NURS601 Week 1 Concept 2: Fluid shift - Dehydration/Hypovolemic shock
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The other end of the spectrum from oedema
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Occurs when water loss exceeds water intake over a period of time and the body is in a negative balance
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Caused by decrease of ECF volume - loss of Na+ containing fluid from the body
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Causes include: vomiting, diarrhea, haemorrhage, burns, profuse sweating, water deprivation, and diuretic abuse
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Class I
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Class II
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Class III
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Class IV
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% Blood loss
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Up to 15%
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15-30%
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30-40%
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>40%
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HR
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Normal
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Mild tachycardia
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Moderate tachycardia
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Severe tachycardia
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BP
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Normal
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Normal to decreased
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Decreased
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Decreased
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RR
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Normal
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Mild tachypnea
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Moderate tachypnea
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Severe tachypnea
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Urine output
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Normal
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0.5-1mL/kg/h (min. goal)
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0.25-0.4mL/kg/h (markedly decreased
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Negligible
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Mental status
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Slightly anxious
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Mildly anxious
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Anxious/confused
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Confused/lethargic
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Fluid replacement
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Crystalloid
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Crystalloid
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Crystalloid & blood
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Crystalloid & blood
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Obligatory fluid loss
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Urine (obligatory), Feces, Cutaneous transpiration, Sweat, Expired air
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Totals to 1500mL
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Required for normal function and health
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Facilitative fluid loss
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Urine (facilitative)
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Totals 1000mL
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The ability to adapt to various situations/conditions
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A patient should be urinating every 6 hours
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Absolute minimum urine output is 30cc/hour
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Fluid intake
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Performed water (food & drink)
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Totals 2300mL
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Vital signs
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Pathophysiological rationale
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Increased HR
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SNS increases HR to maintain CO despite decrease in SV to support perfusion of O2 to major organs and tissues
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Decreased BP
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Decrease in circulating volume leads to decreased venous return to the heart, decreased preload, decreased SV and decreased CO and compensation for vasoconstriction no longer effective
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Skin is pale, cool and clammy
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Body is attempting to maintain critical systems, so tissue perfusion to the skin is reduced
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Occurs when there is inadequate intravascular fluid volume which leads to inadequate tissue perfusion
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Manifestations:
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Decreased blood pressure
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Increased heart rate, respiratory rate
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Pollor, cool, and clammy skin
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Decreased urine output
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Anxiety, confusion, Agitation
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Average adult blood volume for a female is 4-5L of blood and 5-6L for a male
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Approximately 8% of your body weight is blood
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Average blood volume in a 70kg person is 5.5L, so mild loss = 825mL, Class II loss is 825mL-1.65L, and class III is 1.65-2.2L
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Crystalloids
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Equal to body fluid
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Keeps fluid in the intravascular volume without causing a fluid shift from one compartment to the other
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Usually used for replacement or maintenance fluids:
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Plasma-lyte
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Normal saline
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D5W
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Lactated ringers
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An isotonic solution, in a nutshell, is a balanced water-solute concentration
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When a solution is isotonic, it is at equilibrium
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Plasma expanders (Colloids):
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Albumin
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Gelofusine
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Colloids are gelatinous solutions that maintain a high osmotic pressure in blood
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Particles in the colloids are too large to pass semi-permeable membranes such as capillary membranes, so colloids stay in the intravascular spaces longer than crystalloids
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