ObjectiveTo investigate the current status of elderly patients suffering from subsyndromal delirium (SSD) after lower extremity fracture surgery, and to analyze its influencing factors.MethodsA total of 237 elderly patients undergoing lower extremity fracture surgery were selected as the research subjects. The occurrence of SSD within 7 days after surgery was evaluated daily in patients by employing the Confusion Assessment Method (CAM) in Chinese version, and the general data, as well as clinical data in terms of preoperative fasting time, anesthesia method, operation duration, intraoperative bleeding volume, dependence degree of daily living self-care ability, preoperative Mini-Mental State Examination scale score, preoperative Self-Depression Scale (SDS) score, presence of self-controlled analgesia, etc., and blood biochemical indices (hemoglobin, albumin, K+, Na+, Cl-, and Ca2+) levels were collected in patients. The influencing factors for elderly patients suffering from SSD after lower extremity fracture surgery were analyzed by using the multivariate Logistic regression model. ResultsThe incidence rate of SSD was 52.32% among 237 elderly patients after lower extremity fracture surgery, of which 91.93% of SSD symptom appeared within 72 hours after surgery, and 42.74% of SSD patients suffered from delirium at the same time. In SSD patients simultaneously suffering from delirium, SSD symptom appeared in 32.08% of patients before the onset of delirium and eventually progressed to delirium, and SSD symptom appeared in 67.92% of patients in the intermittent stage between two episodes of delirium, or appeared after the end of delirium status. The median frequency of SSD occurred was 2 times, and the total duration was (35.89±16.78) hours. Among the 4 core delirium features of CAM in Chinese version, "change of consciousness level" most frequently occurred, accounting for 42.68%. The results of multivariate Logistic regression analysis revealed that age, preoperative SDS score, preoperative fasting time, hypocalcemia, dependence degree of daily living self-care ability, and use of self-controlled analgesia were the influencing factors for elderly patients suffering from SSD after lower extremity fracture surgery (P＜0.05). ConclusionThe incidence rate of elderly patients suffering from SSD after lower extremity fracture surgery is relatively high, the high-incidence period is within 72 hours after surgery. Older age, longer preoperative fasting time, higher dependence degree of daily living self-care ability, higher preoperative SDS score, use of self-controlled analgesia, and presence of hypocalcemia are more likely to develop SSD after lower extremity fracture surgery in elderly patients. Medical staff should conduct early evaluation and screening on these influencing factors to decrease the incidence rate of SSD, and avoid its progression to delirium.

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