MedSurg 3 - Acid-Base Imbalances (Chap 14) Flashcards
Exam # 3
Acid-base balance
the process of carefully regulate hydrogen ion (H+) production and elimination
Normal arterial pH // venous blood
arterial = 7.35 to 7.45 ; venous = 7.31 to 7.41
Carbonic Anhydrase Equation
CO2 + H2O H2CO3 HCO3 + H
H2CO3 – Carbonic Acid – common ACID in the body.
HCO3 – Bicarbonate – common BASE in the body.
** As CO2 increases, more H+ is created. – Which means the more CO2 retained in the body, the more acid is produced. **
metabolism of Carbohydrate, protein and Fat
CARBOHYDRATE metabolism forms CO2.
**Incomplete breakdown of glucose which occurs whenever cells metabolize under ANAEROBIC (no oxygen) condition forms LACTIC ACID. This occurs when body has very little oxygen to meet metabolic oxygen demands such as heavy exercise, seizure activity, fever, and reduced oxygen intake.
Anaerobic condition occur with HYPOXIA, SEPSIS & SHOCK.
metabolism of protein
PROTEIN breakdown forms SULFURIC ACID.
metabolism of Fat
FAT breakdown forms FATTY ACID & KETOACIDS.
** Incomplete breakdown of FATTY ACIDS occuring when large amount of fatty acids are being metabolized forms KETOACIDS.
Kidney Movement of Bicarbonate – the 1st kidney pH control action
When blood pH changes are persistent, kidney actions that increase excretion and reabsorption rates of acids or bases (depending on the direction of the pH changes) begin to operate. These actions are kidney movement of bicarbonate, formation of acids, and formation of ammonium.
Formation of ACIDs – the 2nd kidney pH control action
When blood hydrogen ion levels is high, this bicarbonate is reabsorbed from the kidneys back into the circulation, where it can help buffer excess hydrogen ions. In this situation, the kidney tubules also can make additional bicarbonate and reabsorb it for an increase buffer effect. When blood hydrogen ion levels are low, the bicarbonate remains in the urine and is excreted.
Formation of AMMONIUM – the 3rd kidney pH control action
Ammonia (NH3), which is formed during normal protein breakdown, is converted into Ammonium (NH4). The ammonia that is secreted into the urine where it is combined with the excess hydrogen ion to form ammonium. The ammonium traps the hydrogen ions and then excreted in the urine. The result is loss of hydrogen ions and an increase in blood pH.
Cause of Acidosis
Overproducing ACID – Ex. Diabetic Ketoacidosis and Seizures.
Underelimiminating ACID – Ex. Respiratory and/or Kidney Impairment
Metabolic Acidosis
Four Process that cause metabolic Acidosis:
- Overproduction of Hydrogen ions
- Underelimination of Hydrogen ions
- Underproducion of Bicarbonate ions
- Overelimination of Bicarbonate ions
Metabolic Acidosis (con't) - overproduction & underelimination of acid
Overproduction of acid:
– Excessive intake of acids such as: Alcoholic beverages, Methyl Alcohol, Acetylsalicylic Acid (Aspirin)
Underelimination of acid:
– Kidney Failure and Lung Problem
Metabolic Acidosis (con't) - underproduction & over-elimination of bicarbonate
Underproduction of bicarbonate:
– Because bicarbonate is made in the kidney and pancreas, kidney failure and impaired liver or pancreatic function can cause base-deficit acidosis.
Over-elimination of Bicarbonate:
– Diarrhea can cause bicarbonate lost.
Manifestation of ACIDOSIS
ACIDOSIS reduces the ability of excitable membranes to respond appropriately, especially in cardiovascular tissue, neurons, skeletal muscle, and GI smooth muscle
Cardiovascular:
Early changes – increase HR and CO
Worsening Acidosis and HYPERKALEMI A – HR decreases, T-Waves become tall and peaked, QRS are widened. Peripheral pulses are hard to find. Hypotension bec of vasodilation.
Manifestation of ACIDOSIS
– Cardiovascular
Early changes:
– increase HR and CO
Worsening Acidosis and HYPERKALEMIA:
– HR decreases, T-Waves become tall and peaked, QRS are widened. Peripheral pulses are hard to find. Hypotension bec of vasodilation.
Manifestation of ACIDOSIS
– Central Nervous System (CNS)
Depression of CNS function
– Lethargy to Confusion (esp. in older adults)
As acidosis worsens:
– may become Unresponsive
** assess mental status
Manifestation of ACIDOSIS
– Neuromuscural
reduced Muscle tone and deep tendon reflexes
- cause of these are hyperkalemia along with acidosis.
** assess muscle strength
Manifestation of ACIDOSIS
– Respiratory
** Assess RATE, DEPTH, and EASE of Breathing. Check Pulse Oximetry.
Metabolic Acidosis:
– Breaths are RAPID and DEEP as hydrogen level rises and not under voluntary control. – called KUSSMAUL Respiration.
Respiratory Acidosis:
– Breaths are SHALLOW and RAPID. Muscle weakness makes this problem worse!
Manifestation of ACIDOSIS
– Skin
Metabolic Acidosis:
– Means breathing is NOT impaired, the rate is increased and CO2 is lost. This caused vasodilation and makes the skin WARM, DRY, and PINK.
Respiratory Acidosis:
– Breathing is impaired, so skin is PALE to CYANOTIC.
ABG Values
pH —- 7.35 to 7.45
PaO2 —- 80 to 100
PaCO2 — 35 to 45
HCO3 — 21 to 28
Metabolic Alkalosis - Etiology
Base (Bicarb) Excess:
- excessive intake of bicarbonates, carbonates, acetate, citrate
- Ex. excessive use of Oral antacids containing sodium bicarbonate or calcium bicarbonate
Acid Deficit:
- Prolonged Vomiting
- Prolonged Gastric Suctioning
- Excess cortisol
- Hyperaldosteronism
- Use of Thiazide Diuretics
Respiratory Alkalosis - Etiology
Excessive loss of CO2:
- HYPERVENTILATION (rapid respirations) due to:
- —– anxiety, fear, or improper setting on mechanical ventilators.
- —– hyperventilation can also result from direct stimulation of central respiratory centers bec of: fever, certral nervous system lesions, and salicylates
Manifestation of Alkalosis
-s/s are the same for respiratory & metabolic alkalosis:
Many S/S are the result of:
- Hypocalcemia
- Hypokalemia
** These problem change the function of the nervous system, neuromuscular, cardiac, and respratory.
Manifestation of Alkalosis
– CNS
Caused by overexcitement of the nervous system:
- Dizziness
- Agitation
- Confusion
- Hyperreflexia, which may progress to seizure
- Tingling or numbness around the mouth and toes
- Positive Chvostek’s & Trousseau’s sign
Manifestation of Alkalosis
– Neuromuscular
Related to Hypocalcemia & hypokalemia:
- Muscle Cramps
- Twitches
- “Charley Horses”
- Deep Tendon reflexes are hyperactive
- TETANY (continuous contractions) of muscle groups may be present —– painful and indicates a rapidly worsening condition
- ** Skeletal muscle may contract as a result of over stimulation, but they become weaker bec of hypokalemia:
- Handgrip decrease
- unable to stand or walk
- Respiratory effort is less effective as skeletal muscle weakens
Manifestation of Alkalosis
– Cardiovascular
Cardiovascular Changes bec of Increase in Myocardial irritability, esp when accompanied with hypokalemia:
- HR increase
- Pulse is thready
- Severe Hypotension (if hypovolemia is also present)
- Risk for Digoxin Toxicity (hypokalemia increases myocardial sensitivity to digoxin)
Manifestation of Alkalosis
– Respiratory
- Increase Respiratory Rate (caused by anxiety or physiologic changes)
Interventions for Alkalosis
- Prevent further loss of Hydrogen, Potassium, Calcium, Chloride ions
- ** STOP or MODIFY: suctioning, infusion of IV solutions containing bases, drugs that promote hydrogen excretion
- Restore fluid balance
- ** Fluid and electrolyte replacement
- ** Antiemetic (if caused by vomiting)
- Monitor Changes
- ** Adjust fluid & electrolyte therapy
- ** Monitor electrolyte values daily until normalized
- Provide Patient Safety
- ** PREVENT FALL ( bec pt has muscle weakness and hypotension)
