Effect of Temperature Maintenance by Forced-Air Warming Blankets of Different Temperatures on Changes in Inflammatory Factors in Children Undergoing Congenital Hip Dislocation Surgery
Hypothermia, defined as a core temperature below 36.7°C, is a common complication during the peri-operative period, particularly in infants and young children. It can result from factors such as large surgical wounds, significant blood loss, prolonged operative times, anesthesia-induced thermoregulation disruption, and the use of low-temperature fluids. Hypothermia is associated with numerous adverse clinical outcomes, including infections, cardiovascular complications, prolonged hospital stays, metabolic dysfunction, and even death. Therefore, identifying effective and safe methods to prevent peri-operative hypothermia and its associated complications in pediatric patients is crucial.
Developmental displacement of the hip (DDH) is a common pediatric malformation characterized by the displacement of the femoral head. Orthopedic surgery is a standard and effective treatment for DDH in infants and young children. However, pediatric patients undergoing DDH surgery are particularly susceptible to peri-operative hypothermia due to the extensive surgical wounds and prolonged operative times. Forced-air warming is recognized as one of the most effective intra-operative thermal insulation methods to prevent peri-operative hypothermia. While the recommended temperature range for adult patients is 32 to 38°C, few studies have investigated the efficacy of forced-air warming at different temperatures in pediatric patients undergoing surgery for congenital hip dislocation.
Additionally, appropriate peri-operative thermal insulation has been reported to effectively inhibit systemic inflammatory responses in children. Previous studies have shown that intra-operative thermal insulation can suppress stress-induced inflammation, thereby improving a child’s prognosis. Furthermore, changes in body temperature can influence the activation of the transforming growth factor-beta (TGF-β) signaling pathway, an anti-inflammatory cytokine pathway that regulates cell growth and differentiation. However, the effect of the temperature setting of forced-air warming devices on the levels of TGF-β and other inflammatory factors remains unclear.
This study aimed to determine the effect of forced-air warming blankets set at different temperatures on changes in body temperature and serum levels of TGF-β and other inflammatory factors in pediatric patients undergoing surgical correction of congenital hip dislocation.
The study included 123 children aged 2 to 7 years who underwent orthopedic surgery for DDH under general anesthesia. The patients were randomly assigned to three groups using a random number table: the 32°C group (n=42), the 38°C group (n=42), and the 43°C group (n=39). The intra-operative body temperature of patients in each group was maintained using a disposable aseptic air heating blanket set to the respective temperature. The heating blanket covered the entire body except for the operative site. The operating room temperature was maintained at 23°C with a relative humidity of 40% to 50% to prevent environmental influences on body temperature.
Anesthesia was induced with intravenous injections of fentanyl, propofol, and rocuronium. After successful intubation, the endotracheal tube was connected to the anesthesia machine for mechanical ventilation. Central venous catheterization was performed through the right jugular vein for hydration and monitoring of venous pressure. Anesthesia was maintained using inhalation of 1.5% to 2.5% sevoflurane, intravenous injection of remifentanil, and intermittent intravenous injection of vecuronium bromide for muscle relaxation. The anesthesia depth was maintained between 40 and 60 during the operation, and respiratory parameters were adjusted to maintain end-tidal carbon dioxide (ETCO2) at 35 to 45 cm H2O. Real-time monitoring of direct arterial pressure and heart rate was performed to maintain heart rate and blood pressure within 30% of baseline values.
Body temperature was recorded at multiple time points: immediately after anesthesia induction and intubation (T0), at initial incision (T1), at 1 hour after incision (T2), at 2 hours after incision (T3), at the end of surgery (T4), immediately upon return to the ward after surgery (T5), and then at 12 hours (T6), 24 hours (T7), 36 hours (T8), and 48 hours (T9) after surgery. A body temperature probe was placed in the esophagus to measure body temperature. The operative time, intra-operative blood loss, and intra-operative infusion volume were recorded during surgery. Post-operative fever (defined by axillary temperature above 37.4°C and fluctuation greater than 1°C within 1 day), hospitalization days, and wound infection (defined by the presence of exudation, rupture, and suppuration of the incision under direct vision during dressing change) were noted.
Venous blood samples were taken at T0 and T4 to measure serum levels of TGF-β, tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), and interleukin-10 (IL-10). TGF-β levels were determined using Western blotting, while TNF-α, IL-1β, and IL-10 levels were measured using enzyme-linked immunosorbent assay (ELISA).
The clinical characteristics of patients in the three groups, including age, body weight, gender ratio, operative time, intra-operative blood loss, intra-operative rehydration, post-operative hospitalization days, and wound infection, were similar. However, the number of patients with fever in the 38°C group was significantly lower than in the 32°C and 43°C groups.
Body temperature was significantly higher in the 38°C and 43°C groups compared to the 32°C group at T0. At T2, the body temperature was significantly higher in the 43°C group than in the 32°C and 38°C groups. At T4, the body temperature appeared higher in the 38°C group than in the 32°C and 43°C groups, although the difference was not statistically significant. Body temperature remained stable within the normal range in all groups throughout the operation and post-operative period.
At T0, there were no significant differences in serum levels of TGF-β, TNF-α, IL-1β, and IL-10 among the three groups. However, at T4, the serum levels of TGF-β and IL-10 were significantly increased in the 38°C group, while the serum levels of TNF-α and IL-1β were significantly decreased in the 38°C group compared to the 32°C and 43°C groups.
The findings of this study suggest that forced-air warming blankets set at 38°C are most effective in maintaining stable body temperature with fewer adverse post-operative outcomes in pediatric patients undergoing surgery for DDH. The 38°C temperature setting was associated with increased serum levels of anti-inflammatory cytokines (TGF-β and IL-10) and decreased serum levels of pro-inflammatory cytokines (TNF-α and IL-1β), indicating an anti-inflammatory effect.
The study highlights the importance of maintaining a stable body temperature during surgery to reduce the risk of hypothermia and its associated complications. The 38°C temperature setting for forced-air warming blankets appears to provide the optimal balance, promoting anti-inflammatory responses and reducing post-operative fever. This temperature is closest to a child’s physiologic temperature, resulting in balanced metabolism and activation of TGF-β.
In conclusion, forced-air warming blankets set at 38°C effectively maintain stable body temperature, reduce adverse outcomes, and inhibit inflammatory responses in pediatric patients undergoing surgery for congenital hip dislocation. This temperature setting should be considered the standard for preventing peri-operative hypothermia and improving post-operative recovery in pediatric surgical patients.
doi.org/10.1097/CM9.0000000000000846
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