Exam 1 Flashcards
process when water is driven by osmotic gradients through a semipermeable membrane separating solutions with different solute concentration
osmosis
TBW in water:
Male % and Liters
Female % and Liters
Infant %
Male 60% and 42L
Female 50% and 39L
Infant 75%
% of total body weight of the following fluid compartments:
TBW
ECF
ICF
RBC in Liters of H2O?
% of ECF that is:
ISF
Plasma
TBW 60%
ECF 20%
ICF 40%
RBC= ~1.5L of H2O
ISF = 75% of ECF Plasma = 25% ECF
Approx total blood volume in an adult male in liters
~5L - Plasma (3.5L) + RBCs (1.5L)
2 fluid types in the ECF (related to movement)
functional and sequestered
osmosis is a passive process driven by differences in particle _______, not size.
numbers
pressure gradient created by solute molecules that displace water
osmotic pressure
molecules move through a semipermeable membrane from an area of higher concentration to an area of lower concentration
diffusion
movement of molecules against their electrochemical gradient in a process that requires energy. [e.g. Na+/K+ATPase]
Active Transport
the force (mmHg) generated by the pressure of fluid within or outside of a capillary on the capillary wall
Hydrostatic Pressure
osmotic pressure (mmHg) exerted by proteins in the blood plasma or interstitial fluid
Colloid Osmotic Pressure (Oncotic Pressure)
number of osmotically active particles per liter of solvent; mOsm/L
Osmolarity
number of osmotically active particles per kilogram of solvent (water); mOsm/kg
Osmolality
Plasma Osmolality formula
2[serum Na+] + [Glucose]/18 + [BUN]/2.8
Normal = 280-290 mOsm/kg
Osmolal Gap: measured osmolality >10 mOsm/kg H2O than calculated
in a fluid compartment, the sum of all positive ions (cations) exactly equals the sum of all negative ions (anions)
Law of Electrical Neutrality
intracellular and intravascular concentration of electrolyte in mEq/L Na+ K+ Ca++ Ma+ Cl-
ion - ICC, IVC Na+ = 10, 134-145 K+ = 156, 3.5-5 Ca++ = 3, 5 Ma++ = 26, 3 Cl- = 2, 103
what ion contributes the greatest to determining osmolality?
Na+
Physiologically, ______ and _____ are the primary determinants of tonicity
sodium, potassium
Isotonic solutions
BSS; Normosol™-R or Plasma-Lyte
Hypertonic solutions
0.9% NaCl is slightly hypertonic; 3% NaCl or 20% mannitol is very hypertonic
Hypotonic solutions
Lactated Ringer’s (LR) slightly hypotonic; 0.45% NaCl and D5W are hypotonic
ICF has high concentrations of which ions?
Potassium (K+): 156 mEq/kg H2O
Magnesium (Mg2+): 26 mEq/kg H2O
Phosphate (P04-): 108 mEq/kg H2O
Proteins 55 mEq/kg H2O
*notice this mEq/kg and relates to osmolality
ICF has low concentrations of which ions?
Sodium (Na+): 10 mEq/kg H2O
Chloride (Cl-): 2 mEq/kg H2O
Calcium (Ca2+): 3 mEq/kg H2O
*notice this mEq/kg and relates to osmolality
ECF has high concentrations of which ions?
Sodium (Na+): 136 - 145 mEq/L
Chloride (Cl-): ~110 mEq/L
Calcium (Ca2+): ~4 mEq/L
*notice this mEq/L and relates to osmolarity
ECF has low concentrations of which ions?
Potassium (K+): 4 mEq/L
*notice this mEq/L and relates to osmolarity
interstitial fluid is separated from intracellular by the _______ _______.
plasma membrane
the interstitial component of the ECF is separated from the vascular component by the _______ ________.
capillary endothelium
blood volume in liters,
2 components and percentages
Blood volume ~ 5 liters
60% of blood is plasma
40% of blood is red blood cells
smallest but most vital of the 3 fluid compartments?
plasma
Interstitial fluid is a complex mixture of what fluids?
Ultrafiltrated plasma (Intravascular water) Transudated Plasma Transcellular Fluids (fluid and electrolytes actively pumped out of cells)
what are the four starling forces that govern the movement of fluid at the capillary level?
hydrostatic pressure in the capillary (Pc)
hydrostatic pressure in the interstitium (Pi)
oncotic pressure in the capillary (pc )
oncotic pressure in the interstitium (pi )
how does fluid that is filtered into the interstitial space make its way back into the vasculature?
via the lymphatic drainage system
water balance is mediated by what three mechanisms?
osmolality sensors in the anterior hypothalamus
baroreceptors in the left atrium, carotid arteries and aortic arch
the juxtaglomerular apparatus (RAAS)
vasopressin is produced in the ____ and released by the ____.
produce in the hypothalamus and released by the posterior pituitary
the most abundant ecf ion….
sodium
primary site of Na+ regulation
kidney via changes in rate of glomerular filtration & tubular resorption
Your patient is hyperglycemic with a blood sugar of 400 and must go to surgery. Due to their hyperosmolar state they have developed a seemingly dilutional hyponatremia. How can you determine an approximate actual sodium level for this patient?
For every 100 mg/dL of glucose above 100, add 1.6 mEq/L to the measure sodium
four general categories of hyponatremia
Pseudohyponatremia
Hypovolemic Hyponatremia
Hypervolemic Hyponatremia
Euvolemic Hyponatremia
examples of pseudohyponatremia
False low PNa+; normal osmolality; presence of other osmolar particles in the serum that don’t contribute to plasma osmolality
Severe hyperlipidemia or hyperproteinemia, blood draw error
examples of hypovolemic hyponatremia
Decreased ECF volume combined with an even greater loss of Na+
Body fluid losses: Sweating, vomiting, diarrhea, GI suction, “third spacing”
Renal causes: Diuretic use, CHF, mineralocorticoid deficiency, renal tubular acidosis, and salt wasting nephropathy or cirrhosis
examples of hypervolemic hyponatremia
Na+ and H2O are retained, but H2O retention exceeds Na+ retention
Heart failure, chronic renal failure, and hepatic failure
Edema; fluid retention is due to renal hypoperfusion and resulting aldosterone secretion
examples of euvolemic hyponatremia
Euvolemic but have increased TBW
Causes: Syndrome of inappropriate antidiuretic hormone secretion (SIADH), psychogenic polydipsia, hypothyroidism, mild CHF with diuretic use, water intoxication, and MDMA use
three most common causes of SIADH
pulmonary lung masses, CNS disorders, and medication
Acute hyponatremia time, treatment and target rise metrics
Acute = less than 48 hours
may be corrected rapidly, but ONLY if neurologically impaired
Treatment = 150 ml of hypertonic (3%) NaCl PIV over 20 min.; furosemide to increase renal excretion of free H2O
Target rise in PNa+ by 4-6 mEq/L within the first 4–6 hours; should not exceed 8 mEq/24°
Chronic hyponatremia time, treatment considerations and target rise metrics
Chronic = > 48 hrs
Slow correction unless seizures or coma
Treatment = 150 ml of hypertonic (3%) NaCl PIV over 20 min.; furosemide to increase renal excretion of free H2O
Correction should not exceed 12 mEq/L over 24 hours
what patients are most at risk for osmotic demyelinating syndrome?
hyponatremic, hypokalemic, malnourished patients such as chronic alcoholics
TURP syndrome cause, risk factors, S&S and treatment
Transurethral Resection of the Prostate (TURP) Syndrome
For benign prostatic hyperplasia; cystoscopic approach
Surgeon uses Isotonic, non-electrolyte fluid with glycine or sorbitol with mannitol to continuously irrigate the bladder.
When this irrigant makes its way into the vascular space via the resected vascular tissue of the prostate it can cause a hypo-osmolar plasma state
Risk factors: prolonged (>1 hour) surgical time, irrigating bag > 40 cm above the operative field, use of hypotonic irrigation fluid, bladder pressure >15 cm H2O
S&S: Cardiopulmonary, neurologic, hematologic, renal, metabolic (Table 21.4)
Treatment: Stop surgery, loop diuretic, support CVS, treat low PNa+ if severe
What is the formula for replacing water deficits in patients with hypovolemic hypernatremia?
Water deficit = (o.6 x total body weight in kg) x (sodium concentration/140 −1)
what is the major intracellular cation?
K+
What 2 factors affect how the kidneys regulate potassium?
renal tubular fluid and aldosterone
potassium balance is primarily governed by what mechanism?
urinary loss
4 Major roles of potassium in the body?
Generation of the resting cell membrane potential and the action potential
Protein synthesis
Acid–base balance
Maintenance of intracellular osmolality
what is aldosterone’s action on sodium and potassium?
aldosterone leads to the retention of sodium and the excretion of potassium.
Hypokalemia most common causes
Serum [K+] < 3.5 mmol/L
Usually iatrogenic; most common electrolyte disorder in patients; most are asymptomatic
Causes: (1) Increased renal loss; (2) Increased G.I. loss; (3) Transcellular shift
2 most common causes hypokalemia due to transcellular potassium shift
respiratory alkalosis and beta agonists
what other electrolyte abnormality is commonly seen in patients with hypokalemia?
hypomagnesemia
hypokalemia is often asymptomatic but when they do arise they will likely be of ______ and _____ in origin.
cardiac, neuromuscular
EKG changes in hypokalemia
T-wave flattening ST depression U waves QT interval prolongation, ventricular dysrhythmias and cardiac arrest
Hypokalemia treatment
Treatment
1 mEq/L serum reduction = 200 mEq total body loss
Potassium chloride 40 to 60 mEq PO q 2 to 4 hours is well tolerated
Intravenous: 10 to 20 mEq/hr; max 0.5 to 0.7 mEq/kg/h
Hyperkalemia common causes and levels
Serum [K+] > 5.5 mmol/L (Mild: 5.5 – 6.0; Moderate: 6.1 – 6.9; Severe: > 7.0)
Common causes :
Pseudohyperkalemia: Hemolysis due to drawing or storing of the laboratory sample or post–blood sampling leak from markedly elevated white blood cells, red blood cells, or platelets
Renal failure: Acute or chronic
Kidneys account for ~90% of K+ excretion; serum K+ begins to rise only when renal function falls to < 25% of normal
Acidosis: Diabetic ketoacidosis (DKA), Addison’s disease (adrenal insufficiency), renal tubular acidosis
Cell death: Rhabdomyolysis, tumor lysis syndrome, massive hemolysis or transfusion, crush injury, burn
Drugs: Beta-blockers, acute digitalis overdose, succinylcholine, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs (NSAIDs), spironolactone, amiloride, potassium supplementation
Hyperkalemia S&S
Chronic: often asymptomatic
Moderate to severe hyperkalemia: nausea, vomiting, and diarrhea
Severe may present with neuromuscular findings like muscle cramps, generalized weakness, paresthesias, tetany, and focal or global paralysis – not sensitive or specific findings.
MOST IMPORTANT consequence of hyperkalemia
The reduction is myocardial membrane resting potential leading to progressive ECG abnormalities
Tumor lysis syndrome, which can cause increased potassium levels, can be induced by the administration of which common anesthesia medication?
dexamethasone
First and most common change on the ECG in the setting of hyperkalemia
symmetrical peaking of the T wave
3 mainstays of treatment for hyperkalemia in rank order
- stabilization of cardiac membrane
- shifting potassium back into cells
- eventually removing potassium from the body
in hyperkalmia, administration of what other electrolyte will help to stabilize the cardiac membrane?
calcium (chloride or gluconate) IV push, which will restore the electrical gradient at the cardiac
membrane.
calcium chloride is most effective
what is the most reliable agent for shifting potassium into the cells in the setting of hyperkalemia?
insulin, give with glucose to prevent hypoglycemia. stimulates sodium potassium ATPase
Most abundant electrolyte in the human body
calcium
2 primary forms of circulating calcium
Free ionized fraction in ECF (60%); this is the physiologically active form! [1.12 to 1.32 mmol/L]
Protein bound (mostly albumin) (40%); pH dependent alkalosis ↑ binding, acidosis ↓ binding
3 hormones involved in the regulation of calcium
Parathyroid Hormone
Calcitonin
Cholecalciferol (Vitamin D3)
Normal range for ionized calcium
1.12-1.32 mmol/L or 4.5-5.3 mg/dL
Parathyroid hormone MOA
closely regulates free ionized fraction of Ca2+
↑ bone resorption and renal tubular reabsorption of Ca2+
Ionized fraction of Ca2+ regulates PTH secretion by negative feedback mechanism
Hypocalcemia stimulates and hypercalcemia suppresses PTH release.
Calcitonin MOA
inhibits bone resorption of Ca2+
opposes parathyroid hormone
Cholecalciferol (vitamin D3) MOA
↑ intestinal absorption of Ca2+ and phosphate (PO₄³⁻) and increase bone mineralization
Synthesized in sun-exposed skin and provided in the diet – hydroxylated in the liver to 25-OH vitamin D and then in the kidneys to the primary active form of 1,25-(OH)2 vitamin D [1,25-dihydroxycholecalciferol]
What are the cardiac effects associated with increased intracellular Ca2+?
increased contractility, inotropy, and cardiac output