This study shows the predictive value of various preoperative and intraoperative risk factors for the occurrence of delirium after amputation surgery and establishes a nomogram. The incidence of postoperative delirium varies with the type of surgery, and several past publications have shown that the incidence of postoperative delirium in amputation patients is significantly higher than in other vascular surgical procedures and serves as an independent risk factor for postoperative delirium. .Through literature search, it is found that there are a few articles on various causes of postoperative delirium in amputated patients, so we separately study the postoperative delirium in amputated patients.
In this retrospective article, the incidence of delirium after amputation was 38.3%. The independent risk factors of postoperative delirium were determined by age, Barthel grade, entry into ICU and low serum albumin after operation. The nomogram is established according to four independent risk factors, and the test shows that the prediction effect of the model is good. The prognosis of patients with postoperative delirium is worse, and the occurrence of delirium indicates longer hospitalization time and higher hospitalization cost.
In our study, age was an independent risk factor for postoperative delirium, as has been previously reported in several papers 。Although a single factor can lead to delirium, usually delirium in the elderly is multifactorial 。Older patients are thought to be more susceptible to the reduced reserve capacity of the brain in the elderly and the gradual accumulation of permanent damage to neurons, dendrites, receptors and microglia,because of the link between aging and impaired physiological compensatory capacity to adapt to the physical stress of surgery when these patients already have coexisting conditions 。Older patients are more vulnerable and present with more susceptibility factors compared to younger patients, and are more likely to suffer postoperative delirium with the same predisposing factors.
Barthel Index is also an independent risk factor for delirium. The Barthel Index is divided into 4 levels, which represent the patient's ability to take care of himself/herself in daily life。However, no significant correlation was found in the shin.et al article, possibly due to differences in the assessment tools used. When patients live their lives only through the help of others and lack autonomy. Especially in amputated patients, leg amputation leads to a reduced range of motion, confining the patient to the bed most of the time and diminished spatial perception. Patients with arm amputation have a reduced ability to take care of themselves and lose their basic life skills, especially in the short time after amputation, they are still unable to adapt to the way of life in the amputation state, which will increase the incidence of delirium。
Postoperative admission to ICU was the most significant independent risk factor in our study. Postoperative admission to ICU or not was done only after a systemic assessment. It represents a poorer current condition of the patient. However, the question of whether the ICU environment contributes to increased delirium risk in patients was not clarified in our study. Insomnia and constant exposure to light and noise are among the stressors for patients。Current guidelines suggest that , where possible, patients are given space and time for recognition and early access to their own families whenever possible. In the ICU environment, the inability to recognize day from night, disorientation and disturbance of the sleep-wake cycle, and the inability of family members accompany may lead to the occurrence of delirium.
Postoperative albumin is an independent risk factor for delirium after major limb amputation. The relationship between albumin levels and the development of postoperative delirium has been reported in different surgical populations. In a cohort study of elderly patients admitted to ICU for non-cardiac surgery, Dan-Fengzhang et al.  pointed out that lower albumin levels have a higher risk of delirium. Albumin has been hypothesized to be an overall biomarker of frailty and nutritional and functional abilities. Weaker patients are more likely to develop delirium. At present, the pathophysiological mechanism of delirium caused by hypoalbuminemia is not clear. The possible reason is that it affects the metabolism of drugs and toxins, because albumin is the main transporter in plasma. The mechanism needs to be further studied.
Other factors are currently the subject of different conclusions in literatures. Different literatures still dispute whether postoperative infection is a risk factor for delirium.The pathophysiology of delirium remains incompletely elucidated, and given the complex multifactorial causes of delirium, each individual episode may have a unique set of component contributors; each group represents a discrete yet sufficient causal mechanism. Thus, a single cause or mechanism for psychosis may not be found。The systemic inflammatory response to sepsis can lead to a cascade of local (brain) neuroin flammation triggered by inflammatory cytokines, resulting in endothelial activation, impaired blood flow, and neuronal apoptosis. Neurological injury can lead to excessive microglia activation, resulting in a neurotoxic response and further damage to neurons。In the present study, the indicator of infection was bacterial culture results, and infection was a potential factor for delirium in the univariate analysis, but in the multifactorial analysis, the infection factor was corrected. Different literature gives contrasting conclusions as to whether the type of anesthesia is a risk factor for delirium.louis de Jong et al.found that the type of anesthesia was not associated with the occurrence of delirium. Shin et al. et al. found that ASA classification was not associated with delirium, but our study found that high ASA score was a risk factor for delirium in univariate analysis.
There are still some limitations of this study: firstly, this study is a retrospective chart- controlled study, which cannot fully ensure the credibility of all information, which may cause bias in the results to some extent; secondly, we used different diagnostic tools in assessing delirium in ICU wards and general wards, which may cause bias in the diagnosis of delirium; finally, the number of cases included in this study is small, and further validation of the model effect is needed at a later stage.