Arterial and Venous Blood Gases

Abstract

Blood gases are obtained to determine ventilation, oxygenation, and acid–base status. Arterial blood gases and acid–base status are used to evaluate the progress of therapy and to indicate when adjustments are necessary. Until recently blood gas analysis was labor intensive and cost prohibitive in private practice veterinary medicine. The dead space of a 3-mL syringe is coated with lithium or sodium heparin (1000 U/mL); excess heparin is expelled from the syringe. Arterial blood gas sample may be collected from an arterial catheter. Samples stored in an ice bath for up to 4–6 hours show very little change in pH and PCO2/PO2. Usually, blood gas samples are analyzed at 37°C; seldom is the patient’s temperature the same as the blood gas analyzer. Venous blood gases are a reasonable alternative to arterial blood gases when one wants to assess acid–base status. It has been reported that venous blood will accurately reflect the acid–base status of dogs with normal circulatory status.