Nursing ABGs! QUESTIONS WITH CORRECT ANSWERS, 2024,2025

Order when reading ABGs? - Oxygenation status (PaO2, level of FiO2 received, O2 delivery device), acid-base balance (pH), ventilation status (PaCO2-also influences acid-base balance), bicarbonate level What are the clinical indications for drawing an ABG? - Patient has a change in LOC, increasing respiratory difficulty, or low blood pressure (or change in BP on arrival). Why do we need to draw an ABG for a patient with low blood pressure? - Because if the body is acidotic and the pH is very low, the patient loses the autonomic nervous system ability to vasoconstrict. ABGs will tell us the pH, and then we can proceed to raise the pH to normalize the blood pressure. Formula for ideal tidal volume on ventilator - 6 to 10ml (preferably 6) per kg of patient's ideal body weight. Bicarbonate level during respiratory failure that warrants administering more bicarb - 10-11 Normal PaO2 - 80-100mmHg Normal PaO2 for COPD patient - 60-80mmHg Why is pulse oximetry unreliable? What other lab do we need to get the full picture of oxygenation status? - Because you may have 100% of your hemoglobin saturated, but it does not tell you how many hemoglobin you have. Need to also draw H and H. What test can we do to determine oxygenation at the cellular level in the body tissues? - SvO2, venous saturation. Normal is 72-75%. Drawn from CVC. Normal pH - 7.35-7.45 (ideally 7.40)Normal PaCO2 - 35-45mmHg What does PaCO2 tell us about the patient? - Ventilation (how well the body is able to get rid of CO2). Normal HCO3- - 22-28mEq/L Where is Bicarbonate made and what does it do? - Base made in the kidneys, buffers or neutralizes acids. How long does the bicarbonate response take in response to low pH? - Several hours to a couple days Base excess - Total buffer base of the body. Indicates how well your body is able to handle the acids produced by metabolism. Base Excess Value of -2mEq - Not a lot of buffer around because body is using it up. indicates an acidotic state. Base Excess Value of +2mEq - Body is not making acid, or is in alkalotic state. Not too much of a concern. Factors affecting oxygen delivery - Cardiac output, hemoglobin, Arterial O2 saturation, affinity of hemoglobin for O2, hemorrhage/hypovolemia clots Four causes of dropping SvO2: - 1. The cardiac output is not high enough to meet tissue oxygen needs. 2. the hemoglobin is too low. 3. the SaO2 is too low. 4. The oxygen consumption has increased without an increase in oxygen delivery.Mild Hypoxemia - 60-79mmHg (may be acceptable in individuals over 75 or patients with COPD) Moderate Hypoxemia - 50-59mmHg Severe Hypoxemia - 20-49mmHg