title: Are 2 smaller intravenous catheters as good as 1 larger intravenous catheter?
abstract: OBJECTIVE
  Using Poiseuille's law and standardized gauge sizes, an 18-gauge (g) intravenous catheter (IV) should be 2.5 times faster than a 20-g IV, but this is not borne out by observation, in vitro testing, and manufacturer's data. Our objective was to determine if the infusion rate of a single 18-g IV was equivalent to the infusion rate of two 20-g IVs.
  
  
  METHODS
  This was a prospective study in healthy adult volunteers. Subjects simultaneously received 500 mL of normal saline via an 18-g IV in one arm and 500 mL of normal saline via two 20-g IVs in the other arm. We measured the rates of fluid administration. Paired Student's t test was used for comparison of the 2 arms of the study. We estimated that 18 trials were needed in sample size analysis.
  
  
  RESULTS
  Eighteen trials were completed. The mean infusion rate for a single 18-g 500-mL IV administration was 35.6 mL/min (95% confidence interval [CI], 30.3-40.8), with manufacturer's rating being 105 mL/min. The mean infusion rate for two 20-g IVs was 41.3 mL/min (95% CI, 36.1-46.4), with manufacturer's rating being 120 mL/min. The rate of infusion via two 20-g IVs were statistically significantly faster than the single 18-g IV, with a mean difference in flow rate of 5.7 mL/min (95% CI, 1.3-10; P = .026).
  
  
  CONCLUSIONS
  In healthy volunteers, administration of intravenous fluids through two 20-g IVs is faster than a single 18-g IV, although both approaches are markedly slower than the manufacturer's estimates.
authors.affiliation: Department of Emergency Medicine, Jacobi Medical Center, Bronx, NY 10461, USA. siuf@verizon.net
authors.forename: Siu Fai
authors.initials: SF
authors.lastname: Li
authors.forename: Michael
authors.initials: M
authors.lastname: Cole
authors.forename: Rhonda
authors.initials: R
authors.lastname: Forest
authors.forename: Mikaela
authors.initials: M
authors.lastname: Chilstrom
authors.forename: Eugene
authors.initials: E
authors.lastname: Reinersman
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jones
authors.forename: Shreni
authors.initials: S
authors.lastname: Zinzuwadia
authors.forename: Sheila
authors.initials: S
authors.lastname: King
authors.forename: Kabir
authors.initials: K
authors.lastname: Yadav
mesh_terms: D000328:Adult; D002406:Catheterization, Peripheral / Q000295:instrumentation*; D004636:Emergency Service, Hospital; D004867:Equipment Design; D005440:Fluid Therapy; D018056:Hemorheology / Q000502:physiology*; D006801:Humans; D007262:Infusions, Intravenous / Q000295:instrumentation*; D011446:Prospective Studies; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D012965:Sodium Chloride