title: Heart rate variability assessment to stratify risk of autonomic imbalance during subarachnoid block: A prospective study.
abstract: BACKGROUND
  Hypotension after subarachnoid block is a common adverse event which can be predicted by simple, safe and indirect measure of autonomic activity.
  
  
  BACKGROUND
  Heart rate variability has been accepted as an indirect measure of autonomic activity.
  
  
  OBJECTIVE
  It was to evaluate preoperatively risk of hypotension after subarachnoid block.
  
  
  METHODS
  This is controlled, randomized blind prospective study.
  
  
  METHODS
  One hundred adult patients of either sex in the age group of 25 to 60 years belonging to ASA physical status of I to III, scheduled for elective infra-umbilical surgery, were enrolled for this randomized prospective study. During preanesthetic check their HRV was analyzed for time domain and frequency domain parameters. They were classified into two groups of 50 patients each depending on their low to high frequency ratios (LF/HF). Group I included patients with LF/HF <2.5 and Group II included patients with LF/HF >2.5. Sensitivity of LF/HF for prediction of hypotension greater than 20% of baseline was tested.
  
  
  RESULTS
  The present study showed significant differences of systolic blood pressure (SBP) after subarachnoid block, depending on baseline LF/HF. Patients with low LF/HF showed lowest SBP of 106.08 ± 3.19 (15.22% fall of base line SBP) as compared to high LF/HF which showed 87.62 ± 8.71 (30.26% fall of base line SBP). Baseline LF/HF parameter correlated significantly with proportionate decrease in SBP after subarachnoid blocks.
  
  
  METHODS
  Hemodynamic parameter was analyzed by using student t test on statgraphic version 5.1.
  
  
  CONCLUSIONS
  Analysis of low and high frequency ratio, reflect autonomic control and may be used as an indirect measure for risk stratification of hypotension after subarachnoid block with high sensitivity.
authors.affiliation: Department of Anesthesiology and Critical Care, Subharti Medical College, Meerut, Uttar Pradesh, India.
authors.forename: Deepak
authors.initials: D
authors.lastname: Sharma
authors.affiliation: Department of Anesthesiology and Critical Care, Subharti Medical College, Meerut, Uttar Pradesh, India.
authors.forename: Kumkum
authors.initials: K
authors.lastname: Gupta
authors.affiliation: Department of Radiodiagnosis and Imaging, Subharti Medical College, Meerut, Uttar Pradesh, India.
authors.forename: Prashant
authors.initials: P
authors.lastname: Gupta
authors.affiliation: Department of Anesthesiology and Critical Care, Subharti Medical College, Meerut, Uttar Pradesh, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Tyagi
keywords: Autonomic nervous system; heart rate variability; subarachnoid block; systolic arterial blood pressure