• Jonathan Yost, Phillip Baldwin, Sarah Bellenger, Freida Bradshaw, Edna Causapin, Richelle Demotica, Michael Livingston, Cynthia Lee, Brian Gegel, James Burgert, Adam Claessens, Don Johnson, and Michael Loughren.
• Department of Anesthesia and Operative Services, Madigan Army Medical Center, Joint Base Lewis-McChord, Washington.

ObjectiveCompare the pharmacokinetics of atropine administered via the intravenous (IV), intramuscular (IM), and intraosseous (IO) routes in a normovolemic and hypovolemic swine model.DesignProspective, between subjects, experimental study.SettingVivarium.SubjectsYorkshire-cross swine (N = 36).InterventionAtropine was administered via IV, IM, or IO routes to normovolemic and hypovolemic swine. Blood samples were drawn at regular intervals after atropine administration and analyzed for plasma atropine concentration. Pharmacokinetic parameters were obtained from modeling the plasma concentrations.Main Outcome MeasurementsPharmacokinetic parameters, maximum concentration (Cmax) and time to maximum concentration (Tmax).ResultsThe IV and IO groups in both the normovolemic and hypovolemic models reached peak plasma concentration immediately and had a very rapid distribution phase with no apparent absorption phase for the IO groups. Peak plasma concentration and time to reach peak concentration were both significantly lower for the IM groups. There was a significant increase in absorption time with IM administration in the hypovolemic model compared to the normovolemic model.ConclusionThe IO route is an effective method of administering atropine and is comparable to the IV route even under conditions of significant hemorrhage. Therapeutic levels of atropine may be delayed and possibly difficult to obtain via IM injection in the presence of hypovolemic shock.

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