Abstract: Electrical stimulation of selected acupuncture points can be used to induce surgical analgesia in small animals. The analgesia is achieved via activation of the endogenous pain-relieving mechanisms. The technique can be used on its own (in non-premedicated animals), or as a complement to drug/general anaesthesia. The author's research into the use of acupuncture analgesia in the dog and cat is reviewed.
Acupuncture analgesia (AA) can be considered as a valid technique for providing surgical analgesia. The first successful operation under AA was performed in humans in China, only in 1958. Surgical analgesia is achieved via strong electrical stimulation of steel acupuncture needles inserted in selected acupuncture points. The electro-stimulation must be continued during the 10 to 30 minute lasting induction period and throughout the surgery. In China, ten to 60% of surgical patients are reported to have been operated under AA.
Mechanisms of AA have been studied extensively in the People's Republic of China and other countries. These studies have revealed that AA operates via neurological mechanisms involving activation of the endogenous inhibitory systems within the spinal cord and brain. Various types of CNS neurotransmitters such as beta-endorphins, enkephalins, dynorphin, serotonin and norepinephrine are involved in AA (Stux and Pomeranz, 1987).
Numerous case reports and controlled studies on the use of AA in dogs, cats, horses, cattle and several species of laboratory animals have been published since the early 1970s.
Workers used various combinations of acupuncture points such as LI4, PC6, TH8, ST36, 43 and 44, SP6, BL60, segmental BL Shu and GV points. A strong electrical stimulation of the needles inserted in selected points was used. AC current at frequencies ranging between 1 to 150 Hz has been recommended. An induction period of 20 to 40 minutes was usually necessary to induce surgical analgesia. The success rate of AA for soft tissue surgery in non-premedicated or lightly sedated dogs varied from 10-100% depending on the study.
AA can be used on its own (in conscious animals), or as a complement to drug/general anaesthesia. The clinical experience of this author with the above two modalities of AA will be briefly reviewed.
Acupuncture analgesia in non-premedicated animals
In order to clinically evaluate the technique for surgery in conscious small animals, three modalities of AA were evaluated in a model of flank laparotomy in 23 dogs and 16 cats (Still, et al 1986, Still 1987; Still et al 1990a, Still et al 1990b). Clinically healthy adult animals of both sexes were used. With the exception of one dog which was slightly premedicated with chlorprothixene in order to provide mild sedation, no drugs were used in this study. Auricular projection zones for vertebral column, intestines and central nervous system, as well as so-called pre- and post-auricular zones were stimulated electrically (frequency 1-25 Hz, voltage up to 150 V, width of the bipolar impulses 0.2-0.6 msec) via steel acupuncture needles. Unilateral (Still et al 1986; Still et al 1990a); or bilateral (Still et al 1990b) electroacupuncture was tested.
In another study, analogous electrical stimulation was applied via needles inserted into the pre- and post-auricular zones, and acupuncture points BL23-24, GV2 (Bai Hui), GV6 and SP6 on the side of the body ipsilateral with the intended incision (Still, 1987).
Animals were gently restrained in the lateral recumbency during the induction period (20-40 min) and during the surgery. In the case of any pain reaction to the surgical intervention, further surgery was immediately stopped and continued only if no clinical reactions to surgery were seen after re-adjustment of parameters of the electrostimulation. Sufficiently deep analgesia allowing to carry out the surgical procedure (including incision of the abdominal wall, abdominal palpation and suturing of the incised wall) was achieved in 45 to 100% of animals depending on the species and the applied technique of AA.
Solid surgical analgesia and normal physiological performance immediately after termination of the surgery were the main advantages in responders to AA. Lack of surgical analgesia in a percentage of animals, variable intra-operative sedation and muscle relaxation and reactivity to environmental activities (noise, movement etc) were the main side-effects seen in the dogs and cats poorly responding to the stimulation.
It was concluded that the method (when applied in non-sedated/non-anaesthetised animals) was not sufficiently reliable in order to satisfy practical requirements of current veterinary anesthesia.
Acupuncture analgesia in anaesthetized animals
Theoretically, additional AA may be beneficial to the anaesthetised patient via providing intra- and post-operative analgesia and via reducing requirements for anaesthetic and analgesic drugs. AA might be further useful to an anaesthetised patient by improving its intra- and post-operative performance through stimulation/balancing of the body's homeostatic functions and modification of the metabolic responses to surgery.
Clinical studies testing the anaesthetic use of AA in man suggested that the inclusion of the technique assisted in reducing requirements for additional intra-anaesthetic analgesic and anaesthetic medication, while maintaining good to excellent cardiovascular stability of the patients. A modest, yet statistically significant reduction of 11% to 17% of the minimum alveolar concentration (MAC) of halothane in the dog (using bilateral electrostimulation of SP6) has been demonstrated by Tseng et al (1981). Using electrostimulation of six selected acu-points (LI4, LU7, GV 14 and 20, San Tai and Baihui), Skarda et al (2003) demonstrated a reduction of MAC of isoflurane by 16.7 % in dogs. The technique of AA can thus potentiate the anaesthetic effects of volatile anaesthetic agents.
As compared to the fentanyl (opioid analgesic) control group, no significant elevation of the stress hormones including adrenaline, noradrenaline, adrenocorticotropin hormone, beta-endorphin, antidiuretic hormone and cortisol was found in human patients anaesthetised for routine abdominal surgery (Kho, Kloppenborg and Egmond, 1993). The findings support the idea that AA does not operate primarily via activation of the body stress mechanisms.
Recently, a clinically-orientated blinded study aiming at evaluation of AA as a part of balanced anaesthesia for routine abdominal surgery in dogs was conducted (Still et al, 1998). Clinical, respiratory, cardiovascular as well as haematological, metabolic and hormonal effects of auricular electroacupuncture were compared to opioid analgesia (buprenorphine) and a control group without any analgesic medication or acupuncture in the course of the surgery (ovariohysterectomy) and two days post-operatively.
Thirty healthy crossbred bitches were premedicated with acepromazine, induced with thiopentone and maintained under halothane anaesthesia. The dogs were then ascribed at random to the three experimental groups (n=10). In the acupuncture group, two steel acupuncture needles were inserted subcutaneously into the auricular projection zones of the "spinal cord" and "central nervous system" on the left external auricle. The needles were electrically stimulated using a low intensity AC current of frequency 2 Hz during the 15-minute induction period and throughout the surgery.
A standard midline ovariohysterectomy surgical technique was used. Anaesthetic plane was kept as light as compatible with surgery. The anaesthetic respiratory and cardiovascular performance, as well as the end-expiratory concentration of halothane were monitored throughout the surgery lasting 20 to 30 minutes. Duration and quality of the post-anaesthetic recovery were evaluated using a standard clinical protocol. Blood gas analysis was performed in samples of arterial blood and samples of venous blood were used for determination of more than 40 parameters of clinical biochemistry and haematology. All clinical procedures were blinded.
Clinically satisfactory values of monitored parameters were found in most of animals of the control group. With respect to this favourable baseline, only relatively minor, mostly statistically insignificant differences were found between this and the acupuncture and buprenorphine groups respectively. Post-anaesthetic recovery tended to be delayed in the buprenorphine group, as compared to the other groups. The method of AA was found to be clinically safe.
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