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Emergency Med > 13 - Acid Base Emergencies > Flashcards

13 - Acid Base Emergencies Flashcards

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1
Q

Case study

A

o 16-year-old with recent ankle break, found unarousable and nausea
o History of weight loss, depression, increased food intake, thirst

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2
Q

Differential

A 
o	Thyroid (high pulse, anxiety)
o	DKA
o	Pregnancy 
o	Infection
o	Anxiety
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3
Q

Labs

A 
o	Pregnancy test
o	CMP (sodium normal, potassium high, bicarb low, creatinine high means mild renal failure, acidotic) 
o	CBC (+/- cultures, +/- lactic acid) 
o	Urine drug screen 
o	Blood drug screen (salicylate, alcohol, acetaminophen) 
o	Arterial blood gas 
o	Serum ketones 
o	Urinalysis (ketones, UTI)
o	HbA1c, TSH
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4
Q

Diagnosis

A

o Classic presentation of DKA

o Need to give fluids, insulin bolus then drip, etc.

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5
Q

Arterial blood gas (ABGs)

A 
A very fast lab (minutes for results) that reads blood directly from artery sample.
o	pH 
o	Oxygenation
o	Ventilation
o	Bicarb
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6
Q

You can get blood gasses other ways

A

VBG
o pH accurate
o PCO2 close
o PO2 unreliable

CBG (used in kids)
o pH accurate
o PCO2 add 5
o PO2 unreliable

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7
Q

Basic abnormalities in ABGs

A
  • Metabolic Acidosis
  • Metabolic Alkalosis
  • Respiratory Acidosis
  • Respiratory Alkalosis
  • Mixed
  • Compensated
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8
Q

Acidosis and alkalosis

A
  • Acidosis – the gain of too many acids OR loss of too many bases
  • Alkalosis – the gain of too many bases OR the loss of too many acids
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9
Q

When to order ABGs

A
  • Vent management
  • Unknown disorder
  • Unknown OD or known OD that causes acid base issues
  • When on fence about admission status
  • Suspected DKA
  • Code decisions
  • Will it change the plan????
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10
Q

Buffer system

A
  • The renal system compensates for respiratory and the respiratory for the renal.
  • Although many other systems, primarily done through bicarb and CO2
  • Respiratory system is fast to kick in but the renal system is not
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11
Q

pH imbalances

A
  • PH imbalances occur when a disturbance overwhelms the buffering systems
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12
Q

Clinical manifestations

A
  • Hypercapnea (Respiratory Acidosis) – altered mental status, delirium, HA, dyspnea
  • Hypocapnea (Respiratory Alkalosis) – lightheaded, nausea, tachycardia, carpel spasm/tingling
  • Acidemia (Metabolic Acidosis) – deep/fast breathing, pale/clammy, often combative then delirious
  • Alkalemia (Metabolic Alkalosis) – tingling, tetany, seizures, delirium
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13
Q

Respiratory acidosis – VERY COMMON ***

A
  • Acute – due to decreased respiratory rate or function, so CO2 builds. Causes – head trauma, med OD, vent settings, pulmonary issues (PE, pneumonia)
  • Chronically – due to lung/body issue so cannot get rid of CO2 (dead space) – VERY common COPD, pregnancy, obesity
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14
Q

Buffering respiratory acidosis

A
  • As CO2 increases, kidneys reabsorb bicarb in an attempt to compensate. See big swing in ph initially
  • Eventually more secondary buffering systems engage, and the ph becomes more normal.

Formulas
o Change in pH = 0.8 X change in paCO2 (Acute respiratory acidosis)
o Change in pH = 0.3 X change in paCO2 (Chronic respiratory acidosis)

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15
Q

Example

A
  • PaCO2 of 60 – what ph changes would you expect?
  • 60 – 40 (normal CO2) = 20 (change in CO2)
    o 20 X .8 = 16 gives ph of 7.19 (acute)
    o 20 X .3 = 6 gives ph of 7.29 (chronic)
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16
Q

Respiratory acidosis treatment = Correct underlying cause…

A
  • Narcan (narcotic OD)
  • Chest tube (pneumothorax)
  • Vent (increase respiratory rate)
  • Careful with O2 and CO2 retainers
  • BiPAP and CPAP
  • Nebulizers, steroids, diuretics
  • Even intubation seems to help when things are severe
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17
Q

Respiratory alkalosis

A
  • Due to hyperventilation (getting rid of too much CO2)
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18
Q

** Causes of respiratory alkalosis ** KNOW THIS

A
  • ** Anxiety/pain = MOST COMMON **
  • Vent settings (rate too high)
  • Fever
  • Sepsis (gram negatives) KNOW THIS
  • OD (aspirin especially)
  • Head trauma
  • Lung issues (PE, pneumothorax)
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19
Q

Acute vs chronic

Study These Flashcards
A
  • In acute situations, the low PaCO2 will cause a big shift in pH, while in chronic situations the pH becomes more normal because the buffering systems have time to kick in.
20
Q

Acute alkalosis

Study These Flashcards
A
  • In acute respiratory alkalosis, the bicarbonate concentration level decreases by 2 mEq/L for each decrease of 10 mm Hg in the PaCO2 level
21
Q

Chronic alkalosis

Study These Flashcards
A
  • In chronic respiratory alkalosis, the bicarbonate concentration level decreases by 5 mEq/L for each decrease of 10 mm Hg in the PaCO2 level
  • Plasma bicarbonate levels rarely drop below 12 mm Hg
22
Q

Respiratory alkalosis treatment

Study These Flashcards
A
  • Treat underlying cause

- Adjust ventilation rate

23
Q

Metabolic alkalosis

Study These Flashcards
A
  • Metabolic loss of hydrogen or gain in bicarb
  • Can have high mortality if pH >7.65
  • Goes along with low Ca, low K
24
Q

Rise in bicarb

Study These Flashcards
A
  • If see a rise in bicarb, could be respiratory acidosis or metabolic alkalosis…rarely see bicarb >35 in respiratory acidosis because the compensation mechanisms have limits
25
Causes of metabolic alkalosis
- GI losses of acids - Loss of Chloride (CF) - Endocrine issues like Cushing's - Drugs (diuretics, non-absorbable antacids) - Renal issues
26
Treatment of metabolic alkalosis
- Treat underlying cause - May have to replace K, Ca, Cl - Maybe dialysis - Maybe HCL, potassium sparing diuretics, ACE
27
Metabolic acidosis (“bread and butter of acid base emergencies” – this is important)
- Caused by increase of acids or loss of bases | - Unlike respiratory acidosis, in metabolic acidosis there are a number of different acids that maybe increased
28
We divide metabolic acidosis into 2 types
- High Anion Gap | - Normal Anion Gap
29
What’s an anion gap??
- Some anions and cations we can measure…others we can’t - We have a formula that will show an increase when there is an excess of unmeasured acids - Normal anion gap is 8 to 12****** - Na – (Cl + bicarb)******
30
Anion gap example
- Na = 135 - Bicarb = 10 - Cl = 98 - Anion gap: 135 – 108 = 27 = high
31
What causes normal gap metabolic acidosis? (not many – this is not common)
- GI loss of bicarb (diarrhea) | - Kidneys are not making or not reabsorbing bicarb
32
HIGH ANION GAP
- ALMOST ALL METABOLIC ACIDOSIS WILL BE HIGH ANION GAP – KNOW THIS
33
***High anion gap causes *** KNOW THIS
- M = methanol - U = uremia - L = lactic Acidosis - E = ethylene glycol, EtOH - P = paraldehyde - A = ASA - K = ketoacidosis
34
High anion gap
- Either kidneys can’t get rid of acids (like phosphate) - Or body over producing acids - Almost all Metabolic Acidosis is High Anion Gap types - Usually the cause is pretty obvious
35
Obvious examples
- 85 y/o female confused, high WBC, fever 101 and UTI - 56 y/o male with BS of 980, breathing hard, pale, sweaty, irritable - 90 y/o with diagnosis of acute bowel ischemia
36
Understanding ABGs
- Is pH high or low? - Do CO2 and bicarb go in same direction (both high or both low)? o In a normal situation, they should either both be high or both be low - If pH is normal is it compensated or mixed? - If CO2 and bicarb in opposite directions, mixed (one high one low)
37
Step by step
- Look at pH – is it acidic or basic? - Look at CO2 and bicarb – are they both high or both low o If acidic, is it caused from too many acids or not enough bases? o Is the cause respiratory (CO2) or metabolic (bicarb)?
38
Someone else’s way
- Follow the CO2 - When the CO2 and the pH move in the same direction (both low or both high) it is metabolic - When the CO2 and the pH move in opposite directions (one high and one low) it is respiratory
39
Let’s try an easy one
- 55 y/o with pneumonia, sleepy – thinking respiratory acidosis - pH 7.15 (acidosis) - pCO2 70 (35-45) – high - HCO3 30 (21-28) – high - pH is low – so acidodic - Bicarb and CO2 both high (normal response) - There is too much acid AND too much base - Only one that could cause acidosis is too much acid which is CO2 which is respiratory - OR CO2 and pH in opposite direction so respiratory
40
Acute or chronic?
- 70 (Co2) -40 = 30 - 30 x 0.8= 24 (7.40 - .24) - 30 x 0.3 = 9 (7.40 - .09) - Is pH closer to 7.16 or 7.31? - Lower pH, bigger swing so acute - Acute problem because it is closer to 7.16
41
Another example… 75-year-old female with COPD
- pH 7.37 (normal) - PCO2 55 - HCO3 35 - PO2 58 - CO2 and bicarb both high = Compensated respiratory acidosis
42
Overdose on a vent
- pH 7.54 - PCO2 19 - HCO3 16 - Alkalosis - Low acid from respiratory (blowing off too much CO2) - What should they do to vent setting? Turn it down
43
Healthy teen vomiting for 4 days
- pH 7.50 - PCO2 50 - HCO3 50 - pH HIGH; CO2 high so is bicarb…which will cause alkalosis? - What does she need for treatment?? - High bicarb is causing the alkalosis, so she needs fluids
44
16-year-old new diagnosis DM with vomiting and confusion
- pH 7.20 - PCO2 20 - HCO3 12 - Expected BS? High - K+?? High - Expected anion gap? Yes - Treatment? First fluids, then supplement potassium because after you give fluids it will start to correct itself
45
Compensated
- pH will be normal – look at ph and which direction it “leans” - Again, look at CO2 and bicarb for cause - Basically if they are compensated leave them alone - ***NOTE: if the pH is in the normal range on the exam, say COMPENSATED***
46
***Salicylate OD***
- Shows up on Board questions - ***Respiratory Alkalosis and Metabolic Acidosis*** - Initially the respiratory center is stimulated causing rapid RR giving respiratory alkalosis - Then inhibition of citric acid cycle so accumulation on acids leads to metabolic acidosis - Aspirin, Ben Gay - Nausea, ***tinnitus*** initially - Then can get changes in vitals (***tachypnea, tachycardia, hyperthermia***) - MS changes (agitation to lethargy)

Emergency Med (14 decks)

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