Fluids Flashcards
What fraction of body water is intracellular?
Extracellular?
Intracellular: 2/3
Extracellular: 1/3
The “first space” corresponds to?
Intravascular compartment
The “second space” corresponds to?
Intracellular space
The “third space” corresponds to?
Where fluid does normally accumulate (pleural cavity, peritoneal cavity, edema in extracellular space)
T/F? Fluids, electrolytes, and medications are not bioavailable in the third space
True
Define maintenance fluid therapy.
Replacement of ongoing losses of water and electrolytes under normal physiologic conditions
Define fluid replacement therapy.
Correction of existing water and electrolyte deficits.
Why do we care about a patients hydration status?
Dehydration causes decreased organ perfusion leading to organ damage
What factors lead to hypovolemia in surgical patients?
Patients are NPO prior to and post surgery
Blood loss from surgery
Third spacing in surgery
What fluid is the most physiologic replacement?
D5 1/2NS
What is the maintenance dose for fluids for a 90 kg patient?
120ml/hr 100ml/kg for first 10kg = 1000ml 50ml/kg for second 10kg = 500ml 20mg/kg for each kg over 20 kgs = 20 x 70 = 1400 1000+500+1400 = 2900 2900/24 hours = 120.83
Calculate the hourly maintenance dose of fluids for a 50 kg patient using the 4/2/1 rule.
4ml for kg 1-10 = 4x10 =40 2mk for kg 11-20 = 2x10=20 1ml/kg for each kg over 21 30x1 = 30 40+20+30 = 90ml/hour
Dehydrated patients need fluid replacement. How do you calculate how much replacement they need?
Estimate deficit.
Calculate real weight
Calculate deficit in kg
Add to maintenance dose
Estimate the fluid deficit for the following patients.
A man dehydrated to the point of tachycardia.
A woman dehydrated with dry skin and mucous membranes.
A man in hypovolemic shock.
Tachycardia = 6% fluid loss Dry = 3% fluid loss Shock = 9% fluid loss
Calculate the total IVF rate for a 60kg man who is dehydrated to the point of tachycardia.
6% deficit.
Calculate real weight - 60kg/.94 = 63.8kg
Calculate deficit - 1L=1kg - patient needs 3.8L of replacement
Maintenance = 1000+500+800=2300
2300+3800=6100
6100/24 hours =254mL/hour
When is a fluid bolus appropriate?
When you need to rapidly increase pressure –> sepsis, shock, ect.
A patient is having high volumes of fluid lost from his NG tube. You know you have to replace those fluids. What fluid is a good option?
NG tube losses have high Cl levels, so replace with fluid that has chloride. NS and RL are good options
What symptoms might you see in a patient whose fluid resuscitation was too vigorous?
Edema, dyspnea, JVD, lung crackles.
You ordered IV fluid resuscitation at a rate of 50mL/hour. Someone fucks up and gives 500mL/hour. Your patient is volume overloaded. How do you treat them?
Fluid restriction, diuretics, and lower rate of infusion.
What fluids are more commonly used, colloids or crystalloids?
Crystalloids
What are crystalloids?
Colloids?
Crystalloids contain electrolytes as the solutes. They can be isotonic, hypertonic, or hypotonic.
Colloids contain large proteins such as albumin as the solutes. These molecules remain intravascular, increased to osmolality and drawing fluid in.
Drawbacks to colloids?
Expensive, specific storage requirements, short shelf life
When you have to give large volumes of fluid, what is the best fluid to use?
LRs
Large volumes of NS can cause?
Hyperchloremic metabolic acidosis, hypernatremia
What fluid is administered with blood products?
NS
When is 1/2 NS a good choice?
Hypernatremic patients who do not need extra glucose. (diabetics)
D5W should not be used in what patients?
Diabetics
or
Hypokalemic (dextrose causes insulin release, insulin stimulates K absorption into cells.)
What is the most common postoperative fluid?
D5 1/2NS
D5NS is ____(hyper/hypo)tonic. Watch for _____ when giving it.
Hypertonic
Volume overload
Your patient is severely hyponatremic. What type of fluid are you going to give, how much?
3% saline in 50-100mL bolus up to 3 times to increase Na.
Then a slow IV infusion at 15-30mL/hour
A 50-100mL 3% saline bolus raises serum Na by how much?
2-3mEq
Is it very important to raise serum Na slowly to prevent?
Demyelination syndrome (central pontine myelinolysis)
Ideal urine output in an adequately hydrated patient?
30-50mL/hour
T/F? It is sufficient to start a patient on fluid replacement and check on them the next day.
False- you need to frequently monitor patient and adjust fluid accordingly.
