Fluids , Electrolytes, and Acid-Base Flashcards
What fraction of body water is found in extracellular space?
20% and 14 Liters
Major ions = Sodium, Chloride, Ca+, and Bicarb
70kg adult has how many Liters of body water? Volume is what percent of weight?
42L and 60% of body weight
Intracellular Volume
40% of total body weight
28L
Major ions = Potassium, Magnesium, and Phosphate
ECV can be further divided into?
Interstitial fluid and plasma
-Interstitial fluid = 16% TBW or 11 L
-Plasma = 4% TBW or 3L
can be (15% and 5%)
What population has the highest TBW of water?
Neonates 80%
What population has the lowest TBW of water?
Females, the obese, and the elderly
What determines the net movement of fluid between the intravascular space and interstitial spaces?
Starling forces and Glycocalyx
Forces that move fluid from CAPILLARY to INTERSTITIAL SPACE
Pc= Capillary hydrostatic pressure (PUSHES fluid out of capillary)
^ if = Interstitial oncotic pressure (PULLS fluid out of capillary)
Forces that move fluid from INTERSTITIAL space into CAPILLARY
P if= Interstitial hydrostatic pressure (pushes fluid into capillary)
^ c= Capillary oncotic pressure (pulls fluid into capillary)
What is the pressure of a solution against a semipermeable membrane that prevents water from diffusing across that membrane?
Osmotic pressure
Which solutes cannot diffuse across semipermeable membrane?
ions, protiens, glucose
carrier proteins transport these solutes from one side to the other
Equation to calculate Plasma Osmolarity
(Na+ x 2) + (Glucose / 18) + BUN / 2.8)
Normal = 280- 290 (high is hyper and low is hypo)
What is the most important determinant of plasma osmolarity?
Sodium
Conditions that increase osmolarity include…..
hypernatremia, hyperglycemia, and uremia
What does giving a hypotonic solution do to ECF, ICF and plasma osmolarity?
Increase ECF and ICF volumes
Decreases plasma osmolarity
What fluid should you never give a patient with increase ICP?
HYPOTONIC!!!
poor expanders of intravascular volume
What does giving isotonic solution do to ECF, ICF, and plasma osmolarity?
Increase ECF
ICF and plasma osmolarity stay the same!
How long do Crystalloids stay in the intravascular space for?
30 minutes
What can cause hypercholemic metabolic acidosis? What is given instead for large-volume resuscitation?
NaCl can cause it
LR is used (the lactate functions as a buffer because the lactate is converted to bicarb by the liver and kidneys)
What fluids are given to dilute PRBCs?
NS and Plasmalyte
LR contains calcium which is why it is avoided. (book answer)
What organ is the most important regulator of potassium homeostasis?
Kidneys (decreased GFR/renal failure increases serum potassium)
Causes of Hypokalemia (< 3.5 mEq/L)
poor intake, GI loss, renal loss, or redistribution (K+ shifts IN to cells)
Causes of Hyperkalemia ( > 5.5 mEq/L)
Increased total body potassium and redistribution (K+ shift OUT of cells)
What is responsible for maintaining the intracellular distribution of potassium?
the Na+K+ATPase pump
Hyperkalemia does what to membranes?
Hypokalemia?
Hyperkalemia DEpolarizes membranes
Hypokalemia HYPERpolarizes membranes
HYPOkalemia symptoms
skeletal muscle cramps —> weakness —-> paralysis
Worsens Digoxin toxicity
HYPERkalemia symptoms
Cardiac rhythm distrubances
EKG findings of HYPOkalemia
LONG–> PR interval
LONG–> QT interval
FLAT–> T wave
U wave
EKG findings of HYPERkalemia
5.5 - 6.5 = Peaked T waves
6.5 - 7.5 = P wave flattened
7.0- 8.0 = QRS prolongation
8.5 or greater = VF or sine wave
Most common electrolyte disorder in clinical practice?
HYPOkalemia
How fast to administer IV K+ ?
Peripheral = 10mEq per hour
Central = 20mEq per hour
Treating HYPOnatremia too quickly causes what?
Fluid to shift from ICF to ECF too quickly which can produce pontine myelinolysis
Treating HYPERnatremia too quickly causes what?
Fluid shifts from ECF to ICF which produces cerebral EDEMA
Rate to correct insensible fluid loss
2ml/kg/hr of crystalloid
Administering a large volume of albumin can lead to __________.
HYPOcalcemia
Acidosis _______ ionized calcium
INCREASES
Parathyroid _________ serum calcium and calcitonin __________ serum calcium.
Raises, Lowers
Which phase in the cardiac muscle cell action potential does Ca+ play a crucial role?
Phase 2
Normal plasma calcium (total)
8.5-10.5 md/dL or 4.5- 5.5 mEq/L
Normal ionized calcium level
4.65 - 5.28 mg/dL or 2.2 - 2.6 mEq/L
Primary treatment for magnesium toxicity?
CALCIUM! it antagonizes the effects of magnesium at the NMJ
What is the most abundant electrolyte in the body?
CALCIUM (nearly all stored in bone)
Calcium is factor 4 in coagulation pathway
Acidosis________ ionized calcium (albumin binds H+ and displaces Ca++ into plasma)
INCREASES
Alkalosis_______ ionized calcium. (albumin binds Ca++ and displaces H+ into the plasma)
DECREASES
Hypocalcemia EKG findings
LONG QT interval
Hypercalemia EKG findings
SHORT QT interval
Hypercalcemia Tx?
Hypocalcemia Tx?
Hyper= 0.9 NS and Loop diuretic
Hypo= calcium and vitamin D
Magnesium _________ the effects of calcium.
antagonizes
Tx for Pre-eclampsia
4g load IV over 10-15 minutes then 1g/hr for 24 hours.
Mag crosses the placenta
The Henderson-Hasselbalch equation details what?
How PaCO2 and HCO3- influence pH
Acidosis effects (P50, SNS, CBF, ICP, K+, SNS tone)
Increase P50 (right = release)
Increase SNS tone
Increase risk of dysrhythmias
decrease contractility
increase CBF and ICP
HYPERKALEMIA
Alkalosis effects (P50, SNS, CBF, ICP, K+, SNS tone)
Decrease P50 (left = love)
decrease coronary blood flow
increase dyshrythmias
decrease CBF and ICP
HYPOKALEMIA
decreased ionized calcium
How does hypercarbia effect the lungs compared to the peripheral circulation?
in the lungs CO2 is a direct-acting vasoconstrictor where it can cause pulmonary HTN and increased RV workload (dilates periphery)
Most common cause of Respiratory Acidosis?
Hypoventilation
What happens when alveolar ventilation exceeds CO2 production?
Respiratory alkalosis
Most common cause of Respiratory Alkalosis?
Iatrogenic —> Mechanical Ventilation
also pain, anxiety, pregnancy, PE
How does the body compensate for Respiratory Alkalosis?
Kidenys excrete Bicarb to return pH to normal
takes a few days
Increased anion gap determines acidosis from what?
DKA, salicylates, and cyanide poisoning
Normal anion gap determines acidosis from what?
Diarrhea, pancreatic fistula, NaCl solutions for resuscitation
Causes of Metabolic Acidosis
accumulation of nonvolatile acids, loss of bicarb, or large volume resuscitation with NS
Causes of Metabolic Alkalosis
increased bicarb, loss of acids (NG suction), increased mineralocorticoid activity (Cushing’s syndrome)
