Fluid therapy Flashcards
What percentage of body weight does water constitute in the adult dog or cat?
60%
What are the two major compartments of total body water distribution?
Intracellular and extracellular
What is the osmolarity of the intracellular and extracellular body compartments?
290 to 310 mOsm/L
What is the distribution of total body water between the extracellular and intracellular compartments?
What is the function of the Na+-K+/ATPase cell membrane protein?
Removes Na+ from the cell and transports K+ into the cell consuming ATP in the process
What is the major cation in the intracellular fluid?
K+
What are the major anions in the intracellular fluid?
PO4-2 and polyionic charges of the intracellular proteins
What is the primary cation of the extracellular fluid?
Na+
What are the major anions of the extracellular fluid?
Cl-, HCO3
What is the glycocalyx?
A negatively charged layer of glycoproteins and proteoglycans that creates part of the endothelial barrier
What determines oncotic pressure?
The ratio of proteins between the intravascular and interstitial space
What is the primary component of osmotic pressure?
Albumin
What is the maximum rate that sodium concentration can be increased or decreased in the blood?
Should not be increased by more than 0.5 mEq/h or decreased by more than 1 mEq/h.
What is the formula for determining the volume of replacement fluids required in a patient?
Body weight in kg x percent dehydration PLUS estimated ongoing losses PLUS maintenance
What formula can be used to estimate maintenance fluid requirements in a patient?
What are the physical examination findings in dehydrated patients (based on % dehydration)?
What are the factors that determine oxygen delivery to tissues (DO2)?
What is the result of insufficient DO2?
Conversion from aerobic to anaerobic metabolism and decreased ATP production. Compromise of NaK/ATPase pump leads to disruption of cell membrane and exposure of subendothelial collagent. This causes activation of platelets, the clotting cascade, fibrinolytic system, and bacterial translocation.
What is the goal of hypotensive resuscitation?
Mean arterial pressure of 60 mmHg or systolic BP of 90 mmHg
What are the key recommendations of the 2012 surviving sepsis guidelines?
Early quantitative resuscitation, early sample collection for C&S, administration of ABs within 1 hour, and early administration of norEpi as first line vasopressor
What are the current fluid rate recommendations for dogs and cats under anesthesia?
Dogs: 5 ml/kg
Cats: 3 ml/kg
What is an isotonic fluid?
A fluid with the same osmolarity as the extracellular space
What is a balanced fluid?
A fluid with similar electrolytes to the extracellular space
Is isotonic saline (0.9% NaCl) a balanced or unbalanced fluid?
Unbalanced - contains higher concentrations of Na+ (154 meq/L) and Cl- (154 meq/L) than normal plasma
During rapid equilibration of isotonic crystalloids, what percentage of fluids remain in the intravascular space after 20-30 mins?
25% remain in the vascular space, 75% redistributes to the interstitial space
What is the typical dose of replacement fluids used to maintain hydration?
2-4 ml/kg/hr
What is the most appropriate fluid for resuscitation of a surgical patient with head trauma?
0.9% NaCl - least likely to cause decreases in osmolarity and movement of water in the brain interstitium
What is the most appropriate fluid for patients with severe hyponatremia or hypernatremia?
Crystalloid fluid most closely matched to the patients sodium concentration to prevent rapid changes in osmolarity and central pontine myelinolysis or cerebral edema
What is the most appropriate fluid for a patient with hypochloremic metabolic alkalosis?
0.9% NaCl (highest concentration of Cl)
What is the most appropriate fluid for a patient with severe metabolic acidosis?
Crystalloid with a buffer agent (not NaCl as this is acidifying)
Is a maintenance solution hypotonic, isotonic or hypertonic?
Hypotonic - obligate fluid losses in the normal animal are hypotonic and low in sodium but contain relatively more potassium. Maintenance fluids are designed to replace these losses.
Should maintenance fluids be administered as a bolus?
No - can lead to a rapid decrease in osmolarity and subsequent cerebral edema.
How can free water by safely administered?
Combine with 5% dextrose to yield an osmolarity of 252 mOsm/L
What can occur when rates of hypertonic fluid administration exceed 1 ml/kg/min?
Activation of pulmonary C-fibers, resulting in vagally mediated hypotension, bradycardia, and bronchoconstriction
How long does intravascular volume expansion last following hypertonic fluid administration?
<30 minutes due to osmotic diuresis and rapid redistribution of sodium. Additional fluid therapy should be administered to maintain intravascular volume
What is the difference between the weight average or number average molecular weight when describing synthetic colloid solutions?
Weight average: arithmetic mean
Number average: median (more accurate).
Ratio of the weight and number average is known as the polydispersity index.
What is the most common type of synthetic colloid used in veterinary medicine?
Hydroxyethyl starches
Are high or low molecular weight colloids more likely to interfere with coagulation?
High
How do colloids affect coagulation?
They decrease factor VIII and vWF, impair platelet function, interfere with the stability of clots.
What should be monitored during synthetic colloid administration?
APTT, platelet count and function, and viscoelastic measurement of clotting
What dose of colloids can be administered to patients in hypovolemic shock not responsive to crystalloid therapy alone?
Dogs: 5-20 ml/kg
Cats: 2.5-10 ml/kg
What is acute normovolemic hemodilution?
Blood is collected immediately pre-operative and then replaced with colloids or 3 x volume of crystalloids. Blood lost during surgery is subsequently lower in protein and RBC levels and can be replaced with collected blood if needed.
NOTE: Expensive and minimally beneficial!
What is the rate of pRBC or FFP administration?
10-15 ml/kg
What is the rate of fresh whole blood administration?
20-25 ml/kg
What is the formula for blood transfusion in dogs and cats?
What are the components in fresh whole blood?
All clotting factors and platelets, although platelets are best used within 8-hours and are no longer present after 24-hours. Clotting factors are also non-functional after 24-hours (stored whole blood).
What is the typical hematocrit and storage time of PRBCs?
Hematocrit: 80%
Storage: Shelf life of 20 days at 4 degrees celsius. Extended to 35 days with additive solutions.
What are the advantages of PRBC administration?
Ready availability, low risk for volume overload, reduced exposure to plasma antigens.