Included data were extracted from our database as previous studies described. Children scheduled for elective cardiac transcatheter occlusion under general anesthesia for ventricular septal defects (VSD), atrial septal defects (ASD), and/or patent ductus arteriosus (PDA) were recruited into the study from 20th February 2019 to 19th March 2021 at the Shanghai Children’s Medical Center & National Children’s Medical Center, a tertiary hospital affiliated to Shanghai Jiao Tong University. Exclusion criteria included parents’ refusal to sign the informed consent; the American Society of Anesthesiologists physical status score ≥ Ⅳ; evidence of a recent lower respiratory tract infection (such as pneumonia and bronchitis) within the past 2 weeks; unavailable medical history (parents or legal guardian cannot recall the medical history clearly); known hypersensitivity to anesthetics; recent participation in other clinical studies; medical history of hepatic or nephritic disease or complex cyanotic heart disease; premedication (e.g., dexmedetomidine, salbutamol and midazolam); and endotracheal tube in exchange for LMA due to dissatisfactory ventilation.
After children entered the operating room, routine monitoring including electrocardiography, noninvasive blood pressure monitoring, and pulse oxygen saturation measurement were conducted. Anesthetics such as propofol (3-4 mg·kg−1) and sufentanil (0.1-0.2 µg·kg−1) were used for the induction of anesthesia and were administered through the peripheral vein. Appropriate LMA was inserted while the child was unconscious. Sevoflurane 1-1.2 MAC with the mixture of oxygen and air (50:50) was inhaled to maintain the depth of anesthesia depending on the heart rate and blood pressure. Crystalloid fluid was infused following the 4-2-1 rule. The LMAs were removed while the children were still anaesthetized (regular breathing, end-tidal sevoflurane level: 0.8 MAC). The anesthesiologist in charge was blinded to the patient’s URI history.
All CHD children were divided into two groups, the COVID-19 period spanning March 2020 to March 2021 and non-pandemic period considered from February 2019 to January 2020 due to January 23rd being the date when Wuhan declared strict anti-pandemic measures which would cause changes in behavior.
Before surgery, the parents or legal guardians of all children were visited by a senior resident anesthesiologist with at least three years anesthesia experience and the parents/guardians were asked to fill out a questionnaire form. The questionnaire included questions concerning patient’s demographic information (age, sex, weight, and height), type of CHD, history of asthma and passive smoking, presence of URI symptoms, and the exact time of URI occurrence. Patient who presented with any two of the following URI symptoms, as confirmed by the parent or legal guardian, over the last the two weeks were considered to have a history of URI: nasal congestion, rhinorrhea, dry or moist cough, sore throat, sneezing, or fever >38°C.
PRAEs (laryngospasm, bronchospasm, coughing, airway secretion, airway obstruction, and oxygen desaturation) as well as details of anesthesia management were recorded. Adverse respiratory events were defined as any episode of perioperative airway obstruction (snoring or requirement of intervention with a decrease in SpO2 after inhalation of room air; interventions included repositioning/neck roll, jaw thrust/ chin lift, and oral airway), laryngospasm (partial or complete airway obstruction associated with muscle rigidity of the abdominal and chest walls), bronchospasm (increased respiratory effort, especially during expiration; wheezing on auscultation), oxygen desaturation less than 95% (for ≥10s), breath holding (≥15s), severe coughing (a series of pronounced, persistent, severe coughs lasting more than 10s), and increased airway/oral secretion (≥one suction). Intraoperative observation and postoperative visit were completed by a researcher in our study team who was also the qualified anesthesiologist. If a laryngospasm occurred, children were treated with positive airway pressure combined with increased anesthetic levels; some patients required the administration of succinylcholine. In cases where bronchospasm occurred, children were treated with nebulized albuterol using a metered-dose inhaler.
According to our previous studies[12, 23], the incidence of PRAEs in CHD children without recent URI was 37.7% (95%CI 35.3–40.2%) during the non-COVID-19 pandemic period. We assumed the incidence of PRAEs in the same population decreased by a half in 2020 (COVID-19 period). 114 children in each period were required with a power of 90% and a significance level of 0.05. Accounting for the 10% dropouts of samples, 125 patients per group were required.
Normality testing was conducted using the Shapiro-Wilk test. Numerous variables were presented as mean and standard deviation (SD), and categorical data as absolute numbers and percentages. Differences between groups were determined using the Student’s t-test for numerous variables and the χ2 test or Fisher exact test for categorical variables. Logistic regression model measured the association between behavior changes during the pandemic and PRAEs. The results were presented as odds ratios (OR) and 95% confidence intervals (CI). For all tests, a two-sided value of P value <0.05 was considered significant. Statistical analyses were performed using IBM SPSS statistics for Windows, Version 26.0 (IBM corp., Armonk, NY, USA).