Preoperative anxiety is the most frequent burden affecting patients before various surgical procedures [1
]. Facing the prospect of surgery and hospitalization, patients experience fear, anxiety, uncertainty, loss of control and decreased self-esteem [2
]. More than 90% of adult patients scheduled for elective surgery developed preoperative anxiety, and 40.5% reported severe anxiety [3
]. Although the preoperative anxiety is a kind of situational anxiety, which terminates itself when the underlying condition (surgery) is over, it causes a profound psychological and physiological response via the release of stress-hormones, that may be associated with a worse postoperative recovery, higher intensity of acute and persistent postsurgical pain and greater anesthetic requirement as well as impaired quality of life in the postoperative period [4
A large variety of approaches is used to treat preoperative anxiety including both psychological and pharmacological interventions; however, none of them seem to be ideal in providing effective, safe and low-cost therapy [9
Auricular stimulation (including acupuncture and comparable techniques such as electroacupuncture and acupressure) is a method of complementary medicine, based on stimulation of cranial nerves. It has already been used to treat situational anxiety in experimental and clinical conditions [12
]. In several randomised controlled trials (RCTs) evaluating a treatment of preoperative anxiety, auricular stimulation was superior to an array of control procedures, including placebo and sham interventions, and equally effective like premedication with benzodiazepines in patients scheduled for surgery under general anesthesia [13
]. Moreover, this method was associated with fewer side effects compared with benzodiazepines, as well as a diminished physical stress reaction such as a reduced response of the autonomic nervous system [12
The potential mechanism of auricular stimulation is attributed to the neuroanatomical conditions of external auricle. It is presumed that auricular stimulation exerts its anxiolytic effects via the involvement of cranial nerves [18
], which leads to the modulation of the brain areas involved in the stress response, including the limbic system, locus coeruleus and hypothalamus [19
Although the majority of RCTs on auricular stimulation for preoperative anxiety were in favor of this technique, these clinical investigations demonstrated a heterogeneity in regard to surgical procedures, control conditions and effect size, thus making it difficult to draw any definitive recommendations. It seems possible that auricular stimulation might serve as an effective replacement for insufficient conventional pharmacological premedication [9
], thus more accurate estimation of the efficacy and safety of this complementary medicine intervention is needed. Therefore, this planned systematic review, including a meta-analysis of RCTs, will be performed to evaluate the effect size of auricular stimulation on preoperative anxiety applied alone or in addition to standard care in comparison with various control conditions. Data on the efficacy and safety of treatment will be calculated and summarized. The review will also try to identify the factors that may influence the effects of this intervention.
Although almost 50% of adult patients scheduled for elective surgery suffer from preoperative anxiety [3
], there is no ideal method to treat this kind of situational anxiety in clinical conditions so far. Pharmacological premedication is convenient in preoperative setting, however it seems to be less effective than previously suggested, if compared with placebo in trials with rigorous designs [9
]. Psychological (cognitive-behavioral) approaches seem to be effective and lack dangerous side effects, however they are too time-consuming in their execution and thus are seldom used in routine clinical practice [24
An array of data suggest that auricular stimulation might become such an effective, safe and easy-to-perform treatment for preoperative anxiety in adults scheduled for elective surgery and painful procedures with sedation [12
]. Despite these promising results from clinical trials on the treatment of preoperative anxiety using auricular stimulation supported by neurophysiological explanation of its potential mechanisms [25
], the systematic evaluation of the evidence for the treatment of anxiety using auricular acupuncture is not available.
This review and meta-analysis will fill this gap, analyzing the RCTs based on this protocol, which was designed according to the PRISMA statement (Supplementary Materials
). The review will calculate and summarise the data on the efficacy and safety of auricular stimulation in the treatment of preoperative anxiety in adult patients scheduled for elective surgery.
The results of this systematic review may be biased, since only the trials described in European languages will be considered, excluding the full format papers in native languages from the countries of the Far East, where auricular stimulation is widely used in traditional medicine [26
]. Furthermore, the trials using transauricular vagal nerve stimulation (TaVNS) are considered to be beyond the scope of this review, despite the number of such trials growing rapidly in last two decades [27
In summary, this systematic review will evaluate the existing evidence on the treatment of preoperative anxiety using auricular acupuncture and related procedures. The scheduled meta-analysis will estimate the effect of auricular stimulation on several perioperative parameters that are known to be influenced by preoperative anxiety. The results of this review will provide the basis for a better understanding of auricular acupuncture in the treatment of perioperative anxiety and will yield the evidence for the implementation of this method in clinical practice.
The data search is being performed for the present systematic review.