Acid/Base/Fluid/Lyte Flashcards
Free water deficit calculation?
TBW x (serum Na / normal serum - 1)
Normal SID in dogs vs cats
dog: 27 mEq/L cat: 30 mEq/L
What toxins cause type B lactic acidosis?
cyanide ethanol ethylene glycol
For every 100 mg increase in glucose, sodium decreases by?
1.6 (pseudohyponatremia)
Myelinolysis lesions in dogs vs people?
dog: thalamus people: pons (hence “central pontine myelinolysis”)
Boag, JVIM, 2005. Dogs with linear FBs were more likely to have what e-lyte abnormality?
Hyponatremia. Study also found hypochloremic metabolic alkalosis found in most regardless of GI or jejunal FB. 25% hypokalemic
death and severe complications of hyponatremia typically occur when the serum Na concentration is less than what?
120 meq/L
what gradient of water between the plasma and brain in dogs can result in translocation of water between plasma and the brain in dogs?
30-35 mOsm/kg gradient
when hyponatremia is chronic, brain volume is adjusted toward normal via what mechanisms?
loss of potassium and organic osmolytes from cells
what are the clinical signs of acute water intoxication?
weakness, incoordination, and seizures
T/F- acute water intoxication likely occurs only if the patient has an underlying cause of impaired water excretion at the time of water load?
true
severe symptomatic hyponatremia of acute onset (clinical signs)
death, cerebral edema, seizures
what is the maximum recommended rate of correction of chronic hyponatremia?
>10-12 meq/L in 24 hrs
name the type of injury that occurs to the brain when chronic hyponatremia is corrected too quickly
demyelination or myelinolysis
where in the brain are lesions often found with demyelination from sodium correction?
pons, thalamus, subcortical white matter, cerebellum
list the MRI abnormalities associated with demyelination
hyperintense area on T2, hypointense on T1, not enhanced with contrast
list the clinical signs that have been reported & associated with myelinolysis?
lethargy, weakness, ataxia, progressing to hypermetria and quadriparesis, loss of CPs, dysphagia, trismus, decreased menace
What mechanism causes a hyponatremic patient to excrete solute-free water via the kidneys when they are volume resuscitated?
volume repletion in hypovolemic patients abolishes the nonosmotic stimulus for vasopressin release and allows the animal to excrete solute-free water via the kidneys- this itself tends to correct hyponatremia
in edematous hyponatremic patients, what treatments should be considered?
dietary sodium restriction, diuretic therapy or 0.9% NaCl in combination with a diuretic for rapid correction of hyponatremia
How do AVP receptor antagonists work?
block either V2 or V1/V2 receptors and increase free water excretion by the kidneys; they normalize serum Na in patients with non-osmotic release of AVP causing euvolemic (SIADH) or hypervolemic (CHF, liver failure) hyponatremia
Why are infusion site reactions common with administration of conivaptan, a V2/V1A receptor antagonist?
the pH of the drug is very low
T/F- vasopressin Rc antagonists have been shown to improve survival in patients with CHF?
false, but they do promote aquaresis and correct hyponatremia in this population
Which other drugs should be cautiously administered when giving conivaptan?
other CYP450 inhibitors such as ketoconazole
what is normal water intake for dogs? cats?
dogs- 90 ml/kg/day cats- 45 ml/kg/day
what is normal urine output for dogs? cats?
20-45 ml/kg/day for dogs and cats
what are the most common causes of PU/PD in dogs and cats?
chronic renal failure, diabetes mellitus, hyperadrenocorticism, hyperthyroidism
contraindications for water deprivation test?
azotemia, clinical dehydration, +/- severe polyuria b/c they could become rapidly dehydrated
Briefly describe a water deprivation test
-empty bladder + collect baseline data (body weight, hct, TP, skin turgor, osmolality, urine osmolality, USG) -withhold water and monitor data every 2-4 hours -stop test once animal concentrates urine or loses more than 5% body weight -if 5% body weight, give 0.25-0.5 U/kg aqueous vasopressin
At 5% body weight, what are the typical values for USG, urine osmolality and urine/plasma osmolality ratio in normal dogs and cats?
dogs- USG 1.050-1.076, urine osm 1787-2791, urine/plasma osm 5.7-8.9 cats- USG 1.047-1.087, urine osm 1581-2984
T/F- during a water depriv test, normal dogs and dogs with psychogenic polydipsia should show no response to ADH administration?
true
Describe the aqueous vasopressin test
IV infusion of aqueous vasopressin (pitressin) at 10 mU/kg is given over 60 min. Bladder is emptied and USG is measured at baseline and q30 min for 3 hrs.
Define COP
Force generated when 2 solutions with different concentrations of colloids are separated by a semipermeable membrane
What is albumin’s contribution to COP?
65-80%
What is the Gibbs-Donnan effect?
Sodium’s constribution to COP b/c they are noncovalently bound to negatively charged albumin
What besides albumin and sodium contribute to COP?
globulins, fibrinogen, hemoglobin, RBC (<5%)
Odunayo, JVECC, 2011. COP in WB vs. plasma. Main findings?
plasma COP * lower than whole blood COP with mean difference 0.5 mm Hg; regardless both in reference range (21-25 mm Hg); no diff in sex, decreased slightly when frozen, hemolysis had no effect
Hayes, JVECC, 2011. What significantly affected TPP readings?
hypercholesterolemia and hyperglycemia
An increase in serum glucose by ___ assc’d with increase in refractometer TPP of ____. Hayes, JVECC, 2011
10 mmol/L0.23 g/dL
An increase in serum cholesterol of 38.6 mg/dL (1 mmol/L) assc’d with increase in refractometer TPP of ____.
0.14 g/dL
TPP < 58 g/L was highly specific for serum hypoalbuminemia and hypoproteinemia. T/F Hayes, JVECC, 2011
T - 84% specificitynonlinear relationship
What formula predicted toal protein by refractometer?
serum protein (g/L) = 0.3 + 0.84(refractometer TP)
How does refractometer work?
measures angle of refraction b/t air and aqueous solution
Mechanisms of iHCa in trauma patients.
CalciuresisDilution following fluidsCellular uptake of calciumChelation with citrate in blood productsAberrations in hormones and electrolytes that regulate iCa
Holowaychuk, JVECC, 2011. Significant differences in iHCa trauma patients.
higher HR, lower SBP, higher ATT, higher systems score, lower HCO3, higher BE, higher lac, higher creat, higher mortality, longer in hospital, needed more transfusion, colloid, oxygen, vasopressor
The trauma system scores uses what 6 body systems?
skin, appendage, thorax, head, abdomen, spine
iHCa (<1.25) found in __% trauma patients. Holowaychuck, 2011, JVECC
16%
What are the 3 independent variables in Stewart AB?
Atot, pCO2, SID
What is Atot?
total plasma concentration of nonvolatile weak buffers such as albumin, globulins, and phosphate
What is SID?
Difference in charge between fully dissociated and therefore nonreactive or nonbuffering strong cations and strong anions at physiologic pH
What is the strong ion gap?
SIDa - SIDeSIDa: Na, K, Ca, Mg, Cl, lactateSIDe: HCO3, albumin, phosphate
SIG increased by ______ and decreased by ______.
unmeasured anions, unmeasured cations
What was the mean and derived ref range for SIG using SIDa-SIDe? Fettig, JVECC, 2012
mean 7.13; RR: 1.85-10.61
What was the mean and derived reference range for SIG using (alb) x 4.9-AG? This formula derived from Atot and Ka on healthy dogs. Fettig, JVECC, 2012
mean -0.22, RR: -5.36-5.18
SIG in vivo is usually…
positive due to an excess of unmeasured anions compared to unmeasured cations
BE takes into account…
free water, chloride, protein, and phosphate concentrations
T/F. A simple conversion factor can convert SIG1 to SIG2.
F - values are not interchangable and conversion factor cannot be used
What are the two methods to correct hyponatremia?
- Sodium deficit [(desired change)] x TBW2. Adrogue-Madias to determine estimation of effect of infusing a 1 L bag of fluids:(desired change) = (infusate Na - serum Na) / (TBW +1)
How do you calculate free water deficit?
TBW x (serum Na/normal sodium - 1)
For every 100 mg increase in glucose, sodium decreases…
1.6 - pseudohyonatremia
How much sodium does 23.4% have in mEq/ml
4
Myelinolysis lesions in dogs are typically found where?
thalamus (pons in humans)
What are the most common reasons for a Na/K less than 27:1
renal failure, hypoadrenocorticism, GI dz (whips, salmonella, duodenal perforation)also chronic chylothorax, lung lobe torsion, neoplastic pleural effusion, pregnancy in greyhounds
What is the most notable adverse metabolic effect of hypokalemia?
glucose intolerance, insulin release impaired
Cardiac effects of hypokalemia.
High intracellular to extracellular K induces state of electrical hyperpolarization leading to prolongation of the the action potential. This may predispose to atrial and ventricular tachyarrhythmias, AV dissociation, and ventricular fibrillationPredisposes to dig induced cardiac arrhythmias and causes myocardium to be refractory to class 1 antiarrhythmics
How do you treat a normovolemic, hyponatremic patient in an emergency setting of hyponatremia (chronic)?
mannitol along with furosemide to ensure that electrolyte free water is excreted along with the mannitol; goal = increase sodium no more than 10 mEq/L during first 24 hours
Causes of pseudohyperkalemia
thrombocytosis, leukocytosis, Akita dogs (their RBC have a fxnal Na-K ATPase so have high intracellular K),
Drugs that promote hyperkalemia
ACE inhibitors, Beta blockers, K sparing diuretics
Complexed calcium is bound to…
phosphate, bicarbonate, lactate, citrate, oxalate
Principle actions of PTH
increased tubular reabsorption of calcium, increased osteoclastic bone resorprtion, increased production of 1,25(OH)2D3
Calcitonin
Produced by thyroid gland in response to hypercalcemia, acts on bone to inhibit osteoclastic bone resorption activity
Effects of alkalosis and acidosis on ionized calcium?
alkalosis decreases iCa (b/c more bound to protein)acidosis increases iCa (b/c less bound to protein)
Clinical signs of hypercalcemia
PU/PD (dogs only), anorexia, constipation, lethargy, weakness, ataxia, obtundation, listlessness, muscle twitching, seizures, coma
ECG findings of hypercalcemia
prolonged PR interval, widened QRS, shortened QT, shortened or absent ST, widened T wave, bradyarrhythmias that progress to complete heart block, asystole, cardiac arrest
Most common cause of hypercalcemia in dogs vs cats?
dogs cancercats idiopathic
Why is 0.9% saline the fluid of choice for hypercalcemia?
Additional sodium ions present competition for calcium and result in reduced renal tubular calcium reabsorptionFurosemide enhances urinary calcium loss
Mechanism of hypercalcemia in fungal disease
due to dysregulated production of 1,25-(OH2)D3 (calcitriol) by activated macrophages trapped in pulmonary alveoli and granulomatous inflammation.
Steroid MOA for hypercalcemia
reduces bone resorption, increases urinary loss, decreases intestinal calcium absorption
Calcitonin MOA for hypercalcemia
decreases osteoclast bone resorption
Bisphosphonates MOA for hypercalcemia
Decreases osteoclast activity and bone resorptionEx: pamidronate, zoledronate, alendronate (oral)
Calcimimetic MOA
Activate the calcium sensing receptor and therefore decrease PTH