Two main mechanisms of postanesthetic shivering are hypothermia and recalibration of the temperature setpoint to a higher level [1, 18, 19]. The management of postanesthetic shivering must focus on correcting these pathophysiologic changes [20–22], as preserving the patient’s body heat is an important issue. Butwick et al.  used a warming device to preserve body heat, and other physicians [9, 20, 21, 24, 25] have used drugs to constrict the blood vessels, thus preserving body heat.
The effect of drugs in preventing postanesthetic shivering has previously been investigated and compared [9, 24, 25]. To the best of our knowledge, ours was the first study to examine the application of electroacupuncture to prevent postanesthetic shivering during regional anesthesia. Our results (Table 3) showed that electroacupuncture exerted a significant antishivering effect compared with the placebo treatment. Furthermore, severe shivering (grade 4) was significantly lower in Group A than Group P (Table 4).
Lin et al.  proposed that stimulating acupoint ST36 may produce a slight increase in oral temperature, with a simultaneous decrease in the cutaneous temperature of the limbs (measurement limited to certain skin locations). The same researchers extended their study to record additional skin locations, and the results indicated that stimulation of ST36 on the left leg produced vasoconstriction in both legs, but not in either arm . Reasons for the discrepant findings between the 2 studies were uncertain but may have included different needling depths (0.5 to 1.3 cun versus 0.5 to 2.3 cun). Dyrehag et al.  found that skin temperature tended to decrease after 30 min of electroacupuncture stimulation. This evidence supports the hypothesis that acupuncture to ST36 may lead to peripheral vasoconstriction.
In traditional Chinese medicine (TCM), ST36 is a Xiahe and He point of the stomach meridian of Foot-Yangming, and ST37 is a Xiahe point of the large intestine meridian. Clinical observation has shown that performing acupuncture on ST36 produces a clearer shape in the radial pulse. This finding may mean that the borders of the radial pulse emerge, which TCM physicians are able to detect by manipulation of the radial pulse through pushing or other movements. We speculated that this phenomenon may be attributed to peripheral vasoconstriction. We also hypothesized that acupuncture to ST36 may facilitate the preservation of heat. In addition, the Dao Ma needling technique, which is characterized by penetrating 2 to 3 adjacent acupuncture points simultaneously, is widely employed by Tung-style acupuncturists to enhance the therapeutic effect . Based on these reasons, we chose the 2 acupuncture points of ST36 and ST37 for pretreatment of postanesthetic shivering.
Our results suggested that electroacupuncture to ST36 and ST37 could preserve core body temperature during regional anesthesia. According to our data, the mean tympanic temperature of patients increased slightly after 30 min of electroacupuncture treatment (before administration of spinal anesthesia), compared with baseline. In both the treatment and placebo groups, mean core temperature then gradually declined after anesthesia. However, this drop in temperature differed significantly between the 2 groups. The mean core temperature remained higher in Group A compared with Group P at the same time point (Figure 4).
Our findings indicated that acupuncture to ST36 and ST37 did not prevent bradycardia or hypotension after spinal anesthesia. The rate of bradycardia and hypotension (defined as a decrease in mean blood pressure of more than 20% from baseline) within 30 min after anesthesia did not differ significantly between groups. We also found no significant difference between the 2 groups for postanesthetic heart rate and mean blood pressure; in both groups, these 2 measurements declined step by step in a similar pattern. This result was similar to those of previous studies of drugs to prevent shivering [9, 20, 24, 25]. The rate of nausea and vomiting, and of hallucination, did not differ significantly between the 2 groups (Table 2).
Previous studies have demonstrated that preoperative electroacupuncture on bilateral ST36 (Zusanli) acupoints with low and high frequency both can postpone time for the first dose of pethidine after operation and decrease the PCA demands and total morphine delivered in patients undergoing lower abdominal surgery . Patients enrolled into the study underwent ureteroendoscopy, which is not major abdominal surgery, and suffered almost no pain in the operative room or postanesthetic room. There was no analgesic requirement for these patients. In view of this, it remains unknown whether electroacupuncture has led to pain-related phenomenon and side effects in our current study.
Previous studies have also shown that low frequency electroacupuncture at acupoints of lower extremities attenuates sympathetic nerve activity, which may mediate muscle shivering for heat production . In this regard, low frequency electroacupuncture was selected as the treatment modality in the present study. In our pilot study setting, we adjusted the electric current based on the conception of patients. Current was tuned up to an amplitude that patient felt little but acceptable twitching, and then was tuned back to an amplitude that patient almost did not feel any twitching. We found that most patients did not feel any twitching with a current of 1 mA.