Fluids And Electrolytes Flashcards by Jing Alabado

The pathophysiology of metabolic alkalosis is divided into 2 factors

A particularly important maintenance factor is?

Generating
Maintenance

Renal response to hypovolemia

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Target blood glucose to lower mortality

180 mg/dL

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Factors that generate metabolic ALKALOSIS are (2)

Vomiting

2. Diuretic administration

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Treatment of metabolic alkalosis(2)

Expansion of intravascular volume

2. Potassium administration

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This most rapidly corrects life threatening metabolic alkalosis

0.1 N hydrochloric acid

Administered through a central vein to prevent tissue damage

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Metabolic acidosis, what anion gap occurs when bicarbonate is lost externally.

Normal anion gap (< 13 mEq/L)

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Metabolic acidosis, what anion gap occurs because of excess production or decreased excretion of organic acids or ingestion of one of several toxic compounds.

High anion gap

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How much is ICV of total body weight?

60%

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How much is ECV of total body weight?

20%

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The primary mechanism of controlling water intake

Thirst

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Final osmolality of tubular fluid

1200 mOsm/kg

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Daily adult requirement for
Na
K

75 meqs

40 meqs

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Number of osmotically active particles per LITER of solvent

Osmolarity

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Number of osmotically active particles per KILOGRAM

Osmolality

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This volume is determined by the rates of capillary filtration and lymphatic drainage.

IFV (interstitial fluid volume)

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Because of the influence of the glycocalyx, theoretical rates of fluid filtration usually substantially exceed actual filtration rates, a phenomenon termed as

Low lymph flow paradox

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What is a positive tilt test?

A positive tilt test defined as an increase in heart rate of at least 20 beats per minute and a decrease in systolic blood pressure of 20 mmHg or more when the subject assumes the upright position.

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How many % of nephrons must be dysfunctional before serum creatinine exceeds the normal range.

40 to 50%

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Requirement of PPV (4)

Direct arterial monitoring
Mechanical ventilation
Vt of 8 mL/kg
No cardiac arrhythmia

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In esophageal doppler assessment of iop blood volume

A corrected flow time of 0.35 suggests
A corrected flow time of 0.40 suggests

Volume expansion should improve CO

Further volume expansion will be ineffective

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In high risk surgical patients, these parameters has been associated with improved outcomes (3)

DO2I of 600 mL/m2/min (equivalent to a cardiac index of 3)
Hgb of 14 g/dL
98% oxyhgb

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Disorders of total body sodium are affected by two factors

2. PV

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Is the most common electrolyte problem in hospitalized patients

Hyponatremia

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Plasma sodium DECREASES approximately how much for each 100 mg/dL rise in glucose concentration

2.4 mEq/L

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The vasopressin-regulated water channel

Aquaporin 2

Diagnosis of SIADH (6)

1. Hyponatremia (low plasma osmolality) 2. Urinary osmolality > plasma osmolality 3. Renal sodium excretion > 20 mmol/L 4. Absence of hypotension, hypovolemia & edematous states 5. Normal renal & adrenal functions 6. Absence of drugs that affect renal water & sodium handling

Cornerstone of SIADH

Free water restriction (0.5 - 1L per day) | Elimination of cause

As long as GFR is above this level, potassium intake can be excreted.

8 mL/min

2 most important regulators of potassium excretion

1. Plasma K | 2. Aldosterone

Hallmark of hypocalcemis

Increased neuronal membrane irritability and tetany

Low or normal phosphate concentrations imply 2 things

1. Vitamin D deficiency | 2. Magnesium deficiency

High phosphate concentration suggests (2)

1. Renal failure | 2. Hypoparathyroidism

Enzyme responsible for conversion of calcidiol to calcitriol

1a hydroxylase

Treatment of hypocalcemia

Treat cause

Symotomatic hypocalcemia occurs when serum ionized calcium is?

Less than 0.7 mM

Correction of this electrolyte abnormality without treating hypocalcemia may provoke tetany

Hypokalemia

Has been called an enogenous calcium antagonist

Magnesium

How does Magnesium function in potassium metabolism?

Regulating Na K ATPase enzyme especially in potassium depleted states, and controls reabsorption of potassium

Absorption of most Mg

Thick ascending loop of Henle

An electrolyte that may block the NMDA receptor

1 gram of magnesium sulfate provides approximately how much mmol, meqs and mg of elemental mg?

4 mmol 8 meqs 98 mg

Symptomatic hypomagnesemia should be treated with?

MgSO4 1 to 2 grams IV for 1 hour Then 2 to 4 meqs/hr infusion Infusion should not exceed 1 meq/min

Most cases of hypermagnesemia are due to?

Iatrogenic causes

Criteria for SIADH (6)

1. Hyponatremia, low plasma osmolality 2. Urinary greater than plasma osmolality 3. Renal sodium excretion > 20 mmol/L 4. No hypotension, hypovolemia & edema 5. Normal renal & adrenal functions 6. Absence of drugs affecting renal & sodium handling

Is a class of drugs that inhibit the action of AVP

Vassopressin receptor blocking agents

Is a vassopressin receptor blocking agent that inhibits both V1a and V1b. However, there are potential decreases of blood pressure when V1a is blocked.

Conivaptan

This drug only blocks the V2 receptor

Tolvaptan

This is indicated for hyponatremic patients who experience seizures

Hypertonic 3% saline (1 to 2 mL/kg/hr or 1 to 2 meqs/L/hr) NO MORE THAN 4 to 8 meqs/L/day

Principal determinants of neurological injury in Na replacement therapy (2)

1. Severity & chronicity of hyponatremia | 2. Rate of correction

Osmotic demyelination is more common if hyponatremia persisted for how many hours

48 hours

Rate of hyponatremia should be at? It should not exceed for how much rate?

Above 1 to 2 meqs/L in an hour No more than 8 meqs/L/day

Why are geriatric patients at risk for hypernatremia

Because of decreased renal concentrating ability

Criteria diagnostic of DI (3)

1. Hypertonicity 2. Polyuria 3. Hypotonic urine (<150 mOsm/kg)

Central DI drug treatment (2)

1. Desmopressin (DDAVP), 10-20 ug intranasally, 2-4 ug SC 2. Aqueous vasopressin (5 U q2-4H IM or SC) DDAVP: longer duration without VASOCONSTRICTOR EFFECTS

TBW deficit is the first step in treating hypernatremia What is the formula.

TBW deficit = 0.6 x body weight x [(Na - 140)/140)] Water deficit should be replaced over 24 to 48 hours Should not exceed 1 to 2 meq/L/hr If present for 2 days, no more than 10 meqs/L/day

Is a drug that potentiates the renal effects of vasopressin, ang carbamazepine, which enhances vasopressin excretion.

Chlorpropramide

Potassium concentration 1. Intracellular? 2. Extracellular?

150 meqs/L | 3.5 to 5 meqs/L

As long as GFR is above this rate, potassium can be excreted

8 mL/min

Major site at which potassium excretion is regulated

DCT

Two most important regulators of potassium

1. Plasma K | 2. Aldosterone

As a general rule, a chronic decrement of 1 meq/L in plasma potassium corresponds to a total body deficit of how much?

200 to 300 meqs

Read

Cardiac rhythm disturbances are among the most dangerous complications of potassium deficiency. Acute hypokalemia causes HYPERPOLARIZATION of the cardiac cell and may lead to ventricular escape activity, re-entrant phenomena, ectopic tachycardias, and delayed conduction.

This drug increases its binding capacity into the myocardium if associated with hypokalemia

Digoxin

Aldosterone primarily controls this electrolyte reabsorption and not potassium excretion.

Sodium reabsorption

Read

Potassium is usually replaced as the chloride salt because coexisting chloride deficiency may limit the ability of the kidney to conserve potassium.

Ascending muscle weakness appears when plasma K is?

7 meqs/L

If hyponatremia exists with hypokalemia what organ should be evaluated?

Adrenals

Drugs that may contribute to hyperkalemia (5)

1. NSAIDs 2. ACEi 3. Cyclosporine 4. Potassium-sparing diuretics 5. Triamterene

Salbutamol decreases potassium acutely by how much?

1 meq/L

What are the two most important regulators of calcium?

PTH | Calcitriol

Hallmark of hypocalcemia is?

Increased neuronal membrane irritability and tetany

Read

In renal insufficiency, reduced phosphorus excretion results in hyperphosphatemia, which downregulates the 1a hydroxylase responsible for the conversion of calcidiol to calcitriol.

Symptomatic hypocalcemia usually occurs when ionized calcium is less than?

0.7 mM

What 2 electrolyte abnormalities potentiate hyocalcemic induced cardiac and neuromuscular irritability?

1. Hyperkalemia 2. Hypomagnesemia Therefore correction of hypokalemia without correction of hypocalcemia may provoke tetany.

Oral calcium can be substituted once serum calcium is at what level?

4 to 5 mg/dL

In hypoalbuminemic patients, total serum calcium can be estimated by assuming an increase of how much?

0.8 mg/dL for every 1 g/dL of albumin concentration below 4 g/dL