Intraosseous infusion flow rates in hypovolemic "pediatric" dogs

We tested a 20-gauge, 21/2-inch spinal needle and a 13-gauge, 31/2-inch bone marrow needle with Ringer's lactate delivered by gravity and 300 mm Hg pressure in vitro and in hypovolemic puppies to ascertain in vivo intraosseous flow rates and to determine the effects of catheter size and anatomic factors on flow rate. In vitro flow was significantly faster than in vivo flow (P = .001). In vivo, mean flow rates were 11 mL/min for the 20-gauge needle and 13 mL/min for the 13-gauge needle by gravity. The mean flows by 300 mm Hg pressure for the same needles were 24 mL/min and 29 mL/min. While the in vivo flow rates were significantly greater for the 13-gauge versus the 20-gauge needle, the differences were not clinically significant (2 mL/min difference by gravity and 5 mL/min difference by pressure). The clinically comparable in vivo rates for the two needles tested indicated that the rates are dependent on flow through the bone marrow rather than the size of the needle. The data suggest that while intraosseous infusion is a rapid technique for gaining vascular access, the flow rates achieved may not be sufficient for the definitive treatment of severe hypovolemic or hemorrhagic shock alone.