PHARMACOKINETICS FROM MULTIPLE INTRAOSSEOUS AND PERIPHERAL INTRAVENOUS SITE INJECTIONS IN NORMOVOLEMIC AND HYPOVOLEMIC PIGS

Objectives: To examine: a) the rate and extent of delivery of radioact ive tracers to the central circulation from the tibial, medial malleol ar, distal femoral, and humeral intraosseous sites, as well as from a peripheral intravenous site; and b) the end-tidal CO2 response to inje cted sodium bicarbonate at these sites. Design: Prospective, descripti ve study. Setting: Animal laboratory at a university medical center. S ubjects: Twenty anesthetized and mechanically ventilated piglets were cannulated with 18-gauge bone marrow needles at intraosseous sites and 22-gauge Teflon catheters in peripheral veins. A 22-gauge angiocath w as placed in the right carotid artery of each subject. Drug kinetics w ere studied in the normovolemic and hypovolemic (acute bleeding of 25 mL/kg) states. Interventions: Sodium bicarbonate (1 mEq/kg) was inject ed into each of the three intraosseous and one intravenous sites with simultaneous monitoring of end-tidal CO2. A 10-min period for stabiliz ation was allowed between injections. Aliquots of (99m)technetium were injected at randomly selected sites and blood samples were obtained a t 1.5-sec intervals via carotid artery for radioactive counts. Experim ents were repeated after withdrawal of 25 mL/kg of blood. Measurements and Main Results: Assessment by end-tidal CO2 monitoring after 1-mEq/ kg injections of bicarbonate demonstrated a mean initial end-tidal CO2 increase at 12.8 sees and a mean maximal end-tidal CO2 increase of 8 torr (1.06 kPa), with no significant site differences noted. Radioacti ve tracer injections were detected in the carotid artery after 15.4 se es in normovolemic animals and after 21.4 sees in hypovolemic animals, with no significant site differences detected. The proportion of inje cted tracer at 2, 5, 10, 20, 30, and 40 mins identified no significant differences between various intraosseous and intravenous sites. Concl usions: Our study demonstrated similar rapid transit and proportion of bicarbonate and radioactive tracers, reaching the central circulation from multiple intraosseous sites and a peripheral intravenous site. T his finding suggests that adjustments in drug dosage may not be requir ed, using various intraosseous locations as an alternative to peripher al intravenous drug therapy.