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Flashcards in ABGs Deck (17)
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1
Q

Why types of physiologic changes that occur with pH changes?

A

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
2
Q

What is the allen test?

A

-test collateral circulation to the hand prior to drawing a sample from the radial artery.

3
Q

What types of patients do we order ABG’s on?

A
  • 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
4
Q

WHat are the biological buffers put in place?

A
  • respiratory
  • renal
  • carbonic acid-bicarbonate
5
Q

Respiratory Buffer

  • fast or slow to modify?
  • acid or base buffer?
A
  • respiratory buffer response is fast, usually occurs within 1-3minutes
  • acid buffer.
6
Q

Renal Buffer

  • fast or slow to modify?
  • acid or base buffer?
A
  • metabolic changes that result in changes in pH take several days
  • basic buffer.
7
Q

If there is an increase in the H+ concentration in the blood what happens?

A

-Formation of carbonic acid, shift to the left.

8
Q

If H+ concentrations iin the blood drop below the desired level what happens?

A

-Carbonic acid dissociates, drives the equation to the right.

9
Q

WHat happens when CO2 levels increases? (which direction is the equation driven?)

A

-formation of more carbonic acid, drives equation to the right.

10
Q

Causes of Respiratory Acidosis with pH less than 7.35 and PaCO2 greater than 45

A
  • 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

11
Q

What are some cause of Metabolic Acidosis, HCO3 less than 22 with pH less than 7.35

A

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)

12
Q

What are some causes of respiratory alkalosis with pH greater than 7.45 and a PaCO2 less than 35?

A
  • 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)
13
Q

what are some causes of metabolic alkalosis with bicarb greater than 28 and pH greater than 7.45?

A

-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.
14
Q

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?

A
  • 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

15
Q

what is the probable cause of Hypoxemia with a normal A-a gradient?

A
  • hypoventilation

- high altitude

16
Q

what is the probable cause of hypoxemia with an increased A-a gradient?

A
  • Diffusion defect
  • ventilation-perfusion mismatch
  • right to left shunt
17
Q

What is V/Q mismatch?

What is the normal value?

What are the most common causes of Ventilation and Perfusion defects?

WHat is a high V/Q and low V/Q mismatch?

A
  • Ventilation = V Perfusion = Q
  • normal V/Q= 0.8
Causes: 
Ventilation: 
-COPD
-Asthma
-Pneumonia 

Perfusion:

  • PE
  • Pulm HTN
  • Cardiac arrest
  • High V/Q= greater than 0.8, Good ventilation and poor perfusion.
  • Low V/Q= less than 0.8, poor ventilation and good perfusion.