U of U PA School Dehydration, Hypovolemia, and Edema

What is dehydration?

Pure water loss with sodium retained

What does dehydration often coexist with?

Hypovolemia

How do cells change with dehydration?

Decreased in intracellular fluid volume causes decreased cell size

How do sodium and osmolarity levels change with dehydration?

Hyperosmolarity

Hypernatremia

What is hypovolemia?

Loss of water and salt equally

How do cells change size in hypovolemia?

Cells remain same size

What is edema?

Water and sodium retention

Expanding of interstitial fluid compartment

What is tonicity?

Relation of serum/ECF to ICF

What is hypertonic? How does water move?

Increased concentration of ions outside of cell

Water flows out of a cell without ions

What is isotonic?

ECF=ICF

What is hypotonic? How does water move?

Decreased concentration of ions outside cell

Water flows into cell without ions

What is osmolarity? Osmolality?

Osmolarity - Concentration of substance per liter

Osmolality - Concentration of substance per kilogram

Where is the majority of the bodies water?

ICF

What is found in abundance in ICF?

Potassium and proteins

What is found in abundance in ECF?

Sodium

What are the types of fluid in ECF?

Interstitial fluid - space between cells

Intravascular fluid - plasma in vasculature

What is the most important function of the kidney? How is this primarily done?

Volume control

Control of ECF via effective arterial blood volume (EABV)

What is effective arterial blood volume?

The volume of arterial blood that is effectively perfused to tissues and organs. This is not simply the total volume of blood in the body, but rather the portion of it that is effectively participating in the circulatory process to deliver oxygen and nutrients and remove waste products.

How does the kidney control ECF volume? How is it monitored?

Can change the concentration of sodium retained

Sensed with baroreceptors - sense renal perfusion

What do baroreceptors in the kidneys do?

Stimulate renin release via JG apparatus when low pressure to increase sodium conservation via aldosterone

ANP/BNP natriuretic factors release when high pressure to increase sodium excretion in kidney

How is concentration of ECF managed?

Via ADH by increasing water reabsorption and signaling thirst

Osmoreceptors

How do disorders of water reveal themselves? Disorders of sodium?

Disorders of water reveal themselves as sodium abnormalities

Disorders of sodium reveal themselves as volume abnormalities

What controls ICF?

Individual solute concentrations inside the cell managed by the cell and tonicity of ECF

Controls water to either move in or out of cell membrane

Where is most water loss from in dehydration?

ICF since it equilibrates across cell membrane

Backfills lost ECF

How much water can be absorbed via oral intake?

1 L/hr

How does dehydration present?

Thirst

Tachycardia

Decreased JVD and cap refill

Dry mucous membranes

Hypotension

What unique physical exam findings are indicative of dehydration?

+ passive leg raise

IVC collapse with inspiration

What lab findings are common with dehydration?

Hypernatremia

Serum osmolality >295 (280 normal)

What labs can help identify the cause of dehydration? (4)

BMP

UA

Lactic acid - increased in poor perfusion

Bicarb decreases

What is the treatment for dehydration?

Rehydration (oral or IV fluids)

Correcting electrolyte abnormalities

Identify and reverse causes

How fast can rehydration occur in dehydration?

If dehydration happened quickly (<48 hours) it can be corrected with 1-2L in 1st hour

Long-standing dehydration with hypernatremia needs slow correction

When is D5W used of NS?

If hypernatremia

What can be added to an IV once a patient beings urinating?

Potassium

How does hypovolemia present? (4)

Poor cardiac perfusion

AMS

Tachycardia

Thirst

When does hypovolemic shock occur? What is is?

If 30%+ of EABV is lost

Global tissue hypoperfusion leads to cellular hypoxia and dysfunction

What can oliguria reveal? What levels indicate oliguria

Earliest sign of a kidney injury

<20 ml/hr or 500 ml/day

How is hypovolemia treated?

Increase tissue perfusion

If hemorrhagic - FFP, platelets, and RBCs

If non-hemorrhagic - NS/LR.albumin in boluses of 30 ml/kg

What is anasarca?

Edema effecting entire body

What causes edema?

Increases in sodium leads to increases in ECF

Hypoalbuminemia

Mechanical obstruction and local factors

How does increases in sodium leading to increases in ECF lead to edema?

Renal sodium retention due to poor renal perfusion triggering aldosterone leads to increase in intravascular hydrostatic pressure leading to capillary leak and increased interstitial fluid

How does hypoalbuminemia leading to edema? What can cause it?

Decreased intravascular oncotic forces leading to capillary lea interstitial tissues

Cirrhosis

Nephrotic syndrome

Kwashiorkor - severe protein malnutrition and bilateral extremity swelling

How does mechanical obstruction and local factors lead to edema? What can cause it?

Obstruction leads to impaired venous flow and increased osmotic forces causing capillary leak

SCV syndrome

DVT

Lymphedema

What are the types of edema? (6)

Peripheral - rarely dangerous

Pulmonary - very dangerous

Ascites

Scleral

Periorbital

Cerebral - very dangerous

What can cause peripheral edema? (4)

CHF

Cirrhosis

Nephrotic syndrome

Amlodipine

Wha is the treatment for peripheral edema? (4)

Leg elevation

Diuretics

Decreased sodium intake

Compression hose

What causes hemosiderin staining?

Heme/iron leaks out of capillary into tissue due to chronic increased venous pressure

What is pulmonary edema?

Fluid back up and collection in alveoli

How does pulmonary edema present?

Dyspnea and orthopnea

Hemosiderin laden macrophages in sputum

What is the treatment for pulmonary edema?

ABCs

Diuretics or dialysis

Therapeutic thoracentesis if moderate to large pleural effusion

What is ascites?

Cirrhosis complication with fluid accumulation in peritoneal cavity

What causes ascites?

Portal venous hypertension plus concurrent inability of liver to synthesize albumin

How does ascites present? (5)

Fluid wave sign

Hemorrhoids

Pleural effusion

Esophageal varicies

Caput medusa

What test can help diagnose ascites?

Peritoneal ultrasound

What is the treatment for ascites?

Paracentesis

Can add IV albumin to stop intravascular shift into peritoneum causing hypotension and cardiac arrest