Acute & Critical Care Medicine Flashcards
What are IV fluids used for?
IV fluids are used to replace fluid losses and treat various conditions
What are the two categories of IV fluids?
Crystalloids or colloids
What are crystalloids?
Crystalloids contain various concentrations of sodium and/or dextrose that pass freely between semipermeable membranes
*Most of the administered volume does not remain in the intravascular space (inside the blood vessels) but moves into the extravascular space or interstitial space
What are some benefits of using crystalloids?
- Crystalloids are less costly and generally have fewer adverse reactions than colloids
- Some data suggest that balanced solutions may be preferred in certain disease states like sepsis, as the chloride load from sodium chloride can be high enough to contribute to cell injury, including renal damage in ICU patients
What are colloids?
Colloids are large molecules (typically protein or starch) dispersed in solutions that primarily remain in the intravascular space and increase oncotic pressure
What is a benefit of colloids?
Colloids provide greater intravascular volume expansion than equal volumes of crystalloids
What is the downside of colloids?
Colloids are more expensive and have not shown clear clinical benefit over crystalloids
What are some examples of crystalloids?
5% dextrose (D5W), 0.9% NaCl (normal saline), Lactated Ringer’s (LR), Multiple electrolyte injection
What are some examples of colloids?
Albumin 5%, 25%, Dextran, Hydroxyethyl starch
When are dextrose-containing products used?
When water is needed intracellularly, as these products contain “free water”
What are Lactated Ringer’s and normal saline used for?
Lactated Ringer’s and normal saline are the most common fluids used for volume resuscitation in shock states
When is albumin most useful?
Albumin is the most commonly used colloid and is particularly useful when there is significant edema
When should albumin not be used?
Albumin should not be used for nutritional supplementation when serum albumin is low
What is the boxed warning with hydroxyethyl starch?
Hydroxyethyl starch use is limited secondary to its boxed warning to avoid use in critical illness (including sepsis) due to mortality and renal injury
What is the definition of hyponatremia?
Na < 135 mEq/L
When are patients typically symptomatic from hyponatremia?
It is usually not symptomatic until the sodium is < 120 mEq/L, unless the serum level falls rapidly
What are the causes of hypotonic hypovolemic hyponatremia?
Hypotonic hypovolemic hyponatremia can be caused by diuretics, salt-wasting syndromes, adrenal insufficiency, blood loss or vomiting/diarrhea
What is the treatment to correct hypotonic hypovolemic hyponatremia?
Administer sodium chloride IV solutions
What is the cause of hypotonic hypervolemic hyponatremia?
Fluid overload (e.g. cirrhosis, heart failure or renal failure)
What is the preferred treatment of hypotonic hypervolemic hyponatremia?
Diuresis with fluid restriction is the preferred treatment
What is the cause of hypotonic isovolemic (euvolemic) hyponatremia?
Hypotonic isovolemic hyponatremia can be caused by the syndrome of inappropriate antidiuretic hormone (SIADH)
What is the treatment of hypotonic isovolemic hyponatremia?
Treatment includes stopping drugs that can induce SIADH, diuresis or restricting fluids
*Demeclocycline can be used off-label for SIADH
What can happen if you rapidly correct sodium?
Correcting sodium more rapidly than 12 mEq/L over 24 hours can cause osmotic demyelination syndrome or central pontine myelinolysis, which can cause paralysis, seizures and death
What is the role of desmopressin in correcting sodium?
Administration of desmopressin reduces water diuresis and can help avoid overcorrection
What can be used to treat SIAH and hypervolemic hyponatremia?
The arginine vasopressin (AVP) receptor antagonists (conivaptan and tolvaptan) may be used to treat SIADH and hypervolemic hyponatremia
How does AVP receptor antagonists work?
They increase excretion of free water while maintaining sodium
What is the downside of AVP receptor antagonists?
The role of these drugs is still being determined, as they are more expensive than 3% saline and use beyond 30 days with the oral product, tolvaptan, is not recommended
What are examples of arginine vasopressin receptor antagonists?
Conivaptan, Tolvaptan
What is a contraindication of conivaptan?
Hypovolemic hyponatremia, concurrent use with strong CYP3A4 inhibitors, anuria
What is a warning with conivaptan?
Overly rapid correction of hyponatremia is associated with ODS
What are some side effects of conivaptan?
Orthostatic hypotension, fever, hypokalemia, infusion site reactions (>60%)
What do you need to monitor when using conivaptan?
Rate of Na increase, BP, volume status, urine output
What are the boxed warnings of Tolvaptan?
- Should be initiated and re-initiated in a hospital under close monitoring of serum Na
- Overly rapid correction of hyponatremia is associated with ODS (consider slower correction with severe malnutrition, alcoholism or advanced liver disease
What are some contraindications to tolvaptan?
Patients who are unable to sense or respond appropriately to thirst, urgent need to raise Na, hypovolemic hyponatremia, use with strong CYP3A4 inhibitors, anuria
What is a warning associated with Tolvaptan?
Hepatotoxicity (avoid use > 30 days and in liver disease/cirrhosis)
What are some side effects of Tolvaptan?
Thirst, nausea, dry mouth, polyuria, weakness, hyperglycemia, hypernatremia
What are some monitoring parameters of Tolvaptan?
Rate of Na increase, BP, volume status, urine output, signs of drug-induced hepatotoxicity
What is hypernatremia?
Hypernatremia (Na > 145 mEq/L) is associated with a water deficit and hypertonicity
What is hypovolemic hypernatremia caused by?
Dehydration, vomiting, or diarrhea
How do you treat hypovolemic hypernatremia?
Fluids
What are the causes of hypervolemic hypernatremia?
Intake of hypertonic fluids
How is hypervolemic hypernatremia treated?
Diuresis
What is the cause of isovolemic (euvolemic) hypernatremia?
Diabetes insipidus which can decrease antidiuretic hormone
How is isovolemic hypernatremia treated?
With desmopressin
What is a common cause of hyperkalemia?
Chronic kidney disease
What is hypokalemia?
Hypokalemia, or K < 3.5 mEq/L, is a common occurrence in hospitalized patients
What is the general management of hypokalemia?
Management includes treating the underlying causes (metabolic alkalosis, overdiuresis and some medications such as amphotericin and insulin) and administering oral or IV potassium
What is the general rule of thumb in potassium deficit?
A drop of 1 mEq/L in serum K below 3.5 mEq/L represents a total body deficit of 100-400 meQ
What is generally used for potassium replacement?
Potassium chloride premixed IVs are generally used for IV replacement
What are the safe recommendations for IV potassium replacement through a peripheral line?
Safe recommendations for IV potassium replacement through a peripheral line include a maximum infusion rate < 10 mEq/hr and a maximum concentration of 10 mEq/100 mL
When are rapid infusions and higher concentrations of potassium warranted?
In severe or symptomatic hypokalemia
*these require a central line and cardiac monitoring
When can IV potassium be fatal?
If administered undiluted or IV push
What should be checked if hypokalemia is resistant to treatment and why?
Serum Mg should be checked becuase magnesium is necessary for potassium uptake so hypomagnesemia can worsen or prevent correction of hypokalemia
What should be replaced first when hypokalemia and hypomagnesemia are present?
Magnesium
What is hypomagnesemia?
Mg < 1.3 mEq/L
What are common causes of hypomagnesemia?
Chronic alcohol use, diuretics, vomiting and diarrhea
What is the most common cause of hypermagnesemia?
Renal insufficiency
When is IV replacement of magnesium recommended?
When serum Mg is <1 mEq/L with life-threatening symptoms (e.g. seizure, arrhythmias), IV replacement is recommended
What is used for IV replacement of magnesium?
Magnesium sulfate
What is recommended when serum Mg < 1 mEq/L without life-threatening symtpoms?
Therapy can be administered IV or IM
What is recommended when serum Mg is > 1 mEq/L and <1.5 mEq/L?
Magnesium is replaced orally, most commonly with magnesium oxide
How long should magnesium replacement regimens be?
Magnesium replacement regimens should continue for 5 days to fully replace body stores
What is a common cause of hypophosphatemia?
Chronic kidney disease
What is hypophosphatemia?
Hypophosphatemia is considered severe and is usually symptomatic when serum phosphate (PO4) is usually < 1 mg/dL
What are some symptoms of hypophosphatemia?
Symptoms can include muscle weakness and respiratory failure
What are some causes of hypophosphatemia?
Hypophosphatemia can be caused by phosphate-binding drugs (calcium, sevelamer, antacids), chronic alcohol intake and hyperparathyroidism
What is recommended when serum PO4 is < 1 mg/dL?
When serum PO4 is < 1 mg/dL, IV phosphorus is used for replacement
What is a common regimen for phosphorus replacement?
0.08-0.16 mmol/kg in 500 mL of NS or D5W over 6 hours
How long does full replacement of severe hypophosphatemia take?
Full replacement often takes one week or longer
What is intravenous immune globulin?
Intravenous immune globulin (IVIG or IGIV) contains pooled immunoglobulin (IgG) that is administered intravenously
How is IgG extracted?
IgG is extracted from the plasma of a thousand or more blood donors
*typically the IVIG is derived from between 3000-10000 donors
What is IVIG used for?
IVIG is given as plasma protein replacement therapy for immune-deficient patients who have decreased or abolished antibody production capabilities
What are some indications of IVIG?
- immunodeficiency conditions
- off label: multiple sclerosis, myasthenia gravis, Guillain-Barre syndrome
What can IVIG impair the response to?
Vaccines
What is the boxed warning of IVIG?
- Acute renal dysfunction can occur (rare) and has been associated with fatalities; it usually occurs within 7 days (more likely with products stabilized with sucrose)
- Use caution in the elderly, renal disease, diabetes, volume depletion, sepsis, paraproteinemia and those taking nephrotoxic medications
- Thrombosis can occur even without risk factors (for patients at risk, administer the minimum dose)
What are contraindications of IVIG?
IgA deficiency (can use product with lowest amount of IgA)
What is a warning about use of IVIG?
Use with caution in CV disease (use isotonic products and low infusion rate)
What are some side effects associated with IVIG?
Headache, nausea, diarrhea, injection site reaction, infusion reaction (facial flushing, chest tightness, fever, chills, hypotension) - slow/stop infusion, renal failure or blood dycrasias (both rare)
What are some monitoring parameters of IVIG?
Renal function, urine output, volume status, Hgb
What are some counseling points of IVIG?
- Patients that should be asked about past IVIG infusions, including product used and any reactions that occurred; slow titration and premedication may be used
- Lot numbers of administered IVIG products must be tracked (it is a blood product)
What is APACHE II and what is it used for?
The Acute Physiologic Assessment and Chronic Health Evaluation II is a scoring tool used to determine prognosis and estimate ICU mortality risk
How do vasopressors work?
Most vasopressors work by stimulating alpha receptors, which causes vasoconstriction and increases systemic vascular resistance which increases BP
What are some examples of vasopressors?
Dopamine, Epinephrine, Norepinephrine, Phenylephrine, Vasopressin
How does phenylephrine work?
Phenylephrine is a pure alpha-agonist that increases SVR without increasing HR
How does epinephrine and norepinephrine work?
Epinephrine and norepinephrine are mixed alpha- and beta- agonists, causing both an increase in SVR as well as an increase in CO and HR
When would you use dopamine?
Dopamine is a natural precursor of norepinephrine and is recommended for use in symptomatic bradycardia
How does vasopressin work?
Vasopressin acts directly on vasopressin receptors
How does Angiotensin II work?
Angiotensin II, approved for septic and distributive shock, raises blood pressure by vasoconstriction and aldosterone release, which results in sodium and water retention
What is a boxed warning of dopamine and norepinephrine?
Dopamine and norepinephrine have a boxed warning regarding extravasation; all vesicants when administered IV; treat extravasation with phentolamine
What are some warnings associated with dopamine, epinephrine and norepinephrine?
Use extreme caution in patients taking an MAO inhibitor; prolonged hypertension may result
What are some side effects of vasopressors?
Arrhythmias, tachycardia (especially dopamine, epinephrine), necrosis (gangrene), bradycardia (phenylephrine), hyperglycemia (epinephrine), tachyphylaxis, peripheral and gut ischemia
What are monitoring parameters for vasopressors?
Continuous BP monitoring (with continuous infusions), HR, mean arterial pressure (MAP), ECG, urine output, infusion site for extravasation
What are some important counseling points about vasopressors?
- Solutions should not be used if they are discolored or contain a precipitate
- All vasopressors are Y-site compatible with each other except angiotensin II
- Some institutions use non-weight based infusions (mcg/min) instead of weight-based infusions (mcg/kg/min)
- All vasopressors should be administered via central IV line
- No clear evidence that low dose dopamine (renal dosing) provides benefit
- Epinephrine used for IV push is 0.1 mg/mL (1:10,000 ratio strength); epinephrine used for IM injection or compounding IV products is 1 mg/mL (1:1,000 ratio strength); ratio strength has been removed from labeling per the FDA
What can vesicants cause?
Vesicants can cause severe tissue damage/necrosis with extravasation
What is extravasation?
Leakage of drug from the blood vessel into the surrounding tissue (medical emergency)
How do you reduce the risk of extravasation?
To reduce the risk, every attempt should be made to infuse vasopressors through a central line
How do you treat vasopressor extravasation?
Treat extravasation with phentolamine, an alpha-1 blocker that antagonizes the effects of the vasopressor