Orexin concentrations and diurnal variation in the cerebrospinal fluid of intensive care unit patients undergoing aortic surgery with spinal drainage.

Background: Cerebrospinal fluid (CSF) levels of orexin show a cyclic diurnal variation in healthy subjects, which is diminished in patients with certain diseases. However, possible circadian variations in orexin levels in critically ill patients remain unknown. In this study, we evaluated the orexin concentrations in the CSF and their diurnal variation in patients undergoing thoracic aortic aneurysm repair with lumbar intrathecal catheterization for CSF drainage after non-neurosurgery.

Methods: Eligible patients with a lumbar intrathecal catheter placed for CSF drainage following aortic surgery at a single-center ICU between September 2019 and February 2020 were included. Catheters were placed before anesthesia induction, and CSF was collected at the time of catheter placement, ICU admission, and daily at 6:00, 12:00, 18:00, and 24:00 until the catheter was removed or for up to 5 days after admission to the ICU.

Results: Three patients (Patients A, B, and C) who underwent thoracic aortic aneurysm repair were included. Patients B and C received sedatives or hypnotics during the orexin measurement period. The baseline orexin levels for Patients A, B, and C were 219.9, 312.3, and 403.8 pg/mL, while the mean orexin levels were 319.4 ± 82.6, 372.4 ± 56.0, and 306.3 ± 48.3 pg/mL, respectively. For all three patients, orexin levels showed diurnal variations, but no consistent periodic changes.

Conclusion: CSF orexin concentrations for patients undergoing thoracic aortic aneurysm repair in the ICU were within the reported range compared to those of previously reported healthy subjects; however, consistent periodic diurnal variations were not observed.