S3C21 - Fluids and Electrolytes Flashcards
1
Q
Total Body Water
A
- total body water = 60% of weight
- of which 67% is ICF and 33% is ECF
- of the 33% ECF, 25% of it is in the IVF which means from the 60% TBW, 5% is IVF
2
Q
Osmolality
A
- calculated and measured osmolality should be within 10 of each other
- ddx osmolar gap:
- decreased serum water content in setting of hyperlipidemia or hyperproteinemia
- other LMW substances in the serum:
- ethanol
- methanol
- isopropyl alcohol
- ehtylene glycol
- acteone
- ethyl ether
- paraldehyde
- lactate
- mannitol
3
Q
Hyponatremia
A
defn: <135mEq/L
- caused by either water gain or Na loss or alteration in the distribution of body water
- <120 pt is likely to get symptoms: n/v, anorexia, muscle cramps, confusion, lethargy, seizures, coma
- seizures likely to occur is Na <113mEq/L
- symptoms are caused by the osmotic gradient the develops across the BBB and from water being drawn into the brain
- in acute severe hyponatremia the mortality rate is 50%
- chronic hyponatremia symptoms: ataxia, focal weakness, hemiparesis
**be aware of correcting too rapidly and causing central pontine myelinolysis
4
Q
Urine Na in hyponatremia
A
- if renal system intact and working well then dilute urine should be made
- if urine [Na]<10mEq/L this indicates renal handling is intact
- if urine [Na] >20mEq/L this indicates intrinsic renal tubular damage or natriuretic response to hypervolemia
5
Q
Hypertonic Hyponatremia: causes
A
Osmolality >295
- usually occurs from shift of water from ICF into ECF
- DDX:
- -hyperglycemia
- -mannitol
- -glycerol therapy
Often there is a volume deficit and fluids are necessary
6
Q
Isotonic Hyponatremia: DDx
A
Osmolality 275-295
- also termed pseudohyponatremia because due to the high levels of plasma proteins/lipids this makes the lab report a hyponatremia where in fact the Na+ is normal
- do not need to treat the hyponatremia
DDX:
- hyperlipidemia
- hyperproteinemia (eg. multiple myeloma, waldenstrom macroglobulinemia)
p.119
7
Q
Hypotonic Hyonatremia: Ddx
A
Omsolality <275
Hypovolemic:
- renal: diuretic use, salt-wasting nephropathy (RTA, CKD, interstitial nephritis), osmotic diuresis (glucose, urea, hyperproteinemia), mineralcorticoid deficiency (aldosterone)
- extra-renal: volume replacement with hypotonic fluids, GI loss (vomiting, diarrhea, fistula, suction), third-space loss (burn, pancreatitis, peritonitis), sweating - CF
Hypervolemic:
- Urinary Na >20mEq/L = renal failure
- inability to excrete free water
- Urinary Na <20mEq/L
- CHF (low-flow to kidneys stimulates ADH)
- Nephrotic syndrome
- cirrhosis - causes decreased protein production
- Tx: usually salt and water restriction, sometimes diuretics or dialysis
Euvolemic: tx - fluid restriction
- urine Na usually >20mEq/L
- SIADH
- Hypothyroid
- pain, stress, nausea, psychosis (stimulates ADH)
- Drugs: ADH, nicotine, sulfonylureas, morphine, barbiturates, NSAIDs, tylenol, carbamazepine, penothiazines, TCA, colchicine, clofibrate, cyclophosphamide, isoproterenol, tolbutamide, vincristine, MAOI
- water intoxication (psychogenic or lesion in thirst center)
- glucocorticoid deficiency (glucocorticoids are required to suppress ADH)
- PPV - ventilation
- porphyria
*
8
Q
Diagnosis Of SIADH
A
6 criteria:
- hypotonic hyponatermia (low serum osmolality)
- innapropriately elevated urinary osmolality (>200mOsm/kg)
- elevated urinary Na (>20mEg/L)
- clinical euvolemia
- normal adrenal, renal, cardiac, hepatic, thyroid fxn
- correctable with water restriction
9
Q
Causes of SIADH
A
CNS: tumor, trauma, infxn, CVA, SAH, GBS, DTs, MS
Pulmonary Dz: tumor, PNA, COPD, abscess, TB, CF
Carcinoma: lung, pacreas, thymoma, ovarian, lymphoma
10
Q
Emergency treatment of hyponatremia
A
- usually do not have to address Na >120 in the ED
- Na <115 or symptomatic need treatment initiated immediately:
- get urine electrolytes
- if hypovolemic, calculate the Na deficit and replace with NS:
- total body [Na] deficit =
(desired plasma[Na] - actual plasma [Na]) xTBW - if severe (<120mEq/L), develops rapidly, or pt seizes/coma, 3% saline should be administered at 25-100mL/h
- rise in Na should be <0.5-1mEq/L per hour
- if pt seizing then Na can be raised by 1-2mEq/L per hour
- if chronic severe, only increase by max 0.5mEq/L/h (NMT 12mEq/L/d)
** symptoms may be irreversible!
11
Q
Hypernatremia
A
Defn: Na > 150mEq/L
- most are related to severe volume loss
- Symptoms: irritability, increased muscle tone, seizures, coma, death, tremulous, ataxia, hyperreflexic, spastic
- if osmolality >350mOsm/kg mortality >50%
- if brain shrinkage occurs rapidly this can tear blood vessels and cause bleeds
DDx:
- Inadequate water intake (impaired thirst, unable to obtain water)
- Excessive sodium
- ioatrogenic administration (hypertonic saline)
- accidental/deliverate ingestion (salt water ingestion/drowning)
- mineralcorticoid/glucocorticoid excess
- primary aldosteronism, cushings
- peritoneal dialysis
- GI loss - vomiting, diearrhea, intestinal fistula
- renal loss
- central diabetes insipidus
- impaired renal fxn
- osmotic diuresis (hypercalcemia, decreased protein intake, sickel cell, multiple myeloma, amyloidosis, sarcoidosis, sjogren, nephrogenic DI)
- drugs/meds (EtoH, lithium, phenytoin, sulfonylureas, amphotericin, colchicine)
- skin loss -burns, sweating
-essential hypernatremia
12
Q
Diabetes Insipidus
A
- failure of central of peripheral ADH response
- low urine osmolality (200-300) - excessive loss of hypotonic urine
- central - failure to excrete ADH
- distinguish b/w central and nephrogenic by taking the serum and urine osmolaritiy under water deprivation and what the response is to 5 units of vasopressin
- lack of response to fluid loss is diagnositc
- pts with central DI respond well to vasopressin (urine osmolarity >800mOsm/L), whereas nephrogenic DI does not respond
Causes:
- Central: neoplasm, pituitary surgery, trauma, granulomas
- Nephrogenic: familial, hypercalcemia, hypokalemia, renal dz, drugs, malnutrition, hematologic d/o
13
Q
Hypernatremia Treatment
A
- volume repletion with NS or RL
- interestingly, in my hypernatremic states there is an overall body deficit of Na+
- once perfusion has been established, switch to 0.45% saline with goal of u/o 0.5cc/kg/h
- do not reduce Na by >10-15mEq/L/day
- each liter of water deficit results in serum[Na] rise of 3-5mEq/L
- if acute hypernatremia then can rapidly correct b/c idiogenic osmoles (taurine) have not had a chance to be present in the brain yet so less risk of cerebral edema
14
Q
Hypokalemia
A
- normal value = 3.5-5mEq/L
- defn: <3.5mEq/L
- clinical manifestations occur at 2.5mEq/L
- tx:
- stable: can give 20mEq of K+ q30-60mins until desired dose achieved
- severe - give IV 10mEq increments over 30-60 mins
- NMT 40mEq to each litre of fluid and NMT 40mEq/h
- cardiac monitoring if infusion >20mEq/h
- 20mEq should raise serum K by 0.25mEq/L
15
Q
Symptoms of Hypokalemia
A
- Cardio: HTN, orthostatic hypotension, worsening of dig tox, dysrhythmia,
- t-wave flattening, u waves, ST depression
- neuro: malaise, weak, fatigue, hyporeflexive, cramps, paresthesias, paralysis, rhabdo
- GI - ileus
- renal: nephrogenic DI, incrased ammonia
- endocrine - glucose intolerance
19
Q
Hyperkalemia Treatment
A
- do ECG, if no changes on ECG then repeat test to make sure
- 5-6 : treat underlying cause
Emergency treatment:
- cardiac monitoring
- check for other lytes (Mg)
- 3 phases of treament:
- membrane stabilization
- intracellular shift of K
- remove/ excrete K from body
- NB - if calcium needs to be administered b/c of severity of hypokalemia, be wary of pts on digitalis b/c hypercalcemia will potentiate the toxic cardiac effects of digitalis (avoid giving Calcium to pts on dig)
Treatment:
- Calcium Gluconate 10% 10-20ml IV
or Calcium chloride 10% 5-10ml IV
**calcium chloride is 3x potent than calcium gluconate - NaHCO3 (Bicarb) 50-100mEq IV
- Insulin 5-10 units with 1-2 amps of D50W
- Ventolin 2.5mg neb
- Lasix 40mg IV
- hemodialysis
- 10% calcium chloride = 27.2 mg/ml
- 10% calcium gluconate = 9mg elemental calcium/mL
