The effect of auricular acupuncture on preoperative blood pressure across age groups: a prospective randomized controlled trial

ABSTRACT

Purpose

To determine the effect of auricular acupuncture on preoperative blood pressure (BP) elevation in different age groups.

Materials and methods

Auricular acupuncture treats elevated BP among patients before surgery. This prospective, randomized clinical trial was performed at Li Huili Hospital of Ningbo Medical Center, China, from January to June 2021. We prospectively enrolled 120 patients with elevated BP aged 45 to 75 and observed them in the inpatient department. Patients were randomly assigned in a 1:1 ratio to undergo auricular acupuncture or sham control groups. In addition to usual care, the study group underwent auricular acupuncture bilaterally at HX6 7i–Ear apex, TF4–Shen men, TF1–Superior triangular fossa, and CO15–Heart.

Results

A total of 120 patients completed the study, 60 in the study group and 60 in the control group. Of these, 76 (63.3%) were men, and the mean (standard deviation) was 64.55 (9.48) years. The differences in systolic BP comparisons after intervention were significant (7.88 mmHg; 95% confidence interval [CI], 2.94 to 12.81; P = .002). Diastolic BP also showed statistical significance (5.85 mmHg; 95% CI, 3.05 to 8.64; P < .01. Neither AA-related adverse events nor serious adverse events occurred. Stratified by age, the differences comparisons of systolic BP (−10.13 mmHg; 95% confidence interval [CI], −16.69 to −3.57; P < .01) and diastolic BP (−7.65 mmHg; 95% confidence interval [CI], −11.17 to −4.14; P < .01) were statistically significant for participants aged 60–75 years; The differences comparison of systolic BP (−2.37 mmHg; 95% confidence interval [CI], −8.04 to 3.31; P = .40) and diastolic BP (−1.46 mmHg; 95% confidence interval [CI], −5.68 to 2.76; P = .48) were not significant aged 45–59.

Conclusion

Auricular acupuncture can reduce BP before procedures. However, further research is needed on the antihypertensive effect on people aged 45–59. These findings provide clinicians with evidence of auricular acupuncture as a standard adjunctive therapy targeting this patient population.

KEYWORDS:

• Auricular acupuncture
• Blood pressure
• Randomized controlled trial
• Preoperative
• Hypertension

Introduction

Preoperative hypertension is a complex problem, encompassing patients with essential hypertension and those with elevated blood pressure (BP) related to surgical stress. Several studies suggested that preoperative hypertension is associated with increased perioperative risk (1,2). The surgery is a severe stressor that can cause vasovagal responses and unnecessary allostatic loads (3). Preoperative patients often produce hypertension via sympathetic nerve excitation due to anxiety. Minimizing stressful stimuli accompanying procedures is critical but often neglected in hospital routines (4). Preoperative hypertension is a common reason to cancel or postpone surgery, which will bring quantifiable losses of resources and unquantifiable, significant psychological, social, and financial implications for patients and families (3). Therefore, we focused on preoperative hypertension generated by surgery-related stress that requires immediate resolution.

Medications are used to reduce BP; however, they can cause unsafe drops in BP, especially in elderly patients. Substantial BP variability was significantly associated with coronary atheroma progression and major adverse cardiovascular events (5). Talk and relaxation therapies reduce BP and relieve anxiety; however, their effects need more research (6).

AA is a non-pharmacological treatment that is safe and effective in clinical practice (7–10). AA can stabilize the autonomic nervous system and reduce BP by activating and suppressing the parasympathetic and sympathetic nervous systems (11). Several well-designed randomized controlled trials of AA treating hypertension have been published (12,13). AA has a mild antihypertensive effect and does not cause sharp drops in blood pressure. Nevertheless, there is little evidence of the ability of AA to reduce BP elevated due to the stress surrounding surgery. There are few studies on the effect of AA on hypertensive people or in specific age groups. Therefore, we designed this study to determine the preoperative pressure effect of AA on patients of different ages.

Methods/design

Design

This study was a randomized trial of AA to treat preoperative hypertension. The trial was conducted at Li Huili Hospital of Ningbo Medical Center from January to June 2021. All patients provided written, informed consent prior to randomization. The Ethics Committee of the Li Huili Hospital of Ningbo Medical Center approved the trial protocol. Trial registration: Clinical Trials gov MR-33-20-005594.

Participants

We prospectively enrolled 130 patients from the Li Huili Hospital of Ningbo Medical Center. Finally, 120 patients were randomized into two groups (Table 1).

Table 1. Baseline demographic and clinical characteristics.

Characteristic	Mean (SD)		P value
	Study group (n = 60)	Control group (n = 60)
Age, y	63.55(9.82)	65.55(9.10)	.25
Body mass indexa	24.59(1.23)	24.74(1.79)	.58
Male, No. (%)	37(61.7)	39(65)	.70
Medical history, No. (%)
Hypertension	22(36.7)	20(33.3)	.70
Diabetes	8(13.3)	4(6.7)	.22
Medication, No. (%)
Antihypertensive drugs	22(36.7)	20(33.3)	.70
Controlled BP on ≥2drugs	12 (21.7)	11 (18.3)	.65
ACE inhibitors/angiotensin receptor antagonists	15 (25.0)	14 (23.3)	.83
Calcium channel blockers	7 (11.7)	6 (10.0)	.77
Diuretics	12 (20.0)	11 (19.2)	.82
Aldosterone antagonist	5 (8.3)	3 (5.0)	.71
oral antidiabetics	8(13.3)	4(6.7)	.22
Surgical classification 1^1 (%)
Two-level	25(41.7)	28(46.7)	0.63
three-level	28(46.7)	23(38.3)
four-level	7(11.7)	9(15.0)

Inclusion criteria

1. Scheduled for nasopharyngeal surgery under general anesthesia.

2. American Society of Anesthesiologists physical status classification of I or II.

3. Systolic BP (SBP) ≥ 130 mmHg or diastolic BP (DBP) > 80 mmHg on the day of surgery morning (14).

4. Age 45–75 years.

5.Willingness to participate and signed an informed consent form.

Exclusion criteria

1. Hypertensive crisis (220/140 mm Hg) and DBP 120 to 130 mm Hg (15).

2. History of syncope resulting from applying needles or contraindications to using needles.

3. Previous use of opioid or psychotropic medication.

4. Canceled surgery.

5. Complications during treatment (e.g., auricular skin infection or pain).¹

Recruitment procedures

We recruited participants using advertisements for the hospital. All participants were informed that there were two study groups, i.e., an AA group and a sham control group, with 50% of the allocation. If patients were taking antihypertensive medications, they were instructed to continue them. All were informed of their right to withdraw from the trial (Figure 1).

Figure 1. Flow diagram depicting the study design.

Randomization

One appointed investigator was responsible for the randomization. Complete randomization was performed using the random number generator in SPSS 23.0 (IBM Corp, Armonk, NY). After establishing selection criteria, the recruiters obtained numbers from the assigning investigator and randomly assigned patients to the study or control groups. The groups were assigned to separate wards to prevent communication.

Interventions and comparison

Study group

In addition to usual care(disease awareness, dietary guidance, exercise, and psychological care), the participants received AA treatment based on the theory of neuroanatomy (16), the literature (17,18), and a textbook (19). We chose the following auricular points(Figure 2): HX6 7i–Ear apex, TF4–Shen men, TF1–Superior triangular fossa, and CO15–Heart. The licensed acupuncturist had more than 5 years of experience in AA. When the patients were relaxed and prone, the acupuncturist held the upper posterior corner of the helix with one hand and located sensitive points with an auricular point detector using the other hand. The acupuncturist used 75% alcohol pads to sterilize the area, then inserted needles (Figure 3) (length 1.5 mm, diameter 0.22 mm; Seirin Corp, Shizuoka City, Japan) into the four auricular points bilaterally. The needles remained in situ. Subsequently, the acupuncturist instructed the patient to stimulate the auricular needles for 10s, with a 3-s pause between the two pressings (20). Optimal stimulation was achieved when the subject felt localized tingling pain. Auricular needles were removed before sending the patient to the operating room. The patient would enter the operating room accompanied by transport staff and wait about 15 minutes for anesthesia and surgery.

Figure 2. Auricular acupuncture used in the study group.

Figure 3. Baseline BP was measured the day after admission, BP before AA was measured at 6:00 on the day of the procedure, and BP after AA was measured 30 min before surgery. BPs between 45 and 75 years old include SBP and DBP. *P < .05 BP after AA for study group vs control group.

Control group

The control group received sham acupuncture. Acupuncture points and manipulation methods of sham acupuncture were the same as the study group. The fake needle is made of round tape with a diameter of 1 cm and no sharp needle. Its appearance, color, and shape were identical to the AA needle. Each acupuncture point received the same twirling motion as the acupuncture group.

BP measurement

The BP measurement device was validated. We had the patient relax and sit comfortably in a quiet room at a controlled temperature of 18–22°C. Neither the patient nor the observer talked during the measurement. We used the average of two readings obtained twice to estimate an individual’s BP level. The measurement interval was 10 minutes. All BP measurements were performed by nurses using the same training techniques.

Outcome

The primary outcome measure was a change in systolic BP, measured after AA intervention and immediately before surgery. Secondary outcomes were changes in diastolic BP after AA intervention and immediately before surgery and adverse events (i.e., pain, hematomas, skin damage, bleeding, and local infections) (Figure 3).

Safety and quality control

Adverse events were appropriately assessed and recorded by the observers. Severe adverse events would have resulted in stopping the trial. Two investigators independently collected and recorded the data in a computer to ensure safety and reliability.

Sample size calculation

The study was powered for a primary outcome measure of the difference in systolic BP in two groups before and after the intervention. We used the formula $n=\frac{\left(Z_{\alpha }+Z_{\beta }\right)\times 2{\sigma }^2}{{\delta }^2}$. N represents the sample size in each group, ϭ represents the standard deviation, and δ represents the between-group difference with clinical significance. At an α value of 0.05, we obtained Z scores of Z_a = 1.28 and Z_β = 0.84 from the Z score table. The sample size calculation was based on Tu et al., who showed a decrease of – 8.53 ± 13.50 mmHg in systolic BP in the control group (13). SBP was expected to decrease by 8.5 mmHg. A one-sided 0.05 level of significance provided 80% statistical power. To accommodate a 10% attrition rate, we needed to recruit at least 80 patients.

Statistical analysis

The data were analyzed using SPSS 23.0. Shapiro-Wilk tests were performed to determine the normality of data distribution. Continuous variables were expressed as means with standard deviations (SDs), and mean differences were expressed with two-sided 95% CIs. Between-group differences at baseline and changes from baseline to the end of the study were tested using independent t-tests. Paired t-tests were performed for within-group comparisons from baseline to the end of the study. Socio-demographic characteristics, disease-related characteristics, and homogeneity of dependent variables were analyzed using the chi-squared (χ2) test. The level of significance was a two-sided P-value less than 0.05.

Results

Recruitment and retention

All of the 120 patients who met the enrollment criteria agreed to participate. No patient terminated the study prematurely; all completed the follow-up assessments and were included in the analysis (Figure 1). Of the total, 76 (63.3%) were men, the mean (SD) age was 64.64 (10.9) years, and 35 (29.1%) were aged 45–59 years. Baseline demographic, clinical characteristics and surgery classification are displayed in Table.

Outcomes

The primary outcome (SBP after intervention) was more significant in the study group (mean 9.91 mmHg) than in the control group (mean 2.03 mmHg), with a mean difference of 7.88 mmHg (95% CI, 2.94 to 12.81; P = .002). The reduction in DBP after the intervention was more significant in the study group (mean, 6.30 mmHg) than in the control group (0.45 mmHg), with a mean difference of 5.85 mmHg (95% CI, 3.05 to 8.64; P < .01). There were no AA-related or severe adverse events (Figure 3).

Stratified by age, participants aged 60–75 years (SBP after intervention) in the study group (mean −10.83 mmHg) was more significant than the control group (mean 0.69 mmHg), with a mean difference of −10.13 mmHg (95% CI, −16.69 to −3.57; P = .003), the reduction in DBP (mean −7.19 mmHg) was more significant than the control group (0.46 mmHg), with a mean difference of −7.65 mmHg (95% CI, −11.17 to −4.14; P < .01). (Figure 4) However, participants aged 45–59 in the study group had no difference in SBP and DBP after the intervention compared with the control group. The reduction in SBP (mean −2.37 mmHg, 95% CI, −8.04 to 3.31; P =.40) and DBP (mean −1.46 mmHg, 95% CI, −5.68 to 2.76; P =.48) were not different from the control group.

Figure 4. Stratified by age, the chart shows the change in BP between 60 and 75 years old. BPs include SBP and DBP. *P < .05 BP after AA for study group vs. control group.

Discussion

Auricular therapy treats physical and psychosomatic diseases by stimulating specific points in the ears; it is a fundamental method in traditional Chinese medicine for returning the body to a harmonized, balanced state (21). Western investigators have also studied auricular points. In 1957, Paul Nogier proposed an inverted fetal image to describe the holographic theory. The manipulation of auricular therapy is based on the holographic theory, a sort of assumption that information regarding a part of the entire organism could be retrieved from the corresponding point of the ear, so that stimulation to a specific point of ear could ameliorate the function of the corresponding visceral organ or other part of the body (22).

Preoperative elevated BP is a frequent complication (23). In this trial, we aimed to clarify the efficacy and safety of AA for preoperative BP elevation. We found that AA reduced preoperative SBP and DBP. This phenomenon may involve baroreceptor responses and cardiovascular inhibition induced by auricular acupuncture (24). Hypertension is due to sympathetic nerve activity increased or vagally-mediated cardiac tone reduction (25). The auricular conchae are innervated by the auricular branch of the vagus nerve, and acupuncture at a concha can induce afferent projection through the vagus nerve to the nucleus of the solitary tract (11). Acupuncture has been used to treat high BP in China (26–28). Auricular acupuncture evokes cardiovascular inhibition similar to the baroreceptor in regulating cardiovascular function.

Hypertension maintains optimal levels and achieves less BP variability (19). BP changes even if patients are not diagnosed with hypertension (27). Medications may reduce BP too quickly and increase the risk of hypotension perioperatively. In our trial, AA safely altered BP, particularly systolic BP.

However, age is an influencing factor of BP in the guidelines, especially after age 60; the range of BP has changed. The population in our study was 45–75 years old, and the BP analysis was carried out according to the age factor, with 60 years old as the cutoff line. It is concluded that AA significantly affects preoperative BP control in 60–75-year-olds but not in 45–59- year-olds. This may be related to the small sample size of 45–59-year-olds; only 35 (29.1%) were aged 45–59 in this trial. This could be attributed to the individuals’ perceptions of the controllability of the stressor. Stress-induced increases or decreases in dopamine secretion in the nucleus accumbens depend on many factors (28). Stress-induced BP increases within a very short period in young individuals (29).

The acupuncture points we chose are unique; they stimulate cranial nerves that modulate stress-related brain areas (30). In a previous trial, five or more acupoints were used to lower BP. In our trial, we used only four points to simplify the treatment in the perioperative setting.

Surgery is a stressful event for most patients (31). BP can be reduced once sympathetic nerve excitation is relieved. When general anesthesia begins, the sympathetic nerve excitement is relieved. Therefore, we removed the needles at the beginning of the procedure and only studied patients with elevated BP preoperatively.

It is worth mentioning that the safety of AA should draw our attention, as it is a kind of traumatic intervention. We recorded no AA-related adverse events or severe adverse events. Our subcuticular needle (Figure 5) method circumvents the limitations of conventional acupuncture (fixed treatment and time, inconvenience of other medical operations during needle retention, and patient aversion to needles). In addition, we designed sham acupuncture. The fake needle is made of round tape with a diameter of 1 cm and has no sharp needle. Its appearance, color, and shape are identical to the AA needle. Most of the participants could hardly distinguish this device from real acupuncture.

Figure 5. Auricular acupuncture.

Limitation

Our findings suggest the safety and efficacy of AA as adjunctive therapy in patients with perioperative hypertension. Nevertheless, this study has several limitations. First, the study was the unblended single center. Second, the study lacked more extensive age stratification, there were no individuals under the age of 45, and there was an insufficient sample size for 45–59-year-olds. Further research is needed to address this issue.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Zhejiang Provincial Medical and Health Technology Project [2021KY1042].

Notes

¹ Surgical classification: In order to ensure the safety of patients, Chinese Ministry of Health issued the “Surgical Classification Catalog” in 2011. According to the risk and difficulty of the operation, the operation is divided into four grades.