Chapter 5 Fluid Therapy Flashcards
What proportion of bodyweight does total body water make up?
What are the propiortions of intra vs extracellular fluid?
And of extracellular fluid, what proportion is plasma vs interstitial?
Total body water = 60% of bodyweight
Intracellular fluid = 2/3rds of total body water
Extracellular fluid (i.e. plasma and interstitial fluid) = 1/3 of total body water
Of extracellular fluid, 25% is plasma, 75% interstitial fluid.
What are the main intracellular cations and anions?
Intracellular cations:
K+
(And Mg2+ and Na+)
Intracellular anions:
PO42- (phosphate)
What are the main extracellular cations and anions?
Extracellular cations
Na+
Extracellular anions
Cl-
HCO3- (bicarb)
What are the guidelines for rehydrating patients with evidence of interstitial dehydration
% dehydration x BW(kg)
+
On-going losses
+
Maintenance
What is the formula for estimating daily fluid requirement?
70(BWkg)0.75
List physical exam characteristics for the following percentages of dehydration:
<5%
5-8%
8-10%
10-12%
>12%
What is meant by “hypotensive resuscitation” and in what situation is it recommended ?
Resuscitation to MAP of 60mmHg or systolic BP of 90mmHg - applicable in animals with uncontrollable bleeding (because aggressive ivft can worsen bleeding)
Human study found it may offer survival benefit
List 4 therapy recommendations from “surviving sepsis guidlines” (human)
- Early quantitative resuscitation during first 6 hours
- Abx administration within 1 hour of recognition of sepsis
- Early administration of norepinephrine as first choice vasopressor after ivft resuscitation
- Close monitoring of indices of perfusion
What is the osmolarity of plasma?
300mOsm/L
What is a balanced fluid
Contains electrolytes similar to those of extracellular space
What is an isotonic fluid
Isotonic crystalloid fluids does not significantly change the osmolarity of the vascular or extravascular (both interstitial and intracellular) space.
Fluid type shoudl be used in head trauma patients?
0.9% NaCl or hypertonic saline as least liekly to cause water movement into brain
What volume of hypertonic saline (7.5% NaCl) should be administered and how long do th effects last?
What is the osmolarity of 7.5% NaCl
4-6 ml/kg over 20 minutes
(Effects last approx 30 minutes therefore additional ivft necessary to maintain intravascular volume.)
Osmolarity of 7.5% NaCl 2400 mOsm/L
N.B. mannitol osmolarity about half that of hypertonic saline.
Below which rate must plasma sodium concentration be changed?
<0.5 mEq/L/hr
What ivft type is recommended in caes with hypochloraemic metabolic alkalosis (typically upper GI obstruction)
0.9% NaCl as has highest concentration of Cl. (
Also ‘acidifying’ as Cl supplementation will lead to reduced bicarb concentration.
What are the characteristics of a “maintenance fluid”
Hypotonic (as obligate fluid losses are hypotonic)
Contain more potassium (15-30 mEq/L)and less sodium (40-60 mEq/L) than replacement fluids
e.g. Plasma-Lyte or Normosol
What is a safe starting rate of D5W administration?
What is the osmolarity of D5W?
3.7 ml/kg/hr + monitor Na closely
252 mOsm/L
List X potential side effects of synthetic colloids
- Coagulation abnormalities (dereased factor VIII and vWf), impaired platelt funtion, interference with firbin clots
- Renal impairment
What are two formulae for calculating the volume of transfused pRBC necessary for desired rise in PCV?
(pRBC PCV approx 80%)?
1.5 x desired rise in PCV x BW(kg)
What is contained within fresh whole blood ?
Why is use of whole blood generally avoided?
RBCs, platelets (best administered within 8 hours), all clotting factors
Avoided due to cancerous and immunological effects
What % acute blood loss requires blood transfusion?
>20%
What is the dose of pRBCs or FFP?
10-15 ml/kg (if not calculated according to formulas!)
What is the shelf life of pRBCs?
20 days (35 by including additives)
What is contained in fresh frozen plasma?
And when does FFP become just FP? What is lost in FP (vs FFP)
Clotting factors, proteins (inc albumin and globulin).
FFP=frozen within 6 hours, stored
Frozen plasma no longer contains labile coag factors (vWf, V and VIII)
What does cryoprecipitate contain (4)?
- vWf
- Factor VIII
- Fibronectin
- Fibrinogen
What 3 blood products could be used in a patient with vWD, and which is most effective?
Cryoprecipitate (most effective)
FFP
Plasma from donor that has received desmopressin
Ho wmany dog erythrocytic antigens are there?
8
Which types of cats generally have A vs B blod types and what is their tolearbility to transfusion?
Moggies type A
Posh cats type B
Posh cats cant tolerate type A blood (have string naturally occuring anti-A antibodies) –> potentially fatal reaction. Type B blood in type A cat –> reduced RBC lifespan (usually 2d or so)
N.B cats also may have Mik antigen therefore always crossmatch cats if poss
At what temperature should whole blood or pRBC be kept?
4Cº
What is the size of the pores in the filter used for blood products?
170 micrometers (removed clots, larger red cells)
40 micrometer filters (fine) do exist - remove most platelets but become clogged quickly
List the two types of reaction to blood products:
What reactions are most common?
Immune mediated vs non-immune-mediated
Most common:
- Transfusion associated circulatory overload (TACO)
- Non-haemolytic febrile reactions
At what sodium concentration does cerebral oedema develop?
<120 mEq/L or decrease rates >0.5 mEq/L/H
What is the formula for calculating free water deficit?
Free water defecit (L) = 0.6 x BW X [(Napresent - Nadesired) - 1]
What proportion of total body potassium is contained intracellularly?
95%
What is the resting potential of a cell mambrane?
-90 mV
Why can potassiu be elevated with thrombosis?
Potassium released from platelets during clot formation
What are typical ECG changes with hyperkalaemia of the following levels?
- 7 - 6.0 mEq/L
- 0 - 8.5 mEq/L
>8.5 mEq/L
10.0 - 12.0 mEq/L
- 7 - 6.0 mEq/L: Spiked T waves. Shortening of QT interval
- 0 - 8.5 mEq/L: Prolonger PR interval. Wide QRS
>8.5 mEq/L: P wave disappears. Reduced R wave amplitued. Increase S-wave prominence
Sequential electrocardiographic (ECG) tracings from a cat with anuric renal failure, severe hyperkalemia, and metabolic acidosis before (top tracing), during (middle three tracings), and after (bottom tracing) hemodialysis. The top tracing (serum potassium concentration = 10.9 mEq/L) shows a slow heart rate or approximately 100 beats/min, a wide QRS complex, and no P-waves. As the potassium concentration decreases, the QRS complex duration decreases, the heart rate increases, and the T-waves become large and “tented.” The QRS complexes and T-waves normalize at a potassium concentration of 7.1 mEq/L, and P-waves reappear when the potassium concentration reaches 6.6 mEq/L.
What proportion of total body calcium exists in bone vs extracelluar/intracellular fluid?
99% in bone
1% in extracellul;ar and intracellular fluid (divided between ionized, protein bound and chelated)
Which 3 hormones regulate calcium levels?
Where is parathyroid hormone produced?
- Parathyroid hormone (–> inc calcium absorbtion from bone and kidney. Also Vit D activation in kidney –> increase GI calcium from GI).
- Produced by chief cells in parathyroid gland
- Vitamin D = cholecalciferol, active for = calcitriol (–> increased GI absorbtion of Ca)
- Calcitonin (–> reduces Ca by inhibiting bone resorbtion).
- Produced by C-cells in thyroid follicles
List 12 broad causes of hypercalcaemia
H - Hyperparathyroidism
A - Addison’s. Hypervitaminosis A (VitA –> osteoclastic activity)
R - Renal
D - Diet. Hypervitaminosis D
I - Infection (granulomatous disease). Idiopathic
O - Osteolytic disease
N - Neoplasia (most common ASAC, lymphoma, MM, mammary-/prostatic-carcinoma/SCC)
S - Spurious. Supplementation
What is Whipple’s triad?
- Clinical signs of hypoglycaemia
- Low BG
- Response to glucose administration
Where is insulin produced, specifically?
ß-cells of pancreas
Where is glucagon produced?
alpha-cells of pancreas
What two hormones are reponsible for trying to maintain adequate BG level during acute hypoglycaemia, and which two hormones during chronic hypoglycaemia
Acute hypoglycaemia:
- Glucagon
- Epinephrine
Chronic hypoglycaemia:
- Growth hormone
- Cortisol
Sepsis is thought to induce hypoglycaemia via a combination of factors, list two:
- Increased cytokine levels (–> increased tissue glucose use)
- Reduced hepatic responsiveness to counter-regulatory hormones –> heatic glucose production
What would you administer in hypoglycaemia patient?
0.5 g/kg Dextrose (diluted 1:4)
(Care in insulinoma or other abnormal insulin production: glucose may –> further insulin release!)
List two mechanisms by which hyperglycaemia –> reduced cellular hydration
- Osmotic force draws fluid out of cells (glucose does not readily diffuse across cell membrane)
- Glucose spills over into urine –> osmotic diuresis
What is the Henderson-Hasselbalch equation?
pH = pKa + (log[A-]/[HA])
What is a strong acid vs a weak acid?
Strong acid completely dissociates into ions in water, weak acid only partially dissociates
What is normal base excess
-4 to +4 mEq/L
What are the 6 anions and 5 cations in tdog and cat blood?
Anions:
- Chloride
- Bicarb
- Protein
- Organic acid
- Phosphates
- Sulfates
Cations:
- Potassium
- Sodium
- Magnesium
- Calcium
- Trace elements
What are the four steps in interpreting the results for an acid/base disorder?
- Is an acid-base disturbance present? Evaluation of blood pH before any other values on the blood gas analysis will answer the question of whether an acid-base disturbance is present. If the value is normal (7.40), a mixed disturbance may still be present, so [HCO3−] and PaCO2 should also be normal if no acid-base disturbance is present.
- What is the primary disturbance?After first establishing whether alkalosis or acidosis is present, one can use the Henderson-Hasselbalch equation (pH = pKa + log [HCO3−]/[CO2]) to identify the primary disorder. If the primary disorder is metabolic in origin, the change in [HCO3−] should be consistent with the change in pH. For example, if the blood pH is low (acidemia), the [HCO3−] should also be low for a metabolic acidosis to be the primary disorder. If [HCO3−] is high in a patient with acidemia, and PaCO2 is also high, the primary disturbance is a respiratory acidosis, and the change in [HCO3−] may be a compensatory response (if appropriate, see the next question), or a mixed disturbance may be present.
- Is the compensatory response appropriate? Once the primary disturbance has been identified, the secondary compensatory response should be evaluated to determine whether the compensatory response is appropriate. If the compensatory response exceeds or falls short of the expected response, a mixed disorder may be present. For example, if the primary disturbance is a metabolic acidosis with a [HCO3−] of 14 mEq/L (10 mEq/L below normal), the expected respiratory compensation would be a 0.7 mm Hg decrease in PaCO2 for every 1 mEq/L decrease in [HCO3−], or 7 mm Hg in this case, so the expected PaCO2 should be 33 mm Hg (the normal PaCO2 of 40 mm Hg minus the compensation of 7 mm Hg). If PaCO2is 23 mm Hg instead, then a mixed disturbance (metabolic acidosis and respiratory alkalosis) is present.
- What underlying disease processes are present? Once the blood gas analysis is correctly interpreted, the list of potential causes of the disturbance(s) should be examined and correlated with the patient’s clinical picture. Correct interpretation of the acid-base balance in a given patient will significantly aid the clinician in narrowing down possible underlying disease processes and formulating appropriate diagnostic and therapeutic strategies.
What is the appropriate level of compensatory response in respiratory acidosis, resporatory alkalosis, metabolic acidosis and metabolic alkalosis?
What is the formula for calculation dose of bicarb necessary to return bese deficit to zero?
What is the typical difference on PaCO2 vs PvCO2?
PvCO2 typically 4-6 mmHg higher
At what bilirubin level is clinical icterus observed?
>25 umol/L
