title: Atropine aborts bradycardic effect of endotracheally administered vasopressin.
abstract: BACKGROUND
  Vasopressin is an alternative drug to adrenaline in intractable ventricular fibrillation. However, vasopressin can cause significant bradycardia, resulting in reduced cardiac output. We investigated whether pre-treatment with atropine abrogates vasopressin-induced bradycardia in a beating-heart canine model.
  
  
  METHODS
  Five adult mongrel dogs received endotracheal vasopressin (1.0 U/kg) with or without endotracheal atropine (0.02 mg/kg) or a placebo (10 ml saline) after being anesthetized and ventilated. Hemodynamic variables and arterial blood gases were determined. Each dog (studied 3 times, one week apart) served as its own control.
  
  
  RESULTS
  Endotracheal vasopressin produced early and significant (p<0.05) bradycardia (from 55+/-7 mmHg to 35+/-5 beats/min) compared with controls, starting one minute post-injection and lasting one hour. In contrast, in atropine-pretreated animals the heart rate increased significantly (p<0.05) for as long as one hour post-atropine and vasopressin administration. In addition, animals treated with vasopressin with or without atropine exhibited a significant rise in diastolic blood pressure (from 83+/-5 to 160+/-15 and from 83+/-3 to 108+/-10 mmHg, respectively). Systolic and mean blood pressures also increased significantly compared with controls. Blood gases remained unchanged in all groups.
  
  
  CONCLUSIONS
  Endotracheal administration of vasopressin can cause protracted bradycardia. Pretreatment with atropine can abrogate this effect. We suggest that atropine administration be considered when vasopressin is administered during cardio-pulmonary resuscitation. Further studies are warranted to evaluate the effect of vasopressin and atropine in a closed-chest model of cardio-pulmonary resuscitation.
authors.affiliation: Departemnt of Pediatric Pulmonology, of the Chaim Sheba Medical Center, Tel-Hashomer, Israel. ori.efrati@sheba.health.gov.il
authors.forename: Ori
authors.initials: O
authors.lastname: Efrati
authors.forename: Dalit
authors.initials: D
authors.lastname: Modan-Moses
authors.forename: Ron
authors.initials: R
authors.lastname: Ben-Abraham
authors.forename: Haim
authors.initials: H
authors.lastname: Bibi
authors.forename: Gideon
authors.initials: G
authors.lastname: Paret
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D001919:Bradycardia / Q000139:chemically induced* / Q000503:physiopathology / Q000517:prevention & control*; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007442:Intubation, Intratracheal; D008297:Male; D014667:Vasopressins / Q000008:administration & dosage*
chemical_list: D014667:Vasopressins; D001285:Atropine