FINAL EXAM ABG and K, Na and Ca Flashcards
1
Q
Arterial Blood Gases: ABG’s
A
- pH 7.35 to 7.45
- PaCO2 35 to 45 mm Hg
- HCO3ˉ 22 to 26 mEq/L (assumed average values for ABG interpretation)
- PaO2 80 to 100 mm Hg
- Oxygen saturation >94%
- Base excess/deficit ±2 mEq/L
2
Q
Maintaining Acid–Base Balance
A
- Normal plasma pH is 7.35 to 7.45: hydrogen ion concentration
- Major extracellular fluid buffer system; bicarbonate-carbonic acid buffer system
- Kidneys regulate bicarbonate in ECF
- Lungs under the control of the medulla regulate CO2 and, therefore, carbonic acid in ECF
3
Q
Metabolic Acidosis: Base bicarbonate deficit
A
- Characterized by acidosis (increased H+ concentration) and a low plasma bicarbonate concentration (<22 mEq/L)
- Causes are often GI loss of bicarbonate or accumulation of fixed acid (lactic acidosis, ketoacidosis, etc.)
- Manifestations are varied but include tachypnea, confusion, hypotension, and decreased cardiac output
- Treatment focuses on the underlying metabolic disorder
4
Q
Metabolic Alkalosis:
base bicarbonate excess
A
- pH >7.45 with high bicarbonate >26 mEq/L
- Commonly due to vomiting or gastric suction; may be caused by medications, long-term diuretic use. May accompany hypokalemia.
MANIFESTATIONS
- symptoms related to decreased calcium
- respiratory depression
- tachycardia
- symptoms of hypokalemia
Correct underlying disorder, supply chloride to allow excretion of excess bicarbonate, and restore fluid volume with sodium chloride solutions
5
Q
Respiratory Acidosis: Carbonic acid excess
A
- pH is <7.35 and PaCO2 is >45 mm Hg
- Always due to inadequate excretion of CO2 with inadequate ventilation
- With chronic respiratory acidosis, the body may compensate and may be asymptomatic; symptoms may include a suddenly increased pulse, respiratory rate, and BP; mental changes; feeling of fullness in the head
- Potential increased intracranial pressure
- Treatment is aimed at improving ventilation
6
Q
Respiratory Alkalosis
A
- pH >7.45 and PaCO2 <35 mm Hg
- Always due to hyperventilation
- Signs consist of lightheadedness due to vasoconstriction and decreased cerebral blood flow, inability to concentrate, numbness and tingling from decreased calcium ionization, tinnitus, and sometimes loss of consciousness
- Correct cause of hyperventilation
7
Q
SODIUM: Na+ [135-145] mEq/L
A
FUNCTION: Principal regulator of ECF volume
- Common electrolyte imbalance in the elderly
- Caused by Na+ losses or Water Gains
- Symptoms are related to cellular swelling
- Manifested FIRST in the CNS as excess water lowers plasma osmolality and shifts fluid into brain cells. Causes poor skin turgor, dry mucosa, headache, decreased salivation, decreased blood pressure, nausea, abdominal cramping, neurologic changes
8
Q
HYPONATREMIA: Na+ < 135 mEq/L
A
Causes: adrenal insufficiency, water intoxication, SIADH or losses by vomiting, diarrhea, sweating, diuretics
Caused by Na+ losses or Water Gains
MEDICAL MANAGEMENT:
- water restriction, sodium replacement, treat underlying.
- If seizures develop, small infusions of 3.0 % - 5% NaCl (hypertonic saline solution) are infused to restore normal level. Must be infused slowly.
- Too rapid correction of sodium balance can cause irreversible neurological damage.
- Provide nutritional counseling and increase foods containing sodium.
NURSING MANAGEMENT
- Check for increased BP and respiratory crackles
- Check for bounding pulses, bulging neck veins
- Monitor for changes in sensorium and signs and symptoms of cerebral edema
- Check for pitting edema with fluid excess
- Monitor 24 hour Intake and Output record
- Check and compare daily weights
- Check Urine specific Gravity–< 1.010. Urine should be a light straw color without sediment.
9
Q
HYPERNATREMIA = Na+ > 145 m/Eq/L
A
CAUSED BY:
Na+ Gain
- Excess IV hypertonic solutions – NaCl 3%, 5%.
- Excess IV Sodium Bicarbonate
- Excess isotonic 0.9% NaCl
- Primary hyper-aldosteronism
- Saltwater near-drowning
Water Loss (Na+ Concentration)
- Increased insensible water loss or perspiration
- High fever, heatstroke
- Diabetes Insipidus
- Osmotic diuresis
10
Q
HYPERNATREMIA = Na+ > 145 m/Eq/L
TREATMENT
A
MANIFESTATIONS:
- thirst
- elevated temperature
- dry, swollen tongue
- sticky mucosa
- neurologic symptoms
- restlessness; weakness
Goal of treatment for Na+ excess is to dilute the concentration of Na+ with salt-free IVF (D5%W), or hypotonic solution (0.45% NS), and administer diuretics to promote excretion of excess Na+.
- Reduce serum Na+ levels SLOWLY to prevent a rapid shift of water back into the cells.
- If the correction is too rapid it may cause cerebral edema.
- Restriction of sodium intake.
11
Q
HYPERNATREMIA = Na+ > 145 m/Eq/L
NURSING MANAGEMENT
A
- Intake and Output - strict and accurate
- Daily Weights - same time, clothes, scale
- Cardiovascular Changes - BP, HR, JVD
- Respiratory Changes - RR, SOB, cough, BS
- Neurological Changes - LOC, pupillary response, orientation, sensorium, voluntary movement, muscle strength, reflexes- OFTEN FIRST SIGN!!
- Skin assessment and care - dryness, turgor, elasticity, edema. Good oral care critical!!!
12
Q
POTASSIUM- K+
Serum level: 3.5-5.0 mEq/L
A
FUNCTION:
- Major ICF cation – 98% of K+ is intracellular.
- K+ necessary for normal cardiac rhythms.
- K+ necessary for skeletal and smooth
- muscle contraction.
- K+ helps make glycogen deposit in the liver.
Main source is dietary intake.
The ratio between ECF and ICF K+ determines the resting membrane potential necessary for the transmission of nerve impulses.
13
Q
Control of Potassium
A
- Kidneys- primary regulators of K +.
- Excess K+ in the ECF ↑ catecholamine levels, causing aldosterone levels to ↑.
- ↑ Aldosterone levels causes the K+ to leave the ECF and travel to the kidneys distal renal tubules, where it is excreted with urine.
- Insulin lowers the concentration of K+ by driving K+ into liver and muscle cells. Here it is used to break down carbohydrates and proteins by moving glucose into the ICF.
- Patients receiving ↑ amounts of insulin (TPN, DKA) should have K+ levels monitored closely.
14
Q
HYPERKALEMIA: K+ > 5.0 mEq/L
A
CAUSES:
- usually treatment related
- impaired renal function
- hypoaldosteronism
- tissue trauma
- acidosis
MANIFESTATIONS:
- cardiac changes and dysrhythmias
- muscle weakness with potential respiratory impairment
- paresthesias
- anxiety
- GI manifestations (cramps)
- ECG tented T-waves, arrhythmias
MEDICAL MANAGEMENT:
- monitor ECG
- limitation of dietary potassium
- cation-exchange resin (Kayexalate)
- IV sodium bicarbonate
- IV calcium gluconate
- regular insulin IV and hypertonic dextrose IV
- β-2 agonists (Albuterol MDI)
- dialysis
Potassium imbalances can be life threatening!!!
15
Q
HYPERKALEMIA: K+ > 5.0 mEq/L
MEDICAL MANAGEMENT
A
- Eliminate K+ intake both oral and IV.
- Administer diuretics- promote excretion of K+.
- Dialysis if patient is in renal failure.
- 10 units of Regular insulin is given IV push to move K+ from ECF to ICF. Given with glucose (1 amp of D 50)to prevent rebound hypoglycemia if patient is NOT diabetic.
- Beta 2-agonist (MDI Albuterol)
- Kayexalate (an ion-exchange resin)- given orally or via enema. (Exchanges Na+ ions for K+ ions in intestines and excretes K+ via feces).
- IV sodium bicarbonate given if patient is acidotic.
- IV calcium gluconate should be given to prevent life-threatening arrhythmias and protect heart.
