Exam 2 Acid-Base Disorders [6/17/24] Flashcards
1
Q
In order to ensure optimal function of enzymatic function, acid-base balance is tightly regulated at what pH?
A
- 7.35 to 7.45
slide 2
2
Q
Change in relative concentrations of ____ and ____ change water ability to auto-ionize.
What is the purpose of this?
A
- fluid and electrolytes [Na, K, bicarb, H2O]
- ensures optimal enzymatic function
slide 2
1831 O’Shuaghnessy “loss of carbonate of soda” in cholera patients.
3
Q
Define acidemia
A
- Excess production of H+ (in relation to hydroxyl ions)
S3
4
Q
Define alkalemia.
A
- Excess production of OH- (in relation to hydrogen ions)
S3
5
Q
How is pH measured?
A
- Measured as H+ concentration pH
- The Power of Hydrogen
S4
6
Q
- The stability of pH is managed by what three factors?
- How do they enter and leave the body?
A
- CO2 (enters/leaves the body via lungs)
- HCO3 (enters/leaves the body via kidneys via proximal tubule)
- H+ (reabsorbed Via distal tubule and collecting duct)
S5
7
Q
What is the equation to calculate pH?
What is this equation called?
A
- pH = 6.1 + log [serum bicarb/(0.03 x PaCO2)]
- Henderson- Hasselbalch equation
coined acid-base balance
S5
8
Q
water is amphoteric meaning what?
A
- it can act as either an acid or a base
- HCl [acid] donates a proton to water [base]
- KOH [base] receives a proton from water [acid]
S6
9
Q
- How do we determine the strength of an acid or base?
- what is an example of a strong acid?
- what is an example of a weak acid?
A
- degree of dissociation in water determines strength
- lactic acid [pka 3.4] completely dissociates in water–> strong acid
- carbonic acid [pka 6.4] incompletely dissociates in water –> weak acid
S6
10
Q
What are the 3 rules for acid base?
A
-
electrical neutrality: of the negative and positively charged ions
- when we add all the cation and anions it should be equal
-
dissociation equilibria: the propensity to dissociate
- chunk of a substance put in water wants to break off into little pieces. Its tendency is to not stay as one solid
-
mass conservation: the amount of substance remains constant
- not insize, but in amount
S7
11
Q
What are the characteristics of strong Ions?
* dissociation?
* most abundant in ECF?
* others strong ions?
A
- dissociate completely
- Most abundant ECF strong ions: Na+ & Cl-
- others: K+, SO42-, Mg2+, Ca2+
S8
12
Q
- What is the formula for strong Ion difference [SID]?
- In ECF, is the SID + or -?
- SID is an independent predictor of?
A
- Total strong cations- Strong anions
- in ECF SID alway positvie
- an independent predictor of pH
S8
13
Q
How do you identify a pH disturbance?
A
- is ph increased or decreased?
- is PaCO2 and/or HCO3- increased or decreased from normal?
S9
14
Q
How can you tell if an acid-base disorder is a primary disorder with secondary compensation?
A
- Both PaCO2 and HCO3 change in the same direction
S9
15
Q
How can you tell if an acid-base disorder is a mixed acid/base problem?
A
- PaCO2 and HCO3 are in different directions.
S9
16
Q
What are normal values for:
* pH:
* PCO2:
* HCO3:
A
- pH: 7.35-7.45 [7.4]
- PCO2: 35-45 [40]
- HCO3: 22-28 [24]
S10
number in brackets is average number to use
17
Q
What is the Acid/Base Disorder
pH: 7.33
PCO2: 48
HCO3: 26
A
RR acidosis with partial compensation
- pH: low
- PCO2: high
- HCO2:Normal
S10
18
Q
What is the Acid/Base Disorder
pH: 7.58
PCO2: 35
HCO3: 29
A
metabolic alkalosis
- pH: high
- PCO2: normal
- HCO2: high
S10
19
Q
What is the Acid/Base Disorder
pH: 7.28
PCO2: 46
HCO3: 18
A
Mixed RR and metabolic acidosis
S10
20
Q
What is the Acid/Base Disorder
pH: 7.48
PCO2: 32
HCO3: 22
A
RR alkalosis with partial compensation
S10
21
Q
What are CV concesquences of acidosis?
A
- impaired contractility [7.2]
- decreased arterial blood pressure
- sensitive to re-entry dyshythmias
- decreased threshold for v-fib
- decreased responsivness to catecholamines [7.1]
IS DDD
S11
7.2 and 7.1 is the pH at which this occur
22
Q
What are nervous system consequences of acidosis?
A
- obtundation →
- coma
S12
23
Q
what are pulmonary consequences of acidosis?
A
- hyperventilation [to blow off CO2]
- dyspnea
- respiratory muscle fatigue
S13
24
Q
what are metabolism consequences of acidosis?
A
- hyperkalmeia
- insulin resisance
- inhibition of anaerobic glycolysis
S14
25
If your patient has normal lungs, what should their PaO2 be when they are on 60% FiO2?
* PaO2: 240 to 300 mmHg
Normal range of PaO2: 80-100 mmHg
FiO2 of room air is 21%
FIO2 of 60% is about 3x of room air.
PaO2 will be between 240-300 mmHg
| ?
26
Define Respiratory Acidosis
* An acute decrease in alveolar ventilation resulting in increase PaCO2
* pH < 7.35
* Caused by respiratory failure
| S15
27
What are the causes of Respiratory Acidosis?
* **Causes**:
* Drug-induced ventilatory depression [*prop, fent, NMBD, versed*]
* Malignant hyperthermia
* **inadequate NMBD reversal**
* Disorder of neuromuscular function
* Status asthmaticus
* Upper airway obstruction
* Permissive hypercapnia [*improper vent settings*]
* PNA/ Pulmonary Edema, Pleural Effusion
* Restriction of ventilation (rib fx, flail chest)
* **opioid excess**
* **CO2 insufflation**
PPROUDD MISC
Drugs MID SUPPR-OC cause respiratory acidosis
| S15
## Footnote
Causes Can be split into these categories:
* Central Ventilation Control
* Peripheral Ventilation Control
* VQ mismatch [airway problem]
*categories is on another card, just here as a reminder*
28
When does CO2 insufflation occur and how do you fix it?
in laparoscopic cases. The CO2 will need to be blown off the lungs, so adjust vent settings to help blow off CO2
| S15- lecture
29
⭐️What are the three categories that can cause Respiratory Acidosis?
* Central ventilation control (neuro/brain)
* Peripheral ventilation control (neuromuscular disease)
* V/Q Mismatch [Airway problem]
| S16
30
⭐️Slow shallow breathing is related to a central problem.
* What is this associated with?
* What is this due to?
* usually associated with somnolence
* D/T:
* residual opioids
* benzos
* propofol
| S16
31
⭐️rapid shallow breathing is related to a peripheral problem which is d/t what 3 main things?
* Neuromuscular
* residual NM blockade
* high epidural/spinal
* Throacic
* pneumothorax
* hemothorax
* V/Q mismatch
* abdominal splinting
* retained secretion
* atelactasis
| S16
32
⭐️obstructed breating is related to an airway problem which is d/t?
* Airway obstruction
* supraglottic
* glottic
* subglottic
* bronchospasm
| S16
33
# Acute Hypercarbia Compensation
* With acute hypercarbia, how long does it take for the bicarb to compensate for the acid-base disorder?
* For compensation to occur in acute hypercarbia, an increase in PaCO2 of 10mmhg should increase the HCO3 by how much?
* Very slowly (2-3 days)
* Increase in 1 mEq/L of HCO3 for every 10 mmHg of PaCO2
| S17
34
# Chronic Hypercarbia
For compensation to occur in chronic hypercarbia, an increase in PaCO2 of 10mmhg should increase the HCO3 by how much?
* ↑ PaCO2 of 10 mmHg = ↑ HCO3- by 3 mEq/L
| S17
## Footnote
This is prevalent in COPD patients
35
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
* What is the expected HCO3 if this patient has compensated acute hypercapnia?
* Normal PaCO2 level: 40 mmHg
* Normal HCO3 level: 24 mEq/L
* PaCO2 increased by 40 mmHg
* For acute hypercapnia, ↑PaCO2 of 10 mmHg=↑HCO3- of 1 mEq
**Answer: 28meq/L**
| S18
36
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
* What is the expected HCO3 if this patient has compensated chronic hypercapnia?
* Normal PaCO2 level: 40 mmHg
* Normal HCO3 level: 24 mEq/L
* PaCO2 increased by 40 mmHg
* Chronic Hypercapnia: ↑PaCO2 10 mmHg=↑HCO3- 3 mEq
* HCO3- increase by 12 mEq/L
**Answer: 36 mEq/L**
| S18
37
What would be the treatment for respiratory acidosis if hypercarbia is marked and CO2 narcosis is present?
## Footnote
*Narcosis: a state of stupor, drowsiness, or unconsciousness produced by drugs.*
* Mechanical Ventilation
* Increase minute ventilation by ↑ tidal volume, ↑ respiratory rate, or both.
| S19
38
Why should there be caution with chronic hypercarbia reversal with bicarb?
* Excessive bicarb will cause CNS irritability leading to seizures
| S19
39
* when should you be cautious when giving bicarb?
* when can you give bicarb?
* **Bicarb should not be 1st line of tx if pt has:**
* RR acidosis w/ metabolic compensation [high bicarb level]
* Mixed Acidosis
* **Bicarb can be given**
* when there is data that proves it’s metabolic acidosis.
| S19 - lecture
40
Define Metabolic Acidosis.
* A lowered blood pH which stimulates the respiratory center to hyperventilate
* Metabolic Acidosis is secondary to an underlying disorder (fix the problem to fix acidosis)
| S20
## Footnote
Respiratory compensation does not fully counter excessive acid production
41
What are causes of metabolic acidosis?
* increased production of acid
* decreased excretion of acid
* acid ingestion
* renal/GI bicarbonate losses
| S20
42
What 3 things is metabolic acidosis associated with?
* alteraration in transcellular ion pumps
* ↑ ionized calcium
* right shift of oxyhgb curve
| S20
43
What direction will the Oxygen-Hemoglobin Dissociation Curve shift with Metabolic Acidosis?
* Rightward Shift [decreased affinity for O2]
* This will allow O2 to be released and available to the tissues
*
| S20
44
What is the formula to determine if the body is compensating for acute metabolic acidosis?
* (1.5 x HCO3) + 8
or
* for evey 1 mEq/L ↓ in BE, PaCO2 should fall 1.2 mmhg
45
What is your expected PaCO2 if your HCO3- is 12 mEq/L?
* PaCO2 = 26 mmHg
* If PaCO2 is >26 mmHg, compensation is INADEQUATE
PaCO2 = (1.5 x HCO3-) + 8
= (1.5 x 12) + 8
= 26 mmHg
| S21
46
For every 1 mEq/L of ↓ base excess, PaCO2 should fall ______ mmHg.
* 1.2 mmHg
*otherwise compensation is inadequate*
| S21
47
# normal anion gap
* A normal anion gap maintains __________.
* Electrical neutrality
* Na balanced by sum of bicarb and chloride.
| S22
48
# normal anion gap
Bicarb loss is countered by?
What is this called?
* Bicarb loss is countered by **net gain of chloride ions**
* This is often called hyperchloremic acidosis
| S22
49
Factors that cause metabolic acidosis with a normal anion gap.
* Sodium Chloride Infusion
* Diarrhea
* Early Renal Failure
| S22
50
* What is the simple anion gap formula?
* What is the range of a simple anion gap?
* Sodium - (Chloride + Bicarb)
* 12-14 mEq/L
| S23
51
What is the conventional anion gap formula?
What is the range of a conventional anion gap?
* (Sodium + Potassium) - (Chloride + Bicarb)
* 14-18 mEq/L
| S23
52
* What does the anion gap underestimate?
* What is it complicated by?
* frequently underestimates extent of disturbance
* complicated by hypoalbuminemia, hypophosphatemia
| S23
53
What defines a high anion gap?
* Additional acid that is added to extracellular space
* Acids dissociates into H+ that combine with bicarb to form carbonic acid that decrease available bicarb
* Anion Gap >20
| S24
54
Causes of high anion gap.
* Lactic Acidosis
* Ketoacidosis
* Renal Failure
* Poisoning
| S24
55
Mnemonic for anion gap acidosis
* C: cyanide and CO
* A: arsenic
* T: toluene
* M: methanol, metformin
* U: uremia
* D: DKA
* P: paraldehyde
* I: iron
* L: lactate
* E: ethylene glycol
* S: salicylates
| S25
56
What is lactic acidosis?
* Marker of critical ilnnes
* over production vs inadequate clearance of lactic acid
* presistent acidosis
| S26
57
where does lactic acid come from?
* degradation product of glucose metabolism
* excess catecholamines degrades to lactacte --> pyruvate --> gluconeogeniss [*produce more sugar for energy*]
* anerobic
* aerobic
* buffer in isotonic solutions
| S26
58
⭐️Decision tree for lactic acidosis
**LOOK AT**
1. What is the lactate level? What is the pH?
2. how is the heart ? [CO, SV, CVP, SVO2?]
3. Low or normal
4. Diagnosis
| S27
59
How do you treat metabolic acidosis?
* Treat the cause!
| S28
60
Treatment for Metabolic Acidosis related to Ketoacidosis.
* Insulin
* fluids
| S28
61
Treatment for Metabolic Acidosis related to Lactic Acidosis.
* Improve tissue perfusion
* fluid resuscitate
* discontinue metformin
| S28
62
Treatment for Metabolic Acidosis related to Renal Failure.
* Dialysis
| S28
63
What are the parameters for the treat metabolic acidosis with sodium bicarbonate?
* pH < 7.1
* HCO3- < 10 mEq/L
*very controversial bc we dont want a metabolic alkalosis shift*
| S29
64
What are the effects of administering bicarb to someone with metabolic acidosis?
* Bicarb will react with H+ ion and generate CO2 which will diffuse intracellularly and **decrease pH**
* In chronic metabolic acidosis, acute pH changes negate the right shift of ocyhemoglobin curve (Bohr effect) and cause **tissue hypoxia**
| S29
## Footnote
The administration of IV NaHCO3 to treat metabolic acidosis should be reserved for the emergency treatment of select conditions
65
What is the formula for a full correction dose of bicarb?
* Full correction dose(mmol)
* 0.3 x Base Deficit (mmol/L) xWt(kg)
* Give half this dose and reassess
| S29
66
What happens to elective surgery if the patient experience acute metabolic acidosis?
* Surgery will be postponed
| S30
67
Anesthesia management considerations for urgent/emergent surgery with metabolic acidosis.
* Hemodynamic monitoring [Swann, SVV line, Art Line]
* Give Fluids
* Monitor Cardiac Functions
* Frequent Lab
* *Uphill battle, be honest with family members*
| S30
68
Define Respiratory Alkalosis.
* An acute increased alveolar ventilation
* Results in ↓ PaCO2 and pH > 7.45
| S31
69
What are the causes of Respiratory Alkalosis?
* Pregnancy
* High Altitude (↑RR)
* Salicylate overdose (asprin)
* Iatrogenic hyperventilation (during perioperative period/ fear)
I SHIP the causes of respiratory alkalosis
| S31
70
What are the symptoms of Respiratory Alkalosis?
* Decrease PaCO2 will cause vasoconstriction:
* Lightheadedness
* Visual disturbance
* Dizziness
| S32
71
Respiratory Alkalosis will result in greater binding of calcium to ________.
* Albumin
*Patient will be hypocalcemic.*
| S32
72
What are the signs and symptoms of hypocalcemia?
* Paresthesia, muscle spasm, cramp, tetany, circumoral numbness, seizures
* Trousseau's sign
* Chvostek's sign (Irritability on the facial nerve)
| S32
73
How many branches of the facial nerve are there?
Name them :)
**Five Branches**
* Temporal
* Zygomatic
* Buccal
* Mandibular
* Cervical
| additional info
## Footnote
*Two Zebras Bit My Chicken*
74
Anesthesia management of respiratory alkalosis.
* Consider what is causing the hyperventilation (anxiety, pain, full bladder, agitation)
* Poor mechanical ventilation strategy
* Therapeutic Hyperventilation
| S33
75
Define Metabolic Alkalosis.
* Marked increase in plasma bicarb usually compensated by an increase in CO2
| S34
76
Metabolic Alkalosis is usually ____ and has ____ or ____ causes from what?
* Usually iatrogeninic: Renal or extrarenal causes
* Net loss of H+ or a net gain of bicarb
* excess citrate
| S34
77
What are other names for Metabolic Alkalosis?
* Volume depletion alkalosis
* Volume overload alkalosis
| S34
78
What are the causes of Metabolic Alkalosis?
* Hypovolemia
* Bicarb administration
* Hyperaldosteronism (Conn's ↑ Na+, ↓ K+)
* Vomiting
* NG suction
* Diuretic Therapy
High Bicarb Has Very Nasty Damage
| S35
79
What are the symptoms of metabolic alkalosis?
* lightheadnedness
* tetany
* paresthesia
**also due to hypocalcemia [like RR alkalosis]
| S35
80
Treatment for Metabolic Alkalosis?
* Treat the cause!
| S36
81
Treatment for Metabolic Alkalosis related to volume depletion.
* Saline fluid resuscitation
| S36
82
Treatment for Metabolic Alkalosis related to gastric loss.
* Proton Pump Inhibitors
| S36
83
Treatment for Metabolic Alkalosis related to loop diuretics.
* Potassium-sparing diuretics (Spironolactone)
| S36
