Indicator of the acidity or basicity of a solution

measure of the hydrogen ion concentration [H+]

ranges from 0-14

pH< 7.0 is acidic

pH= 7.0 is neutral

ph> 7.0 is basic

normal blood pH is 7.35- 7.45

values slightly above or below these values may be compatible with life, but can lead to serous acidosis or alkalosis

enzymes that are constructive can become destructive or not function properly

comprises O2 delivery to cells

comprises organ systems

food abosrption and digestion can also be affected

also known as academis

as a high hydrogen ion concentration when blood pH is <7.35

also known as alkalemia

defined as low hydrogen ion concentration when blood pH is >7.45

an estimate of the sum of the plasma concentrations of bicarbonate, carbonic acid, and dissolved gaseous carbon dioxide

bicarbonate conc. is the commonly measured index of blood hydrogen ions homeostasis

venous blood can be used

often performed with urea and electrolytes tests

measures how much gaseous carbon dixode is dissolved in the blood and how well it able to move out of the body.

indicates whether or not a respiratory problem exists.

high Pco2 indicates hypoventillation (respiratory acidosis).

a low Pco2 indicates hyperventillation ( respiratory alkalosis)

a measure of the capacity of oxygen transport.

percentage of hemoglobin binding sites in the bloodstream occupied by oxygen (oxyhemoglobin)

any solution: pH= -log[H+]

Henderson-Hasselbach equation: pH= pKa+log[HCO3]/[H2CO3]

Henderson-hasselbach used for body fluids and blood

[HCO3]- represents the contribution of pH from the kidneys

[H2CO3]- represents the contribution of pH from the lungs

soulutions of weak acids or bases and their associated salts( conjugated acid or base)

resist changes in pH by reacting with an acid or a base

a substance that separates less readily into ions.

gives up H+ with difficulty

(weak acids are also weak electrolytes)

form conjugate bases with the loss of hydrogen ions(H+)

a substance that has slight affinity to gain hydrogen ions (H+)

form conjgate acids with the additon of hydrogen ions

when a strong acid is added to a buffer, hydrogen ions of the strong acid will react with the conjugate base of the buffer system.

This reduces the conc. of hydrogen ions by making a weak acid.

This explains how the ph of 1.2 hydrochloric acid can be increased to a pH of 5.1 to 7.1

when a strong base is added to a buffer, hydroxide ions of the strong base will react with the weak acid of the buffer system.

This reduces the conc. of hydroxide ions by making water and the conjugate base of the weak acid.

this explains how the pH of 13 of sodium hydroxide can be decreased to a pH below 7.4

-the amount of the acid or base produced and absorbed equals the amount of acid or base excreted and expired.

-The amount of acid or base consumed from the diet and absorbed in the intestines as well as that metabolically produced is equal to the amount ofacid or base excreted by the lungs and kidneys.

1) intracellular buffers ( inside all the cells in the body)

2) extracellular buffers ( Blood, Interstitial fluid, urine, csf)

3) respiratory mechanisms (lungs)

4) remnal mechanims ( kidneys)

( blood, interstitial fluid, urine, csf)

react very rapidly (w/in seconds) with the lungs to changes in pH

Helps maintain the normal blood pH (7.35- 7.45)

1) Bicarbonate- Carbonic Acid

2) proteins

3) phosphate

 found inside all the cells of the body

1) bicarbonate- carbonic acid

2) hemoglobin (Hb)- found only inside the rbcs

3) proteins

4) phosphate

buffer system of both the extracellular and intracellular fluids.

reacts quickly to changes in the amount of carbonic acid or bicarbonate present in body fluids

one of the main buffers of plasma in th extracellular fluid

regulated by two organs:

- the immediate response of the lings by controlling ventilation and carbon dioxide excretion.

- bicarbonate reabsorption and hydrogen ion excretion by the kidneys.

this buffeer system works by using hydrogen ions to react with bicarbonate to form carbonic acid

this minimizes pH changes.

carbonic acid; weak acid (proton donor)

bicarbonate; conjugate base ( proton acceptor)

main buffer system inside rbcs. present in high concentrations in rbcs.

Hb binds either CO2 or hydrogen ions made from cell metabolism to minimize pH changes in the body.

exchange of blood gases.

binds, transports, and release O2 to the tissues.

binds, transports, and releases carbon dixoide in the lungs

one of the main buffers inside the cells (intracellular fluid) and plasma ( extracellular fluid)

made up of a series of amino acids that have side groups. some of these side groups can regulate acid-base balnace.  they have either a positive or neg charge.

negatively charged amino acids can then bind hydrogen ions to help minimize pH balance changes.

important buffer system of:

Extracellular fluid: RBCs and plasma

Intracellular fluid: inside all body cells

Kidney: Urine

help maintain  and regulate the pH in the extracellular fluid and within cells

Diffusion of gaseous CO2 from plasma and the RBCs to teh alveoli for excretion

the rate of the air exchange between the lungs.

O2 is inhaled, and CO2 is exhaled from the lungs

supply oxygen to tissue cells for normal metabolism.

maintain normal pH by excreting or retaining CO2

hyperventilation- faster and deeper breathing.

this decreases CO2 and H+ in the extracellular fluid.

hypoventilation: slower and shallow breathing.

this increases CO2 and H+ in the extracellular fluid.

end products of aerobic glucose metabolism:

CO2, H20, and ATP

for one molecule of glucose metabolized:

O2 is consumed

CO2 is produced

fluid facilitates the diffusion of gaseous carbon dioxide out of the interstitial fluid and into the plasma.

as CO2 diffuses into plasma, the plasma Pco2 increases.

This increase in the Pco2 facilitates the diffusion of a large amount (89%) of CO2 inside RBC

The small amount (11%) of gaseous CO2 stay in plasma

1% - bound to free amino groups of plasma protein

5%- converted to bicarbonate

5%- converted to carbonic acid

5%- dissolved gaseous CO2

21%- bound to globin portion of Hb

63%- reacts with water to form carbonic acid

the simultaneous exchange of chloride ions into the RBC for bicarbonate ions out of the RBC

helps decrease the Pco2 inside the RBCs by removing CO2 as bicarbonate ions

oxygen doesnt easily dissolve in water

1.5% of inhaled O2 is dissolved in plasma.

98.5% of blood O2 is bound to hemoglobin inside the RBC

oxyhemoglobin is the primary form of transport of oxygen

the estent of oxygen binding to hemoglobin

Increases in blood flow to the tissues

cells use oxygen to carry out metabolic reactions

factors that affect O2 binding to Hb:

Bohr Effect

- changes in pH CO2 H+

- acids produced from cell metabolism

- excretion of acids as CO2 in the lungs

temperture

Lactic acid from excercise and oxidation of pruvate

carbonic acid from glucose metabolism

acids produced from metabolism increases both carbon dioxide and hydrogen ion concentrations

Factors that affect oxygen binding to Hb:

Temperature

generated from cell metabolism and muscle contraction

elevated body temps increases metabolism, delivery of oxygen to the cells, and release of O2 from Hb

Lower body temperature decreases metabolism, deliver of oxygen to the cells, and release of O2 from Hb

Factors that affect oxygen binding to Hb:

2,3- Diphosphglycerate

found inside RBCs

metabolic by product of glucose metabolism

regulated by: high altitiudes and body hormones (thryoxine, growth homrone, epinephrine, norepinepherine, and testosterone)

facilitates O2 release from Hb by binding two beta chains of Hb

more O2 is then readily available to cells

reacts slowly to changes in pH ( min to hrs) and persist longer than the other acid base mechanisms

helps maintain the pH of urine between 4.5-8.0

excretes acids as hydrogen ions (acidic urine) and base a bicarbonate ions ( basic urine)

hydorgen ions neutralized by buffer systems  found in urine: bicarbonate- carbonic acid, ammonia-ammonium, phosphate, urate and citrate

reabsorption of bicarbonate into blood

generation and reabsorption of bicarbonate into blood

phosphate buffer

ammonia- ammonium buffer

- account for 60% excretion of hydrogen ions from acids in the form ammonium ion

both gaseous ammonia and hydrogen ions aer then excreted into urine

increases excretion of acids and reabsorption of bicarbonate when the pH decreases

decreasing excretion of acids and increasing excretion of bicarbonate when pH increased

in acid- base imbalances screening test along with arterial blood gas (ABG)

Measures the conc. of key electrolytes in the body: Na+, Cl-, K+, and HCO3-

bicarbonate conc. is reported as total CO2 in a serum electrolyte test

 a drect measure of the conecetration of unmeasured acid anions in blood

calucalated as the difference between the measured cations and the measured anions

increase in the anion gap result indicates metabolic acidosis

anion gap> 12mmol/L

test measures acid-base balance and oxygenation status in the blood.

Evaluates gas exchiange in the lungs by measuring the dissolved gases in arterial blood as: pH Po2 and So2

screening test

reference range: 7.35-7.45

caulated from abg results using Henderson Hasselbach equation

pH= Pka+log([hco3]/[h2co3])= 6.1+ (log[hco3]/(Pco2 x 0.0301))

Measures how much oxygen hemoglobin is carrying as a percentage of the maxium it could carry

formula:

So2= [Hb-O2]/[Hb-O2]+[Hb] x 100%= [Oxyhemoglobin]/Total Hb x 100%

Samples should be analyazed immediately.

if it is not analyzed within 30 minutes, it shoul be sotred on ices and analyzed within one hour from collection of sample

painful procedure due to puncture site

preanalytical errors due to puncture sites

air bubbles in sample: increases oxygen adn decreased carbon dioxide

too much anticoagulant- dilutes blood and increases Pco2

improper mixng of sample with anticoagulant or clotting of sample- incorrect results

improper storage during transport lowers the pH due to glycolysis- increase carbon dixoide, decrease oxygen

indentification and handling of collected samples

improper calibration and maintenance of instrumentation

collecting venous blood rather arterial blood

measures all buffers in the blood: Hb, proteins, phosphate, and bicarbonate-carbonic acid

it measures the deviation of all blood buffers in a patient sample.

Base excess is affected by blood lactate and organic acids that accumlulate during and after excercise.

a positive value is also called "base deficit"

a negative value indicates acidosis

A positive value base indicates alkalosis

Clinical Significance

Acidosis/ Acidemia

excess amount of acids in the blood is a result of

increased acid production from metabolism

decreased acid excretion via the lungs or kidneys

increased excretion of base via the kidneys

*acidosis occurs when arterial pH falls below 7.35*

Clinical Significance:

Alkalosis

excess accumulation of base in the blood as a resultof:

decreased excretion of base by the kidneys

increased excretion of acids via the lings or kidneys

*alkalosis occurs when pH of the blood exceeds 7.45*

excess carbon dioxide retention

disorders prevent normal excretion of CO2

pH <7.35 and Pco2> 40mm Hg

HCO3- >24 mEq/L

central nervous system depression from drugs, injury, and/or disease

asphyxia

hypoventilation due to pulmonary, cardiac, musculoskeletal or neuromuscular disease

Excess carbon dixoide excretion

pH>7.45 and Pco2 <40mm Hg

HCO3- < 24 mEq/L

Hyperventilation due to anxiety, pain, or improper ventilation settings

Respiratory stimulation by drugs, disease, hypoxia, fever

gram-negative bacterial infections

kidneys increase excretion of bicarbonate

this causes rentention of acids in the blood

pH<7.35 and Pco2<40mm Hg

Bicarbonate depletion due to renal disease, dirrhea

Excessive production of organic acids due to liver disease

Endocrine disorders including diabetes mellitus, hypoxia, shock, and drug toxicity

kidneys decrease excretion of bicarbonate

this causes excretion of acids from the blood

pH>7.45 and Pco2> 40mm Hg

HCO3- >24mEq/L

Excessive excretion of acids due to renal disease

loss of gastric hydrochloric acid from prolonged vomiting of gastric sunctioning 

 loss of potassium due to increase renal excretion as a result of diurectics or steroid use.

excessive alkali ingestions (antacid)

* the most common type of metabolic acidosis*

excess production or diminish removal of lactic acid from the blood

caused by inadequate Oxygen delivery

caused by: shock, cardiac arrest, severe anemia, carbon monoxide poisoning, and hypoxia

has adequate oxygen delivery

caused by: epileptic seizures, cyanide poisoning, strokes, uncontrolled diabetes mellitus, and liver failure