L ‘“relax.. ing” effect from acupuncture be unfavourable prroperatively? Is preoperative mental stress C.ruci;tl for the activation of endogenous pain-inhibiting \vstcrnb important for postsurgical pain inhibition? A correlation between anxiety (stress) and plasma beta-end~)rphir~ levels during operative removal of impacted third molars has been reported fll]. These authors found a negative correlation between plasma beta-endorphin levels during surgery and intraoperative pain. Following surgery. however, endorphin levels have been found to increase in parallel with the onset of postoperative pain although anxiety was unchanged [12]. It might therefore be suggested that part of the increased pain experienced by the acupuncture groups, especially the PRE-‘4CU. was due to mental relaxation (a reduced state ~)f anxietyi following acupuncture and a concomitant reduction in “natural activation” of endogenous pain-inhibiting systems. The higher degree of tension reported by the PRE-ACU following surgery in comparison with the POST-ACU and the CG might, on the other hand, have further increased their postoperative pain since it is known that anxiety and pain are positively correlated [25]. These hypothetically different effects of anxiety and anxiety reduction are interesting and call for further work. (3) It has been shown both in healthy subjects and in pain patients that activity in the sympathetic system can be modulated by afferent stimulation such as acupuncture I&] and transcutaneous electrical nerve stimulation [1,7,14,20] with a resulting sympatholytic effect. The effect of afferent stimulation has been correlated in animal experiments with a reduction in activity in sympathetic efferent fibers and a release ol‘ vasodilatory peptides from sensory fibers [15]. An acupuncture-induced vasodilatory effect with concomitant changes in intra/postoperative bleeding could lead to local complications in wound healing and increase in postoperative pain. Interestingly we found a significantly increased incidence of “dry socket” (a painful focal acute osteitis, a complication normally found in this type of surgery in CJnf0rtUni~ttJ!~.

tcnstrw

241

only l&3% [22]), in both the PRE- and POST-ACU compared to the CG. If vasodilation was induced by acupuncture in these patients it might explain the increased intraoperative pain experienced as well as the extra amount of local anesthesia needed in the PREACU. Vasodilation would lead to a faster wash-out of local anesthetic thereby shortening its effective duration, resulting in increased intraoperative pain and increased use of anesthetics: a hypothesis supported by the present findings. (4) Our results might of course also have been influenced by the acupuncture technique used. Several possibilities exist as to which acupuncture points to use in different situations, although a segmental stimulation relative to the painful area seems to be preferred [17,19]. We did stimulate several acupuncture points intrasegmentally although our choice of points and the number used might have been suboptimal. It is difficult, however, to evaluate these factors since opinions vary between different authors [ 171. In conclusion, our data indicate that acupuncture given preoperatively or early in the postoperative period after the surgical removal of impacted third molars is accompanied by increased pain and more complications. Therefore acupuncture is not recommended as an adjuvant in this type of elective surgery. The mechanisms responsible for the observed negative effects are at present conjectural.

Acknowledgements

We thank Elisabeth Berg at the Department of Medical Information Processing, Karolinska Institutet, for valuable comments on statistics. This study was supported by the Karolinska Institutet Foundation, Stockholm County Council, and the Swedish Dental Association, Tove Nilsson Foundation for Medical Research.

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