Fluid and Blood Therapy Flashcards
TBW calculation
Total Body Water = 0.6% x Body Weight
TBW in L
TBW = 42 L (60%)
ECF = 1/3 or 14 L (20%)
ICF = 2/3 or 28 L (40%)
3 ECF Contents
Interstitial Fluid
Plasma
Transcellular Fluid
Interstitial Fluid
3/4 of ECF = 10.5 L or
15% body weight or
25% TBW
- During surgery, capillary permeability increases and more fluid escapes to the interstitium.
Plasma
1/4 of ECF = 3 L or
5% body weight or
9% TBW
(85% venous, 15% arterial)
Transcellular Fluid
0.5 L
Classic Fluid Compartments Visual
Daily Fluid Output
Urine 0.5 - 1.5 L
Sweat/Respiratory 0.8 - 1.2 L
Feces 0.2 L
Daily Fluid Intake
Fluids
Fluids in Food
Metabolic Fluids
NPO after midnight
Third Space
- nonfunctional space somewhere within the body that accumulates fluids that escape from the vasculature and the interstitium
- does it really exist??? if so, needs replacement!
- large volumes avoid renal failure
- may precipitate ARDS
- leads to abd compartment syndrome
- probably doesn’t exist, ERAS leans towards restricted fluid administration
Hypovolemia contributes to what two things?
- inadequate tissue perfusion
- post op complications
S/S of Hypovolemia
- tachycardia lacks sensitivity and specificity and is NOT a good indication of volume status
- hypotension means hypoperfusion has already occurred
Volume Responsive
- fluids should be given when patients require augmentation of perfusion and are volume responsive
- if BP and HR come up/down after fluid challenge, they are RESPONSIVE (frank-starling)
Hypervolemia: Weight Gain
>10% of preop weight = 32% mortality rate
<10% = 10% mortality rate
Pulmonary Edema
- occurs when volume infused is >67cc/kg/hr
- Healthy Volunteers - fasted - 40 ml/kg/hr LR over 3 hours
- decreased FEV1 and FVC for 8 hours
- median weight gain of 0.85 kg 24 hours after bolus
Bowel Manipulation
- results in a 5-10% increase in weight at the anastamosis
Tissue Edema leads to….
impaired wound healing 2/2 decreased oxygen tension
- so if everything is swollen and blood/oxygen cells can’t get through the edematous cell membranes it causes probs w wound healing
Ideal Body Weight
When we replace fluid we want to replace the intravascular volume, we don’t need to hydrate the fat cells.
Euvolemia
- maintains physiological homeostatis (HR, BP)
- replace preop defecits (NPO = 1.4 cc/kg/hr)
- replace maintenance fluids throughout surgery (basal rate = 100mL/hr)
- replace surgical losses (EBL)
Fluid Maintenance Calculation
4:2:1 Rule IBW
NPO losses and maintenance (4:2:1 rule)
4cc(10kg) + 2cc(10kg) + 1cc/kg(>20kg)
1st 10 kg gets 4cc/kg, 2nd 10kg gets 2cc/kg, all other gets 1cc/kg
EBL Loss Replacement
3:1
3rd Space Loss Replacement
2-10 cc/kg/hr
Fluid Calc Visual
Issues with classic fluid calculations
- fasting patients don’t become hypovolemic (NPO after midnight)
- insensible losses increase with incision is false
- literature doesn’t support decrease in kidney failure with large volumes
- 3rd space doesn’t exist
Incisional Losses
0.5cc/kg/hr
small incision = 2cc/hour
medium = 8cc/hour
large = 32cc/hour
Fluid Goals
- optimize tissue perfusion
- optimize vascular volume, SV, oxygenation (GDFT)
- reduce m/m
- euvolemia
GDFT
- optimized fluid therapy to ensure adequate tissue perfusion, tissue oxygen delivery and cellular oxygenation
- prevent cell death and organ damage
How to optimize tissue perfusion:
- maintain appropriate intravascular volume
- maintain preload, maintain CO
- maintain adequate tissue BP
Frank-Starling Visual
PPV
- art line pulse pressure
- difference b/t systolic peak and diastolic bottom
- PP(max) taken at end inspiration
- PP(min) taken at end expiration
- PP(mean) = [PP(max)+PP(min)]/2
SPV
art-line SPV (same as PPV but you’re using systolic pressure)
- difference b/t highest SBP and lowest SBP readings
- SP at end inspiration
- SP at end expiration
SPV=SP(max) - SP(min)
Large PPV or SPV means what?
hypovolemia
- accurate tools for guidance of fluid management but rely on mechanical ventilation and art lines
Fluid Challenges
- test the functional reserve of the CV system
- can be repeated as long as the response is positive (increased BP by 10-15% after challenge increase CO and indicates success)
- no response means you’ve maxed the F-S curve and additional challenges will cause fluid overload
Fluid Challenge Effect on BP
- increase BP via increase CO 2/2 increased SV
- hypoperfusion 2/2 hypotension 2/2 hypovolemia
GDFT Outcomes
DUMC GDFT Protocol
- 250cc carbohydrate drink (Gatorade) 1hr before arrival
- infuse 3cc/kg/hr per IBW
- preop baseline SV assessment
- after incision give 250cc colloid bolus <15 min
- if SV increases >10% repeat bolus
- if SV increases <10% no further bolus
- record peak SV (new baseline)
- if hypotensive give phenylephrine 100-200 mcg bolus or infusion
- give additional colloid bolus when SV decreases 10% from peak SV
- repeat cycle
Hypotonic
- osmolality lower than plasma, poor expanders, distributes to all body compartments
- Na+ concentrate less than 130mEq/L = osmolarity <280 mOsm/L
ie: 0.45% NS
Isotonic
- osmolality close to extracellular osmolality of body, expands ECV
- Na+ concentration 130-155 mEq/L = osmolarity 280-310 mOsm/L
ie: LR, 0.9% NS
Hypertonic
osmolality higher than ECF, expands by mobilizing water from ICV
- Na+ concentration >155 mEq/L = osmolarity >310 mOsm/L
ie: 3% NS, mannitol
Crystalloids: Cost, Composition and Use
- NS
- LR
- D5W
- cost: 2$/bag
- move freely between intravascular and interstitial fluid compartments
- cheap, easy, no allergic reactions
- contain water, electrolytes and glucose
0.9% NS
– Isotonic and isosmotic to plasma Na + but less Cl-
– Large volumes result in mild hypernatremia and hyperchloremia (non-ion gap acidosis)
LR
– Intended to mimic composition of plasma better
– Has minimal amounts of electrolytes added and frequently some sort of buffer (lactate in LR)
Hypertonic 3% Saline
– Used for replacement in the case of hyponatremia
– Used to reduce cerebral swelling (just as effective as Mannitol)
- moves fluid from ICF to ECF
Glucose Containing Solutions
D5W, D5NS, D10W
– Used to replace glucose in pts who need the sugar – D10W is base for most parenteral nutrition formulas – D 50 W comes in 50cc syringes for treatment of acute hypoglycemic shock
– Glucose is rarely ever used as a standard maintenance IV fluid because patients rarely need the sugar. Outcomes of arrest patients are worse when given glucose containing solu;ons.
Colloids
- albumin
- hetastarch
- dextrans
Colloid Composition, Use, and Downsides
- contain large molecular weight protein or glucose polymer particles
- create an osmotic force that keeps water intravascular and stay intravascular longer than crystalloids
- downside: more expensive, allergic reacitons, cause osmotic diuresis and coagulopathies
- colloids not superior in recusitation or long term outcomes
- beneficial in pts who need volume support but would go into CHF w crystalloids
cost: $50-1000/L but can be givin in smaller amounts
Crystalloid T1/2
15 min
- one hour after giving 1L crystalloid, only 250cc remains in intravascular space (the other 750cc is EDEMA!)
- must keep giving to maintain hydration and BP
Osmolarity of Crystalloids
Hypotonic Osmolarity <280 mOsm/L
Na+ <130mEq/L, 0.45%NS
Isotonic 280-310 mOsm/L
Na+ 130-155 mEq/L, 0.9% NS or LR
Hypertonic >310 mOsm/L
Na+ >155mEq/L, 3% NS
What does current evidence suggest re: high risk patients and major surgical procedures?
these pts do better w GDFT plans aimed at maximizing CO and tissue oxygenation
Benefits of GDFT and ERAS
- morbidity rates for major surgical procedures like esophagectomy, pelvic exenteration, pancreatectomy, colectomy, gastrectomy, and liver resection range from 25% - 55%
- one postop complication = $6,400
- two = $12,800
- three = $43,000 (average $18k)
prevention saves moneY!!
What is the #1 determinant of decreased postop survival?
– Complications within 30 days postop is #1 determinant of decreased postop survival
– Complications decrease postop survival by 69%
ERAS Graphic
