260-Fluid and electrolyts balance( test 3) (1).docx

260-Fluid and electrolyts balance( test 3) (1).docx - Fluid...

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Fluid, Electrolytes and Acid-Base Homeostasis Fluid Compartments Intracellular fluid : fluid inside the cells (accounts for 2/3 of body water) Extracellular fluid: fluid outside the cells (accounts for 1/3 of body water) •Interstitial fluid : between the cells (accounts for 80% of extracellular fluid) •Intravascular fluid : inside the blood vessels (accounts for 20% of extracellular fluid) Transcellular fluid (accounts for 1% of extracellular fluid) and includes: -Fluids in the peritoneal cavity, pleural and pericardial spaces. -Cerebrospinal fluid -Fluid in joint spaces, lymph system, eyes and GI tract. Intracellular fluid - Rich in Potassium, Magnesium, Phosphates and proteins. Extracellular fluid – Rich in Sodium, Chloride, Bicarbonate. Fluid Movement •The movement of water depends on Hydrostatic (push) and Osmotic ( pull) pressures. Hydrostatic pressure = Blood pressure Osmotic pressure = Proteins and electrolytes (solutes) contribute to the osmotic pressure of a fluid. •At the arteriolar end of the capillary, the blood’s hydrostatic pressure (blood pressure) exceeds the opposing interstitial hydrostatic pressure thereby moving (pushing) fluid out of the intravascular compartment and into the interstitial compartment to meet cellular needs. •At the venous end of the capillary, the blood’s hydrostatic pressure is decreased and the osmotic pressure exceeds the hydrostatic pressure (blood pressure), thereby moving fluid from the interstitial compartment to the intravascular compartment to aid in the exchange of waste products to be excreted. Tonicity refers to the osmotic pressure (movement of water) of two solutions separated by a semipermeable membrane. Isotonic: Equal solute concentrations, causes no fluid shifts (0.9% saline or Lactated Ringer’s) Hypotonic: Lower solute concentrations, causing fluids to shift from the intravascular compartment to the intracellular space. (0.45% saline) Hypertonic: higher solute concentrations, causing fluids to shift from the interstitial space to the intravascular space ( 5% dextrose in 0.9% saline, or 3% saline) Fluid Sources •Oral intake (Including Enteric Tube feedings) •Intravenous solutions Fluid Losses • Urine • Feces •Insensible losses (Unmeasurable losses – perspiration, breathing, talking, coughing and mechanical ventilation – approximately 400- 500 ml/day) Fluid intake and Fluid output is balanced through several mechanisms Thirst mechanism is triggered in the hypothalamus to increase oral intake in response to decreased fluid volume and increased osmolarity (solute concentration). Antidiuretic hormone (ADH) is released from the posterior pituitary gland in times of decreased fluid volume and increased osmolarity. ADH promotes reabsorption of water in the kidneys.
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  • Summer '17
  • pH, Bicarbonate, Arterial blood gas

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