ABGs Flashcards
Why types of physiologic changes that occur with pH changes?
Acidosis:
- decreased cardiac contractions
- decreased vascular response to catecholamines
- decreased respond to the effects of certain medications
Alkalosis:
- interferes with tissue oxygenation
- normal neurological and muscular function
What is the allen test?
-test collateral circulation to the hand prior to drawing a sample from the radial artery.
What types of patients do we order ABG’s on?
- critically ill
- impending or current respiratory failure
- sepsis
- multiorgan failure
- Drug overdose
- assessment of pt with chronic lung disease to evaluate level of CO2 retention
- carbon monoxide poisoning
WHat are the biological buffers put in place?
- respiratory
- renal
- carbonic acid-bicarbonate
Respiratory Buffer
- fast or slow to modify?
- acid or base buffer?
- respiratory buffer response is fast, usually occurs within 1-3minutes
- acid buffer.
Renal Buffer
- fast or slow to modify?
- acid or base buffer?
- metabolic changes that result in changes in pH take several days
- basic buffer.
If there is an increase in the H+ concentration in the blood what happens?
-Formation of carbonic acid, shift to the left.
If H+ concentrations iin the blood drop below the desired level what happens?
-Carbonic acid dissociates, drives the equation to the right.
WHat happens when CO2 levels increases? (which direction is the equation driven?)
-formation of more carbonic acid, drives equation to the right.
Causes of Respiratory Acidosis with pH less than 7.35 and PaCO2 greater than 45
- Central Nervous System depression: medications (narcotics, sedatives, anesthesia) or head injury
- Impaired respiratory muscle function: spinal cord injury, neuromuscular disease, neuromuscular blocking drugs
-Pulmonary disorders:
atelectasis, pneumonia, pneumothorax, pulmonary edema, bronchial obstruction
Hypoventilation d/t pain, chest wall deformity, abdominal distension, obesity
Trauma
What are some cause of Metabolic Acidosis, HCO3 less than 22 with pH less than 7.35
Renal failure
DKA
Diarrhea
Starvation
Salicylate intoxication*** PANCE!!!!
***the presence of metabolic acidosis should spur a search for hypoxic tissue somewhere in the body. (could be dead bowel, muscle tissue dying from ischemic leg)
What are some causes of respiratory alkalosis with pH greater than 7.45 and a PaCO2 less than 35?
- Psychological responses (anxiety or fear)
- pain
- increased metabolic demands (fever, sepsis, pregnancy, or thyrotoxicosis)
- medications (respiratory stimulants)
- central nervous system lesion (telling you to breathe really fast)
what are some causes of metabolic alkalosis with bicarb greater than 28 and pH greater than 7.45?
-either an excess of base or a loss of acid in the body
-excess base occurs from ingestion of:
antacids
excess use of bicarb
use of lactate in dialysis
-loss of acids can occur secondary to: protracted vomiting gastric suction hypochloremia excess administration of diuretics high levels of aldosterone.
what is the A-a gradient?
WHat is the normal range?
How do you calculate estimated A-a gradient?
How to calculate A-a gradient?
- the difference between oxygen tension in the alveoli (PAO2) and the arterial oxygen tension (PaO2)
- measures the integrity of the alveolar-capillary unit.
Normal: less than 10mmHg
How to measure estimated:
Age/4 + 4 = ___.
A-a gradient= PAO2-PaO2
what is the probable cause of Hypoxemia with a normal A-a gradient?
- hypoventilation
- high altitude
