Drugs for Fluid and Electrolyte Imbalances, and Acid–Base Disorders Flashcards
Body Fluid Compartments
- Continuous exchange of fluids across Semipermeable Membranes between Intracellular & Extracellular Fluid compartments (Large molecules and those that are ionised are less able to cross membranes)
Indications for IV Therapy
- Imbalances of
1. Body Fluids
2. Electrolytes
3. Acid-Base
Definition of Osmolality
A colligative property of solutions that depends on the number of dissolved particles/solutes in the solution in 1kg (1L) of fluid
- Average osmolality is 275-295mOsm/kg
What does changes in Osmolality do?
- If there are any changes in the Osmolality, it can cause water to more into different/another compartment
(Sodium is the greatest contributor, and is controlled by Hormone Aldosterone)
How to regulate Fluid Intake and Output?
- Output
- The kidneys regulate it with the Renin-Angiotensin-Aldosterone System (RAAS) and Antidiuretic Hormone (ADH) - Input
- Achieved through “Complex Mechanisms”
- Most important regulator of Fluid Intake is “Thirst Mechanism”
2 types of Fluid Balance Disorders
- Deficient Fluid Balance Disorders
- Can cause Dehydration and Shock
- Treated with Oral or Intravenous Fluids
- IV Therapy Fluid helps to maintain Blood Volume and Support Blood Pressure - Excess Fluid Balance Disorders
- Treated with Diuretics: Helps to reduce fluid buildup in the body (By helping the kidneys remove salt and water through urine)
How does IV Fluid Therapy help with Deficient Fluid Balance?
- It replaces the fluid and electrolytes in the body by using Crystalloids and Colloids
5 Main Causes of Water and Electrolyte Loss
- Loss of GI Fluids due to vomiting, diarrhoea, chronic laxative use or GI suctioning
- Excessive sweating during hot weather, athletic activities, or prolonged fever
- Severe burns
- Haemorrhage (Loss of blood from damaged blood vessels)
- Excessive Diuresis (Increase in amount of Urine) due to Diuretic Therapy or Uncontrolled Diabetes Ketoacidosis
Crystalloids
- Intravenous (IV) Solutions containing electrolytes, designed to closely mimic the body’s Extracellular Fluid (ECF), they replace Lost Fluids and promote Urine output
Example of IV Fluids (Solutions that move out of the plasma and into the interstitial spaces and intracellular fluid, depending on tonicity)
- Isotonic Solutions (e.g. 0.9% NaCl)
- Expands plasma volume without causing fluid shifts between compartments
- Indicated for treatment of fluid loss due to vomiting, diarrhoea or surgical procedures, especially when there is low BP - Hypertonic Solutions (e.g. 3% NaCl)
- Draws water cells and tissues into plasma, useful for treating Cerebral Oedema
- Indicated for the release of Cellular Oedema - Hypotonic Solutions (e.g. 0.45% NaCl)
- Moves water from the plasma into cells and tissues, indicated for Hypernatremia and Cellular Dehydration
Adverse Effects of IV Solutions
- For Isotonic/Hypertonic Solutions
- Fluid Overload (Excessive expansion of IV Compartments) - For Hypotonic Solutions
- Hypotension (Depletion of IV Compartment) and Peripheral Oedema (Too much expansion of Intracellular Compartment)
Colloids
- Contain large molecules, such as proteins or starches, that are too large to easily pass through Capillary Membranes, keeping them in Intravascular Space
- These solutions rapidly expand plasma volume by drawing water from intracellular fluid and interstitial space into plasma, increasing Osmotic Pressure
Selected Colloid Solutions
- Normal Serum Albumin (Most Common)
- Dextran (A Synthetic Polysaccharide), Infusion can double the plasma volume within a few minutes
- Hetastarch (A Synthetic Colloid), similar to 5% Albumin with extended duration of action
Adverse Effects of Colloids
- Usually Safe
- May caused Altered Coagulation (Disruptions in the body’s ability to control blood clotting), resulting in Bleeding
- (Rarely) Dextran Therapy causes Anaphylaxis or Renal Failure
Blood Products
- Only class of fluids that carries Oxygen
- Increases Tissue Oxygenation
- Increases Plasma Volume