L8 - Fluid And Electrolyte Balance Disturbance Flashcards
Body fluids are distributed in two
compartments.. what are they?
1.Extracellular fluids[ECF] Which includes
interstitial fluid & intravascular fluid
2.Intracellular fluids[ICF]
Percentages of water in the body
60% of body weight is water
Of which 40% from intracellular fluid
20% from ISF and plasma
What do fluids contain?
Water w/
- Electrolytes
- Minerals
- Cells
Measured osmolality
measured by freezing point depression (by osmometer)
It’s a measure of the osmotically active particles in a fluid
In plasma:
Na, K, Cl, HCO3, urea, glucose
Calculated osmolality
It’s a rough estimate of the plasma osmolality (285-295mmol/kg)
Determined by the equation:
2(Na) + urea + glucose (mM)
Osmolar gap
Difference b/w calc & meas osmolality - usually < 10mM
Fluid intake and fluid output
Processes that happen naturally to maintain the body’s homeostasis
Influences that regulate the fluid intake and output
What are the two cases where fluid needs to be regulated in the body
Hypervolemia and hypovolemia
Hypervolemia definition
Excessive fluid volume
Hypovolemia definition
Deficient fluid volume
Hypervolemia regulation
It will inhibit 1. ADH release 2. Aldosterone release 3. Thirst =increased urination and diluted urine
Hypovolemia regulation
It will stimulate: 1. Thirst 2. ADH release 3. Aldosterone release =decreased urination and concentrated urine
ADH fxn
Reduces water passage into urine
Aldosterone fxn
Promotes reabsorption of sodium and h2o
Daily fluid balance
Input- 2.6L
Output- 2.6L
(To maintain homeostasis)
Neutral balance
Input = output
Positive balance
Input> output
Can lead to edema
Negative balance
Input< output
Leads to dehydration
Hypo + hyper + iso
Reflect electrolyte balance
Contraction and expansion
Reflects the water balance
Fluid contraction
Deficient fluid
Fluid expansion
Excess fluid
What causes extracellular contraction
Not enough water and not enough sodium
What causes extracellular expansion
Too much water and too much sodium
What can also be a cause of fluid contraction and expansion
Aside from fluid disturbances or could also be a result of a change in electrolytes
(Water like to follow sodium)
Fluid status indication - physical exam
Mucous membranes and turgor
Fluid status indication - blood
Hematocrit (HCT) -> measures plasma volume
If someone is dehydrated the majority of his plasma is going to be molecules therefore hematocrit and hemoglobins are gonna be high
Fluid status indication - plasma
BUN -> blood, urea, nitrogen
Fluid status indication - urine
— Output (volume)
— Specific gravity: <1.003 -less concentrated urine prod.
>1.030 -more concentrated urine prod.
Fluid status indication - electrolytes
Mainly sodium and potasssium
Hypovolemia definition
Decrease in ECF volume ( intravascular and interstitial volume) - could be due to a loss in water and electrolytes or only water
What causes an isotonic volume deficit
- Decreased intake of isotonic fluids
- Excessive vomiting and diarrhea
- Excessive hemorrhage
- Excessive urine output
2,3,4 -> isotonic v. deficit bcz these are fluids that contain electrolytes so you’re losing isotonic fluid
Hypovolemia manifestations
— Decreased tissue perfusion (passage of fluid from circulation or lymphatics to tissue)
— Decreased blood volume (hypotension, tachycardia, oliguria)
— tissue dehydration ( loss of skin turgor, possible temperature elevation)
Hypovolemia lab studies in urine
Very concentrated urine low output Urinalysis may be normal Sodium conc. Low Chloride conc. Low Osmolality high Oliguria
Hypovolemia lab studies in blood
- High serum sodium =dehydration
- If sodium normal then patient is not dehydrated but hypovolemia (losing isotonic solution)
- high BUN/plasma creatinine level ( if not excreted = renal problems)
- HCT and plasma albumin high
Hypervolemia
Excess of isotonic fluid in the intravascular and interstitial spaces -isotonic fluid retention - secondary hyperaldosteronism - iatrogenic hypervolemia
Isotonic fluid retention
Oliguric state eg renal failure (no urine excretion)
Secondary hyperaldosteronism
Inappropriate renal reabsorption of water and sodium and increased renal secretion of potassium
Iatrogenic hypervolemia
If doctor gives patient too much fluid
Hypervolemia pathology
Excess in blood volume results in high capillary pressure
Hypervolemia clinical manifestations
Edema
Hypertension ( high cardiac output)
Bounding pulse (throbbing felt over arteries in the body due to forceful heartbeat)
Increased urinary output
Cation electrolytes
Na+
K+
Ca++
Mg+
Anion electrolytes
HCO3-
Cl-
PO4-
ICF major electrolytes
K+
ECF major electrolytes
Na+
What are the 4 headings which are discussed with disease
Intake
Compartmental shift
Output/loss
Possible artifact (normally, loses bcz of GI and kidney disturbances)
Hyponatremia
Too little sodium or too much water (diluted)
Hypernatremia
Too much sodium or too little water (concentrated)
How to evaluate water and Na balance problems
By comparing:
- serum sodium with urine sodium
- serum osmolality with urine osmolality
- careful clinical examination
When serum Na is low and urine Na< 20 mmol/l
This is due to dilution ( retaining fluid)
When serum Na is low and urine Na is >20 mmol/l
It is due to depletion (losing fluid)
Hyponatremia symptoms
Nausea/vomiting
Muscle weakness
Headache
Lethargic; possible seizure and coma is very low (<125 mmol/l)
Why do hyponatremia symptoms develop
Usually bcz of cells swelling and cerebral edema
Hyponatremia
- Low total body sodium
- Normal total body sodium
- High total body sodium
Low total body volume=
Low ECF volume/ hypovolemic
Normal total body sodium=?
Normal ECF volume/ euvolemic/ normovolemic
High total body sodium=?
High ECF volume/ hypervolemic
Hyponatremia with low body sodium
Na loss greater than body loss
Reduction in total body water
Dehydrated patients
Causes of hyponatremia with low body sodium
GIT disorders= vomiting /diarrhea /intestinal obstruction
Burns
Diuretic therapy
Adrenal insufficiency:
Infants/ elderly who can’t demand fluids
Patients who are vomiting/ comatose/ not allowed oral fluids
Profuse sweating or diarrhea- water loss more than the intake
Hyponatremia with normal body sodium
In SIADH (syndrome of inappropriate anti diuretic hormone)
Aka - euvolemic or dilutional hyponatremia
Water retained but no signs of fluid overload
Hypernatremia with high sodium concentrations
Signs and symptoms
Altered mental state Lethargy Irritability Seizures Fever Increased thirst
Hypernatremia with high sodium concentrations
Cause
Cellular dehydration Usually iatrogenic (caused by docs and nurses) ex. Administering hypertonic fluid >0.9% normal saline
Hypernatremia with low sodium concentrations
Lose more water than sodiums
Thirst mechanism increase water intake
Hypernatremia with normal body sodium causes
Increased insensible water loss- fever, excessive burns, mechanical ventilation Diabetes insipidus (causes body fluid imbalance) Drugs (lithium causes nephrogenic diabetes insipidus)
Why is potassium deadly?
It affects muscles and influence skeletal and cardiac activity (particularity the heart= arrhythmia)
Serum potassium
98% of body potassium is inside the cell
Normal serum concentration:
3.5->5.5 mmol/l
Hypokalemia signs and symptoms
Alkalosis Shallow respiration Irritability Confusion Weakness Arrhythmias Lethargy Weak pulse Low intestinal motility
Hypokalemia
Serum potassium below 3.5 mmol/l
Increase it but not more than 5.5
monitor it with an ECG
Hypokalemia causes
Diarrhea
Diuretics
Poor K intake
Steroid administration
Hyperkalemia signs and symptoms
Muscle cramps-> weakness-> paralysis Drowsiness Low blood pressure EKG changes Dysrythmias Abdominal cramps Diarrhea Oliguria
Hyperkalemia
Serum potassium higher than 5.5mmol/l
More dangerous than hypo bcz cardiac arrests are more frequent with high K+
Hyperkalemia causes
Renal disease
Massive cellular trauma (ex chemotherapy)
Addison’s disease (hypoaldosteronism-> stop K+ secretions)
Decreased blood pH (ex acidosis in DM)
