Fluid And Blood Flashcards
Reasons for fluid management
- Maintain intravascular volume
- Augmenting CO
- Maintain tissue perfusion
- Promoting O2 delivery
- Correcting/maintaining electrolyte balance
- Enhancing microcirculatory flow
- Facilitating delivery of nutrients
- Clearance of metabolic waste
Total body water percentages
60% of total body weight
Intracellular volume (24L) -40% total body weight
Extracellular volume
-20% total body weight
Extracellular volume/fluid compartment
-interstitial fluid volume: 75% of ECV (9.6L)
-plasma volume: 25% of ECV (2.4L)
Total body water percentages of males/females/infants
Males: 55%
Females: 45%
Infants: 80%
- obese individuals have less TBW per weight than non-obese. Fat does not have as much water so lower calculation for them
- elderly have less water, but don’t change calculation
Fluid compartments are divided by what?
Water permeable membranes
- intracellular space is separated from the extracellular space by the cell membrane
- capillary membranes separates the components of the extracellular space. In between the interstitial and plasma volume
The intracellular fluid compartment has a high concentration of what electrolytes?
Potassium (primary cation)
Phosphate (primary anion)
Magnesium
What maintains the high concentration of K in the intracellular fluid?
Sodium-potassium pump
Uses ATP for active transport
3 Na out per 2 K in, uses 1 ATP
The extracellular fluid compartment has a high concentration of what electrolytes?
Sodium (primary cation)
Chloride (primary anion)
This makes up about 1/4 of the extracellular volume and has a high concentration of what?
Intravascular fluid or plasma
Albumin
T/F: Capillary membrane is essentially impermeable to plasma proteins?
True
They create an osmotic pressure to pull fluid in to try to dilute solute and balance concentrations.
This makes up 3/4 of the extracellular fluid compartment and is fluid in tissue spaces
Interstitial fluid
Fluid movement across fluid compartments is affected by:
-Properties of membranes separating the compartments
Concentration of osmotically active substances within a compartment
This fluid space is the chief focus of our fluid therapy, why?
The intravascular fluid space bc this is an accessible fluid compartment
What are the 4 things that determine starling forces?
- Hydrostatic pressure in the capillary
- Hydrostatic pressure in the interstitium
- Oncotic pressure of the capillary
- Oncotic pressure of the interstiitium
This is used to calculate the overall pressure of a compartment to find the need driving pressure
Starling equation
What 3 factors affect fluid movement?
- Osmolarity: expression of the number of osmolality of a solute in a liter of solution
- Osmolality: expression of the number of osmolality of a solute in a kilogram of solution
- Tonicity: how a solution affects cell volume
Hypovolemia
AKA: volume depletion
- loss of extracellular fluid
- absolute loss of fluid from the body
- reduced circulating volume
*balance is there, just less volume
Dehydration
- concentration disorder
- insufficient water present in relation to sodium levels.
*can be caused by different things, not just fluid loss. Balance also off
Hypervolemia
- excess fluid volume in an isotonic concentration
- not usually a problem with surgical patients
Hypervolemia may be seen in surgical what patients?
CHF
Renal failure
Over hydration with isotonic IVF
What is the most abundant electrolyte in the ECF?
Sodium
What is responsible for normal osmotic activity of the ECF?
Na+ and accompanying anion Cl-
All sodium gain/loss is accompanied by what?
Water gain/loss
What are the extracellular and intracellular sodium levels?
ECV: 140 mEq/L
ICV: 25 mEq/L
Causes of hyponatremia
Vomiting Diarrhea Diuretics Adrenal insufficiency Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) Renal failure Water intoxication CHF Liver failure Nephrotic syndrome
*you’re either losing sodium or gaining too much water
What is the most common electrolyte abnormality is hospitalized patients?
Hyponatremia
Clinical manifestations of hyponatremia
Neurologic
- HA
- malaise
- agitation
- coma
- cerebral edema
- confusion
GI
- anorexia
- N/V
Muscular
- cramps
- weakness
What is most significant risk of hyponatremia?
Cerebral edema
Na can’t cross BBB. Great increases Na and will pull fluid in causing the brain to swell
Treatment of hyponatremia
- fluid restriction
- hypertonic saline and an osmotic loop diuretic
- correction of serum sodium levels too fast can result in neurological damage and myelinolysis
- see Nagelhout pg 362 on how to correct
How rapidly should a low sodium level be corrected?
No more than 1-2 mEq/L/hr
Causes of hypernatremia
*not as common
- most common cause is water deficiency d/t:
- excessive loss
- *inadequate intake
- exogenous Na load
- primary hyperaldosteronism
- diabetes insipidus
- renal dysfunction
Clinical manifestations of hypernatremia
Neurologic
- thirst
- weakness
- seizure
- hallucinations
- irritability
- disorientation
- coma
- intracranial bleeding
CV
-hypervolemia
Renal
- polyuria or oliguria
- renal insufficiency
Treatment of hypernatremia
- replacing the water deficit *see nagalhout p363
- plasma sodium should be decreased by 1-2 mEq/hr until the pt is clinically stable
- correction should progress gradually over a 24 hr time frame
This makes up 87% of the body’s potassium supply and how is it balanced?
Intracellular electrolyte
Balanced by GI absorption and renal excretion
Intracellular and extracellular K levels
Intracellular: 150-160 mEq/L
Extracellular: 3.5-5.0 mEq/L
Largely responsible for resting membrane potential
Causes of hypovolemia
GI losses Systemic alkalosis Diabetic ketoacidosis Diuretic therapy Sympathetic nervous system stimulation Poor dietary intake
What is the most commonly seen electrolyte abnormality is our clinical practice?
Hypokalemia
Clinical manifestations of hypokalemia
CV
- ST-segment depression
- presence of U wave
- flattened or inverted T waves
- ventricular ectopy
Neuromuscular
- weakness (respiratory muscle)
- decreased reflexes
- confusion
- <2.5 pt will likely have parisesias and decreased reflexes
Treatment of hypokalemia
-slow IV potassium supplements
Anesthesia concerns with hypokalemia
- increased risk of myocardial irritability (K < 2.6)
- avoid hyperventilation of the lungs
- avoid glucose containing IV solutions
- avoid rapid infusion of IV K supplements
*normal replacement rate is 10-2- mEq/hr
Causes of hyperkalemia
Increased total body potassium
- renal failure
- k-sparing diuretics
- excessive IV K supplements
- excessive use of salt substitutes
Altered distribution of potassium
- metabolic or respiratory acidosis
- digitalis intoxication
- insulin deficiency
- hemolysis
- tissue and muscle damage after burns
- admission of succinylcholine
Clinical manifestations of hyperkalemia
CV
- tall, peaked and elevated T wave
- widened QRS complex
- prolonged PR interval
- flatted or absent P wave
- ST segment depression
- cardiac arrest
Treatment of hyperkalemia
Primary goal
- avoid adverse cardiac effects
- insulin and glucose to shift K into cells
- IV calcium to antagonize cardiac effects: 1st line of defense bc it helps to generate an action potential
What is the upper K limit for elective procedures?
5.5 mEq/L
Percentage of magnesium stored in muscle/bone, cells, and serum
Muscle/bone; 40-60%
Cells: 30%
Serum: 1%
What regulates magnesium levels?
Intestines had kidneys
What role does magnesium play in the body?
Cofactor in enzymatic reactions
- energy metabolism
- protein synthesis
- neuromuscular excitability
- function of Na-K-ATPase
What is considered hypomagnesemia?
Serum mag < 1.7 mEq/L
What causes hypomagnesemia?
Inadequate dietary intake
TPN w/o mag supplementation
Starvation
GI loses
- diarrhea
- fistulas
- NG suctioning
- vomiting
Chronic alcoholism
Clinical manifestations of hypomagnesemia
ECG
- flat T-waves
- U-waves
- prolonged QT interval
- widened QRS
- atrial and ventricular PVCs
*low mag has an inhibitory effect on ATPase pump and alters resting membrane potential
Treatment of hypomagnesemia
IV administration of mag sulfate
- 1-2g over 5 minutes with EKG monitored
- followed by continuous IV infusion 1-2 g/hr
What is considered hypermagnesemia?
Serum mag > 2.5 mEq/L
Causes of hypermagnesemia
Iatrogenic administration
- preeclampsia
- antacids/laxative
Renal failure
Adrenal insufficiency
Clinical manifestations of hypermagnesemia based on labs (mEq/L)
3-5: flushing n/v 4-7: drowsiness, decreased deep tendon reflexes, weakness 5-10: hypotension, bradycardia 7-10: loss of patellar reflex 10: respiratory depression 10-15: respiratory paralysis, coma 15-20: cardiac arrest
Treatment of hypermagnesemia
D/C supplemental mag
Use calcium as an antagonist in urgent situations
- bradycardia
- heart block
- respiratory depression
What does magnesium do to resting membrane potential?
Decreases it
What does calcium do to resting membrane potential?
Increases it
What will magnesium do to non-depolarizing neuromuscular blockers?
It will potentiate them
Where is calcium stored in the body?
99% found in bones
1% found in plasma and body cells
Functions of calcium in body?
Structural integrity of bones
- second messenger that couples cell membrane receptors to cellular responses
- muscle contraction, hormones, neurotransmitters, coagulation, myocardial contractility
This is the best lab to determine physiologically active calcium
Ionized calcium
Normal: 9.0-10.5
Calcium level is maintained/regulated by what 2 things?
Calcitonin: drives calcium into bones
Parathyroid hormone: pulls it out
Causes of hypocalcemia
Hypoparathyroidism
Malignancy
Chronic renal insufficiency
What are the 2 most common causes of intra-operative hypocalcemia?
Hyperventilation (leads to alkalosis which causes protein binding to calcium)
Massive transfusion (due to citrate in blood products binds to calcium)
Manifestations of hypocalcemia
Neuromuscular irritability
- cramps
- weakness
- Chvostek sign: clinal sign of hyperexcitability. Abnormal reaction to stimulation of facial nerve
- Trousseau sign: carpal spasm when upper arm is compressed. Indication of latent tetany
- seizure
- numbness
- tingling
Clinical manifestations of hypocalcemia
CV
- dysrhythmias
- prolonged QT interval
- T-wave inversion
- hypotension
- decreased myocardial contractility
Pulmonary
- laryngospasm
- bronchospasm
- hypoventilation
Treatment of hypocalcemia
Infusion of calcium salts
Calcium chloride
- more bioavailable
- more rapid correction (best)
Calcium fluctuate
- slower (has to be altered by body first)
- 3 grams = 1 gram calcium chloride