The change of arteriovenous carbon dioxide and pH gradients during severe hemorrhagic shock and resuscitation.

OBJECTIVE To investigate clinically useful markers for determining the severity of hemorrhagic shock and adequacy of resuscitation. METHODS Prospective study was undertaken in 12 dogs, using an established model for hemorrhagic shock. The anesthetized dogs were bled to a mean arterial pressure of 40 mmHg which was maintained for 3 hours. Then each animal was resuscitated with heperinized whole blood followed by intravenous infusion of dobutamine at a rate of 5 micrograms.kg-1.min-1 for 10 minutes. Arterial and mixed venous blood gases, arterial lactate concentrations and hemodynamic parameters were measured throughout the study. RESULTS A difference in the PCO2 and pH values between arterial and mixed venous blood was observed. Arterial-venous PCO2 and pH difference increased significantly after sustained shock. The arteriovenous carbon dioxide and pH gradients recovered more rapidly than arterial lactate levels after successful resuscitation with blood and dobutamine. CONCLUSION Arterial blood gases fail to reflect the acid-base status of tissues during hemorrhagic shock. The differences in PCO2 and pH values between arterial and mixed venous blood could be used as clinical indicators for assessing the severity of shock and efficacy of resuscitation.