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 PCO2 values determined from of simultaneously corrected samples of central venous and intraosseous blood during sequential changes in cardiac output.

DESIGN

Prospective, descriptive study.

SETTING

An animal laboratory in a university medical center.

SUBJECTS

Fourteen mixed breed 4-wk-old piglets.

INTERVENTIONS

Animals were anesthetized with ketamine hydrochloride and neuromuscular blockade was induced by the administration of pancuronium bromide. After endotracheal intubation and the institution of mechanical ventilation, a 4-Fr pulmonary artery catheter and a carotid artery cannula were inserted via a cutdown into the right neck of each piglet. A 16-gauge intraosseous needle was inserted into the anteromedial surface of the right tibia.

MEASUREMENTS AND MAIN RESULTS

Central venous and intraosseous blood gas samples were obtained simultaneously with thermodilution cardiac output measurements. Cardiac output measurements were as follows: during steady state (0.80 +/- 0.14 L/min), after volume loading 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, and 0.43 +/- 0.16 L/min, respectively) and at exsanguination (unrecordable). Paired t-tests demonstrated no significant differences in pH and PCO2 values between intraosseous and central venous samples under all study conditions. Limits of agreement for difference in PCO2 between 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.

CONCLUSIONS

Intraosseous blood samples can be obtained without difficulty even during extreme hypovolemia. The pH and PCO2 values of intraosseous and central venous blood samples were similar under all study conditions. Intraosseous blood may be a useful alternative to central venous blood to assess tissue acid-base status during hemorrhagic shock and other low-flow states.