IV Fluids

Isotonic Solutions:

• 0.9% Saline (aka Normal Saline)
• Normal Saline is given to increase the amount of fluid in the blood vessels (intravascular space), without significantly changing the balance of electrolytes in the body.  This is useful for making sure a patient remains in a well-hydrated state of homeostasis.  Normal Saline also happens to be the only IV solution that can be infused at the same time as a blood product.
• Use to expand volume, dilute medications, and to keep vein open.
• Ringer’s Solution
• Lactated Ringers
• Ringer’s and Lactated Ringer’s Solutions contain a wider variety of electrolytes than Normal Saline, which makes them even more similar to what’s found in blood plasma.
• Use for fluid resuscitation
• 5% Dextrose in 0.225% Saline
• 5% Dextrose in Water (D5W) 
• The Isotonic Dextrose solutions have the same goal as the hypertonic dextrose solutions; to provide extra calories to the patient. Dextrose is just a sugar, which can be easily absorbed by the body and turned into energy.
• 5% Dextrose in Water is a special case. Although it is technically isotonic, it acts upon the body as if it is hypotonic as glucose is metabolized.

Hypotonic Solutions: contain less solute than blood, which causes water to want to leave the hypotonic solution and enter an area that has a higher concentration of solute via osmosis.  When discussing IV fluids, that usually means that the water will want to leave the intravascular space and enter Red Blood Cells (RBCs).

• 0.45% Saline
• the most common reason to give 0.45% Saline is for true dehydration, which is when the body has lost water, without losing any electrolytes (this is different from fluid volume deficit, when the body loses BOTH water AND electrolytes).  In dehydration, the body already has a normal amount of electrolytes, so there is no need to provide more in the IV solution.  The patient simply needs some of their water replaced!
• *5% Dextrose in Water 
• this is technically isotonic, but once the dextrose is absorbed then it acts on the body as if it was hypotonic

Hypertonic Solutions: has a higher solute to solvent ratio than blood does. Blood basically becomes our definition of what “Isotonic” means. Useful for a patient who needs electrolytes but is already on fluid overload, such as in Heart Failure or severe edema.  That way you are providing the patient with needed electrolytes, but minimizing the extra water that their condition doesn’t get worse.

• 3% Saline
• typically used to treat severe cases of hyponatremia (low sodium).  This makes sense because if your blood stream has become hypotonic and it’s supposed to be isotonic, then adding a hypertonic solution will help increase the electrolyte imbalance back to normal levels. 
• Caution: You need to infuse the IV solution very slowly and cautiously, and watch the patient closely for any evidence of intravascular overload (too much fluid in the blood vessels).  This could be increased blood pressure, pulmonary edema (fluid in the lungs), or even hypernatremia (high sodium).
• 10% Dextrose in Water
• 5% Dextrose in 0.45% Saline
• 5% Dextrose in 0.9% Saline
• These three dextrose solutions are primarily used for the purpose of providing the patient with extra calories.

Heart failure

Preload is the amount of blood returning to the heart from the body via the Vena Cava.
After load is the amount of resistance the heart must pump against to eject blood from the heart into the body.

Cardiac output = SV X R stroke volume times rate is the amount of blood circulated through the body in a minute.

Stroke volume is the amount of blood pump from each ventricle during contraction
Starling’s Law of the Heart reflects the elasticity creating force of cardiac cells to contract. As heart goes into failure the cells are stretch and dilated and so loose the ability to contract with efficient force. Think of a rubber band, the more it is stretch and dilated the weaker it is and loses its recoil ability. This is the same physiology seen in heart failure.

How do the baroreceptors in the carotid arch influence hormone secretion in heart failure?
Baroreceptors sense the pressure with which the blood as ejected and fills the aorta. This is reflected in the blood pressure. If the pressure is low, word is sent out to secrete hormones of the body to contract the arteries, and retain fluid to fill the arteries thus raising the blood pressure.

Explain the role of these hormones in heart failure:
Adrenalin – causes vasoconstriction of blood vessels leading to hypertension
Aldosterone – binds with sodium to retain water and cause the symptom of edema
Antidiuretic Hormone closes the epithelial cells in the distal kidney tubule and thereby retains water that adds to the symptoms of hypertension and edema.
Renin is secreted by the juxtaglomulerus of the kidney in response to the request of the baroreceptors in the aortic arch. Renin then goes to the lungs to initiate the formation of Angiotensin I and II that will add to hypertension.
Angiotensin II goes to the cardiac cells to stimulate remodeling or the formation of immature cardiac cells that are not able to contract with the force necessary to eject the volume of blood necessary for adequate stroke volume, thus the cardiac output remains low and the heart continues into failure.

What is the physiology that causes the primary symptoms of dyspnea, edema, and fatigue in heart failure?
Dyspnea comes from lungs trying to compensate for decrease perfusion in alveoli.
Fatigue results from lack of oxygen and build up of carbon dioxide in cells as sluggish circulation cause tissues to not have normal cleaning and perfusion.
Edema is a safety mechanism to third space fluid and decrease the work load of the heart pumping blood.

Why does PND paroxysmal nocturnal dyspnea occur primarily at night?
Edema fluid held in the legs during the day while a person is sitting, returns to the general circulation when the person is horizontal in bed. This fluid causes overload and drowning sensation leading to symptoms of severe dyspnea, air hunger and pulmonary edema.

Contrast the etiology of left and right sided heart failure.
Left sided heart failure occurs after MI, hypertension, or other causes that weaken the pumping ability of the left ventricle. Occurs in response to resistance of blood pumping in afterload. Low blood flow over the carotid baroreceptors triggers the compensatory hormone mechanisms or Adrenalin, Aldosterone, ADH and Renin. Treatment is medication to reduce afterload or intraortic balloon pump is person goes into shock.

Right sided heart failure deals with preload. The edema fluid is trying to return to the already full distended right ventricle.

Think about it … blood can’t be pumped out to the body or lungs so ventricles are full of blood. Where is new blood trying to ender the heart going to go? It backs up so jugular veins distend and A/V waves can be seen when the heart contracts. The body employs safety measure of third spacing reducing the flow of blood back to the heart by pushing it into the tissues by increased hydrostatic pressure. This is similar to when a river is full of water; the water overflows the banks and seeps into the ground. Same thing in heart failure, the ground is the tissues of the body (pulmonary edema of lungs, ascites from the liver, and pitting edema in the legs.

Differentiate Cor Pulmonale from right sided heart failure.
Right sided heart failure occurs with MI, Cor Pulmonale occurs from COPD as heart has to pump against the resistance of lung tissue pathology.

Comparison of heart, kidney, and liver failure symptoms

Symptom	heart	kidney	liver
Ascitesedema	ADH, renin, Aldosterone secretion, venous congestion into right ventricleIncreased hydrostatic pressure	ADH, renin, Aldosterone secretion, venous congestionLack of output	Decreased albuminPortal hypertension, increased capillary pressure, obstruction of venous flow
hypertension	ADH, renin, Aldosterone secretion, arterial congestion, edema, arterial constriction	ADH, renin, Aldosterone secretion, fluid retention	Liver does not metabolize aldosterone
breath		acetone	Fetor hepaticus
Change sensorium	Decreased circulation and oxygen	Increased nitrogen and acidosis	Ammonia and nitrogen
hepatomegaly	Venous engorgement		Scar tissue, inflammation
puritis		Uric acid crystals, uremic frost	Bile salts and jaundice
anemia	Low hemoglobin and oxygen carrying power	Lack of erythropoietin	Inability to metabolize hemoglobin and clotting factors
Diagnostic labs	H &H, BNP, Aldosterone	BUN, creatinine, electrolytes Creatinine clearance	AST, ALT, PT, BUN, A/G ratio
acidosis	Decrease CO, inadequate tissue perfusion, decrease oxygen exchange in cells, lactic acidosis	Hydrogen retention
anorexia	Venous stasis in the abdominal organs, ascites	Toxins, ammonia	Ascites, toxins
diet	DASH, low sodium, cholesterol, low triglycerides, and fluid restriction	Low sodium, potassium, protein, fluid restriction, high carbohydrate	High carbohydrate, low protein, low sodium
hepatomegaly	venous engorgement		Inflammation, scar tissue
Treatments	diuretics	dialysis	Diuretics, SPA

Hypovolemia & Hypervolemia tx

Hypovolemia:

• Oral rehydration, 1500mL/day
• Carbohydrate/electrolyte solution such as sports drink, gingerale, pedialyte
• IV theraphy
• Isotonic solutions are used to expand plasma volume preferably LR
• 0.45% w/ or w/out added electrolytes for maintenance

Hypervolemia:

• Diuretics = loop, thiazide-type, potassium sparing i.e lasix, HCTZ, aldactone
• Restrict fluid intake
• Restrict sodium intake
• Too much water retention can lead to cerebral edema or pulmonary edema.

Hypernatremia tx

• Oral or IV water replacement
• Hypotonic IV fluids such as 0.45% NaCl solution or
• 5% Dextrose in water (isotonic solution but becomes hypotonic when glucose is metabolized)
• Diuretics may be given to increase sodium excretion (for excess sodium)
• Restrict sodium in diet
• Give isotonic solutions