Chapter 24 – Principles of Acid-Base Balance: Fluid and Electrolyte Therapy – Flashcards
129 test answers
Unlock all answers in this set
Unlock answers 129question
What is milliequivalent per liter (mEq/l)?
answer
= mmol/l x valence
Unlock the answer
question
Solutes exert an osmotic effect in solution that is dependent only on what?
answer
the number of particles in a solution and not on the molecular weight or valence
Unlock the answer
question
What does osmolarity refer to?
answer
the number of osmoles per liter
Unlock the answer
question
What does osmolality indicate?
answer
the number of osmoles per kg
Unlock the answer
question
The effective osmolality, or tonicity, of a solution is related to what?
answer
the ability of a solute to attract water and to sustain an increase in osmotic pressure as a result of water movement
Unlock the answer
question
What is the approximate percentage of total body water (TBW)?
answer
60%
Unlock the answer
question
Total body water is broadly divided into what two types?
answer
intracellular and extracellular
Unlock the answer
question
The extracellular fluid is divided into what four subcompartments?
answer
plasma volume, interstitial lymph fluid, transcellular fluid, and fluid present in dense connective tissue and bone
Unlock the answer
question
Where is transcellular fluid found?
answer
in diverse locations including CSF, pleural cavity, GI tract, bladder, synovia, aqueous humor, and peritoneal cavity
Unlock the answer
question
What is the most abundant and osmotically active ECF cation?
answer
Na+
Unlock the answer
question
What is the most abundant ICF cation?
answer
K+
Unlock the answer
question
Which ion is the major determinant of the resting cell membrane potential (-70 to -90 mV)?
answer
K+
Unlock the answer
question
The critical distribution of water between the plasma and the interstitium is maintained by what?
answer
the colloidal osmotic pressure of plasma protein (oncotic pressure)
Unlock the answer
question
What must occur to maintain electroneutrality?
answer
the number of cations in the ECF must equal the number of anions
Unlock the answer
question
Calculation of the difference between the commonly measured cations and anions in ECF yields what?
answer
the anion gap
Unlock the answer
question
The anion gap calculation can be useful in assessing what?
answer
the etiology of metabolic acidosis
Unlock the answer
question
What is water turnover?
answer
the term used to describe input and output of body water over a given period of time
Unlock the answer
question
Water turnover in mature dogs is approximated at what?
answer
40-60 ml/kg/day
Unlock the answer
question
What are maintenance fluids defined as?
answer
as the volume of fluid required daily to maintain an animal in zero fluid balance - no net gain or loss of water
Unlock the answer
question
What happens if ECF volume and renal perfusion decrease?
answer
renin will be secreted into the circulation
Unlock the answer
question
What is thirst stimulated by?
answer
plasma hypertonicity and/or contracted ECF volume
Unlock the answer
question
What is the rate limiting step in the renin-angiotensin system?
answer
conversion of angiotensinogen to angiotensin I
Unlock the answer
question
What does angiotensin II stimulate?
answer
the zona glomerulosa of the adrenal cortex to secrete aldosterone which causes increased reabsorption of sodium from the distal nephron with excretion of K+ and H+
Unlock the answer
question
In regards to normal water loss, what are sensible losses?
answer
water loss that occurs via urine, fecal water, and saliva
Unlock the answer
question
In regards to normal water loss, what are insensible losses?
answer
water loss that occurs via evaporation from cutaneous and respiratory epithelia
Unlock the answer
question
In a healthy animal, insensible losses account for TBW elimination of about what?
answer
15-30 ml/kg/day
Unlock the answer
question
Metabolic rate is directly proportional to what?
answer
the ratio of body surface area to total volume
Unlock the answer
question
Daily urinary water losses can be divided into what two groups?
answer
obligatory water loss and free water loss
Unlock the answer
question
What is obligatory water loss?
answer
water eliminated in order to excrete the daily renal solute load (urea, Na+, K+, Ca++, Mg++, NH4+, Cl-, SO4^2-, PO4^3- and other cations/anions)
Unlock the answer
question
What is free water loss?
answer
water excreted unaccompanied by solute
Unlock the answer
question
Free water loss is controlled by what?
answer
vasopressin
Unlock the answer
question
When does free water loss increase and decrease?
answer
it increases during relative water excess or hypotonicity and decreases during water deficit or hypertonicity
Unlock the answer
question
What part of the nephron is responsive to vasopressin?
answer
the collecting ducts
Unlock the answer
question
Renal reabsorption of sodium in the distal nephron is increased by what?
answer
aldosterone
Unlock the answer
question
What are the three categories of dehydration?
answer
hypertonic, isotonic and hypotonic
Unlock the answer
question
Causes of dehydration associated with pure water deficit include what?
answer
hypodypsia due to neurologic disease, diabetes insipidus, respiratory losses during exposure to elevated temperatures, fever and inadequate access to water
Unlock the answer
question
What is third spacing?
answer
a term used to describe extravasation of fluid from the vascular compartment into extravascular spaces
Unlock the answer
question
What has been included as a guideline for assessment of dehydration in neonatal calves?
answer
the measured gap between the eyeball and orbit
Unlock the answer
question
What factors are used when assessing dehydration?
answer
extent of exophthalmos, skin-tent duration on neck, thorax, and upper and lower eyelids, heart rate, mean central venous pressure, peripheral (extremities) and core temperatures, PCV, and hemoglobin and plasma protein concentration
Unlock the answer
question
What is sodium essential for?
answer
proper maintenance of membrane potentials, initiation of action potentials, and maintenance of acid-base balance
Unlock the answer
question
What are the clinical signs of hypernatremia?
answer
neurologic deficits, thirst, anorexia, lethargy, vomiting and muscle weakness; dehydration may be present
Unlock the answer
question
With hypernatremia, in the case of pure-water loss, what can the volume be replaced with?
answer
5% dextrose in water over a 48- to 72- hour period
Unlock the answer
question
What is the treatment for hyponatremia?
answer
infusion with conventional crystalloid solutions
Unlock the answer
question
When can cause hyperchloremia?
answer
fluid loss associated with small bowel diarrhea
Unlock the answer
question
What can cause hypochloremia?
answer
fluid losses due to vomiting or excessive diuretic administration
Unlock the answer
question
What is the treatment for chloride-responsive alkalosis?
answer
chloride-replete fluid such as normal saline
Unlock the answer
question
What is the primary determinant of potassium secretion across renal tubular epithelial surfaces?
answer
aldosterone
Unlock the answer
question
Most of the filtered potasium is reabsorbed where?
answer
in the proximal tubule
Unlock the answer
question
Tubular secretion of potassium is aldosterone mediated and occurs where?
answer
in the distal nephron
Unlock the answer
question
What does hypokalemia do to the resting membrane potential?
answer
makes it more negative thereby hyperpolarizing the cell
Unlock the answer
question
What does hyperkalemia due to the cell
answer
makes it more positive causing hyperexcitability
Unlock the answer
question
What can affect the distribution of potassium between the ICF and the ECF?
answer
changes in pH
Unlock the answer
question
What is the rule of thumb regarding pH and serum potassium concentration?
answer
every 0.1 unit decrease in pH will be accompanied by a 0.6 mEq/l increase in serum potassium concentration
Unlock the answer
question
What are some of the clinical signs of hyperkalemia?
answer
muscle weakness, twitching, and irritability
Unlock the answer
question
How might ACE inhibitors cause hyperkalemia?
answer
by interfering with angiotensin II-mediated aldosterone secretion
Unlock the answer
question
Emergency treatment is indicated if potassium rises and exceeds what?
answer
6.0-8.0 mEq/l
Unlock the answer
question
What is the therapy for hyperkalemia?
answer
calcium gluconate
Unlock the answer
question
What are the clinical signs of hypokalemia?
answer
weakness of skeletal and respiratory muscles and intestinal smooth muscle loss of tone
Unlock the answer
question
What is feline hypokalemic polymyopathy syndrome often manifested as?
answer
ventroflexion of the head and a stiff, stilted gait
Unlock the answer
question
Administration of intravenous potassium should not exceed a rate of what?
answer
0.5 mEq/kg/hr
Unlock the answer
question
What is responsible for the maintenance of body pH?
answer
pulmonary and renal control of dissolved CO2 and bicarbonate concentrations
Unlock the answer
question
Under normal physiological conditions, what is the ratio of HCO3- to dissolved CO2?
answer
20:1
Unlock the answer
question
The respiratory component of acid-base regulation involves changes in what?
answer
respiratory rate and volume prompted by changes in PCO2
Unlock the answer
question
The renal component of acid-base regulation involves what?
answer
selective absorption of bicarbonate and secretion of H+
Unlock the answer
question
What happens during acidosis?
answer
more H+ are secreted while more K+, Na+ and HCO3- are retained
Unlock the answer
question
What happens during alkalosis?
answer
K+ is secreted while more H+ and less Na+ and HCO3- are retained
Unlock the answer
question
How do the kidney's regulate acid-base balance?
answer
by maintaining the appropriate HCO3- in the plasma
Unlock the answer
question
Disorders of acid-base equilibrium can result from what?
answer
a primary disturbance in pulmonary regulation of the concentration of H2CO3 in body fluids via changes in alveolar ventilation and PCO2 levels, from metabolic changes in concentration of bicarbonate or from a combination of these mechanisms
Unlock the answer
question
What is the best measure of respiratory disturbances?
answer
the partial pressure of CO2
Unlock the answer
question
What does a blood gas analysis provide?
answer
three measured parameters (pH, PCO2, PO2) and two calculated values (actual bicarbonate and base excess)
Unlock the answer
question
Actual bicarbonate values are useful in assessment of what?
answer
non-respiratory disorders
Unlock the answer
question
What is the approximate normal anion gap in dogs and cats?
answer
13-24 mEq/l
Unlock the answer
question
What is the anion gap often used to identify?
answer
causes of metabolic acidosis
Unlock the answer
question
Increased anion gap often occurs in what?
answer
lactic acidosis, diabetic ketoacidosis, azotemic renal failure and poisoning
Unlock the answer
question
A normal anion gap usually occurs in what?
answer
metabolic acidosis related to diarrhea, renal tubular acidosis, excessive use of carbonic anhydrase inhibitors or ammonium chloride administration and in iatrogenic expansion acidosis caused by excessive normal saline administration
Unlock the answer
question
What is an acid-base disturbance?
answer
a primary disturbance with a secondary or compensatory response
Unlock the answer
question
Metabolic acidosis may be characterized by what?
answer
a decrease in plasma HCO3- concentration, decreased pH, increased concentration of strong anions and decreased plasma sodium concentration associated with renal disease or diarrhea
Unlock the answer
question
What are the clinical signs most associated with metabolic acidosis?
answer
hyperpnea and CNS depression
Unlock the answer
question
Laboratory evaluation of blood and urine reveals what with a metabolic acidosis?
answer
a lowered urine and blood pH and a decreased serum HCO3-
Unlock the answer
question
What is the most common acid-base disorder in dogs, cats and horses?
answer
metabolic acidosis
Unlock the answer
question
What is the most common cause of normal anion gap (hyperchloremic) metabolic acidosis?
answer
loss of Na+ and HCO3- associated with diarrhea
Unlock the answer
question
What is metabolic alkalosis characterized by?
answer
an excess of HCO3- caused by a deficit of H+ in the ECF
Unlock the answer
question
What can metabolic alkalosis be caused by?
answer
excessive vomiting, excessive alkaline therapy or use of diuretics
Unlock the answer
question
What are the clinical signs of metabolic alkalosis?
answer
depressed breathing (slow and shallow), nervous excitement, including tetany, and even convulsions and muscular hypertonicity
Unlock the answer
question
Compensation for metabolic alkalosis requires what?
answer
the kidneys to excrete HCO3- and retain H+
Unlock the answer
question
What does respiratory acidosis involve?
answer
retention of CO2 as a consequence of alveolar hypoventilation
Unlock the answer
question
What does hypoventilation result in?
answer
CO2 retention, an excess of H2CO3 and thereby an excess of H+
Unlock the answer
question
What is the compensatory mechanism for respiratory acidosis?
answer
for the kidneys to conserve HCO3- and excrete H+
Unlock the answer
question
The most important treatment for respiratory acidosis is what?
answer
proper ventilation of the animal
Unlock the answer
question
What is the purpose of fluid and electrolyte therapy?
answer
to correct dehydration or overhydration and electrolyte imbalance and/or acid-base imbalance
Unlock the answer
question
What provides a rational basis for estimating patient fluid and electrolyte needs and monitoring treatment success?
answer
laboratory examination of the blood in combination with clinical signs
Unlock the answer
question
What happens to specific gravity and urine volume during a state of dehydration?
answer
specific gravity increase and urine volume decrease
Unlock the answer
question
If the specific gravity is unchanged or lowered and the animal shows clinical signs of dehydration, what does this typically mean?
answer
the kidneys are not functioning properly
Unlock the answer
question
What are the three aims of volume replacement?
answer
correct existing deficits, satisfy maintenance needs and replace continuing loss
Unlock the answer
question
What is the replacement volume equation?
answer
replacement volume = body weight (kg) x % dehydration
Unlock the answer
question
When are maintenance fluids needed?
answer
when a patient does not voluntarily ingest sufficient food and water to replace normal losses occurring via urine, feces, respiratory tract and skin
Unlock the answer
question
What is the rule of thumb for giving fluids for mature and immature animals?
answer
mature: 40-65 ml/kg/24 hour immature: 130 ml/kg/24 hour
Unlock the answer
question
In less severe cases of dehydration, what should the infusion rate of fluids be?
answer
15-30 ml/kg/hr
Unlock the answer
question
Large volumes of fluid administered too rapidly may overload the circulatory system, causing what?
answer
pulmonary edema and even death, especially in severely ill or toxic cases
Unlock the answer
question
What is hypodermoclysis?
answer
subcutaneous administration of fluid
Unlock the answer
question
What are the major categories of parenteral fluids?
answer
crystalloids, colloids, blood replacements and nutritional solutions
Unlock the answer
question
What are the fluids going to be like that closely resemble the ECF?
answer
isotonic, high in sodium, low in potassium, and may be acidifying or alkalinizing
Unlock the answer
question
What is the fluid of choice for treatment of diabetic ketoacidosis?
answer
normal saline
Unlock the answer
question
What are the fluids of choice for metabolic alkalosis?
answer
normal saline and Ringer's solution
Unlock the answer
question
What are the two types of colloids?
answer
natural and synthetic
Unlock the answer
question
What are the natural colloids?
answer
whole blood, plasma, and albumin
Unlock the answer
question
What are the synthetic colloids?
answer
dextran 40, dextran 70, hetastarch, pentastarch and oxypolygelatin
Unlock the answer
question
Which type of fluid contain large particles and are retained within the vascular space more readily?
answer
colloids
Unlock the answer
question
Initial tissue perfusion has been found to be better after volume expansion with what type of fluids?
answer
colloids or combination of crystalloids and colloids
Unlock the answer
question
What are the indications for colloid use?
answer
perfusion deficits, hypooncotic states, deficiency of blood components, and diseases that lead to systemic inflammatory response syndrome (SIRS)
Unlock the answer
question
What are the hallmarks of SIRS?
answer
alterations in temperature, heart rate, respiratory rate, PCO2 and white blood cell count
Unlock the answer
question
What are the three major categories of synthetic colloids?
answer
dextrans, hydroxyethyl starches and gelatins
Unlock the answer
question
What are dextrans prepared from?
answer
a macromolecular polysaccharide produced by bacterial fermentatino of sucrose
Unlock the answer
question
What are hydroxyethyl starches derived from?
answer
plant amylopectin and are modified by hydroxyethylation to reduce hydrolysis by amylase
Unlock the answer
question
What is the most commonly used hydroxyethyl starch?
answer
hetastarch (Hespan)
Unlock the answer
question
What is the only approved plasma substitute in the U.S. for fluid resuscitation?
answer
oxypolygelatin (Vetaplasma) derived from bovine bone gelatin
Unlock the answer
question
Hypertonic saline is used in the treatment of what?
answer
shock associated with hemorrhage, trauma, GDV, acute pancreatitis, burns and sepsis
Unlock the answer
question
What does hypertonic saline do?
answer
draws interstitial and intracellular water away from edematous tissues and into the vasculature
Unlock the answer
question
As hypertonic saline is short-lived, what should be combined for long-term resuscitation?
answer
crystalloids or colloids
Unlock the answer
question
What are hemoglobin based oxygen carriers (HBOCs) useful for?
answer
replacing RBCs in anemic humans and animals
Unlock the answer
question
What do hemoglobin based oxygen carriers contain?
answer
purified hemoglobin, removed from RBCs and suspended in solution
Unlock the answer
question
What are hemoglobin based oxygen carriers developed from?
answer
animal or human hemoglobin
Unlock the answer
question
Does oxyglobin need to be cross-matched?
answer
no, it does not have the potential to transmit disease
Unlock the answer
question
What will grain overloading in ruminants cause?
answer
severe dehydration and metabolic acidosis
Unlock the answer
question
What can provide benefit to calves that have hypernatremia and diarrhea?
answer
5% dextrose alone or with isotonic sodium bicarbonate
Unlock the answer
