Hypotension during transsphenoidal pituitary surgery associated with increase in plasma levels of brain injury markers.

Background: Patients undergoing pituitary surgery may experience short- and long-term postoperative morbidity. Intraoperative factors such as hypotension might be a contributing factor. Our aim was to investigate the association between intraoperative hypotension and postoperative plasma levels of tau, neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) as markers of perioperative brain injury.

Methods: Between June 2016 and October 2017, 35 patients from the Gothenburg Pituitary Tumor Study were included. For tau, NfL, and GFAP, concentrations were measured in plasma samples collected before and immediately following surgery, and on postoperative days 1 and 5. The difference between the highest postoperative value and the value before surgery was used for analysis (∆tau_peak , ∆NfL_peak , ∆GFAP_peak ). Intraoperative hypotension was defined as the area under the curve of an absolute threshold below 70 mmHg (AUC70) and a relative threshold below 20% (AUC20%) of the baseline mean arterial blood pressure.

Results: Plasma tau and GFAP were highest immediately following surgery and on day 1, while NfL was highest on day 5. There was a positive correlation between AUC20% and both ∆tau_peak (r²  = .20, p < .001) and ∆NfL_peak (r²  = .26, p < .001). No association was found between AUC20% and GFAP or between AUC70 and ∆tau_peak , ∆NfL_peak or ∆GFAP_peak .

Conclusion: Intraoperative relative, but not absolute, hypotension was associated with increased postoperative plasma tau and NfL concentrations. Patients undergoing pituitary surgery may be vulnerable to relative hypotension, but this needs to be validated in future prospective studies.