title: The hemodynamic response to dexmedetomidine loading dose in children with and without pulmonary hypertension.
abstract: BACKGROUND
  Dexmedetomidine, an α-2 receptor agonist, is widely used in children with cardiac disease. Significant hemodynamic responses, including systemic and pulmonary vasoconstriction, have been reported after dexmedetomidine administration. Our primary goal of this prospective, observational study was to quantify the effects of dexmedetomidine initial loading doses on mean pulmonary artery pressure (PAP) in children with and without pulmonary hypertension.
  
  
  METHODS
  Subjects were children undergoing cardiac catheterization for either routine surveillance after cardiac transplantation (n = 21) or pulmonary hypertension studies (n = 21). After anesthetic induction with sevoflurane and tracheal intubation, sevoflurane was discontinued and anesthesia was maintained with midazolam 0.1 mg/kg i.v. (or 0.5 mg/kg orally preoperatively) and remifentanil i.v. infusion 0.5 to 0.8 μg/kg/min. Ventilation was mechanically controlled to maintain PCO2 35 to 40 mm Hg. When end-tidal sevoflurane was 0% and fraction of inspired oxygen (FIO2) was 0.21, baseline heart rate, mean arterial blood pressure, PAP, right atrial pressure, pulmonary artery occlusion pressure, right ventricular end-diastolic pressure, cardiac output, and arterial blood gases were measured, and indexed systemic vascular resistance, indexed pulmonary vascular resistance, and cardiac index were calculated. Each subject then received a 10-minute infusion of dexmedetomidine of 1 μg/kg, 0.75 μg/kg, or 0.5 μg/kg. Measurements and calculations were repeated at the conclusion of the infusion.
  
  
  RESULTS
  Most hemodynamic responses were similar in children with and without pulmonary hypertension. Heart rate decreased significantly, and mean arterial blood pressure and indexed systemic vascular resistance increased significantly. Cardiac index did not change. A small, statistically significant increase in PAP was observed in transplant patients but not in subjects with pulmonary hypertension. Changes in indexed pulmonary vascular resistance were not significant.
  
  
  CONCLUSIONS
  Dexmedetomidine initial loading doses were associated with significant systemic vasoconstriction and hypertension, but a similar response was not observed in the pulmonary vasculature, even in children with pulmonary hypertension. Dexmedetomidine does not appear to be contraindicated in children with pulmonary hypertension.
authors: From the Department of Anesthesiology, Department of Pediatrics, The Research Institute, and Department of Pediatrics (Cardiology), Children's Hospital Colorado, University of Colorado, Denver, Colorado.
authors: Robert H
authors: RH
authors: Friesen
authors: Christopher S
authors: CS
authors: Nichols
authors: Mark D
authors: MD
authors: Twite
authors: Kathryn A
authors: KA
authors: Cardwell
authors: Zhaoxing
authors: Z
authors: Pan
authors: Biagio
authors: B
authors: Pietra
authors: Shelley D
authors: SD
authors: Miyamoto
authors: Scott R
authors: SR
authors: Auerbach
authors: Jeffrey R
authors: JR
authors: Darst
authors: D Dunbar
authors: DD
authors: Ivy
mesh_terms: D000293:Adolescent; D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D020927:Dexmedetomidine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006439:Hemodynamics / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy* / Q000503:physiopathology; D007223:Infant; D008297:Male; D011446:Prospective Studies
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D020927:Dexmedetomidine
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