Fluid + Electrolytes RW Exam 3

Total body water (TBW)

60% of lean body weight (50% of lean body weight in females, 60% in males)

Intracellular fluid (ICF)

Water contained within the cells, rich in electrolytes

Extracellular fluid (ECF)

Fluid outside the cell; rich in sodium, chloride, and bicarbonate

Serum electrolytes

Routinely measured from the ECF

Interstitial fluid

Fluid occupying the spaces between cells, about 25% of TBW, often accepted as 15%

Intravascular fluid (plasma)

Fluid within the blood vessels, about 8% of TBW, often accepted as 5%

Transcellular fluid

Includes viscous components of peritoneum, pleural space, pericardium, cerebrospinal fluid, joint space fluid, GI digestive juices; 1% of TBW

Electrolytes in ICF

Potassium, Magnesium, Phosphates, and Proteins

Electrolytes in ECF

Sodium, Chloride, and Bicarbonate

Safe infusion rate for Potassium Chloride

10 mEq/hour for most patients

Common oral administration ADR for Potassium Chloride

GI upset

Furosemide

Loop diuretic with a BBW for profound fluid and electrolyte depletion (particularly low potassium)

Hydrochlorothiazide

Thiazide diuretic

Ideal body weight (IBW) for Males

50 kg + (2.3 kg/in x [ht in inches - 60])

Ideal body weight (IBW) for Females

45.5 kg + (2.3 kg/in x [ht in inches - 60])

Cockcroft-Gault equation for Males

[(140 - age) x IBW] / (72 x serum creatinine)

Cockcroft-Gault equation for Females

[(140 - age) x IBW] / (72 x serum creatinine) x 0.85

Fluid balance

Maintained when input and output are equal.

Typical input

Total amount of fluid gained throughout the day, averaging 1,400 mL/day.

Sensible losses

Urinary and stool losses that are easily measured.

Insensible losses

Evaporation of fluid through the skin and/or lungs that is not readily measurable.

Additional fluid losses in hospitalized pt.'s

Includes enteric suctioning, surgical drains, fistulous tracts, and enhanced evaporative losses.

Symptoms of TBW depletion

Includes CNS disturbances, excessive thirst, dry mucous membranes, decreased skin turgor, elevated serum sodium, increased plasma osmolality, concentrated urine, and acute weight loss.

Common causes of TBW depletion

Insufficient oral intake, excessive insensible losses, diabetes insipidus, excessive osmotic diuresis, and impaired renal concentrating mechanisms.

Calculation of maintenance fluid requirements for adults

Calculated as 1,500 mL + 20 mL for each kg >20.

Fluid deficit calculation

Acute weight change (kg of weight lost = L of water) or

Normal TBW - Present TBW = L of additional fluid requirement.

Replacement fluids calculation

Maintenance fluid requirements + ongoing exceptional losses + fluid deficit.

Symptoms of ECF depletion

Includes dizziness, orthostasis, tachycardia, decreased urine output, increased hematocrit, decreased central venous pressure, and hypovolemic shock.

Common causes of ECF depletion

External fluid losses, third spacing of fluids, including septic shock and anaphylactic shock.

Isotonic crystalloids

0.9% NaCl (NS) and Lactated Ringers

Uses of isotonic crystalloids

Any TBW depletion: perioperative fluids, shock, hemorrhage, burns, hyponatremia, metabolic contraction alkalosis

*Lactate works as a buffer to increase pH (should not be used in liver disease)

*Large volume of NS can cause metabolic acidosis

Hypotonic crystalloids

0.45% NaCl (½ NS) and D5 1/2 NS

Use of 0.45% NaCl (½ NS) (hypotonic crystalloid)

Patients who are hypotonic due to primary depletion of the ECF

Serum Na must be closely monitored during admin.

Use of D5 ½ NS (hypotonic crystalloid)

Commonly used as maintenance fluid

Used once fluid deficits have been corrected with NS or LR

Serum Na must be closely monitored during admin.

Hypertonic crystalloids

3% NaCl

Use of 3% NaCl (hypertonic crystalloid)

Patients with severe hyponatremia, who have symptoms due to low serum Na

Can be used to acutely lower intracranial pressure, in traumatic brain injuries and stroke

Short term use

Frequent serum Na and neurologic checks closely monitored

Colloids names

Albumin, HES, Dextran

Albumin indications

Plasmapheresis/apheresis

Large volume paracentesis (>4 L removed)

Hypotension in hemodialysis

Spontaneous bacterial peritonitis

Albumin inappropriate uses

Nutritional supplementation, pancreatitis, alteration of drug PK's, or acute normovolemic hemodilution in surgery

HES limitations

Acquisition cost, hypersensitivity, bleeding, increased risk of mortality and severe renal injury

Dextran limitations

Anaphylactic reactions, prolonged bleeding times

Osmolality

A measure of the number of osmotically active particles per unit of solution

Normal serum osmolality

Normally 280-300 mOsm/kg

Osmolar gap calculation

Osmolar gap = Measured osmolality - calculated osmolality

Osmolar gap greater than 10 mOsm/kg

Suggests the presence of a small osmotically active agent, commonly seen with the ingestion of alcohols or medications such as mannitol or lorazepam

Hyponatremia

Na< 135 mEq/L

Symptoms of hyponatremia

Irritability, mental slowing, unstable gait/falls, fatigue, headache, nausea

Symptoms of hyponatremia

Confusion, seizures, stupor/coma, respiratory arrest

Hypertonic hyponatremia mechanisms

EC sodium is "decreased"

(other osmotically active molecules in large quantities "dilute" the sodium- usually glucose)

Hypertonic hyponatremia causes

1. Hyperglycemia

2. Hypertonic sodium-free solutions (mannitol)

Hypertonic hyponatremia management

1. Treat hyperglycemia

Hypotonic (hypervolemic) hyponatremia mechanisms

Hypotonic hyponatremia w/ inc. ECF

Excess of total body Na and TBW, excess of TBW > excess Na

Hypotonic (hypervolemic) hyponatremia causes

1. CHF

2. Hepatic Cirrhosis

3. Nephrotic syndrome

Hypotonic (hypervolemic) hyponatremia management

Sodium and fluid restriction, in combination with treating underlying cause

Hypotonic (euvolemic/isovolemic) hyponatremia mechanism

Hypotonic hyponatremia with normal ECF

Excess of TBW, with normal Na content

Presence of excess free water

Hypotonic (euvolemic/isovolemic) hyponatremia causes

Most commonly seen in pt.'s with syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Common causes of SIADH

Carcinomas (lung or pancreas), pulmonary disorders (pneumonias or TB), CNS disorders (meningitis, stroke, tumor, trauma), medications (sulfonylureas, antineoplastic, barbiturates, morphine, antipsychotics, TCAs, NSAIDs, SSRIs, DA agonists, general anesthetics).

Short term management of Hypotonic (euvolemic/isovolemic) hyponatremia

1. Remove or treat underlying cause

2. Restrict free water

3. Severe symptoms (Na

Long term management of Hypotonic (euvolemic/isovolemic) hyponatremia

Fluid restriction, demeclocycline, loop diuretics, lithium, tolvaptan (do not need to know doses).

Concern w/ correction of hyponatremia

Overly aggressive corrections (>12 mEq/L/day) can cause central pontine myelinolysis (osmotic demyelination syndrome).

Hypotonic (Hypovolemic) hyponatremia mechanism

Deficit of both total body Na and TBW, with deficit of Na > TBW deficit.

Hypotonic (Hypovolemic) hyponatremia causes

Diuretic use, profuse sweating, wound drainage, burns, GI losses (vomiting or diarrhea), hypoadrenalism (low cortisol and low aldosterone), renal tubular acidosis.

Hypotonic (Hypovolemic) hyponatremia management

1. Correct underlying cause

2. Calculate Sodium deficit = TBW (desired Na — Current Na)

0.9% NS is safest way to replace sodium and water. Hypertonic saline is generally reserved for severe hyponatremia

Sodium deficit calculation

Sodium deficit = TBW (desired Na — Current Na).

Safest way to replace sodium and water

0.9% NS is safest way to replace sodium and water; hypertonic saline is generally reserved for severe hyponatremia.

Hypernatremia

Na > 145 mEq/L.

Symptoms of hypernatremia

Thirst, mental slowing, dry mucus membranes; severe symptoms include confusion, hallucinations, acute weight loss, decreased skin turgor, intracranial bleeding, and/or coma.

Common causes of hypernatremia

Associated with TBW depletion

Dehydration from loss of hypotonic fluid from the respiratory tract or skin, decreased water intake, osmotic diuresis (mannitol), and diabetes insipidus (decreased ADH, phenytoin, lithium).

Management of hypernatremia

1. Calculate TBW deficit

2. Replace fluids with 0.9% NaCl until hemodynamically stable, then can change to D5W or 0.45% NaCl over total 24-48 hours

Correction should not exceed 0.5 mEq/L/h to prevent cerebral edema and death.

Hypokalemia presentation

Serum K

Common causes of hypokalemia

GI losses (vomiting, diarrhea, NG tube suction), renal losses (high aldosterone and low Mg), inadequate K intake (in IV fluids or oral), alkalosis.

Medications that precipitate hypokalemia

B2-agonists (albuterol), insulin, loop diuretics (furosemide), thiazide diuretics (hydrochlorothiazide), high-dose antibiotics (penicillin), corticosteroids (prednisone), amphotericin B, cisplatin, foscarnet.

Management of hypokalemia

KCl & Potassium acetate - most commonly used

KCl preferred for alkalosis patients; K acetate for acidosis patients.

Route: oral for moderate severity, IV for severe (do NOT exceed 10 mEq/h w/o continuous cardiac monitoring)

Hyperkalemia presentation

Serum K >5 mEq/L

Symptoms include muscle weakness, paresthesia, hypotension, ECG changes, cardiac arrhythmias, decreased pH.

Common causes of hyperkalemia

Increased K intake: excessive dietary K, excess K in IV fluids, medications (K-sparing diuretics, cyclosporine, ACE inhibitors, NSAIDs, pentamidine, UFH, LMWH).

Dec. K excretion: Acute renal failure, Chronic renal failure, Addison's disease

K release from intracellular space: Tissue breakdown (surgery, trauma, hemolysis, rhabdomyolysis), Blood transfusions, Metabolic acidosis

Management of hyperkalemia

"C A BIG K Drop"

C- calcium gluconate if >7 or EKG changes

A- albuterol nebulized

B- bicarb

I- insulin &

G- glucose

K- kayexalate/ sodium polystyrene sulfonate or sodium zirconium cyclosilicate (Lokelma)

D- diuretics and dialysis

C A BIG K Drop mnemonic

A mnemonic for treatments of hyperkalemia: Calcium gluconate, Albuterol, Bicarbonate, Insulin, Glucose, Kayexalate, Diuretics.

Hypocalcemia presentation

Ca < 6.5 mg/dL

Symptoms: Tetany, Circumoral tingling, Muscle spams, Hypoactive reflexes, Anxiety, Hallucinations, Hypotension, MI, Seizures, Lethargy, Stupor, Trousseau's or Chvostek's sign

Hypocalcemia causes

Hypoparathyroidism

Hypomagnesemia

Alcoholism

Hyperphosphatemia

Blood product infusion

Chronic renal failure

Vitamin D deficiency

Acute pancreatitis

Alkalosis

Hypoalbuminemia

Meds:

Phosphate replacement products

Loop diuretics

Phenytoin

Phenobarbital

Corticosteroids

Aminoglycoside antibiotics

Acetazolamide

Management of Hypocalcemia

Check Mg concentration, correct if low

Acute symptomatic: 200-300 mg elemental Ca IV, repeat until symptoms fully controlled

Use 1g of Ca Chloride or 2-3g Ca gluconate, at rate no faster than 30-60 mg elemental Ca per minute

Use of Ca gluconate preferred for peripheral use

Chronic asymptomatic: oral Ca supplements, 2-4g/day of elemental Ca

Hypercalemia presentation

Ca>10.2 mg/dL

Moderate to severe- anorexia, confusion, cardiac manifestations, acute renal failure, ventricular arrhythmias

Hypercalemia causes

1. Disease states (hyperparathyroidism, malignancy, Paget's disease, Addison's disease, granulomatous diseases, hyperthyroidism)

2. Other (immobilization, multiple bony fractures, acidosis, milk-alkali syndrome)

3. Drugs (thiazide diuretics, estrogens, lithium, tamoxifen, vitamin A, vitamin D, calcium supplements)

Hypercalemia management

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

Mild hypercalcemia- hydration alone

*Treatment of underlying cause*

Hypophosphatemia presentation

Serum P

Hypophosphatemia causes

Inc distribution to the ICF (hyperglycemia, insulin therapy, malnourishment)

Dec. absorption (starvation, excessive use of p-binding antacids, Vit D deficiency, diarrhea, laxative abuse)

Inc. renal loss (diuretic use, DKA, alcohol abuse, hyperparathyroidism, burns)

Meds:

Diuretics (acetazolamide, furosemide, HCTZ)

Sucralfate

Corticosteroids

Cisplatin

Antacids (Al carbonate, Ca carbonate, Mg oxide)

Foscarnet

Phenytoin

Phenobarbital

Phosphate binders (sevelamer, Ca acetate)

Hypophosphatemia management

Mild cases (2.6-2.7)- high-phosphorous diet (eggs, nuts, whole grains, meat, fish, poultry, milk products)

Moderate cases (1.6-2.5)- oral supplementation of 1.5-2 g/day (usually phosphate, unless hypokalemia present, then potassium phosphate) May be limited by diarrhea

Severe cases (Phos

Hyperphosphatemia presentation

Serum P >4.5 mg/dL

Symptoms: Parasthesias, ECG changes, Metastatic calcifications

Causes of Hyper-phosphatemia

Impaired P excretion (hypoparathyroidism, renal failure),

Redistribution of P to ECF (acid-base imbalance, rhabdomyolysis, muscle necrosis, tumor lysis),

Inc P intake (meds)

Medications causing Hyper-phosphatemia

Enemas w/ P, Laxatives w/ phosphate or P, Parental or oral supplements, Vitamin D supplements, Bisphosphonates

Management of Hyper-phosphatemia

Generally benign, rarely needs therapy

Most cases- dietary restriction of phosphate and protein

Renal failure- phosphate binders (aluminum-based antacids, calcium carbonate, calcium acetate, sevelamer, lanthanum carbonate)

Hypo-magnesemia presentation

Serum Mg

Hypo-magnesemia causes

Inadequate intake (alcoholism, dietary restriction, inadequate Mg in TPN),

Inadequate absorption (steatorrhea, cancer, malabsorption syndromes, excess Ca or P in GI tract),

Excessive GI loss of Mg (diarrhea, laxative abuse, NG tube suctioning, acute pancreatitis),

Excessive urinary loss of Mg (primary hyperaldosterism, meds, DKA, renal disorders)

Medications causing Hypo-magnesemia

Aminoglycoside antibiotics, Amphotericin B, Cisplatin, Insulin, Cyclosporine, Loop diuretics, Thiazide diuretics

Management of Mild Hypo-magnesemia

Increased oral intake of magnesium-containing foods or oral supplementation (magnesium oxide)

Management of Severe Hypo-magnesemia

IV magnesium sulfate

*Magnesium concentration does not correlate well with total body magnesium stores, so often magnesium is administered empirically to critically ill patients

Hyper-magnesemia presentation

Serum Mg >2.4 mEq/L

Symptoms of Mild Hyper-magnesemia

Nausea, vomiting, cutaneous vasodilation, bradycardia

Symptoms of Moderate Hyper-magnesemia

Hyporeflexia, weakness, somnolence, hypotension, ECG changes

Symptoms of Severe Hyper-magnesemia

Muscle paralysis, complete heart block, asystole, respiratory failure, refractory hypotension, death

Causes of Hyper-magnesemia

Renal failure

Drugs (magnesium-containing cathartics, antacids, and supplements; lithium)