Reduction in the duration of postoperative fever following NUSS surgery during the COVID-19 pandemic

Pectus excavatum (PE) is the most common congenital birth defect of the chest wall that often causes psychological and social issues [1], limited exercise capacity [2], and even decreased sleep quality. PE occurs in 1 out of every 400–1000 births. The first reports of corrective surgery to fix PE date back a century, as Meyer and colleagues first reported the surgical treatment of PE in 1911 [3]. Currently, the most accepted means of correcting PE is through minimally invasive surgical repair (NUSS procedure) [4]. Importantly, postoperative fever is a common symptom in the early postoperative period following NUSS. Fever onset may be caused by metal allergies [5], hematoma absorption, transfusion reactions, or result from unknown origins. Clinically, fever is one of the common postoperative symptoms and does not seem to be significantly associated with serious complications. As such, fever has not received much attention. When the first case of pneumonia of unknown cause was reported on 8 December 2019 in Wuhan, China [6], within one month, the Chinese Center for Disease Control and Prevention had successfully isolated and named the novel strain of coronavirus, and by 7 January 2020, the National Health Commission (NHC) had issued guidelines for epidemic prevention and control. To prevent COVID-19 in public, several prevention tools, such as use of surgical masks and filtering facepiece respirators (FFRs), were introduced into daily clinical practice [7]. Meanwhile, for high-risk occupational exposure groups, such as hospital workers, the NHC recommended that doctors and nurses should wear overalls, work hats, and medical-grade surgical masks. In addition, relatives of patients were limited or forbidden to visit inpatient departments. During this time period, our cardio-thoracic surgery department observed an empirical decrease in the incidence of post-operative fever in patients admitted for PE.

As the duration of the surgical procedure, protocols for prophylactic administration of antibiotics, and other possible causes related to postoperative fever were all the same, we hypothesized that the lower incidence of postoperative fever in Group 2021 was related to the increased precautions used during hospitalization in the early period of COVID-19, specifically, the use of personal protective equipment (PPE) and no external visits to the hospital.

The aim of this study was to compare the incidence of postoperative fever during the COVID-19 pandemic (January 1, 2020 to March 1, 2021) (Group 2021) to that of the preceding non-pandemic period (January 1, 2017 to March 1, 2019) (Group 2019).

Data from a total of 284 patients, consisting of 200 males and 84 females with an average age of 9.73 ± 3.41 (range, 4 to 17) years, were collected. 144 patients were allocated into Group 2019, with an average age of 10 years (range 6 to 13) and a mean BMI of 15.68 ± 2.46 kg/m². Alternatively, 140 patients were allocated into Group 2021, with an average age of 11 years (range 8 to 13) and a mean BMI of 16.25 ± 12.92 kg/m². Age and BMI were similar between the two groups (p > 0.05) (Table 1). The duration of the surgical procedure, as well as mechanical ventilator and urinary catheter use were also no difference between the two groups (p > 0.05) (Table 1). Contrastingly, the prevalence of postoperative fever 72 h after surgery in Group 2021 was significantly lower than Group 2019 (7% vs. 31%, p < 0.001)(Fig. 1). In Group 2021, fever was observed in the first 24 h post-surgery in 11 (7%) patients, which was also the percentage observed 72 h after surgery. In Group 2019, fever was observed in the first 24 h post-surgery in 35 (23%) patients, which increased to 47 (31%) patients after 72 h. In addition, the peak postoperative fever temperature recorderd at 72 h was also significantly higher in Group 2019 (p < 0.05) (Table 1). Accordingly, the length of hospitalization in Group 2021 was also significantly shorter than that of Group 2019 (p < 0.05) (Table 1). We also observed a statistically significant difference in the level of WBC between the two groups at 24 h after surgery (p < 0.05) (Table 1). However, no statistical difference were observed in CRP level or the incidence of postoperative complications between the two groups (p > 0.05) (Table 1).

Our study shows a significant decrease in the post-operative fever of patients in Group 2021 compared to Group 2019 (7% vs. 31%, p < 0.001). Furthermore, we observed a reduction in the postoperative fever temperature (degree of fever ≥ 38.0℃) in Group 2021 (3% in Group 2021 vs. 11% in Group 2019, p < 0.05). Meanwhile, we also observed a statically significant difference in postoperative WBC count between the two groups, while CRP levels remained unchanged. Interestingly, we observed that infection-related complications did not decrease with the declining fever rate, possibly because the complication rate after surgery was very low. During the entire observation period, only 1 in 284 patients was found to have poor wound healing (a small amount of pink exudation), and the wound became better after daily dressing changes and systemic prophylactic antibiotic therapy. Data in the literature indicate that the incidence of wound healing after NUSS surgery is 1.5–6.9% [8]. During the COVID-19 epidemic, where the prevalence of postoperartive fever decreased significantly within 72 h post-surgery, we were unable to observe any decrease in the incidence of complications, although the hospital stay was significantly shortened, resulting in lower healthcare costs.

Fever is a common complication in the early stages following the NUSS procedure, and fever is often associated with infection-related complications. We hypothesize that the decline in the frequency of postoperative fever observed during the epidemic was most likely related to the strengthening of personal protection measures for physicians, nurses, patients, and family members, including implementation of surgical masks, FFRs, and limiting the number of relatives allowed into inpatient departments, thus reducing the risk of pathogen exposure [9‐11]. However, due to our failure to perform preoperative and postoperative respiratory tract or blood tract tests on patients with PE, we were unable to objectively obtain evidence of pathogen transmission. Wilder et al [12]found that during the COVID-19 epidemic, pediatric hospitalization rates for virus-related acute diseases (such as asthma, bronchitis, and pneumonia) decreased, suggesting that measures such as wearing surgical masks can reduce the spread of the virus significantly. According to statistics, the frequency of postoperative fever ranges from 18 to 60%. Since fever is a common symptom after surgical procedures, it previously did not garner much attention. However, since the COVID-19 epidemic, fever has become one of the more frequent screening factors to identify viral infections, which has significantly increased fever awareness [13], and the correlation between fever temperature and the prognosis of viral infections has been reported in a few studies. In addition, we accept that fever can reflect the presence of an inflammatory reaction in the body, however, fever may not be related to the severity of inflammation. We routinely tested serum from the two groups at the same time and significant differences were only found in the WBC count, but not CRP levels. Thus, it is difficult to conclude that fever is associated with the degree of inflammation.

Furthermore, while BMI was not significantly different between the two groups (p > 0.05), the BMI of both groups was lower than the normal range, with some of the patients being severely underweight. This supports the notion that PE is more likely to occur in thin children, which has been reported previously [14]. Therefore, adolescents should be encouraged to eat a balanced diet, strengthen their exercise routine, and enhance their physical fitness.

As the present study was limited to PE patients, additional surgery types have not yet been investigated, which makes it impossible to as of yet infer the broader implications of the observed postoperative fever phenomenon that arose during the COVID-19 epidemic. Interestingly, a previous clinical study carried out in another single center also found a decrease in the postoperative fever rate [15]. In this study by Mastri and colleagues, they showed that the other observation objects were not involved in the NUSS postoperative group. Thus, this study provides more convincing evidence for the phenomenon we have observed. However, further studies with larger cohorts at multiple clinical research centers is required for subsequent validation of our results.

In the early stages of the COVID-19 epidemic, the absence of rapid and precise screening tests for COVID-19 significantly increased concern regarding clinical symptoms such as fever and cough. However, this troublesome situation led to stronger measures to prevent respiratory infections (surgical masks and FFRs), also reducing the spread of the virus to the public. As for PE patients, there was a significant decrease in the prevalence of postoperative fever and the length of hospitalization, further decreasing the overall economic cost.