Fluids, Electrolytes, Acids/Bases - Step Up Flashcards
total body water
60% of weight (50% in women)
- decreases with age and obesity
ICF is _ % of body weight; ECF is _ % of body weight, _% is interstitial fluid and _% is plasma
40
20
15
5
fluid loss due to insensible losses increases with .. (4)
fever, sweating, hyperventilation, tracheostomies (unhumidified air)
normal urine output in infants
> 1.0 ml/kg/hr
normal urine output in adults
> 0.5-1.0 ml/kg/hr
each degree over 37 C, body’s water loss increases by..
100 ml/day
what patients tend to third-space fluid?
any condition with hypoalbuminemia
- liver failure
- nephrotic syndrome
best fluid when pt is dehydrated or has lost blood
normal saline (0.9% NaCl)
what is the standard maintenance fluid?
D5 1/2 NS with 20 mEq KCl/L
5% dextrose and 1/2 normal Saline
which IVF should be avoided in heart failure and renal failure pts due to risk of volume overload?
normal saline
which IVF is used to dilute powdered medications?
D5W
MC trauma resuscitation fluid
Ringer’s Lactated solution
- excellent for replacement of IV fluids
- isotonic solution
in which situation should Ringer’s Lactate be avoided?
hyperkalemia
when should you consider placing a Swan-Ganz catheter in hypovolemic pt?
pt is critically ill
pt w/ cardiac or renal failure
what do elevated serum Na, low urine Na and BUN/Cr > 20:1 suggest?
hypoperfusion to the kidneys (sign of hypovolemia)
how does hematocrit change with hypovolemia?
3% increase for every liter deficit
how does CBC and proteins in serum change with hypovolemia?
increase with an ECF deficit
decrease with an ECF excess
how do you correct volume deficit in hypovolemia?
give bolus of either Lactated Ringers or Normal Saline
do not give bolus fluids with what? (2)
dextrose - hyperglycemia
potassium - hyperkalemia
how do you calculate maintenance fluids?
4-2-1 rule
4 ml for first 10 kg, 2 ml for next 10 kg, 1 ml/kg for every kg over 20
(always give 60 ml for first 20 kg)
signs of volume overload (6)
jugular venous distention elevated CVP or PCWP pulmonary rales peripheral edema weight gain low hematocrit or albumin conc
Tx. of hypervolemia
fluid restriction
diuretics
changes in Na+ conc. are a reflection of…
water balance
changes in Na+ content are a reflection of…
Na+ balance
main osmotically active cation of ECF
sodium
increase in Na+ intake results in…
increased ECF volume, increase in GFR and sodium excretion
normal plasma hypertonicity
295 mOsm/kg
formula for serum osmolarity
(2 Na) + BUN/2.8 + glucose/18
- if BUN and glucose normal, = (2Na) + 10
definition of hyponatremia
plasma Na+ conc < 135 mmol/L
when do symptoms of hyponatremia occur?
usually around Na+ conc of 120 mmol/L (except in cases of ICP where symptoms are made worse and earlier with low Na)
what happens to the deep tendon reflexes in hyponatremia?
hyperactive deep tendon reflexes
also get muscle twitching and weakness
how do you calculate free water deficit?
TBW (1 - actual Na+/desired Na+)
normal serum calcium
8.5-10.5 mg/dl
what does calcium balance depend on?
hormonally controlled
albumin level
pH
how does albumin affect Ca2+ levels?
most Ca2+ ions are bound to albumin; so if albumin is low, TOTAL Ca2+ is low, but ionized fraction is normal –> pt. does not show sx
how can you estimate ionized calcium?
total calcium - (serum albumin x 0.8)
how do you assess if person is truly hypocalcemic?
correct Ca2+ = measured total Ca2+ + 0.8 (4-albumin)
what effect does pH have on calcium?
increase pH (alkalosis) increases Ca2+ binding to albumin, total Ca2+ is normal but ionized Ca2+ decreases –> pt will manifest w/ signs of hypocalcemia
effect of PTH on calcium and phosphate
increases Ca2+ and decreases PO4-
effect of calcitonin on calcium and phosphate
decreases Ca2+ and decreases PO4-
effect of vit. D on calcium and phosphate
increases Ca2+ and increases PO4-
MCC of hypocalcemia
hypoparathyroidism - usually due to surgery
what could be the cause of LOW Ca2+ levels, but high PTH levels?
pseudohypoparathyroidism - end organ resistance to PTH
vitamin D deficiency
what electrolyte abnormalities cause hyperactive deep tendon reflexes?
hyponatremia
hypocalcemia
what are signs of tetany?
hyperactive deep tendon reflexes
Chvostek’s sign
Troussaeu’s sign
what are signs of increase neuromuscular irritability in hypocalcemia?
numbness/tingling - circumoral, fingers, toes
Tetany
Grand Mal seizures
cardiovascular manifestations of hypocalcemia
arrhythmias
prolonged QT syndrome
in the setting of hypocalcemia, when is Phosphate high?
renal insufficiency
hypoparathyroidism
Tx. of symptomatic hypocalcemia
IV calcium gluconate
how do you correct hypocalcemia due to PTH deficiency?
vitamin D and high oral Ca2+ intake
thiazide diuretics - lower urinary calcium
milk alkali syndrome
hypercalcemia, alkalosis and renal impairment due to excessive intake of calcium and absorbable antacids (calcium carbonate, milk)
drugs that cause hypercalcemia
thiazide diuretics
lithium
ECG findings in hypercalcemia
shortened QT interval
symptoms of hypercalcemia
nephrolithiasis/nephrocalcinosis bone aches/pains muscle pain and weakness pancreatitis, PUD, gout constipation psychiatric symptoms HTN weight loss
what additional lab finding is seen in primary hyperparathyroidism?
elevated urinary cAMP
first steps in management of anyone w/ hypercalcemia?
- IV fluids - normal saline
2. furosemide
what tx. inhibits bone resorption in pts with osteoclastic disease?
bisphosphonates (pamidronate)
calcitonin
when can you use glucocorticoids in tx. of hypercalcemia?
vitamin-D related mechanisms
multiple myeloma
normal K+ levels
3.5-5.0 mmol/L
effect of pH on serum k+
alkalosis = hypokalemia acidosis = hyperkalemia
if pt has HTN and hypokalemia…
excessive aldosterone activity is likely
if pt is normotensive and hypokalemic..
either GI or renal loss of K+ is likely
Bartter’s syndrome
chronic volume depletion secondary to AR-defect in salt reabsorption in TAL leading to hyperplasia of JG apparatus and increase renin levels and aldosterone levels; cause of hypokalemia
GI losses leading to hypokalemia (5)
vomiting, NG suction - alkalosis diarrhea laxatives/enemas intestinal fistulae decreased K+ absorption
renal losses leading to hypokalemia
diuretics renal tubular or parenchymal disease hyperaldosteronism licorice ingestion excessive steroids Mg2+ deficiency Bartter's syndrome
other causes of Hypokalemia
Insulin insufficiency dietary intake antibiotics - bactrim, amphotericin B profuse sweating B2-agonists
increased entry of K+ into cells
alkalosis
B2 agonists
Insulin
vit. B12 replacement
ECG changes in hypokalemia
T wave flattens out or inverts if severe
U wave appears
arrhythmias - prolongs normal cardiac conduction
effect of K+ levels on deep tendon reflexes
both hypo and hyperkalemia cause DECREASED deep tendon reflexes
CF of hypokalemia
muscle weakness/fatigue/paralysis/cramps decreased deep tendon reflexes paralytic ileus polyuria/polydipsia NV exacerbates digitalis toxicity
what two electrolytes are difficult to correct in case of hypomagnesemia?
Calcium
Potassium
preferred method of K+ replacement
oral K+ - safest
- 10 mEq of KCl increases K+ levels by 0.1 mEq/L
what kind of fluid should you avoid in hypokalemia?
dextrose containing fluids - increase insulin and cause further K+ shifts into cell
when can you give IV KCl
hypokalemia severe (<2.5) pt has arrhythmias
infusion rate of IV KCl
max 10mEq/hr in peripheral IV line; max 20 in central line
- add 1% lidocaine to decrease burning pain
in setting of hypokalemia, what does a urine K+ < 20 imply?
extra-renal loss
- renal loss has Urinary K+ > 20
causes of increased total body K+
renal failure/ type IV RTA Addison's dz drugs iatrogenic overdose blood transfusion
drugs that cause hyperkalemia
spironolactone NSAIDs ACEi heparin cyclosporine digitalis succinylcholine Bactrim B-blockers
what can cause a shift of K+ OUT of cells
insulin deficiency B-blockers acidosis tissue/cell breakdown - burns, rhabdo GI bleeding
effect of acidosis on K+ levels
- every 0.1 decrease in pH, K+ increases by 0.7 points
what can cause pseudohyperkalemia (spurious elevation)
tight/prolonged tourniquet application
delay in processing - RBC hemolysis
leukocytosis
thrombocytosis
effect of hyperkalemia on ammonia
inhibits ammonia synthesis and reabsorption = metabolic acidosis which shifts K+ out of cells and exacerbates it further
ECG changes in hyperkalemia
peaked T waves –> widened QRS –> prolonged PR –> loss of P waves –> sine wave pattern –> V.fib
CF of hyperkalemia
arrhythmias muscle weakness and flaccid paralysis decreased deep tendon reflexes respiratory failure NVD, intestinal colic
Tx of severe hyperkalemia with ECG changes, muscle paralysis or level > 6.5
IV calcium gluconate
methods to immediately/quickly lower K+ levels
- insulin + glucose (30-60 min)
2. sodium bicarbonate - emergency measure in severe hyperkalemia
methods of removing K+ from the body
Kayexalate - sodium polystyrene sulfonate (cation exchange resin)
Hemodialysis
Furosemide
who is hemodialysis reserved for in hyperkalemia tx.?
intractable hyperkalemia
pts with renal failure
normal Mg2+ levels
1.8-2.5 mg/dL
MCC of hypomagnesemia
steatorrheic states
causes of hypomagnesemia
GI - steatorrhea, malabsorption, prolonged fasting, TPN, fistulas
alcoholics
renal causes - SIADH, diuretics, Bartter’s, drugs, renal transplant
drugs causing hypomagnesemia
gentamicin
amphotericin B
cisplatin
neuromuscular and CNS sx of hypomagnesemia
muscle twitching/weakness, tremor
hyperreflexia
mental status changes
seizures
ECG changes in hypomagnesemia
prolonged QT
T wave flattening
torsades de pointes
Tx. of hypomagnesemia
mild - oral Mg (Mg2+ oxide)
severe - IV Mg (Mg sulfate)
first sign of hypermagnesemia
progressive loss of deep tendon reflexes
CF of hypermagnesemia
nausea, weakness facial paresthesias loss of deep tendon reflexes ECG changes same as in hyperkalemia somnolence --> coma and muscular paralysis
Tx. of hypermagnesemia
IV calcium gluconate for emergent sx
saline + furosemide
dialysis in renal failure pts
intubation
normal plasma phosphate conc.
3.0-4.5 mg/dL
decreased intestinal absorption of phosphate due to..
alcohol abuse (MCC) vit D deficiency malabsorption excessive use of antacids TPN and/or starvation
increased renal excretion of phosphate due to…
excess PTH states hyperglycemia oncogenic osteomalacia renal tubular acidosis hypokalemia/hypomagnesemia
other causes of low phosphate levels?
respiratory alkalosis anabolic steroids severe hyperthermia DKA (MCC) hungry bones syndrome
Tx. of hypophosphatemia
oral supplementation - neutra-phos capsule, K-phos tablets, milk
severe - parenteral supplementation
CF of hyperphosphatemia
metastatic calcifications and soft tissue calcifications - binds calcium (hypocalcemia)
Tx. of hyperphosphatemia
phosphate binding antacids contatining AlOH or carbonate
anion gap
Na - (HCO3 + Cl)
- normally between 5-15
- represents ions present in serum but unmeasured
effects of acidosis
right shift of O2-Hb dissociation curve depresses CNS decreases pulmonary blood flow arrhythmias impairs myocardial function hyperkalemia
effects of alkalosis
decreases cerebral blood flow left shift on O2-Hb curve arrythmias tetany seizures
an (1) in lactate results in a (2) in HCO3-
1 - increase
2 - decrease
what causes an increased AG acidosis?
- ketoacidosis - DKA, starvation, alcohol
- lactic acidosis
- renal failure - decreased NH4 excretion
- intoxication
acid-base defect in salicylate overdose
primary respiratory alkalosis AND AG metabolic acidosis
what causes a normal AG acidosis (hyperchloremic)
- renal tubular acidosis - decreased HCO3 absorption or decreased production of HCO3
- carbonic anhydrase inhibitors
- GI loss - diarrhea, pancreatic fistulas, small bowel fistulas, ureterosigmoidostomy
- adrenal failure
MCC of non-AG acidosis?
diarrhea
proximal tubular acidosis
causes nonAG acidosis by decreasing reabsoprtion of HCO3-
- multiple myeloma
- cytinosis
- Wilson’s disease
distal tubular acidosis
inability to make HCO3-
caused by: SLE, Sjogrens and ampho.B
CF of metabolic acidosis
hyperventilation - Kussmaul breathing
decreased CO
decreased tissue perfusion
Winter’s formula
expected PaCO2 = 1.5 (HCO3) + 8 (+/- 2)
in Winter’s formula, if actual PaCO2 > calculated PaCO2…
metabolic acidosis with respiratory acidosis
in Winter’s formula, if actual PaCO2 < PaCO2..
metabolic acidosis with respiratory alkalosis
Tx. of severe metabolic acidosis
NaHCO3 –> tx. up to a pH of 7.20 (no higher)
saline-sensitive metabolic alkalosis
Urinary Cl < 20 = ECF contraction and hypokalemia
saline-resistant metabolic alkalosis
Urinary Cl > 20 - ECF expansion and HTN
causes of saline-sensitive metabolic alkalosis
Vomiting NG tube suction diuretics volume depletion villous adenoma of colon
causes of saline-resistant metabolic alkalosis
primary hyperaldosteronism Cushing's syndrome severe hypokalemia Bartter's syndrome diuretic abuse excessive black licorice consumption
Tx. of saline-sensitive metabolic alkalosis
IVF with normal saline and K+
Tx. of saline-resistant metabolic alkalosis
IVF will NOT help
- underlying cause must be addressed
- spironolactone may help
compensation in acute respiratory acidosis
HCO3- rises acutely -> 1 mmol/L for every 10 mmHg increase in PCO2
compensation in chronic respiratory acidosis
renal compensation takes about 5 days to complete –> HCO3- rises 4 mmol/L for every 10 mmHg increase in PaCO2
what is the main cause of respiratory acidosis
alveolar HYPOVENTILATION
major causes of alveolar hypoventilation (5)
- primary pulmonary disease - COPD, sleep apnea, CH, Obesity
- neuromuscular dz - myasthenia, ALS
- CNS - injury to brainstem, stroke
- drug-induced - opiods, sedatives
- respiratory muscle fatigue
signs of acute CO2 retention
headache
confusion
papilledema
effect of elevated PaCO2 on CNS
elevated PaCO2 = increased cerebral blood flow = increased ICP = generalized CNS depression
which situations in respiratory acidosis require intubation?
- severe acidosis
- PaCO2 > 60 or inability to raise PaO2 w/ O2
- deterioration in mental status
- respiratory fatigue
PaCO2 is primarily determined by…
- respiratory rate - any disorder that increases RR can lead to alkalosis
- tidal volume
9 major causes of alveolar hyperventilation:
- anxiety
- PE, pneumonia, pulm edema, atelectasis, effusion
- sepsis
- hypoxia - high altitudes
- mechanical ventilation
- pregnancy
- liver disease
- medications - aspirin
- hyperventilation syndrome
CF of respiratory alkalosis
- decreased cerebral blood flow - lightheaded/dizzy, anxiety, paresthesias, perioral numbness
- tetany
- arrhythmias
Tx. of respiratory alkalosis
inhaled mixture containing CO2
breathing into a paper bag
