Electrolytes and Acid-Base Disorders Flashcards
What is the composition of infection stones?
- Magnesium ammonium phosphate (MgNH₄PO₄)
- Calcium phosphate carbonate (Ca₁₀[PO₄]₆ * CO₃)
LR 1L
1. Grams
2. mEq
3. pH
- NaCl 6, Na-Lactate 3.1, KCl 0.3, CaCl 0.2
- Na 130, Cl 109, Lactate 28, K 4, Ca 3
- 6.5
What are the molar masses (g/mol) of sodium, potassium, chloride, calcium and magnesium?
Sodium 23, Potassium 39, Chloride 35, Calcium 40, Magnesium 24
What is the pH and composition (grams and mEq) of 1L of Plasma-Lyte 148 solution?
Mass (g): Sodium Chloride 5.26, Sodium Gluconate 5.02, Sodium Acetate 3.68, Potassium Chloride 0.37, Magnesium Chloride 0.3
Ions (mEq): Sodium 140, Chloride 98, Potassium 5, Magnesium 3, Acetate 27, Gluconate 23
pH: 7.4
What are osmolality and osmolarity?
Osmolality measures the number of moles of dissolved particles per kilogram of solvent.
Osmolarity measures the number of dissolved particles per liter of solution.
Laboratory measurement technique of electrolytes
When metabolism converts the parent molecule to acid metabolites, such as formic acid (in the case of methanol) or glyoxylic and oxalic acid (in the case of ethylene glycol), their osmotic contribution disappears because each molecule of organic acid produced generates an equimolar disappearance of bicarbonate. Thus, this increase in organic anion osmoles is matched by an identical fall in bicarbonate osmoles. Consequently, the serum osmolal gap estimates the molar quantity of the uncharged parent alcohol molecules and any uncharged metabolites but not their strong acid metabolites
The addition of 20 mmol of methanol to each liter of extracellular fluid will raise the serum osmolality by approximately 20 mosmol/kg. If all of the methanol is converted to formic acid, then 20 mosmol of methanol has been converted to 40 mosmol of solute (20 hydrogen ions and 20 formate anions). However, the hydrogen ions will be largely buffered by bicarbonate. This causes bicarbonate to be converted to H2CO3 and then to H2O and CO2, which results in disappearance of both the hydrogen ion and the HCO3. The net effect is that, in each liter of extracellular fluid, 20 formate anions “replace” 20 bicarbonate ions, the serum osmolality then returns to its baseline level prior to the ingestion, and there is no serum osmolal gap.
What is the average renal pelvic pressure in normal humans during antidiuresis and during the passage of a ureteral stone?
5 mmHg, 25 mmHg
Chloride is largely restricted to the extracellular space (3, 80,
206, 243), which is 40% of total body water (TBW), unlike
sodium that distributes over TBW (206). Intravascular volume
accounts for 8% of TBW, and extravascular volume accounts
for 32%. One liter of normal saline contains 154 mEq chloride
and distributes 25% to the intravascular space and 75% to the
interstitium. The average normal plasma chloride concentration is 104 mEq/l (28). If 25% of chloride and water from
normal saline enters the intravascular space, 1 liter of normal
saline would increase plasma chloride in a 70-kg man from
104.0 to 107.5 mEq/l
What is Laplace’s Law and how does it help explain the arteriolar vasdilation seen within the immediate 2 to 3 hours after unilateral or bilaterla ureteral obstruciton?
The most probable explanation for this vasodilatory response involves a decrease in the inherent myogenic tone of the arterioles. Laplace’s Law, which is used to estimate resistance in blood vessels, states that T = R (Piv — Pev), where T represents wall tension, R is the inner radius of the vessel, and Piv and Pev are the intravascular and extravascular hydrostatic pressures, respectively.
During ureteral obstruction, there is an increase in intrarenal pressure, which raises Pev and reduces the transmural pressure gradient (Piv - Pev). Consequently, this decrease in wall tension leads to vasodilation, increase in R
Filtration Fraction (FF)
Filtration fraction in the context of renal physiology refers to the ratio of the amount of plasma that is filtered through the kidneys’ glomeruli to the total amount of plasma that passes through them. It is a measure of kidney function and indicates how much of the blood plasma passing through the glomeruli is actually filtered into the kidney tubules.
The filtration fraction is calculated as the Glomerular Filtration Rate (GFR) divided by the Renal Plasma Flow (RPF). The GFR is the rate at which blood is filtered through the glomeruli, and the RPF is the rate at which plasma flows through the kidneys.
In formula terms, it is represented as:
GFR
RPF
Filtration Fraction (FF)=
RPF
GFR
A normal filtration fraction is typically around 20%, meaning that about 20% of the plasma that enters the glomeruli is filtered into the kidney tubules, while the rest continues through the circulatory system.
What are the principal mechanisms that determine post-obstructive diuresis?
1) Increased circulating natriuretic factors like urea and ANP, which decreases sodium and water reabsorption in the loop of Henle and distal tubule of both surface and deep nephrons. ANP also decreases renal vascular resistance leading to increased filtrate delivery to the collecting ducts.
2) Impaired collecting duct function and reabsorption of sodium and water from reduced medullary solute concentration gradient and the effects of increased hydrostatic pressure caused by elevated medullary blood flow on transporters.
