Elevated Substance P Is a Risk Factor for Postoperative Delirium in Patients with Hip Fracture

Hip fractures are quite common worldwide, especially among the elderly, and are associated with a high incidence of postoperative delirium, which worsens functional results and increases death. The causes of postoperative delirium in patients with hip fractures are unknown, and a separate pathobiology has been hypothesized. Substance P is a neuropeptide that has been linked to a number of immune-inflammatory and neurological conditions. The purpose of this study was to see if serum substance P levels could predict postoperative delirium in a group of hip fracture patients.

A total of 148 hip fracture patients were enrolled in the study, all of whom had no substantial pre-existing medical or cognitive issues. Demographic and regular laboratory data were gathered as a starting point. ELISA was used to examine substance P levels before and after surgery (after 1 day). Patients were then divided into two groups: "postoperative delirium" and "no postoperative delirium." Intergroup comparisons, study of delirium prevalence rates in postoperative serum substance P quartile categories, and binary logistic regression for postoperative delirium category as outcome were all done.

Except for serum low-density lipoprotein (LDL) levels, there were no statistically significant variations in preoperative substance P levels or other baseline characteristics between the two groups. The "postoperative delirium" group had significantly higher postoperative substance P levels than the "no postoperative delirium" group (46.36.1 versus 31.94.7 pg/ml). There was a significant difference in postoperative delirium rates between the quartile categories of postoperative substance P, with the fourth quartile having the highest rate. Regression analysis revealed that postoperative substance P levels were related with a significantly increased OR (1.265, CI: 1.172-1.283) of postoperative delirium.

In the current sample of hip fracture patients, a higher postoperative serum substance P level was linked to a higher risk of postoperative delirium. Further research into the utility of early postoperative serum substance P as a delirium indicator in hip fracture patients is needed.