Fluids + Electrolytes Summary Slides HL

What are functions/importances of electrolyes?

Metabolic functions

Maintenance of cell structure/function

Neurotranmission

Hormone function

Muscle contraction

CV function

Bone composition

Fluid and acid-base regulation

Critical Illness (ICU)

What is the importance of electrolytes in the ICU?

acute changes (i.e., renal rxn, hormones, meds) and treatment implications

How much of weight is total body water (TBW)?

60%

What is intracellular fluid (ICF)?

represents water contained within cells and is rich in K, Mg, P, and proteins

2/3 of TBW (~40%)

What is extracellular fluid (ECF)?

fluid outside of cells and is rich in Na, Cl, bicarb

1/3 of TBW (~20% clinically) and is divided into 2 compartments

What are the compartments of ECF?

interstitial fluid and intravascular fluid (plasma)

What is interstitial fluid?

fluid occupying the spaces between the cells

25% of TBW (15% clinically)

What is intravascular fluid (plasma)?

fluid within the blood vessels

8% of TBW (5% clinically)

What is transcellular fluid?

Includes viscous components of peritoneum, pleural space, pericardium, cerebrospinal fluid, joint space fluid, GI digestive juices

"third spacing" when increased

1% of TBW

What is "third spacing" of transcellular fluid?

can increase significantly during various illnesses favoring fluid collection (i.e., pleural effusions, ascites in peritoneum)

What is the maintenance fluid calculation?

1500mL + 20mL for each kg above 20kg

fluids in = fluids out

What is included in your typical "input"?

total amount of fluid gained throughout the day: IV fluids (+ med solns) and PO intake

What is included in your typical "output"?

total amount of fluid lost throughout the day: urine/stools ("sensible") and evaporation of fluid via skin/lungs ("insensible")

What are examples of hypotonic fluids?

D5 1/2 NS and 1/2 NS

What is a decrease in TBW called?

dehydration

What are S/S of dehydration?

Thirst

Decreased skin turgor

Dark urine

Acute weight loss

CNS changes

Is there an osmolality change during dehydration?

usually

What are causes of dehydration?

Inadequate PO intake

Increase insensible losses

Diabetes insipidus

Osmotic diuresis

What fluids are used for resuscitation?

isotonic crystalloids (NS, LR)

What are S/S of a decrease in ECF?

Acute

Orthostatic hypotension

Tachycardia

Decreased urine output

Increase hematocrits

Is there an osmolality change in ECF?

rarely

What can cause a decrease in ECF?

Hemorrhage

Burns

Diuresis

GI losses

Sepsis

Anaphylaxis

Ascites

True or False: when there is a decrease in ECF, we need rapid resuscitation fluids (isotonic) for tissue perfusion

True

What level of Na indicates hyponatremia?

< 135 mEq/L

What must be evaluated first when there are signs of hyponatremia?

serum osmolality/tonicity: hypo, iso, hyper

What is hypotonic hyponatremia?

low serum osmolality which can either be hypo, eu, or hypervolemic

What is isotonic hyponatremia?

pseudohyponatremia

What is hypertonic hyponatremia?

hyperglycemia

What must be evaluated after tonicity when hyponatremia occurs?

volume status

What affects distribution of water among compartments?

osmotic pressure and osmolality

What is the natural osmolality range?

280-300 mosmol/kg

What is the osmolality equation?

2(Na) + (BUN/2.8) + (glucose/18)

Can osmolality be measured or calculated?

BOTH (finding the difference is how to measure the osmolar gap)

What level of an osmolar gap indicates presence of small osmotically active agents?

above 10

What are the sodium assessment steps?

1. Assess Na (normal 135-147mEq/L)

2. Assess osmolality/tonicity (hypo-, iso-, hypertonic)

3. Assess fluid status (eu-, hypo-, hypervolemic)

What causes euvolemic hyponatremia?

Syndrome of inappropriate antidiuretic hormone (SIADH):

- SSRIs

- Antipsychotics

- TCAs

- CBZ

- Pulmonary infections (TB, pneumonia)

- Stroke

- CNS disorders

- Malignancy

- Adrenal insufficiency

- Hypothyroidism

What is the treatment of euvolemic hyponatremia?

Remove underlying cause (when possible)

Restrict free water

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

Vasopressin receptor antagonists

Demeclocycline

What are vasopressin receptor antagonists used in euvolemic hyponatremia?

Conivaptan (Vaprisol) IV infusion or Tolvaptan (Samsca) PO QD

What are limitations of Tolvaptan (Samsca)?

limited to 30 days bc of hepatotoxicity and must be started in hospital to monitor Na

What is Demeclocycline?

tetracycline derivative used off-label to treat euvolemic hyponatremia

What are C/I of Demeclocycline?

pregnancy and children < 8 years

Summary of Euvolemic Hyponatremia:

SIADH

Free water fluid restriction

Remove underlying cause

Consider medication therapy (Na supplementation, Vasopressin receptor antagonists)

How to calculate Na deficit?

TBW x (140-Na)

TBW = 0.6 x kg

How do we treat acute or symptomatic hyponatremia if it's been < 48 hours?

1-2mEq/L/hr

How do we treat chronic or asymptomatic hyponatremia if it's been > 48 hours?

0.5mEq/L/hr

What is the maximum correction of Na allowed?

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

total correction is over 48-72 hours

What is central pontine myelinolysis?

osmotic demyelination syndrome that's a neurologic problem related to overly rapid Na correction

What is the duration of central pontine myelinolysis?

1-6 days

What are ADRs of central pontine myelinolysis?

Seizures

Movement disorders

Pseudobulbar palsy

Quadriparesis

How to calculate free water deficit?

TBW x [(Na / 140mEq/L) - 1]

What is the treatment of hypovolemic hyponatremia?

replace half of the FW deficit in first 24 hours and the total in 48-72 hours

What is the first line for hypovolemic hyponatremia?

1/2 NS or D5W

What is used for hypovolemic hyponatremia for hemodynamic instability?

isotonic fluid for repletion FIRST

How frequently should Na be monitored during hypovolemic hyponatremia?

Q2-4H until asymptomatic

Q4-8H until normal range

How to estimate Na change after 1 L?

D5W = (0mEq/L - serum Na) / (TBW + 1)

1 L has NO Na

½ NS = (77mEq/L - serum Na) / (TBW + 1)

1 L has 77mEq of Na

True or False: overly rapid correction of hypovolemic hyponatremia can cause brain edema, herniation, or death

True

What causes hypertonic hyponatremia?

hyperglycemia or mannitol

How does hypertonic hyponatremia present?

Na appears low and decreasing about 1mEq for every 60mg/dL that the BG is above 200

What is the corrected Na equation?

Na + (BG-200) / 60

How do we treat hypertonic hyponatremia?

treat underlying cause and the Na should correct

What are the types of hypernatremia?

hypo, iso, hypervolemic

What are common causes of hypovolemic hypernatremia?

Vomiting

Diarrhea

NG suctioning

Osmotic diuresis

Burns

Sweat

How to treat hypovolemic hypernatremia?

replace volume with NS (isotonic) if hemodynamically unstable, then replace free water with hypotonic fluid

What are common causes of isovolemic hypernatremia?

central diabetes insipidus (DI): head trauma, tumors, infection which is caused by lack of antidiuretic hormone (ADH)

nephrogenic DI: electrolyte abnormalities, Li, Amp B, clozapine, renal disease, demeclocycline, gentamicin

How to treat CDI isovolemic hypernatremia?

desmopressin

How to treat NDI isovolemic hypernatremia?

thiazide or indomethacin and treat underlying cauase

What are common causes of hypervolemic hypernatremia?

hypertonic saline or Na bicarb soln infusion

How to terat hypervolemic hypernatremia?

sodium restriction and loop/thiazide diuretic

How does hypokalemia present?

Asymptomatic (frequently)

Muscle cramps

Weakness

EKG changes

What is first line for hypokalemia?

KCl >> K acetate

What dose is used for severe hypokalemia (symptoms + K < 2.5mEq/L)?

Slow IV therapy (< 10mEq/hr)

Unless cardiac monitored, central line, facility policy approval, and is medically necessary

K increases ~ 0.1 per 10mEq IV

When do we make K dose adjustments?

during renal impairment

What are precautions of hypokalemia treatment?

difficult to replace if there's low Mg

What are causes of hyperkalemia?

K-sparing diuretics

ACEi

NSAIDS

Increased intake (K supplementation, salt sub)

Metabolic acidosis

Trauma

Rhabdomyolysis

Hypoaldosteronism

What is pseduohyperkalemia?

hemolysis of blood sample that was contaminated with K infusion

How to manage hyperkalemia?

C A BIG K Drop

When do we use calcium IV for hyperkalemia?

to protect the heart

What are the rapid acting treatment options for hyperkalemia?

albuterol, bicarb, insulin/glucose

to drive K intracellularly

What are the treatment options for eliminating K during hyperkalemia?

LoKelma or diuretics/dialysis

What causes hypoMg?

Cisplatin

Aminoglycosides

Amphotericin

Diuretics

How does hypoMg present?

Asymptomatic (frequently)

Weakness

Cramps

Tremor

Hypocalcemia

Refractory hypokalemia

EKG Changes

What is the goal of Mg for patients with cardiac hx?

> 2

What are ADRs of PO treatment of hypoMg?

diarrhea (which can dec levels)

What is the dose of IV treatment of hypoMg?

1-2 g IV over ~60 min

levels increase 0.1 for every g infused

What are causes of hyperphosphatemia?

Renal impairment

Hypoparathyroidism

Increased intake

Drugs w/ P or bisphosphonates

How to treat benign hyperP?

no treatment needed usually

How to treat hyperP

phosphate binder or dialysis

What are Ca-based phosphate binders?

Ca carbonate, Ca acetate

What are non-Ca based phosphate binders?

Al-based antacid, sevelamer, lanthanum

How does hypoP present?

Muscle weakness

Diaphragm failure

Respiratory failure

N/V

Seizures

Coma

What is the treatment for mild hypoP (>2.6 or asymptomatic)?

high P diet (i.e., skim milk)

What is the treatment for moderate hypoP?

PO supplements

What is the treatment for severe hypoP (< 1.6 or resp failure or symptoms)?

injectable Na or Kphos

What goes with Na?

H2O

What is the most common ICU derangement?

K+

What is always dosed in mMol?

Phosphorous