Acid-Base Disorders

potassium is in the system, there will be fewer hydrogen ions in the filtrate and less

conservation of bicarbonate.

ACID-BASE DISORDERS

The normal pH in the blood is between 7.35 to 7.45. Levels below this are considered to be

acidotic, while levels above this are considered to be alkalotic. The symptoms of acidosis are

fatigue, lethargy, headache, and confusion. The symptoms of alkalosis are cognitive impairment, numbness and tingling, muscle twitching, and nausea/vomiting. Metabolic and

respiratory disorders can cause either acidosis or alkalosis. The respiratory component involves

CO2, which parallels the carbonic acid level, while the renal component involves bicarbonate

levels.

Metabolic acidosis involves primary bicarbonate deficiency. The most common cause of this

problem is excessive numbers of organic acids or ketones in the bloodstream. Other causes of

metabolic acidosis include diarrhea (with loss of bicarbonate), kidney disease, diabetic

ketoacidosis (from ketones), strenuous exercise, methanol toxicity, paraldehyde toxicity,

isopropanol toxicity, ethylene glycol toxicity, and salicylate poisoning (from aspirin overdoses).

Metabolic alkalosis is from primary bicarbonate excess. This can be caused by ingestion of

certain antacids, excess ACTH production in Cushing’s disease, vomiting (loss of acid), and

excessive diuretic or laxative abuse.

Respiratory acidosis comes from respiratory failure, pneumonia, or congestive heart failure. On

the other hand, respiratory alkalosis comes from hyperventilation, salicylate toxicity (after an

initial acidosis), and catecholamine excesses.

These things rarely happen as “pure diseases” but are rapidly compensated for in the body.

The goal of compensatory mechanisms is to maintain the pH of the blood, which is paramount

over the actual concentrations of CO2, carbonic acid, and bicarbonate. The lungs will

compensate for metabolic acidosis by blowing off CO2 and will compensate for metabolic

alkalosis by holding onto CO2 (within limits, because respiration must to a degree continue to

happen or the person will die).

The kidneys will eventually compensate for respiratory acidosis or respiratory alkalosis but it

takes hours to days for this to occur. Hydrogen ions can be secreted and bicarbonate can be

conserved, depending on the pH of the body. This will work to some degree in both elevated

and low pH changes in the body.