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Electroacupuncture analgesia in dogs: is there a difference between uni- and bi-lateral stimulation?
Veterinary Anaesthesia and Analgesia, 2008, 35, 52–61
doi:10.1111/j.1467-2995.2007.00347.x
RESEARCH PAPER
Electroacupuncture analgesia in dogs: is there a difference between uni- and bi-lateral stimulation? Renata N Cassu* DVM, PhD, Stelio PL Luna* Se´rgio N Kronka MSc, PhD
DVM, PhD, Diplomate ECVA,
Rosana MO Clark*
DVM, PhD
&
*Department of Veterinary Surgery and Anaesthesiology, Faculty of Veterinary Medicine and Animal Science, FMVZ, Unesp, Botucatu, SP, Brazil Department of Statistics, Bioscience Institute, Unoeste, Presidente Prudente, SP, Brazil
Correspondence: Stelio Luna, Department of Veterinary Surgery and Anaesthesiology, School of Veterinary Medicine and Animal Science, FMVZ, Unesp, 18618-000 Botucatu, SP, Brazil. E-mail: [email protected]
Abstract Objective To compare the analgesic effect of uniand bi-lateral electroacupuncture (EA) in response to thermal and mechanical nociceptive stimuli and to investigate the cardiorespiratory, endocrine, and behavioral changes in dogs submitted to EA. Study design Prospective, randomized cross-over experimental study. Animals Eight adult, clinically healthy, cross-breed dogs, weighing 13 ± 4 kg. Methods Dogs underwent electrostimulation at false acupoints (T-false); bilateral EA at acupoints, stomach 36, gall bladder 34 and spleen 6 (T-EA/bil); unilateral EA at the same points (T-EA/uni) or were untreated (T-control). All animals received acepromazine (0.05 mg kg)1) IV; and heart rate, pulse oximetry, indirect arterial blood pressure, respiratory rate, PE¢CO2, rectal temperature, and plasma cortisol concentration were measured before, during, and after EA. Analgesia was tested using thoracic and abdominal cutaneous thermal and mechanical stimuli, and an interdigital thermal stimulus. Behavior was classified as calm or restless. Analysis of variance for repeated measures followed by Tukey’s test was used for analysis of the data. 52
Results There were no cardiorespiratory differences among the treatments. The cutaneous pain threshold was higher after EA, compared with false points. The latency period was shorter and analgesia was more intense in T-EA/bil than T-EA/uni, when both were compared with T-false and T-control. Six out of eight animals treated with EA were calm during treatment, and 5/8 and 4/8 of the T-false and T-control animals, respectively, were restless. Latency to interdigital thermal stimulation increased in T-EA/bil compared with the others. There was no difference in plasma cortisol concentrations among the treatments. Conclusions Bilateral EA produced a shorter latency period, a greater intensity, and longer duration of analgesia than unilateral stimulation, without stimulating a stress response. Clinical relevance Bilateral EA produces a better analgesic effect than unilateral EA. Keywords bilateral, dog, electroacupuncture, unilateral.
Introduction Acupuncture is among the many treatment options for pain in clinical veterinary practice. The advantages of acupuncture are that it is practical, safe,
Electroacupuncture analgesia in dogs RN Cassu et al.
less expensive, and with fewer side effects when compared with conventional pharmaceutical management of pain. The disadvantages are that a specific knowledge of the subject is necessary and that the response among individuals may vary. The first surgical procedures using electroacupuncture (EA) were reported in the early 1970s in humans and animals (Vierck et al. 1974; Kothbauer 1975; Roccia & Franco 1977; Zaslavskii et al. 1977; Barbieri et al. 1979; Caracausi 1979). Electroacupuncture is also indicated for the treatment of chronic diseases, peripheral and central nervous system disturbances, and acute and chronic pain (Wynn et al. 2000). A few reports suggest that the analgesia induced by acupuncture is caused by stress because increased plasma cortisol and ACTH concentrations may be observed after EA (Stellpflug et al. 1978; Cheng et al. 1980; Lee et al. 1982; Bossut et al. 1983). However, other studies have dismissed these findings, as analgesia is observed regardless of the presence of a stress response (Pellegrin et al. 1980; Masala et al. 1983; Pullan et al. 1983; Luna & Taylor 1998). Bilateral acupuncture is usually recommended for general clinical purposes, including pain relief (Dorman & Gage 1978; Wright & Mcgrath 1981). However, unilateral stimulation may be an alternative to simplify the technique (Still 1987), as the animals might be maintained in lateral recumbency during treatment and the technique would be less time consuming, as the number of needles would be reduced by half. The aim of this study was to compare the analgesic effects of uni- and bi-lateral EA in response to thermal and mechanical nociceptive stimuli, as well as to investigate the cardiorespiratory, endocrine, and behavioral changes in dogs submitted to EA.
(n ¼ 8) – EA at false acupoints close to real points in the right hind limb; T-EA/bil (n ¼ 8) – EA at stomach 36 (ST36), gall bladder 34 (GB34), and spleen 6 (SP6) acupoints, bilaterally; T-EA/uni (n ¼ 8) – as for T-EA/bil but unilaterally in the right hind limb (Fig. 2). The Tsu-san-li (ST36) acupoint is located 3 cun (1 cun ¼ width of the last rib) distal to the lateral head of the fibula. The acupoint Yangling-chuan (GB34) is located at the proximal end of the interosseous space between the tibia and fibula and the acupoint San-yin-chiao (SP6) is located 3 cun proximal to the medial malleolus, at the caudal border of the tibia, close to the medial saphenous vein (Fig. 2). The false points were selected in areas close to the real points, making sure that they were not points of other principal meridians. According to that, the false ST36, GB34, and SP6 points were located in the longus digital extensor and deep digital flexor muscles, and caudal border of the calcanean (Achilles) tendon, respectively (Fig. 3). All animals were maintained in left lateral recumbency. Except for the untreated animals (control), the 30 · 0.25 mm needles (Suzhou Huanqiu Acupuncture Medical Appliance, Beijing, China) were introduced in the above points and the electrodes were attached to the body of the needles.
Materials and methods This study was approved by the Animal Research Ethical Committee, under protocol number 43/ 2002. Seven females and one male clinically healthy cross-breed dogs, weighing 13 ± 4 kg were sedated with 0.05 mg kg)1 of acepromazine IV. The region from the manubrium to the pubis was shaved and divided bilaterally into 12 squares of 25 cm2 each (Fig. 1). Thirty minutes after sedation, each animal underwent four different protocols at weekly intervals, using a random order of treatments: T-control (n ¼ 8) – no treatment; T-false
Figure 1 Diagram showing the thoracic and abdominal ‘squares’ used to investigate cutaneous analgesia: 1, 2, 3, 4, 5, and 6 (pre-umbilical), 7, 8, 9, 10, 11, and 12 (retroumbilical), 1, 4, 7, and 10 (right side), 2, 5, 8, and 11(midline), 3, 6, 9, and 12 (left side).
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Electroacupuncture analgesia in dogs RN Cassu et al.
GB 34 ST 36
SP 6
Figure 3 Location of false points. From: Acupuncture points and meridians in the dog, Janssens & Still, Stittsville, Ontario, Canada, 1995.
Figure 2 Location of ST36, GB34, and SP6 acupoints. From: Acupuncture points and meridians in the dog, Janssens & Still, Stittsville, Ontario, Canada, 1995.
twitching. After that, the electrical current intensity was reduced until the animals were comfortable again, but still maintaining local muscle contraction. Electrostimulation was performed for 60 minutes. The mechanical and thermal nociceptive responses were investigated at 30 and 60 minutes after beginning the electrical stimulation, and 30 and 60 minutes after the end of electrical stimulation. The experimental sequence is described in Fig. 4. The following measurements were performed: heart rate, ECG; pulse oximetry (with the sensor on the vulva or prepuce); respiratory rate and capnography (with the sampling collecting tube in the nostrils); rectal temperature (Datex Engstrom,
An alternating square wave dense/disperse 0.2 ms (10–1000 Hz) continuous electrical stimulus was used (Electronic Acupuncture WQ-6F, Beijing, China). For T-EA/uni, the same electrical source of stimulation was used for the points GB34 and SP6 and another source was used for ST36, with the second electrode placed on the skin pleat caudal to the achilles tendon. For T-EA/bil, the same electrical source of stimulation was used for GB34 and SP6 on one side, another source for the other side, and another source was used for bilateral stimulation of ST36 acupoints. The EA equipment was turned on and the intensity of the electrical current stimulation started from zero and increased slowly until the animals showed signs of discomfort and presence of
Electroacupuncture or untreated (control)
–30
IV ACP
–15
0
15
30
45
60
75
90
105
CR Cortisol pain
CR
CR pain
CR
CR Cortisol pain
CR
CR pain
CR
120
CR pain
Figure 4 Experimental sequence of EA, blood sampling, cardiorespiratory measurements, and pain scoring in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/unil) and untreated dogs (T-control). IV ACP: IV administration of acepromazine, cortisol: blood sampling for cortisol measurement, CR: cardiorespiratory measurements, pain thermal and mechanical stimuli applied and response evaluated. 54
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Electroacupuncture analgesia in dogs RN Cassu et al.
Ohmeda Division, Finland); indirect arterial blood pressure, (with the width cuff about 40% of the circumference of the antebrachium) (Dixtal DX 2710; Biomedica, Manaus, Brazil); and plasma cortisol concentration, using a solid phase radioimmunoassay (Coat-A-Count Cortisol – DPC, USA). Somatic analgesia was evaluated using the thermal (Thermoalgimeter, Iope Precision Instruments, Sa˜o Paulo, Brazil) and mechanical nociceptive stimuli, applied to the thoracic and abdominal regions (Fig. 1). The thermal stimulus was applied using a blunt probe at 52 C and the mechanical stimulus was applied using forceps protected with rubber, squeezed until the animal reacted or until the first ratchet of the forceps had been reached. The thermal and mechanical stimuli were applied until the animal reacted or for up to a maximum of 10 seconds. The following score was used: 0 ¼ no response (animals remained in sternal or lateral recumbency, with no response), 1 ¼ reduced response (slight reaction after stimulation, raising the head and looking at the area of stimulation, without vocalization), 2 ¼ normal response (quick and strong reaction against stimulation, trying to bite the metal probe or the forceps, with vocalization). The response was observed in each square and the scores were summed from the left, right, and midline areas in a total of 12 squares, rostral and caudal to the umbilicus. The possible maximum score was 24, with a normal response obtained in all measurements (Fig. 1). The thermal stimulus was also applied to the interdigital space of the fore limbs for a maximum of 10 seconds, measuring the time in seconds until a withdrawal response. Behavior was observed and considered as calm/ sedated, when animals were asleep and cooperative, or restlessness for the animals that were impatient and restless during the experimental procedure. The pain and behavior scores were assessed by an individual who had not inserted the needles. Statistical analysis was performed using analysis of variance with the F test followed by Tukey’s test using Graphpad software (San Diego, CA, USA), to investigate differences between treatments at each time, differences in time for each treatment, and interaction between treatment and time. A p-value less than 0.05 was considered significant. When the factors treatment and time were dependent, interaction was further investigated to study 1) effects of time for each treatment and 2) effects of treatments at each time (Table 2). When interaction between treatment and time was not observed (p > 0.05),
these two factors (treatment and time) were independent, according to that, 1) the mean of each treatment was calculated considering all times and 2) the mean of each time was calculated considering all treatments (Table 3). A chi-square test with Yates correction was used to compare the differences in behavior (Banzatto & Kronka 1995). Results There were no differences between the treatments for the cardiorespiratory variables (Table 1) and the values were within the normal range for dogs. Temperature decreased over time in all treatments. The number of sedated animals in T-EA/bi and T-EA/uni was significantly greater than in T-false. There was no difference between the control treatment and the others. Seventy-five percent of the animals were calm during and after bilateral and unilateral EA. On the contrary, 5/8 T-false and 4/8 T-control animals were agitated and responded intensely to the nociceptive stimuli. Bilateral EA reduced the response to thermal cutaneous stimulation at 30–120 minutes when compared with the baseline values. Unilateral EA reduced the response to thermal cutaneous stimulation, at 60–120 minutes when compared with the baseline values but did not change responses to mechanical stimulation. Bilateral EA reduced the response to cutaneous thermal stimulation when compared with false EA and control animals from 30 to 120 minutes and at 90 minutes, respectively (Table 2). Unilateral EA reduced the response to cutaneous thermal pain stimulus only when compared with false EA at 60 and 120 minutes after the beginning of EA. Both bilateral and unilateral EA reduced the response to the cutaneous mechanical pain stimulus when compared with the false treatment. The control treatment values were intermediate (Table 3). The time to response after the left and right interdigital thermal stimulus was longer 30 minutes after the beginning of EA in the bilateral treatment, when compared with the other treatments (Table 2). The latency was also increased over the false group on the left at 30, 60, and 90 minutes and on the right at 90 and 120 minutes. The interdigital stimulus was different between the control and the bilateral stimulation at 30 minutes, but the difference was only statistically significant for the right side at 60 and 90 minutes. There was a statistically significant difference between the
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Electroacupuncture analgesia in dogs RN Cassu et al.
Table 1 Mean (SD) heart rate (HR), mean arterial blood pressure (MAP), respiratory rate (RR), end tidal CO2 (PE¢CO2), and rectal temperature (C) in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
Minutes
0
15
HR (beats minute)1) T-false 98 ± 24 T-EA/bil 96 ± 22 T-EA/uni 94 ± 15 T-control 91 ± 17 MAP (mmHg) T-false 86 ± 16 T-EA/bil 87 ± 21 T-EA/uni 83 ± 16 T-control 86 ± 17 RR (breaths minute)1) T-false 30 ± 19A T-EA/bil 21 ± 11 T-EA/uni 22 ± 10 T-control 27 ± 12A PE¢CO2 (mmHg) T-false 29 ± 10A T-EA/bil 34 ± 6 T-EA/uni 30 ± 5 T-control 29 ± 5A Temperature (C) T-false 38.7 ± 0.5A T-EA/bil 38.9 ± 0.5A T-EA/uni 38.8 ± 0.3A T-control 38.9 ± 0.5A
30
45
60
75
90
105
120
90 81 89 83
± ± ± ±
10 12 110 21
101 85 88 83
± ± ± ±
25 20 17 18
88 84 96 88
± ± ± ±
19 16 18 23
85 90 87 81
± ± ± ±
21 30 19 17
93 101 84 91
± ± ± ±
23 31 11 20
85 84 84 88
± ± ± ±
21 15 16 25
82 84 87 80
± ± ± ±
16 15 14 26
83 94 85 77
± ± ± ±
20 17 20 19
89 77 83 83
± ± ± ±
13 24 16 18
84 82 89 82
± ± ± ±
9 20 13 11
86 87 87 79
± ± ± ±
13 10 12 7
87 83 84 81
± ± ± ±
15 10 0 14
85 87 90 86
± ± ± ±
12 15 15 14
80 85 87 78
± ± ± ±
13 8 21 12
86 83 88 82
± ± ± ±
15 8 22 16
92 76 84 86
± ± ± ±
19 13 15 13
18 18 20 16
± ± ± ±
7B 15 17 5B
17 17 18 18
± ± ± ±
6B 9 10 8B
17 19 18 17
± ± ± ±
6B 9 9 8B
16 16 15 17
± ± ± ±
3B 4 5 8B
15 15 17 18
± ± ± ±
4B 6 3 8B
19 15 19 18
± ± ± ±
4AB 5 4 6B
18 16 17 16
± ± ± ±
5B 5 3 5B
18 17 16 17
± ± ± ±
5AB 6 3 4B
34 33 32 34
± ± ± ±
2B 7 8 2B
34 35 33 33
± ± ± ±
3B 4 4 3B
33 35 34 33
± ± ± ±
3B 3 4 2B
33 35 34 33
± ± ± ±
5B 2 3 3B
33 36 33 33
± ± ± ±
6B 2 3 2B
31 36 34 34
± ± ± ±
7B 2 3 2B
32 37 33 34
± ± ± ±
6B 2 3 2B
32 37 33 34
± ± ± ±
6B 3 3 2B
38.3 38.4 38.3 38.6
± ± ± ±
0.3B 0.3B 0.3B 0.5A
38.1 38.1 38.2 38.5
± ± ± ±
0.3B 0.3B 0.3B 0.4B
38.1 38.2 38.1 38.3
± ± ± ±
0.3B 0.2B 0.3B 0.4B
38.1 38.1 38.2 38.2
± ± ± ±
0.3B 0.2B 0.3B 0.3B
38.1 38.1 38.1 38.1
± ± ± ±
0.3B 0.3B 0.3B 0.3B
38.0 38.1 38.1 38.1
± ± ± ±
0.4B 0.3B 0.3B 0.3B
38.1 38.1 38.0 38.2
± ± ± ±
0.4B 0.4B 0.2B 0.3B
38.1 38.2 38.1 38.3
± ± ± ±
0.5B 0.3B 0.3AB 0.2B
Different superscript capital letters indicate differences over time in each treatment.
unilateral stimulation and control at 60 minutes on the right side. There were no statistical differences in plasma cortisol concentrations between the treatments (Fig. 5). Discussion In Traditional Chinese Medicine, ST36 is the master point for the abdomen and gastrointestinal tract, SP6 is the master point for the caudal abdomen and genitourinary region and GB34 is the influential point for tendons and ligaments. The points selected in this study have produced analgesia in several other studies (Rogers 1982). Stimulation at ST36 and SP6 or ST36 and GB34 produced sufficient analgesia for an abdominal incision and gentle manipulation of the viscera in 25% and 89% of bitches, respectively (Wright & Mcgrath 1981). Abdominal surgical analgesia in dogs (O’Boyle & Vajda 1975) and pronounced hind limb analgesia in rats (Oliveira & Prado 2000) were observed with 56
the use of ST36 and SP6 acupoints. In this study, the combination of ST36, SP6, and GB34 reduced the pain response to thermal and mechanical stimuli, confirming these previous reports. Bilateral EA increased the thermal and mechanical pain thresholds when compared with the false points and the untreated animals. Cutaneous pain threshold increased in horses and sheep treated with EA (Bossut et al. 1984,1986), suggesting that EA might stimulate the primary afferent fibers from muscle and cutaneous mechanical and thermal receptors (McIntyre 1974). Some studies (Christensen et al. 1982; Wang et al. 1991) suggest the classical ‘gate’ control theory as part of the mechanism of action (Melzac & Wall 1965). Acupuncture activates the large-diameter nerve fibers (A delta), modifying C fiber transmission of the noxious stimulus at the spinal cord, thereby reducing the sensation of pain (Kotani et al. 2001; White et al. 2001). There is evidence showing that EA stimulates the pain inhibitory system at the spinal cord,
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Electroacupuncture analgesia in dogs RN Cassu et al. pffiffiffiffiffiffiffiffiffiffiffiffiffi Table 2 Square root transformed means ( X þ 1) and standard deviation (SD) of the summed pain scores of the right, midline and left areas in a total of 12 pre umbilical and retro umbilical squares (possible maximum score ¼ 24), after thermal cutaneous stimuli and of the time in seconds until reaction after interdigital thermal stimulus in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
Minutes
0
30
60
Thermal cutaneous stimulus (score) T-false 4.5 ± 5 4.5 ± 7a T-EA/bil 4.5 ± 7A 2.5 ± 5bB T-EA/uni 4 ± 7A 3.5 ± 7abAB T-control 4 ± 10 3 ± 10ab Thermal right interdigital stimulus (latency in seconds) T-false 1.5 ± 0.5 2 ± 2b T-EA/bil 2 ± 2B 3 ± 3aA T-EA/uni 1.5 ± 1B 2 ± 3bAB T-control 2±4 2 ± 0.5b Thermal left interdigital stimulus (latency in seconds) T-false 1.5 ± 1 2 ± 3b 3 ± 2aA T-EA/bil 2 ± 2C T-EA/uni 1.5 ± 1B 2 ± 4bAB T-control 2±3 2 ± 1b
90
120
4 1.5 2 3
± ± ± ±
10a 6bB 8bB 9ab
4 2 2.5 4
± ± ± ±
9a 9bB 8abB 8a
4.5 3 3 4
± ± ± ±
6a 8bB 10bB 9ab
2 2.5 2.5 1.5
± ± ± ±
3ab 4aA 4aA 4b
1.5 3 2 2
± ± ± ±
1b 4aA 4bAB 3b
1.5 2.5 2 2
± ± ± ±
1b 4aAB 4abAB 1ab
2 3 2.5 2
± ± ± ±
3b 4aAB 4abA 2ab
2 2.6 2.5 2
± ± ± ±
3b 4aAB 4abAB 3ab
2 2.5 2 2
± ± ± ±
3 4BC 4AB 3
Different superscript capital letters indicate differences over time in each treatment; different superscript small letters indicate differences between treatments at each time.
Treatments T-false T-EA/bil T-EA/uni T-control Times(minutes) 0 30 60 90 120 F-test Treatment (A) Times (B) Interaction A · B
GPfalse GEA/bil GEA/uni Gcontrol
60 50 Cortisol (nmol.L–1)
pffiffiffiffiffiffiffiffiffiffiffiffiffi Table 3 Square root transformed means ( X þ 1) of the summed pain scores of the right, midline and left areas in a total of 12 pre umbilical and retro umbilical squares (possible maximum score ¼ 24), after mechanical cutaneous stimulus in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
40 30 20 10
4.0a 2.9b 3.4b 3.5ab 3.4ABC 3.2BC 2.9C 3.6AB 4.0A 4.7* 5.4** 1.7ns
ns: not significant (p > 0.05). Different superscript capital letters indicate differences over time; different superscript small letters indicate differences between treatments. *Significant (p < 0.05); **Significant (p < 0.01).
brainstem and other areas of the central nervous system, such as thalamus, 3rd ventricle, mesencephalon, diencephalon, hypothalamus, and hypo-
0 Before
After
Figure 5 Mean (SD) plasma cortisol concentration (nmol L)1) in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and untreated animals (T-control).
physis (Melzack 1976; Han et al. 1980; He 1987; Kho & Robertson 1997). Endogenous opioids, such as endorphins, enkephalins, and dynorphins have also been well documented to contribute to the analgesic effect of acupuncture (Pomeranz 1987; Hsu 1996). The dense-disperse mode of electrical stimulation, with the frequency ranging from 10 to 1000 Hz, used in this study probably produced the release of a combination of endogenous opioids. Low-frequency EA increases the release of enkephalin, b endorphin,
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Electroacupuncture analgesia in dogs RN Cassu et al.
and endomorphin 1 and 2 (Han 1993; Huang et al. 2000) and high-frequency EA releases dynorphin in the spinal cord (Han 1993). Chen & Han (1992) observed that the l and r, j and l, r and j opioid receptors were activated after EA using the frequencies of 2, 100, and 2–15 Hz, respectively. The analgesic effect observed after transcutaneous and percutaneous electrical stimulation was more pronounced after the use of mixed frequencies, when compared with low or high frequencies (Ghoname et al. 1999; Hamza et al. 1999), showing that a mixed frequency appears to be ideal to produce analgesia during EA. The analgesic effect produced by unilateral EA was intermediate between the bilateral and false acupoint stimulation. A previous study showed that both unilateral and bilateral auricular acupuncture produced similar analgesic effects (Still et al. 1985). In our study, bilateral EA produced better analgesia than unilateral EA, with a shorter time to effect, longer duration of effect, and greater intensity of analgesia. The prolonged duration of analgesia in the animals undergoing bilateral EA suggests an endocrine participation in this effect. Pomeranz (1978) showed that b endorphin and serotonin are involved in the humoral response mediated by EA, producing long-term analgesia in rats, even after interruption of the electrical stimulation of acupoints. Some studies have demonstrated increased serotonergic activity (Cheng & Pomeranz 1981; Cui et al. 1999) and plasma endorphin concentration in response to acupuncture (Liao et al. 1980; Nappi et al. 1982; Bossut et al. 1983), because of either the increased production or the reduced reuptake and/or elimination of these hormones. The thoracic and abdominal cutaneous analgesia was more pronounced than the analgesia at the interdigital space, as at some time points there was no response to pain at the thoracic and abdominal areas, whereas there was always a response after interdigital stimulation. This difference in somatatopic response might have been influenced by the points selected. The ST36 and SP6 are the master points for the abdominal region. In horses submitted to EA, there was no analgesia of the head or limbs using the points Ba Shan (BL53), Bai Hui (GV20), and Yao Pang or Ye Yan (PC6), San Yan Lu (TH8), and Qiang Feng (TH13) (Bossut et al. 1983). However, analgesia was observed in both fore and hind limbs in sheep undergoing EA at Yao Pang, Bai Hui, San Yang Lui, and Qiang Feng (Bossut et al. 58
1986). In a similar study, EA at the acupoints ST36 and SP6 produced analgesia in the hind limbs of rats (Oliveira & Prado 2000). These differences may be produced by the pain inhibitory system activated in each situation (Bossut et al. 1983). Watkins et al. (1982) reported that different pain modulation systems are activated in pelvic and thoracic limbs in rats. Analgesia of the thoracic limbs, but not in the pelvic limbs, was reversed by naloxone administration, showing that the endogenous opioids do not take part in the pain suppression response in pelvic limbs. In the present study, pain stimulation was performed in the thoracic limb as it is a general consensus that acupuncture-induced analgesia is partially mediated by endogenous opioids. Practically, it was recognized that the animal’s reaction to the stimulus might remove the needles inserted into the hind limbs if the pelvic limb had been used for the noxious stimulus. The sedation with acepromazine was necessary in order to avoid undesirable reactions as a result of manipulation, restraint, recumbency, monitoring, insertion of needles, and electrical stimulus for a long period. In sick animals, the use of acupuncture is well tolerated, and this difference may produce conflicting results when clinical and experimental studies are compared (Wright & Mcgrath 1981). Acepromazine might have compromised the results, as it depresses the CNS and cardiovascular system, modifying the responses against noxious stimuli. Low doses of acepromazine (0.05 mg kg)1) produce sedation for 1–2 hours (Brock 1994). Acepromazine might also potentiate the EA-induced analgesia (Rogers 1982). This study showed a difference between true EA and false EA, but the magnitude of the effect of acepromazine cannot be determined as it was administered to all dogs for all treatments. The stimulation of false points, even with restraint and electrical stimulation did not increase the pain threshold, as previously reported in rats (Oliveira & Prado 2000) and in dogs (Still et al. 1986), showing that EA and not stress, was responsible for the analgesia. Further confirmation of the above statement is provided by the lack of change in plasma cortisol concentrations in any treatment, as reported previously (Pellegrin et al. 1980; Masala et al. 1983; Pullan et al. 1983; Umino et al. 1984; Luna & Taylor 1998). Electroacupuncture at real points was more successful in producing analgesia than at false EA points. Other studies in rabbits (Takeshige 1985), cats (Dorman & Gage 1978), rats (Toda et al. 1980;
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Electroacupuncture analgesia in dogs RN Cassu et al.
Iriki 1982), and humans (Pomeranz 1987; Kho & Robertson 1997) also reported that acupuncture at real points produced more analgesia than at false points. False points produced analgesia in only 3% of the animals submitted to acute pain models (Pomeranz 1987). On the contrary, false points can produce analgesia in 30–35% of human chronic pain patients (Pomeranz 1987). It seems that stimulation of any point in the body may increase pain threshold. However, a better effect is achieved when real acupoints are used or when the points stimulated are from the same area of innervation as the acupoints (Kho & Robertson 1997). In this study, the needles of the false points were inserted at the same dermatome, using the same kind of electrical stimulation according to Gaw et al. (1975) and Fung & Chow Okw (1986), respectively, to simulate, as closely as possible, the technique used for the real acupuncture treatment. Accordingly, a possible dermatome effect and stimulation technique can be discounted by our results. Previous reports showed that stimulation of the muscle fibers produce muscle action potentials and participate in the acupuncture effect (Kendall 1989). This effect is produced by the intrafusal muscle tissue and gamma 2 type motor fibers, remaining even when the nervous and vascular supply are interrupted (Kendall 1989). The intensity of the muscle action potential is dependent on the quantity, presence and distribution of intrafusal muscle fibers in specific acupoints (Yan et al. 1984). One of the reasons for selection of the ST36 acupoint in this study was that it produces a much higher muscle action potential when compared with other acupoints (Yan et al. 1984). The use of EA alone to produce surgical anesthesia does not seem to be very ethical, as it is not effective in 100% of the cases. However, considering the absence of side effects and the low cost, EA could be used as a complement to other analgesic techniques to reduce the amount of anesthetics and analgesics used perioperatively (Janssens et al. 1988; Wynn et al. 2000). Cardiorespiratory variables were not affected by EA. Similar studies of EA in dogs (Wright & Mcgrath 1981) and sheep (Bossut et al. 1986) showed no cardiorespiratory effects either. The decrease in rectal temperature in all treatments was probably produced by the vasodilatory effect of acepromazine; however, this finding was not clinically significant, as temperature was always above 38.0 C.
The calm behavior observed in most of the dogs in this study is a typical finding of EA in several species and might be related to the release of endogenous opioids (Bossut et al. 1986; Luna & Taylor 1998). The absence of cardiorespiratory and behavioral changes typical of stress during EA shows that it is unlikely that EA-induced analgesia is produced by stress (Bossut et al. 1986). Acupuncture might reduce stress (Lin & Rogers 1980), as plasma cortisol concentration was reduced in stressed rabbits after acupuncture (Liao et al. 1980) and the parasympathomimetic effect of ST36 has been useful to treat hypertension in humans (Tam & Yiu 1975) and rats (Lee 1974). In conclusion, bilateral EA produced a shorter latency period, a greater intensity, and longer duration of analgesia, than unilateral stimulation, without a stress response. According to these results, bilateral EA should be used instead of unilateral EA, because of the better analgesic effect produced by the bilateral EA. References Banzatto DA, Kronka SN (1995) Experimentac¸a˜o agrı´cola. (3rd edn), Funep, Jaboticabal. p. 247. Barbieri O, Bellone G, Manfredi C et al. (1979) Acupuncture analgesia in eye surgery. Minerva Med 70, 3853–3856. Bossut DFB, Leshin LS, Stromberg MW et al. (1983) Plasma cortisol and beta-endorphin in horses subjected to electro-acupuncture for cutaneous analgesia. Peptides 4, 501–507. Bossut DFB, Page EH, Stromberg MW (1984) Production of cutaneous analgesia by EA in horses: variations dependent on sex of subject and locus of stimulation. Am J Vet Res 45, 620–625. Bossut DFB, Stromberg MW, Malven PV (1986) EA-induced analgesia in sheep: measurement of cutaneous pain thresholds and plasma concentrations of prolactin and b-endorphin immunoreactivity. Am J Vet Res 47, 669–676. Brock N (1994) Acepromazine revisited. Can Vet J 35, 458–459. Caracausi SR (1979) Electro-acupuncture in thoracic and cardiovascular surgery. Minerva Med 70, 3857–3860. Chen XH, Han JS (1992) Analgesia induced by EA of different frequencies is mediated by different types of opioid receptors: another cross-tolerance study. Behav Brain Res 47, 143–149. Cheng RSS, Pomeranz B (1981) Monoaminergic mechanisms of EA analgesia. Brain Res 29, 77–92. Cheng R, Mckibbin L, Roy B et al. (1980) Electroacupuncture elevates blood cortisol levels in naive horses: sham treatment has no effect. Int J Neurosci 10, 95–97.
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Christensen P, Brandt MR, Rem J (1982) Influence of extradural morphine on the adrenocortical and hyperglycemic response to surgery. Br J Anaesth 54, 23–27. Cui M, Feng Y, Mcadoo DJ et al. (1999) Periaqueductal gray stimulation-induced inhibition of nociceptive dorsal horn neurons in rats is associated with the release of norepinephrine, serotonin, and amino acids. J Pharmacol Exp Ther 289, 868–879. Dorman HL, Gage TW (1978) Effects of EA on the threshold for eliciting the jaw depressor reflex in cats. Arch Oral Biol 23, 505–506. Fung KP, Chow Okw SOS (1986) Attenuation of exerciseinduced asthma by acupuncture. Lancet 2, 1419– 1422. Gaw AC, Chang LW, Shaw LC (1975) Efficacy of acupuncture on osteoarthritic pain: a controlled, double blind study. N Engl J Med 293, 375–378. Ghoname EA, Craig WF, White PF et al. (1999) The effect of stimulus frequency on the analgesic response to percutaneous electrical nerve stimulation in patients with chronic low back pain. Anesth Analg 88, 841– 846. Hamza MA, Ghoname EA, White PF (1999) Effect of the duration of electrical stimulation on the analgesic response in patients with low back pain. Anesthesiology 91, 1622–1627. Han JS (1993) Acupuncture and stimulation produced analgesia. In: Handbook of Experimental Pharmacology. Herz A (eds). Springer, Berlin, Germany. pp. 105–125. Han JS, Tang J, Ren MF et al. (1980) Central neurotransmitters and acupuncture analgesia. Am J Chin Med 8, 331–348. He L (1987) Involvement of endogenous opioid peptides in acupuncture analgesia. Pain 31, 99–121. Hsu DT (1996) Acupuncture: a review. Reg Anesth 21, 361–370. Huang C, Wang Y, Chang JK et al. (2000) Endomorphin and l-opioid receptors in mouse brain mediate the analgesic effect induced by 2 Hz but not 100 Hz electroacupuncture stimulation. Neurosci Lett 294, 159– 162. Iriki A (1982) Site and action of electroacupuncture induced effects on the jaw opening reflex. Exp Neurol 75, 36–50. Janssens LAA, Rogers PAM, Schoen AM (1988) Acupuncture analgesia: a review. Vet Rec 122, 355–358. Kendall OMD (1989) A scientific model for acupuncture. Am J Acupunct 17, 251–268. Kho HG, Robertson EN (1997) The mechanisms of acupuncture analgesia: review and update. Am J Acupunct 25, 261–281. Kotani N, Hashimoto H, Yuataka S et al. (2001) Preoperative intradermal acupuncture reduces postoperative pain, nausea and vomiting, analgesic requirement, and sympathoadrenal responses. Anesthesiology 95, 349– 356.
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Kothbauer O (1975) Electroacupuncture analgesia in caesarean section in cows. Wien Tierarztl Monatsschr 62, 394–396. Lee GTC (1974) A study of electrical stimulation of acupuncture locus tsusanli (St-36) on mesenteric microcirculation. Am J Chin Med 2, 53–66. Lee SC, Yin SJ, Lee ML (1982) Effects of acupuncture on serum cortisol level and dopamine beta-hydroxylase activity in normal Chinese. Am J Chin Med 9, 62–69. Liao YY, Seto K, Saito H (1980) Effects of acupuncture on adrenocortical hormone production. II Effect of acupuncture on the response of adrenocortical hormone production to stress. Am J Chin Med 8, 160–166. Lin JH, Rogers PAM (1980) Acupuncture effects on the body defense systems: a veterinary review. Vet Bull 50, 633–639. Luna SPL, Taylor PM (1998) Effect of EA on endogenous opioids, AVP, ACTH, cortisol and catecholamine concentrations. Proceedings of the 24th International Congress on Veterinary Acupuncture, Taipei, Taiwan. pp. 172–174. Masala A, Satta G, Alagna S (1983) Suppression of electroacupuncture (EA) induced beta-endorphin and ACTH release by hydrocortisone in man. Acta Endocrinol 103, 469–472. McIntyre AK (1974) Central action of impulses in muscle afferents fibres. In: Muscle Receptors. Barker D, Hung CC, McIntyre AK (eds). Berlin-Heidelberg, New York. pp. 262–266. Melzac R, Wall PD (1965) Pain mechanisms. A new theory. Science 150, 971–979. Melzack R (1976) Acupuncture and pain mechanisms. Anaesthesist 25, 204–207. Nappi G, Facchinetti F, Legnante G (1982) Different releasing effects of traditional manual acupuncture and EA on proopiocortin-related peptides. Acupunct Electrother Res 7, 93–103. O’Boyle MA, Vajda GK (1975) Acupuncture anesthesia for abdominal surgery. Mod Vet Pract 56, 705–707. Oliveira R, Prado WA (2000) Anti-hyperalgesic effect of electroacupuncture in a model of post-incision. Braz J Med Biol Res 33, 957–960. Pellegrin D, Mion H, Bossy J (1980) Modification of ACTH and cortisol secretion through the stimulation of taichong: preliminary study. Acupunct Electrother Res 5, 171–179. Pomeranz B (1978) Do endorphins mediate acupuncture analgesia? Adv Biochem Psychopharmacol 18, 351–359. Pomeranz B (1987) Scientific bases of acupuncture. In: Acupuncture Textbook and Atlas. Stux G, Pomeranz B (eds). Springer Verlag, Berlin/Heidelberg, Germany. pp. 20–26. Pullan PT, Finch PM, Yuen RWM et al. (1983) Endogenous opiates modify release of growth hormone in response to electroacupuncture. Life Sci 32, 1705– 1709.
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Roccia L, Franco I (1977) Surgical analgesia by acupuncture. Studies of more than 500 cases. Minerva Med 68, 703–710. Rogers PAM (1982) Acupuncture analgesia for surgery in animals. Proceedings of the Belgium Acupuncture Society Seminar, Antwerpen, Belgium. pp 1–22. Stellpflug H, Wickings EJ, Nieschlag E (1978) Operative stress during electroacupuncture and enflurane anaesthesia assessed by serum cortisol. Prakt Anaesth 13, 483–488. Still J (1987) Acupuncture analgesia for laparotomy in dogs and cats: an experimental study. Am J Acupunct 15, 155–165. Still J, Konrad J, Saidova Z et al. (1985) Acupuncture auricular analgesia in the dog and cat using VESA instrument. Proceedings of the II International Congress on Acupuncture, Prague, Czechoslovakia. p. 51 (abstract). Still J, Still V, Merta J et al. (1986) Experimental ear acupuncture analgesia in the dog. Vlaams Diergeneesk Tijdschr 55, 407–415. Takeshige C (1985) Differentiation between acupuncture and non-acupuncture points by association with an analgesia inhibitory system. Acupunct Electrother Res 10, 195–203. Tam KC, Yiu HH (1975) The effect of acupuncture on essential hypertension. Am J Chin Med 3, 369–375. Toda K, Suda H, Ichioka M et al. (1980) Local electrical stimulation: effective needling points for suppressing jaw opening reflex in rat. Pain 9, 99–107. Umino M, Shimada M, Kubota Y (1984) Effects of acupuncture anesthesia on the pituitary gland. Bull Tokyo Med Dent Univ 31, 93–98.
Vierck CJ, Lineberry CG, Lee PK et al. (1974) Prolonged hypalgesia following acupuncture in monkeys. Life Sci 15, 1277–1289. Wang Y, Wang S, Zhang W (1991) Effects of naloxone on the changes of pain threshold and contents of monoamine neurotransmitters in rat brain induced by electroacupuncture. J Tradit Chin Med 11, 286–290. Watkins LR, Cobelli DA, Faris P et al. (1982) Opiate vs non-opiate footshock-induced analgesia (FSIA): the body region shocked is a critical factor. Brain Res 242, 299– 308. White PF, Li S, Chiu JW (2001) Electroanalgesia: its role in acute and chronic pain management. Anesth Analg 92, 505–513. Wright M, Mcgrath CJ (1981) Physiologic and analgesic effects of acupuncture in the dog. J Am Vet Med Assoc 178, 502–507. Wynn SG, Luna SPL, Liu H et al. (2000) Global acupuncture research: previously untranslated studies. Studies from Brazil. In: Veterinary Acupuncture (2nd edn). Schoen AM (ed.), Mosby, St Louis, USA. pp. 53– 72. Yan JQ, Wang KM, Hou ZL (1984) The nature of acupoint muscle action potential (AMAP) and influence of temperature on it. Proceedings of the 2nd National Symposium on Acupuncture and Moxibustion, Beijing, China. pp. 533–534. Zaslavskii SIA, Asnes SV, Tolchinskii VV (1977) Tonsillectomy with electro acupuncture analgesia. Zh Ushn Nos Gorl Bolezn 3, 35–38. Received 6 February 2005; accepted 7 July 2006.
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doi:10.1111/j.1467-2995.2007.00347.x
RESEARCH PAPER
Electroacupuncture analgesia in dogs: is there a difference between uni- and bi-lateral stimulation? Renata N Cassu* DVM, PhD, Stelio PL Luna* Se´rgio N Kronka MSc, PhD
DVM, PhD, Diplomate ECVA,
Rosana MO Clark*
DVM, PhD
&
*Department of Veterinary Surgery and Anaesthesiology, Faculty of Veterinary Medicine and Animal Science, FMVZ, Unesp, Botucatu, SP, Brazil Department of Statistics, Bioscience Institute, Unoeste, Presidente Prudente, SP, Brazil
Correspondence: Stelio Luna, Department of Veterinary Surgery and Anaesthesiology, School of Veterinary Medicine and Animal Science, FMVZ, Unesp, 18618-000 Botucatu, SP, Brazil. E-mail: [email protected]
Abstract Objective To compare the analgesic effect of uniand bi-lateral electroacupuncture (EA) in response to thermal and mechanical nociceptive stimuli and to investigate the cardiorespiratory, endocrine, and behavioral changes in dogs submitted to EA. Study design Prospective, randomized cross-over experimental study. Animals Eight adult, clinically healthy, cross-breed dogs, weighing 13 ± 4 kg. Methods Dogs underwent electrostimulation at false acupoints (T-false); bilateral EA at acupoints, stomach 36, gall bladder 34 and spleen 6 (T-EA/bil); unilateral EA at the same points (T-EA/uni) or were untreated (T-control). All animals received acepromazine (0.05 mg kg)1) IV; and heart rate, pulse oximetry, indirect arterial blood pressure, respiratory rate, PE¢CO2, rectal temperature, and plasma cortisol concentration were measured before, during, and after EA. Analgesia was tested using thoracic and abdominal cutaneous thermal and mechanical stimuli, and an interdigital thermal stimulus. Behavior was classified as calm or restless. Analysis of variance for repeated measures followed by Tukey’s test was used for analysis of the data. 52
Results There were no cardiorespiratory differences among the treatments. The cutaneous pain threshold was higher after EA, compared with false points. The latency period was shorter and analgesia was more intense in T-EA/bil than T-EA/uni, when both were compared with T-false and T-control. Six out of eight animals treated with EA were calm during treatment, and 5/8 and 4/8 of the T-false and T-control animals, respectively, were restless. Latency to interdigital thermal stimulation increased in T-EA/bil compared with the others. There was no difference in plasma cortisol concentrations among the treatments. Conclusions Bilateral EA produced a shorter latency period, a greater intensity, and longer duration of analgesia than unilateral stimulation, without stimulating a stress response. Clinical relevance Bilateral EA produces a better analgesic effect than unilateral EA. Keywords bilateral, dog, electroacupuncture, unilateral.
Introduction Acupuncture is among the many treatment options for pain in clinical veterinary practice. The advantages of acupuncture are that it is practical, safe,
Electroacupuncture analgesia in dogs RN Cassu et al.
less expensive, and with fewer side effects when compared with conventional pharmaceutical management of pain. The disadvantages are that a specific knowledge of the subject is necessary and that the response among individuals may vary. The first surgical procedures using electroacupuncture (EA) were reported in the early 1970s in humans and animals (Vierck et al. 1974; Kothbauer 1975; Roccia & Franco 1977; Zaslavskii et al. 1977; Barbieri et al. 1979; Caracausi 1979). Electroacupuncture is also indicated for the treatment of chronic diseases, peripheral and central nervous system disturbances, and acute and chronic pain (Wynn et al. 2000). A few reports suggest that the analgesia induced by acupuncture is caused by stress because increased plasma cortisol and ACTH concentrations may be observed after EA (Stellpflug et al. 1978; Cheng et al. 1980; Lee et al. 1982; Bossut et al. 1983). However, other studies have dismissed these findings, as analgesia is observed regardless of the presence of a stress response (Pellegrin et al. 1980; Masala et al. 1983; Pullan et al. 1983; Luna & Taylor 1998). Bilateral acupuncture is usually recommended for general clinical purposes, including pain relief (Dorman & Gage 1978; Wright & Mcgrath 1981). However, unilateral stimulation may be an alternative to simplify the technique (Still 1987), as the animals might be maintained in lateral recumbency during treatment and the technique would be less time consuming, as the number of needles would be reduced by half. The aim of this study was to compare the analgesic effects of uni- and bi-lateral EA in response to thermal and mechanical nociceptive stimuli, as well as to investigate the cardiorespiratory, endocrine, and behavioral changes in dogs submitted to EA.
(n ¼ 8) – EA at false acupoints close to real points in the right hind limb; T-EA/bil (n ¼ 8) – EA at stomach 36 (ST36), gall bladder 34 (GB34), and spleen 6 (SP6) acupoints, bilaterally; T-EA/uni (n ¼ 8) – as for T-EA/bil but unilaterally in the right hind limb (Fig. 2). The Tsu-san-li (ST36) acupoint is located 3 cun (1 cun ¼ width of the last rib) distal to the lateral head of the fibula. The acupoint Yangling-chuan (GB34) is located at the proximal end of the interosseous space between the tibia and fibula and the acupoint San-yin-chiao (SP6) is located 3 cun proximal to the medial malleolus, at the caudal border of the tibia, close to the medial saphenous vein (Fig. 2). The false points were selected in areas close to the real points, making sure that they were not points of other principal meridians. According to that, the false ST36, GB34, and SP6 points were located in the longus digital extensor and deep digital flexor muscles, and caudal border of the calcanean (Achilles) tendon, respectively (Fig. 3). All animals were maintained in left lateral recumbency. Except for the untreated animals (control), the 30 · 0.25 mm needles (Suzhou Huanqiu Acupuncture Medical Appliance, Beijing, China) were introduced in the above points and the electrodes were attached to the body of the needles.
Materials and methods This study was approved by the Animal Research Ethical Committee, under protocol number 43/ 2002. Seven females and one male clinically healthy cross-breed dogs, weighing 13 ± 4 kg were sedated with 0.05 mg kg)1 of acepromazine IV. The region from the manubrium to the pubis was shaved and divided bilaterally into 12 squares of 25 cm2 each (Fig. 1). Thirty minutes after sedation, each animal underwent four different protocols at weekly intervals, using a random order of treatments: T-control (n ¼ 8) – no treatment; T-false
Figure 1 Diagram showing the thoracic and abdominal ‘squares’ used to investigate cutaneous analgesia: 1, 2, 3, 4, 5, and 6 (pre-umbilical), 7, 8, 9, 10, 11, and 12 (retroumbilical), 1, 4, 7, and 10 (right side), 2, 5, 8, and 11(midline), 3, 6, 9, and 12 (left side).
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GB 34 ST 36
SP 6
Figure 3 Location of false points. From: Acupuncture points and meridians in the dog, Janssens & Still, Stittsville, Ontario, Canada, 1995.
Figure 2 Location of ST36, GB34, and SP6 acupoints. From: Acupuncture points and meridians in the dog, Janssens & Still, Stittsville, Ontario, Canada, 1995.
twitching. After that, the electrical current intensity was reduced until the animals were comfortable again, but still maintaining local muscle contraction. Electrostimulation was performed for 60 minutes. The mechanical and thermal nociceptive responses were investigated at 30 and 60 minutes after beginning the electrical stimulation, and 30 and 60 minutes after the end of electrical stimulation. The experimental sequence is described in Fig. 4. The following measurements were performed: heart rate, ECG; pulse oximetry (with the sensor on the vulva or prepuce); respiratory rate and capnography (with the sampling collecting tube in the nostrils); rectal temperature (Datex Engstrom,
An alternating square wave dense/disperse 0.2 ms (10–1000 Hz) continuous electrical stimulus was used (Electronic Acupuncture WQ-6F, Beijing, China). For T-EA/uni, the same electrical source of stimulation was used for the points GB34 and SP6 and another source was used for ST36, with the second electrode placed on the skin pleat caudal to the achilles tendon. For T-EA/bil, the same electrical source of stimulation was used for GB34 and SP6 on one side, another source for the other side, and another source was used for bilateral stimulation of ST36 acupoints. The EA equipment was turned on and the intensity of the electrical current stimulation started from zero and increased slowly until the animals showed signs of discomfort and presence of
Electroacupuncture or untreated (control)
–30
IV ACP
–15
0
15
30
45
60
75
90
105
CR Cortisol pain
CR
CR pain
CR
CR Cortisol pain
CR
CR pain
CR
120
CR pain
Figure 4 Experimental sequence of EA, blood sampling, cardiorespiratory measurements, and pain scoring in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/unil) and untreated dogs (T-control). IV ACP: IV administration of acepromazine, cortisol: blood sampling for cortisol measurement, CR: cardiorespiratory measurements, pain thermal and mechanical stimuli applied and response evaluated. 54
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Ohmeda Division, Finland); indirect arterial blood pressure, (with the width cuff about 40% of the circumference of the antebrachium) (Dixtal DX 2710; Biomedica, Manaus, Brazil); and plasma cortisol concentration, using a solid phase radioimmunoassay (Coat-A-Count Cortisol – DPC, USA). Somatic analgesia was evaluated using the thermal (Thermoalgimeter, Iope Precision Instruments, Sa˜o Paulo, Brazil) and mechanical nociceptive stimuli, applied to the thoracic and abdominal regions (Fig. 1). The thermal stimulus was applied using a blunt probe at 52 C and the mechanical stimulus was applied using forceps protected with rubber, squeezed until the animal reacted or until the first ratchet of the forceps had been reached. The thermal and mechanical stimuli were applied until the animal reacted or for up to a maximum of 10 seconds. The following score was used: 0 ¼ no response (animals remained in sternal or lateral recumbency, with no response), 1 ¼ reduced response (slight reaction after stimulation, raising the head and looking at the area of stimulation, without vocalization), 2 ¼ normal response (quick and strong reaction against stimulation, trying to bite the metal probe or the forceps, with vocalization). The response was observed in each square and the scores were summed from the left, right, and midline areas in a total of 12 squares, rostral and caudal to the umbilicus. The possible maximum score was 24, with a normal response obtained in all measurements (Fig. 1). The thermal stimulus was also applied to the interdigital space of the fore limbs for a maximum of 10 seconds, measuring the time in seconds until a withdrawal response. Behavior was observed and considered as calm/ sedated, when animals were asleep and cooperative, or restlessness for the animals that were impatient and restless during the experimental procedure. The pain and behavior scores were assessed by an individual who had not inserted the needles. Statistical analysis was performed using analysis of variance with the F test followed by Tukey’s test using Graphpad software (San Diego, CA, USA), to investigate differences between treatments at each time, differences in time for each treatment, and interaction between treatment and time. A p-value less than 0.05 was considered significant. When the factors treatment and time were dependent, interaction was further investigated to study 1) effects of time for each treatment and 2) effects of treatments at each time (Table 2). When interaction between treatment and time was not observed (p > 0.05),
these two factors (treatment and time) were independent, according to that, 1) the mean of each treatment was calculated considering all times and 2) the mean of each time was calculated considering all treatments (Table 3). A chi-square test with Yates correction was used to compare the differences in behavior (Banzatto & Kronka 1995). Results There were no differences between the treatments for the cardiorespiratory variables (Table 1) and the values were within the normal range for dogs. Temperature decreased over time in all treatments. The number of sedated animals in T-EA/bi and T-EA/uni was significantly greater than in T-false. There was no difference between the control treatment and the others. Seventy-five percent of the animals were calm during and after bilateral and unilateral EA. On the contrary, 5/8 T-false and 4/8 T-control animals were agitated and responded intensely to the nociceptive stimuli. Bilateral EA reduced the response to thermal cutaneous stimulation at 30–120 minutes when compared with the baseline values. Unilateral EA reduced the response to thermal cutaneous stimulation, at 60–120 minutes when compared with the baseline values but did not change responses to mechanical stimulation. Bilateral EA reduced the response to cutaneous thermal stimulation when compared with false EA and control animals from 30 to 120 minutes and at 90 minutes, respectively (Table 2). Unilateral EA reduced the response to cutaneous thermal pain stimulus only when compared with false EA at 60 and 120 minutes after the beginning of EA. Both bilateral and unilateral EA reduced the response to the cutaneous mechanical pain stimulus when compared with the false treatment. The control treatment values were intermediate (Table 3). The time to response after the left and right interdigital thermal stimulus was longer 30 minutes after the beginning of EA in the bilateral treatment, when compared with the other treatments (Table 2). The latency was also increased over the false group on the left at 30, 60, and 90 minutes and on the right at 90 and 120 minutes. The interdigital stimulus was different between the control and the bilateral stimulation at 30 minutes, but the difference was only statistically significant for the right side at 60 and 90 minutes. There was a statistically significant difference between the
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Table 1 Mean (SD) heart rate (HR), mean arterial blood pressure (MAP), respiratory rate (RR), end tidal CO2 (PE¢CO2), and rectal temperature (C) in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
Minutes
0
15
HR (beats minute)1) T-false 98 ± 24 T-EA/bil 96 ± 22 T-EA/uni 94 ± 15 T-control 91 ± 17 MAP (mmHg) T-false 86 ± 16 T-EA/bil 87 ± 21 T-EA/uni 83 ± 16 T-control 86 ± 17 RR (breaths minute)1) T-false 30 ± 19A T-EA/bil 21 ± 11 T-EA/uni 22 ± 10 T-control 27 ± 12A PE¢CO2 (mmHg) T-false 29 ± 10A T-EA/bil 34 ± 6 T-EA/uni 30 ± 5 T-control 29 ± 5A Temperature (C) T-false 38.7 ± 0.5A T-EA/bil 38.9 ± 0.5A T-EA/uni 38.8 ± 0.3A T-control 38.9 ± 0.5A
30
45
60
75
90
105
120
90 81 89 83
± ± ± ±
10 12 110 21
101 85 88 83
± ± ± ±
25 20 17 18
88 84 96 88
± ± ± ±
19 16 18 23
85 90 87 81
± ± ± ±
21 30 19 17
93 101 84 91
± ± ± ±
23 31 11 20
85 84 84 88
± ± ± ±
21 15 16 25
82 84 87 80
± ± ± ±
16 15 14 26
83 94 85 77
± ± ± ±
20 17 20 19
89 77 83 83
± ± ± ±
13 24 16 18
84 82 89 82
± ± ± ±
9 20 13 11
86 87 87 79
± ± ± ±
13 10 12 7
87 83 84 81
± ± ± ±
15 10 0 14
85 87 90 86
± ± ± ±
12 15 15 14
80 85 87 78
± ± ± ±
13 8 21 12
86 83 88 82
± ± ± ±
15 8 22 16
92 76 84 86
± ± ± ±
19 13 15 13
18 18 20 16
± ± ± ±
7B 15 17 5B
17 17 18 18
± ± ± ±
6B 9 10 8B
17 19 18 17
± ± ± ±
6B 9 9 8B
16 16 15 17
± ± ± ±
3B 4 5 8B
15 15 17 18
± ± ± ±
4B 6 3 8B
19 15 19 18
± ± ± ±
4AB 5 4 6B
18 16 17 16
± ± ± ±
5B 5 3 5B
18 17 16 17
± ± ± ±
5AB 6 3 4B
34 33 32 34
± ± ± ±
2B 7 8 2B
34 35 33 33
± ± ± ±
3B 4 4 3B
33 35 34 33
± ± ± ±
3B 3 4 2B
33 35 34 33
± ± ± ±
5B 2 3 3B
33 36 33 33
± ± ± ±
6B 2 3 2B
31 36 34 34
± ± ± ±
7B 2 3 2B
32 37 33 34
± ± ± ±
6B 2 3 2B
32 37 33 34
± ± ± ±
6B 3 3 2B
38.3 38.4 38.3 38.6
± ± ± ±
0.3B 0.3B 0.3B 0.5A
38.1 38.1 38.2 38.5
± ± ± ±
0.3B 0.3B 0.3B 0.4B
38.1 38.2 38.1 38.3
± ± ± ±
0.3B 0.2B 0.3B 0.4B
38.1 38.1 38.2 38.2
± ± ± ±
0.3B 0.2B 0.3B 0.3B
38.1 38.1 38.1 38.1
± ± ± ±
0.3B 0.3B 0.3B 0.3B
38.0 38.1 38.1 38.1
± ± ± ±
0.4B 0.3B 0.3B 0.3B
38.1 38.1 38.0 38.2
± ± ± ±
0.4B 0.4B 0.2B 0.3B
38.1 38.2 38.1 38.3
± ± ± ±
0.5B 0.3B 0.3AB 0.2B
Different superscript capital letters indicate differences over time in each treatment.
unilateral stimulation and control at 60 minutes on the right side. There were no statistical differences in plasma cortisol concentrations between the treatments (Fig. 5). Discussion In Traditional Chinese Medicine, ST36 is the master point for the abdomen and gastrointestinal tract, SP6 is the master point for the caudal abdomen and genitourinary region and GB34 is the influential point for tendons and ligaments. The points selected in this study have produced analgesia in several other studies (Rogers 1982). Stimulation at ST36 and SP6 or ST36 and GB34 produced sufficient analgesia for an abdominal incision and gentle manipulation of the viscera in 25% and 89% of bitches, respectively (Wright & Mcgrath 1981). Abdominal surgical analgesia in dogs (O’Boyle & Vajda 1975) and pronounced hind limb analgesia in rats (Oliveira & Prado 2000) were observed with 56
the use of ST36 and SP6 acupoints. In this study, the combination of ST36, SP6, and GB34 reduced the pain response to thermal and mechanical stimuli, confirming these previous reports. Bilateral EA increased the thermal and mechanical pain thresholds when compared with the false points and the untreated animals. Cutaneous pain threshold increased in horses and sheep treated with EA (Bossut et al. 1984,1986), suggesting that EA might stimulate the primary afferent fibers from muscle and cutaneous mechanical and thermal receptors (McIntyre 1974). Some studies (Christensen et al. 1982; Wang et al. 1991) suggest the classical ‘gate’ control theory as part of the mechanism of action (Melzac & Wall 1965). Acupuncture activates the large-diameter nerve fibers (A delta), modifying C fiber transmission of the noxious stimulus at the spinal cord, thereby reducing the sensation of pain (Kotani et al. 2001; White et al. 2001). There is evidence showing that EA stimulates the pain inhibitory system at the spinal cord,
2007 The Authors. Journal compilation 2007 Association of Veterinary Anaesthetists, 35, 52–61
Electroacupuncture analgesia in dogs RN Cassu et al. pffiffiffiffiffiffiffiffiffiffiffiffiffi Table 2 Square root transformed means ( X þ 1) and standard deviation (SD) of the summed pain scores of the right, midline and left areas in a total of 12 pre umbilical and retro umbilical squares (possible maximum score ¼ 24), after thermal cutaneous stimuli and of the time in seconds until reaction after interdigital thermal stimulus in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
Minutes
0
30
60
Thermal cutaneous stimulus (score) T-false 4.5 ± 5 4.5 ± 7a T-EA/bil 4.5 ± 7A 2.5 ± 5bB T-EA/uni 4 ± 7A 3.5 ± 7abAB T-control 4 ± 10 3 ± 10ab Thermal right interdigital stimulus (latency in seconds) T-false 1.5 ± 0.5 2 ± 2b T-EA/bil 2 ± 2B 3 ± 3aA T-EA/uni 1.5 ± 1B 2 ± 3bAB T-control 2±4 2 ± 0.5b Thermal left interdigital stimulus (latency in seconds) T-false 1.5 ± 1 2 ± 3b 3 ± 2aA T-EA/bil 2 ± 2C T-EA/uni 1.5 ± 1B 2 ± 4bAB T-control 2±3 2 ± 1b
90
120
4 1.5 2 3
± ± ± ±
10a 6bB 8bB 9ab
4 2 2.5 4
± ± ± ±
9a 9bB 8abB 8a
4.5 3 3 4
± ± ± ±
6a 8bB 10bB 9ab
2 2.5 2.5 1.5
± ± ± ±
3ab 4aA 4aA 4b
1.5 3 2 2
± ± ± ±
1b 4aA 4bAB 3b
1.5 2.5 2 2
± ± ± ±
1b 4aAB 4abAB 1ab
2 3 2.5 2
± ± ± ±
3b 4aAB 4abA 2ab
2 2.6 2.5 2
± ± ± ±
3b 4aAB 4abAB 3ab
2 2.5 2 2
± ± ± ±
3 4BC 4AB 3
Different superscript capital letters indicate differences over time in each treatment; different superscript small letters indicate differences between treatments at each time.
Treatments T-false T-EA/bil T-EA/uni T-control Times(minutes) 0 30 60 90 120 F-test Treatment (A) Times (B) Interaction A · B
GPfalse GEA/bil GEA/uni Gcontrol
60 50 Cortisol (nmol.L–1)
pffiffiffiffiffiffiffiffiffiffiffiffiffi Table 3 Square root transformed means ( X þ 1) of the summed pain scores of the right, midline and left areas in a total of 12 pre umbilical and retro umbilical squares (possible maximum score ¼ 24), after mechanical cutaneous stimulus in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and no treatment (T-control)
40 30 20 10
4.0a 2.9b 3.4b 3.5ab 3.4ABC 3.2BC 2.9C 3.6AB 4.0A 4.7* 5.4** 1.7ns
ns: not significant (p > 0.05). Different superscript capital letters indicate differences over time; different superscript small letters indicate differences between treatments. *Significant (p < 0.05); **Significant (p < 0.01).
brainstem and other areas of the central nervous system, such as thalamus, 3rd ventricle, mesencephalon, diencephalon, hypothalamus, and hypo-
0 Before
After
Figure 5 Mean (SD) plasma cortisol concentration (nmol L)1) in dogs submitted to false EA (T-false), bilateral EA (T-EA/bil), unilateral EA (T-EA/uni) and untreated animals (T-control).
physis (Melzack 1976; Han et al. 1980; He 1987; Kho & Robertson 1997). Endogenous opioids, such as endorphins, enkephalins, and dynorphins have also been well documented to contribute to the analgesic effect of acupuncture (Pomeranz 1987; Hsu 1996). The dense-disperse mode of electrical stimulation, with the frequency ranging from 10 to 1000 Hz, used in this study probably produced the release of a combination of endogenous opioids. Low-frequency EA increases the release of enkephalin, b endorphin,
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Electroacupuncture analgesia in dogs RN Cassu et al.
and endomorphin 1 and 2 (Han 1993; Huang et al. 2000) and high-frequency EA releases dynorphin in the spinal cord (Han 1993). Chen & Han (1992) observed that the l and r, j and l, r and j opioid receptors were activated after EA using the frequencies of 2, 100, and 2–15 Hz, respectively. The analgesic effect observed after transcutaneous and percutaneous electrical stimulation was more pronounced after the use of mixed frequencies, when compared with low or high frequencies (Ghoname et al. 1999; Hamza et al. 1999), showing that a mixed frequency appears to be ideal to produce analgesia during EA. The analgesic effect produced by unilateral EA was intermediate between the bilateral and false acupoint stimulation. A previous study showed that both unilateral and bilateral auricular acupuncture produced similar analgesic effects (Still et al. 1985). In our study, bilateral EA produced better analgesia than unilateral EA, with a shorter time to effect, longer duration of effect, and greater intensity of analgesia. The prolonged duration of analgesia in the animals undergoing bilateral EA suggests an endocrine participation in this effect. Pomeranz (1978) showed that b endorphin and serotonin are involved in the humoral response mediated by EA, producing long-term analgesia in rats, even after interruption of the electrical stimulation of acupoints. Some studies have demonstrated increased serotonergic activity (Cheng & Pomeranz 1981; Cui et al. 1999) and plasma endorphin concentration in response to acupuncture (Liao et al. 1980; Nappi et al. 1982; Bossut et al. 1983), because of either the increased production or the reduced reuptake and/or elimination of these hormones. The thoracic and abdominal cutaneous analgesia was more pronounced than the analgesia at the interdigital space, as at some time points there was no response to pain at the thoracic and abdominal areas, whereas there was always a response after interdigital stimulation. This difference in somatatopic response might have been influenced by the points selected. The ST36 and SP6 are the master points for the abdominal region. In horses submitted to EA, there was no analgesia of the head or limbs using the points Ba Shan (BL53), Bai Hui (GV20), and Yao Pang or Ye Yan (PC6), San Yan Lu (TH8), and Qiang Feng (TH13) (Bossut et al. 1983). However, analgesia was observed in both fore and hind limbs in sheep undergoing EA at Yao Pang, Bai Hui, San Yang Lui, and Qiang Feng (Bossut et al. 58
1986). In a similar study, EA at the acupoints ST36 and SP6 produced analgesia in the hind limbs of rats (Oliveira & Prado 2000). These differences may be produced by the pain inhibitory system activated in each situation (Bossut et al. 1983). Watkins et al. (1982) reported that different pain modulation systems are activated in pelvic and thoracic limbs in rats. Analgesia of the thoracic limbs, but not in the pelvic limbs, was reversed by naloxone administration, showing that the endogenous opioids do not take part in the pain suppression response in pelvic limbs. In the present study, pain stimulation was performed in the thoracic limb as it is a general consensus that acupuncture-induced analgesia is partially mediated by endogenous opioids. Practically, it was recognized that the animal’s reaction to the stimulus might remove the needles inserted into the hind limbs if the pelvic limb had been used for the noxious stimulus. The sedation with acepromazine was necessary in order to avoid undesirable reactions as a result of manipulation, restraint, recumbency, monitoring, insertion of needles, and electrical stimulus for a long period. In sick animals, the use of acupuncture is well tolerated, and this difference may produce conflicting results when clinical and experimental studies are compared (Wright & Mcgrath 1981). Acepromazine might have compromised the results, as it depresses the CNS and cardiovascular system, modifying the responses against noxious stimuli. Low doses of acepromazine (0.05 mg kg)1) produce sedation for 1–2 hours (Brock 1994). Acepromazine might also potentiate the EA-induced analgesia (Rogers 1982). This study showed a difference between true EA and false EA, but the magnitude of the effect of acepromazine cannot be determined as it was administered to all dogs for all treatments. The stimulation of false points, even with restraint and electrical stimulation did not increase the pain threshold, as previously reported in rats (Oliveira & Prado 2000) and in dogs (Still et al. 1986), showing that EA and not stress, was responsible for the analgesia. Further confirmation of the above statement is provided by the lack of change in plasma cortisol concentrations in any treatment, as reported previously (Pellegrin et al. 1980; Masala et al. 1983; Pullan et al. 1983; Umino et al. 1984; Luna & Taylor 1998). Electroacupuncture at real points was more successful in producing analgesia than at false EA points. Other studies in rabbits (Takeshige 1985), cats (Dorman & Gage 1978), rats (Toda et al. 1980;
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Electroacupuncture analgesia in dogs RN Cassu et al.
Iriki 1982), and humans (Pomeranz 1987; Kho & Robertson 1997) also reported that acupuncture at real points produced more analgesia than at false points. False points produced analgesia in only 3% of the animals submitted to acute pain models (Pomeranz 1987). On the contrary, false points can produce analgesia in 30–35% of human chronic pain patients (Pomeranz 1987). It seems that stimulation of any point in the body may increase pain threshold. However, a better effect is achieved when real acupoints are used or when the points stimulated are from the same area of innervation as the acupoints (Kho & Robertson 1997). In this study, the needles of the false points were inserted at the same dermatome, using the same kind of electrical stimulation according to Gaw et al. (1975) and Fung & Chow Okw (1986), respectively, to simulate, as closely as possible, the technique used for the real acupuncture treatment. Accordingly, a possible dermatome effect and stimulation technique can be discounted by our results. Previous reports showed that stimulation of the muscle fibers produce muscle action potentials and participate in the acupuncture effect (Kendall 1989). This effect is produced by the intrafusal muscle tissue and gamma 2 type motor fibers, remaining even when the nervous and vascular supply are interrupted (Kendall 1989). The intensity of the muscle action potential is dependent on the quantity, presence and distribution of intrafusal muscle fibers in specific acupoints (Yan et al. 1984). One of the reasons for selection of the ST36 acupoint in this study was that it produces a much higher muscle action potential when compared with other acupoints (Yan et al. 1984). The use of EA alone to produce surgical anesthesia does not seem to be very ethical, as it is not effective in 100% of the cases. However, considering the absence of side effects and the low cost, EA could be used as a complement to other analgesic techniques to reduce the amount of anesthetics and analgesics used perioperatively (Janssens et al. 1988; Wynn et al. 2000). Cardiorespiratory variables were not affected by EA. Similar studies of EA in dogs (Wright & Mcgrath 1981) and sheep (Bossut et al. 1986) showed no cardiorespiratory effects either. The decrease in rectal temperature in all treatments was probably produced by the vasodilatory effect of acepromazine; however, this finding was not clinically significant, as temperature was always above 38.0 C.
The calm behavior observed in most of the dogs in this study is a typical finding of EA in several species and might be related to the release of endogenous opioids (Bossut et al. 1986; Luna & Taylor 1998). The absence of cardiorespiratory and behavioral changes typical of stress during EA shows that it is unlikely that EA-induced analgesia is produced by stress (Bossut et al. 1986). Acupuncture might reduce stress (Lin & Rogers 1980), as plasma cortisol concentration was reduced in stressed rabbits after acupuncture (Liao et al. 1980) and the parasympathomimetic effect of ST36 has been useful to treat hypertension in humans (Tam & Yiu 1975) and rats (Lee 1974). In conclusion, bilateral EA produced a shorter latency period, a greater intensity, and longer duration of analgesia, than unilateral stimulation, without a stress response. According to these results, bilateral EA should be used instead of unilateral EA, because of the better analgesic effect produced by the bilateral EA. References Banzatto DA, Kronka SN (1995) Experimentac¸a˜o agrı´cola. (3rd edn), Funep, Jaboticabal. p. 247. Barbieri O, Bellone G, Manfredi C et al. (1979) Acupuncture analgesia in eye surgery. Minerva Med 70, 3853–3856. Bossut DFB, Leshin LS, Stromberg MW et al. (1983) Plasma cortisol and beta-endorphin in horses subjected to electro-acupuncture for cutaneous analgesia. Peptides 4, 501–507. Bossut DFB, Page EH, Stromberg MW (1984) Production of cutaneous analgesia by EA in horses: variations dependent on sex of subject and locus of stimulation. Am J Vet Res 45, 620–625. Bossut DFB, Stromberg MW, Malven PV (1986) EA-induced analgesia in sheep: measurement of cutaneous pain thresholds and plasma concentrations of prolactin and b-endorphin immunoreactivity. Am J Vet Res 47, 669–676. Brock N (1994) Acepromazine revisited. Can Vet J 35, 458–459. Caracausi SR (1979) Electro-acupuncture in thoracic and cardiovascular surgery. Minerva Med 70, 3857–3860. Chen XH, Han JS (1992) Analgesia induced by EA of different frequencies is mediated by different types of opioid receptors: another cross-tolerance study. Behav Brain Res 47, 143–149. Cheng RSS, Pomeranz B (1981) Monoaminergic mechanisms of EA analgesia. Brain Res 29, 77–92. Cheng R, Mckibbin L, Roy B et al. (1980) Electroacupuncture elevates blood cortisol levels in naive horses: sham treatment has no effect. Int J Neurosci 10, 95–97.
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