COMPARISON OF PH AND CARBON-DIOXIDE TENSION VALUES OF CENTRAL VENOUS AND INTRAOSSEOUS BLOOD DURING CHANGES IN CARDIAC-OUTPUT

Objective: To compare the pH and Pco(2) values determined from of simu ltaneously corrected samples of central venous and intraosseous blood during sequential changes in cardiac output. Design: Prospective, desc riptive study. Setting: An animal laboratory in a university medical c enter. Subjects: Fourteen mixed breed 4-wk-old piglets. Interventions: Animals were anesthetized with ketamine hydrochloride and neuromuscul ar blockade was induced by the administration of pancuronium bromide. After endotracheal intubation and the institution of mechanical ventil ation, a 4-Fr pulmonary artery catheter and a carotid artery cannula w ere inserted via a cutdown into the right neck of each piglet. A 16-ga uge intraosseous needle was inserted into the anteromedial surface of the right tibia. Measurements and Main Results: Central venous and int raosseous blood gas samples were obtained simultaneously with thermodi lution cardiac output measurements. Cardiac output measurements were a s follows: during steady state (0.80 +/- 0.14 L/min), after volume loa ding of 15 mL/kg (1.00 +/- 0.25 L/min), after three successive bleeds of 15 mL/kg each at 30-min intervals (0.70 +/- 0.28, 0.54 +/- 0.22, an d 0.43 +/- 0.16 L/min, respectively) and at exsanguination (unrecordab le). Paired t-tests demonstrated no significant differences in pH and Pco(2) values between intraosseous and central venous samples under al l study conditions. Limits of agreement for difference in Pco(2) betwe en sites, within the range of cardiac outputs studied, were -12.86 to 11.38 torr (-1.71 to 1.46 kPa) and for pH were -0.09 to 0.15. Conclusi ons: Intraosseous blood samples can be obtained without difficulty eve n during extreme hypovolemia. The pH and Pco, values of intraosseous a nd central venous blood samples were similar under all study condition s. Intraosseous blood may be a useful alternative to central venous bl ood to assess tissue acid-base status during hemorrhagic shock and oth er low-flow states.