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Acid-Base Balance

Terms in this set (73)

Hydrogen Ions
determine the relative acidity of body fluids
Acids
release hydrogen ions in solution
Bases (alkalis)
accept hydrogen ions in solution. Will bind to a hydrogen ion being sodium bicarbonate (NAHCO3)
pH
hydrogen ion concentration is measured as _____
Acidic
as hydrogen ion concentration increases, the pH falls, and the solution becomes more _____
Alkaline or basic
as hydrogen ion concentration falls, the pH rises and the solution becomes more __________
7.35-7.45
normal pH levels of body fluids (slightly basic)
Volatile acid
Eliminated from the body as gas
Carbonic acid
the only volatile acid produced in the body. Dissociates into carbon dioxide and water. Carbon dioxide is then eliminated through the lungs
Nonvolatile acids
must be metabolized or eliminated in body fluids. All other acids inside the body (except carbonic acid)
Lactic acid
acid that results from cellular destruction
Hydrochloric acid
acid that is found in stomach secretions
Phosphoric acid
acid that forms from the oxidation of phospholipids and phosphoproteins
Sulfuric acid
acid the is formed from oxidation of sulfur containing amino acids
3 systems that help maintain normal pH
buffer system, respiratory system and renal system
Buffers
substances that prevent major changes in pH by releasing hydrogen ions (acid). When excess acid is present, they bind to hydrogen ions to minimize the change in pH. If body fluid is too basic or alkaline, they release hydrogen ions
Bodies major buffer systems
bicarbonate-carbonic acid buffer system, the phosphate buffer system, and protein buffer system
Bicarbonate-carbonic acid buffer system (equation)
CO2 + H2O <--> H2CO3 <--> H+ + HCO3-
24 mEq/L
serum bicarbonate level
1.2 mEq/L
serum carbonic acid level
20:1
bicarbonate to carbonic acid ratio
acidosis
the condition that results when hydrogen ion concentration increases above normal cause the pH to drop below 7.35
alkalosis
the condition that results when hydrogen ion concentration falls below normal and the pH level rises above 7.45
Respiratory system
regulates carbonic acid by eliminating or retaining carbon dioxide.
Carbon dioxide
when combined with water, it forms carbonic acid. Respiratory rate regulates the rate at which it is expelled from the body or taken in
Renal system
long term regulation of acid-base balance
PaCO2
measures the pressure exerted by dissolved carbon dioxide in the blood and reflects the respiratory component of acid-base regulation and balance because it is regulated by the lungs.
34-45 mmHg
normal PaCO2 levels
Hypocapnia
a condition that results when PaCO2 falls below 35mmHg
Hypercapnia
a condition that results when PaCO2 rises about 45mmHg
PaO2
a measure of the pressure exerted by oxygen that is dissolved in the plasma. Only 3% of O2 is transported in solution, most is combined with hemoglobin. Not used as a primary measurement in determining acid-base balance
80-100mmHg
normal PaO2
hypoxemia
condition resulting from PaO2 levels falling below 80mmHg
Serum Bicarbonate (HCO3-)
reflects renal regulation of acid-base balance. Normal value is 22-26mEq/L
Base Excess (BE)
a calculated value also known as buffer base capacity. Measure substances that can accept or combine with hydrogen ions. Reflects the degree of acid-base imbalance by indicating the status of the body's total buffering capacity. Represents the amount of acid of base that muse be added to the blood sample to achieve a pH of 7.4.
-3.0 to +3.0
normal BE for arterial blood
Arterial blood gases (ABGs)
used primarily to assess acid-base balance. Reflects acid-base balance throughout the entire body better than venous or capillary blood that has dispersed oxygen into the tissues and collected carbon dioxide. Indicates the regulatory mechanism of the lungs or kidneys.
Metabolic disorders
primary change is in the concentration of bicarbonate
Respiratory disorders
primary change is in the concentration of carbonic acid
Primary disorders
usually due to one cause. For example, respiratory failure often causes respiratory acidosis due to retained carbon dioxide; renal failure usually causes metabolic acidosis due to retained hydrogen ion and impaired bicarbonate production
Mixed disorders
occur from combinations of respiratory and metabolic disorders.
Pharmacotherapy for acidosis
administration of sodium bicarbonate infusions. Carefully monitor ABGs during infusions and what for signs of alkalosis
S/S of alkalosis
irritability, confusion, cyanosis, slow respirations, irregular pulse, and muscle weakness
Pharmacotherapy of alkalosis
administer sodium chloride concurrently with potassium chloride. Severe cases can be treated with infusions of an acidic drug such as ammonium chloride.
S/S of toxic levels of ammonium
pallor, sweating, irregular breathing, retching, bradycardia, twitching, and convulsions.
5mL/min
to prevent ammonium toxicity, administer no more than ____
Risk factors or metabolic acidosis
cardiac arrest (acute lactic acidosis), clients with type 1 DM (diabetic ketoacidosis), acute or chronic renal failure, Diarrhea, intestinal suction, or abdominal fistulas
Manifestations of Metabolic acidosis
diminished appetite, N/V, abdominal pain, weakness, fatigue, headache, general malaise, decreased LOC's, dysrhythmias, bradycardia, warm/flushed skin, skeletal problems, hyperventilation (kussumaul's respirations) dyspnea
Etiology of Metabolic Alkalosis
excessive acid loss due to vomiting or gastric suction, excessive use of potassium losing diuretics, excessive adrenal corticoid hormones due to cushing syndrome, hyperaldosteronism, excessive bicarbonate intake from antacids, parenteral NaHCO3
Manifestations of metabolic alkalosis
confusion, decreasing level of consciousness, hyperreflecia, tetany, dysrhythmias, hypotension, seizures, respiratory failure.
Lab and diagnostic tests for metabolic alkalosis
ABGs (show a pH greater than 7.45 and bicarbonate level greater than 26 mEq/L), Serum electrolytes (Serum potassium <3.5 mEq/L and decreased chloride <95 mEq/L), Urine pH (pH 1-3), ECG (shows changes similar to hypokalemia)
Acute respiratory acidosis
occurs due to sudden failure of ventilation, chest trauma, aspiration of a foreign object, acute pneumonia, and overdoses of narcotic or sedative medications
Chronic respiratory acidosis
associated with chronic respiratory or neuromuscular conditions such as COPD, asthma, cystic fibrosis, and multiple sclerosis
Clinical manifestations of respiratory acidosis
ACUTE: headache, warm/flushed skin, elevated pulse, blurred vision, irritability, altered mental status, decreased LOC, cardiac arrest
CHRONIC: weakness, dull headache, sleep disturbances with daytime sleepiness, impaired memory, personality changes
Diagnostic tests for Respiratory Acidosis
ABGs (pH less than 7.35 and a PaCO2 of more than 45mmHg), Serum electrolytes (chloride level <98mEq/L), PFT's
Etiology of Respiratory alkalosis
extreme anxiety, elevated temp, overventilation with a mechanical ventilator, hypoxia, salicylate overdose, brain stem injury, fever, increased BMR
Manifestations of Respiratory alkalosis
dizziness, numbness and tingling around the mouth, hands and feet...palpitations, dyspnea, chest tightness, anxiety/panic, tremors, tetany, seizures, loss of conciousness
Hydrogen (acid)
potassium expelled from upper GI losses
Bicarbonate (base)
potassium expelled from lower GI losses
Buffers reaction time
within seconds to pH change by excreting CO2 from lungs, and days by excreting H ions and HCO3 from the kidneys
how often does biological regulation of acid/base occur?
every 2-4 hours
How does biological regulationg of acid/base occur?
H enters cell and potassium leaves cell (ECF<Acid) CO2 diffuses into RBC forming carbonic acid
Respiratory acidosis
caused by hypoventilation, retaining H ions.
S/S of respiratory acidosis
impaired respirations, disorientation, weakness, H/A, decreased respirations, Increased HR, decreased blood pressure, convulsions, coma
Respiratory Alkalosis
caused by hyperventilation. There is a decrease in H ions due to respirations
S/S oF respiratory alkalosis
deep/rapid breathing, tetany, paresthsia, tinnitus, blurred vision, diaphoresis, dry mouth, N/V, inability to concentrate, disorientation, coma
Metabolic acidosis
increased H ion by loss of HCO3 (lower GI losses)
S/S of metabolic acidosis
SOB with exertion, hyperventilation, Weakness, disorientation or coma
Metabolic alkalosis
there is a loss of acid (vomitting)
S/S of metabolic alkalosis
numbness and tingling of extremities, hypertonicity of muscles, slow/shallow respirations or apnea, bradycardia, dizziness, convulsions
PCO2
measures the adequacy of pulmonary circulation
HCO3
measures the kidneys ability to retain or excrete bicarbonate
What are the steps to interpreting a blood gas?
1)look at pH
2) determine the cause of the imbalance
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