title: Effects of isoflurane with and without dexmedetomidine or remifentanil on heart rate variability before and after nociceptive stimulation at different multiples of minimum alveolar concentration in dogs.
abstract: OBJECTIVE
  To evaluate the influence of 3 anesthetic protocols and multiples of minimum alveolar concentration (MAC) on heart rate variability (HRV) with and without nociceptive stimulation in dogs.
  
  
  METHODS
  6 healthy adult Beagles.
  
  
  METHODS
  Each dog was anesthetized 3 times: with isoflurane alone, with isoflurane and a constant rate infusion of dexmedetomidine (IsoD; 3 μg/kg/h, IV), and with isoflurane and a constant rate infusion of remifentanil (IsoR; 18 μg/kg/h, IV). Individual MAC was determined via supramaximal electrical stimulation. Sinus rhythm-derived intervals between 2 adjacent R-R intervals were exported from ECG recordings. Selected HRV time and frequency domain variables were obtained (at 2-minute intervals) and analyzed offline with signed rank tests before and after stimulation at 0.75, 1.0, and 1. 5 MAC for each anesthetic session.
  
  
  RESULTS
  The isoflurane session had the overall lowest prestimulation SDNN (SD of all R-R intervals) values. Prestimulation SDNN values decreased significantly with increasing MAC in all sessions. For the IsoD session, SDNN (milliseconds) or high-frequency power (milliseconds(2)) was inversely correlated with MAC (Spearman rank correlation coefficient for both variables, -0.77). In the isoflurane and IsoR sessions, heart rate increased significantly after stimulation. In the IsoD session, poststimulation SDNN was increased significantly, compared with prestimulation values, at 0.75 and 1.0 MAC.
  
  
  CONCLUSIONS
  On the basis of SDNN and high-frequency power values, anesthetic levels between 0.75 and 1.5 MAC within the same anesthetic protocol could be differentiated, but with a large overlap among protocols. Usefulness of standard HRV variables for assessment of anesthetic depth and nociception in dogs is questionable.
authors.affiliation: Small Animal Clinic, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, D-30559 Hannover, Germany. anne_voigt@gmx.de
authors.forename: Anne M
authors.initials: AM
authors.lastname: Voigt
authors.forename: Carina
authors.initials: C
authors.lastname: Bergfeld
authors.forename: Martin
authors.initials: M
authors.lastname: Beyerbach
authors.forename: Sabine B R
authors.initials: SB
authors.lastname: Kästner
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D000769:Anesthesia, Inhalation / Q000662:veterinary; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D018592:Cross-Over Studies; D020927:Dexmedetomidine / Q000008:administration & dosage / Q000494:pharmacology*; D004285:Dogs; D004359:Drug Therapy, Combination; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010146:Pain / Q000517:prevention & control / Q000662:veterinary*; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D011650:Pulmonary Alveoli; D000077208:Remifentanil
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D010880:Piperidines; D020927:Dexmedetomidine; D007530:Isoflurane; D000077208:Remifentanil