Cardiac Autonomic Dysfunction and Perioperative Outcomes

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.

Inclusion criteria

• aged between 18 and 80 years
• belonging to ASA grade 1-4
• scheduled for craniotomies or spinal surgeries under anesthesia

Exclusion criteria

• scheduled for redo procedures
• patients with preoperative arrhythmias and cardiac failure
• patients on preoperative inotropic support
• pregnant neurosurgical patients