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Questions and Answers
What does the arterial blood gas (ABG) primarily measure regarding the body's acid/base status?
Which component of arterial blood gases indicates the adequacy of ventilation?
What is the role of bicarbonate (HCO3) in the body?
Which method is considered the gold standard for assessing oxygenation and acid-base disorders?
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What is the primary function of catabolism within metabolism?
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What does the VBG reliably assess in a clinical situation?
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Which process is involved in the transformation of complex saccharides into glucose in the liver?
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Which factors can alter the pH in the body?
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What factor can potentially increase both PT and INR in a patient?
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How long should a patient ideally stabilize before an arterial blood gas (ABG) sample is taken after a therapeutic intervention?
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What effect does a decrease in body temperature have on PaCO2 levels?
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What is a common error that can occur if air bubbles are introduced into an ABG sample?
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What could a prolonged time (over 30 minutes) before testing an ABG sample lead to?
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What laboratory test measures a patient's intrinsic clotting pathway?
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What is a potential consequence of heparin dilution in an ABG sample?
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What happens to excess blood glucose when levels are abnormally high?
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Which of the following factors is NOT a consideration for proper ABG sampling?
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What role do proteins play in the body?
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Which statement about lipid metabolism is true?
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What is the respiratory quotient (RQ) for carbohydrate metabolism?
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How much ATP is produced from the complete oxidation of glucose in the presence of oxygen?
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What does anaerobic metabolism primarily produce?
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Where is ATP primarily produced within the cell?
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What condition can result from the formation of ketone bodies in the absence of sufficient glucose?
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What is the primary reason for ensuring a sample is adequately heparinized during arterial blood gas sampling?
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How much blood is typically required for an adequate arterial blood gas sample in adults?
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What is the formula for calculating total oxygen content in the blood?
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What effect does 2,3 Diphosphoglycerate (DPG) have on hemoglobin?
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Which shift in the oxyhemoglobin dissociation curve indicates a decreased affinity of hemoglobin for oxygen?
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What proportion of fetal hemoglobin is typically present in a term infant at birth?
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Which of the following describes carboxyhemoglobin?
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Which statement about normal hemoglobin levels is accurate?
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Study Notes
Arterial Blood Gas (ABG)
- ABG aids in diagnosis, assessment, and treatment by providing information on pH, PaCO2, PaO2, HCO3, and oxygen saturation in arterial blood.
- pH indicates the body's acid/base status.
- PaCO2 reflects ventilation adequacy.
- PaO2 measures the amount of oxygen dissolved in the blood and correlates to the SpO2.
- HCO3 represents bicarbonate, a significant acid buffer system managed by the kidneys.
- VBG can be a reliable alternative for assessing pH, PvCO2, and HCO3, but its accuracy can be affected by local metabolism and variability in unstable patients.
- ABG is the gold standard for assessing and managing oxygenation and acid-base disorders.
Metabolism
- Metabolism is the sum of chemical processes in the body, resulting in growth, energy generation, and other bodily functions.
- Catabolism breaks down complex molecules to create energy.
- Anabolism builds complex molecules from simpler ones, requiring energy.
Carbohydrates
- Primary energy source, readily absorbed into the bloodstream.
- Simple sugars are absorbed as glucose, complex saccharides require glycogenolysis to transform into glucose in the liver.
- Gluconeogenesis in the liver produces glucose from pyruvic acid, lactic acid, amino acids, and glycerol.
- Excess blood glucose is excreted in the urine, converted to fat, or stored as glycogen.
Protein
- Essential for tissue growth, repair, and maintenance.
- Provides building blocks for RNA, DNA, and enzymes.
- Involved in hormonal function.
- Absorbed as amino acids and synthesized by the liver.
- Protein oxidation produces CO2, H2O, energy, and urea.
Lipids
- Energy stores, signaling molecules, and structural components of cell membranes.
- Absorbed from the intestine or synthesized from glucose, pyruvic acid, and amino acids.
- Lipid breakdown produces ketone bodies, which can lead to metabolic acidosis.
Respiratory Quotient (RQ)
- Reflects the volume of CO2 produced per volume of O2 consumed.
- Carbohydrate metabolism RQ is 1.0.
- Fat metabolism RQ is 0.7.
- Protein metabolism RQ is 0.8.
- Whole-body RQ is 0.8.
ATP
- Primary and most usable form of energy in the body.
- Produced in the mitochondria.
- Powers enzymatic reactions, muscle contractions, and metabolic functions.
- Complete glucose oxidation with oxygen yields 38 ATP molecules.
Citric Acid Cycle (Krebs Cycle)
- Oxidative phosphorylation process resulting in complete glucose oxidation.
- Requires oxygen to produce 38 ATP.
- Anaerobic metabolism produces lactic acid, reducing HCO3 buffering capacity.
Arterial Blood Gas Sampling
- Requires a steady state for accurate interpretation.
- Ideally, wait 15-20 minutes after interventions for stabilization.
- Consider patient temperature during interpretation.
ABG Sampling Errors
- Air bubbles: PaCO2 tends toward zero, PaO2 rises to atmospheric levels.
- Delayed testing (over 30 min): Increased PaCO2, decreased pH, decreased PaO2.
- Heparin dilution: Decreased PaCO2 and pH.
- Venous sampling: Values do not reflect arterial blood.
Avoiding ABG Sampling Errors
- Choose a bounding artery with a strong, palpable pulse.
- Verify saturations with oximetry.
- Utilize proper needle size.
- Ensure adequate heparinization.
- Position the patient correctly.
- Obtain a sufficient sample size.
Oxygen Transport
- Oxygen in the blood is transported in two ways:
- Dissolved in blood plasma (0.003 mL O2/100 mL of blood/mmHg)
- Bound to hemoglobin (1.34 mL O2/g of Hb at 100% saturation)
- Total oxygen content is the sum of dissolved and combined oxygen.
Hemoglobin
- Each red blood cell contains about 280 million hemoglobin molecules.
- Heme group binds to oxygen molecules, allowing each hemoglobin molecule to carry four oxygen molecules.
- Normal hemoglobin levels:
- Men: 15 g/100 mL
- Women: 13-14 g/100 mL
Oxyhemoglobin Dissociation Curve
- Illustrates the relationship between the partial pressure of oxygen (PaO2) and hemoglobin saturation.
- Shifts in the curve reflect changes in hemoglobin's affinity for oxygen.
Shifts of the Curve
- Left shift: Increased affinity, better oxygen delivery to tissues.
- Right shift: Decreased affinity, less oxygen delivery to tissues.
2,3 Diphosphoglycerate (DPG)
- Organic phosphate group in erythrocytes.
- Binds to hemoglobin, reducing its affinity for oxygen.
- A rapid compensatory mechanism.
Hemoglobin Variants and Abnormalities
- Fetal hemoglobin: Higher affinity for oxygen than adults.
- Carboxyhemoglobin: CO binds to hemoglobin, preventing oxygen binding, resulting in reduced oxygen-carrying capacity.
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Description
Test your knowledge on Arterial Blood Gas (ABG) and metabolism concepts. This quiz covers important parameters like pH, PaCO2, HCO3, and their significance in diagnostics. Additionally, explore how metabolism interacts with energy generation and bodily functions through catabolism and anabolism.
