Acid-Base Balance Flashcards
Hydrogen Ions
Vital to life because determine the pH of the body.
Expressed as pH, the scale is determined by the number of hydrogen ions and it goes from 1 to 14.
The pH of body fluid is 7.35 - 7.45
Acids
Produced as end products of metabolism.
Are hydrogen ion donors.
pH below 7.35
pH < 6.80 = death
Bases
Contain no hydrogen ions. Are hydrogen acceptors. Normal serum levels of bicarbonate (HCO3) are 21 - 28 mEq/L (mmol/L). pH above 7.45 pH > 7.80 = death
Regulatory Systems for Hydrogen Ion Concentration: Buffers
Are the fastest-acting regulatory system.
Provide immediate protection against changes in hydrogen ion concentration in the extracellular fluid.
When too much acid or base is released in the system, they absorb or release hydrogen ions as needed, only to keep pH within the narrow limits.
Also serve as a transport mechanism that carries excess hydrogen ions to the lungs.
Regulatory Systems for Hydrogen Ion Concentration: Hemoglobin system (primary buffer system in extracellular fluid)
Maintains balance by a process called chloride shift.
Chloride shifts in and out of cells in response to the level of oxygen in the blood.
For each chloride ion that leaves a red blood cell, a bicarbonate ion enters.
For each chloride ion that enters a red blood cell, a bicarbonate ion leaves.
Regulatory Systems for Hydrogen Ion Concentration: Plasma protein system (primary buffer system in extracellular fluid)
It functions along with the liver to vary the amount of hydrogen ions in the chemical structure of plasma proteins.
Plasma proteins have the ability to attract or release hydrogen ions.
Regulatory Systems for Hydrogen Ion Concentration: Carbonic acid-bicarbonate system (primary buffer system in extracellular fluid)
The system maintains a pH of 7.4 with a ratio of 20 parts HCO3 to 1 part carbonic acid (H2CO3).
This ratio determines the hydrogen ion concetration of the body fluid.
Carbonic acid concentration is controlled by the excretion of CO2 by the lungs; the rate and depth of respiration change in response to changes in the CO2.
The kidneys control the bicarbonate concentration and selectively retain or excrete bicarbonate in response to bodily needs.
Regulatory Systems for Hydrogen Ion Concentration: Phosphate buffer system (primary buffer system in extracellular fluid)
System is present in cells and body fluids and is especially active in the kidneys.
System acts like bicarbonate and neutralizes excess hydrogen ions.
Regulatory Systems for Hydrogen Ion Concentration: Lungs
The lungs are second defense of the body and interact with the buffer system.
During acidosis, the respiratory rate and depth increase in an attempt to exhale acids. During alkalosis, the respiratory rate and depth decrease; CO2 is retained to neutralize and decrease the strength of excess bicarbonate.
The lungs can hold hydrogen ions until deficit is corrected or can inactivate hydrogen ions, changing the ions to water molecules to be exhaled along with CO2, thus correcting the excess.
Regulatory Systems for Hydrogen Ion Concentration: Kidneys
Process is slow and requires a few hours to several days.
- During alkalosis: excess bicarbonate ions move into the tubules, combine with sodium, and are excreted in the urine.
- During acidosis: excess hydrogen ions are secreted in the tubules and combine with buffers for excretion. The alterations of certain amino acids in the renal tubules results in a diffusion of ammonia into the kidneys; the ammonia combines with excess hydrogen ions and is excreted in the urine. Also, excess hydrogen ions are excreted in the form of phosphoric acid. At last, kidneys retain bicarbonate.
Regulatory Systems for Hydrogen Ion Concentration: Potassium (K+)
Potassium level changes to compensate for hydrogen ion level change.
- During acidosis: the body protects itself from the acidic state by moving hydrogen ions into the cells. Therefore, potassium moves out to make room for the hydrogen ions and the K+ level increases.
- During alkalosis: the cells release hydrogen ions into the blood in an attempt to increase the acidity of the blood; this forces the K+ into the cells and level decrease.
!! When the client experiences an acid-base imbalance, monitor the K+ level closely, because it moves in and out of cells in an attempt to maintain balance. The resulting hypo or hyperkalemia predisposes client to associated complications.
Respiratory Acidoses (causes)
Caused by primary defects in the function or changes in respiratory patterns. Any condition that causes an obstruction of the airway leading to hypoventilation or depresses the respiratory system can be a cause (asthma, brain trauma, sedatives, opioides, pneumonia, emboli, edema…)
Respiratory Acidoses (Assessment)
Neurological: Lethargy, confusion, dizziness, headache, coma.
Cardio: decreased BP, dysrhythmias (related to hyperkalemia), warm flushed skin.
NM: Seizures.
Respiratory: rate and depth increase in an attempt to exhale acids. However, when there is a respiratory problem and the lungs are unable to compensate, hypoventilation with hypoxia occurs.
Respiratory Acidosis (interventions)
Adm O2 as prescribed; Semi-fowler's position; Encourage cough and deep breathe; Assist to turn; Encourage hydration to thin secretions Reduce restlessness by improving ventilation, rather than by adm tranquilizers, sedatives or opioides. Suction airway if necessary Prepare for intubation and mechanical ventilation if CO2 above 50 mmHg and signs of acute distress.
Respiratory Alkalosis (Cause and assessment)
Results from conditions that cause overstimulation of the respiratory system (fever, hyperventilaton, hypoxia, mechanical overventilation, pain, severe anxiety).
Neuro: dizziness, lightheadedness, confusion, headache
Cardio: Low BP, tachycardia, dysrhythmias.
GI: Nausea, vomiting, diarrhea, epigastric pain.
NM: tetany, numbness, tingling of extremities, hyperreflexia, seizures.
Respiratory: rate and depth decrease as a compensatory action. However, when there is a problem, hyperventilation can occur.
