This was a pilot prospective interventional study from January 2020 to October 2023. This study was approved by the ethics review committee of Fuxing Hospital, Capital Medical University (Ethics approval number: 2020FXHEC-KY036). Trial registration number: NCT03524950. All patients signed the informed consent form. This study occurred 100 patients (The power of 0.9 and Alpha of 0.05 were calculated by PASS15 (NCSS Corp., Kaysville, UT, USA), and the sample size was 76, with 38 cases in each group. Considering a 10% increase in sample, a total of 100 patients were included. The two studies were divided into two groups with 50 cases in each group by random number table method). The inclusion criteria: patients aged 40–60 years, American Society of Anesthesiologists (ASA) class 1–2, and undergoing laparoscopic UF surgery under general anesthesia. The exclusion criteria: (1) hypertension; (2) thyroid disease; (3) adrenal disease; (4) acute or chronic renal disease; (5) impaired liver function; (6) obesity (body mass index (BMI) $>$30 kg/m${}^2$); (7) history of severe obstructive sleep apnea-hypopnea syndrome (OSAHS); (8) psychological disorders or mental disorders; (9) autonomic nervous diseases; (10) diabetesmellitus.

One hundred patients were randomly assigned to two groups by computer random number table method: dexmedetomidine group and non-dexmedetomidine group. Random numbers were sealed in envelopes. Prior to the operation, the nurse who did not participate in the study opened the envelope and prepared the experimental drugs according to the grouping assignment in the envelope.

Dexmedetomidine group: study medication was: 0.2 mg of dexmedetomidine (Yangzijiang Pharmaceutical Company, Taizhou, Jiangsu, China) diluted with normal saline to 50 mL. The injection rate was 1 µg/kg/h of dexmedetomidine and the injection time was 10 minutes before anesthesia induction. The injection rate was 0.7 µg/kg/h of dexmedetomidine during the maintenance phase with discontinuation occurring 30 minutes before the end of the operation.

Non-dexmedetomidine group: study drug was: normal saline 50 mL. The dosage was calculated according to dexmedetomidine group.

Prior to induction of anesthesia, the experimental drugs were injected into both groups by an intravenous infusion pump for 10 minutes (pump speed: 1.0 µg/kg/h calculated according to dexmedetomidine). Patients in both groups received the experimental drug at a pump rate of 0.7 µg/kg/h and the infusion was continued until half an hour before the end of surgery. Other induction drugs used in both groups were: sufentanil 0.5 µg/kg (IDTBiologikaGmbH, Beijing, China), propofol initiated at 6 µg/mL via target-controlled infusion (TCI), and rocuronium 0.6 mg/kg.

During the maintenance phase of anesthesia, both groups received remifentanil (0.1–0.3 µg/kg/min; Yichang Renfu Pharmaceutical Co., Ltd., Yichang, Hubei, China) and propofol (AstraZeneca, S.P.A, Milano, Lombardia, Italy) continuously. The injection speed of the propofol pump was adjusted according to the bispectral index (BIS) value, with BIS value maintained between 45–55. When blood pressure rises to 30% of baseline, 10–30 mg of urapidil hydrochloride is injected intravenously. When blood pressure is reduced by 30% from baseline, 6–10 mg of ephedrine hydrochloride (Northeast Pharmaceutical Group Company Shenyang first pharmaceutical factory, Shenyang, Liaoning, China) is injected intravenously Vasoactive drugs could be reused after 10 minutes. There was no reduction in blood pressure in this study, therefore ephedrine hydrochloride was not used. After surgery: an intravenous analgesia pump was utilized (100 mL). Tropisetron Hydrochloride injection 5 mg and Flurbiprofen Axetil injection 50 mg were administered intravenously half an hour before the end of surgery to prevent postoperative nausea, vomiting and pain. When the postoperative visual analogue scale (VAS) of the patient was more than 5, Flurbiprofen Axetil injection 50 mg was injected intravenously.

The surgeon performs the operation through three small puncture sites made in the patient’s abdomen. The surgeons were senior gynecologists who have performed more than 500 laparoscopic UF surgeries.

(1) General information of the patient, included: age, height, weight, uterine fibroids diameter, number of fibroids, anesthesia time, spontaneous breathing recovery time, consciousness recovery time, extubation time, and recovery room time.

(2) Post‑operative pain: visual simulation scoring method (visual analogue scale, VAS) scores were recorded at 0.5 h, 1 h, 12 h and 24 h postoperatively. The VAS score was graded on a scale of 0–10. The score 0 was no pain and 10 was unbearable pain. The higher the score, the higher the pain level.

(3) Post operative stress response: Richmond Agitation-Sedation Scale (RASS) was recorded at 0.5 h, 1 h, 12 h and 24 h after the operation. The sedation score is on a 10-point scale, from –5 to 4.

A scale of –5 to 0 indicates coma to wakefulness, and the higher the score, the better the wakefulness. On a scale of 0 to 4, it ranges from wakefulness to agitation and violent behavior. The closer the score is to zero, the better the level of wakefulness.

(4) Postoperative chills (involuntary shaking of the whole body or part of the muscles occurs after surgery), nausea, and vomiting were recorded.

SPSS 26.0 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. The continuous variables conforming to the normal distribution (Kolmogorov-Smirnov test) were presented as means $\pm$ standard deviations and analyzed using the independent sample t-test, Categorical variables were expressed in frequency (%) and analyzed using Chi-square tests. RASS and VAS were expressed by p50 (p25, p75), and Mann-Whitney U test was used for data analysis. p-values 0.05 were considered statistically significant.

There were 50 patients in each group (Fig. 1). Their baseline characteristics are shown in Table 1. There were no significant differences in age, height, weight, diameter, or number of uterine fibroids between the two groups (Table 1).

Fig. 1.

Flow chart. UF, uterine fibroids.

There was no difference in anesthesia time. There were differences in spontaneous breathing recovery time, consciousness recovery time, extubation time, recovery room time (Table 2), chills and nausea between the two groups (Table 3).

Dex group has a RASS value closer to zero than non-DEX group. There was no significant difference in RASS at 1 h, 12 h, 24 h (Table 4). The VAS of the DEX group was smaller than that of the non-DEX group at half an hour, but there was no significant difference in VAS at 1 h, 12 h and 24 h (Table 5).