GI IV Fluids Flashcards
What is a crystalloid?
based on a solution of sterile water with added electrolytes to approximate the mineral content of human plasma
What is the purpose of giving a crystalloid IV?
reduce colloid osmotic pressure via hemodilution
What is a colloid?
- often based on crystalloid solutions, so contains water and electrolytes
- also contain colloid substance that does not freely diffuse across semipermeable membranes (eg albumin, dextran)
What is the purpose of a colloid?
maintain or increase colloid osmotic pressure
Are crystalloids or colloids used more often? Why?
- crystalloids preferred
- colloids are substantially more expensive and lack date showing their superiority
What is special about Lactated Ringers?
- most closely mimics the electrolyte concentration of human plasma
- also has a small amount of lactate included
What is the most common dextrose crystalloid?
D5W
What components make up D5W?
5% dextrose and sterile water
What is the normal level of plasma osmolality?
290 (normal range 240-340)
Water makes up what % of body weight in men and women?
- men 60%
- women 50%
What is the breakdown of total body water intra vs extracellular?
- intra: 2/3
- extra: 1/3
What is the normal obligatory fluid intake for adults in a day? What is the breakdown (where do they get their fluids)?
- 2600 mL/day
- ingested water 1400 mL
- water in food 850 mL
- water of oxidation 350 mL
What is the normal obligatory fluid output for adults in a day? What is the breakdown (where do they eliminate their fluids)?
- about 2600 mL/day
- urine 1500 mL
- skin 500 mL
- respiratory tract 400 mL
- stool 200 mL
How does volume depletion occur?
Na+ and/or water loss from different sites (GI, renal, skin/resp, third space)
How does volume depletion occur in GI system?
vomiting, diarrhea, bleeding
How does volume depletion occur in renal system?
effects of diuretics, osmotic diuresis, salt wasting nephropathies, hypoaldosteronism
How does volume depletion occur in skin/respiratory system?
insensible losses, sweat, burns
How does volume depletion occur with third-space sequestration?
intestinal obstruction, crush injury, fracture, acute pancreatitis
How does volume depletion manifest clinically (signs and sxs)?
- primarily related to decreased tissue perfusion
- early S/S: lassitude (exhaustion, weariness), easy fatiguability, thirst, muscle cramps, postural dizziness
- more severe fluid loss: abdominal or chest pain, lethargy, confusion
How can one tell clinically that interstitial volume is decreased?
- examine skin and mucous membranes
- skin tenting, dry or clammy skin, dry buccal mucosa
- parched or cracked lips, deep set or sunken eyes
How can one tell clinically that plasma volume is decreased?
- reductions in BP and venous pressure in jugular veins
- tachycardia, cap refill >2-3 seconds
What can happen clinically due to electrolyte and acid-base imbalances that happen with volume depletion?
- muscle weakness to due hyperkalemia/hypokalemia
- polyuria and polydipsia due to hyperglycemia or severe hypokalemia
- lethargy, confusion, seizures, and coma due to hyponatremia, hypernatremia or hyperglycemia
What are the 3 goals of dehydration treatment?
- identify and correct underlying cause of hypovolemia
- restore euvolemia with fluid similar in composition to what was lost
- replace ongoing losses
How is mild dehydration treated vs severe dehydration?
- mild: usually via oral
- severe: usually requires IV
What should patients with significant anemia, hemorrhage or third-spacing need?
-blood transfusion and colloid
What is the solution of choice in normonatremia and mildly hyponatremia patients or initially in HoTN/shock patients?
-isotonic or normal (0.9%) saline
What type of fluid should be used when extracellular fluid volume expansion is desired?
isotonic
What might severe hyponatremia require?
hypertonic (3%) saline
Replacement Therapy
-corrects any existing water and electrolyte deficits
Maintenance Therapy
-replaces ongoing losses of water and electrolytes under normal physiologic conditions, via urine, sweat, respiration and stool
What is the goal of fluid REPLACEMENT therapy?
-correct existing abnormalities in plasma electrolytes and volume status
What type of fluid is given for replacement therapy?
-depends on type of fluid lost and any concurrent fluid or electrolyte disorders
What might provide a reasonable estimate of fluid losses?
-weight loss if the pre and post-deficit body weights are known
If weight loss is not known, how is volume depletion assessed?
- with clinical and laboratory parameters
- eg BP, skin turgor, urine output, urine sodium excretion, osmolality
At what rate must severe volume depletion or hypovolemic shock be given fluids?
- 1-2 liters of NS given as rapidly as possible
- then continued at a rapid rate until clinical signs normalize
At what rate should mild to moderate hypovolemia be given fluids?
- optimal rate somewhat arbitrary
- 50-100 mL/hour in excess of continued losses
What patients require caution with IV fluids and why?
- hypo/hypernatremia: overly rapid correction of Na_ can lead to irreversible neurologic damage
- pts at risk of fluid overload: renal/cardiac/hepatic failure, older adults
What 4 components must be considered in maintenance IV therapy?
- water
- sodium
- potassium
- carbohydrates (minimize protein catabolism)
What component will kill a patient first with IV therapy if a mistake is made in calculations?
potassium
What are the water requirements for patients? (Holliday Segar Formula)
- pt weight in kilos plus 40 mL/hour
- OR 60 mL/hr + 1 mL/kg/hr for any increment of weight over 20kg (max of 120 mL/hr)
How much sodium and potassium are needed each day?
- Sodium: 1-2 mEq/kg/day
- Potassium: 0.5-1 mEq/kg/day
How much dextrose does the average adult need each day?
-for 70 kg man, 100-150 gm/day
-can try to do 50 times the L/day of H2O
What does replacement of water losses from the skin and respiratory tract depend upon?
-resp rate, ambient temp, humidity, body temp
How does a fever affect water loss and fluid replacement?
for each degree of body temp >37 C, water losses increase by 100-150 mL/day
What should insensible losses be replaced by?
-5% dextrose or hypotonic saline
Which GI losses have a greater than average K+ loss?
- diarrheal #1
- also gastric and salivary
What types of renal losses occur and why?
- sodium: diuretic use, recovery phase of ATN, post-obstructive diuresis, interstitial renal dz, mineralocorticoid deficiency
- potassium: recovery phase of ATN, renal tubular acidosis, diuretic use, catabolic states, hyperaldosteronism
What are 3 common problems with IV fluids?
- over or under HYDRATION
- too much or not enough SODIUM
- too much or not enough POTASSIUM
How might underhydration occur with IV fluids?
- wrong rate of fluid for body weight
- not calculating for other losses
- not calculating for pre-existing fluid deficits
How might overhydration occur with IV fluids?
- wrong rate of fluid for body weight
- not taking into account pre-existing fluid overload
- not considering renal dysfunction
Why might a pt receive too much sodium with IV fluids?
- using endless bags of normal saline in euvolemic patient
- not monitoring serum sodium for someone who has had many bags of IV fluid
Why might a pt receive too little sodium with IV fluids?
- using hypotonic fluids in pts who are very ill or for prolonged periods
- not monitoring serum sodium for someone who has had many bags of IV fluid
Why might a pt receive too much potassium with IV fluids?
- not monitoring potassium
- not considering renal dysfunction
Why might a pt receive too little potassium with IV fluids?
- forgetting to include potassium (esp post-op)
- not calculating for losses of K+ rich fluid (diarrhea, vomit)
Monitoring of IV Therapy
- vitals signs
- clinical appearance: volume excess (edema) or volume depletion (decreased turgor and BP)
- daily weight
- urine output and specific gravity
- serum electrolytes (for inpatient, 1x/day)
