{"id":5724,"date":"2021-05-13T15:03:46","date_gmt":"2021-05-13T19:03:46","guid":{"rendered":"https:\/\/todaysveterinarynurse.com\/?post_type=articles&p=5724"},"modified":"2022-05-18T19:19:16","modified_gmt":"2022-05-18T19:19:16","slug":"the-veterinary-nurses-role-in-reading-blood-gases","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarynurse.com\/diagnostics\/the-veterinary-nurses-role-in-reading-blood-gases\/","title":{"rendered":"The Veterinary Nurse\u2019s Role in Reading Blood Gases"},"content":{"rendered":"

Obtaining blood samples for serum chemistry panels, complete blood counts, and coagulation panels is a familiar procedure for most veterinary nurses, but samples for blood gases are less commonly collected and analyzed in general practice. Knowing when and how to draw blood gas samples, as well as how to interpret the results, is critical to good patient care, as veterinary nurses are frequently the members of the team reviewing and delivering results. What the veterinary nurse reports back to the clinician has a direct impact on the patient\u2019s treatment and outcome.<\/p>\n

Why Measure Blood Gasses?<\/h2>\n

Blood gas measurement allows assessment of 3 primary parameters: the patient\u2019s oxygenation, ventilation, and acid\u2013base status. Blood gases can also be used to assess blood glucose, electrolytes, ionized calcium, and\/or lactate levels.\u00a0<\/span><\/span><\/p>\n

When used alone or in conjunction with a serum chemistry profile and a complete blood count, blood gas analysis aids in the diagnosis and treatment of many disease processes that are directly related to metabolic or respiratory dysfunction. Blood gas results are also indicators of how well that patient\u2019s body is compensating for that disease. Being familiar with the dysfunctions that affect blood gases and their causes will help veterinary nurses remind veterinarians that blood gases can play a vital role in diagnosis and treatment. When a blood gas reading is needed, veterinary nurses should understand vessel selection (arterial or venous), collection methods, normal values and reference ranges (<\/span>TABLE 1<\/span><\/strong>), and the physiologic meaning of findings.<\/span><\/p>\n

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Overview of Sample Collection and Processing<\/h2>\n

Step-by-step descriptions of how to properly obtain and process blood samples for blood gas evaluation are available elsewhere, but a few key considerations are listed here. <\/span>TABLE 2<\/span><\/strong> lists common sampling and processing errors and their effects.<\/span><\/p>\n

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Obtaining Venous Samples<\/h3>\n

Venous blood gas samples are commonly collected from the jugular vein, unless a central line is present, in which case they should be collected from the central line. Samples from these locations give a more global picture of the patient\u2019s status than a sample taken from a peripheral vessel (<\/span>FIGURE 1<\/span><\/strong>).<\/span><\/p>\n

\"FigureFigure 1. Process of obtaining a venous blood gas sample from a lateral saphenous central venous catheter. (A) Catheter in place with necessary supplies.<\/span><\/a><\/div>
\"FigureFigure 1. Process of obtaining a venous blood gas sample from a lateral saphenous central venous catheter. (B) Tapping out all air from syringe.<\/span><\/a><\/div>
\"FigureFigure 1. Process of obtaining a venous blood gas sample from a lateral saphenous central venous catheter. (C) Syringe sealed against air contamination.<\/span><\/a><\/div>
<\/div><\/div>\n

Obtaining Arterial Samples<\/h3>\n

For arterial sampling, the area surrounding the collection site should be clipped and scrubbed. Hands should be sanitized and gloves donned. A prepared heparin (1000 IU\/mL)-coated 3-mL syringe, a fresh 25-gauge needle, and a rubber stopper or tightly fitted syringe cap are needed.<\/span><\/p>\n

TIP:<\/span><\/strong> Obtaining an arterial blood gas sample from a conscious patient can be challenging and cause pain. If the patient is anxious, panting, and\/or shaking, this activity could alter the results. A local infusion of 2% lidocaine or a topical application of EMLA cream (a eutectic mixture of 2.5% lidocaine and 2.5% prilocaine) can aid in pain management of arterial punctures along with sedation to relieve stress.<\/span><\/p>\n

Handling Samples<\/h3>\n

Once the blood sample is collected, every effort should be made to quickly remove any air bubbles from the syringe. Flicking the syringe and expelling air will help keep the integrity of the sample. The sample should be capped or the needle put in a rubber stopper. This prevents further contamination of the sample with air. Rolling the sample between the palms helps combine the sample with the anticoagulant, avoiding the common error of sample clotting.<\/span><\/p>\n

Processing Samples<\/h3>\n

The sample should be analyzed directly after collection. If this is not possible, then the sample should be immersed in ice water.1<\/sup> At room temperature, if the sample is not analyzed within 20 minutes, continued cell metabolism starts to increase the PCO2<\/sub> and decrease the pH. The sample can be stored for up to 2\u00a0hours in an ice water bath; otherwise, a new sample must be obtained.<\/span><\/p>\n

Evaluation of Blood Gas Findings<\/h2>\n

When assessing metabolic function, obtaining a venous sample is appropriate. Respiratory function can be assessed from venous blood gas findings; however, obtaining an arterial sample to assess whether respiratory dysfunction is affecting oxygenation (PaO2<\/sub>) is ideal in clinical treatment. <\/span>TABLE 3<\/span><\/strong> lists the findings for metabolic and respiratory acidosis and alkalosis.\u00a0<\/span><\/span><\/p>\n

\"Sidari_TVNSummer21_BloodGasses_Table3\"<\/a><\/p>\n

Metabolic Dysfunction<\/h3>\n

Maintaining a balanced pH is vital to overall cellular function. The lungs and kidneys have synergistic roles in maintaining pH, which, along with chemical buffers, is constantly monitored and regulated by the brain. The body uses multiple mechanisms to correct acid\u2013base imbalances, some of which work faster than others. For example, the process in which the lungs aid in pH balance takes effect in minutes to hours, unlike the process by which the kidneys compensate, which takes hours to days. Like the lungs, chemical buffers can assist rapidly in maintaining acid\u2013base balance.<\/span><\/p>\n

Metabolic Acidosis<\/strong><\/p>\n

In patients with metabolic acidosis, blood gas analysis will reveal decreased<\/i> pH, normal to low-normal<\/i> PCO2<\/sub>, and decreased<\/i> <\/b>HCO3<\/sub>. Metabolic acidosis can be seen when there is a loss of bicarbonate, an increased production or addition of acids, or failure of excretion of acids. Electrolytes, lactate, ketones, base excess, anion gap analysis, and urinalysis can help determine the type of metabolic acidosis present.<\/span><\/p>\n