In this retrospective analysis, we examined the clinical characteristics of severe encephalitis and identified baseline risks of age,respiratory failure, status epilepticus, and GCS<8. These factors were significantly associated with poor-prognostic. The age, GCS and status epilepticus were same as previous studies1. The respiratory failure has not been reported. There were 17 respiratory failures which included with 8/17(47.05%) autoimmune encephalitis, 7/17(41.17%) Japanese encephalitis,1 viral encephalitis and 1 purulent encephalitis. It has suggested that more attention should be paid to respiratory system, for patients with autoimmune encephalitis in NICU.
In this cohort, the prognostic nutritional index (PNI) was initially representing patients' immune and nutritional status about severe encephalitis. We were first investigating how immune-nutritional status influenced prognosis in encephalitis. Previous studies on PNI have identified PNI as a malnutrition predictor of poor survival in patients with various malignant and perioperative period diseases.In some neurologic disease, such as acute ischemic stroke (AIS), cognitive function impairment (CFI), the PNI score was associated with a higher risk of adverse effects. Interestingly, whether the PNI score was the marker of prognostic of infectious disease had not been widely studied.
From the pathophysiology, PNI is composed by albumin and lymphocyte. Serum albumin is not only a marker of nutrition but also an inflammatory indicator11. The Serum albumin has a long half-life, which is insensitive to acute changes in nutritional status. Consequently, the Society of Critical Care Medicine (SCCM) as well as the American Society for Parenteral and Enteral Nutrition (ASPEN) do not recommend albumin as an indicator of nutritional status in critically ill patients12. According to some studies, the low serum albumin not only indicated acute malnutrition, but also correlated with antioxidant, anti-inflammatory effects, and maintenance of homeostasis. Thus, cytokine storm, oxidative stress, blood clotting, and even organ failure may be caused by low serum albumin. In our study, the lower albumin was also related with a poor-prognostic(P<0.005). Comparing with PNI score, it was not significant in poor-prognostic. Lymphocytes are a crucial part of immune cells in body and participate in cellular immunity. Decreased lymphocytes count indicates physiological stress and poor health and many studies have shown it might be associated with poor prognosis in numerous disease such as cancer, infections, immune dysfunctions. The lymphocyte count is considered as a blood marker for malnutrition13. We also calculated the NLR, as an immune marker. As a result, the NLR and PNI were with the same trend, but NLR were less significant than PNI (P<0.010). In recent studies, the PNI was superior to the NLR as a prognostic marker in many cancer patients. Above all, Albumin and Lymphocytes are also an immune-nutrition indicator in infectious disease.
In this cohort, we first retrospectively revealed the line relationship between the PNI Score and prognosis of patients with severe encephalitis in NICU. Severe encephalitis patients were manifested as an inflammatory cascade and associated with a massive release of inflammatory cytokines that triggers systemic inflammatory reaction. As a result of inflammation, an infection can result in prolonged vasodilatation and increased capillary permeability. Blood vessel components, such as albumin, leaked into the tissue spaces, causing a decrease in plasma albumin concentration. This reflected the process of PNI to some extent. Consequently, PNI may reflect the immune and nutritional status of patients with severe encephalitis at the same time, which may explain the poor prognosis with low level of PNI.
In NICUs, we focused on high-risk patients who required clinical attention. Early sufficient nutritional support for the severe encephalitis patients may improve patients’ outcome and reduce mortality. PNI are easy to calculate and composed by albumin and lymphocytes which is facile for application.
This study, however, had some limitations. Firstly, this study is a single-center retrospective study with relatively small number of patients. We were the largest NICU in western China, so our sample was representative and convincing. Secondly, because the etiology of encephalitis was complex and difficult to identify, we did not perform an additional subgroup analysis. Differences in outcomes may be seen for patients with different kinds of encephalitis, such as infectious encephalitis and autoimmune encephalitis. Thirdly, in this study, only PNI scores obtained during the first 24 hours following a patient's admission to the NICU were included, which reflected the baseline level. It was unknown whether a dynamic change in the PNI score during NICU treatment affected the prognosis of patients. Finally, the study was observational and retrospective. It is therefore necessary to conduct a well-designed, prospective, multi-center, randomized controlled study to verify the conclusion.