module three | BIO 224

acids

substances that donate hydrogen ions

bases

substances that accept hydrogen ions

pH

clinical measure of acid:base ratio; measurement of hydrogen ion

• acid = high concentration of hydrogen ions

• basic = low concentration of hydrogen ions

anion gap

difference between major cations (sodium) and anions (chlorine and bicarbonate) in the blood

• represents the unmeasurable anions such as: phosphate, organic acids serum proteins)

• 12 = 142 - (103 + 27); normal value

• metabolic acidosis is anion gap is greater than 12 or excess chlorine/low bicarbonate

buffers

act to resist pH change by sequestering pr releasing hydrogen ions

• mix acids and bases to resist change

• trade stronger acids and bases for weaker

plasma buffer

reacts to hydrogen ion levels in seconds (quickest)

• utilizes these systems to balance the buffer:

  • bicarbonate buffer

  • protein buffer (albumin)

  • H+/K+ exchange

respiratory buffer

reacts in minutes to excrete carbon dioxide

renal buffer

reacts in hours to days to produce, absorb, and excrete acid, bases, and ions

how does metabolic acidosis compensate?

because of the low pH levels:

• respiratory rate will increase meaning more carbon dioxide will be exhaled (excretion) bringing the pH level up

  • break down of carbonic acid

how does metabolic alkalosis compensate?

because of the high pH levels:

• respiratory rate will decrease meaning carbon dioxide will be retained causing the pH level to decrease via the build up of hydrogen ions

  • carbon dioxide will mix with water to make carbonic acid

where is respiratory buffer controlled?

the brainstem containing the pons and medulla oblongata (primitive area)

• chemoreceptors sense hydrogen ion concentration

hypoxemia

decreased oxygen in the arterial blood

• leads to decrease in pressure of oxygen in the blood

  • paCO2 less than 80 mmHg

hypoxia

oxygen deprivation in the cells

• causes by a decrease ventilation of decreased perfusion

• patients become restless, confused, tachypneuc, and tachycardic

hypercapnia

increased carbon dioxide in the blood

changes in blood bicarbonate levels can lead to:

metabolic acidosis or metabolic alkalosis

changes in blood carbon dioxide levels can lead to blood pH imbalance:

respiratory acidosis or respiratory alkalosis

normal pH levels of blood

7.35 - 7.45

paCO2

35 - 44 mmHg

HCO3

22 -26 mmHg

paCO2

80 - 100 mmHg

saO2

greater than 95%

base excess

gain or loss 2.0 mEq/L

uncompensated

pH is outside the expected reference range and either the HCO3 (bicarbonate) or paCo2 is outside the expected range

• ex:

  • pH = 7.30

  • CO2 = 48

  • HCO3 = normal

partially compensated

pH, HCO3, and paCO2 are all outside the reference ranges

• ex:

  • pH = 7.32

  • CO2 = 48

  • HCO3 = 28

fully compensated

pH is within the range and paCO2 and HCO3 are outside the reference ranges

• ex:

  • pH = 7.37

  • CO2 = 48

  • HCO3 = 30

pulse oximeter

measure oxygen saturation; amount of hemoglobin fully saturated

• less than 95% indicates hypoxemia (decrease oxygen in arterial blood)

arterial blood gas (ABG)

measures partial pressure of oxygen (paO2) in the blood

• partial pressure of CO2 less than 80 indicates hypoxemia

total parenteral nutrition (TPN)

delivery of water, glucose or dextrose, amino acids, lipids, vitamins, minerals, electrolytes, acetate, and trace elements through venous system

• hydrochloric and organic acids and base are additives

• metabolic acidosis can occur

cations

ions with a positive charge

anions

ions with a negative charge

sodium

135 - 145 mEq/L

potassium

3.5 - 5 mEq/L

chloride

98 - 106 mEq/L

calcium

8.5 - 10.2 mg/dL

magnesium

1.5 - 2.5 mEq/L

phosphate

2.5 - 4.5 mg/dL

hypovolemia

deficit of bodily fluid volume, decreased vascular volume

• causes:

  • fluid loss

  • less intake

  • fluid in the peritoneal cavity

• ex:

  • hemorrhage

  • dehydration

hypervolemia

excess fluid in vascular or interstitial space

• ex:

  • edema

  • water intoxication

tonicity

fluid movement in or out of the cell in response to tonicity of extracellular solution

isotonic

equal concentration of solutes

hypertonic

more solutes on the outside of the cell; cell will shrivel

hypotonic

more solutes in the inside of the cell; cell will swell and burst

hemorrhage

excessive bleeding

• loss of water and sodium levels at an equal rate = isotonic