Ninety children undergoing elective ophthalmic surgery, who were classified as ASA I-II, were selected in this prospective study from the Eye Hospital China Academy of Chinese Medical Sciences between June 2013 and November 2019. The children were randomly divided into two groups using the random number table method: 45 children received propofol-remifentanil intravenous anesthesia combined with regional block (LG group), and 45 children received intravenous anesthesia (G group). Informed consent from the guardians of the children was obtained and was approved by the ethics committee of the hospital.

The inclusion criteria: The types of surgery included eyelid mass excision, strabismus correction, eyelid entropion correction, frontalis muscle flap suspension, cataract phaco-emulsification, compound trabeculectomy, and vitrectomy.

The exclusion criteria: (1) Severe liver and kidney dysfunction or abnormal coagulation function. (2) History of upper respiratory tract infection within 1 month prior to surgery. (3) History of neurological or psychiatric disorders. (4) History of allergy to anesthesia drugs. (5) Delayed cognitive development or inability to communicate and cooperate verbally during the preoperative evaluation. (6) History of sleep apnea.

Prior to the surgery, the children were regularly subjected to an 8-hour fasting period and were prohibited to consume any drink for 4 h. Intravenous fluid access was established in the wards. An anesthesiologist who was not involved in anesthesia implementation and grouping completed all the preoperative and postoperative visits and the documentation of relevant intra-operative data to ensure the consistency of the assessment and statistical standards. Prior to the surgery, effective communication was established with the children at their pre-operative appointment to ensure their comprehension of anesthesia and awakening procedures. On the day of surgery, the anesthesiologist accompanied the child into the operating room and re-enforced the understanding of the child about the anesthesia process, and completed the subsequent evaluation and data collection. In the operating room, the children were routinely monitored for electrocardiogram (ECG), heart rate (HR), blood pressure (BP), bispectral index (BIS), saturation of pulse oximetry (SpO2), end-tidal carbon dioxide partial pressure (PETCO2), and respiratory rate (RR). Atropine is premedicated by intravenous injection prior to induction of general anesthesia at 0.01 mg/kg (with a controlled total of ≤ 0.3 mg).

Based on the weight of the child, reinforced laryngeal mask was selected accordingly (Medis Medical (Tianjin) Co., Ltd.). Prior to the induction 100% oxygen was administered using a mask for a duration of 3 min. Induction of general anesthesia was as followings: slow intravenous injection of propofol at a dose of 3–5 mg/kg and remifentanil at a dose of 1–1.5 µg/kg for more than 30 s in the LG group. Slow intravenous injection of propofol at a dose of 3–5 mg/kg and sufentanil at a dose of 0.6 µg/kg, in the G group. Following the loss of consciousness in the child, when normal breathing ceased entirely and jaw muscle tone diminished, a laryngeal mask was inserted to facilitate mechanical ventilation. The maintenance of general anesthesia was as follows. After induction of general anesthesia in the two groups, the patients were injected intravenously with propofol at of 6–8 mg/kg/h and remifentanil at 15–20 µg/kg/h. The BIS value was maintained at 40 to 60 until the general anesthesia was stopped. All children were given 10 mg of lidocaine intravenously before propofol administration to relieve propofol-induced intravenous pain. Propofol and remifentanil pumping was stopped about 5 min before the end of surgical procedure. Children in the LG group were given regional nerve block by the operators after their general anesthesia. The specific steps were as follows: 2 to 4 ml of 0.375% ropivacaine and 1% lidocaine mixture for local infiltration anesthesia or retrobulbar nerve block. The retrobulbar nerve block is considered effective with the presence of pupils dilated and fixed in the center. For surface anesthesia, 0.4% oxybuprocaine, was used along with intermittent additional 2% lidocaine intra-operatively. Group G was given an equal amount of normal saline as placebo for local injection.

The mechanical ventilation process was as follows: The pressure-controlled ventilation method was used in both groups, and the airway pressure was adjusted so that the tidal volume (VT) reached 10–12 ml/kg, the RR 18–20 times/minute, and the inspiratory/expiratory ratio (I: E) 1:1–1:1.5, and a PETCO2 level of 35–45 mmHg.

After surgery, the child was transferred to the post anesthesia care unit (PACU). In PACU, continue to perform mechanical ventilation and monitor vital signs, and observe and record all vital indicators. Remove the laryngeal mask after meeting the conditions.

Indications for laryngeal mask removal were as follows: The child regains consciousness and starts spontaneous respiration, is able to open the mouth, raise the head, and take deep breaths on command or has movements such as raising the head, opening the mouth, and coughing.

The child can leave the PACU when all of the following criteria are met: (1) The child is awake and can communicate and complete command actions; (2) After the laryngeal mask is removed, the patient can be transferred out of PACU by maintaining SpO2 > 94% for more than 10 min under the condition of spontaneous breathing without oxygen inhalation; (3) Pain, PONV, EA and other conditions were effectively controlled.

The main observational indicator was awakening time after general anesthesia. Secondary outcomes were removal time of laryngeal mask, duration of the operation, heart rate, the incidence of intraoperative and postoperative adverse events (including physical response, EA, respiratory depression, PONV and so on) and postoperative pain scores.

Awakening time after general anesthesia: It refers to the time from the end of general anesthesia to opening eyes voluntarily [6].

Removal time of laryngeal mask: It refers to the time period from the discontinuation of anesthetics to the removal of the laryngeal mask [6].

Heart rate: The heart rate of the child at the three time points; after entering the operating room (HR-T1), immediately after inserting the laryngeal mask (HR-T2), and immediately after removing the laryngeal mask (HR-T3) were set as the observation indicators. If the heart rate dropped by more than 20% during the operation, atropine at a dose of 0.005 mg/kg was administered. In the case of the presence of a drop in blood pressure more than 20%, then 1 to 3 mg of ephedrine was administered. The medications were readministered if necessary.

Physical response: The frequency of frowning, choking, swallowing, shaking head and any movement of the limbs occurring during the induction of general anesthesia and its maintenance were respectively recorded. When the physical reaction occurred, remifentanil at a dose of 0.5 µg/kg was administered intravenously, and if accompanied by a BIS value higher than 55, propofol at a dose of 1 mg/kg was added intravenously.

EA: EA (Emergence agitation and early postoperative agitation) was assessed on a four-point scale as follows [6]: (1) calm; (2) Not calm but easily amenable to reassurance; (3) Not easily calmed, marked by moderate agitation or restlessness; and (4) Combative, excited, or disoriented. Grades 1 or 2 were construed as indicative of the absence of agitation, and grades 3 or 4 were considered as evidence of the presence of agitation. The children were evaluated at three time points—5 min after the laryngeal mask was removed (EA-T1), when they left the recovery room (EA-T2), and at 2 h postoperatively (EA-T3)—to determine whether they experienced EA. For EA patients who can communicate and have no obvious pain, they are transferred directly out of PACU and transferred to their parents. For EA patients who were unable to communicate verbally, propofol was given intravenous sedation of 1-2 mg/kg, and continued monitoring and observation, and transferred out of PACU after EA symptoms were relieved. For patients with pain, sufentanil was administered slowly by intravenous injection of 0.1 µg/kg.

Respiratory depression: The criteria for respiratory depression [7] were as follows: RR less than 8 beats per minute or SpO2 less than 90% in case of calm breathing after the laryngeal mask was removed. Verbal prompts were promptly administered upon the initiation of respiratory depression, and mask oxygenation was administered until the SpO2 reached 100%. In instances where deemed necessary, assisted ventilation with a mask was initiated.

PONV: It refers to a significant vomiting reaction that occurs within 5 min after the laryngeal mask is removed and continues up to 2 h postoperatively. PONV was treated by intravenous ondansetron 0.1 mg/kg.

Postoperative pain scores: The pain score was assessed at the time of leaving the recovery room (PA-T1), 2 h after surgery (PA-T2), and 24 h after surgery (PA-T3), respectively, using the Faces Pain Scale Revised (FPS-R method) [8]. The scale utilized ranges from 0 to 10, with higher scores indicative of a greater degree of pain. If the recorded score equals or surpasses 6, sufentanil was administered at a dosage of 0.1 µg/kg via gradual intravenous injection. If sufentanil administration occurred in PACU, the pain score of the child leaving the recovery room was the same as before sufentanil administration.

In addition, the duration of the operation and the occurrence of other adverse events such as laryngospasm or tracheospasm, reflux and aspiration, sore throat or local anesthetic toxicity were also observed and recorded.

The statistical software SPSS24.0 was used for data processing and statistical analysis. Measurement data are expressed as mean ± standard deviation (\(\stackrel\pm s)\). Comparisons between groups were conducted using the paired t-test. Chi-squared (χ2) test was used for the comparison of count data. A difference was considered statistically significant when the p-value was less than 0.05.