The incidence of pulmonary infection in elderly patients with hip fractures after surgery differs in regions with different economic levels[12], but the overall incidence is still relatively high, which is worthy of attention. In addition, postoperative lung infection will further increase the risk of death in such patients[13]. Studies[14, 15] have shown that lung infection is an independent risk factor for death after hip fracture in the elderly. Previous study[16] has found that 14% of elderly hip fracture patients with lung infections died within 30 days, while the case fatality rate of patients with non-pulmonary infections is only 1.7% within 30 days. Another study[17] has showed that the risk of death for patients with pulmonary infection after hip fracture is 7.36 times higher than that of patients without lung infection after surgery. Therefore, the prevention of pulmonary infection should be strengthened clinically in order to reduce the complications and mortality. The results of this study have found that the incidence of pulmonary infection in patients with hip fracture is 13.11%, which is similiar to previous reports[18, 19]. And we have found that age ≥ 70y, diabetes mellitus, anemia, hypoalbuminemia, general anesthesia, duration of surgery ≥ 120min were the risk factors of pulmonary infection in elderly patients with hip fracture, early intervention targeted on those influencing factors should be taken to reduce the development of postoperative pulmonary infections.
Regarding the influence of age on postoperative pulmonary infections in elderly patients with hip fractures, many studies[20, 21] have reached different conclusions. A study[22] has reviewed 1,429 patients undergoing hip fracture surgery, and the results have showed that the higher the age, the greater the probability of postoperative lung infections. This may be because elderly patients have more underlying diseases and the body’s immune function is reduced, which is extremely easy under the invasion of pathogenic bacteria, combined with fracture trauma, surgical stress, and long-term bed rest caused a further decline in immunity, which induced pulmonary infection[23–25]. However, some studies[26–28] have pointed out that the occurrence of postoperative lung infections should be attributed to the increase in the number of comorbidities that accompany age, rather than age itself. However, it is currently recognized that the incidence of hip fractures in elderly patients increases with age, and surgery is the current main treatment method. Therefore, surgery cannot be given up on the grounds of advanced age, and other controllable patients should be evaluated. For patients with more risk factors, we should adopt targeted interventions to reduce the risks of postoperative pulmonary infections.
Malnutrition has been proven to be one of the important risk factors for postoperative pulmonary infection in elderly patients with hip fracture. In addition to low BMI, serum albumin is also an important indicator of nutritional status[29]. Studies[30, 31] have pointed out that low serum albumin levels increase the risk of pneumonia, because wounds, fracture healing, and muscle strength recovery require a large amount of protein supplementation. When protein is insufficient, muscle strength and limb function decline, causing the prolonging duration of bed time[32]. Besides, some patients are in a state of malnutrition when they are admitted to the hospital, coupled with increased catabolism caused by trauma and surgery, and increased demand for nutrients, resulting in a further sharp decline in nutritional status, weakened immunity, and increased risk of pulmonary infection[33]. Therefore, elderly patients with hip fractures should be screened for nutrition before surgery, and nutritional support interventions should be implemented before surgery to reduce the risk of pulmonary infections due to malnutrition.
Diabetes may be one of the risk factors for postoperative lung infection in elderly patients with hip fracture. Some studies[34, 35] have found that patients with diabetes before surgery are prone to pulmonary infection after surgery, which is consistent with the results of this study. However, some studies[36, 37] have pointed out that diabetes has nothing to do with the occurrence of postoperative lung infections in elderly patients with hip fractures. Study[38] has reported that when the patient's blood glucose is > 200 mg/dL, it will increase the incidence of pneumonia. Diabetes may be associated with postoperative lung infections in elderly patients with hip fractures, but this relationship may only exists when blood sugar is high[39]. The reason may be that when the blood sugar of diabetic patients is too high, the plasma osmotic pressure will also increase, which inhibits the phagocytic ability of immune cells in the blood and is prone to infection[40, 41]. However, due to the small sample size of related studies, there may be biases in the results. Further researches are needed to confirm the role of diabetes in the future.
Studies[42, 43] have reported that the longer duration of surgery is an important risk factor for postoperative pulmonary infection in elderly patients with hip fractures, which is more consistent with the results of this study. The prolonged operation time may be caused by a variety of factors, such as severe osteoporosis and complex fracture morphology[44]. The prolongation of the operation time can lead to an increase in blood loss during the operation, and the prolongation of the patient's intraoperative hypothermia time, resulting in a decrease in their resistance, thereby increasing the postoperative pulmonary infection[45]. In addition, during general anesthesia surgery, the cough reflex is suppressed, and prolonged surgery leads to rapid proliferation of lower respiratory tract bacteria, which may lead to the occurrence of pneumonia[46]. Therefore, medical staff should shorten the operation time as much as possible, and pay attention to monitoring the patient's body temperature and keep warm during the operation.
At present, many scholars[47, 48] believe that general anesthesia is related to the occurrence of pulmonary infections after surgery. Because local anesthesia does not affect the patient's spontaneous breathing, does not inhibit the protective cough reflex, and at the same time avoids tracheal intubation, thus reducing the risk of postoperative pulmonary infection. But the shortcoming of the study is that doctors are more inclined to adopt general anesthesia for patients with more severe illness, which may cause selection bias. In addition, it’s been reported[49] that the incidence of pulmonary infection after local anesthesia is lower than that of patients under general anesthesia. However, when subgroup analysis is performed, only in patients with femoral intertrochanteric fractures, the difference in the results of the study is statistically significant, while in the femoral neck There is no such trend among fracture patients. However, the specific reasons are not clear, and further studies are needed in the future. Furthermore, this study has found that the bacteria in lung infections are mainly gram-negative bacteria. This result suggests that the detection of pathogenic bacteria should also be paid attention to in actual clinical treatment, and reasonable antimicrobial treatment should be selected in combination with patient drug sensitivity test to improve anti-infection effects.