Electrolytes Flashcards
Total body water and the compartment model
-Intracellular fluid (ICF)-> fluid enclosed w/in cells-> tightly regulated and remains pretty stable - regulated by cellular membrane
-Extracellular fluid (ECF)-> fluid surrounds all the cells in the body-> Plasma (fluid component of blood) and Interstitial fluid (surrounds all cells not in blood-> MAINTENANCE IS CRITICAL TO TISSUE PERFUSION
What is third spacing?
intracellular fluid
Composition of Body fluids
Extracellular fluid
-Plasma -> Sodium, Chloride, Protein, Bicarbonate
-Interstitial fluid-> sodium, chloride, bicarbonate
Intracellular fluid
potassium, phosphate, protein
Pressure- 2 pressure forces act to cause fluid shifts in our bodies
- Hydrostatic Pressure-> any pressure that a fluid in a confined space exerts
- Osmotic/Oncotic pressure-> pressure exerted by the MOVEMENT OF WATER in relation to the molar conc of solutes
the RELATIVE DIFFERENCES in osmolality BTWN FLUID COMPARTMENTS will drive osmotic fluid shift
What is Oncotic pressure? (Colloid osmotic pressure)
Big part of Osmotic pressure
-derived from large molecules (albumin)-> oncotic pressure
-25-30 mm Hg range or 0.5% of total osmotic pressure-> small contribution to KEEP WATER IN THE VASCULAR COMPARTMENT
Albumin
What is it? Protein made by the liver
Why is it important? maintains consistent amount of fluid in the blood and carries a variety of substances thru body (hormones, vitamins, enzymes)
How do you evaluate it? via CMP
What do the levels mean clinically?
-High levels: dehydration and severe diarrhea
-Low levels: liver disease, kidney disease, malnutrition, infection, IBD, thyroid disease
Main point of albumin
major contributor to the oncotic pressure-> 75%
Conditions that can cause a shift in body fluid: increase in fluid
edema and effusions
-sodium & water retention-> CHF or Renal failure
-increased hydrostatic pressure-> DVT or CHF
-Decreased plasma osmotic pressure-> decreased Plasma albumin -> malnutrition, liver failure, nephrotic syndrome
-lymphatic obstruction-> trauma, fibrosis, invasive tumors, infectious agents
Conditions that can cause a shift in body fluid: Loss of fluid
Sweating
Diarrhea->increased NaCl or LOSS OF ECF WATER LEADS TO SHIFT FROM ICF TO ECF
VOMITING
IV- Parenteral fluids/therapy
Definition: tharpy involving IV administration of crystalloids, colloidal solutions, and/or blood products
Purpose:
-hydration
-IV access for better admin of meds-> rapid therapeutic action needed and pts who are unable/restricted from taking oral preparation
-provides a patent IV line in cases of blood loss and electrolyte depletion
Type of fluids-> generally classified according to molecular weight & oncotic pressure
-CRYSTALLOIDS-> molecular weight < 8000 and low oncotic pressure
-COLLOIDS-> molecular weight >8000 and high oncotic pressure
Types of Fluids
Crystalloid vs colloid overview
Isotonic crystalloids: Lactated Ringers and Normal Saline
MOST COMMON FLUIDS GIVEN, ESPECIALLY DURING ACUTE SITUATIONS
Properties:
-SAME OSMOLALITY AS PLASMA-> DO NOT PROMOTE SHIFTS OF FLUID
-EQUAL TONICITY as plasma-> will NOT cause cells to shrink or enlarge
Use: EXPAND ECF VOLUME-> will cause an INCREASE OF OVERALL FLUID VOLUME -> severe fluid loss- dehydration
EX:
-Normal saline- 0.9% Sodium Chloride
-Lactated Ringer’s solution- water, sodium chloride, sodium lactate, potassium chloride, calcium chloride (more mainstay bc most like body)
–aka LR, Ringer’s lactate, sodium lactate solution, hartmann’s solution
Lactated Ringers- Properties, uses, SE
Properties: MOST SIMILAR TO BODY’S PLASMA & SERUM CONCENTRATION
-contains: water, sodium chloride, potassium chloride, calcium chloride, SODIUM LACTATE-> body metabolizes to bicarb-> ACTS AS A BUFFER-> useful when in sepsis and acidic
Uses:
1. RESTORE FLUID BALANCE AFTER SIGNIFICANT BLOOD LOSS OR BURN
2. Irrigating trauma wounds, or surgical procedures
3. Keep vein open
4. SEPSIS MANAGEMENT
5. used when large volumes of fluid needed- RESUSCITATION
SE:
-FLUID OVERLOAD-> SWELLING AND PERIPHERAL EDEMA, in pts who cannot handle extra fluid= CHF, CKD, CIRRHOSIS-> pts cant process large volumes of lactate
-hypokalemia
-hyponatremia
Normal Saline- properties, uses, side effects
Properties: MOST COMMONLY USED SOLUTION FOR INITIAL REPLETION
Uses: Dehydration, Hypovolemia, DKA, Hyperosmolar hyperglycemic state, headaches, trauma, sepsis
SE:
1. Hyperchloremic acidosis-> secondary to high chloride content relative to plasma
2. Peripheral edema->2ndary to significant extravascular distribution of normal saline
use w/ extreme caution w/ cardiac, renal compromise bc potential for sodium induced fluid retention
Normal saline vs lactated ringers
Normal saline
- lasts longer than lactated ringers
-high chloride content
Lactated ringers
-does not not last as long in the body as NS
-contains additive sodium lactate-> body metabolizes to bicarbonate
-contains many of the same electrolytes as blood
HARMFUL FOR CIRRHOSIS
Both
-Isotonic IV FLUIDS
-Same osmotic pressure as blood
-can cause fluid overload/edema
Crystalloids: hypotonic
Hypotonic solutions-> cause water to shift from ECF to ICF
MAIN INDICATIONS ARE FOR FLUID MAINTENANCE->DOSE= 4:2:1 RULE
4 mL per kg per hour for first 10 kg then 2 mL/kg per hour for every kg over 20
1. D5W-> dextrose in water
-glucose for quick energy for cells - free water to all compartments-> often used for diabetic pts who are NPO but may impair glucose control
-AVOID FOR RENAL FAILURE, CARDIAC COMPROMISE, RISK OF INCREASED INTRACRANIAL PRESSURE
- 1/2 Normal Saline- 0.45% NaCl
-used for Hypernatremia (long term use) or DKA
-Avoid in pts w. burns, trauma, or liver disease
-increased risk of IV infiltration vs. isotonic - D5 1/2 NS-> Dextrose in half normal saline
post surg pts who are NPO
Crystalloids: hypertonic
Hypertonic-> cause water to shift from ICF to ECF
~3% NaCl~
Indication: SEVERE SYMPTOMATIC HYPONATREMIA
Caution: Osmotic demyelination syndrome with TOO RAPID CORRECTION
>12 mEq/L/d for acute hyponatremia— never- 5-10
> 8 mE/L/d for chronic hyponatremia
ALWAYS GO SLOW
IV solutions: Colloids
What are they? Large molecules w/ the inability to pass thru semipermeable membranes thus they stay in the blood vessels
Why are they useful?
-aka volume/plasma expanders-> draw fluid from interstitial space back into BV as they have increased Oncotic pressure
-require less Volume than crystalloids-> good for pts who can’t handle large fluid volumes
Indications: shock, external burns, pancreatitis, peritonitis, post op albumin loss
Types:
1. protein
-ALBUMIN
-Gelatin
2. Starch
-Dextran
-Hydroxyethyl starches
Protocols for IV Fluids in the adult
5 R’s
Resuscitation
Reassess
Routine maintenance
Replacement
Redistribution
5 R’s- Resuscitation
pt w. obvious Fluid deficit IN NEED OF URGENT FLUIDS: (baby cry w/out tears)
1. Assess Volume Status via PE, Vitals, Labs
-hypotension, tachy, prolonged cap refill, cool extremities, skin turgor, electrolyte levels
Fluids:
-GIVE 500 mL BOLUS of crystalloid (NS or LR) over 15 minutes
REASSESS-> does pt still need resuscitation
-repeat fluid bolus in 250-500 mL increments up to 2500 mL PRN
REASSESS
5R’s Routine maintenance
pt cannot meet routine fluid needs orally but is otherwise stable
NORMAL MAINTENANCE NEEDS:
-25-30 mL/kg/day H2O
-1mmol/kg/day K+
50-100 g/day glucose
usually short term and low volume-> pts will only 1- 2 L
NS is adequate if admin slowly
pt w/ longer term needs-> may need to alternate with D5W or a mixed NS/glucose solution
REASSESS
5R’s- Replacement & Redistribution
Pt has existing fluid and/or electrolyte imbalances
-dehydration, fluid overload, HYPER/HYPO - LYTE –> Estimate deficits or excess
Ongoing losses
-vomiting, sweating/fever, Urinary —> Estimate amounts lost
Prescribe REPLACEMENT fluids by adding or subtracting from routine maintenance amount
Check for REDISTRIBUTION
-peripheral edema, heart failure, severe sepsis–> fluid depends on clinical scenario
REASSESS
Hyponatremia
MC electrolyte disorder-> acute or chronic-> elderly and hospitalized pt
Na < 135
Causes: a failure to excrete water normally-> excess water retention> too little sodium
-iatrogenic-> excess hypotonic IV Fluid 0.45% NaCl
-volume depletion- GI causes, diuretics
-edamatous states-> HF, liver disease
SIADH
Symptoms: nausea, malaise, headache, disorientation, eventual brainstem herniation
Confirm that pt has hypotonic hyponatremia-> evaluate volume states
1. Hypovolemic
-replace intravasc volume with 0.9% NaCl or LR
2. Euvolemic
-restrict fluid intake
-tx underlying cause-> demeclocycline for chronic SIADH or conivaptan for acute SIADH
3. Hypervolemia
-Restrict fluid & salt intake
-diurese pt
-tx underlying cause -> conivaptan or Tolvaptan to target ADH
