Some New Terms
o Total body water
§ Sum of all the water or fluids within all of the body compartments in the pt. makes up 60% of body weight.
o Intracellular fluid (ICF)
§ Within cells 2/3 of total body water.
o Extracellular fluid (ECF)
§ Outside of cells 1/3 of total body water.
§ Additionally there is sweat, urine.
o Interstitial Fluid
§ Fills the space around the cells and outside of blood vessels.
o Intravascular Fluid
§ Fluid in the blood vessels (plasma)
· Osmolarity and Osmotic pressure
o Osmolality: concentration of a solute per kilogram of water
§ Primary electrolyte is sodium.
o Osmolarity concentration of solute per liter of a solution.
§ Creates osmotic pressure.
o Osmotic Pressure: the pulling power of a solution for water.
o Isotonic Solution: physiologically equivalent to blood plasma (no osmotic diff, no shifting of fluids occurs) and other body fluids, stay in ECF space. e.g. Normal Saline, ringers, lactated ringers.
§ Replacing water.
o Hypotonic: less concentrated solution
§ Pull water out of vessels into cells. Increased cell water and decreased vascular fluid. e.g. given if cells are dehydrated, renal failure. D5 (5% dextrose) half normal saline, D5 water (5% dextrose with water), drives water into cells. Contraindicated for fragile neural cells, we don't like swelling brains (cerebral edema). Have to be monitored.
o Hypertonic: A more concentrated solution
§ Given for drastically low sodium level or hypoglycemic given D50 (50% dextrose), D10 (10% dextrose) newborn with diabetic mother. Have to be monitored.
§ e.g. high percentage saline
o Hypotonic: A more dilute solution
· Oncotic Pressure
o Oncotic pressure (colloid oncotic pressure): the pulling force exerted by colloids in a solution
§ Albumin - most important colloid for maintaining oncotic pressure, helps maintain adequate vascular pressure. Sits in vessels and pulls fluid into blood vessels.
§ Administered for patients with third space fluid, draws fluid back into vascular system so we can pee it out.
· Capillary filtration
o Capillary hydrostatic pressure
§ Pushing the water out of the capillary
§ Fluid moves out of capillaries into tissues.
o Capillary oncotic pressure
§ Pulling water into the capillary
o In artery CHP greater than COP fluid moves into tissues, in vein COP greater than CHP fluid moves into vessels.
· Chemical Regulation of fluid balance
o ADH (antidiuretic hormone)
§ acts on distal tubules of the kidneys
§ Secreted by posterior pituitary, regs water balance by acting on distal tubules of the kidneys
§ Increase in BP, rise in osmolality, kidneys get rid of more water (neg feedback loops) Blood volume low, cause renal tubules to not get rid of water.
o Aldosterone
§ Secreted from adrenal gland
§ causes kidneys to secrete K+ instead of Na+
§ Water follows sodium, helps body hang onto extra water (neg feedback loop)
o Glucocorticoids
§ Cortisol, promote renal retention of Na+ and H2O
o Atrial natriuetic peptide (ANP) and Brain natriuretic peptide (BNP)
§ released with high blood volume or blood pressure causing vasodilation, trigger aldosterone and ADH to be released.
§ Found in either atria or ventricles released into body when atria or ventricle is stretched.
§ There is a blood test for BNP
o Thirst Mechanism
§ When as much as 1 milliosmol/liter decrease in amount of water needed.
§ Triggers aldosterone and ADH.
§ Depressed in elderly. More likely to experience dehydration.
· Alterations in Water balance
o Dehydration
§ More body water loss than taken in
o Overhydration
§ More body water taken in than loss.
· Alterations in Water Balance
o Isotonic Alterations
§ Amount gained/loss is proportion to electrolytes gain/loss
§ Isotonic Fluid Loss
§ Lose fluid and electrolytes at same rate - wound, excessive diaphoresis.
§ Isotonic Fluid Excess
§ Gain fluid and electrolytes at same rate - over hydrate with isotonic solution.
· Alterations in Water Balance
o Hypotonic Alterations
§ Osmolality of serum is less than should be (normal). Low sodium level. Water and not enough electrolytes.
§ Water Excess --> water toxicity
§ Drinks too much fluid, hard to develop b/c body has several compensatory mechanisms. Neurological condition to drink large amounts of fluid, marathon runners drinking only water.
§ Confusion, convulsions, muscle twitching, headaches.
o Hypertonic Alterations
§ Osmolality is elevated above normal, more sodium than water.
§ Water Deficit
§ Dehydration from pure water loss.
§ Body can't concentrate urine, ie. lose large volumes of fluid through kidneys, (diabetes) --> hypovolemia (low blood volume)
Alterations in Sodium
· Sodium
o Helps conduct neural impulses, helps reg K+, found in all body fluids, neurological responses.
o nml: 135 to 145 mEq/L (each lab has own normals)
o Hyponatremia below 135
§ Causes
§ Renal disease
§ Diuretics
§ GI losses
§ Skin Losses
§ Wound drainage
o Hypernatremia above 145
§ Causes
§ Decreased water intake
§ Watery diarrhea
§ Fever
§ Hyperventilation
§ Burns
§ Increased sodium dietary intake
· What happens to people?
o hyponatremia
· behavioral changes
§ lethargy
§ confusion
· depressed reflexes
· seizures
· coma
hypernatremia
· thirst
· fever
· dry mucous membranes
· restlessness
· Alterations in Potassium
Potassium, even small changes are poorly tolerated.
· Functions: maintains action potentials of muscles, assists in controlling the cardiac rates/rhythms, conducts nerve impulses.
nml: 3.5 to 5 mEq/L
Mechanisms of regulation
§ renal regulation
§ Kidneys maintain balance by excreting or reabsorbing in glomerulus (mostly).
§ Extra- and intra cellular shifts
§ Temporary shift into RBC (hemoglobin), liver muscles, bone
Hypokalemia
§ Low intake in diet, excessive loss of K+ usually in gut (suctioning), nausea/vomiting, sweating profusely, diabetes encephalitis.
Hyperkalemia
§ Excessive intake of potassium, usually body tolerates well unless a lot given quickly, renal failure, potassium sparing diuretics.
· What happens to the person
Hypokalemia
§ Mild losses asymptomatic
§ Well tolerated
§ Acute Losses cause
§ Skeletal Muscle Weakness
§ Loss of smooth muscle tone
§ Cardiac dysrhythmias
§ Lethargy/Fatigue
§ Inability to concentrate
Hyperkalemia
§ Slow onset usually well tolderated
§ Mild
§ Restless ness
§ Intesting cramping
§ Diarrhea
§ Severe: (see slide)
· Alterations in Calcium and Phosphorus and Magnesium
Vitamin D regulation
§ Calcitriol - form of vit D makes Ca and Phosphorus available for bone mineralization.
§ Helps absorb Ca in intestine.
§ Activates parathyroid hormone.
Parathyroid hormone regulation
§ Helps increase blood calcium levels by transporting Ca out of bones.
§ Aid reabsorption in kidneys
§ Raise serum Ca levels and lowers Phosphorus levels b/c they have an inverse relationship with one another.
· Alterations in Calcium
Muscle contractions, clotting abil, neurological conduction, rigidity to teeth/bones.
Normal level 8.5-10.5 mg/dl
Hypocalcemia
§ Causes
§ Hypoparathyroidism
§ Hypomagnesemia
§ Alkalosis
§ Multiple blood transfusions
§ Malabsorptive states
§ Renal disease
Hypercalcemia
§ Causes
§ Hyperparathyroidism
§ Hypophosphatemia
§ Hyperthyroidism
§ Vitamin D intoxication
§ Steroid therapy
§ Immobility
§ Lithium therapy
· Alterations in Calcium
hypocalcemia
§ Paresthesias (muscle pain)
§ skeletal muscle cramps
§ abdominal spasms and cramps
§ hyperactive reflexes
§ Hypotension
§ bone pain, deformities, factures
hypercalcemia
§ Polyuria (a lot of peeing), polydipsia (very thirsty)
§ anorexia, n/v, constipation
§ Ataxia (uncoordinated muscle movements)
§ osteoporosis
§ lethargy
§ stupor, coma
§ HTN - may be due to inabil of muscle cells to relax fully.
· Alterations in Phosphorus (Phosphate)
Inverse relationship with Ca, essential for muscular function, important for RBC function, cellular metabolism, role in formation of teeth/bones.
Normal level: 2.5 to 4.5 mg/dl
Hypophosphatemia
§ From decreased absorption of Vit D, intestinal loss, less skin absorption, diabetic ketoacidosis, alcoholic, poor dietary intake.
Hyperphosphatemia
§ From renal insufficiency, low blood calcium, chemotherapy, parathyroid gland is understimilated, prolonged Vit D exposure, antacids, salicylates, excessive intake of phos supplements, massive transfusions of blood.
· Alterations in Phosphorus Manifestations
· Hypophosphatemia
Intention tremor
Ataxia, Paresthesias
Seizures
muscle weakness
bone pain
Osteomalacia (softening of bone)
bleeding disorders
impaired WBC fxn
· Hyperphosphatemia
paresthesias
Tetany (rigidity to muscles)
hypotension
cardiac arrhythmias
· Alteration in Magnesium
Usually a function of dietary intake, role in enzymatic process in body, helps power Na/K pump (convert ATP to ADP), transmits electrical impulses across nervous system and MSK, necessary to release parathyroid hormone.
Normal level: 1.8 to 3.0 mg/dl
Hypomagnesia
§ Chronic alcoholism (most common)
§ Decreased dietary intake
§ Decreased absorption d/t GI pathology
§ Increased GI losses
§ Increased Renal excretion
§ Burns
Hypermagnesia
§ Untreated diabetic ketoacidosis
§ Adrenal insufficiency
§ Mg++ treatment in preeclampsia (pregnancy induced HTN)
§ Lithium ingestion
§ Volume Depletion
· Alteration in Magnesium Manifestations
· hypomagnesia
personality change
nystagmus
tetany
tachycardia
hypertension
cardiac arrhythmias
+ Babinski, Chvostek, and Trousseau signs
· hypermagnesia
Lethargy
Hyporeflexia
Confusion
Coma
Hypotension
Cardiac arrhythmias
cardiac arrest
· Acid Base Disturbances
· Acid-Base Balance
Must be regulated in a narrow range to function normally
Lungs, kidneys, and bone regulate the balance
Hydrogen ions maintain membrane integrity and speed enzymatic reactions
Bicarbonate is maintained as well.
pH represents a power of hydrogen
pH < 7.4 is acidic, > 7.4 alkaline
· Buffers
Absorb excess H+ and OH-
Prevent significant change in pH
Exist as acid base pairs
Carbonic Acid Buffering (bicarb) [main system]
§ Lungs and kidneys
§ Changing rate of ventilation (blow off extra CO2 or retain)
§ Retain bicarb or excrete extra in pee.
Protein Buffering (hemoglobin)
§ CO2 loaded onto hemoglobin
Renal Buffering (phosphate)
§ Secreting H ions in urine and reabsorbing bicarb in renal tubules.
· Acid Base Disorders
Metabolic versus Respiratory
§ Metabolic - produce and alteration in bicarb (hydrogen and CO2 associates and disassociates to be moves through system),
§ Respiration - alteration in partial pressure of CO2, increase or decrease in ventilation
Acidotic versus Alkalotic
§ pH level
· Metabolic Acidosis
Decrease HCO3- with decrease pH
Causes
§ Diabetic Ketoacidosis, kidney failure, aggressive suctioning of the GI tract
Compensation in increased resp. rate (blow off CO2) Kussmaul type respiration.
Treatment
§ Treat underlying cause, replace fluid/electrolyte volume.
§ Supplemental sodium bicarb if severe (IV)
· Metabolic Alkalosis
Increased pH due to primary excess of HCO3-
Causes
§ Increase in intake of alkalotic solution (IV, oral [antacids]), vomiting, binge purge.
