ABG Flashcards
What does you use the Allen test for?
To ensure there is adequate circulation in the ulnar artery so that blood flow to the hand isn’t compromised when ABG is performed on the radial artery
What artery is typically used for ABG?
Radial artery
An ABG will tell you what? (3)
- Oxygenation
- Ventilation
- Acid-base balance
pO2 is used to determine what?
How well a pt is oxygenating (not used in determination of acid-base disturbances)
Is pO2 from pulse ox or ABG more reliable?
ABG
If pCO2 is high (>45) do you have acidosis or alkalosis?
Acidosis
If pCO2 is low (<35) do you have acidosis or alkalosis?
Alkalosis
If HCO3 is high (>26) do you have acidosis or alkalosis?
Alkalosis
If HCO3 is low (<22) do you have acidosis or alkalosis?
Acidosis
Is an ABN pCO2 reflective of a respiratory or metabolic problem?
respiratory
Is an ABN HCO3 reflective of a respiratory or metabolic problem?
metabolic
What is the tx for acid-base disturbance?
Treat the underlying disease causing the imbalance
Will the body be able to fully compensate for the disorder causing a pH imbalance?
No (won’t restore pH back to 7.4)
Are the lung or kidneys quick to respond to pH imbalance?
Lungs
How do the lungs compensate for a metabolic acid-base disturbance?
If pH is low (acidic), lungs will hyperventilate to blow of more pCO2 (blow off acid)
If pH is high (basic), lungs will hypoventilate to retain CO2 (retain acid)
Are the kidneys fast or slow to respond to respiratory acid-base imbalance?
Slow
How do the kidneys compensate for a respiratory acid-base disturbance?
If pH is low (acidic) will retain HCO3 (basic)
If pH is high (basic) will increase excretion of HCO3
What does it mean when you have an uncompensated state?
Primary defect in pCO2 or HCO3 WITHOUT a change in the other parameter
What does it mean when you have a compensated state?
Primary defect in pCO2 or HCO3 WITH a change in the other parameter
*pCO2 and HCO3 move in the same direction
What does a “partial” or “full” compensation refer to?
pH
What is a “full” compensation?
pH is restored to 7.35-7.45 (pt is compensating well)
What is a “partial” compensation?
pH is outside to 7.35-7.45 (pt is not compensating well)
When do you calculate an Anion gap?
If pt has a metabolic acidosis
What is your first step in determining if there is an acid-base disturbance?
Look at pH
Once you determine pt has acid or base disturbance by evaluating pH, what do you look at next?
HCO3 and PCO2 to determine what is the main cause
Respiratory acidosis will be due to pulmonary retention/impaired CO2 excretion. What are some of the major causes? (5)
- Lung/pleural disease (ex: COPD, airway obstruction, PE, pneumonia)
- Neuromuscular diseases (Gillian-Barre, Myasthenia gravis, spinal cord injury)
- Chest wall dysfunction
- Drug induced hypoventilation (opioids, benzos)
- CNS event, trauma
Pt presents with acute onset of dyspnea and in respiratory distress. On exam you find mental status changes, somnolence, hemodynamic instability. This presentation of sx is consistent with what? What acid-base disturbance are you concerned about?
Presentation of sx = hypercapnia
Concerned for respiratory acidosis
What is the tx for respiratory acidosis?
BiPAP (Bilevel Positive Airway Pressure) and respiratory support
Anxiety, fever, pain, sepsis, pregnancy, salicylate intoxication and high altitude can all cause what acid-base disturbance?
Respiratory alkalosis (hyperventilation)
Pt presents with tachypnea, palpitations, lightheadedness, and paresthesia’s. What acid-base disturbance are you concerned about?
Respiratory alkalosis
What is the range for a normal anion gap?
8-12 mmol/L
MUDPILES is the pneumonic for what? What does is stand for?
Elevated anion gap
Methanol Uremia (from renal failure) DKA (ketoacidosis) Propylene glycol Iron/isoniazid Lactate (lactic acidosis) Ethylene glycol Salicylate/starvation
Bicarbonate loss from: diarrhea, pancreatic drainage, GI fistulas, and renal tubular necrosis will have what effect on anion cap?
Will not effect anion gap
Pt presents with hyperventilation, tachycardia/arrhythmia and hyperkalemia. What acid-base disturbance are you concerned about?
Metabolic acidosis
Pt can also present with AMS
Kussmaul breathing is associated with what acidotic condition?
DKA
Treatment of underlying cause, dialysis, +/- bicarbonate therapy are tx for what acid-base disturbance?
metabolic acidosis
Caution w/ bicarbonate therapy. Can lead to hyponatremia and volume issues
With what acid-base disturbance do you check a urine chloride?
metabolic alkalosis
If urine chloride (metabolic alkalosis) is < 20 what do you suspect might be the cause? (2)
- GI loss (vomiting, NG suction)
2. Diuretics
Is a urine chloride < 20 responsive to fluid and Cl replacement?
yes
Sx due to volume contraction/dehydration
If urine chloride (metabolic alkalosis) is >20 what do you suspect might be the cause? (5)
- Hyperaldosteronism
- Cushings
- Renin secreting tumor
- Potassium depletion
- Citrate toxicity related to blood transfusion
Is a urine chloride > 20 responsive to fluid and Cl replacement?
No. Treat underlying cause, +/- potassium
Sx due to volume expansion/overload
Pt presents with reduced ventilatory rate, arrhythmia, hypokalemia. What acid-base disturbance are you concerned about?
Metabolic alkalosis
T or F: You can both metabolic alkalosis and acidosis at the same time
TRUE
T or F: you can have both respiratory alkalosis and respiratory acidosis at the same time?
FALSE. Can only have 1 respiratory disorder
How many acid base disturbances can you have at one time?
- metabolic alkalosis and acidosis, and 1 respiratory disorder
