Week 5 - Osmolality Flashcards
(29 cards)
What is osmolality?
-indicator of water balance (concentration)
What is the range for N Plasma Osmolality?
- 285-295 mOsm/kg
What does it mean if plasma osmolality is higher than >295?
water deficit - too little water or too much solute
What does it mean if plasma osmolality is less than 285?
Water excess - too little solute or too much water
Cells are affected by osmolality of fluids around them. What osmolality do isotonic fluids have? (2)
- equal osmolality
aka neutral concentration between ICF and ECF
What osmolality do hypertonic fluids have?
- have higher osmolality (shrinks cells)
What osmolality do hypotonic fluids have?
- have lower osmolality (swell cells)
Fluid shifts diagram*
Which area of the brain is responsible for regulation of water balance?
- hypothalamus-pituitary gland in brain
What is the mechanism in which the hypothalamus regulates water balance? (4)
- Hypothalamus osmoreceptors sense increased osmolality
- too many particles, not enough fluid - Thirst triggered (decreased in older adult)
- ADH released from pituitary gland
- in kidney, free water absorption (not Na) - ADH release can be triggered by increased plasma osmolality, stress, nausea, nicotine, and morphine
Why happens to osmolality if you are dehydrated?
- osmolality goes up and thirst is triggered
Must know RAAS, in perfusion unit
ok
What is aldosterone’s role in the kidneys?
- stimulates kidneys to reabsorb water and sodium
What is the role of ADH? (2)
- kidneys reabsorb more water, not Na+
- This dilutes our blood so the Na+ concentration drops
What occurs in the GI regulation of water? (2)
Intake: source of new water for the body
Output: Diarrhea and vomiting may lead to excessive water loss and electrolyte loss
In lecture, hypokalemia and decreased water
What occurs in the genitourinary regulation of water? (2)
- Output: Urine
- Renal excretion provides largest output
What is insensible water loss? (3)
- water loss from breathing and insensible perspiration (water only)
- excessive sweating (sensible perspiration) may lead to excessive water and electrolyte loss (fever, hot environment)
- water used in metabolic processes
How much water is lost per day with insensible water loss?
900 mL a day
What are age-related considerations that increase the risk of imbalances? (5)
- reduced renal function
- reduced hormone regulation
- reduced thirst trigger
- reduced temperature regulation
- impaired functional and cognitive ability may interfere with oral consumption of water
What are nursing implementations for intake and output of the GI and GU system? (3)
- use of 24h record of I&O
- types of fluid intake: drinking, eating, IVs, GI tubes
- Types of fluid output: urine, vomit, diarrhea, sweat, breathing
What are nursing implementations for daily weight measurements? (3)
- accurate daily weight estimates volume status
- rapid increase of 1kg body weight approximates 1000 mL of fluid retention
- obtained under standardized conditions (same time everyday with the same clothes and scale)
What are the sources of fluid and sodium for oral intake? (4)
- “free” water (“tap” water)
- Electrolyte-replacement beverages
- Food and other beverages
- Caffeine beverages
How is free water a source of fluid and sodium? (3)
- no significant Na
- will provide water to dilute plasma Na
- if un-needed, kidneys will excrete excess water
How are electrolyte-replacement beverages like sports drinks or pedialyte, a source of fluid and sodium?
- provides electrolytes commonly lost through sweat, vomiting, diarrhea as well as water
