Acid Base Balances

Conditions that affect acid/base balance

• Infection

• Trauma

• Medications

• Disease processes

Normal pH

7.35 to 7.45

• Represents a balance b/w the & of hydrogen ions & bicarbonate ions

Acid base imbalance causes:

1. Changes shape of hormones & enzymes

2. Changes distribution of other electrolyes causing F&E imbalance

3. Changes membranes: making the heart, nerves, muscles, Gi tract more or less active (muscle contraction)

4. Decreases the effectivness of many drugs & hormones

Acids

____ are substances that release hydrogen ions (give up or donate) when dissolved in water (H20) increasing the amount of free hydrogen ions in that solution

• Incomplete breakdown of glucose

• Incomplete breakdown of protein & fats

• Destruction of cells

Hydrogen ions sources

• Intake (PO,IV, IM, NG)

  • Food: fatty acids, amino acids

  • Drugs: aspirin, toxins, paraldehyde, ethylene glycol, methanol, formaldehyde

• C02 production:

  • C02 is not an acid, but it combines w water to form carbonic acid which then dissociates into H- & HC03

• Metabolic acids:

  • Citric acid cycle intermediates (aerobic metabolism)

  • Latric acid (anaerobic metabolism)

  • Ketoacids— produced when some fats are incompletely metabolized

• Other organic acid production

Bases

• A base binds (accepts) free hydrogen ions in solution & lowers the amount of free hydrogen ions in solution

• Strong _____ bind hydrogen ions easily; for ex, ammonia

• Bicarbonate ions are the most common base in the body

Buffers

• The body always tryes to bring pH to 7.35-7.45

• If basic (alkaline): buffer releases hydrogen ions

• If acidic: buffer binds hydrogen ions

Chemical Control Buffer

__________ are the 1st line of defense against change in free hydrogen ion lvls

• Always present in body fluids & act FAST to reduce or raise free hydrogen ions

Composed of chemicals or chemical buffers

• Bicarbonate

• Phosphate

Protein buffers:

• Albumin

• Globulins

• Hemoglobin

Respiratory Buffer

When chemical buffers alone cannot prevent blood pH changes, the respiratory system is the 2nd line of defense:

• Hyperventilation

• Hypoventilation

Lungs compensate for acid-base imbalance of metabolic origin

Kidney Buffer

3rd line of defense

• Stronger but slower buffer

• Can take 24-48 hrs to respond

• Increase excretion & reabsorption of acids or bases: kidney movement of bicarb, formation of acids, & formation of ammonium

• Kidneys can correct/compensate for pH changes when the resp. system is overwhelmed or unhealthy

Compensation

• Body attemps to correct blood pH changes

• pH <6.9 or >7.8 unusually fatal

• Resp. system more sensative to acid-base changes; can begin compensating in seconds to minutes

• Kidneys more powerful; result in rapid changes in ECF compostion; fully triggered for imbalance of several hours to days

Acidosis

Excess of hydrogen ions, arterial pH <7.35

• Not a disease: a condition caused by a disorder

• Caused by metabolic problems, respiratory problems or both

• Results from actual or relative increase in amount or strength of acids

Causes major changes in body fx

• Hydrogen ions are positively charged ions

• Increase creates an imbalance of other posivively charges electrolytes, especially potassium

• Disrupts fx of nerves, cardiac muscles, skeltal muscle

• Even slight increases in blood hydrogen ion lvls reduce the activity of many hormones & enzymes leading to death

Symptoms of Acidosis

Cardiovascular:

• EKG changes

• Bradycardia to heartblock

• Hypotension

• Thready pulses

• Assess cardiovascular system 1st in any pt at risk for acidosis it can lead to cardiac arrest from hyperkalemia

CNS: Depressed activity

• Lethargy

• Confusion

• Stupor

• Coma

Neuromuscular

• Hyporeflexia

• Skeletal muscle weakness

• Flaccid paralysis

Respiratory

• Kussmaul respirations (fast & deep)

• Variable respirations

Integumentary

• Warm flushed dry

• Pale to cyanotic

Alkalosis

Excess of bases, especially bicarbonate

• Decrease in free hydrogen ion lvl pH above 7.45

Symptoms of Alkalosis

CNS:

• Increased activity

• Anxiety, irritability, tetany, seizures

• Postive chvosteks

• Positive trousseau’s sign

• Paresthesias

Neuromuscular

• Hyperreflexia

• Muscle cramping & twitching

• Skeletal muscle weakness

Cardiovascular

• Increased HR

• Normal or low bp

• Incrased digitalis toxicity

Respiratory

• Increased rate & depth of ventilation in resp alkalosis

• Decreased resp effect (assoc w skeletal muscle weakness) in metabolic alkalosis

Arterial Blood Gas

• Most hospitals: resp therapist obtains

• In ICU: pt often have an arterial line for monitoring arterial blood pressure, Rn can draw off arterial sample for ______ (you will learn about this in crtical care course)

• The sample must go quickly to the lab on ice. The RT will draw a sample. RN often offers to hold pressure on site so the sample can go quickly

• Drawing _____ from radial artery: allen test

  • What the test results mean: If normal color comes back to your hand w/i 5-15 seconds, it means that one artery is healthy enough to supply blood to your hand all by itself

Partial pressure of’Carbon dioxide/ PaCO2

Normal lvl: 35-45 mmHG

Bicarbonate/ HCO3

Normal lvl: 22-26 mEq/L

Partial pressure of oxygen/ Pa02

80-100 mmHg

Respiratory Acidosis

Unable to rid the body of enough CO2 due to:

• Decreased resp or inaequete gas exchange

• Ventilation failure

• Perfusion compromise

• Airway obstruction

• Neuromuscular problems

• Myasthenia gravis

• CPD- less surface area (asmtha,COPD, bronchitis, ARDs, pulmonary edema)

• Spinal cord injury (diaphragmatic paralysis)

• Medications: Anesthetics, hyponotics, opiods, sedatives

Treatment for respiratory acidosis

• Improving ventilation & lowering CO2

• Maintain patent aiway

• Bronchodilators

• Oxygen

• Drug therapy (hyperkalemia)

• Antibiotics for infection

• Chest physiotherapy (secretion removal)

• Removal of foreign body

Respiratory Alkalosis

Results from alveolar hyperventilation & hypocapnia (low CO2)

• A sudden increase in ventilation, hyperventilation-anxiety, panic attacks

• CPR

• Hypermatabolic state: fever, liver failure, sepsis

• Hypoxia (high altitude, pulmonary diesase, severe anemia, pulmonary embolus, hyptension)

• Mechanical ventilation

• Salicylate Intoxication

Treatment for respiratory Alkaloisis

• Breathe into a paper bag or cupped hands

• Prevent hyperventilation

• Matain F&E balance

• Maintain safety

Metabolic Acidosis

• Increased H+ production and/or loss of HCO3

• Depresses CNS

• Untrated leads to ventricular arrhythmias, coma, cardaic arrest

Overproduction of hydrogen ions

• Excessive oxidation of fatty acids: diabetic ketoacidosis, starvation, chronic alchoolism, malnutrition/starvation, hyperthyroidism, severe infection

• Hypermetabolism: heavy exercise, seizure, fever, hypoxia/ischemia, sepsis

• Excessive ingestion of acids: ethanol intoxication, salicylate intoxication (ASA overdose)

• Poisoning/toxic reaction to meds

Under elmination of hydrogen ions

• Decreased ability of kidneys to excrete acids (renal insufficenty or renal failure)

Underproduction of bicarbonate ions

• Kidney failure

• Pancreatitis

• Liver failure

• Dehydration

Over elimination of bicarbonate ions

Diarrhea

Treatment for metabolic acidosis

• Mechanical ventilation if needed

• Reverse DKA (drives K+ into cell)

• Dialysis for renal failure or toxic drug raction

• Antibiotics for infection

• IV sodium bicarb & fluid hydration

• Antidiarrheal

Metabolic Alkalosis

Increase of base (HCO3)

• Cushing’s disease (excess cortisol)

• Post cardiac arrest (NaCO3 administartion)

• Drugs: corticosteriouds & antacids

• Excessive bood transfutions

Decrase (or loss) of acids

• Excessive acid loss from the GI tract

• Vomiting

• Prolonged NG tube suctiong

• GI disorders

• Diuretic therapy (thiazide & loop diuretics)

Treatmnet for metabolic alkalosis

• Correct acid-base by getting rid of excess HCO3 & increasing H+

• Dc diuretics & NG suctioning

• ANtiemtic

• Durg therapy (acetazolamide) to inhibit calcium & increase renal excretion of HCO3

• Seizure precautions

• May need K+ supplements

• Prevent further lossess of hydrogen, K+, calcium, & chloride ions

• Restore fluid balance