Week 1- Fluids, Electrolytes, Acid Base Status Flashcards
How much fluid is in:
1) a full-term baby?
2) Lean Adult Male?
3) Aged client?
1- 80%, 2- 60%, 3- 40%
What % of the body is solid vs Fluid?
40-45%, 55-60%
what portion of fluid is ECF vs ICF?
2/3 ICF
1/3 ECF
What % of ECF is interstitial fluid vs plasma?
IF- 80%, Plasma- 20%
what happens if there is more space between cells?
harder for glucose/ O2 etc. to go through, more space to travel
Compartments of ECF
- Cerebrospinal fluid (surrounds brain and spine)
- lymph
- synovial fluid (joints, adds lubrication)
- pleural fluid (protect lungs & heart)
- peritoneal fluid (abdominal)
- pericardial fluid (heart)
Functions of water in body?
1) solvent- dissolves salts + electrolytes
2) chemical reactant
3) lubricant
4) moderate temp changes
5) coolant: perspiration cools body
where does the most water GAIN come from?
- Ingested liquids
- Ingested foods
- metabolic water
where is the most water LOSS?
- Kidneys (pee)
- Skin (sweat)
- lungs (heat when you breathe out)
- GI tract
Sensible fluid losses
Measurable losses
- urination
- defecation
- wound drainage
Insensible fluid losses
Unmeasurable losses, require estimation for replacement
- Evaporation from skin
- Evaporation from breathing
paths of body fluid movement between body compartments? (2 beginnings)
- Arterial capillaries→ Interstitium→ cells
- Cells → interstitium → route A and B
A→ lymphatics (~15%)
B→ Venous capillaries (~85%)
2 Key factors of bulk flow
- Hydrostatic Pressure
- Osmotic Pressure
Hydrostatic Pressure
- BP in capillaries from cardiac contraction
→ exerts outward force on walls of the vessels
→ movement of water out of capillaries
Osmosis
- requires concentration gradient
- diffusion of water across membrane from area of high to low concentration of water molecules
- Applied pressure to raised side = osmotic pressure
Oncotic Pressure / Colloid osmotic pressure
- osmotic pressure of a colloid in solution
- caused by presence of large, charged, insoluble particles such as proteins
- can not cross the semi-permeable membrane
- particles draw water towards them
MAJOR factor of movement in interstitium and cells
differing ion concentrations btw these two compartments
- Na+/K+ pumps → Increase [Na+] outside cell
- Na+ tends to flow in → Na+ can be used to bring in other substances
Second factor of movement in interstitium and cells
cytosol contains large # of negatively charged ions (proteins and phosphates)
- positively charged substances then are attracted
4 regulatory Mechanisms
- Baroreceptors
- Volume receptors
- Renin-Angiotensin-aldosterone mechanism
- Antidiuretic hormone
Baroreceptor Reflex
- Pressure sensors
- Respond to fall in arterial BP
- In atrial walls, vena cava, aortic arch and carotid sinus
- constricts afferent arterioles of kidneys resulting in retention of fluid → sends less blood to kidneys, & holds onto more water
Volume Receptors
- Respond to fluid excess in atria and great vessels
- Stimulation of these receptors creates a strong renal response that increases urine output
Renin in RAAS
- Enzyme secreted by kidneys when arterial pressure or volume drops
- Interacts with angiotensinogen to angiotensin I (vasoconstrictor)
Angiotensin in RAAS
- Angiotensin I converted in lungs to Angiotensin II using ACE
- produces vasoconstriction to elevate BP
- stimulates adrenal cortex to secrete aldosterone
Aldosterone in RAAS
- mineralocorticoid that controls Na+ and K+ blood levels
- Increases [Cl-] and [HCO3-] and fluid volume
Dehydration
- Only water loss (hypotonic fluid loss)
- Loss of body fluids→ increase conc. of solutes in blood and rise in serum Na+ levels
- fluid shifts out of cells into blood to restore balance
- cells shrink from fluids loss, no longer function properly
Hypovolemia
- Isotonic fluid loss from the EC space
- can progress to hypovolemic shock
- caused by:
- Ecessive fluid loss (hemorrhage)
- decreased fluid intake/ not eating over time
- third space fluid shifting
1st space? 2nd space? 3rd space?
1- blood
2- inside cell
3- interstition
Hypervolemia
- excess fluid in EC compartment as result of fluid or Na retention, excessive intake, or renal failure
- occurs when compensatory mechanisms fail to restore fluid balance
- leads to congestive heart failure (CHF) and pulmonary edema
Edema
- abnormal accumulation of IF
- 4x causes
- giving them fluid but can’t force it to stay where we want it
4 causes of Edema
- increase in blood hydrostatic pressure
- venous congestion, circulatory failure, thrombi - decrease in blood colliod osmotic pressure
- hypoalbuminemia, kidney or liver disease,
severe burns - increase in IF osmotic pressure
- inflammation → exudate formation
- * increase IFOP due to increase capillary
permeability - Obstruction of lyphatics
- surgery
- tumor growth
- parasitic infections
Elephantiasis
as angiotensin II hits kidneys, aldosterone tells kidneys to absorb water
- swollen limbs
Electrolytes
- compound that dissociates into ions when in solution
- ions are charged particles and
- resulting solution can carry an electric current
4 general functions of electrolytes
- control osmosis of water between compartments
- help maintain the acid-base balances need for cellular activity
- carry electrical current
- serve as cofactors
Sodium
- Major EC cation
- Attracts fluid and helps preserve fluid volume
- Combines with Cl and HCO3 to help regulate acid-base balance
- Normal range of serum Na 135-145 mEq/L
Normal Levels of Sodium?
135-145 mEq/L
What happens if sodium intake increases?
- [ECF] increases
- increased thirst and release of ADH (antidiuretic)
- tiggers kidneys to retain more water
- aldosterone also increases Na+, H2O and Fluid
Functions of Sodium-Potassium Pump
- Na+ outside tries to get inside
- K+ inside tries to get outside
- pump maintains normal conc. using ATP, magnesium, and an enzyme
- pump prevents cell swelling, creates electrical charge allowing neuromuscular impulse transmission
Potassium
- Major INTRAcellular cation
- untreated changes in K+ levels lead to serious neuromuscular and cardiac problems
- Normal levels: 3.5-5mEq/L
Normal Potassium levels
3.5-5 mEq/L
Factors influencing K+ balance
- Na+/K+ pump
- Renal regulation
- pH levels
How does Renal Regulation influence K+ balance?
- increased K+ levels→ increased K+ loss in urine
- Aldosterone secretion causes Na+ reabsorption and K+ excretion
How does pH influence K+ balance?
- Potassium ions and hydrogen ions exchange freely across cell membrane
- Acidosis → hyperkalemia (K+ moves out of cell)
- Alkalosis → hypokalemia (K+ moves into cell)
Hyperkalemia
- K+ > 5mEq/L
- less common
- caused by altered kidney function, increased intake (salt substitutions), blood transfusions, meds (K+ sparing diuretics), cell death (trauma)
Magnesium
- helps produce ATP
- Role in protein synthesis & carbohydrate metabolism
- helps cardiovascular system function (vasodilation)
- regulates muscle contractions
- Normal levels Mg2+: 1.5-2.5 mEq/L
Normal levels of Magnesium
1.5-2.5 mEq/L
Hypermagnesemia
- Mg++ > 2.5mEq/L
- not common
- renal dysfunction most common cause
~ renal failure
~ Addison’s disease
~ Adrenocortical insufficiency
~ untreated Diabetic Ketoacidosis (DKA)
Hypomagnesemia
- Mg++ < 1.5mEq/L
- caused by poor dietary intake, poof GI absorption, excessive GI/urinary losses
- High risk clients
~ chronic alcoholism
~ Malabsorption
~ GI/ urinary system disorders
~ Sepsis
~ burns
~ wounds needing debridement
Calcium
- 99% in bones, 1% serum and soft tissue (measure by serum)
- works with phosphorus to form bones and teeth
- role in cell membrane permeability
- affects cardiac muscle contraction
- participates in blood clotting
Normal Calcium levels (serum and ionized)
Serum: 8.9-10.1 mg/dl
ionized: 4.5-5.1 mg/dl
Hypocalcemia
serum: <8.9 mg/dl
ionized: <4.5 mg/dl
- caused by inadequate intake, malabsorption, pancreatitis, thyroid or parathyroid surgery, loop diuretics, low magnesium levels
Hypercalcemia
serum: >10.1 mg/dl
ionized: > 5.1 mg/dl
Two major causes:
- cancer
- hyperparathyroidism
Chloride
- Major Extracellular anion
- Na+ and Cl- maintain water balance
- secreted in stomach as HCl
- Aids CO2 transport in blood
Normal Chloride levels
96-106 mEq/L
Hypochloremia
<96 mEq/L
- caused by decreased intake or decreased absorption, metabolic alkalosis, and loop, osmotic, or thiazide diuretics
Hyperchloremia
> 106 mEq/L
- not common, rarely occurs alone
- causes: dehydration, renal failure, resipiratory alkalosis, salicylate toxicity, hyperpara-thyroidism, hyperaldosteronism, hypernatremia
Normal pH in blood
7.35-7.45
- narrow, crucial for enzyme activity and to prevent tissue damage
Acidosis vs Alkalosis
- pH < 7.35
- pH > 7.45
Sources of H+ in body (3 major)
- Cell Respiration
- complete combustion of glucose yeilds CO2 + H2O) - Incomplete combustion of glucose yeild organic acids
- lactic acid, ketones - ingestion of acid products
- drug overdose (asprin, TCA, increase breathing)
3 Acid-Base Regulatory systems
- Buffers
- major buffer = HCO3- (carbonic acid system) - Respiratory therapy system
- regulates CO2 loss - Kidneys
- secrete H+
- Reabsorb HCO3-
What is a buffer system
- SA/SB converted to WA/WB
- modifies release of H+ and prevents drastic pH change
- done w/in fraction of a second
types of buffer systems
- carbonic acid- bicarbonate
- phosphate
- protein
Carbonic Acid-Bicarbonate System
- plasma and ECF buffer (in blood)
- kidney nomally maintains 20:1 supply of HCO3-:H2CO3
- respiratory system regulates amount of CO2
Phosphate Buffers
- Intracellular buffer (also used to buffer in urine)
- phoasphates can bind and release H+
- can buffer and acid or base
Protein buffers
- intracellular and plasma buffer
~ ex. hemoglobin in RBCs buffers H2CO3 - each protein has a carboxyl terminal and an amino terminal
- can buffer both acid or base
What happens during Hyperventilation?
What happens during hypoventilation?
How is pH monitored and what happens?
- chemoreceptors (medulla, aortic, carotid bodies)
- monitor [CO2]/[H+] of blood
- send a message to inspiratory control center (brainstem) to alter rate of respiration
How do kidneys regulate pH?
Excreting H+:
- secrete H+ into urine in exchange for Na+; H+ competes with K+ regulating bicarbonate concentration
~ reabsorbs and synthesizes new HCO3-
*renal failure can quickly cause death
kidneys → slow system → hours to days
How to maintain acceptable Urine pH
- two buffers in urinary filtrate to combine with H+ and prevent Urine becoming too acidic
- HPO4– → H2PO4-
- NH3 → NH4+
Normal PaCO2
35-45 mmHg
Normal HCO3 conc.
22-26 mmol/L
Respiratory Acidosis
→ decrease exhalation of CO2
(hypoventilation) (think: resp=lungs)
→ increase PaCO2, pH < 7.35
causes:
- ephysema (smoking too much, cant breathe out)
- pulmonary edema (too much fluid in lungs)
- brainstem injury ( signal isn’t happening)
- airway obstruction
How do you compensate Respiratory Acidosis
- kidneys compensate by increasing H+ secretion and HCO3- reabsorption
- slow: hrs, days
Respiratory Alkalosis
→ increase exhalation of CO2
(hyperventilation) (think: resp=lungs)
→ decreas PaCO2, pH > 7.45
causes:
- CVA (cerbrovascular accident/ stroke)
- anxiety
- O2 deficiency (eg. high altitude)
How do you compensate Respiratory Alkalosis
- kidneys compensate by decreasing H+ secretion and HCO3- reabsorption
Metabolic Acidosis
Loss of HCO3-
- Severe diarrhea
- renal dysfunction
- or buffer overwhelmed:
drug overdose, ketosis, lactic acidosis
Metabolic Acidosis Compensation
hyperventilation to increase CO2 exhalation
- decrease CO2 in system +H2O → H2CO3 → decrease HCO3- + H+
Metabolic Alkalosis
- loss of acid
causes: - vomiting (loss of stomach HCl)
- alkaline drugs
- too much HCO3- in IV
Metabolic Alkalosis Compensation
Hypoventilation (decrease CO2 release)
