Electrolytes Flashcards
what is the IBW for men?
IBW = 50kg + (2.3 x inches over 60’’)
what is the IBW for women?
IBW = 45.5kg + (2.3 x inches over 60”)
what is the equation for NBW?
NBW = IBW + 0.25 (wt-IBW)
when do you use NBW and what does it apply to when doing calculations?
–> use NBW if ABW > 130%s of IBW
–> this applies to fluid, electrolytes, and nutrition (FEN) parameters
what is the fluid distribution like in the body?
- intracellular –> 2/3 (40% of wt)
- extracellular –> 1/3 (20% of wt)
what are the two types of extracellular fluid, what they are, and what percent of extracellular are they?
- interstitial – 3/4 – surrounding cell
- intravascular – 1/4 – plasma
when balancing fluids what are the 3 key organs and how do we balance fluids?
- skin
- lungs
- kidneys
– fluid intake = fluid losses ( in=out)
what is the body water composition for women, men, and neonates?
W – 45-55%
M – 50-60%
N – 75-90%
what is the average fluid loss for sensible and what does that mean?
sensible – urination, poop, wounds
—– 1-1.5 L/day
what is the average fluid loss for insensible and what does that mean?
insensible – skin and lungs
——- 1 L/day
what is not counted toward the daily balance?
gastric, intestinal, pancreatic, and biliary secretions and almost completely reabsorbed
what are some additional fluid losses we don’t think about that may or may not be measurable?
- NG output
- vomit
– diarrhea
– large wounds
– burns
– drains
– bleeding
what is isotonic solutions range and meaning?
- same conc in as out
- between 275-290 mOsm/L
what is hypotonic range and meaning?
- less conc in than out
- < 275 mOsm/L
what is hypertonic range and meaning?
- more conc in than out
- > 290 mOsm/L
why do we care about the osmolarity?
it can result in hemolysis of RBCs, renal failure, and even death
how do you calculate osmolarity of IVs?
- total osmolarity = osmolarity of IV solution + osmolarity of added electrolytes
- in mOsm/ L
How do you calculate MIVF and what are the amount needed?
– use 30-40 mL/kg x weight in kg = MIVF/ day
– for hourly rate use MIVF/ day and divide by 24 h to get mL/hr
what is the tonicity of crystalloids?
isotonic, hypertonic, and hypotonic
what is the tonicity of colloids?
hpertonic
what do crystalloids solutions do?
- provide water and sodium
- maintain fluid between intravascular and extravascular space
when is normal saline used (0.9%)?
- for fluid replacement
when is 1/2 NS uses (0.45%)?
- for maintenance
when do you use LRs?
- for resuscitation (trauma, burns, when they need blood)
when do you use dextrose 5%?
- for free water replacement
- NOT BY ITSELF & NOT RESUSCITATIVE FLUID
what are some examples of balanced salt solutions (buffer- solutions)?
- LRs
- Normosol-R
- Plasma-lyte
How much sodium is in 0.9% and 0.45%?
0.9% – 154
0.45% – 77
when are colloids used?
- to inc. plasma oncotic pressure
- move fluid into plasma
what are colloids place in therapy?
for volume expansion
- people who need blood
what is albumin used for and its adverse effects?
- AEs
– azotemia
– hypervolemia - supportive/ symptomatic tx unless hypoproteinemia
when do you use 5% vs. 25% albumin
5%- when need volume
25%- when need protein
tell me about blood as a colloid?
- 1 unit RBC = 230-350mL
- low hemoglobin < equal to 7-8 g/dL
- 1 unit of blood increases Hb by 1 g/dL
what is the most common MIVF?
D5W + 1/2 NS + 20 mEq KCl/L
- similar to urine
what do we monitor for in fluid status?
- volume status –> dehydration
- OUP in mL/kg/hr
- weight, vitals, ins/outs
what are possible signs of dehydrations?
- tachycardia and hypotension
- BUN/SCr > 20
- decreased urine output < 0.5 mL.kg.hr
what is the normal sodium range?
- 135-145 mEq/L
what is hyponatremia and what classifies it?
- most common electrolyte disturbance
- Na < 135
how do we calculate serum osmolarity?
- Osm= (2 x Na) + (BUN/2.8) + (Glucose/18)
what is pseudohypontremia and when can we see this in patients?
- normal Osmserum
- can be seen with hypertriglyceridemia (TG > 1000) or hyperproteinemia
what is hypertonic hyponatremia and what population is it most seen with?
- high Osm >290
- in people with elevated BG
how do you calculate corrected serum sodium?
corrected Na = Naserum + (1.6 (BG-100)/100)
what is low osm for low sodium?
hypotonic hyponatremia
what makes a volume status of hypotonic hyponatremia HYPOVOLEMIC?
decrease in both TBW and Na+
what are the renal causes for HYPOvolemic “”?
urine >20
– diuretics
– salt losing nephropathy
- adrenal insufficiency
what are non-renal causes of HYPOvolemic “”?
- blood loss
- skin loss
- GI loss
what classifies hypotonic hyponatremia to “ISOvolemic”?
- increase in TBW and normal or slightly inc. Na+
what is a cause of ISOvolemic “”?
SIADH
what is SIADH and what is its main cause?
- syndrome of inappropriate AntiDiuretic Hormone release
- drugs are the main cause
what drugs specifically are the main cause?
- antipsychs
- carbamazepine
- SSRIs (prozac, zoloft)
how do you treat SIADH?
- remove underlying cause if possible
- first line: free H20 restriction
what makes it HYPERvolemic “”?
both TBW and Na+ increase
what are some clinical presentations of hypotonic hyponatremia for both hypo and hypervolemic?
- hypovolemic: dehydration
- hypervolemic: fluid overload
what are the goals in treatment of hypotonic hyponatremia?
- not to rise serum sodium > 0.5 mEq/L/hr or no more than NMT 8-12 mEq/L/day
what are the treatment options for hypovolemic hyponatremia (hypertonic and isotonic)?
- hypertonic NaCl 3% if symptomatic
- isotonic 0.9% if asymptomatic
what is the treatment for isovolemic hyponatremia?
- lasix and 3% NaCl if symptomatic
- 0.9% NaCl if asymptomatic and water restirction
how do you treat hypervolemic hyponatremia?
- lasix and judicious 3% if symptomatic
- lasix only if asymptomatic
what is acute hyponatremia?
- <48 hours
- very severe
–> canc ause AMS, seizures, cerebral edema - need prompt treatment
how do you treat acute symptomatic hyponatremia?
- increase serum Na+ by 1-2mEq/L/hr
- if too rapidly can cause central pontine myelinolysis
- max increase is 8-12 mEq/L in first 24 hours
what is the rule of 8s?
- replace half sodium deficit in 8 hours, then remaining deficit within 8-16hrs
how do you calculate TBW in M/F?
- M = 0.6 x wt (in kg)
- F = 0.5 x wt (in kg)
how do you calculate a sodium deficit?
TBW x Na goal - current Naserum)
what is hypernatremia and what must we access?
- associated with hypertonicity
- must assess volume status
what classifies hypernatremia?
Na+ > 145 mEq/L
What classifies hypovolemic hypernatremia and where at?
- loss of water and sodium
- renal, GI, lungs, skin
what classifies hypervolemic hypernatremia?
- gain H20 and Na+
- sodium overload and mineralocorticoid excess
what classifies isovolemic hypernatremia?
- loss of H20 and na+ is normal or slightly high
- diabetes insipidus
- skin loss
how do you calculate free H20 deficit for hypovolemic hypernatremia?
Free H20 deficit =TBW x [(Naserum/140)-1]
how do you replace free water deficit?
- provide free water
- match I/O
- don’t correct too quickly
- goal is 0.5 mEq/L/hr decrease in Naserum
what are the monitoring parameters for serum Na+ conc. and fluid status?
- check every 3-6hrs over the first 24 hours
- when sx resolve and Na+ < 145, then q 6-12hrs
- I/O q8-12hr
- overall fluid balance q24h
what is the treatment for ISOvolemic hypernatremia?
- desmopressin (DDAVP)
- vasopressin
tell me about hypervolemic hypernatremia and treatment?
- generally this is uncommon
– hypertonic saline resuscitation - tx: diuretic if needed
- match I/O
how do you calculate the estimated change in sodium?
- Change in Naserum= (Nafluid-Naserum)/(TBW + 1L)
- estimates change per one liter
what is the normal range for potassium?
3.5-5
what factors affect potassium?
- Na/K ATPase pump
- kidneys
- arterial pH/ acid-base status
what are the causes of hypokalemia?
- magnesium depletion
–> co-factor for Na/K ATPase
what is the treatment for potassium of levels 3.5-4?
none
- if in ICU goal is 4 so may need to treat
what is the treatment for potassium at 3-3.4?
- debatable
- po potassium with cardiac outputs
what is the treatment for potassium <3?
- po route preferred if asymptomatic
- iv for symptomatic or patients who can’t take PO
what do you do with any treatment of potassium?
attempt to correct magnesium deficit
what are some warnings/precautions with IV K+?
- arrhythmia or cardiac arrest if given too quickly
how do you administer IV K+?
- infusion rate WITHOUT cardiac monitor
—–> 10 mEq/hr - infusion WITH cardiac monitoring
—–> 20 mEq/hr
what are the different stages of hyperkalemia?
- mild
– 5.5-6 - moderate
– 6.1-6.9 - severe
- > or equal to 7
what is a clinical presentation of hyperkalemia?
cardiac arrhythmias
– peaked T waves
what are goals of therapy for hyperkalemia?
- antagonize AEs
- everse symptoms
- return K+ to normal
- correct underlying cause
how do you treat severe hyperkalemia (>7)?
- antagonize membrane actions
- decrease extracellular K+ concentrations
- remove K+ from the body
how do we antagonize the membrane actions?
- calcium
how do we decrease extracellular K+ conc.?
- albuterol
- bicarb
- insulin and glucose
how do we remove K+ from the body?
- lokelma
- diuretics
- renal unit for dialysis of patient
what is the normal range for magnesium?
1.5-2.5
what are some fun facts about magnesium?
- it is a co-factor for many enzymes in the body such as ATP and Alkaline phosphatase
- it is related to Ca2+ and K+ metabolism
what is a major drug cause of hypomagnesemia?
- diuretics (thiazide or loop)
what is the treatment for hypomagnesemia for asymptomatic patients?
- PO with Mg2+ > 1 mg/dL
—- MOM
—- Mag-Ox
what is the treatment for hypomagnesemia for symptomatic patients?
- goal in ICU is > equal to 2mg/dL
IV
– mg 1-2 mg/dL : 0.5 mEg/kg
– mg < 1: 1mEq/kg
—- 8mEq/1g= infuse 1 gm per hour
what is the normal range for calcium?
8.5-10.5
what are the etiologies for hypocalcemia?
- mag deficiency
- large volumes of blood products
- hypoalbuminemia (correct Ca2+)
how do you correct Calcium?
- measured Ca2+ +[(4-measured albumin) x 0.8]
what is the acute treatment for hypocalcemia?
- 100-300 ELEMENTAL Ca2+
—-> 1 g Ca CHLORIDE = 3 g Ca GLUCONATE = 270 ELEMENTAL Ca
what is the rate for acute treatment for hypocalcemia and what else must you correct?
- admin at a rate of 1gm/hr
- correct hypomagnesemia
what is the chronic treatment for hypocalcemia?
- PO calcium
- 1-3g of ELEMENTAL/ day
- Vit D supplements
– calcitriol
what is the normal range for phosphorus?
2.5-4.5
what is mild to moderate hypophosphatemia?
conc of 1-2
what is severe hypophosphatemia?
< 1
- icu goal is > or equal to 3
what are the etiologies of hypophosphatemia?
- dec. intake
- impaired absorption
- intracellular shifts
how do you treat mild to hypophosphatemia?
ORAL
- Phos-NaK
- Fleets Phospho-Soda
how do you treat severe hypophosphatemia?
IV
- KPhos when K+ < 4
- NaPhos when K+ > or equal to 4
what is the phos replacement numbers for NaPhos ratio?
1 mMol = 1.33 Na & 1.33 Phos
what is the phos replacement numbers for KPhos ratio?
1 mMol = 1.47 K & 1.47 Phos
how do you administer IV phos replacements?
no faster than 7 mMol/hr