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Emergency Med > 13 - Acid Base Emergencies > Flashcards

13 - Acid Base Emergencies Flashcards

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

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

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

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

A
  • Treat underlying cause

- Adjust ventilation rate

23
Q

Metabolic alkalosis

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

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
Q

Causes of metabolic alkalosis

A
  • GI losses of acids
  • Loss of Chloride (CF)
  • Endocrine issues like Cushing’s
  • Drugs (diuretics, non-absorbable antacids)
  • Renal issues
26
Q

Treatment of metabolic alkalosis

A
  • Treat underlying cause
  • May have to replace K, Ca, Cl
  • Maybe dialysis
  • Maybe HCL, potassium sparing diuretics, ACE
27
Q

Metabolic acidosis (“bread and butter of acid base emergencies” – this is important)

A
  • 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
Q

We divide metabolic acidosis into 2 types

A
  • High Anion Gap

- Normal Anion Gap

29
Q

What’s an anion gap??

A
  • 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
Q

Anion gap example

A
  • Na = 135
  • Bicarb = 10
  • Cl = 98
  • Anion gap: 135 – 108 = 27 = high
31
Q

What causes normal gap metabolic acidosis? (not many – this is not common)

A
  • GI loss of bicarb (diarrhea)

- Kidneys are not making or not reabsorbing bicarb

32
Q

HIGH ANION GAP

A
  • ALMOST ALL METABOLIC ACIDOSIS WILL BE HIGH ANION GAP – KNOW THIS
33
Q

**High anion gap causes ** KNOW THIS

A
  • M = methanol
  • U = uremia
  • L = lactic Acidosis
  • E = ethylene glycol, EtOH
  • P = paraldehyde
  • A = ASA
  • K = ketoacidosis
34
Q

High anion gap

A
  • 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
Q

Obvious examples

A
  • 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
Q

Understanding ABGs

A
  • 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
Q

Step by step

A
  • 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
Q

Someone else’s way

A
  • 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
Q

Let’s try an easy one

A
  • 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
Q

Acute or chronic?

A
  • 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
Q

Another example… 75-year-old female with COPD

A
  • pH 7.37 (normal)
  • PCO2 55
  • HCO3 35
  • PO2 58
  • CO2 and bicarb both high = Compensated respiratory acidosis
42
Q

Overdose on a vent

A
  • 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
Q

Healthy teen vomiting for 4 days

A
  • 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
Q

16-year-old new diagnosis DM with vomiting and confusion

A
  • 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
Q

Compensated

A
  • 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
Q

Salicylate OD

A
  • 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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