Association of nociception index with postoperative immune status: a prospective observational study

Purpose

Electroencephalography (EEG) is commonly used to assess sedation levels in general anesthesia, but its ability to indicate perioperative trauma and inflammation activation levels remains unclear. This study examines the relationship between the nociception index (NOX), an EEG-derived metric, and related immune changes in surgical patients.

Methods

Patients aged 18 to 75 years scheduled for elective surgery under general anesthesia, without chronic pain, hepatic or renal dysfunction, pregnancy, intensive care unit stay, and a postoperative stay of less than 1 day. We investigated the relationship between the NOX and immune-inflammatory parameters in surgical patients. NOX and bispectral index (BIS) values were recorded upon post-anesthesia care unit admission and after awakening from anesthesia. We collected immune-related indicators, including immune cell counts in routine blood tests, C-reactive protein (CRP) levels, hemoglobin, and the length of postoperative hospital stay. The association of NOX with inflammatory response from surgical stimulation and postoperative prognosis was assessed.

Results

A total of 100 patients were included in the analysis. NOX value is positively associated with immune-inflammatory parameters, such as the postoperative CRP level (R = 0.3313, P = 0.0002), changes in monocyte counts (R = 0.3078, P = 0.0009), and changes in hemoglobin (R = 0.4036, P < 0.0001) before and one day after surgery, whereas the BISpro index is not associated with these parameters (All P > 0.05). In comparison to patients with NOX values lower than the BISpro values, patients with NOX values exceeding BISpro levels showed elevated levels of immune-related indicators, such as CRP level (P = 0.0182), monocyte count (P = 0.0357), and changes in hemoglobin before and one day after surgery (P = 0.0234). The variation of NOX (△NOX) negatively correlates with the CRP level (R = –0.2708, P = 0.0073), changes in monocyte numbers (R = –0.3606, P = 0.0002), changes in hemoglobin (R = –0.3083, P < 0.0001), and postoperative hospital stay (R = –0.1882, P = 0.0327).

Conclusions

Our study demonstrates that, as an EEG index, NOX and its dynamic variation may be associated with the inflammatory response induced by surgical trauma, potentially offering insights into postoperative immune status.

Trial registration

Registered at the Chinese Clinical Trial Registry (ChiCTR, https://www.chictr.org.cn/showproj.html?proj=199672) with No. ChiCTR2300074319.