title: The efficacy of a simulated intravascular test dose in sevoflurane-anesthetized children: a dose-response study.
abstract: A recent study demonstrated that changes in both heart rate (HR; positive if > or = 10bpm increase) and T-wave amplitude (positive if > or = 25% increase) reliably detect accidental intravascular injection when a full test dose containing epinephrine 0.5 microg/kg is injected intravascularly. We designed this study to prospectively determine whether a smaller dose of epinephrine would produce reliable HR and T-wave changes in sevoflurane-anesthetized children. We studied 80 ASA physical status I infants and children (6-72 mo) undergoing elective surgeries during 1.0 minimum alveolar anesthetic concentration sevoflurane and 67% nitrous oxide in oxygen. After the administration of i.v. atropine 0.01 mg/kg, the patients were randomly assigned to receive either i.v. saline (n = 20), an i.v. test dose (0.1 mL/kg) consisting of 1% lidocaine with 1:200,000 epinephrine (epinephrine 0.5 microg/kg group, n = 20), an i.v. test dose (0.05 mL/kg) (epinephrine 0.25 microg/kg group, n = 20), or an i.v. test dose (0.025 mL/kg) (epinephrine 0.125 microg/kg group, n = 20) via a peripheral vein to simulate the intravascular injection of the test dose. HR and systolic blood pressure were recorded every 20 and 30 s, respectively, and T-wave amplitude of lead II was continuously recorded for subsequent analysis. After the i.v. injection of the test dose, all children in the epinephrine 0.5 and 0.25 microg/kg groups developed positive responses based on the peak T-wave amplitude, whereas all children in the epinephrine 0.5 microg/kg group and 17 children (85%) in the epinephrine 0.25 microg/kg group elicited a positive response according to the peak HR criterion. No false-positive responses were observed with saline injections. Children in the epinephrine 0.125 microg/kg group showed clinically unacceptable efficacy based on either criterion. We conclude that the efficacies of detecting an intravascular injection of the test dose based on the hemodynamic and T-wave criteria are reduced with smaller doses of epinephrine and that HR and T-wave changes are still useful indicators in most patients if epinephrine 0.25 microg/kg is accidentally injected intravascularly.
  
  
  CONCLUSIONS
  To determine whether an epidurally administered local anesthetic has been unintentionally injected into a blood vessel, a small dose of epinephrine is often added to a local anesthetic. We found that an increase in T-wave amplitude > or = 25% in lead II and a heart rate increase > or = 10 bpm are useful indicators for detecting the accidental intravascular injection of a small dose of epinephrine in sevoflurane-anesthetized children.
authors.affiliation: Department of Anesthesia, Akita University School of Medicine, Japan. mtanaka@med.akita-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
mesh_terms: D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000494:pharmacology; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects; D004837:Epinephrine / Q000008:administration & dosage; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007223:Infant; D007275:Injections, Intravenous; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage* / Q000494:pharmacology; D011446:Prospective Studies; D000077149:Sevoflurane; D014662:Vasoconstrictor Agents / Q000008:administration & dosage
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D014662:Vasoconstrictor Agents; D000077149:Sevoflurane; D004837:Epinephrine