Acid- Base Balance: Flashcards
1
Q
Acid-base disturbances:
A
conditions that arise from illness; medication toxicity (CNS depressant); and/or neurogenic causes (severe anxiety, pain)
2
Q
What is pH?
Absolute normal blood pH?
A
- Plasma pH is an indicator of hydrogen ion (H+) concentration and measure the acidity or alkalinity of the blood.
- Chemists use a pH scale of 1-15; with 7 considered neutral.
- absolute normal blood pH: 7.40
3
Q
Hydrogen ions
A
- are vital to life because they determine the pH of the body and expressed as pH.
- The number of hydrogen ions in the body fluid determine whether it is acid (adidosis), alkaline (alkalosis), or neutral.
- Normal pH of body fluid is between 7.35-7.45
4
Q
Acids
A
- are produced as end products of metabolism and contain hydrogen ions.
- They are hydrogen ion donors; they give up hydrogen ions to neutralize or decrease the strength of an acid or form a weaker base.
5
Q
Bases:
- what are the 3 mechanisms to maintain pH
A
- are hydrogen ion acceptors; they accept hydrogen ions from acids to neutralize or decrease the strength of a base or to form a weaker acid.
- They contain no hydrogen ions.
- Normal serum levels of bicarbonate (HCO₃) are 22-26mEq/L.
- Acid base balance, or homeostasis of hydrogen ions, is necessary if the body systems are to function properly. The slightest change in ionic hydrogen concentration alters the rate of cellular chemical reactions.
- *To maintain normal blood pH, 7.35-7.45; the body relies on three mechanisms: buffers, respirations (lungs) and urinary excretion (kidneys).
6
Q
Buffers
A
- chemically composed of two substances, buffers prevent radical pH changes by replacing strong acids added to a solution (ie: blood) with weaker ones.
- Normal ratio of the principle buffer coupling of bicarbonate and carbonic acid is a ratio of 20:1; 20 bicarbonate to 1 carbonic acid.
- They absorb or release hydrogen ions as needed.
- Buffers are the fastest acting regulatory system and provide immediate protection against changes in hydrogen ion concentration in the extracellular fluid.
- Buffers serve as a transport mechanism that carries hydrogen ions the lungs.
- Once the primary buffer systems react, they are consumed, leaving the body less able to withstand further stress until the buffers are replaced.
7
Q
Primary buffer systems in extracellular fluid
A
- Hemoglobin system
- Plasma protein system
- Carbonic acid-bicarbonate system
- Phosphate buffer system
8
Q
Hemoglobin buffer system
A
- System maintains acid-base balance by a process called chloride shift.
- Chloride shifts in and out of the 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.
9
Q
Plasma protein buffer system
A
- The system 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
10
Q
Carbonic acid-bicarbonate buffer system
A
- Primary buffer system in the body
- Maintains a pH of 7.4 with a ratio of 20 parts bicarbonate (HCO₃) to 1 part carbonic acid (H₂CO₃)
- This ratio (20:1) determines the hydrogen ion concentration of 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.
11
Q
Phosphate buffer system
A
- Present in cells and body fluids; especially active in the kidneys.
- System acts like bicarbonate and neutralizes excess hydrogen ions.
12
Q
- The underlying cause of an acid-base imbalance needs to be identified and the cause needs to be treated to resolve the imbalance.
A
13
Q
Respiration (Lungs)
A
- is an important in maintaining blood pH and is the second defense of the body; they interact with the buffer system to maintain acid-base balance.
- During acidosis, the pH decreases and the respiratory rate and depth increase in an attempt to exhale acids. The carbonic acid created by the neutralizing action of bicarbonate can be carried to the lungs, where it is reduced to CO₂ and water and is exhaled making the hydrogen ions inactive and then exhaled.
- During alkalosis, the pH increases and the respiratory rate and depth decrease; CO₂ is retained and carbonic acid increases to neutralize and decrease the strength of excess bicarbonate.
- The action of the lungs is reversible in controlling excess or deficit.
- The lungs can hold hydrogen ions until the deficit is corrected or can inactivate hydrogen ions, changing the ions to water molecules to be exhaled along with CO₂; creating an excess.
- The process of correcting a deficit or excess takes 10 to 30 seconds to complete.
- The lungs are capable of inactivating only hydrogen ions carried by carbonic acid; excess hydrogen ions created by other mechanisms must be excreted by the kidneys.
14
Q
- Monitor the client’s respiratory status closely.
- 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.
A
15
Q
***Urinary Excretion (Kidneys)
A
- The third factor in acid base balance.
- Because the kidneys excrete varying amounts of acids and bases, they control urine pH, which also affects blood pH.
- For example; when blood pH is decreased (acidic), the distal and collecting tubules remove excess hydrogen ions (carbonic acid forms in the tubular cells and dissociates into hydrogen and bicarbonate) and displaces them in urine, eliminating hydrogen ions from the body.
- In exchange, basic ions in the urine – usually *sodium – diffuse into the tubular cells, where they combine with bicarbonate. The sodium bicarbonate is then reabsorbed in the blood, resulting in decreased urine pH and increased blood pH.
- The kidneys provide a more inclusive corrective response to acid-base disturbances than other corrective mechanisms, even though the renal excretion of acids and alkalis occurs more slowly.
- *Compensation requires a few hours to several days; but the compensation is more thorough and selective than that of other regulators, such as the buffer systems and lungs.
- During acidosis, the pH decreases and excess hydrogen ions are secreted into the tubules and combine with buffers for excretion in the urine.
- During alkalosis, the pH increases and excess bicarbonate ions move into the tubules, combine with sodium and are excreted in the urine.
- Selective regulation of bicarbonate occurs in the kidneys. The kidneys restore bicarbonate by excreting hydrogen ions and retaining bicarbonate.
- Excess hydrogen ions are excreted in the urine in the form of phosphoric acid.
- The alteration 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.
- *Potassium (K+) plays an exchange role in maintaining acid-base balance.
- The body changes the potassium level by drawing hydrogen ions into the cells or by pushing them out of the cells. Under normal conditions, the intracellular potassium content is much greater than that of the extracellular fluid. The concentration of hydrogen ions is low in both areas.
- In acidosis, the extracellular hydrogen ion content increases, and the hydrogen ions move into the intracellular fluid. To keep the intracellular fluid electrically neutral, an equal number of potassium ions leave the cell, creating relative hyperkalemia.
- In alkalosis, more hydrogen ions are present in the intracellular fluid than in the extracellular fluid. Hydrogen ions move from the intracellular fluid into the extracellular fluid. To keep the intracellular fluid electrically neutral, potassium ions move from the extracellular fluid into the intracellular fluid, creating a relative hypokalemia.
- The body is attempting to protect itself from the acidic state by moving hydrogen ions into the cells which causes the potassium to move extracellular to make room resulting in Hyperkalemia
- The opposite happens in alkalotic state as the cells release hydrogen ions into blood which forces the potassium into the cells resulting in Hypokalemia.
- *When the client experiences an acid-base imbalance, monitor the potassium level closely, because the potassium moves in or out of the cells in an attempt to maintain the acid-base balance .
16
Q
What complications can arise from Hypokalemia and Hyperkalemia?
A
- Respiratory Acidosis
- Respiratory Alkalosis
- Metabolic Acidosis
- Metabolic Alkalosis
17
Q
Respiratory Acidosis
A
- Caused primarily by defects in the function of the lungs or changes in the normal respiratory pattern.
- Excess carbonic acid
- Generally due to hypoventilation and CO₂ retention which lowers the pH
18
Q
Respiratory Acidosis Causes:
A
- COPD
- barbiturate/CNS depressant/opioid overdose
- brain trauma
- pneumonia
- asthma
- atelectasis
- low respiratory rate on the ventilator
- pulmonary edema
- conditions that cause muscle weakness
- *pulmonary embolism – when unable to ventilate; the emboli results in an obstruction and inadequate gas exchange.
19
Q
Respiratory Acidosis Clinical Manifestations
A
- Lethargy
- confusion
- headaches
- low BP
- dysrhythmias r/t hyperkalemia
- seizures
—————— - warm flushed skin
- hyperkalemia
- coma
- dizziness
