title: Heart rate variability predicts severe hypotension after spinal anesthesia for elective cesarean delivery.
abstract: BACKGROUND
  Hypotension due to vasodilation during subarachnoid block (SAB) for elective cesarean delivery may be harmful. Heart rate variability (HRV), reflecting autonomic control, may identify patients at risk of hypotension.
  
  
  METHODS
  Retrospectively, HRV was analyzed in 41 patients who were classified into one of three groups depending on the decrease in systolic blood pressure (SBP): mild (SBP > 100 mmHg), moderate (100 > SBP > 80 mmHg), or severe (SBP < 80 mmHg). Prospectively, HRV and hemodynamic data of 19 patients were studied. Relative low frequency (LF), relative high frequency (HF), and LF/HF ratio were analyzed.
  
  
  RESULTS
  Retrospective analysis of HRV showed a significantly higher sympathetic and lower parasympathetic drive in the groups with moderate and severe compared with mild hypotension before SAB (median, 25th/75th percentiles): LF/HF: mild: 1.2 (0.9/1.8), moderate: 2.8 (1.8/4.6), P < 0.05 versus mild; severe: 2.7 (2.0/3.5), P < 0.05 versus mild. Results were confirmed by findings of LF and HF. Prospectively, patients were grouped according to LF/HF before SAB: low-LF/HF: 1.5 (1.1/2.0) versus high-LF/HF: 4.0 (2.8/4.7), P < 0.05; low-LF: 58 +/- 9% versus high-LF: 75 +/- 10%, P < 0.05; low-HF: 41 +/- 10% versus high-HF: 25 +/- 10%, P < 0.05. High-risk patients had a significantly lower SBP after SAB (76 +/- 21 vs. 111 +/- 12 mmHg; P < 0.05).
  
  
  CONCLUSIONS
  Retrospectively analyzed HRV of patients scheduled to undergo elective cesarean delivery during SAB showed significant differences depending on the severity of hypotension after SAB. Preliminary findings were prospectively confirmed. High LF/HF before SAB predicted severe hypotension. Preoperative HRV analysis may detect patients at risk of hypotension after SAB.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Schwanenweg 21, 24105 Kiel, Germany. hanss@anaesthesie.uni-kiel.de
authors.forename: Robert
authors.initials: R
authors.lastname: Hanss
authors.forename: Berthold
authors.initials: B
authors.lastname: Bein
authors.forename: Thomas
authors.initials: T
authors.lastname: Ledowski
authors.forename: Marlies
authors.initials: M
authors.lastname: Lehmkuhl
authors.forename: Henning
authors.initials: H
authors.lastname: Ohnesorge
authors.forename: Wiebke
authors.initials: W
authors.lastname: Scherkl
authors.forename: Markus
authors.initials: M
authors.lastname: Steinfath
authors.forename: Jens
authors.initials: J
authors.lastname: Scholz
authors.forename: Peter H
authors.initials: PH
authors.lastname: Tonner
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002585:Cesarean Section; D005260:Female; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007022:Hypotension / Q000139:chemically induced* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011247:Pregnancy; D011446:Prospective Studies; D012189:Retrospective Studies