PHRM 825: Acid-Base Balance - Metabolic Disorders Flashcards
(108 cards)
1
Q
Metabolic acidosis is characterized by what 3 things?
A
- Low pH (<7.35)
- Low serum HCO3- (<24 mEq/L)
- A compensatory decrease in PaCO2 from hyperventilation
2
Q
2 classifications of metabolic acidosis
A
- Non-anion gap metabolic acidosis
- Anion gap metabolic acidosis
3
Q
Anion gap equation
A
Anion gap = Na+ - (Cl- + HCO3-)
Key cations - Key anions
4
Q
Normal anion gap value
A
3-11 mEq/L
5
Q
Why is there not a gap in non-anion gap acidosis?
A
The loss of plasma HCO3- is replaced by Cl-
6
Q
Non-anion gap acidosis is also known as
A
Hyperchloremic acidosis (elevated Cl- prevents the gap)
7
Q
Causes of non-anion gap acidosis
A
- Gastrointestinal bicarbonate losses
- Renal bicarbonate loss
- Reduced renal H+ excretion
- Acid and chloride administration
8
Q
Gastrointestinal bicarbonate losses are caused by
A
Diarrhea and pancreatic fistulas/biliary drainage
9
Q
Diarrhea is a common cause of what
A
Non-anion gap acidosis (hyperchloremic acidosis)
10
Q
Diarrhea contains a large amount of what
A
HCO3-
11
Q
Pancreatic fistulas and biliary drainage are rich in what
A
HCO3-
12
Q
What does RTA stand for?
A
Renal tubular acisosis
13
Q
Type II RTA occurs in which tubule?
A
Proximal
14
Q
Which type of RTA causes renal bicarbonate loss?
A
Type II
15
Q
What causes renal bicarbonate loss?
A
Various diseases or toxins (heavy metal toxicity, carbonic anhydrase inhibitor therapy, topiramate, etc.)
16
Q
During renal bicarbonate loss, reabsorptive threshold for HCO3- is ____ in the proximal tubule
A
Reduced
17
Q
What percentage of filtered bicarbonate is normally absorbed in the proximal tubule?
A
~85%
18
Q
With enhanced bicarb loss, there will be increased ___ and ___ loss
A
Na+ and fluid
19
Q
During bicarb loss, Na and water are also lost which activates the ____ system and leads to ____
A
renin-angiotension system; secondary hyperaldosteronism
20
Q
Increased aldosterone augments ____ excretion, causing ___
A
K+; hypokalemia
21
Q
Are patients still able to acidify their urine in response to an acid load during renal bicarb loss?
A
Yes
22
Q
Type I RTA occurs in which tubule?
A
distal
23
Q
Type IV RTA occurs in which tubule?
A
distal
24
Q
Type I RTA is also know as what?
A
Hypokalemia RTA
25
Type IV RTA is also known as what?
Hypoaldosteronism or hyperkalemia RTA
26
What causes type I RTA?
- Primary tubule defect
- SLE (lupus)
- Myeloma
- Sickle cell
- Li+
- Ampho B
- Toluene
27
During Type I RTA, what cannot be pumped into tubule lumen by cells of collecting duct?
H+
28
During type I RTA, what happens to urine?
It cannot be maximally acidified (pH>5.3)
29
During type IV RTA, there is less aldosterone, causing retention of what?
H+
30
During type IV RTA there are hyperkalemic conditions that lead to ____ retention, causing ___.
H+ retention; acidosis
31
During chronic renal failure, there is ____ H+ secretion and less ___ production
less; amonia
32
Excess administration of what can cause non-anion gap metabolic acidosis?
- TPN
| - HCl or Ammonium Cl
33
During anion gap metabolic acidosis, HCO3- losses are replaced with what?
Another anion besides Cl-
34
What is the delta gap?
Difference between the patient's anion gap and the normal anion gap
35
Causes of anion gap metabolic acidosis
- Lactic acidosis
- Ketoacidosis
- Drug intoxication
36
What is the most common cause of anion gap acidosis?
Lactic acidosis
37
Lactate is a normal product of ___ metabolism
anaerobic
38
Lactate formation is essential for tissues that need ____ to produce energy anaerobically
NAD+; anaerobically
39
Which tissues need NAD+ to generate energy anaerobically?
- RBCs
| - Exerciseing muscle
40
Lactate normally enters the circulation in ____ amounts and is promptly removed by the ___
small; liver
41
Increased blood levels of lactate almost always result from what?
Decreased clearance (not overproduction)
42
What is lactate converted to when it is eliminated?
Pyruvate
43
What will happen if there is persistent failure to oxidize lactic acid?
The buffering capacity will be exhaused
44
Possible causes of lactic acidosis include (8)
- Shock
- Drugs/toxins
- Seizures
- Leukemia
- Hepatic/renal failure
- Diabetes mellitus
- Malnutrition
- Rhabdomyolysis
45
What drugs/toxins cause lactic acidosis?
- Ethanol
- Metformin
- Nucleoside reverse transcriptase inhibitors (NRTIs)
- Linezolid, isoniazid, propofol
- Propylene glycol
46
How does ethanol cause lactic acidosis?
Increases lactate and causes hypoglycemia impaired gluconeogenesis
47
How does metformin cause lactic acidosis?
Mechanism is unclear
48
How do NRTIs cause lactic acidosis?
Inhibit DNA polymerase, which is responsible for mitochondrial DNA synthesis
49
How do linezolid, isoniazid, and propofol cause lactic acidosis?
Increase lactic acid
50
How does propylene glycol cause lactic acidosis?
Propylene glycol is metabolized to lactic acid
51
How do seizures cause lactic acidosis?
Seizures are self-limiting
52
What causes lactic acidosis in leukemia survivors?
They have packed poorly perfused bone marrow cavities
53
How does hepatic/renal failure cause lactic acidosis?
They cause impaired metabolism and excretion
54
How does diabetes mellitus cause lactic acidosis?
DM can cause formation of ketones/lactate; use of metformin
55
How does malnutrition cause lactic acidosis?
Deficiencies of vitamins and thiamine
56
How does rhabdomyolysis cause lactic acidosis?
Sulfur-containing amino acids are released
57
What causes ketoacidosis?
Increased acetoacetic acid and B-OH butyric acid
58
How does salicylate toxicity cause respiratory alkalosis?
Stimulation of respiratory drive
59
How does salicylate toxicity cause metabolic acidosis?
Accumulation of organic acids
60
Symptoms of lactic acidosis (6)
- Kussmaul respirations
- Peripheral vasodilation causing flushing and tachycardia; as acidosis worsens, ventricular arrhythmias or reduced contractility may occur
- Hyperkalemia
- Lethargy/coma
- Nausea/vomiting
- Bone demineralization in chronic acidotic states
61
Treatment of lactic acidosis
- Treat the underlying cause
- Acute bicarbonate therapy (for severe and acute bicarb losses)
- Chronic bicarbonate therapy (for chronic metabolic acidosis)
- Tromethamine (THAM)
- Carbicarb/Dichloracetate
62
When should acute bicarbonate therapy be considered for use?
when pH < 7.10 - 7.15
63
What are good indications for acute bicarbonate therapy?
- Hyperkalemia
- pH < 7.10 with cardiac arrest after defibrillation
- Ventilation
- Other medications have been utilized
- Overdoses
64
What is the equation for dosing bicarb?
Dose (mEq) - [o.5 L/kg (IBW)] X (desired HCO3- - actual HCO3-)
Use 12mEq/L for the desired HCO3-
65
How should you administer bicarb after an amount is calculated?
Give 1/3 to 1/2 the calculated dose and monitor the ABG
66
What does ABG mean
Arterial blood gas
67
During cardiac arrest, how much sodium bicarb can be given
~1 mEq/kg
68
Bicarb can lower ___ blood levels
Potassium
69
Hazards of bicarbonate therapy
- Overalkanization
- Hypernatremia/hyperosmolality
- CSF acidosis
- Electrolyte shift
70
What can overalkanization caused by bicarb therapy result in?
Reduced cerebral flow and impaired oxygen release from Hgb to tissues
71
How is CSF acidosis caused by bicarb therapy?
Occurs from the CO2 that is generated, which readily diffuses into the CSF
72
When bicarbonate is administered, there is a decrease in _____ which decreases myocardial contractility
ionized calcium
73
When should chronic bicarbonate therapy be considered for use?
When the patient has chronic metabolic acidosis
74
What average dosing should be used for chronic bicarbonate therapy?
1-3 mEq/kg/day (may go up to 10+ mEq/kg/day)
75
How does tromethamine (THAM) treat metabolic acidosis?
- Combines with H+ from H2CO3 to form HCO3-
| - Acts as an osmotic diuretic to increase urine flow, urine pH, and excretion of fixed acids
76
Highly alkaline patients can experience ___ and ___
inflammation and extravasation
77
It is important to administer THAM ___ while monitoring ____
slowly; pH to avoid alkalosis
78
Adverse effects of THAM
- Hyperkalemia
- Hypoglycemia
- Hypocalcemia
- Impaired coagulation
79
What is carbicarb?
Mixture of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3)
80
How does carbicarb help treat metabolic acidosis?
Preferentially buffers hydrogen ions resulting in the formation of bicarb rather than CO2
81
How does dichloroacetate (DCA) help treat metabolic acidosis?
It facilitates lactate metabolism
82
Metabolic alkalosis is characterized by what 3 things?
- pH > 7.45
- Increased HCO3-
- Compensatory hypoventilation resulting in increased PaCO2
83
What causes a rise in plasma HCO3-?
- Loss of acid from GI tract or urine
- Administration of HCO3- or a bicarb precursor
- Contraction of alkalosis (loss of Cl- rich, HCO3- poor fluid)
84
Impairment of renal ___ excretion can result in the maintenance of metabolic alkalosis
HCO3-
85
How do volume and chloride depletion contribute to metabolic alkalosis?
- Decrease in arterial blood volume
- Decrease in ability of kidney to excrete HCO3-
- With volume depletion, capacity of the proximal tubule to reabsorb HCO3- increases
86
What is the most common cause of saline responsive alkalosis?
Diuretic therapy
87
In saline responsive alkalosis, urinary chloride is ____ mEq/L
< 10-20
88
What are causes of saline responsive alkalosis?
- Diuretic therapy
- Vomiting & NG suction
- Exogenous HCO3- administration or blood transfusions
- Maintenance of the alkalosis
89
What are some examples of diuretic therapy?
Furosemide, torsemide, HCTZ, bumetanide
90
Diuretic therapy enhances excretion of ___ and ___, resulting in extracellular volume contraction
Sodium chloride and water
91
Volume contraction stimulates ____ release
aldosterone
92
Aldosterone increases distal tubular ____ reabsorption adn induces ___ and ____ secretion
Na+, K+ and H+
93
H+ secretion is associated with ____ reabsorption
HCO3-
94
Normally Cl- is absorbed with ____
Na+
95
Without Cl- (hypochloremia), Na- is reabsorbed with ___
HCO3-
96
What is the second most common cause of alkalosis?
Vomiting and NG suction
97
How much fluid can be lost per day with vomiting?
1 L/day
98
What is used to preserve blood products and what does it do in the body?
Citrate --> Breaks down to HCO3-
99
What 3 things can result in maintenance of alkalosis?
- Reduced GFR
- Enhanced proximal tubular HCO3- reabsorption
- Effects of hypokalemia
100
What happens during reduced GFR that leads to alkalosis?
Na+ reabsorption is increased in distal and proximal tubules, leading to H+ secretion and HCO3- reabsorption in those respective areas
101
What causes enhanced proximal tubular HCO3- reabsorption that leads to alkalosis?
With hypochloremia, Na+ is reabsorbed with HCO3-
102
How does hypokalemia cause alkalosis?
- With less K+, H+ is secreted while Na+ is reabsorbed
| - H+ secretion is associated with HCO3- reabsorption and ammoniagenesis
103
In saline resistant alkalosis, urinary chloride is ____ mEq/L
>20
104
During saline resistant alkalosis, there is enhanced___ excretion and ___ reabsorption
H+; HCO3-
105
What is the key difference between saline responsive and saline resistant alkalosis?
In saline resistant alkalosis there is no chloride depletion or there is an inability to reabsorb chloride
106
What causes saline resistant alkalosis?
- Increased mineralcorticoid activity
- Hypokalemia
- Renal tubular chloride wasting
107
What are symptoms of saline resistant alkalosis?
- Muscle cramps; weakness; paresthesias
- Postural dizziness
- Cellular hypoxia; mental confusion, coma; seizures
- Direct myocardial suppression; CV collapse; arrhythmias
108
What are possible treatment options for saline resistant alkalosis
- Correct underlying cause
| - Rapid correction not necessary but treatment is still needed
