2 - Electrolytes and Fluids Flashcards
What factors regulate total body sodium?
Aldosterone
ANP
What factor alters [Na+]?
ADH
What is the difference between total body sodium and sodium concentration?
Total body sodium means that there is an increased amount of sodium located in the body. Usually this means there is also an increase in the amount of water in the body, so the sodium concentration does not change.
Sodium concentration refers to the ratio of sodium to water.
Aldosterone regulates the total number of sodium cells. ADH causes serum concentration by decreasing the amount of water, thereby increasing the Na concentration.
What regulates total body potassium?
Aldosterone
Intrinsic renal mechanisms
What regulates [K]?
Insulin
Epinephrine
What regulates total body Ca?
Vit D and PTH
What regulates [Ca]?
Vit D and PTH
How are Mag and Phos regulated?
Both total body and serum concentrations are regulated by intrinsic renal methods
with minimal input from PTH
the blood–brain barrier is poorly permeable to _______ but freely permeable to _______
Sodium
Water
How is serum osmolality determined?
2 x serum sodium + serum glucose + serum urea
A patient has a normal [Na] but an elevated serum osmolality. What is a likely explanation?
Increased glucose or BUN
What is the name of the vasopressin mediated water channel in the distal tubule?
Aquaporin 2
What can result from increasing serum Na too quickly?
Central Pontine Myelinolysis
How quickly should serum sodium be increased?
< 12 mEq/L/day
Carcinoid Syndrome
When a carcinoid tumore metastasizes to the liver and secretes its hormone into the portal vein and general circulation
What is the most common hormone carcinoids secrete?
Serotonin
Clinical manifestations of carcinoid syndrome
Flushing
Intestinal Motility (diarrhea)
R sided heart issues (TRegurg, pulm stenosis)
What are the components of TBW (Total Body Water)?
ICV (40% of total body weight)
ECV (20% total body weight)
What are the components of ECV (extracellular volume)?
Plasma (3L, 1/5 of of ECV)
Remainder is IFV (interstitial fluid volume)
Red cell volume contributes to ICV or ECV?
ICV!
Why is the brain so sensitive to changes in sodium?
The blood brain barrier is completely impermeable to sodium, so sodium levels directly influence fluid movement in and out of the cerebral circulation
Compare and contrast the effects of hypertonic saline and mannitol
Both cause a decrease in brain water
3% saline causes increased intravascular volume
mannitol causes diuresis, leading to decreased intravascular volume
Is mild hypovolemia associated with metabolic alkalosis or acidosis?
What about severe hypovolemia
Mild: alkalosis
Severe: Acidosis
How is sodium plasma concentration effected by glucose levels?
Glucose holds water within the extracellular space, cause dilutional hyponatremia
Why does serum hyponatremia with a normal serum os occur in renal failure?
Because BUN is distributed in the ECV and ICV
What is the cornerstone of SIADH treatment
Freewater restriction
Elimination of precipitating cause
What is the difference between cerebral salt wasting and SIADH?
in cerebral salt wasting, ADH secretion is normal and is treated with steroids
What is the difference between aldosterone and ADH?
Both cause water retention BUT
aldosterone does it by increasing sodium and decreasing potassium/Hydrogen (maintain electrical charge)
ADH does it by acting directly on aqauporins to retain water
What is normal intracellular K concentration
150
Acute _____ kalemia hyperpolarizes cell membrane
Hypokalemia, because the electrical gradient is suddenly widened between the intra and extra cellular spaces
This is why cardiac cells are more irritable, and why arteries have hypertension
Both metabolic and respiratory alkalosis lead to _____kalemia
hypokalemia
REMEMBER emia refers to the blood
hypokalemia means the amount of potassium in the blood, not the body
What are ECG changes associated with HYPOkalemia
flat or inverted T waves, prominent U waves, and ST segment depression
Ectopy
For a patient with DKA who has hypokalemia and is acidotic, when should potassium be repleted?
Before the correction of the acidosis
BECAUSE
Potassium is going to start moving back into cells and drop off precipitously once pH is controlled
what does insulin administration decrease potassium levels?
Activates the Na-K ATPase pump, moving K into the cell
Why do B adrenergics like albuterol help lower potassium?
Increases uptake of potassium in skeletal muscle cells
What is the ECV:ICV ratio of CA
10,000 to 1
Acidemia _____ Ca
Alkalosis _____ Ca
increases
decreases
What causes hypocalcemia?
Failed PTH or calcitriol
Calcium chelation or precipitation
What is the hallmark symptom of hypocalcemia?
increased neuronal membrane irritability and tetany
____ in Magnesium and _____ in phosphate lower calcium levels
Decrease, increase
What is the rule of 10’s for emergency calcium administration
10ml
of 10%
over 10 minutes
What is the effect of calcium on digitalis?
Makes it more toxic
Be careful giving calcium to patients who are on dig
Why is total serum calcium a poor indicator of calcium status if albumin is low?
A significant amount of circulating calcium is bound to albumin, but the not the functional calcium. So if your albumin is low it will decrease your total calcium content, but it doesn’t effect your ionized calcium
What causes hypercalcemia?
Bone resorption
what is the first line drug treatment for hypercalcemia
biphosphonates
What is the second line treatment for hypercalcemia
Calcitonin
Fast acting, but doesn’t work in about 25% of people
More effective if given with glucocorticoids
What is net filtration pressure?
The sum effect of all the intra and extra capillary pressures
Positive net filtration favors fluid _______
exudation into tissues
Negative net filtration favors ______
Fluid reabsorption into vasculature
Venous capillary net filtration is ______
Arterial capillary net filtration is ______
Negative
Positive
How does the glycocalyx regulate osmotic pressure?
Binds with circulating albumin!
What is the preferred fluid for patients at risk for cerebral edema?
NS, slightly hyperosmolar
Which patients should not get LR?
DKA (lactate breakdown in the liver produces glucose)
TBI (mildly hypotonic, can cause cerebral edema)
What are some of the benefits of plasmalyte?
Buffered (preserves physiologic pH)
Doesn’t contain calcium
Doesn’t use lactate as buffer
What disease process causes specific damage to the glycocalyx?
hyperglycemia
What do DO2 and VO2 represent?
Oxygen delivery
Oxygen consumption
What is primary hemostasis?
Platelets adhere to sites of endothelial disruption, undergo activation to recruit more platelets and amplify the platelet response, and then cross-link with fibrin, the end product of the plasma clotting factor cascade, to form a platelet plug.
What happens when the endothelial lining (glycocalyx) is disrupted?
Platelets adhere to the collagen in the broken matrix
Does anemia increase or decrease platelet function?
decreases
How much should hemoglobin and Hct increase for each unit of PRBCs?
1 g/dl
3%
What types of patients benefit from maintaining platelet count > 50?
Eye surgeries, polytrauma
What is alloimmunization?
Exposure to a foreign antigen, initial exposure doesn’t prompt a reaction but the second does
Rh and second pregnancy
Multiple blood transfusions, especially platelets
What is the leading cause of transfusion associated mortality?
TRALI
What is Post Transfusion Purpura?
Rare, severe thrombocytopenia after transfusion
Almost always in previously pregnant women
Destroys platelets
IVIG is first line of defense
What is the most common hereditary bleeding disorder?
vWD (von Willenbrand)
vWD is an disorder of _______ hemostasis
Primary
How is hemophilia inherited?
X linked, almost entirely affects males
Hemophilia A is a defect in which clotting factor?
VIII (8)
List two forms of hereditary hypercoagulopathy
- FVL mutation
- Protein C and S deficiencies
Both act on factor V
What are the leading causes of Vit K deficiency
Liver insufficiency
Sterile gut in newborns
ABX treatment
How is Vit K synthesized?
Bacteria in the gut
Bile salts in the liver
Which coagulation factors are produced by the liver
2
5
7
9
10
11
Is a PT or aPTT acute in chronic renal failure?
NO
DIC is consumptive _____ and ______
coagulopathy and thrombocytopenia
What is the treatment for coagulopathy in DIC?
For thrombocytopenia?
Plasma
Platelets
GP IIb/IIIa receptor blockers
epciximab
tirofibin, eptifibitide
inhibit the cross linkage of fibrin
Vitamin K Antagonists
Warfarin
inhibit synthesis of Vit K dependent factors
ADP Receptor Antagonists
prevent the expression of GP IIb/IIIa on the surface of activated platelets, thereby inhibiting platelet adhesion and aggregation
clopidogrel, ticagrelor
Cyclooxygenase Inhibitors
Apirin and NSAIDs
What is the role of COX-1?
plays an integral part in maintaining the integrity of the gastric lining, renal blood flow, and initiating the formation of TxA2, an important molecule for platelet aggregation.
what are the key characteristics of HIT?
Thrombocytopenia, but increased coaguability
What is the treatment for HIT?
D/C Heparin
Start thrombophylaxis
Exclude thrombosis
DON’T GIVE PLATELETS
Parenteral Direct Thrombin Inhibitors
Argatroban, Bivalirudin
rFVIIIa
Recombinant factor 8a
Designed for hemophiliacs, but used in postpartum hemorrhage, trauma, reversal of various anticoagulants, and high-risk cardiac surgery.
Why is DDAVP used in bleeding disorders?
improves hemostasis and platelet function
Antifibrinolytics
TXA
derivatives of lysine
competitively inhibit the binding site on plasminogen, preventing cleavage to plasmin and the resultant fibrinolysis
What blood type is a universal recipient? Why?
AB
Have A and B antigens
Do not have A or B antibodies
What blood type is universal donor? Why?
Do no have antigens
Have anti-bodies to A and B
Why does distal renal tubular acidosis hypokalemia?
Major water/sodium loss is caused by dRTA, so aldosterone is synthesized and decreases K levels
If sodium is low and the serum os is high or normal, what does that mean?
Some other substance (mannitol, glucose, BUN, ethanol etc.) is in the PV pulling water into the capillaries. Total body sodium is normal, but the capillaries are overfilled so the low Na is dilutional
If sodium is low and serum osmolality is low, what should you check next?
Urine osmolality and urine sodium
What are the top two diseases associated with SIADH?
Small cell lung CA
Brain problems
How does plasma [Na+] related to total body sodium?
It doesn’t!
Sodium concentration measures fluid status, not the amount of sodium in the body
What is the most common cause of hyperkalemia?
Drugs!
NSAIDS, ACE inhibitors, cyclosporines
Which two types of acidosis cause shifts in K?
Which two do not?
Respiratory and Mineral Metabolic Acidosis
Organic metabolic acidosis (lactic acidosis, ketoacidosis)
What are three methods for shifting K intracellularly?
glucose and insulin
bicarb
Albuterol (B2 agonists)
If phosphate is high, Ca is _____
Low
Magnesium is an endogenous _______ and stabilizes _______
calcium antagonist
axonal membranes
Competes with Ca for binding sites in pres-synaptic terminals, meaning it requires more Ca to cause depolarization
Hypomagnesemia is characterized by:
increased neuronal excitability, muscle irritability and tetany
Of all the isotonic crystalloids, NS is the least ______.
Why?
Physiologic.
Contains proportionally more Cl
What is the primary role of NS in anesthesia?
given in small volumes for neuro patients
NS is the preferred fluid for which patient?
those at risk for cerebral edema
Why is NS sometimes the only option for patients in ESRD?
They can’t tolerate the K level of other isotonics
When is LR contraindicated?
Why?
TBI
Neurovascular insults
Slightly hypo-osmolar
A patient with a BG of 220 should probably not receive _______
Colloids
Hyperglycemia is known to injure the endothelial glycocalyx
