Perioperative Fluid Management Flashcards
What are the goals of perioperative fluid management?
Provide appropriate amount of parental fluid to maintain adequate intravascular fluid volume, left ventricular filling pressure, CO, systemic BP, and O2 delivery to tissues
In the average adult, the extracellular fluid volume represents approximately ___ % of total body water.
33%
The major components of the extracellular compartment are:
Interstitial fluid and plasma volume
Blood volume at rest is normally distributed as __% arterial and __% venous
15
85
The primary gradient that helps maintains intravascular fluid may be best described as:
oncotic pressure
The recommended duration of preoperative fasting from clear liquids is:
2 hours
Approximately 20 to 40 minutes following parenteral administration of crystalloid solutions, ___ % of the crystalloid remains intravascular.
33%
Balanced salt solutions (LR, Plasma-lyte) in respect to sodium are (slightly hypotonic, isotonic, or slightly hypertonic).
slightly hypotonic
The buffer in LR is metabolized in vivo to generate:
bicarbonate
Which crystalloids are appropriate for diluting PRBCs?
Normal saline, plasma-lyte
Name 3 situations where normal saline is preferred over LR.
Brain injury
Hypochloremic metabolic acidosis
Hyponatremia
What is the 1/2 life of albumin under normal circumstances?
16 hours
What is the recommended max dose of Dextran 70 in the initial 24 hours?
How does it increase bleeding time (keep it simple)?
20ml/kg/day (in the first 24 hours), then 10ml/kg/day
Decreases platelet adhesiveness
Calculate fluid maintenance rate for a 15Kg patient.
10kg * 4ml/kg = 40
5kg * 2ml/kg = 10
50ml/hr maintenance fluid
What is the maintenance fluid rate for an 80kg pt?
120ml/hr
How is fluid deficit calculated?
Preoperative fluid deficit = Maintenance fluid rate x hours NPO
If your 80kg pt was NPO for 14 hours, what would his fluid deficit be?
1680 ml
80kg = 120ml/hr * 14 hr = 1680 ml
To address a patient’s fluid deficit, how much should be infused in the first hour? Second hour? Third hour?
50%
25%
25%
Why is dextrose solutions typically not used for volume maintenance during surgery?
Dextrose metabolized, leaving only water. The water can dilute other plasma substrates.
For every 1ml of blood loss, ___ ml of crystalloid can be given.
3ml
Define third spacing
Movement of extracellular fluid to the interstitial space, an area where the body cannot use fluid in the intravascular space to move O2 and other essential nutrients to tissues.
Under what conditions should fluids be restricted?
CHF ESRD Liver resection Pulmonary surgery patients Abdominal surgery
Soaked sponge holds __ ml of blood.
Soaked laparotomy pad holds __ to __ ml of blood.
10
100 to 150ml
How do you calculate estimated blood volume (EBV)?
EBV = 60-70ml/kg in adults * weight
80ml/kg in children
90ml/kg in infants
100ml/kg in infants
How do you calculated allowable blood loss (ABL)?
ABL = [EBV * (Hi - Hm)]/Hi
i.e. [4900 * (40-25)]/40
What is the most common cause of bleeding following a massive blood transfusion?
Dilutional thrombocytopenia
What is the only reason for blood transfusion?
To increase O2 carrying capacity
Why do males have more total body weight of water than females?
Increased adipose tissue in females (60% males vs 50% females)
Plasma volume is what percent of total body weight?
4% (20% of ECF, which is 20% of TBW)
Why may a transfusion of LR only temporarily increase blood volume intravascularly?
LR is slightly hypotonic. Infusing this will dilute intravascular volume of Na and plasma proteins, shifting excess water intracellularly and to interstitial space. This leaves less water intravascularly.
At what degree of hyponatremia do seizures occur?
<120
What are some EKG changes associated with hypokalemia?
flattened or inverted T wave
U wave
Prolonged QT interval
What electrolyte should be checked for patients who are going to receive an AV fistula?
Potassium. r/t renal failure
What are clinical manifestations of hypocalcemia?
parathesia confusion laryngeal stridor carpopedal spasm, masseter spasm seizure prolonged QT interval - decreased contractility
Hypercalcemia will lead to ____ QT intervals
shortened
If your patient is on a Mg drip, you need to (increase/decrease) your dose of rocuronium.
Decrease by 25-50%
Total body water weight is __% of total body weight.
Intracellular water weight is __% of total body weight.
Extracellular water weight is __% of total body weight.
Interstitial fluid is __% of ECF.
Plasma volume is __% of ECF.
60% 40% 20% 80% 20%
Plasma osmolarity formula
275-295 mOsm/L
Osmoreceptors located in the _____ control the release of ____.
hypothalamus, ADH.
It also controls thirst.
The normal blood osmolarity is ___ to ___ mOsm/L.
Hypotonic is less than ____, hypertonic is greater than ____.
275 to 295
350
At what level of hypokalemia would you cancel a case?
If it’s 3 or better, generally do the case.
Also need to consider if it’s an emergency or not.
In other words, need to consider a lot of factors when deciding whether to do the case.
Which electrolyte abnormality would one see with massive transfusions?
Hypocalcemia – look for prolonged QT interval, decreased neuromuscular conduction
List 3 primary factos in which relative precentage of water varies significantly:
Age
Gender
Adiposity
Which has higher oncotic pressure, plasma or interstitial fluid?
Plasma, by 20mmHg greater oncotic pressure
List various reasons for perioperative shifts in fluid balance:
Preoperative fasting
Vasodilation from general or regional anesthetic
Insensible losses from intraoperative surgical exposure
Fluid shift from surgical trauma and inflammation
Blood loss
Is NS hypo, iso, or hypertonic?
hypertonic, just slightly
When would D5W be used?
Pts on insulin.
Pt on TPN up to time of surgery.
Correct hypernatremia.
5% albumin contain what kind of viruses?
None, they are removed in the preparation.
What effect does albumin have on coagulation?
Minimal
Which dextran solution would be used to prevent thrombosis?
Dextran 40
T/F. Perioperative fluid strategies are set guidelines that need be followed exactly to ensure patient has adequate fluid resuscitation.
False. These guidelines were developed over 40 years ago. They are a good starting point but fluid resuscitation can be adjusted to patient response.
What can be done to help compensate for venodilation and cardiac depression caused by anesthesia?
Approximately 5-7ml/kg of BSS before or simultaneously with onset of anesthesia.
How much fluid may be lost in a bowel resection in addition to maintenance and deficit replacement?
4-6ml/kg/hr
Patients with acute anemia usually need a transfusion at HCT < ___. Patients with chronic anemia may tolerate Hgb concentrations of < ___.
< 21 %
< 7 g/dL. But transfuse when < 6g/dL
Muscle contains __% H2O, adipose contains ___%.
75, 10
Ideal body weight
Males
IBW (kg)=50 kg +2.3 kg for every inch over 5 feet
Females
IBW (kg)= 45.5 Kg + 2.3kg for very inch over 5 feet
Osmosis is the net movement of:
a) solutes across a semipermeable membrane
b) water across a semipermeable membrane
b
Diffusion is:
the random movement of individual molecules due to their kinetic energy
The Starling-Landis equate helps determine:
whether serum will stay in the blood vessel or leak out based on the forces exerted.
JV = Kf [(Pc - Pif) – σ [π p - π if)]
Describe forces causing capillary fluid movement.
Mean forces moving fluid outward:
- Mean capillary pressure
- Interstitial fluid colloid osmotic pressure
- Negative interstitial free fluid pressure
Mean forces moving fluid inward:
- Plasma colloid osmotic pressure
Slight outward force greater than inward
Hypernatremia can be caused by:
Excessive loss of H2O
Inadequate intake of H2O
Lack of ADH
Excessive intake of Na
Postpone if > 145-150 mEq/L
Hypernatremia should be corrected (quickly/slowly)
Slowly. Correct H2O deficit over 48 hours with D5W.
Most likely cause of hyponatremia in the OR.
TURP
Hypokalemia can be caused by:
shift from EC to IC
- insulin and B2 agonist
Vomiting, NG, diarrhea, succinylcholine?, diuresis (renal)
Decreased upatake
T/F. Renal failure is often associated with hyperkalemia?
true. up to 75% of cases
ECG changes in hyperkalemia:
Tall peaked T waves
widened QRS and loss of P wave
extremely wide QRS
Vfib
ECG changes in hypokalemia
flat, inverted T wave
Prominent U wave
Prolonged QT (due to U wave)
Sagging, slurred ST segment
Which pack of PRBCs have higher potassium levels, 2 days old or 2 months old?
2 months
How can hyperkalemia be treated?
Ca IV push Hyperventilation NaHCO3 if metabolic acidosis Beta agonist (albuterol, epi) Insulin/glucose gtt or (10 units, 30-50G)
Hypocalcemia caused by
hypoparathyroidism (surgical, idiopathic, endocrine) hypomagnesemia hyperphosphatemia Chelation with citrate ions (transfusion) Low albumin Acute pancreatitis Acute hyperventilation Infusion of citrated blood
Patients with hypocalcemia present with:
Parathesias Confusion Laryngeal stridor Carpopedal spasm, masseter spasm seizures Decreased cardiac contractility, prolonged QT interval
Look for Chvostek sign (tapping of facial nerve will contract eye, mouth, or nose) or Trousseal (BP cuff around arm will lead to carpopedal spasm)
Which has a higher concentration of calcium, Ca chloride or Ca gluconate?
Ca Chloride has 1.36 mEq/L versus Ca gluconate with 0.45 mEq/L
Hypercalcemia can be caused by
hyperparathyroidism some cancers chronic immobilization drug induced thiazide diuretics lithium adrenal insufficiency
Clinical manifestations of hypercalcemia
Hypertension
Shortened ST and QT interverals
Weakness
Vomiting
Polyuria, renal calculi, oliguria, renal failure
Change in mental status: irritable, confused, ataxia
How is hypercalcemia treated?
Saline diuresis Diuretics Check other electrolytes Dialysis Avoid acidosis It's better to correct preoperatively
Is the concentration of phosphorous greater in the EC or IC?
15% in IC, 0.1% in ECF. 85% in bone
Hyperphosphatemia will cause (hypo/hypercalcemia)?
Hypocalcemia
Hypomagnesemia is often associated with ___calcemia and ____kalemia
hypocalcemia, hypokalemia
Hypermagnesemia will cause what EKG changes?
Depressed cardiac conduction
Early - prolonged PR interval
Late - widened QRS
What are some clinical manifestations of hypermagnesemia?
Vasodilation Bradycardia Myocardial depression skeletal muscle weakness respiratory depression
