Today's Veterinary Practice

MAY-JUN 2013

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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Peer reviewed The PracTiTioner's acid–Base Primer: oBTaining & inTerPreTing Blood gases | The Practitioner's Acid–Base Primer Obtaining & Interpreting Blood Gases Lori S. Waddell, DVM, Diplomate ACVECC T his article is the first in a 2-part series that addresses alterations in acid– base and respiratory function, which are common in both emergency patients as well as hospitalized, critically ill patients. Familiarity with obtaining and interpreting blood gases can be essential in the management of these patients. Part 1 will cover obtaining and interpreting blood gases, while Part 2 will discuss differential diagnoses and therapeutic options associated with acid– base abnormalities. ACID–BASE OVERVIEW Metabolic acid–base alterations can lead to: • Altered cardiovascular, neurologic, and respiratory function • Altered response to various drug therapies. Signs of acid–base disturbances are usually vague and cannot be differentiated from clinical signs associated with the underlying disease, making blood gas analysis essential. Both arterial and venous blood gas samples can be used to interpret metabolic derangements. Metabolic acid–base alterations can often be corrected via appropriate IV fluid therapy, other pharmacologic interventions and, ultimately, by addressing the underlying disease. RESPIRATORY FUNCTION OVERVIEW Respiratory function, more specifically the patient's ability to oxygenate and ventilate, can be evaluated with arterial blood gases. However, in most cases, venous blood gases can also be used to assess ventilation, as venous CO2 is typically about 5 mm Hg higher than arterial CO2. Other options for respiratory function evaluation include physical examination findings and pulse oximetry to detect hypoxemia, although arterial blood gases remain the gold standard. Figure 1. Arterial blood gas sample being entered into a blood gas analyzer (heska.com) BlOOD GAS ANAlYzERS There are a variety of different blood gas analyzers on the market, ranging from small point-of-care analyzers to larger laboratory equipment (Figure 1). smaller machines are less expensive, relatively good quality, and easy to run and maintain. some of the larger machines require high maintenance but also provide the best quality control and are more economical when large numbers of samples are anticipated. The type of practice and volume of blood gases the practice evaluates help determine which type of analyzer is best. May/June 2013 Today's Veterinary Practice 43

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