Patients undergoing cranial neurosurgery face a high-risk postoperative period, particularly during emergence from anesthesia and early recovery in the post-anesthesia care unit (PACU). Standard monitoring provides limited insight into brain and autonomic recovery processes. Heart rate variability (HRV) and processed electroencephalography (pEEG) may offer complementary markers of autonomic and cortical function, with potential to improve early detection of complications and guide individualized care.
Adult patients (≥18 years) scheduled for elective cranial neurosurgery.
Planned extubation in the PACU after surgery.
Ability to obtain high-quality ECG and EEG recordings intra- and postoperatively (≥60 min expected PACU monitoring).
Written informed consent signed preoperatively.
Pre-existing severe cardiac arrhythmias (e.g., atrial fibrillation, frequent ectopy) or pacemaker dependence.
Known severe autonomic neuropathy (e.g., advanced diabetes, Parkinson's disease with autonomic failure).
Preoperative conditions associated with abnormal EEG (status epilepticus, uncontrolled seizures, sedative/hypnotic overdose).
Intraoperative or immediate postoperative events necessitating continued mechanical ventilation or ICU admission (e.g., massive bleeding, intraoperative arrest).
Elective Cranial Neruosurgical Patients with planned extubation in the Post-Anesthesia Care Unit (PACU)
Cohort
Prospective
Not listed
Temporal trajectories of HRV and pEEG after Neurosurgery in the PACU
Quantitative assessment of autonomic and cortical recovery during the entire period of PACU staying until 120 minutes after extubation or PACU discharge 1. Heart Rate Variability (HRV) parameters derived from continuous ECG recording, including: Time-domain indices: RMSSD (ms) SDNN (ms) Frequency-domain indices: LF power (ms²) HF power (ms²) LF/HF ratio (dimensionless) HRV will be calculated from high-resolution ECG signals using validated software following international standards (Task Force of the European Society of Cardiology and North American Society of Pacing and Electrophysiology). 2. Processed EEG (pEEG) parameters obtained from a commercial depth-of-anesthesia monitor, including: Processed EEG index value (dimensionless scale, 0-100) Spectral edge frequency (Hz) Relative alpha and delta power (% of total EEG power) Measurements will be extracted in predefined 5-minute epochs during of PACU monitoring
Correlation Between HRV/pEEG Parameters in PACU and Incidence of Early Postoperative Complications Within 48 Hours
Association between HRV and pEEG parameters (RMSSD, SDNN, LF/HF ratio, pEEG index, spectral edge frequency) measured during the first 60 minutes in PACU and the occurrence of predefined postoperative complications within 48 hours. Postoperative complications will include: * Intracranial hemorrhage * Cerebral edema * Hydrocephalus * Ischemic events * Delirium * Reintubation * Unplanned ICU admission Complications will be recorded as a binary variable (presence/absence). The strength of association will be quantified using: * Odds Ratios (OR) from multivariable logistic regression models * Area Under the Receiver Operating Characteristic Curve (AUC) Unit of Measure: * Incidence (% of patients with complication) * Odds ratio (dimensionless) * AUC (0-1 scale)
Correlation Between HRV/pEEG Parameters and Perioperative Drug Exposure
Correlation between HRV/pEEG parameters measured in PACU and intraoperative anesthetic and opioid exposure including: * Total propofol dose (mg) * Total remifentanil dose (µg) * Effect-site concentration at end of surgery (µg/mL or ng/mL) The relationship will be quantified using: * Pearson or Spearman correlation coefficients (r) * Multivariable linear regression coefficients (β) Unit of Measure: * Drug dose (mg, µg) * Effect-site concentration (µg/mL or ng/mL) * Correlation coefficient (r, -1 to +1)
Correlation Between HRV/pEEG Parameters and Perioperative Clinical Variables
Correlation between PACU HRV/pEEG parameters and: * Duration of surgery (minutes) * Intraoperative hypotension duration (minutes below MAP threshold) * Estimated blood loss (mL) * ASA physical status classification Association will be assessed using: * Pearson/Spearman correlation * Multivariable regression models Unit of Measure: * Minutes * mL * ASA class (categorical scale) * Correlation coefficient (r)
Feasibility and Data Quality of HRV and pEEG Monitoring in PACU
Assessment of feasibility and signal quality of ECG and pEEG recordings during PACU monitoring, including: * Percentage of analyzable ECG epochs (%) * Percentage of analyzable EEG epochs (%) * Artifact burden (% of recording time excluded) Unit of Measure: Percentage (%)
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