BLOOD GASES CCHM Flashcards by Queenie Mae

substance that can yield a hydrogen ion (H) or hydronium ion when dissolved in water
represents (+) charge molecules

Acids

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substance that can yield hydroxyl ions (OH)
represents (-) charge molecules

Base

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combination of a weak acid or weak base and its salt, is a system that resists changes in pH
Effectiveness of a buffer is determined based on:
1.
2.

Buffer
1 Ionization constant/ pKa of the
buffering system
2 pH of the environment

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Function: maintain or prevent sudden
fluctuations in pH

Buffer

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Major buffer system:

Plasma – bicarbonate
carbonic acid buffer system; pK of 6.1

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Normal blood pH: ___, to achieve this the body uses buffers

7.35-7.45

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BUFFER SYSTEMS

1 BICARBONATE-CARBONIC ACID BUFFER SYSTEM
2 PHOSPHATE BUFFER SYSTEM
3 HEMOGLOBIN-OXYHEMOGLOBIN BUFFER SYSTEM
4 PROTEIN BUFFER SYSTEM

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BUFFER SYSTEMS

1 BICARBONATE-CARBONIC ACID BUFFER SYSTEM
2 PHOSPHATE BUFFER SYSTEM
3 HEMOGLOBIN-OXYHEMOGLOBIN BUFFER SYSTEM
4 PROTEIN BUFFER SYSTEM

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Principal mammalian buffer system

BICARBONATE-CARBONIC ACID BUFFER SYSTEM

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Acids combine with Bicarbonates in the blood

Neutral Salts (Bicarbonate Salts) –
conjugate base
Carbonic Acid (Weak Acid)

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BICARBONATE-CARBONIC ACID BUFFER SYSTEM

Acids combine with Bicarbonates in the blood

Neutral Salts (Bicarbonate Salts) –
conjugate base
Carbonic Acid (Weak Acid)

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Bicarbonate
Form:
Regulation:

Bicarbonate
Through Kidney renal regulation

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Carbonic acid (unstable)
Form
Regulation

Changes to H2O and CO2 once it reaches the plasma.
Measurement: based on pCO2

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Carbonic acid (unstable)
Form
Regulation

Changes to H2O and CO2 once it reaches the plasma.
Measurement: based on pCO2

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____ unstable, changing to H2O and CO2 in fluid

H2CO3

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Primary utilization is in RBCs. It is 16% of the non-bicarbonate buffer value of erythrocytes It increases the amount of ____ in ECF (more alkaline)

PHOSPHATE BUFFER SYSTEM
NaHCO3

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_____ is a negatively charged molecule which makes blood pH to be more ____, but still maintaining the normal blood pH

Sodium bicarbonate (NaHCO3)
alkaline

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In PHOSPHATE BUFFER SYSTEM , ____ phosphate form that acts as a buffer

2,3-diphosphoglycerate

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In PHOSPHATE BUFFER SYSTEM , ____ phosphate form that acts as a buffer

2,3-diphosphoglycerate

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maintains pH level (Venous and Arterial Blood)
____ is considered to be an effective buffer because it is responsible for carrying oxygen so it has the ability to off load ___ replacing it with ___
- helps in the maintenance of CO2; it facilitates its diffusion across different gradients
____ carries ____.
Each mole of Hgb binds with ____ (primarily more than 95% of Hgb binds with O2)

HEMOGLOBIN-OXYHEMOGLOBIN BUFFER SYSTEM
Hemoglobin
O2
CO2
1 gram of Hemoglobin
1.39 mL of Oxygen
1 mole of O2

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Proteins can also help in maintaining the buffer due to charges present on their surfaces. Proteins are made up of ____ which has ___ and ____; consisting of (+) and (-) charge end.
Proteins can exist in 2 forms: ___, ___ > Their characteristics depend on the pH of the environment
• More (+) in _____ environment
•More (-) in ___
•Has capability to bind or release excess Hydrogen as required within blood circulation
Plasma proteins (Charges on their surface)
o pH > pI –
o pH < pI –

PROTEIN BUFFER SYSTEM
amino acids
carboxyl end
amino end
H+ protein
B Protein
acidic
basic/alkaline
(-) charge
(+) charge

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second largest fraction of the anions in the plasma.
Conjugate base representative of major buffer system
Classified under electrolytes.
It includes: ___ and _____

BICARBONATE (HCO3)
ionized bicarbonate (HC03)
Bicarbonate molecules linked with amino acid:

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second largest fraction of the anions in the plasma.
Conjugate base representative of major buffer system
Classified under electrolytes.
It includes: ___ and _____

BICARBONATE (HCO3)
ionized bicarbonate (HC03)
Bicarbonate molecules linked with amino acid:

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measured to determine pH

ionized bicarbonate (HC03) –

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measured to determine pH

ionized bicarbonate (HC03) –

carbonate and the carbamino compounds. Normal range is from ___

Bicarbonate molecules linked with amino acid 21 - 28 mmol/L (21 - 28 meq/L)

carbonate and the carbamino compounds. Normal range is from ___

Bicarbonate molecules linked with amino acid 21 - 28 mmol/L (21 - 28 meq/L)

Weak acid representative of major buffer system readily dissociated into ___ and ___ once it reaches the blood circulation This fraction of blood, plasma or serum includes the ___ and ___ In blood circulation, CO2 concentration is ____ than HCO3, the symbol cdCO2 (conc. of dissolved C02) is frequently used and measured from ___ Other references: the complete solubility coefficient is ____ Normal range: ____

CARBONIC ACID (H2CO3) H2O CO2 undissociated carbonic acid physically dissolved anhydrous C02 higher pCO2 multiplied by the solubility coefficient (0.03) of CO2. 0.0307 or 0.0306 1.05 –1.45 mmol/L.

pressure or tension exerted by C02 gas dissolved in blood It is an index of efficiency of gas exchange in the lungs and not a direct measurement of total CO2 concentration in the blood. Function: used to determine (H2CO3) level by multiplying it with solubility coefficient  Normal range: ____

PARTIAL PRESSURE OF C02 (PCO2) 35 - 45 mmHg.

Amount of CO2 bound within the blood circulation depending on the sample used The value of the CO2 combining power Is an index of the amount of CO2 that can be bound by serum, plasma, or whole blood as HCO3 at a ____ of ___ at ____ degree celsius Normal range: ___

CARBON DIOXIDE COMBINING POWER (CO2 COMBINING POWER) pCO2 of 40 mmHg at 25 degrees Celcius. 24 - 30 mmol/L.

Formerly known as ____ Sum of major buffer system or total concentration of C02 in the blood consisting of ionized HC03, C03, carbamino compound) and unionized fraction (H2C03) and physically dissolved C02. Normal range: ____

TOTAL CARBON DIOXIDE CONCENTRATION (ctCO2) -C02 content 21-28 mmol/L.

The negative logarithm of hydrogen ion activity with a normal average range of 7.35-7.45

MAJOR FACTORS REGULATING BLOOD PH: in order to prevent drastic fluctuation in pH, and second line which acts when major disturbances, changes or deviations from normal pH occurs.

Primary line 1) Chemical buffers (with charges) > bicarbonate and carbonic acid buffer system >proteins >Hemoglobin >Electrolytes (Cl and HCO3) Second line Second line 2) Respiratory regulatory mechanism > increased release of CO2: thru respiration or decreasing the exhalation > Decreased release of CO2: thru decreasing the respiratory rate 3) Renal regulatory mechanism – kidney which regulates level of bicarbonate (HCO3)

used to measure blood pH

HENDERSON-HASSELBALCH EQUATION ph= bicarbonate/ carbonic acid

may not be encountered by MTs anymore because there are other healthcare professionals that are responsible for this procedure as they are capable and trained to perform.

BLOOD COLLECTION FOR BLOOD GAS AND PH ANALYSIS

Keep the sample at ___technique in blood collection; at least prevent its exposure to ambient air because the concentration of ___ and ___ is different in blood and in air.

anaerobic O2 and CO2

Keep the sample at ___technique in blood collection; at least prevent its exposure to ambient air because the concentration of ___ and ___ is different in blood and in air.

anaerobic O2 and CO2

Preferred sample:______ ____ is the more preferred specimen for blood gas analysis because it is of more uniform composition than venous blood. This is due to the metabolic diversity

whole blood Arterial blood

These specimens can also be used for blood gas analysis provided that they undergo arterialization.

Venous and Capillary (Skin punctured) Blood

___ used as an alternative if arterial sample from the patient cannot be possibly collected or if the patient does not have arterial cannula yet.

Arterialized capillary blood

_____ process by which vasodilation is induced to maintain good blood flow. Sample from capillary puncture undergoing arterialization will be near arterial sample.

Arterialization

Procedure of Blood gas analysis Warm up first the area of blood extraction. (i.e in finger/heel stick, dip it first in water bath with ____ and leave it for at least ____  Alternative: _____

42oC temp 10mins. use warming pad

Exceptions in Arterialization  If patients have low blood pressure: ____ Conditions which induce _____  Patients undergoing ___  ____

systolic with <95mmHg vasoconstriction O2 therapy Newborns with Respiratory Distress Ssyndrome (RDS)

______ is preferred than venous blood because it is a mixture of venous and arterial blood.

Capillary (Skin punctured) blood

_____ is a very delicate procedure because arteries are always situated next to a nerve. Incorrect procedure may damage a nerve or dangerous effects to patient may occur.

Arterial blood gas collection

Ideal syringe (but not used anymore): _____ less porous than plastic syringe so it lessens amount of exposure and difference in amount of CO2 and O2 in ambient air.

glass syringe

Anticoagulant: ___ powdered . The use of liquid is not advisable because it causes dilution of sample.  Always follow anaerobic technique.

heparin (lyophilized/freeze dried) –

___ Method  ______  Principle: Based on amperometric or polarographic measurement of oxygen.  Gasometric analysis  Calculation from oxygen saturation, pH and temperature by means of the standard O2 dissociation curve.

pO2 partial pressure of oxygen ISE Clark/e p02 electrode

___ non-invasive method where patients stay in the hospital and put up with an electrode with gel casing which maintains temperature in certain portion of skin between ____ causing arterialization of capillaries; thus measuring O2

Transcutaneous monitoring 43o-44oC

Use of ______  Principle: Based on pH measurement of a stationary NaHCO3 solution which is in equilibrium with the test solution and the test via a CO2 permeable membrane.  Gasometric analysis  Use of _____ -from pH and total carbon dioxide. From a measured pH value interpolated in the C02 equilibrium curve

partial pressure of carbon dioxide PCO2 pCO2 electrode (Severinghaus electrode) Henderson Hasselbach equation

___  Principle: Based on polarographic principle ____– used as mathematical derivation for determining pH based on pCO2 and HCO3 level  Use of PH meters  Nomogram and Slide Rule  Siggard -Anderson Alignment nomogram

PH electrode Henderson - Hasselbach equation

______  Principle: Carbon dioxide is released frontHC03 by the addition of lactic add. The C02 and other gases are extracted under a partial vacuum. The pressure difference at constant value before and after absorption of C02 by NaOH Is the amount of C02 present in the sample.

CT C02 Manometric Method Using Natelson Microgasometer

2 Types of Gasometric Analysis vary depending on the volume of blood sample which will be utilized

Macrogasometric method – >1mL of sample  Microgasometric method - <1mL of sample

Gasometric Analysis

 Natelson Gasometric Analysis  Van Slyke Gasometric Analysis

Chemicals are used to liberate the different blood gases; and specific chemicals to differentiate which is O2 and CO2

 Natelson Gasometric Analysis

Principle: Involves the release of CO2 gas when the sample is added to H2S04 with subsequent monitoring of this release with a pair of pCO2 electrodes (reference and sample electrodes). The rate of change in pH of the buffer inside the pCO2 electrodes is a measure of the concentration of its CO2 in the sample  Same methodology which involves replacement of ____ of ___ for the release of CO2 gas.  Same with ___ which has reference and sample electrode so the measurement is also done through electrochemical analysis

ALTERNATIVE METHOD lactic acid with sulfuric acid (H2SO4) ISE

Conditions for Blood Gas Analysis:

1. All procedures should be considered “STAT” 2. Specimen must be kept at anaerobic condition Specimen w/c cannot be analyzed immediately must be placed in an ice slurry (done but not advisable)

Should have short TAT; test procedure must be performed within an hour after blood extraction.  If delayed 20-30 mins: pH lowers by ___  Avoid glycolysis

All procedures should be considered “STAT” 0.01

conversion of glucose into acetyl coA, further proceeding to production of ATP (end product together with CO2 and H2O). Since there is CO2, this has an effect to blood gas analysis

Glycolysis

O2 at ambient air could enter the sample which can cause a decrease.  If the sample is exposed to O2, blood will take up O2 and will ↓ pCO2 = ↓ H2CO3 = ↑ pH or making the pH level of sample to have higher than normal pH  Use plastic syringe (but POCT is still preferred) Winged blood collection set is not advisable to use.

Specimen must be kept at anaerobic condition

ACID-BASE DISTURBANCES:

Acidosis ( <7.35) Alkalosis ( >7.45)

General term applied for the any condition where the pH of the blood and the bicarbonate concentration of the blood are below normal.

Acidosis ( <7.35)

General term applied for any condition with an increase in blood pH (above normal range) characterized by an elevation in the H+ ion accepting buffer of the plasma (UC03) and a reduction in the H+ ion substances (H2CO3)

Alkalosis ( >7.45)

Metabolic affects HCO3

Metabolic Alkalosis ↑  Metabolic Acidosis ↓

Respiratory affects H2CO3

Respiratory Alkalosis ↑  Respiratory Acidosis ↓

– either excretion or reabsorption

Metabolic

either retention by decreasing or increasing exhalation of CO2 which is affected based on the rate of respiration__ AND ___

Respiratory Hyperventilation  Hypoventilation

caused by bicarbonate (HCO3) deficiency Production of increased amount of acid ___,_____,_____,_____ Compensation: ____

Metabolic Acidosis diabetic ketoacidosis, lactic acidosis (alcoholism), renal failure and diarrhea Hyperventilation

compensated by respiratory

Metabolic

compensated by alkalosis  To induce alkalosis, decrease the carbonic acid, therefore pCO2 must be decreased by ensuring that there is greater exhalation of CO2 thru hyperventilation  ↑ respiratory rate = ↑ release of CO2 thru respiration = ↓ CO2 conc. in blood circulation.

Acidosis

____ and ____ as the body’s  response to increased positively charged molecules. If you’re increasing bicarbonate (anion), it must be replaced with Cl molecule causing hyperchloremia (except in ____ which has normal Cl level)  In _____, there is an ↑ H+ ions.

Metabolic Acidosis Hyperkalemia hyperchloremia diabetic ketoacidosis acidosis

caused by bicarbonate excess Conditions: Vomiting with the loss of ____ from the stomach  If there’s a decrease of chloride, there must be a replacement of same charge which is reabsorption of bicarbonate Compensation: _____   Metabolic → compensated by respiratory  Alkalosis → compensated by acidosis  To induce acidosis, increase the carbonic acid by increasing pCO2 by decreasing exhalation/ respiratory rate through hypoventilation (+) hypokalemia, hypochloremia  For every 10 meq/L rise in bicarbonates, the pCO2  rises by 6 mmHg

Metabolic Alkalosis chloride Hypoventilation

caused by bicarbonate excess Conditions: Vomiting with the loss of ____ from the stomach  If there’s a decrease of chloride, there must be a replacement of same charge which is reabsorption of bicarbonate Compensation: _____  Metabolic → compensated by ___  Alkalosis → compensated by ____ >To induce it, increase the carbonic acid by increasing pCO2 by decreasing exhalation/ respiratory rate through its compensation. (+) ___ and _____ For every ___ rise in bicarbonates, the pCO2  rises by____

Metabolic Alkalosis chloride Hypoventilation respiratory acidosis hypokalemia hypochloremia 10 meq/L 6 mmHg

Excessive CO2 accumulation Conditions: ____, ___,____,_____ overdose ____,____,___ pneumonia >Common to these conditions are the lowered effectiveness of lungs in terms of releasing CO2 thru respiration Compensation: retention of ____ >Induce metabolic alkalosis: to induce, increase bicarbonate by reabsorption/ retention Bicarbonate rises ___ for each ____rise in pCO2

Respiratory Acidosis Chronic obstructive pulmonic disease (COPD), myasthenia gravis, CNS disease, drug morphine, barbiturates and opiates bicarbonates 1 meq/L 10 mmHg

Due to excessive carbon dioxide loss  Conditions (which causes ____): Anxiety, severe pain, aspirin overdose, hepatic cirrhosis, during blood extraction  Compensation: _____ >Induce metabolic acidosis: to induce, decrease bicarbonate by excreting more thru kidney function  (+) ____ – potassium is excreted together with bicarbonate, leading to reabsorption of Na and Cl molecule  Bicarbonate falls ___ for each ___ fall in pCO2

Respiratory Alkalosis hyperventilation decreased reabsorption Hypokalemia 2 meq/L 10 mmHg

In Alkalosis, ____ ensues due to. _____, which can lead to death because of respiratory muscle spasm.

tetany hypocalcemia

In Alkalosis, ____ ensues due to. _____, which can lead to death because of respiratory muscle spasm.

tetany hypocalcemia

In Acidosis, there is an inhibition of the neural mechanisms which will then lead to ____. A blood pH of ____ has been proven fatal

coma 6.9

Arterial Blood Gas ref range pH pCO2 (mm Hg) HCO3 mmol/L Total CO2 content pO2 mmol/L SO2 (%) O2Hb (%)

7.35-7.45 35-45 22-26 23-27 80-110 >95 >95

PARAMETERS OF INTEREST

-Evaluate (normal pH - 7.35-7.45) -Evaluate the ventilation (Lungs) -Evaluate the metabolic Process (kidneys) -Determine which is the Primary (1°) and compensating disorder - Determine the degree of compensation - pO2 = 81 - 100 mmHg (adequate oxygenation)

PARAMETERS OF INTEREST

Evaluate (normal pH - 7.35-7.45)

 <7.35 - acidosis  >7.45 – alkalosis

Evaluate the ventilation (Lungs)

 pC02 - 35 - 45 mm Hg  < 35 respiratory alkalosis  > 45 respiratory acidosis

Evaluate the ventilation (Lungs)

 pC02 - 35 - 45 mm Hg  < 35 respiratory alkalosis  > 45 respiratory acidosis

Evaluate the metabolic Process (kidneys)

 HC03 = 22-26 meq/L  < 22 - metabolic acidosis  >26 – metabolic alkalosis

Determine which is the Primary (1°) and compensating disorder

Determine the degree of compensation

 non- compensatory  partial compensatory  complete compensation

pO2 = 81 - 100 mmHg (adequate oxygenation)

 p02 Hypoxemia:  mild = 61 - 80  moderate = 41 - 60  severe = 40 or less

pO2 = 81 - 100 mmHg (adequate oxygenation)

 p02 Hypoxemia:  mild = 61 - 80  moderate = 41 - 60  severe = 40 or less

pH is based on HCO3 and H2CO3  H2CO3 = _____

HENDERSON-HASSELBACH EQUATION pCO2 x 0.03 (solubility coefficient; other references: 0.029)

HENDERSON-HASSELBACH EQUATION formula to be used

pH = 6.1 + log HCO3 / pCO2 x 0.03

HENDERSON-HASSELBACH EQUATION Alternative Formula: if incase the given is only tCO2 and pCO2

pH = 6.1 + log tCO2 − (pCO2 x 0.03) pCO2 x 0.03

Representative conjugate base Maintains pH at normal level Measured directly ___: renal regulatory mechanism

Bicarbonate (HCO3-) kidney

Weak acid Not directly measured; it is measured thru the breakdown products specifically pCO2 (representative of H2CO3) tCO2 = HCO3- + H2CO3 ___: respiratory regulatory mechanism

Carbonic acid (H2CO3) Lungs

body’s mechanism which allows it to revert back the pH level into normal range One buffer system adjusts for the other buffer system which has primary disturbance

Degree of Compensation

Primary Disturbance

HCO3 (22-29mmol/L) Metabolic acidosis <22 mmol/L Metabolic alkalosis >29 mmol/L pCO2 represent H2CO3 (35-45mmHg) Respiratory alkalosis <35 mmHg Respiratory acidosis >45 mmHg

Degree of Compensation

pH pCO2 H2CO3 Non-compensatory A A or N A or N Partial compensatory A A A Complete compensatory N A A

No compensation Either pCO2/ H2CO3 is normal; pH is abnormal  Ex: _______ - pCO2 is abnormal, while H2CO3 did not adjust and is normal. Since this is acidosis, pH in effect will be acidic or in abnormal range.

Non-compensatory Respiratory acidosis

With compensation but insufficient to compensate pH → abnormal pCO2 and H2CO3 are abnormal; pH is abnormal

Partial compensatory

 With sufficient compensation; thus normalizing pH

Complete compensatory

 Evaluate according to the given result based on normal range  ↓ pO2 (<85 mmHg) = ____ – using blood sample; or ___ if O2 source is from oxymeters

Degree of Oxygenation (pO2= 85-105 mmHg) hypoxemia hypoxia Mild >61; <85 Moderate >41; <60 Severe <40

 Evaluate according to the given result based on normal range  ↓ pO2 (<85 mmHg) = ____ – using blood sample; or ___ if O2 source is from oxymeters

Degree of Oxygenation (pO2= 85-105 mmHg) hypoxemia hypoxia Mild >61; <85 Moderate >41; <60 Severe <40