Acid-base status of blood from intraosseous and mixed venous sites during prolonged cardiopulmonary resuscitation and drug infusions

Objectives: a) To determine the relationship of acid-base balance (pH, PCO2 ) of blood samples from the intraosseous and the mixed venous route during prolonged cardiopulmonary resuscitation; b) to compare the effect of separa te infusions of epinephrine, fluid boluses, or sodium bicarbonate through t he intraosseous sites on the acid-base status of intraosseous and mixed ven ous blood during cardiopulmonary resuscitation; and c) to compare pH and PC O2 of intraosseous and mixed venous blood samples after sequential infusion s of fluid, epinephrine, and sodium bicarbonate through a single intraosseo us site. Design: Prospective, randomized study. Setting: Animal laboratory at a university center. Subjects: Thirty-two mixed-breed piglets (mean weight, 30 kg). Interventions: Piglets were anesthetized and prepared for blood sampling an d cardiopulmonary resuscitation. After anoxic cardiac arrest, ventilation w as resumed and chest compression was resumed. Blood gas samples from the pu lmonary artery and both intraosseous sites were obtained simultaneously at baseline, at cardiac arrest, and at 5, 10, 15, 20, and 30 mins of cardiopul monary resuscitation for group 1 (control group) and after drug (epinephrin e and sodium bicarbonate) and saline infusions via one of the intraosseous cannulas in groups 2 through 5. Measurements and Main Results: We found no differences between intraosseous and mixed venous pH and PCO2 during periods of <15 mins of cardiopulmonary resuscitation. However, this relationship was not maintained during prolon ged cardiopulmonary resuscitation and after bicarbonate infusion. After lar ge volume saline infusion, the pH and PCO2 of mixed venous and intraosseous blood were similar. During epinephrine infusion, the relationship between intraosseous and mixed venous pH and PCO2 was similar to that found in the control group. Conclusions: The intraosseous blood sample could be used to assess central acid-base balance in the early stage of arrest and cardiopulmonary resuscit ation of <15 mins. However, during cardiopulmonary resuscitation of longer duration, drug infusions may render the intraosseous site inappropriate for judging central acidosis.