1.9 - Intravenous Fluid Management Flashcards
How is normal water balance maintained?
- Water balance is accomplished in a normal, unhospitalized patient by responding to the body’s response to the fluid state.
- If there is a water loss (extreme sweating, increased insensible losses) there is an increase in serum sodium and osmolality.
- This stimulates thirst and an increased release of antidiuretic hormone (ADH). These changes will increase water intake and decreased urine output.
- Other sources of fluid ingestion include the water content of food particularly fruit and vegetables. A normal adult takes in approximately 1600 ml a day (there is great variation among adults) that comes from water ingestion, food and water from oxidation.
- They lose fluid from urine, skin, respiratory tract and stool.
What % of TBW is located in the intracellular fluid?
- Volume is approximately 60% of TBW.
- Because the majority of water is contained in the intracellular space, the loss of water alone does not typically result in the hemodynamic changes associated with volume depletion
What is the composition of the intracellular fluid in the body?
Composition:
- High concentration of potassium and phosphate ions
- Low concentration of sodium and bicarbonate ions
What % of TBW is located in the extracellular fluid?
Volume approximately 40% of TBW
What is the composition of the extracellular fluid in the body?
- Primarily sodium salts (NCl, NaHco3). 85-90% of total body sodium is extracellular. Changes in the body’s total Na content leads to contraction or expansion of the ECF that can lead to volume depletion or volume expansion respectively.
- Low concentrations of potassium and phosphates
What is the % volume and composition of the extravascular (interstitial) compartment of the ECF?
- Volume approximately 80% of ECF volume
- Composition is protein poor electrolyte solution of ECF
What is the % volume and composition of the intravascular compartment of the ECF?
- Volume approximately 20% of ECF volume
-
Composition: protein enriched electrolyte solution of ECF
- The compartment whose volume most closely reflects and best determines our cardiovascular function
Usefulness
- Compartment into which all therapeutic fluids are administered
- Distribution to all other body fluid spaces occurs by diffusion or transport into those compartments
What is the importance of body fluids?
Body fluids vital and essential to maintaining life. They help maintain our body temperature and shape of the cells. Fluids are involved in transporting nutrients, gases and wastes. The principle fluid in our body is water. The proper fluid balance is maintained by skin, lungs and kidneys. The two fluid compartments are separated by capillary walls and cell membranes.
What is fluid spacing?
A normal distribution of fluid in the body in both the intracellular and extracellular fluid compartments
What is second spacing?
Second spacing describes the excess accumulation of fluid in the interstitial spaces which we also call edema
What is third spacing?
- Third spacing occurs when fluid accumulates in areas that normally have no fluid or a minimal amount of fluid.
- You see this in ascites or edema associated with burns. If the third spacing is extreme the patient can present with extreme hypotension.
What are the 3 main reasons for IV fluid administration?
- ECF Volume depletion
- Body water (osmolality) adjustment or maintenance
- Delivery of therapeutic agents
What are the signs of ECF volume depletion?
- Look for the contributing causes including GI losses (Vomiting, diarrhea, NG suction) , urinary losses (diuretics, osmotic diuresis from hyperglycemia, contrast media), surface losses (heavy sweating if febrile; burns) respiratory tract (hyperventilation, non-humidified inhalation therapy), fluid sequestration (pancreatitis, ileus, burns), blood losses, other(inadequate oral or IV intake)
- Physical signs include: hypotension, tachycardia, postural hypotension, decreased jugular venous filling
- Invasive signs: include decreased CVP measurement and decreased pulmonary capillary wedge pressure
What are the signs of ECF volume excess?
- Physical signs: hypertension, internal jugular venous distention and edema. Edema can be peripheral, pulmonary or ascites.
- Invasive – increased CVP or PCWP
When and why is maintenance fluid started?
- In the presence of normal or near normal kidney function, maintenance fluid therapy is undertaken when the patient is not expected to be able to consume fluids for a prolonged period of time.
- These patients may be in a post-operative state or maintained on a ventilator
- The goals of maintenance fluid are to maintain adequate hydration and possibly to provide nutrition.
- The assessment of volume status is best learned at the bedside but assessment of lab values is important. In addition to sodium, look at the creatinine-to-urea ratio. A ratio higher than 12 is suggestive of volume depletion.