ABGs

Question 1

Arteries to get ABGs from?

Answer 1

• radial artery should be 1st choice: superficial, easily compressed
• other arteries: femoral and brachial

Question 2

What can acidosis cause?

Answer 2

• decreased force of cardiac contraction
• decreased vascular response to catecholamines
• decreased response to effects and action of certain meds

Question 3

What can alkalosis interfere w/?

Answer 3

• tissue O2

- neuro and muscle fxn

Question 4

O2-Hgb dissociation?

Answer 4

• Bohr effect: increased CO2 = decreased pH
• when pH changes - that changes binding of O2
• lower the pH the curve moves right, allows O2 to dissociate easier
• left shift (alkalosis): O2 doesn’t unload as well

Question 5

What controls the pH?

Answer 5

• diet
• metabolic prod of CO2
• regulation through GI tract
• influence of other lytes
• buffers

Question 6

3 systems that maintain pH?

Answer 6

- chemical buffering: 
carbonic acid (main buffer) - CO2 is best transported as HCO3- (as CO2 increases so does H+) 
phosphate
plasma proteins
- resp center
- kidneys

Question 7

How does resp buffer work?

Answer 7

• conc. of CO2, carbonic acid, and HCO3 will trigger resp center
• RR and tidal vol will be altered to either increase or decrease ventilation
• response occurs in 1-3 min

Question 8

How does renal buffer work?

Answer 8

• kidneys can excrete either acid or alkaline urine, thereby adjusting pH of blood:
  excrete or retain HCO3- and H+
  if blood pH decreases then bicarb would be retained to balance out acidity)
• response takes over hours or even days, but represents a more powerful regulatory system

Question 9

Onset of action of buffer systems?

Answer 9

• chemical buffer systems occur almost immediately

- respiratory and renal systems act more slowly than chemical buffers, have more capacity than chemical buffers

Question 10

Causes of resp acidosis?

Answer 10

• CNS depression: meds - narcotics, sedatives, anesthesia
• impaired muscle fxn: spinal cord injury, neuromuscular diseases, or neuromuscular blocking drugs
• pulm disorders: atelectasis, pneumonia, pneumothorax, pulmonary edema, bronchial obstruction
• massive PE
• hypoventilation due to pain, chest wall injury, or abdominal pain

Question 11

S/S of resp acidosis?

Answer 11

• resp: dyspnea, resp distress, and/or shallow respiration
• nervous: HA, restlessness and confusion: if CO2 level extremely high drowsiness and unresponsiveness may be noted (hypoxic)
• CVS: tachycardia and dysrhythmias

Question 12

Management of respiratory acidosis?

Answer 12

• increase ventilation
• causes that can be tx rapidly: pneumo, pain and CNS depression due to med
• if cause can’tbe readily resolved then will reqr mechanical ventilation

Question 13

Causes of resp alkalosis?

Answer 13

• psych responses, anxiety or fear
• pain
• increased metabolic demads: fever, sepsis, preg, or thyrotoxicosis
• meds: resp stimulants
• CNS lesions

Question 14

S/S of resp alkalosis?

Answer 14

• CNS: light headedness, numbness, tingling, confusion, inability to concentrate and blurred vision
• dysrhythmias and palpations
• dry mouth, diaphoresis and tetanic spasms of arms and legs

Question 15

Management of resp alkalosis?

Answer 15

• resolve underlying problem
• monitor for resp muscle fatigue
• when resp muscles become exhausted, acute resp failure may ensue

Question 16

Causes of metabolic acidosis?

Answer 16

• renal failure
• DKA
• anaerobic metabolism (tissue death, lactic acidosis)
• starvation
• salicylate intoxication
• sepsis

Question 17

MUDPILES?

Answer 17

increased anion gap metabolic acidosis

• M: methanol intoxication
• U: uremia
• D: diabetic or alcoholic ketoacidosis
• P: paraldehyde
• I: isoniazide or Fe overdose
• L: lactic acid
• E: ethylene glycol intoxication
• S: salicylate overdose

Question 18

USED CAR?

Answer 18

non-anion gap metabolic acidosis:

• U: ureteral - sigmoid diversions - reabsorb Cl-, H2O in intestine - secrete bicarb in intestine
• S: small bowel fistula, saline admin
• E: endocrinopathies: addison’s, hyperparathyroidism
• D: diarrhea
• C: carbonic anhydrase inhibitors
• A: hyperalimentation (tPA)
• R: renal tubular acidosis

Question 19

S/S of metabolic acidosis?

Answer 19

• CNS: HA, confusion, restlessness progressing to lethargy, stupor or coma
• CVS: dysrhythmias
• KUssmaul’s respirations (big deep fast resp)
• warm, flushed skin as well as nausea and vomiting

Question 20

Tx of metabolic acidosis?

Answer 20

• tx cause
• hypoxia of any tissue bed will produce metabolic acids as result of anaerobic metabolism even if paO2 is normal
• restore tissue perfusion to hypoxic tissues
• use of bicarb is indicated
• hydration

Question 21

Causes of metabolic alkalosis?

Answer 21

• ingestion of excess antacids, excess use of bicarb, or use of lactate in dialysis
• protracted vomiting, gastric suction, hypochloremia, excess use of diuretics or high level of aldosterone

Question 22

S/S of metabolic alkalosis?

Answer 22

• CNS: dizziness, lethargy, disorientation, seizures, and coma
• M/S: weakness, muscle twitching, muscle cramps and tetany
• nausea, vomiting, resp depression
• diff to tx

Question 23

Base excess?

Answer 23

• amt of excess or insufficient level of bicarb:
• 2 to +2 mEq/L
• negative base excess indicates a base deficit in blood
• it is an est of amt of strong acid or base needed to correct metabolic component of acid base disorder

Question 24

Major anion in ECF?

Answer 24

• Cl: it helps maintain osmotic pressure of blood
• when acidosis occurs, fewer Cl- are reabsorbed
• other anions have transport maximums and excesses are excreted in urine

Question 25

What is the anion gap?

Answer 25

- unmeasured anions = proteins, phosphates, citrate, sulfate - normal is equal to 12

Question 26

``` pt admitted for severe asthma attack, been having increasing SOB since admission 3 hrs ago ABGs: pH 7.22 paCO2: 55 HCO3: 25 DX? Tx? ```

Answer 26

- resp acidosis | - need to improve ventilation and O2 by admin bronchodilators, O2, possible mechanical ventilation

Question 27

``` 55 admitted w/ recurring bowel obstruction has been experiencing intractable vomiting for last several hours: pH: 7.5 paCO2: 42 HCO3: 33 Dx? Tx? ```

Answer 27

- metabolic alkalosis | - tx: IV fluids, measures to reduce excess base

Question 28

When does compensation occur in primary resp acidosis?

Answer 28

- when kidneys retain HCO3

Question 29

``` Pt on hemodialysis and has missed her last 2 appts ABG: pH 7.32 paCO2 32 HCO3 18 paO2 88 Dx? ```

Answer 29

- partially compensated metabolic acidosis

Question 30

``` Pt w/ hx of COPD presents for resting ABG prior to PFTs: pH 7.35 paCO2 48 HCO3 28 PaO2 90 Dx? ```

Answer 30

fully compensated resp acidosis

Question 31

``` pH 7.51 PaCo2 50 HCO3 40 PaO2 40 (21% O2) Dx? ```

Answer 31

- metabolic alkalosis w/ partial resp compensation