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91 Cards in this Set

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range of normal values for Na, K, HCO3- and Cl- in serum
Na: 135-145
K: 3.5 - 5.0
HCO3: (CO2 content): 24-30
Cl-: 95-105
range of normal values for Na, K, HCO3- and Cl- in gastric aspirate
Na: 10-150
K: 10-20
HCO3-: 0
Cl-: 120-160
range of normal values for Na, K, HCO3- and Cl- in bile
Na: 135-145
K+: 5-10
HCO3-: 30-40
Cl-: 80-120
ISOTONIC TO SERUM
range of normal values for Na, K, HCO3- and Cl- in ileostomy aspirate (from small intestine)
Na: 120-140
K+: 5-10
HCO3-: 30-40
Cl-: 20-40
what is the normal serum osmolarity?
290 mOsm/L
extracellular osmolarity is calculated by osmolarity = {2 x [Na]s} + [glucose(mg)/dL / 18] + (BUN /2.8) -> normal if 290 +- 10
what is the total body sodium level (mEq/kg)
40 mEq/L
whaty is the normal adulst sodium requirement?
1-2 mEq/kg/day
what are 4 hormones/substrates that affect renal absorption and excretion of sodium and water?
Aldosterone
Antidiuretic hormone
what is the role of aldosterone?
controls sodium resorption in exchange for K+ and H+ secretion in distal tubules -> maintains both extracellular volume and osmolarity
what is the role of ADH?
increases tubular resorption of water at the collecting ducts
released from the posterior pituitary
what is the normal total body store of K+? where is the majority located?
normal total body store of K+ = 50-55 mEq/kg
98% is located intracellularly at concentraction of 150 mEq/L
extracellularly, concentration is 3.5-5.0 mEq/L
what regulates potassium levels and excretion?
circulating levels of aldosterone
cellular and extracellular K+
tubular urine flow rates
also acid-base disturbances
how do you relation bicarb buffering system to pH?
Henderson-Hasselbach eqn:
pH = 6.1+ log ([HCO3-]/[0.03xPaCO2])
7.4= 6.1+ log (24/1.20)
what effect does acidosis have on K+?
acidosis -> H+ moves from area of high concentration (extracellular) to low concentration (intracellular) causes K+ to move OUT of the cell
Alkalosis is the opposite
what is the K+ status in acidosis vs. alkalosis
acidosis -> hyperkalemia
alkalosis -> hypokalemia
what are the 3 components of F&E managment in op pts?
1. resuscitation = recognize and repair imbalances and defecits already present
2. replacement = provide for ongoing and additional losses that occur during course of therapy
3. maintenance = meet requirements for F&E intake that balance daily obligatory losses
what are ranges of different types of output?
12-15 ml/kg/day of urine
3 ml/kg stool water
0-1.5 ml/kg sweat
10 ml/kg combined insensible losses from lung and skin (increased with fever or higher ambient temps)
if all you need are maintainance fluids (IV), what can you use? and why?
5% dextrose in water
because kidney reabsorbs all NaCl that it needs
what should you use for replacement fluids?
0.45% or 0.9% normal saline + 20 mEq KCl
what preop test should you do in someone with COPD
ABGs
what preop test should you do in someone with chronic renal disease
BUN, serum creatinine, electrolytes
what condition should you susptect in someone who is vomiting or has had prolonged gastric drainage?
Hypokalemic, Hypochloremic Metabolic Alkalosis
(remember: hypokalemia is associated with alkalosis)
pt needs replacement of volume, K+ and Cl-
in this situation, what happens if the urine pH is acidic?
what is this called?
profound K+ depletion if urine pH is acidic
= Paradoxical Aciduria
name 4 situtations in which 3rd space fluid losses can be present
peritonitis (bacterial or chemical)
intestinal obstruction
extensive soft tissue inflammation
trauma
what kind of loss is this (___tonic)
what should be used for replacement?
this is an isotonic loss
LR (a balanced salt solution) should be used for replacement
what are some clinical signs of hypovolemia?
Hemodynamic changes: tachycardia, narrowed pulse pressure, hypotension
Decreased urine output (<0.5 ml/kg/hr)
Lab evidence: increasing hematrocrit, serum BUN:creatinine > 20:1, urine Na concentration < 20mEq/L
what are hte F&E goals during surgery?
Goal: Tissue perfusion and maintain circulating volumes
How are these monitored?
Urine flow rates
central venous or pulmonary arterial pressures
when does 3rd spaced fluid accumulation usually resolve post-operatively?
POD 3 -> expect diuresis and wt loss
how can you differentiate prerenal azotemia (low intravascular volume) from acute renal injury?
Prerenal azotemia:
Urine Na <20 mEq/L
BUN:creatinine >20:1
urine osmolality > 400 mOsm/L
Acute Renal Injury:
Urine Na increases (>40mEq/L)
BUN:creatinine <10:1 (because creatinine starts to rise)
urine osmolality approaches plasma osmolality
when should LR NOT be use for a replacement fluid? why not?
LR should not be used to replace gastric loss d/t vomiting or NG tube sxn
Because there isn't enough Cl- in LR, so it won't correct the Hypochloremic hypokalemic metabolic alkalosis that occurs
what should be used instead?
1/2 NS + 20 mEq KCL/L
Note:
Glucose solns should not be used to correct volume deficits d/t osmotic diuresis induces by hyperglycemia
what is a good indication of adequate repletion of vascular volume
urine output at rates greater than 0.5ml/kg/hr
what are 3 major groups of cuases of Hyponatremia. give a few examples of each
1. Dilution (accumulation of excess water): hypotonic fluid replacement for GI or 3rd space losses, too much ADH
2. Excessive renal loss of Na: Thiazide diuretics, Metabolic alkalosis, Ketoacidosis, Adrenal insufficiency, Salt-wasting nephropathy
3. Artifactual: hyperlipidemia, hyperproteinemia
what are the primary clinical manifestations of Hyponatremia?
CNS dysfunction
what are cut-off levels of Na and what S/Sx do you expect?
Serum Na od 130-120 (acute drop) -> irritability, weakness, fatigue, increased deep-tendon reflexes, and muscle twitches
But completely ASx if developed slowly
Serum Na < 120, if untreated -> seizuers, coma, areflexia, and death
what diuretic causes hyponatremia and how?
Thiazide diuretic - blocks reabsorption of NaCl in cortical-diluting segment.
But there is still resorption of salt in ascending loop of Henle, so urine can be very concentrated.
so there is water retention with loss of Na, K, and Cl
what endocrine disorder can cause hyponatremia?
SIADH
tx: Demeclocyline or Lithium carbonate
how do you estimate the amount of sodium needed to correct hyponatremia?
mEq Na+ needed = (140- measured serum Na+) x TBW
where TBW = 0.6 x body wt(kg)
at what rate should this be given?
not more thatn 1/2 the total calculated amt of Na needed is give in the first 12-18 hours
the rest can be given over the next 24-48 hours with normal saline
what can happen if correction is too rapd? what rate is too rapid?
Too rapid = > 12 mEq/L/day
can cause Osmotic Demyelination Syndrome
what are signs of acute volume loss (hypovolemia) vs. chronic water loss?
Acute volume loss: tachycardia, hypotension, and decreased urine output
Gradual water loss: loss of skin turgor, thirst, altered body temp, and changes in mental status
what is the consequence of hypervolemia in most people?
high urin output
what are possible complications? in whom do these occur?
complications can occur in elderly and those retaining fluid
complications: CHF and acute peripheral edema
how does CHF occur in young people
occurs with sudden fluid excess. can occur in young people with compromised cardiac function d/t shock with trauma, acid-base disturbances, or blood transfusions
what happens if fluid excess occurs more slowly?
can get pulmonary or peripheral edema instead of CHF
what can be a complication of Acute Peripheral edema?
usually causes little harm
but if it pesists, can lead to pulm edema --> decreased oxygenation
edema also breaks down tight jxns --> further edema
Definition of hyponatremia
serum sodium < 130 mEq/L
what are the symptoms of hyponatremia
irritability
increased TDReflexes
muscle twitching
seizures if severe
causes of hyponatremia (4)
Hyperglycemia --> artifact
Total body sodium defecit
Total body sodium excess
Normal body sodium level
how can total body sodium excess cause hyponatremia?
these pts have inability to excrete Na and H2O correctly
Occurs with renal failure, cirrhosis, and stress
Can see evidence of fluid overload: pulm and pitting edema
how can pts with normal body sodium level become hyponatremic?
if patient is unable to voluntarily control sodium and water intake
also SIADH - do not excrete excess free water appropriately
what is the definition of hypernatremia?
serum sodium > 145
what are S/Sx of hypernatremia
volume depletion sx: tachy, hypotension, lethargy, agitation
and signs of dehydration: dry mucus membranes and decreased skin turgor
what can cause hypernatremia
often in hospitalized pt d/t administration of salt-containing fluids(NS)
loss of water can also be d/t NGtube drainage, sweating, trach, diarrha, diuresis
how do you know how and when to treat hypernatremia?
calculate the Free Water Defecit =
0.6 x body wt x [1-(140/Na)]
what do you to treat hypernatremia?
free water infusions --> monitor signs of volume defecit
but if total body water is already increased, decrease the amount of sodium that is being administered
what is the definition of hypokalemia?
serum K < 3 mEq/L
what are the S/Sx of Hypokalemia?
Depression of neural, cardiac, and muscle fxn
what do you see on the EKG in hypokalemia?
Arrhythmias
Flattened or inverted T waves
then U waves
ST segment depression
PR interval elongates
QRS complex widens
what are the neuromuscular changes of hypokalemia?
weakness
what is the GI problem with hypokalemia?
can develop an ileus
what are the causes of hypokalemia?
unusual in healthy person because there are large body stores
can be causes by starvation, anorexia, or diuretics
can also lose K through NG tubes, diarrhea, and fistulas
what is the treatment for hypokalemia?
FIRST correct the deficit of K
then correct the underlying problem
can do a central infusion (not peripheral, because that causes irritation)
what is the definition of hyperkalemia?
serum K+ > 6 mEq/L
what are the S/Sx of Hyperkalemia?
Hyperexcitability
GI tract: hypermobility --> nausea, cramping, diarrhea, vomiting
Heart: peaked T waves and widened QRS. can lead to heard block and eventually diastolic cardiac arrest
how likely is hyperkalemia to occur?
almost impossible in someone with normal functioning kidneys
what are causes of hyperkalemia?
in hospital: insufficient renal function and excess K+ (iatrogenic or endogenous)
Can occur with massive blood transfusions and GI bleeding
Acidosis can cause acute severe hyperkalemia
what is the treatment for hyperkalemia?
1. Calcium --> stabilizes cell membranes, avoid arrhythmias
2. Bicarb and insulin --> lowers serum K+ levels by moving K+ back into cells
3. Ion-exchange resins --> to remove excess K+ from body by exchanging K+ for Na+ ions
4. Dialysis - very effective, but invasive
what ist the definition of hypochloremia?
chloride < 90 mEq/L
what can cause hypochloremia?
high GI fluid losses (prolonged vomiting, NG tube sxn) --> loss of lots of H+ and Cl- ions
can also be due to dilutional states after admin of hypotonic fluids
what are S/Sx of hypochloremia?
Loss of H+, Cl-, or water causes kidneys to retain sodium --> loss of K+ and Cl- and retention of HCO3- --> severe HYPOCHLOREMIC HYPOKALEMIC METABOLIC ACIDOSIS
what is the treatment for hypochloremia?
NaCl solutions and with KCl if K is low
what is the definition of hyperchloremia?
Cl > 110 mEq/L
what are the causes of hyperchloremia in hospitalized patients?
to much Cl- in IV solutions
Note: Chloride in normal saline (154 mEq/L) is much higher than in plasma (90-100 mEq/L)
what are S/Sx of hyperchloremia?
increased Cl- causes HCO3- to go into cells to keep plasma electrically neutral --> METABOLIC ACIDOSIS
this metabolic acidosis can also be caused by aggressive diuresis after giving NS by concentrating the plasma
what is the treatment for hyperchloremia?
stop giving high levels of Cl-
may need to give ree water to return plasma to normal so that kidneys can then correct the electrolyte abnormality
what causes of deficit of bicarb (leading to metabolic acidosis)?
Lack of O2 delivery to tissues --> production of Lactic Acid that is then buffered with HCO3-
With Renal Failure, kidneys can't excrete metabolic acids produced and cannot prodice HCO3-
What is the treatment for low bicarb?
Correct the oxygen delivery problem
If there is severe acidosis (pH <7.2) may need to administer bicarb to raise pH and allow for normal organ fxn
If renal failure cannot be corrected, then diuresis
what is the common role of Magnesium?
Co-factor for many enzymes
Also affects neuromuscular function
Where is magnesium stored?
At least half in bone
Most of the remaineder is INTRAcellular
Note: Mg++ is the commonest intracellular divalent cation and most is bound to ATP
what is the normal range of serum Mg++?
1.5-2.5 mg/dL
what causes hypomagnesemia to be common in surgical patients?
They are often in starvations tates and may also have GI losses or absorption defects
what happens to some other ions when Mg++ is low?
these is alos loss of Potassium and Phosphorys - the 2 other major elents in cells --> cells end up decreasing in size to maintain normal intracellular composition
Low Mg++ also causes hypocalcemia by causing a decrease in PTH secretion
what are some other causes of hypomagnesemia?
chronic alcoholism (esp during withdrawl)
malabsorption (esp steatorrhea)
acute pancreatitis
improper hyperalimentation
endocrine disorder
can be a side effect of many drugs
what are S/Sx of low Mg++?
Increased deep tendon reflex
Tetany
Asterixis
Tremor
Chvostek's sign
Ventricular ectopy
Vertigo
Tachycardia
Arrhythmias
what is the treatment?
Acute Tx: MgSO4 IV
Chronic Tx: Magnesium oxide PH (but causes diarrhea)
correct the underlying cause
what can cause Hypermagnesemia?
Renal failure
Injury that causes rhabdomyolysis (crush injuries, severe burns)
Dehydration
Severe metabolic acidosis
After treatment for eclampsia
what are S/Sx of hyperMg++?
Respiratory failure
CNS depression
Decreased deep tendon reflexes
what is the Tx for HyperMg?
Calcium gluconate IV
insulin + glucose
Dialysis
(similar to treatment of hyperkalemia)
Furosemide (lasix)