Fluids and Electrolytes Pt 2 RW Exam 3

What are the components of total body water (TBW)?

Intracellular fluid (ICF) - 2/3 of TBW

Extracellular fluid (ICF) - 1/3 of TBW

What components make up extracellular fluid (ECF)?

Interstitial fluid - 15% of TBW

Plasma (intravascular fluid) - 5% of TBW

Transcellular fluid ("third spacing") - 1% of TBW

What electrolytes are found in the intracellular fluid (ICF)?

K

Mg

Phos

Proteins

What electrolytes are found in the extracellular fluid (ECF)?

Na

Cl

Bicarb (HCO3)

What is osmolality/tonicity?

Osmotic pressure and osmolality affect distribution of water among compartments

What indicates and osmolar gap?

>10 (diff. between measured and calculated osmolality)

Indicates presence of small osmotically active agents

What are the types of crystalloid fluids?

Isotonic - NS, LR

Hypotonic - 1/2NS, D51/2NS

Hypertonic - 3% NaCl

What are the isotonic crystalloids?

NS

LR

What are isotonic fluids (NS, LR) used for?

Resuscitation

(albumin can also be used for this)

What are the hypotonic crystalloids?

1/2NS

D5 1/2NS

What are hypotonic fluids (D51/2NS, 1/2NS) used for?

Maintenance

What are the hypertonic crystalloids?

3% NaCl

What are hypertonic fluids (3% NaCl) used for?

Very limited uses

Severe hyponatremia

To lower intracranial pressure

What fluids should be used as maintenance fluids?

Hypotonic fluids -- D5 ½ NS, ½ NS

What fluids should be used as resuscitation fluids?

Isotonic crystalloid -- NS, LR

What are causes of decrease in TBW (dehydration)?

Inadequate PO intake

Increased insensible losses

Diabetes insipidus

Osmotic diuresis

What happens to osmolality when there is a decrease in TBW (dehydration)?

Changes in osmolality common

Because TBW depletion represents a loss of hypotonic fluid (more water than sodium lost) from all body compartments

How is a decrease in TBW (dehydration) treated?

Resuscitation fluids: isotonic crystalloid (NS, LR)

What are causes of a decrease in ECF?

Hemorrhage

Burns

Diuresis

GI losses

Sepsis

Anaphylaxis

Ascites

What happens to osmolality when there is a decrease in ECF?

Rarely causes changes in osmolality

Because it's generally due to loss of isotonic fluid (proportional loss of sodium and water)

How is a decrease in ECF treated?

Need rapid resuscitation fluids (isotonic fluid) for tissue perfusion

What are the different types of HypoNatremia?

Hypotonic (low serum osmolality) - Hypovolemic, Euvolemic, or Hypervolemic

Isotonic (pseudohyponatremia)

Hypertonic (hyperglycemia)

What is Hypertonic HypoNatremia?

Serum osmolality is high (hypertonic)

ECF sodium appears decreased because other osmotically active molecules, usually glucose, are diluting the sodium

Sodium will decrease ~1mEq for every 60 mg/dL blood glucose over 200 mg/dL (calc. corrected Na)

What are causes of Hypertonic HypoNatremia?

Hyperglycemia

Hypertonic sodium-free solutions (mannitol)

How is Hypertonic HypoNatremia treated?

Treat hyperglycemia

Na will correct (only appears dec.)

What is Hypotonic HypoNatremia?

Low serum osmolality

Categorized by vol. status (Hypovolemic, Euvolemic, or Hypervolemic)

What is Hypotonic Hypervolemic HypoNatremia?

Excess of both total body sodium and TBW, but the excess of TBW is greater than the excess of sodium

Fluid volume status is high, and osmolality is low

What are common causes of Hypotonic Hypervolemic HypoNatremia?

CHF

Hepatic Cirrhosis

Nephrotic syndrome

How is Hypotonic Hypervolemic HypoNatremia managed?

Diuretics (furosemide)

Sodium and fluid restriction

Treat underlying cause

What is Hypotonic Euvolemic HypoNatremia?

Excess of TBW with a normal total body sodium content, causing an excess of free water

Patient does not appear fluid overloaded or dehydrated

What are common causes of Hypotonic Euvolemic HypoNatremia?

Syndrome of inappropriate antidiuretic hormone (SIADH)

What are causes of SIADH?

Medications (Antidepressants, antipsychotics, antiepileptics, others)

Pulmonary infections (TB, pneumonia)

Stroke, CNS disorders

Malignancy

Adrenal insufficiency

Hypothyroidism

How is Hypotonic Euvolemic HypoNatremia managed?

Remove underlying cause (when possible)

Restrict free water

Hypertonic saline if severe (Na < 110 mEq/L)

Meds: vasopressin receptor antagonists, Demeclocycline

What are the names of the vasopressin receptor antagonists?

Conivaptan - IV infusion

Tolvaptan - PO daily

What is the MOA of Demeclocycline for HypoNatremia?

Tetracycline derivative, used off-label based on side effect of inhibiting ADH

What is What is Hypotonic Hypovolemic HypoNatremia?

Deficit of both total body sodium and TBW, but the sodium deficit is greater than the TBW deficit

Fluid volume and osmolality are both low

What are common causes of Hypotonic Hypovolemic HypoNatremia?

Diuretic use

Profuse sweating

Wound drainage

Burns

GI losses (vomiting or diarrhea)

Hypoadrenalism (low cortisol and low aldosterone)

Renal tubular acidosis

How is Hypotonic Hypovolemic HypoNatremia managed?

Correct underlying cause

Calculate Sodium deficit for replacement

Replace with NS (safest)

At what rate should Na replacement occur?

Total correction over 48-72 hours

Acute (

What is the maximum Na correction that can be performed in the first 24 hours?

MAX 8-12 mEq/L/day in first 24 hours

What is the estimated change in Na after 1 L of 3% NaCl?

512 mEq of Na per L of 3% NaCl

What is the estimated change in Na after 1 L of NS?

154 mEq of Na per L of NS

How should Na be monitored during correction?

Q 2-4 hours until asymptomatic

Q 4-8 hours until Na in normal range

What is Central Pontine Myelinolysis (aka Osmotic Demyelination Syndrome)?

Neurologic problem related to overly rapid sodium correction

May occur in 1-6 days

May cause seizures, movement disorders, pseudobulbar palsy, quadriparesis

Do NOT correct sodium too quickly

What are the different types of HyperNatremia?

Hypovolemic

Isovolemic

Hypervolemic

What is Hypovolemic HyperNatremia?

Low total body volume, often resulting from a loss of hypotonic fluid (more water than sodium

Presentation: TBW depletion and dehydration

What are common causes of Hypovolemic HyperNatremia?

Vomiting

Diarrhea

NG suctioning

Osmotic diuresis

Burns

Sweat

How is Hypovolemic HyperNatremia treated?

Replace half the deficit in the first 24 hours, and the total in 48-72 hours

Use ½ NS or D5W (hypotonic fluids) to correct the deficit

If patient is hemodynamically unstable, use isotonic fluid (NS, LR) for repletion first

What is Isovolemic HyperNatremia?

Primarily caused by Diabetes Insipidus (DI), which causes the patient to excrete a large volume of hypotonic urine

What are common causes of Isovolemic HyperNatremia?

Central DI - lack of ADH

(Trauma, tumors, infection)

Nephrogenic DI - lack of kidney response to ADH

(electrolyte abnormalities, lithium, amphotericin B, clozapine)

How is Isovolemic HyperNatremia treated?

CDI: Desmopressin

NDI: Thiazide or indomethocin

What is Hypervolemic HyperNatremia?

Excess total body sodium and water, resulting from the intake of excessive sodium

What are common causes of Hypervolemic HyperNatremia?

Hypertonic saline or sodium bicarbonate solution infusion

How is Hypervolemic HyperNatremia treated?

Sodium restriction

Loop or thiazide diuretic

How does HypoKalemia present?

Frequently asymptomatic.

May have muscle cramps, weakness, EKG changes

What agents are used for HypoKalemia treatment?

Potassium chloride or acetate salt

Chloride most commonly used, benefit if alkalotic

Acetate may be used if acidotic

How is mild/moderate HypoKalemia treated?

Utilize oral K therapy

Use small and frequent doses (more effective and less ADRs)

How is severe (symptomatic or K

Utilize IV therapy

SLOW infusion - Do NOT exceed 10 mEq/hour

Decrease dose in renal impairment

May be difficult to replace if Mg is low

What is the maximum infusion rate for K?

10 mEq/hour

Unless cardiac monitored, central line, facility policy approves use, and it is medically necessary

How much do K levels increase for every 10 mEq given via IV?

K will increase ~ 0.1 per 10 mEq IV

What are common causes of HyperKalemia?

Medications (K-sparing diuretics, ACE-I, NSAIDs)

Increased intake (potassium supplementation, salt substitute)

Metabolic acidosis

Trauma/rhabdomyolysis

Hypoaldosteronism

What is pseudo-HyperKalemia?

Caused by hemolysis of blood sample or blood sample contaminated with potassium infusion

Falsely high K reading

How is HyperKalemia treated?

"C A BIG K Drop"

Calcium IV

Albuterol

Bicarbonate (when acidotic)

Insulin and Glucose

LoKelma

Diuretics and Dialysis

How does HypoMagnesemia present?

Often seen with hypoCa and hypoK

Frequently asymptomatic

May have weakness, cramps, tremor, hypocalcemia, refractory hypokalemia

May cause EKG changes

Goal Mg > 2 in patients with cardiac history

What are common causes of HypoMagnesemia?

Medications: CISPLATIN (most common), aminoglycosides, amphotericin, diuretics

How is HypoMagnesemia treated?

IV treatment preferred

Empiric dosing of 1-2 grams IV over 60 mins

(oral therapy assoc. w/ diarrhea)

(if asymptomatic/mild just increase oral intake)

How does HypoPhosphatemia present?

Muscle weakness—including diaphragm/respiratory failure, N/V, seizures, coma

How is mild (asymptomatic/phos>2.6) HypoPhosphatemia treated?

High phosphorous diet (Skim milk)

How is moderate HypoPhosphatemia treated?

Oral supplementation

(note sodium and potassium concentrations in various products)

How is severe (resp. failure/symptomatic/phos

Injectable Na- or K-Phos

When is oral therapy preferred for treatment of HypoPhosphatemia?

Oral preferred if functional GI tract and asymptomatic or mildly low levels

How should HypoPhosphatemia IV therapy be dosed?

Always dose in mMol

Decrease dose in renal impairment! (no more than half calculated dose)

Generally infused over ~6 hours (Always calculate K+ infusion rate!)

What are the options for HypoPhosphatemia IV therapy?

K or Na salt form

Choice is always dependent on the pt.'s K level

If pt. doesn't need K always give Na-Phos

How much K is in 1 mMol of KPhos?

~ 1.5 mEq K per mMol KPhos

How much Na is in 1 mMol of NaPhos?

~ 1 mEq Na per mMol NaPhos

What are common causes of HyperPhosphatemia?

Renal impairment is most common cause

Other causes: hypoparathyroidism, increased intake, drugs containing phosphorous or bisphosphonates

How is HyperPhosphatemia treated?

Often benign, no treatment needed

If need treatment - Dialysis, Phosphate binders

What are phosphate binder options?

Calcium-based binder (calcium carbonate/acetate)

Non-calcium binder (aluminum based antacid, sevelamer, lanthanum)

How is the choice between a Ca-based and non-Ca based phosphate binder made?

Ca-based binder (calcium carbonate/acetate) is default choice

Only use non-Ca based if pt. has high Ca

How is HypoCalcemia managed?

Check Mg concentration, correct if low

Acute/symptomatic: IV Ca

Chronic/asymptomatic: Oral Ca

How is HyperCalcemia managed?

Rehydration- normal saline (at 200-300 mL/h)

Mild hypercalcemia: hydration alone

When the pH is low (

Acidosis

When the pH is high (>7.45), what is the primary acid base disorder?

Alkalosis

When the pH is low (

Respiratory Acidosis

(resp. opposite - low pH and high pCO2)

When the pH is low (

Metabolic Acidosis

(metabolic equal - low pH and low HCO3)

When the pH is high (>7.45) and the pCO2 is low (

Respiratory Alkalosis

(resp. opposite - high pH and low pCO2)

When the pH is high (>7.45) and the HCO3 is low (>26), what is the acid base disorder?

Metabolic Alkalosis

(metabolic equal - high pH and high HCO3)

What indicates an anion gap?

>12 mEq/L indicates anion gap

What are the causes of Metabolic Acidosis with a elevated anion gap?

"MUD PILES"

M- Methanol, metformin

U- Uremia

D- Diabetic (or alcoholic) ketoacidosis

P- Paraldehyde, phenformin

I- Isoniazid, iron

L- Lactic acidosis

E- Ethylene glycol, ethanol

S- Salicylates

How is Metabolic Acidosis managed?

Treat underlying cause (MUD PILES)

Sodium bicarbonate - reserved for pH < 7.1

When is sodium bicarbonate used for treatment of Metabolic Acidosis?

Generally reserved for pH< 7.1 (severe cases)

May be more necessary if renal impairment

May cause volume overload, hypernatremia, hypokalemia

What are common causes of Metabolic Alkalosis?

Fluid deficit

How is Metabolic Alkalosis treated?

Treat underlying cause (fluid deficit)

Acetazolamide (Diamox) 500mg IV x1, then assess efficacy

If severe: may utilize dialysis or HCl infusion

What is the MOA of Acetazolamide for treatment of Metabolic Alkalosis?

Carbonic anhydrase inhibitor

Increases renal secretion of bicarbonate, sodium, potassium, and water

How are Respiratory Acidosis and Alkalosis treated?

Treat underlying cause

Supportive therapy: Mechanical ventilation, Rebreathing mask/paper bag

How is DKA treated?

Fluid replacement

Correct blood glucose

Correct electrolyte abnormalities