Fluids And Electrolytes Flashcards
Alkalemia is pH over?
7.44
pH over 7.40, you are dealing with?
Alkalosis
pH under 7.40, you are dealing with?
Acidosis
Bicarb over 25, you are dealing with?
Metabolic alkalosis
These are general rules since infants have lower bicarb levels than adults
Bicarb under 25, you are dealing with?
Metabolic acidosis
These are general rules since infants have lower bicarb levels than adults
pCO2 is over 40, you are dealing with?
Respiratory acidosis
pCO2 is under 40, you are dealing with?
Respiratory alkalosis
Equation for serum osmolality?
2*Na (mEq/L) + [BUN (mg/dL) / 2.8] + [Glucose (mg/dL) / 18]
If you are given electrolytes in the question, what should you do?
Calculate serum osmolality
What is normal serum osmolality?
265-285
Higher than this: Hyperosmolar or hypertonic
Lower than this: Hypoosmolar or hypotonic
What is the formula to correct metabolic acidosis (how much bicarb)?
mEq Bicarbonate = Weight * 0.3 * the base deficit
What is the renal threshold for bicarb in term neonates?
21 mEq/L (Their kidneys haven’t fully developed)
What is the primary cause of respiratory acidosis?
Hypoventilation
What does the pCO2 do in respiratory acidosis?
Elevates (Ex: pH 7.15, pCO2 75)
What is a common example of something that would blunt the respiratory drive, resulting in hypoventilation and respiratory acidosis?
CNS dysfunction
What is the primary cause of respiratory alkalosis?
Hyperventilation
What happens to the pCO2 in respiratory alkalosis?
Decreases
Example: pH 7.55, pCO2 25
What is a common example of something that would cause hyperventilation (to increase O2) resulting in blowing off too much CO2 leading to respiratory alkalosis?
Pneumonia
What 2 things can cause metabolic acidosis?
Increased acids or decreased bicarbonate
What happens to bicarb in metabolic acidosis?
It is depleted
Example: pH under 7.4, bicarb under 25
What is the leading cause of metabolic acidosis in kids?
Diarrhea
What happens to the bicarb in metabolic alkalosis?
It is high
Example: pH over 7.4, bicarb over 25
What are 4 common causes of metabolic alkalosis?
- Vomiting
- Prolonged NG suction
- Pyloric stenosis
- Cystic fibrosis
What does the body try to do to minimize any changes in the pH?
Buffer…if the lungs caused the problem, the kidneys will try to fix the pH and vice versa
Are compensatory mechanisms complete?
No, incomplete
Compensation for metabolic acidosis?
Too much acid and it is the kidneys fault…so lungs help and blow off acid (CO2)
Acidemia is pH under?
7.36
What is the pH and pCO2 in compensated metabolic acidosis?
Low pH and lowered pCO2 (Ex: pH 7.20, pCO2 25)
What is a clinical scenario that could cause compensated metabolic acidosis?
Septic shock (for example, secondary to meningococcemia)
Compensation for metabolic alkalosis?
Too much bicarb, usually GI’s fault…so the kidneys will have to excrete more bicarb to increase pH (if kidney was problem in first place, it would be a big issue)
What is a classic example of a cause of metabolic alkalosis in an infant?
Pyloric stenosis or NG tube
How does pyloric stenosis or an NG tube lead to a hypochloremic metabolic alkalosis?
- Loss of stomach juices leads to loss of hydrogen ions (alkalosis) and loss of chloride ions (hypochloremia)
- Contraction of extracellular fluid leads to increased bicarb reabsorption in the kidneys causing worsening alkalosis. The kidneys retain chloride, so urine chloride is under 10
What is the respiratory response to metabolic alkalosis?
Hypoventilation (to retain CO2)… But hypoventilation can never adequately compensate for metabolic alkalosis (you can’t completely stop breathing)
Patient with pyloric stenosis, given labs, which one is inconsistent with diagnosis?
Hypochloremic, hypokalemic, metabolic alkalosis…high pH, low serum chloride, low serum sodium, low serum potassium, hyperbilirubinemia
High potassium would be inconsistent (but remember that a heel stick could have high potassium due to hemolysis, not pathology)
*Write down adjective description of lab values, then cross off ones which are consistent
What is the compensation for respiratory acidosis?
Since lungs didn’t breath enough and held of to too much CO2 (acidosis), the kidneys will step in and hold on to bicarb
What is pH, CO2, and bicarb for respiratory acidosis?
Low pH, high CO2, and high bicarb (Example: pH 7.2, CO2 25, bicarb 32)
What is the compensation for respiratory alkalosis?
Lungs blew off too much acid (CO2), so the kidneys need to get rid of bicarb to decrease the alkalosis
What is pH, CO2, and bicarb with compensated respiratory alkalosis?
pH is high, CO2 is low, bicarb is low (Example: pH 7.48, pCO2 20, bicarb 15)
What acid-base disturbance would occur in a kid who recently moved to Colorado?
Respiratory alkalosis…they would breath rapidly because of the the air…the hypoxia triggers hyperventilation leading to respiratory alkalosis
What do you do if you have a patient with acidosis and you are given serum sodium, chloride, and bicarbonate?
Calculate the anion gap
What is the equation for anion gap?
Anion gap = Serum sodium - (Chloride + Bicarb)
What does the anion gap measure?
Ions that aren’t accounted for in routine labs, like protein, organic acids, phosphate, sulfate, and lactic acid
What is a normal anion gap?
Between 8-12 mEq/L
With metabolic acidosis and a normal anion gap, what happens to the serum chloride?
It is elevated
What can cause metabolic acidosis with a normal anion gap?
Loss of bicarbonate, kidney dysfunction, diarrhea, addition of hydrochloric acid, renal tubular dysfunction
What is the most common cause of a non-gap metabolic acidosis in children?
Diarrhea
If you get a kid with a normal anion gap metabolic acidosis, but no diarrhea, what should you think?
RTA (almost always 1 or 2)
Mnemonic for normal anion gap acidosis?
USEDCARP Ureterostomy Small bowel fistula Extra chloride Diarrhea Carbonic anhydrase inhibitor use Adrenal insufficiency Renal tubular acidosis Pancreatic fistula
Failure to thrive, polyuria, constipation, metabolic acidosis (pH
RTA
What is wrong is type 1 (distal) renal tubular acidosis, or classic RTA?
Proximal tubule is fine (keeps all the bicarb it needs to), but the distal tubule doesn’t do its job and H isn’t allowed into the urine compartment inside the distal tubule
What does the urine pH do in type 1 RTA?
Urine high pH (always greater than 5.5) and can’t be acidified
What organ is the key to acid-base metabolism?
Kidney (more so than breathing)
What does the proximal tubule of the kidney do?
Boxes and takes Bicarb Back in
What does the distal tubule in the kidney do?
Arranges for H/Acid to leave the building
What is the acid-base/metabolic derangement with distal RTA?
Metabolic acidosis associated with hyperchloremia and hypokalemia
What is the problem with type 2 (proximal) RTA?
Caused by the inability of the proximal tubule to take back its bicarb (resulting in excessive bicarb in the urine)…the distal tubule can still do its job and show the H+ to the door (urine)
What is the urine pH in type 2 (proximal) RTA?
Urine pH is less than 5.5
What is type 3 RTA?
Rarely used as a classification today because it is thought to be a combination of type 1 and type 2
What causes type 4 RTA?
Resistance to aldosterone (or aldosterone deficiency)
What electrolyte is off in type 4 RTA?
Hyperkalemia (remember this is due to resistance to aldosterone or aldosterone deficiency)
What is acidosis with an elevated anion gap usually due to?
Overproduction of organic acids, ingestion, inability to excrete acid (like in renal failure)
What happens to the serum chloride in acidosis with an elevated anion gap?
Serum chloride is normal
What may be mimicked by use of potassium-sparing drugs like spironolactone?
Type 1 (distal) RTA
What is mimicked by the use of carbonic anhydrase inhibitors like acetazolamide?
Proximal (type 2) RTA
What is the classic mnemonic for conditions that are associated with acidosis and an elevated anion gap?
MUDPILES Methanol Uremia Diabetic ketoacidosis Paraldehyde Ingestion: Iron/Isoniazid Lactic acid Ethanol/Ethylene Glycol Salicylates
Why is sodium so important and what organ does it affect if it shifts?
It maintains osmolality
Shifts impact the brain (either swelling of contractions)
What is the daily requirement for sodium?
3 mEq/kg/day
How much sodium do preterm infants need?
May require 2-3 times normal amount (3 mEq/kg/day) because of renal immaturity and rapid growth
What is hypernatremia?
Serum sodium over 145 mEq/L
What 2 situations cause hypernatremia?
- Sodium excess
2. Water deficit
What 5 things can result in sodium excess and hypernatremia?
- Improper mixing of formula (not enough water)
- Ingestion of sea saltwater
- Excessive sodium bicarb after resuscitation
- Breast milk with excessive sodium
- Iatrogenic
What 2 things can result in water deficit and hypernatremia?
- Diabetes insipidus
2. Diarrhea (both sodium and water are lost, but more water than sodium)
What % of a fetus’s body weight is water?
90%
What happens to total body water as we age?
The percentage decreases
In adolescents and adults, what is the TBW as a percentage of body weight?
60%
What is total body water broken down into?
Intracellular and extracellular fluids
How is equilibrium maintained between intracellular and extracellular fluid compartments?
Diffusion across cell membranes based on serum osmolality between these two compartments
Is extracellular fluid maintained in hypernatremia?
Yes
Why can hypernatremia cause pulmonary edema?
If there is hypernatremia, water is drawn out of the intracellular compartment, resulting in increased extracellular volume, causing pulmonary edema
What do kids with diabetes insipidus do?
Urinate a lot
Diabetes “I am sipping and sipping this”… Drink a lot too because they are peeing a lot
What are the 2 types of DI?
Central (lack of ADH), nephrogenic (resistance to ADH)
Child that is urinating profusely, but has no sugar in the urine…
DI
What do the labs show in DI?
High serum osmolality with inappropriately dilute urine
How do you differentiate DI from hypernatremic dehydration?
Check urine
DI kids have continued urination with dilute urine
Dehydrated kids have decreased urination with concentrated urine
What is the inheritance of nephrogenic DI?
X-linked (so it’s only found in males)
What happens in nephrogenic DI?
Kidney doesn’t respond to vasopressin (ADH), results in dilute urine
Which form of DI responds to exogenous vasopressin?
Central (nephrogenic won’t respond)
If they describe DI with a familial pattern among males, which type is it?
Nephrogenic
What is hyponatremia?
Serum sodium less than 130 mEq/L
What are the 3 categories of hyponatremia?
- Hypovolemic
- Euvolemic
- Hypervolemic
What is the best study to order to determine the type of hyponatremia you are dealing with?
Urinary fractional excretion of sodium (FENa)
If sodium is under 120, what can patients present with?
Lethargy and seizures
Hyponatremia is the result of what 2 mechanisms?
- Loss of sodium
2. Increased water (dilutional)… Either too much taken (polydipsia) or too little let out (SIADH)
How can hyponatremia result with sodium and water being lost?
More sodium is lost than water…result is still hyponatremia
An example of this is 3rd space losses post op
What happens to urine sodium with hyponatremia secondary to GI losses?
Low urine sodium (under 10)…kidneys hold on to sodium
What does SIADH do to urine output?
Diminished urine output
*Anti-diuretic is opposite of diuretic…think of it as syndrome of I am definitely hydrated cause I’m not peeing
When do you have appropriate ADH and concentrated urine?
Whenever there is high serum osmolality and you want to retain fluid
What can cause SIADH?
Cerebral injury or insult like trauma or a tumor (pituitary produces ADH)
Also certain pulmonary or endocrine disorders can trigger SIADH
What drugs can lead to SIADH?
Chemotherapeutic drugs (like vincristine or cyclophosphamide) and antiepileptic carbamazepine
What is the mneumonic to remember causes of SIADH?
SIADH Surgery Infection Axon (neurological such as Guillain Barre, brain tumor) D (Day after, Post op, of any kind) H (Head and hemorrhage)
What is the sodium in SIADH and what causes it?
Hyponatremia…underlying problem is fluid retention, not excretion of sodium
What is potassium, urine sodium, and plasma volume in SIADH?
Normal serum potassium, elevated urine sodium (over 25 mEq/L or 25 mmol/L), plasma volume is increased
What are the expected lab values in SIADH for serum sodium, BP, urine output, and BUN/Cr?
Low serum sodium: 124 mEq/L
Elevated BP
Decreased urine output: Under 1 cc/kg/day
Normal renal function (Bun/Cr)
What can happen to ADH post operatively and what do you do about it?
Risk for increased ADH secretion…important to monitor for hyponatremia and restrict fluids appropriately
What is the urine osmolality and sodium concentration ins SIADH?
Urine will have high osmolality and high sodium concentration
How to differentiate SIADH from hyponatremic dehydration?
Serum osmolality…SIADH is overhydrated, so serum osmolality is low. Hyponatremic dehydration will have either normal or elevated serum osmolality
What happens to BUN in SIADH v. Hyponatremic dehydration?
BUN is elevated in dehydration and decreased in SIADH.
What happens to body weight in SIADH versus hyponatremic dehydration?
Body weigh increases in SIADH and decreases in dehydration
What is the preferred treatment for SIADH?
Fluid restriction
How is SIADH diagnosed?
Diagnosis of exclusion…may need to rule out other disorders leading to hyponatremia before you choose fluid restriction (which can be difficult in infants)
How fast is correction of SIADH?
It is slow no matter what
What can you do for SIADH is fluid restriction doesn’t work?
Furosemide and hypertonic saline
What drug can be given to kids 8 and older with SIADH?
Demeclocycline…blocks effects of ADH on kidney
*Since this is a derivative of doxycycline can only give to kids 8 or older
What drug blocks the effects of ADH, but is usually not recommended due to its side effect profile?
Lithium
What fluids are indicated if serum sodium is less than 120 mEq/L?
3% sodium chloride
Which type of diuretics are incorrect for treatment of SIADH?
Thiazides…they can lower sodium even further
Patient with head injury or meningitis, either imply or just say patient has SIADH, no neurological symptoms, treatment?
2/3 (0.66) maintenance fluids…use demeclocycline if there is no clinical improvement with appropriate fluid restriction
*Don’t pick maintenance, twice maintenance, or 1.5 time maintenance
A patient with diminished urine output who is taking in fluid in excess of urine volume will develop what?
Hyponatremia
- They will present you with a clue that renal disease is present (like elevated creatinine)
- Also likely present with edema and urine sodium over 20 mEq/L
What is the correct initial treatment for a patient who is oliguric and hemodynamically unstable (even in patients with renal failure)?
20 mL/kg of isotonic solution (normal saline, LR, packed RBC, or albumin)
After giving 20mL/kg of isotonic solution for a patient who is oliguric and hemodynamically unstable, what do you do next?
Once hemodynamically stable, adjustments would be based on the urine output, weight, and other symptoms included in question (including presence of pulmonary edema or other conditions)
What can chronic diuretic therapy result in?
Hyponatremia
Name 4 medications that cause hyponatremia
Vincristine, cyclophosphamide, chlorpropamide (oral hypoglycemic), thiazide diuretics
How does vincristine cause hyponatremia?
SIADH
How does cyclophosphamide cause hyponatremia?
Diminishes water excretion
How does chlorpropamide cause hyponatremia?
Stimulates vasopressin release
How do thiazide diuretics cause hyponatremia?
Blocks renal sodium and chloride reabsorption, decreasing the kidney’s ability to produce dilute urine
What is dilutional hyponatremia due to?
Water intoxication
What is the total body sodium in dilutional hyponatremia?
Normal
Is there intravascular volume depletion in dilutional hyponatremia?
No, no signs of this
Why can seizures occur with dilutional hyponatremia?
Due to cerebral swelling
What happens to the urine sodium concentration in dilutional hyponatremia?
Urine sodium concentration is increased
What is one of the most common causes of hyponatremia in infants?
Water intoxication…mostly due to excessive dilution of formula with water
What is the presentation of infants with water intoxication and hyponatremia?
Afebrile seizures, respiratory insufficiency, hypothermia
What can hyponatremic dehydration do to the brain?
Can cause pontine damage
*Hyponatremic and pontine both have an “o” in them
What should seizures in a patient with no history of seizures, no history of trauma, and no fever make you think of?
Metabolic causes…like hypoglycemia or hyponatremia
What are some causes of seizures due to hyponatremia or hypoglycemia?
Kid who has spent a lot of time swimming (especially if young kid cause they swallow a lot of water), malnutrition, hypotonic IV fluids, glucocorticoid deficiency, hypothyroidism
What happens to the total body sodium in dilutional hyponatremia?
Total body sodium is normal in dilutional hyponatremia
What 2 scenarios can present like dilutional hyponatremia?
- Third spacing of fluid
2. Renal salt wasting
What can cause third spacing of fluid?
- After extensive surgery
2. Nephrotic syndrome
Third spacing of fluid after extensive surgery can be due to what 2 things?
- Endothelial damage and/or leakage
2. Hypoalbuminemia and low oncotic pressure
In nephrotic syndrome, what is the urine sodium concentration?
Low…less than 10 mEq/L
What is an important feature of nephrotic syndrome?
Edema
In renal salt wasting, what are two presenting features from fluid and electrolytes perspective?
Hyponatremia, but also hypovolemia
Kid who is post op for resection of a craniopharyngioma has hyponatremia, elevated serum creatinine, increased urine output, urine sodium greater than 100 mEq/L, a during osmolality of 350…diagnosis and treatment?
Don’t assume SIADH/Fluid restriction…with SIADH urine output is low and urine sodium concentration is also low…hypervolemia is the result and fluid restriction is the correct management
With elevated urine output and elevated urine sodium, the correct diagnosis is cerebral salt wasting, and the correct treatment is replacement of fluid and sodium losses
Dilutional hyponatremia and 3rd spacing of fluid both have hyponatremia, but how are they different?
Urine sodium…high in dilutional hyponatremia and low in 3rd spacing of fluid
Steps for low sodium value and determining if total body sodium is normal, low, or elevated (pseudohyponatremia)?
- Get situation with high triglycerides and/or plasma proteins (typical example is nephrotic syndrome)
- TG’s take up lots of room…less water, but volume is same (labs report sodium per volume, not sodium per water…so sodium level is reported low since water is the only part that contains sodium)…So the sodium level in circulation really is normal
- Lots of water is outside circulation in anything causing edema…there is more water than usual and this water does have sodium…so the total body sodium is elevated
What is the measured sodium with edema secondary to decreased oncotic pressure?
Low
What is the daily requirement for potassium?
2 mEq/kg/day
What is hypokalemia?
Serum potassium less than 3.5 mEq/L
Kid with a history of diarrhea presenting with muscle pain, weakness, paralysis, constipation and ileus, or polyuria?
Hypokalemia
What GI issue causes hypokalemia and what GI issue does hypokalemia result in?
Hypokalemia can be caused by diarrhea
Hypokalemia results in constipation
What are some causes of hypokalemia?
- Poor intake (anorexic nervosa)
2. Loss: GI (Vomiting/Diarrhea) or Renal (diuretics, renal tubular disorders, or excess aldosterone)
What are some EKG changes with hypokalemia?
- Flattening of T waves
- ST depression
- Premature ventricular beats
- U wave just after T wave (extreme cases)
Boy with 2-3 day history of vomiting and diarrhea, taken water and juice, but progressively weaker, difficulty sitting or standing without support…why is he weak?
Hypokalemia…any question asking for a specific explanation for weakness with vomiting and dehydration, it’s hypokalemia
*Don’t be temped to pick dehydration or hyponatremia
In emergency situations, how is potassium replaced?
Use KCl 0.5-1.0 mEq/L per kg over an hour…maximum is 40 mEq/L
*This is only in emergency/urgent situations
For mild cases of hypokalemia how do you replace potassium?
Oral replacement
If hypokalemia is due to dehydration, how do you fix it?
Fluid replacement with added potassium
Is a patient is hypokalemic and acidosis is a factor, what do you use to correct it?
Potassium acetate
If a patient is hypokalemic and hypophosphatemia is an issue, what do you use?
Potassium phosphate
What is required during IV infusion of KCl?
EKG monitoring
What other electrolyte abnormalities besides hypokalemia can present with weakness and EKG changes?
Hypocalcemia and hypomagnesemia
What presents with muscle weakness and prolonged QT interval
Hypocalcemia
What can occur in patients with diarrhea and shows a prolonged PR or QT interval on EKG?
Hypomagnesemia
Which 2 electrolyte abnormalities present with muscle weakness, but no EKG changes?
Hypoglycemia and hyponatremia
What is hyperkalemia?
Serum potassium greater than 5.0 mEq/L
Name 4 causes of hyperkalemia?
- Excess intake
- Not enough out (renal failure, hypoaldosteronism)
- Redistribution: Acidosis (H goes into cell, K goes out of cell)
- Cell breakdown (pseudohyperkalemia)
What is the initial EKG finding with hyperkalemia?
Peaked T waves
With substantially high potassium levels (10 or greater) what will you see on EKG and what is this associated with?
Absence of P waves and widened QRS complex…associated with electromechanical dissociation (EMD)
What can the widened QRS complex from hyperkalemia be misinterpreted as and how do you distinguish?
Idiopathic bundle branch block or ventricular tachycardia
- Wouldn’t describe muffled heart sounds or absence of pulses in IBBB
- Pulseless state is possible with ventricular tachycardia at rates of 200 or higher, but no muffled heart sounds
How do you treat milder cases of hyperkalemia?
Glucose and insulin, sodium bicarbonate, inhaled albuterol, IV furosemide (Lasix), oral polystyrene resin
If you are presented with a patient with potassium greater than 10 who has EKG changes, then what is the correct treatment?
IV calcium chloride…dialysis is also an option
Infant with abdominal mass who becomes hypotensive, he has non-palpable pulses and distant heart sounds, EKG shows wide QRS complex…appropriate immediate treatment?
Abdominal mass is adrenal tumor, causing adrenal failure and hyperkalemia…results in electromagnetic dissociation (EMD)… Most appropriate immediate treatment is IV calcium chloride
*Dont pick NS bolus to treat shock or hydrocortisone IV or pressor like dobutamine
Alkalosis and potassium…go
- Alkalosis is high pH, so little H+ in ECF
- H+ in cells (ICF) move out to ECF to balance things
- To replace the H+ leaving cells, K+ goes from ECF into ICF
- During alkalosis, K goes into cells and you get lower measured K levels
What happens to serum potassium and total body potassium in alkalosis?
During alkalosis, K moves into ICF and H moves to ECF…lower measured serum potassium and total body potassium is unchanged (it’s just hiding in the cells)
Acidosis and potassium…go
- Acidosis is low pH, so lots of H+ floating around in ECF
- These excess H+ move into the ICF
- When this happens, the K+ moves out of the cells into the ECF, so there is increased K in the ECF
What is serum and total body potassium in acidosis?
In acidosis, the H+ moves into the cells and the K moves out of the cells, so you have high serum potassium and normal total body potassium
What are signs of 5% dehydration?
Tachycardia, decreased tear production, decreased urinary output, increased urine concentration
5% dehydration means the kid is short how many mL/kg?
50mL/kg
Can 5% dehydration be corrected orally?
Yes
If you have to do IV fluids to correct 5% dehydration, how do you do it?
Add 50mL/kg to the maintenance fluid and give over 24 hours (half of the total given over first 8 hours and half given over next 16 hours)
How do you calculate maintenance fluid for a day?
100mL/kg/day for first 10kg, then 50mL/kg/day for next 10kg, then 20mL/kg/day for each kg after that
How do you calculate maintenance fluid rate hourly?
4mL/kg/hr for first 10kg +
2mL/kg/hr for next 10kg +
1mL/kg/hr for each additional kg
Signs of 10% dehydration?
Tachycardia, sunken eyes, poor skin turgor, sunken fontanelle
10% dehydration means a kid is short how many cc/kg?
100cc/kg
How do you correct 10% dehydration?
Maintenance fluids plus 100cc/kg given over 24 hours
How are IV fluids given for 10% dehydration?
20cc/kg over an hour (emergency phase), then whatever is left over…give half over next 7 hours and other half over remaining 16 hours
Which are early and late signs of dehydration: hypotension, tachycardia, decreased skin turgor, bounding pulses?
Early: Tachycardia
Later: Hypotension, decreased skin turgor, bounding pulses
What level of dehydration would you see signs of shock, including delayed capillary refill time?
15% dehydration
How many cc/kg is the child short with 15% dehydration?
150cc/kg
What do you give to correct 15% dehydration?
Maintenance plus the 150cc/kg
How do you give IV fluids to correct 15% dehydration?
Keep giving 20cc/kg boules until you see clinical improvement…then you give half of what is left over during next 7 hours and remaining half over next 16 hours
If you are presented with a patient in septic shock, they may require how many blouses of normal saline?
3 20mL/kg boluses or 60mL/kg total
For a patient in septic shock, if they ask you how much to give for a bolus, what would the correct answer be?
The total amount is based on findings on frequent reassessment
All oral rehydration fluids must contain what?
Glucose
Why do oral rehydration fluids have to contain glucose?
In order to cross microvillus membrane of GI tract, sodium has to be accompanied by glucose
Besides IV fluids what else do you do for a patient with moderate to severe dehydration (tachycardia and delayed capillary refill)?
Use oral rehydration fluid
How much sodium is in oral rehydration fluid and now should it be given?
75 mEq/L of sodium…rate should be 50mL/kg over 1-4 hours (even if given with dropper)
What type of oral rehydration is used for mild dehydration and how much sodium does it contain?
Standard maintenance hydration fluids, 50 mEq/L (this solution can be used once capillary refill is normalized in cases of severe dehydration)
If you have an infant with moderate to severe dehydration, can you use standard formula?
No… Need oral rehydration fluid
When do you use the BRAT diet?
Never, BRAT diet isn’t part of AAP recommendations, so it’s never the correct answer for managing acute gastroenteritis
Toddler with 2-3 days of vomiting and diarrhea…tolerating some clear liquids, dry mucous membranes and mild tachycardia, best management?
Start oral rehydration therapy, followed by a regular diet of complex carbohydrates, fruits, and veggies. Given usual formula at full strength
*Don’t pick bolus of isotonic fluids, BRAT diet, or diluted formula
What is isotonic dehydration?
Dehydration with serum sodium between 135-145
Why does isotonic dehydration result in a symptomatic patient?
Even though sodium and water are lost proportionately, more ECF than ICF fluid is lost…this causes symptoms
What is hyponatremic dehydration?
Dehydration with serum sodium under 135
What usually causes hyponatremic dehydration?
GI losses (like from diarrhea), but can have element of water intoxication
Question hinting at a dehydrated kid who was fed tea or water by grandmother…?
Hyponatremic dehydration
In which form of dehydration are patients more symptomatic on presentation and causes the greatest circulatory disturbances?
Hyponatremic dehydration
What form of dehydration might they mention poor skin turgor?
Hyponatremic dehydration
Why does hyponatremic dehydration cause the greatest circulatory disturbances and causes patients to be more symptomatic on presentation?
Because fluid moves from the ECF to the ICF
Why can patients with hyponatremic dehydration present with seizures?
Because free water moves into CNS cells with a serum sodium of 125
What is the initial treatment of hyponatremic dehydration?
Normal saline boluses
If normal saline boluses don’t work for hyponatremic dehydration, what do you do?
Hypertonic 3% saline in the ICU (hypertonic saline isn’t indicated as the initial treatment)
For hyponatremic dehydration, how do you replace sodium?
A = (Desired sodium - Measured sodium) x Weight x 0.6
Maintenance sodium is 3 mEq/kg/day
Add maintenance to the A…this is amount of sodium, needed over 24 hours
Because cystic fibrosis is associated with an increased loss of sodium and chloride in sweat, it can lead to what?
Hypochloremic hyponatremic metabolic alkalosis with dehydration
What is hypernatremic dehydration?
Dehydration with a serum sodium over 145
What is the cause of hypernatremic dehydration and what is the end result in terms of sodium?
Either due to water loss or sodium gain, end result is lots of sodium in ECF
What 2 things in history can cause hypernatremic dehydration?
- History of being fed improperly mixed formula
2. Severe rotavirus diarrhea (in olden days before rotavirus vaccine)
How do infants with hypernatremic dehydration present?
Irritable, lethargic, doughy skin, high pitched cry, eventual seizures
How does the body deal with hypernatremic dehydration?
Extreme thirst
What type of patients will not act on the thirst mechanism and likely develop hypernatremic dehydration?
Altered mental status: Unconscious, infant, psychotic
What happens with hypernatremic dehydration that diminishes the clinical signs of dehydration?
Water tends to go into the ECF
What % of dehydration should you assume with hypernatremic dehydration?
Assume 10% dehydration (regardless of clinical presentation)
What is the pathophysiology behind hypernatremic dehydration taking longer for symptoms to present for a given level of dehydration?
Due to osmotic pressures, fluid is drawn out of ICF and into ECF…less circulatory disturbances, longer for symptoms to present
Why can hypernatremic dehydration result in acidosis?
Due to release of hydrogen ions secondary to cellular destruction
How does hypernatremic dehydration lead to potential intracranial hemorrhage?
Intracellular dehydration results from water going to ECF (due to sodium) and this causes brain cells to shrink which can tear bridging blood vessels leading to intracranial hemorrhage
How can brain cells combat shrinkage due to hypernatremic dehydration?
The cells can take on idiogenic osmoles to lure the water back
How long does it take idiogenic osmoles to develop in hypernatremic dehydration?
Over 1-2 days, they don’t go away quickly either
Why should hypernatremic dehydration be corrected slowly over 2-3 days?
Avoid cerebral edema (idiogenic osmoles are present and take time to go away)… Don’t want water rushing in to meet the idiogenic osmoles
What should the decrease in sodium per day be to avoid cerebral edema when correcting hypernatremic dehydration?
No more than 10-12 mEq/L per day
What is the treatment goal for hypernatremic dehydration?
Correct the sodium concentration as well as circulating volume
If hypernatremic dehydration is chronic, what is the rate of sodium reduction?
0.5 mEq/L per hour
How do you correct severe hypernatremia (sodium of 170 or greater)?
Over 48-72 hours using 0.5 or 0.25 normal saline
What is done is there are signs of overcorrection with hypernatremic dehydration?
Hypertonic solution should be used as a brake to slow the train down
When can you give potassium when correcting hypernatremic dehydration?
Potassium should be held until urine output is established
Na: 125 K: 4.0 Cl: 85 BUN: 25 Glucose: 90 Urine Specific Gravity: 1.025
Hyponatremic dehydration
Decreased sodium and chloride
Increased BUN and specific gravity
Hyponatremic dehydration
Na: 152 K: 4.0 Cl: 120 BUN: 25 Glucose: 90 Urine Specific Gravity: 1.025
Hypernatremic dehydration
Increased sodium, chloride, BUN, specific gravity
Hypernatremic dehydration
Na: 120 K: 4.0 Cl: 108 BUN: 15 Glucose: 650 Urine Specific Gravity: 1.015
Pseudo-hyponatremia
Decreased sodium
Markedly elevated glucose
Pseudo-hyponatremia
Na: 120 K: 4.0 Cl: 85 BUN: 5 Glucose: 90 Urine Specific Gravity: 1.025
SIADH
Decreased sodium, chloride, and BUN
Increased specific gravity
SIADH
Na: 152 K: 4.0 Cl: 120 BUN: 25 Glucose: 90 Urine Specific Gravity: 1.002
Diabetes insipidus
Increased sodium, chloride, BUN
Decreased specific gravity
Diabetes insipidus
Na: 120 K: 4.0 Cl: 108 BUN: 15 Glucose: 90 Urine Specific Gravity: 1.010
Lab error
Sodium is decreased
Chloride is normal
Lab error
