Fluids and Electrolytes 1 Flashcards
What does water loss lead to?
Water loss leads to increase in serum sodium and osmolality resulting in a stimulation of thirst and increased release ADH (acts on the kidneys)
In normal people this leads to an increase in water intake and reduced water excretion.
What is the minimum water intake required to maintain homeostasis (assuming normal temp and renal concentrating ability)?
500ml/d which would yield 500ml urine
What is the minimal obligatory water intake for normal adults?
Normal adults are considered to have a minimal obligatory water intake of 1600 mL/day
Ingested water- 500mL
Water in food- 800mL
Water from oxidation – 300mL
What is normal water loss in healthy adults and where does it come from?
Normal healthy individuals have obligatory water loss of 2.5-3L/24hr Loss from urine 500mL Skin- 500mL Respiratory Tract- 400mL Stool- 200mL
What are the factors affecting fluid requirements?
Age
Environmental Factors
Conditions with increased fluid needs
Conditions with decreased fluid need
What are the age factors affecting fluid requirements?
Neonates with larger fluid needs
Geriatric patients with smaller fluid needs
What are the environmental factors affecting fluid requirements?
Ambient temperature
Neonates- radiant warmers, ultraviolet phototherapy
What are the conditions with increased fluid needs that affect fluid requirements?
Burns, diarrhea, dehydration, fever
What are the conditions with decreased fluid needs that affect fluid requirements?
CHF, renal failure, iatrogenic fluid overload, mechanical ventilation
What determines the distribution of water between ECF and ICF compartments?
To tonicity (osmolality) of ECF
What is tonicity determined by?
The concentrations of effective osmoles in the ECF
What are effective osmoles?
Solutes that can not move freely across cell membranes (require active transport)
What is the main “effective osmole” in ECF?
Sodium
What reflects osmolality of body water?
Plasma osmolality
Unless abnormality of sodium and fluid resulting in redistribution between ICF and ECF
Rank the fluid compartments from most to least percentage of body water considering interstitial fluid, plasma, and intracellular fluid.
Intracellular fluid > Interstitial fluid > Plasma
What are the low pressure systems and what do they do?
Atria and pulmonary vasculature
In response to decreased wall stress (sign of decreased intravascular volume- in the heart and lungs) signal hypothalamus to release antidiuretic hormone (ADH) or vasopressin, while increased stress results in secretion of natriuretic peptide
What are the high pressure systems and what do they do?
Baroreceptors in aortic arch, carotid sinus, and juxtaglomerular apparatus
Stimulates the Renin-Angiotensin-Aldosterone system
What is renin released by?
Response of juxtaglomerular appraratus to decreased arteriolar wall of tension
Beta-1 innervation of juxtaglomerular apparatus
Tubuloglomerular feedback that senses distal nephron sodium release
What cleaves angiotenson to generate angiotensin I?
Renin
What cleaves angiotensin I to generate angiotensin II?
Angiotensin I is then cleaved by angiotensin converting enzyme (ACE) to Angiotensin II
Stimulation of Aldosterone secretion by adrenal gland
Increased reabsorption of NaCl from proximal tubule
Central stimulation of thirst and secretion of ADH
Arteriolar vasoconstriction
What type of solution is D5W?
Hypotonic
What type of solution is 1/2 NS (0.45%)?
Hypotonic
What type of solution is NS (0.9%)?
Isotonic
What type of solution is 3% saline?
Hypertonic