Cardiac Autonomic Dysfunction and Perioperative Outcomes
Condition: Neurosurgical Patients
MeSH terms: Autonomic Nervous System Diseases; Primary Dysautonomias
Study type: Observational

Summary: 
      The autonomic nervous system (ANS) is cardinal for maintaining systemic homeostasis and is
      pivotal for the baseline regulation and modulation of vital cardiovascular, hemodynamic,
      respiratory, gastrointestinal, and body temperature regulating functions. Pathological
      perturbations of the ANS leading to cardiac dysautonomia (CAD) affect one in 1000 population.
      Autonomic dysfunction can occur from a variety of pathological conditions such as ischemic
      heart disease, systemic hypertension, diabetes mellitus, neurological illnesses, neurotrauma,
      and cervical spine diseases. When patients with dysautonomia present for surgical procedures,
      they may manifest severe hemodynamic responses that may be less responsive to pharmacological
      interventions. Pre-existing autonomic dysfunction accentuates perioperative hemodynamic
      fluctuations during stressful events like direct laryngoscopy, endotracheal intubation, and
      extubation, and can result in major adverse cardiac events (MACE). The complications arising
      from CAD can prolong the duration of hospital stay and contribute to morbidity and mortality.
      Preoperative diagnosis of CAD helps in anticipation of and preparation for potentially severe
      adverse events in the perioperative period. Most neurosurgical patients are not candidates
      for detailed ANS examination in the supine and standing positions due to their underlying
      neurological condition. Real-time assessment of heart rate variability (HRV) using the
      ANSiscope equipment provides information on the sympathovagal balance during the immediate
      preoperative period and aids in the simple rapid bedside assessment of CAD. This study aims
      to examine the incidence of CAD through HRV assessment in neurosurgical patients, identify
      the potential risk factors for CAD in this population, and evaluate the impact of CAD on
      perioperative outcomes.
    

Detailed description: 
      Demographic and baseline clinical data including comorbid conditions and medication history
      will be collected. Baseline hemodynamic parameters - heart rate (HR) and systolic, diastolic,
      and mean blood pressure (SBP, DBP, MAP), rate pressure product (RPP) calculated as the
      product of HR and SBP and ANSindex (which informs the degree of dysautonomia and is derived
      noninvasively from a recording of 572 R wave to R wave intervals on an electrocardiogram)
      will be recorded in the immediate preoperative period.

      Assessment of risk factors for preoperative CAD The investigators will explore potential risk
      factors for CAD in neurosurgical patients. The investigators postulate some known factors
      such as anxiety which will be diagnosed using the Visual analog scale for anxiety (VAS-A),
      age, gender, neurosurgical pathology, site-specific surgery (high cervical pathology,
      structural brain lesions, brainstem lesion, etc.), pre-existing diabetes mellitus and
      hypertension, and medications used for their treatment, higher American Society of
      Anesthesiology (ASA) grade, etc. to be associated with CAD in neurosurgical patients.

      The investigators will explore the association between CAD and perioperative outcomes. Major
      Adverse Cardiac Events during Intra and postoperative period, in-hospital mortality, and
      duration of postoperative ICU and hospital stay.

      Anesthesia will be administered as per the existing practice. Hemodynamic parameters HR, SBP,
      DBP, MAP at following time points - before and 1 and 2 min after induction of general
      anesthesia, before and at 1, 3, and 5 mins after tracheal intubation, and before and at 1, 3,
      and 5 mins after skull pin application, where applicable. Adverse hemodynamic events -
      persistent hypotension, arrhythmias, myocardial ischemia, cardiac failure, cardiac arrest)
      during the early (after anesthetic induction and before surgical incision), late (surgical
      incision to surgical closure) intraoperative period, recovery period (end of anesthesia to
      discharge from the operating room), post-anesthesia care unit (PACU) period (from arrival to
      discharge from PACU) and early postoperative period (up to 72 hours after surgery),
      neurological status (Glasgow Coma Scale) at hospital discharge, and duration of ICU and
      hospital stay will be recorded. The core temperature will be monitored during the
      intraoperative period to detect hypothermia (<35o C) or hyperthermia (>37.5 o C).

      Sample size and statistical analysis Previous studies in the non-neurosurgical populations
      have determined the prevalence of CAD to vary from 25 to 73%. Considering an average
      prevalence of 50% in the neurosurgical population and a possible 5% margin of error, a sample
      size of 383 would be necessary for achieving a 95% confidence level. Hence the investigators
      plan to recruit 400 patients over a period of 1 year to account for potential dropouts from
      the study.

      Data will be analyzed using Statistical Package for the Social Sciences (SPSS) or R software.
      Continuous variables will be compared by t-test, qualitative data by chi2 test, or Fisher
      exact test. Logistic regression will be used to identify the risk factors for cardiac
      autonomic dysfunction. A p < 0.05 will be considered statistically significant.
    

Intervention name(s): No intervention
Intervention type(s): Other
Intervention description(s): This is a prospective observational study
Other intervention name(s): No interventions
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Consenting patients scheduled for neurosurgical procedures at the National Institute of
        Mental Health and Neurosciences, Bengaluru will be recruited if they fulfill the study
        inclusion criteria during the period of study duration
      
Keywords: cardiac dysautonomia; neurosurgery; heart rate variability; hypotension; anesthesia; major adverse cardiac events; perioperative outcome