Fluids + Electrolytes Flashcards
Water makes up what % of total body weight?
50-60 %
50-60% of total body weight is composed of what?
water
Relationship between TB weight and TBwater is a reflection?
body fat
**lean tissues like muscle and solid organs –> have higher water content than fat/bone
Lean tissues like muscle and solid organs have higher water content than what?
Fat/Bone
Why do young lean males have a higher proportion of TB water than an elderly or obese pt?
lean tissues like muscle and solid organs have more water content that fat/bone
TBWater and TBWeight in males vs females:
males–> TBwater makes up 60% of weight
females—> TBwater makes up 50% of weight
women have more adipose, less muscle tissue
The highest % of TBWater per weight is found in which pts?
newborns
In newborns what % of TBweight is TBwater?
80%
decreased to 65% by year 1 and then remains stable
In the body, water can be found in 3 compartments, what are they?
intracellular
intravascular
interstitial
2/3 of water in the body found where?
intracellular
Intravascular volume makes up what % of TB weight?
5-7%
Intracellular water makes up what % of an individual’s total body weight?
40%, mostly in skeletal muscle
What are the main intracellular cations??
K
Mg
What are the main intracellular anions?
phosphates
proteins
Extracellularly what is the predominant cation?
Na
Extracellularly what are the anions?
Cl
HCO3
The concentration gradient between intra-cellular and extra-cellular compartments is maintained by what?
Na-K ATPase
What determines osmolality?
Na
Glucose
BUN
2N + Glu/18 + BUN/2.8
What is the osmolality of intracellular and extracellular fluids?
290-310 mOsm
What are the daily water intakes and daily water losses?
Intake; 2 L/day, 75% from PO, 25% from solid foods
Losses: 800- 1200 cc in urine, 250 cc in stool, 600 cc insensible
To clear products of metabolism the kidney must excrete how much water daily?
500-800 cc of urine/daily
What is a simple way to calculate fluid rate in pts weighing more than 40kg?
40 + weight in kg
73 kg male maintenance rate is 73 + 40–> 113 cc/hr
Maintenance fluid formula?
4 cc/kg for first 10 kg
2 cc/kg for next 10 kg
1 cc/kg for every kg over 20
(ex; 45 kg pt–> 4 x10, 2x 10, 1 x25 = 85cc/hr)
(ex; 73 kg pt–> 4x 10, 2 x 10, 1x 53 = 113 cc/hr)
Daily Na and K needs for a 70 kg male?
Na 2-4 g
K 100 mEq
What’s oliguria defined as?
less than 400 cc of urine in 24 hrs
How much urine do we need to make daily to excrete toxins?
0.24 cc/kg/hr
normally we give 0.5 cc/kg/hr to over compensate
Normal K level range?
Hypokalemia?
Hyperkalemia?
3.5–>5
Hypo–> less than 3.5
Hyper–> greater than 5
What are sensible fluid losses?
fluid losses from diarrhea, NG tube, urine output
WHat are insensible fluid losses?
fluid losses from skin, respiratory tract, open abdomen
Adult K requirements?
0.5–0.8 mEq/kg/day
What are normal insensible fluid losses for an adult daily?
50-500 cc/day
Systemic sxs of hypokalemia?
Neuro; fatigue, paresthesia, paralysis, can exacerbate increased ammonia production–> hepatic encephalopathy
MSK: rhabdomyolysis, diminished deep tendon reflexes
Renal; polyuria and polydipsia secondary to decreased ability to concentrate urine
GI: anorexia, N/V, due to paralytic ileus
What are some signs of hypokalemia?
constipation muscle fatigue parasthesia paralysis diminished deep tendon reflexes parasthesias
What conditions can cause hyperkalemia?
rhabdo
acidosis
muscle relaxants for anesthesia
hypoaldosteronism
hyperpyrexia
How does an acidosis cause hyperkalemia?
H ions are shifted into the intracellular space
K is shifted into the extracellular space
How does alkalosis cause hypokalemia?
H ions are shifted to the extracellular space
K is shifted into the intracellular space
EKG signs of hypokalemia?
low voltage, flattended, inverted T waves
prominent U waves
depressed ST segment
wide QRS
prolonged PR interval
Low voltage, flattended, inverted T waves, prominent U waves seen with hyper or hypokalemia?
hypokalemia
What EKG changes do we see with hyperkalemia?
peaked T waves (usually at K >6(
flattened P waves
can see complete heart block and atrial systole
When do we see sine wave appearance on EKG of hyperkalemia?
at K >8
wide QRS complexes merge with T waves
***this can be followed by v-fib and cardiac arrest
What do we do if hypokalemia is caused by low magnesium and low Ca?
replace Mg and Ca first
When treating a pt with hyperkalemia, what are some rapidly acting methods to correct?
IV calcium
IV insulin/glucose
**do not remove K from the body, just shift it in and out of cells
What are some methods of removing K from the body in cases of hyperkalemia?
loop diuretics;for use in pts without renal impairment
kayexalate
dialysis**very effective
2nd most prevalent intracellular cation?
Mg
What does Mg do?
cofactor in ATP-powered rxns
modulates Ca-influx
has a role w/muscles including myocyte contraction
Normal ranges of Mg?
1.5–2.5
Most abundant intra-cellular anion?
P
Role of phosphate?
organic form is important in ATP rxns
inorganic form (85%) is in bone, contributing to strength and structure
Normal serum P levels?
2.5–4.5
What cause hypomagnesemia?
renal, GI, skin losses
hungry bone syndrome
GI, renal, and skin causes of hypomagnesemia?
GI: chronic diarrhea, high output fistula
Renal: diuresis
skin: burns, TEN
How does etoh cause hypomagnesemia?
diuretic effect
magnesium deficiency
Causes of hypermagnesemia?
theophylline toxicity
magnesium containing antacids
magnesium infusion in obstetric pts w/preeclampsia
Causes of low phosphate?
hyperparathyroidism causes increased renal excretion of P
after major liver resection–> regenerating hepatocytes use phosphate rapidly
Causes of high phosphate?
pts w/renal insufficiency
pts w/tumor lysis syndrome, rhabdo, hemolysis
When do we start seeing sxs of hypomagnesemia in pts?
when levels fall below 1.2
Sxs of hypomagnesemia?
neuromuscular and CNS irritability
Seere hypomagnesemia in post-surgical pts can lead to what?
ventricular arrhythmia like Torsades
Sxs of hypermagnesemia?
usually with Mg >6
loss of deep tendon reflexes –> can progress to paralysis, apnea, heart failure, coma
Sxs of low phosphate?
muscle weakness
pts can become vent dependent or difficult to wean from vent after major liver resection
Sxs of high phosphate?
typically asymptomatic
How do we treat Torsades?
1 to 2 g magnesium bolus during 5 minutes
TX for hypermagnesemia?
Ca to stabilize heart
NS for fluid expansion
loop diuretics to excrete Mg out
Normal Ca ranges?
8.5–10.2
Most common Ca-binding protein?
albumin
Corrected Ca formula?
(0.8 x (Normal alb - Pt’s alb)] + serum Ca
How does blood transfusion cause hypocalcemia?
citrate in blood binds Calcium
Causes of low Ca?
massive transfusion
hypothyroidism after thyroid/parathyroid surgery
Vit D deficiency
gastric bypass
acute pancreatitis
osteoblastic mets
Causes of hypercalcemia?
malignancy sarcoidosis 1, 3 hyperparathyroidism loops, thiazides FHH
What sxs do we normally see with hypocalcemia?
perioral numbness
tingling of extremities
muscle cramps
Trousseau sign seen in hypocalcemia?
carpopedial spasm when inflating BP cuff
Chvostek sign of hypocalcemia?
contraction of ipsilateral facial muscles by tapping facial nerve anterior to ear
Sxs of hypercalcemia?
fatigue
depression
constipation
Acute hypercalcemia shows what EKG changes?
short QT interval
Hypocalcemia shows what EKG changes?
prolongation QT interval
Classifying hyponatremia as mild;moderate;severe;
mild; 130-138
moderate; 120-130
severe; <120
Sxs of severe hyponatremia?
headaches
lethargy
induce comas/seizures
cells swell due to inability to maintain homeostatic osmolality
What does hypernatremia cause?
cells shrink
cause confusion, coma, intracranial hemorrhage
For central diabetes insipidus what drug can we give?
DDVAVP
Corrected Na formula?
[Na] + 0.016 x (glucose -100)
Formula for serum osmolality?
2 x [Na] + BUN/2.8 + Glucose/18
4:2:1 rule of fluid replacement;
4cc/kg/hr for first 10 kg
2 cc/kg/hr for next 10 kg
1 cc/kg/hr for every kg over 20 kg
Ex: 73 kg male; 4x 10 + 2 x10 + 1 x 53 = 113
Why do we want to correct hyponatremia gradually?
avoids central pontine myelinosis
seen 1 -6 days after
sxs; pseudo-bulbar palsy, quadriparesis, movement disorders, decreased consciousness
Rapid correction of severe hypernatremia causes?
irrerversible neurological deficits due to cerebral edema
