Chapter 3 - Fluids, Electrolytes and acid-base Flashcards
What percentage of body weight does total body water (TBW) represent in adult horses?
60%
What percentage of body weight does total body water (TBW) represent in foals?
70%
What proportion of TBW does the extracellular fluid (ECF) volume represent in adult horses?
One third (20% of the BW)
Which component forms the largest part of the ECF?
Interstitial fluid (two thirds, 40% of BW)
What is the normal volume of gastrointestinal secretion in a 500-kg horse?
About 100 L every 24 hours
What is the blood volume in fit horses as a percentage of body weight?
14%
What is the normalblood volume as a percentage of body weight in sedentary horses?
8% in sedentary and 14% in sport horses
In neonates, blood volume represents what percentage of body weight?
15%
What is the osmotic pressure generated mainly by proteins in the plasma called?
Colloid osmotic pressure (COP)
The ECF is composed by what?
interstitial fluid (75%),
plasma (25%) lymph,
transcellular fluids such as synovial, pleural, abdominal, and cerebrospinal fluids (<1%).
The overall concentrations of anions and cations have to be ____________ in all fluids
The overall concentrations of anions and cations have to be equal in all fluids, including plasma (sum of all anions = sum of all cations)
In plasma what is the main anion and the main cation
In plasma, sodium is the main cation and chloride the main anion
n plasma what is the main anion and the main anion
bicarbonate and chloride are the main anions
Proteins have positve or negative charge?
Proteins have a negative charge and contribute
to the anions.
The interstitial fluid accounts for ___% of the ECF
The interstitial fluid accounts for about 75% of the ECF, and the components with significant concentrations
are sodium, bicarbonate, and chloride
The composition of Ions the ICF
the important cations are potassium and magnesium, and the important anions are phosphates and proteins
Definitation of osmolality
Osmolality is defined as the concentration of osmotically active particles in solution per kilogram of solvent (mOsm/kg)
definition of osmolarity
is the number
of particles of solute per liter of solvent (mOsm/L)
Normal plasma
osmolality
from 275 to 312 mOsm/kg
what is the Starling’s equation?
**Kf **is the filtration coefficient, which varies depending on the surface available for filtration and the permeability of the capillary wall; **Pcap and Pint **represent the hydrostatic pressures in the capillary bed and in the interstitial compartment, respectively;
πp and πint represent the oncotic pressure in the plasma and interstitial fluid, respectively; and σ is the reflection coefficient of proteins across the capillary wall
**Kf ** is the filtration coefficient, which varies depending on the
depending on the surface available for filtration and the permeability of the capillary wall
what Pcap and Pint
Pcap and Pint represent the hydrostatic pressures in the capillary bed and in the interstitial compartment, respectively;
Colloid osmotic pressure
(COP) is generated mainly by
proteins, albumin
What is the normal COP for foals and adults?
Normal values of 15.0 to 22.6 mm Hg for foals
Normal values of 19.2 to 31.3 mm Hgfor adults
Henderson-Hasselbalch equation - What does the traditional approach to determine acid-base and electrolyte status focus on?
Bicarbonate and hydrogen ions
Stewart’s definition what is the definition of base?
a substance that can accept H (Bronsted)
result in a decrease of H+in the fluid (Stewart),
Stewart’s definition what is the definition of acid
a substance that can donate H (Bronsted)
result in an H+ increase in a fluid (Stewart)
which voltatile acid exist?
volatile acid (CO2)
what other acids exist beside the CO2?
lactate
acetate
pyruvate
citrate
Henderson-Hasselbalch approach centers on what to determine if it is metabolic or respiratory?
centers on pH, bicarbonate and CO2
What is the formula of law of mass with dissociation of carbonic acid?
Name the Henderson-Hasselbalch equation
Name causes of metabolic acidosis and what does it mean
Metabolic acidosis is present when there is a decrease in HCO3− caused by either loss or buffering of nonvolatile acids
what does it mean to have metabolic alkalosis
Metabolic alkalosis is present when there is an increased concentration of HCO3
what are the reasons of respiratory acidosis
what are the reasons of respiratory alkalosis
The major route for return of fluid to the circulation is
lymph
Why focusing only on pH as sole determinant of acid-base homeostasis is not sufficient?
because pH can be normal and electrolytes are ignored using traditional approach
What challenge did Peter Stewart present to the traditional approach to acid-base balance?
Emphasized the role of strong ions and weak electrolytes (Quantative Strong ion approach)
3 parameters PCO2, SID and total proteins (Atot)
What is an increase in the strong ion difference (SID) indicative of?
Metabolic alkalosis
What does Atot represent in the quantitative strong ion approach?
Total mass of nonvolatile weak acids (proteins)
What is the effect of a significant increase in Atot?
Metabolic acidosis
What are the strong cations mentioned in the Stewart quantative strong ion approach?
Na+, K+, Mg++, and Ca++
What is the primary buffer system of the extracellular fluid (ECF)?
Bicarbonate
What is considered the primary respiratory component in the quantitative strong ion approach?
Carbon dioxide partial pressure (pCO2)
What happens when the strong ion difference (SID) decreases?
Metabolic acidosis
What results from a significant decrease in Atot (weak acids)?
Metabolic alkalosis
What are weak acids primarily comprised
Proteins and phosphates
In the quantitative strong ion approach, what are HCO3− and H+ considered as?
Dependent variables
What does blood gas analysis typically measure?
pH, pCO2, and pO2
what are the strong anions
Cl, lactate, sulfate, ketoacids, uremic acids
what are the main ions present in high concentrations that are taken into consideration for SID calculation?
Cl−, K+, and Na+
Quantative strong ion approach
For accurate blood gas analysis appropriate sampling with anticoagulant is needed. what anticoagulant is used?
usually lithium heparin,
What happens to pO2 and pCO2 at high body temperatures?
Both increase
What effect does placing blood on ice before analysis have?
Decreases cell metabolism
What is the base excess (BE) a measure of?
Metabolic acid-base disturbances
How is the pH value determined?
It’s the negative logarithm of H+ concentration
For traditional approach what do you evaluate?
If you evaluate the horse in quantitative strong approach what do you evaluate?
1 . check pCO2 is evaluated initially. If abnormal, a respiratory acidosis or alkalosis is present
2. Calculate SID. Common causes of low SID include hyponatremia, hypokalemia, hyperchloremia, and hyperlactatemia (Na + K − Cl) = A− (total protein × 0.2) = 16 mmol/L,
3. Determine Atot
4. Presence of unmeasured anions (L-lactate, D-lactate, ketoacids, uremic acids, sulfate)).
What is a high pCO2 level termed as?
Hypercapnia or hypercarbia
What does a venous blood sample typically show compared to an arterial sample?
Higher pCO2
What is tCO2 an indirect measurement of?
HCO3−
What is the first step in interpreting blood gases using the traditional approach?
Examine the pH
What indicates an acidemia in the traditional approach?
Increase in pCO2 or decrease in HCO3−
Anion Gap is often used in the traditional approach
represents the difference between the sum of the commonly measured cations and the sum of the commonly measured anions in serum,
what is the normal anion gap in adult horses?
A normal AG of 10.4 ± 1.2 mmol/L
Is there correlation btw AG (anion gap) and the lactate concentration?
yes, In horses with abdominal pain, the correlation between lactate concentration and the AG is excellent
Is the AG a good prognostic indicator of survival in horses with colic?
The AG (because of its correlation with lactate) is considered a good prognostic indicator of survival in horses with abdominal disorders
Strong Ion Gap or SID reflects the concentration of
measured ions (ie Chloride)
unmeasured anions can be quantified using the SIG (L-lactate, D-lactate, phosphate, sulfate, ketoacids)
The SIG is defined as (formula)
SIG similar to AG is a good predictor for
hyperlactemia cases
Basically the SID can correct the electrolyte and acid-base abnormalities using
Based on pCO2, SID, and total protein concentrations (Atot), and potentially the assessment of unmeasured anions (lactate), an integrative fluid plan can be developed to correct the electrolyte and acid-base abnormalities.
why lactate has to be immediately measured?
Samples should be analyzed immediately to prevent in vitro lactate production by erythrocytes
if you cannot run the sample of blood to analyse the lactate immediately, what can you do to avoid changment in the value?
fluoride-containing tubes,
storage on ice,
separation of plasma
Lactate is the end product of
anaerobic glycolysis, and its concentration is another indicator of tissue perfusion and oxygen delivery
Neonates have higher blood lactate concentrations that decrease to adult values by 24 hours of age. TRUE or FALSE?
TRUE
what are the 2 most common used IV fluids?
Crystalloids or balanced electrolyte solutions (BES) are the most commonly used intravenous replacement fluids.
what is the maintenance fluid requirements?
60 mL/kg/day
2.5 mL/kg/h
very important
What is the formula to estimate the L of dehydration?
what are the negative effects of fluid overload?
interstitial tissue edema,
gastrointestinal motility disturbances,
acute respiratory distress syndrome,
abdominal compartment syndrome,
delayed wound healing,
and increased mortality.
What are the 2 tyoes of crystalloids commonly used for fluid replacement?
0.9% NaCl (saline) and BES.
Which type of fluid is chosen when the electrolytes are close to normal?
BES are chosen when serum electrolytes are close to normal
BES contains lactate, or acetate plus gluconate
contains K+, Ca2+, or Mg2+
Saline is higher in Na+ and much higher in Cl− than serum concentrations and is only indicated if
acute hyponatremia is present (Na+ <125 mmol/L for 24 hours or less severe hypochloremia relative to hyponatremia (i.e., in a patient with large volumes of gastric reflux
it has a pH of 5 NOT RECOMMENDED in cases of metabolic acidosis
NaCl is contra-indicated in which cases?
Cases of blader rupture
Metabolic acidosis
it is preferable to determine ionized concentrations or Total Mg2+ and tCa2+?
Total Mg2+ and tCa2+ concentrations are less reliable for identification of Mg2+ and Ca2+status—it is preferable to determine ionized concentrations
The calcium values can be misleading in 2 situations, name them
Measurement of tCa2+ can be misleading if TP is low (ionized calcium may still be normal) or if the horse is alkalotic (tCa2+ may be normal, with a low ionized fraction).
How much calcium should you give o a horse?
Administration of 50 to 100 mL of 23% calcium gluconate in every 5 L of fluid
severe hypocalcemia (iCa <4.0 mg/dL), administration of 500 mL of calcium gluconate in 5 L of BES is indicated.
In which cases can you give the all bottle of 500 mL calcium gluconate?
In the presence of severe hypocalcemia (iCa <4.0 mg/dL), administration of 500 mL of calcium gluconate in 5 L of BES is indicated.
what should you suspect if a horse is refractory to the treatment of calcemia?
Hypocalcemia that is refractory to calcium therapy may indicate hypomagnesemia, and concurrent magnesium replacement is required
what are the maintenance requirement of magnesium in horses?
13 mg/kg/day of elemental Mg2+, which is provided by 31 mg/kg/day of MgO, 64 mg/kg/day of MgCO3, or 93 mg/kg/day of MgSO4.
what the maximum velocity a horse can receive of potassium?
patients receive K+ no faster than 0.5 mmol/kg/hr (use a pump)
20 mmol of K+ in the form of potassium chloride/liter of fluids.
what are the causes of hypokalemia?
may develop because of lack of intake, diuresis, and gastrointestinal loss through diarrhea
Which case you should supplement with bicarb?
- acute severe metabolic acidosis (pH<7.2)
- normal respiratory function
- hyponatremia
- The blood pH should be less than 7.2. In acute acidosis associated with dehydration (lactic acidosis), fluid replacement using isotonic crystalloids (e.g., lactated Ringer) will result in clearance of lactate and improved tissue oxygenation and perfusion, resulting in reduced production of lactate; use of NaHCO3 is not indicated.
- half calculated amount should be given quick and rest over 12 to 24 hours
- IV Na-bicarbonate should not ge given with Ca+ containing solutions
what are the 2 formulas to calculate the bicarbonate required
foasl is 0.6 instead 0.3
what are the forms of bicarbonate available commercially?
injectable solution in two concentrations: a 5% solution, which contains 0.59 mmol/mL of HCO3− and 0.59 mmol/mL of Na+, and an 8.4% solution, which contains 1 mmol/mL of HCO3− and 1 mmol/mL of Na+.
isotonic solution for intravenous administration, 1 part of 5% Na-HCO3− can be diluted in 3 parts of sterile water
150 mL of 8.4% Na-HCO3− can be added to 850 mL of sterile water.
HCO3− can be given orally as a powder (baking soda), where 1 g NaHCO3 = 12 mmol HCO3−
what are the conditions to wich is advised to give dextrose? name 3
hypertonic dehydration in patients that are hyperkalemic
hyperlipemia (miniature horses and donkeys, adult horses with azotemia),
pregnant mares as a source of energy for the fetoplacental unit.
what happens when patients have hyperkalemia and you give glucose?
Glucose (alone or in combination with insulin) is used to push K+ intracellularly in patients with hyperkalemia.
what is the dosage of dextrose?
rate of 1 to 4 mg/kg/min
rate infusion (CRI) using 20% to 50% dextrose solutions
or supplement the BES to make 2.5 to 5% solution
how many times have the hypertonic crystalloid fluids have the tonicity of plasma?
8 times the tonicity
what does the hypertonic, how does it distribute?
expand the vascular volume by redistribution of fluid from the interstitial and intracellular spaces
What is the recomended dose of hypertonic?
2-4 mL/kg (1-2L per 500kg horse) followed by isotonic crystalloid 2-4 mL/kg/hr
from which value are colloids indicated?
when the TP concentration is <40 g/L, the albumin concentration is <20 g/L, or the colloid oncotic pressure is <12 mm Hg
what types of plasma are commonly used?
Plasma and hydroxyethyl starches (HES) are commonly used colloids in horses. Comercial 10mg/kg/day
what is the dosage of synthetic colloid?
dosage of 10 mL/kg/day.
what is the advised rate of fluids with clinical signs of shock?
20 mL/kg (10 L in a 500-kg horse) should be given rapidly (with the use of pressured bags or a pump) over 30 to 60 minutes monitor HR, mentation and urination and pass to
maintenance 2-4 mL/kg/hr over next 12 to 24h
how can you achieve a isotonic electrolyte solution ?
5.27 g of NaCl, 0.37 g of KCl, and 3.78 g of NaHCO3 per liter of tap water
how many fluids per day does the intubation allow?
intermittent intubation allows administration of approximately 60 L of fluids per day
usually not possible to administer more than 5 L every 2 hours
Thrombogenicity depends on
on the material used (polyethylene, Polypropylene, teflon, polyuretane, silastic)
Standard adult horse catheter sizes are usually
14 gauge in diameter and 13 cm
The rate of fluid flow is proportional to
diameter of the catheter and inversely proportional to the length of the catheter and the viscosity of the fluid
In case of shock which size catheter you should use?
12 to 10 gauge
Teflon catheters should be changed every
3 days
polyurethane catheters may remain in the vein for
2 weeks
Horses that are very ill (bacteremic, septicemic, endotoxic) are more likely to encounter catheter problems and benefit from what type of kt?
polyurethane or silicone catheters
name the common sites for intravenous catheters
jugular,
superficial thoracic,
cephalic,
saphenous veins.
what are the administration sets used?
10 drops/mL and 60 drops/mL
which catheter is the most thrombogenic?
polypropylene, polyethylene tubing
catheter is the less thrombogenic?
silastic
