Dysnatremias Flashcards
1
Q
What is hypernatremia?
A
Sodium over 145
2
Q
What are the 2 main phases of hypernatremia?
A
Generation and maintenance
3
Q
What are 2 forms of generation phase of hypernatremia?
A
- Loss of later
- Gain of salt (sodium ingestion via salt tabls and infant formula, mineralocorticoid excess, and iatrogenic via IV fluids, dialysis, tube feeds, and TPN)
4
Q
What are 2 forms of the maintenance phase of hypernatremia?
A
- Failure to drink water
2. Inability to sense thirst
5
Q
Are hyper and hypo natremia issues with salt?
A
NO they are issues with water
6
Q
General view of hypernatremia?
A
Loss of water leading to dehydration
-If patient can take in H20 normally, it shoudl correct itself
7
Q
What is hypernatremia most often caused by?
A
A loss of water either renal or extra renal
8
Q
What are 2 renal causes for loss of water leading to hypernatremia?
A
- Diabetes insipidus
2. Osmotic diuresis
9
Q
What are the 2 types of diabetes insipidus?
A
- Central
2. Nephrogenic
10
Q
Describe central DI?
A
Inability of brain to release ADH
- Caused by brain injury (iatrogenic (surgery), trauma, tumors, ischemic insults, infections)
- Kidneys are normal
11
Q
Does central DI respond to ADH when supplied?
A
YES
12
Q
Describe nephrogenic DI?
A
Inability of kidney to respond to ADH
- The collecting tubules are impermeable to water (can be caused by chronic lithium use, congenital, or demeclocycline)
- Other causes of poor response to ADH include hypercalcemia, loop diuretics, hypokalemia, sickle cell
13
Q
What is the 1st step to diagnosing DI?
A
Water restriction test…this differentiates psychogenic polydipsia, CDI, and NDA
14
Q
In the water restriction test, what is seen if the patient has hyponatremia due to psychogenic polydipsia?
A
There is a progressive increase in the urine osmolarity
15
Q
What is seen in the water restriction test if the patient has NDI or CDI?
A
NOTHING…no change in urine osmolarity
16
Q
What will happen if you give ADH to someone with CDI?
A
THe urine osmolarity will increase
17
Q
What will happen if you give ADH to someone with NDI?
A
No change in urine osmolarity
18
Q
What will happen if you give ADH to someone with psychogenic polydipsia?
A
No change in urine osmolarity
19
Q
What is the treatment for psychogenic polydipsia?
A
STOP DRINKING
20
Q
What is the treatment for CDI?
A
DDAVP (desmopressin)
21
Q
What is the treatment for NDI?
A
Diuretics…thiazide with K-sparing will increase water resorption in ADH independent regions of the kidney
22
Q
What are 3 causes of osmotic diuresis?
A
- Hyperglycemia
- Post-obstructive (can’t void… like in BPH)
- Mannitol: Diuretic that makes you pee a lot… have to keep up with fluid intake
23
Q
Generally, what is happening in osmotic diuresis?
A
You are peeing out lots of water and become hypernatremia (you need to drink H20)…
24
Q
What are 3 sources of extra renal loss of water?
A
- Skin losses: Burns
- Pulmonary Losses: Advanced COPD, breating too fast/too often
- GI losses: Acute diarrhea, IBD
25
What are signs and symptoms of hypernatremia?
Confusion, lethargy, weakness, seizure, coma
26
What is the risk in treating hypernatremia?
The speed of correction
27
What is the speed of correction in chronic (over 48 hours) asymptomatic hypernatrmia?
Don't excees 0.5mEq/L/hr
28
What is the speed of correction in acute (less than 48 hours) symptomatic hypernatremia?
1-1.15 mEq/L/hr until symptoms improve, then slow the rate to 0.5mEw/L/hr
29
Why do we recheck Na levels frequently when correcting them?
Want to avoid an undesirable rate
30
What is the rate at which we should give fluids?
Deficit/time
31
How to we calculate time to correction?
Difference between current and normal sodium/ 0.5
32
How do we calculate water deficit?
Estimated TBW * Weight in Kg * (Current Na/140-1)
| Estimated TBW is 0.5 in males and 0.4 in females
33
What is hyponatermia?
Plama sodium under 135
34
What is typically the problem in hyponatremia?
WATER (ingested water is greater than excreted water)
35
What things can result in too much water with normal intake?
1. Renal failure (dialysis helps with this)
| 2. Increased ADH (lung tumors, heart failure, cirrhosis)
36
Can excessive intake of water overwhelm normal kidneys leading to hyponatremia?
YES
37
What are the marks of true hyponatremia?
Low plasma osmolarity and low plasma Na
38
What 2 states are considered to be pseudohyponatremia?
Normal plasma osmolarity and low plasma Na
| High plama osmolarity and low plasma Na
39
What conditions are associated with pseudohyponatremia with normal plasma osmolarity?
1. Hyperlipidemia
| 2. Hyperproteinemia
40
What conditions are associated with pseudohyponatremia with high plasma osmolairty?
1. Glucose (hyperglecemia dilutes down NA)
| 2. Mannitol
41
If ADH is present, is the urine osmolality high?
YES
42
If there is ADH present, what do you need to do?
Determine if it is appropriate or inappropriate
43
What are states where presence of ADH is appropriate with hyponatremia?
1. Hypervolemia (CHF, nephrosis, cirrhosis)
| 2. Hypovolemia (fluid losses)
44
What are states where prescence of ADH is inappropriate?
Euvolemia: This can indicate SIAHD, hypothyroid, adrenal insufficiency
45
Can you test urine osmality if the patient is on diuretics?
NO...you need to take these levels after 24 hours off of diuretics because diuretics can affect urine osmolality
46
What needs to be done to determine a true hyponatremia (low serum Na and osmolality)?
You have to confirm the low level by checking the plasma osmolality (don't use an estimated value)
47
Once a true hyponatremia is established, what do you do next?
Assess volume status: Hypovolemic, euvolemic, hypervolemic
48
What are signs of fluid overload (hypervolemic)?
Skin turgor, putting edema, JVD
49
If your patient is hypovolemic or euvolemic, what do you do next?
Urine sodium and osmolality
50
What is present if urine osmolality if high?
ADH
51
What is seen in psychogenic polydipsia?
Low urine sodium and low urine osmolality
52
What is seen in hypovolemic hyponatremia?
Low urine sodium and high urine osmolality (if not on diuretics) ...associated with ADH
53
What is seen in euvolemic hyponatremia?
High urine sodium and high osmolality (seen with SIADH, adrenal insufficiency, hypothyroidism)
54
What are signs and symptoms of hyponatremia?
Seizure, nausea, headache, lethargy, confusion, coma
55
What is predictive of symptoms in hyponatremia?
How quickly the level has changed (absolute level of hyponatremia isn't always predictive of symptoms)
56
What is acute hyponatremia?
Under 48 hours
57
What is chronic hyponatremia?
Over 48 hours (true timeline isn't usually known and is therefore chronic
58
What is the most feared treatment complication in hyponatremia?
Central pontine myelinolysis
59
When is central pontine myelinolysis seen?
With overly rapid correction of chronic compensated hyponatremia
60
What is seen in central pontine myelinolysis?
Devastating neurologic consequences that typically lead to death within a matter of weeks
1. Flaccid quadriplegia
2. Respiratory muscle paralysis
3. Coma
4. Pseudobulbar palsy
61
What are risk factors for central pontine myelinolysis?
1. Over correction
2. Improvement at a rate greater than 1-2mEq/hr
3. EtOH
4. Female
5. Liver disease
6. Malnutrition
62
What is happening in central pontine meylinolysis to cause symptoms?
Rapid movement of fluid out of brain cells causing the cells to shrink and their myelin sheaths to crack (demyelinate from that)
63
What can be done to see lesions in central pontine myelinolysis and when can you do this?
Lesions detectable on MRI and CT...may not be seen for up to 4 weeks
64
How should you approach treatment of hyponatremia?
WITH CAUTION - Repeat levels in a couple of hours to be safe
65
What's the approach for treatment of hypovolemic hyponatremia?
0.9% saline, not difficult to correct
66
What are symptoms due to in hypovolemic hyponatremia?
Volume depletion, not hyponatremia
67
What else is 0.9% saline given for besides hypovolemic hyponatremia?
Hypotension, vomiting, diarrhea
68
What is given for the acute treatment of euvolemic hyponatremia?
- 3% saline for acute symptoms, but discontinue once severe symptoms resolve and sodium is in the safe range (100-125)
- Water/fluid restriction (1000mL fluid a day)
- Recheck sodium frequently
69
What makes euvolemic hyponatremia worse in acute treatment?
0. 9% saline
| - You need to give fluid that is more concentrated than the urine osmolality
70
What is given for chronic treatment of euvolemic hyponatremia (possibly from SIADH)?
This one is difficult to treat and maintain
* Treat underlying disorder (like CA, which cna produce ADH like material)
- Limit fluids
- Demeclocycline (SE is hypernatremia because this dilutes urine even more)
- Salt (or urea) tablets
71
What is given for treatment of hypervolemic hyponatremia (perhaps from cirrhosis, nephrosis, or CHF)
1. Treat underlying disorder (Maybe with ACEi or BB)
2. Fluid restriction
3. Diuretics
4. Vasopressin receptor antagonists (aquaretic...which is electrolyte-free diuresis)
72
What can happen from too much TPN?
Patient can become protein overfed, which will increase water output resulting in volume depletion and dehydration leading to iatrogenic hypernatremia
73
If your patient is getting mannitol to control intracranial pressure, what can you see?
Pseudohypernatremia due to mannitol (ostmotic diuretic...peeing out all fluid)
74
If you have a patient with polyuria and polydipsia with insatiable thirst what might be the cause of hyponatremia?
Hyperglycemia (DIABETIC) which is causing a pseudohyponatremia (glucose is diluting out all the Na)
75
What's a general guideline for how quickly hyponatrmia should be corrected?
10mEq/L/day
76
If you correct hyponatremia too quickly, what can happen?
Osmotic demyelination syndrome
77
Who is at risk for osmotic demyelination syndrome?
1. Lower starting sodium (110 or lower)
2. Advanced liver disease
3. Alcoholism
4. Chronic hyponatremia: 48-72 hours or if previous Na unknown
5. Corrected from hyponatremia too quickly (more than 10-12mEw/L in a 24 hour period
78
What indicates that a patient will begin to correct from hyponatremia too quickly?
Polyuria (so measure their urine output hourly)
79
How often should serum Na be checked
Every 3-4 hours
80
What can you do if the Na begins to rise at an undesirable rate?
1. Hypotonic fluids can be ordered (D5 which will decrease Na back to safe rate of correction)
2. DDAVP can be given (vasopressin will drop urine flow
81
In psychogenic polydipsia, what is a common feature of the urine?
It has a low urine sodium and low urine osmolality
82
In psychogenic polydipsia what should you do regarding water and liquids
Restrict them! Even guard the toilet
83
If you have a patient who has stopped drinking and presents with normal BP and hypernatremia, what will you give?
IV D5W at 100mL/hr and recheck sodium every 4 hours
84
If you have a patient who has stopped drinking and presents hypotensive with hypernatrmia, what will you give?
IV 0.9% saline at 250ml/hr
| -This is given to normalize the BP, then any volume depletion (still hypernatrmic) can be treated with D5W
85
If you have a patient who is dehydrated and can drink lots of water, can they correct their own hypernatrmia?
YES
86
What will 0.225% saline cause?
RBC lysis... it's too hypotonic...don't use this fluid
87
How do you differentiate between dehydration and volume depletion?
- Dehydration requires a high sodium
| - Volume depletion can have a normal Na
88
What do you treat dehydration with?
WATER (because they have high sodium)
89
What do you treat volume depletion with?
SALT (like an isotonic fluid or something)
90
How do you calculate how many fluids to give?
Dosing factor * weight * (Serum Na/140-1)
| Dosing factor is 0.6 is male and 0.5 is female
91
If a patient has hypernatremia and is given desmopressin with no change in urine output (decrease), what might he have?
Nephrogenic DI because it isn't responding to desmopressin
92
What can cause NDI?
Chronic lithium use
93
What can be given for someone with hypernatremia due to NDI?
D5W
94
If patient has hypernatremia and it responds to desmopressin (via fall in urine output), what might she have?
Central diabetes insipidus
95
In someone with CDI, what will the urine osmolality be before and after treatment?
Before it will be DILUTE, after it will be CONCENTRATED
96
What types of sitations might result in CDI
Maybe a brain surgery or something affecting the BRAIN
97
If someone has lung cancer, what else are you thinking they might have?
SIADH
98
What clinical features are seen in someone with SIADH (possibly from a lung tumor)?
Hyponatremia (reataining water), low BUN and uric acid, super concetrated urine (high urine osmolality and sodium)
99
If the BUN is high, what does that indicate?
Volume depletion
100
If BUN is low, what does that indicate?
Mild volume overload
101
If someone with lung cancer is hyponatremic, but their urine sodium and urine osmolality are normal to low, what might be the reason?
They could be puking their guts out from chemo (NOT ALL LUNG CA PATIENTS HAVE SIADH)
102
What kind of urine osmolality number are you looking at in someone with SIADH?
Over 300 or at least more than serum osmolality
103
If you're giving someone in labor oxytoxin and them a crap ton of fluids and they become hyponatremic, what could be the cause?
Oxytocin causes you to secrete ADH, so then she can't excrete all that extra water you are giving her and she will become hyponatremic and SEIZE
104
Why would a little old thin lady on hydrochlorothiazide become hyponatremic?
Since she's peeing so much from the diuretic, she might think she needs to drink more to compensate, so she drinks a ton of water and becomes hyponatremic
105
So if your old lady on thiazide diuretics has hyponatrmia, what are you gonna do about it?
- Start her on 0.9% saline and check her in 4 hours
- If correcting too fast, can give 3% saline
- NO excess water drinking or fluids with this
106
When is a time you might see hypernatremia in a kid?
When their parents are messed up and give the salt tablets in Munchhausen by proxy
