title: Heart Rate Variability Analysis in an Experimental Model of Hemorrhagic Shock and Resuscitation in Pigs.
abstract: BACKGROUND
  The analysis of heart rate variability (HRV) has been shown as a promising non-invasive technique for assessing the cardiac autonomic modulation in trauma. The aim of this study was to evaluate HRV during hemorrhagic shock and fluid resuscitation, comparing to traditional hemodynamic and metabolic parameters.
  
  
  METHODS
  Twenty anesthetized and mechanically ventilated pigs were submitted to hemorrhagic shock (60% of estimated blood volume) and evaluated for 60 minutes without fluid replacement. Surviving animals were treated with Ringer solution and evaluated for an additional period of 180 minutes. HRV metrics (time and frequency domain) as well as hemodynamic and metabolic parameters were evaluated in survivors and non-survivors animals.
  
  
  RESULTS
  Seven of the 20 animals died during hemorrhage and initial fluid resuscitation. All animals presented an increase in time-domain HRV measures during haemorrhage and fluid resuscitation restored baseline values. Although not significantly, normalized low-frequency and LF/HF ratio decreased during early stages of haemorrhage, recovering baseline values later during hemorrhagic shock, and increased after fluid resuscitation. Non-surviving animals presented significantly lower mean arterial pressure (43±7 vs 57±9 mmHg, P<0.05) and cardiac index (1.7±0.2 vs 2.6±0.5 L/min/m2, P<0.05), and higher levels of plasma lactate (7.2±2.4 vs 3.7±1.4 mmol/L, P<0.05), base excess (-6.8±3.3 vs -2.3±2.8 mmol/L, P<0.05) and potassium (5.3±0.6 vs 4.2±0.3 mmol/L, P<0.05) at 30 minutes after hemorrhagic shock compared with surviving animals.
  
  
  CONCLUSIONS
  The HRV increased early during hemorrhage but none of the evaluated HRV metrics was able to discriminate survivors from non-survivors during hemorrhagic shock. Moreover, metabolic and hemodynamic variables were more reliable to reflect hemorrhagic shock severity than HRV metrics.
authors.affiliation: LIM08-Laboratory of Anesthesiology, Department of Anesthesia and Surgical Intensive Care, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Edgard
authors.initials: E
authors.lastname: Salomão
authors.affiliation: LIM08-Laboratory of Anesthesiology, Department of Anesthesia and Surgical Intensive Care, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Denise Aya
authors.initials: DA
authors.lastname: Otsuki
authors.affiliation: LIM08-Laboratory of Anesthesiology, Department of Anesthesia and Surgical Intensive Care, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Andre Luis
authors.initials: AL
authors.lastname: Correa
authors.affiliation: LIM08-Laboratory of Anesthesiology, Department of Anesthesia and Surgical Intensive Care, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Denise Tabacchi
authors.initials: DT
authors.lastname: Fantoni
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Fernando
authors.initials: F
authors.lastname: dos Santos
authors.affiliation: Hypertension Unit, Heart Institute (InCor), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Maria Claudia
authors.initials: MC
authors.lastname: Irigoyen
authors.affiliation: LIM08-Laboratory of Anesthesiology, Department of Anesthesia and Surgical Intensive Care, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Jose Otavio Costa
authors.initials: JO
authors.lastname: Auler
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004562:Electrocardiography; D004573:Electrolytes / Q000097:blood; D005740:Gases / Q000097:blood; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics; D012151:Resuscitation; D012771:Shock, Hemorrhagic / Q000378:metabolism / Q000503:physiopathology*; D013552:Swine
chemical_list: D004573:Electrolytes; D005740:Gases