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NCT Number: NCT07443072

Heart Rate Variability and Processed EEG Features as Predictors of Postoperative Outcomes After Cranial Neurosurgery

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.

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Key information

Conditions

Cranial Neurosurgery

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

About this study

Patients undergoing cranial neurosurgery face a particularly vulnerable postoperative course. The immediate hours after surgery represent a high-risk window, as the transition from anesthesia to recovery is marked by abrupt physiological shifts and the potential for neurological or systemic instability. As patients transition from deep anesthesia to consciousness, dynamic fluctuations in autonomic tone and cortical activity reflect the brain's ability to recover from surgical and anesthetic stress. Smooth emergence and extubation are therefore essential: coughing, hypertension, or surges in intracranial pressure (ICP) can endanger hemostasis and compromise brain protection. Most serious complications-such as intracranial bleeding, cerebral edema, ischemia, hydrocephalus, or herniation-tend to arise within the first hours after surgery.

The Post Anesthesia Care Unit (PACU) constitutes a important window of observation. At this critical phase many strategies have been developed to protect the brain from complication triggering events. For example, remifentanil infusion-whether manual or target-controlled at effect-site concentrations, like adopted at our institution, titrated to suppress airway reflexes and blunt cardiovascular responses-have been shown to promote safe and controlled awakening while preserving prompt neurological evaluation(1-6), facilitating the identification of surgical from anesthetic causes of delayed recovery. Any unrecognized or delayed deterioration early after surgery may herald potentially warning signs, highlighting the need for accurate, physiology-based monitoring to support timely detection and intervention.

Standard monitoring-focused largely on vital signs-offers limited insight into the underlying brain and autonomic processes that govern recovery. Heat rate variability (HRV) and processed electroencephalography (pEEG) features, may provide novel means to characterize patient vulnerability in the PACU, improving risk stratification and guiding individualized perioperative care.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 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.

Exclusion criteria

  • 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).
  • Inability to provide informed consent (e.g., cognitive impairment, language barrier without interpreter).
  • Refusal of informed consent

Treatment and study plan

Primary outcomes

  1. Temporal trajectories of HRV and pEEG after Neurosurgery in the PACU

    Time frame: 1 year

    Quantitative assessment of autonomic and cortical recovery during the entire period of PACU staying until 120 minutes after extubation or PACU discharge

    • 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).

    • 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

Secondary outcomes

  1. Correlation Between HRV/pEEG Parameters in PACU and Incidence of Early Postoperative Complications Within 48 Hours

    Time frame: 48 hours after surgery

    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)

  2. Correlation Between HRV/pEEG Parameters and Perioperative Drug Exposure

    Time frame: Intraoperative period

    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)

  3. Correlation Between HRV/pEEG Parameters and Perioperative Clinical Variables

    Time frame: Intraoperative period

    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)

  4. Feasibility and Data Quality of HRV and pEEG Monitoring in PACU

    Time frame: First 60 minutes of PACU stay

    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 (%)

Study contacts

Contact information is provided by the study sponsor or research team.

Andrea Gentile, MD

CONTACT

[email protected]

+ 39 02.2394

Marco Gemma, M.D.

CONTACT

[email protected]

02.2394.

Sponsors and collaborators

Lead sponsor

Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta

Other

Registry information

Official study title

Heart Rate Variability and Processed EEG Features as Predictors of Postoperative Outcomes After Cranial Neurosurgery - A Prospective Observational Study in the Post-Anesthesia Care Unit

Acronym: HERO-PACU

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Mar 2, 2026
Registry last updated
Mar 10, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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