Parenteral Therapy: Fluids and Electrolytes

• Unit 2 is about Parenteral Therapy
• The objective is to draw conclusions regarding the administration of parenteral therapy.
• An overview of signs and symptoms of fluid deficiencies.
• An overview of types of fluids used to correct fluid deficiencies.
• An overview of intravenous infusion principles.

Fluids, Electrolytes and Basic Biology

• Water comprises 60% of the human body weight.
• Intracellular fluid is the portion of body fluid inside the cells and makes up 2/3 of all body water.
• Extracellular fluid is the fluid outside the body's cells and accounts for the remaining 1/3 of total body water.
• Intravascular fluid is 25% of extravascular water and is fluid within the circulatory system.
• Interstitial Fluid is 75% of extravascular water and is fluid between cells.
• Electrolytes are substances or charged particles referred to as ions.
• Cations are positively charged ions such as Sodium (Na), Potassium (K), Calcium (Ca), and Magnesium (Mg).
• Anions are negatively charged ions such as Chloride (Cl), Bicarbonate (HCO3), and Phosphate (HPO4).
• Osmosis and Diffusion occur in semi-permeable membranes or specialized biological structures such as the cell membrane.
• A solute is a substance which dissolves into a solvent.
• A solvent is a liquid that dissolves the solute.
• Isotonic fluids have the same solute concentration as the body fluids.
• Hypotonic fluids have a lower solute concentration than body fluids.
• Hypertonic fluids have a higher solute concentration than body fluids.
• Osmosis is the movement of a solvent (water) across a semi-permeable membrane from an area of lesser solute concentration to an area of higher solute concentration.
• The pressure created by the movement is called osmotic pressure.

History and Vital Signs

• Tachycardia and tachypnea are compensatory signs of moderate dehydration.
• Hypotension is more evident of hypovolemic shock.
• Additional signs of dehydration include listlessness, dry or sticky mucus membranes, delayed capillary refill, decreased skin turgor, diminished pulses, and neurologic dysfunction such as lethargy or seizures.

Intravenous Fluids

• Colloids contain larger molecular weight particles and have plasma oncotic pressures similar to normal plasma proteins.
• Colloids draw extravascular fluid into the intravascular space.
• Colloids remain in the intravascular space for a greater period of time.
• Colloid fluids have limited use in clinical practice.
• Colloid fluid examples are Albumin, Fresh Frozen Plasma (FFP), Dextran, Hetastarch (Hextend).
• Crystalloids can be Isotonic solutions that mimic normal body fluids.
• Crystalloids can be Hypertonic Solutions, these contain higher solute (sodium) concentration than normal body fluids.
• The entire volume of fluid does not remain in the intravascular space when using Isotonic solutions.
• Osmotic pressure only keeps isotonic fluids in the extracellular space.
• Water moves freely between intravascular and interstitial spaces, a large portion of volume (~75%).
• Isotonic solutions are the preferred fluid for hypovolemia/dehydration resuscitation.
• Examples of Isotonic solutions include Lactated Ringer (LR) and Normal Saline (NS).
• There is no clear research to suggest that either Normal Saline or Lactated Ringers is superior to the other.
• Hypertonic Solutions have a greater osmolarity than extracellular fluids.
• Osmotic pressure drives fluids into intravascular space.
• Hypertonic Solutions are used in the treatment of increased intracranial pressure and severe hyponatremia.