title: Does a sodium-free buffer affect QRS width in experimental amitriptyline overdose?
abstract: OBJECTIVE
  We carried out this study to determine the effects of pH alteration on QRS width with administration of tromethamine, a non-sodium-containing buffering agent, in experimental amitriptyline overdose.
  
  
  METHODS
  Prospective, nonblinded trial.
  
  
  METHODS
  Adult mongrel dogs.
  
  
  METHODS
  Pentobarbital-anesthetized dogs were overdosed with amitriptyline 5 mg/kg followed by infusion at 1.0 mg/kg/minute until the QRS width doubled, then decreased to .5 mg/kg/minute until the end of the experiment. At two defined points of toxicity, the dose of tromethamine required to raise the pH to 7.50 +/- 4 was given. pH and QRS width at a speed of 100 mm/second were measured over a 30-minute period after each tromethamine dose. Data were analyzed with non-linear-regression analysis.
  
  
  RESULTS
  At toxicity 1 the mean pH was 7.32, with a QRS width of 11.6 mm. Two minutes after the tromethamine dose the pH rose to 7.51, with narrowing of the QRS width to 8.4 mm. At toxicity 2 the pH was 7.40, with QRS width of 10.6 mm. Two minutes after tromethamine, the pH rose to 7.49 and the QRS width decreased to 9.7 mm. Regression analysis showed a correlation between pH and QRS width; as pH increased, QRS width decreased (P = .0001).
  
  
  CONCLUSIONS
  Cardiac toxicity of amitriptyline overdose, as manifested by QRS widening, is reversible by pH changes alone.
authors.affiliation: Department of Emergency Medicine, East Carolina University School of Medicine, Greenville, North Carolina, USA.
authors.forename: C K
authors.initials: CK
authors.lastname: Stone
authors.forename: C M
authors.initials: CM
authors.lastname: Kraemer
authors.forename: R
authors.initials: R
authors.lastname: Carroll
authors.forename: R
authors.initials: R
authors.lastname: Low
mesh_terms: D000639:Amitriptyline / Q000633:toxicity*; D000818:Animals; D004285:Dogs; D062787:Drug Overdose / Q000503:physiopathology; D004562:Electrocardiography / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D011446:Prospective Studies; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D014325:Tromethamine; D000639:Amitriptyline