....HOW to calculate BE (base excess or deficit)?
....it requires to know pH, which stands for "potential of hydrogen ion" and is defined as the negative logarithm to the base 10 of hydrogen ion concentration.
....normal pH is 7.35 - 7.45 and the normal hydrogen ion concentration is 40 nmol/L.
....Base excess/deficit of +/- 2 mEq/L is normal. A positive number is called a base excess and indicates a metabolic alkalosis and a negative number is called a base deficit and indicates a metabolic acidosis.
Base Excess / Base Deficit
---------------------------
Calculation of the base excess or deficit is a way of quantifying HCO3 requirement!
...."Base excess is the quantity of base (HCO3 mEq/L) that is above or below the normal range of buffer base in the body (22 -28 mEq/L). This cannot be calculated from PCO2 and pH alone as the hemoglobin also contributes to the buffer base. One can use the Siggaard-Andersen nomogram to estimate base excess or deficit. Another way is to estimate using the following calculations:"
For example: taking the real figures from an ABG report attached below:
pH 7.17
PCO2 106
PO2 86
BE 5.6
HCO3 38
SaO2 94
Step 1
Find the difference between normal and measured PaCO2 in the ABG report above:
40 - 106 = 66.0 mmHg
Step 2
Move the decimal by two places to the left:
66.0 becomes 0.66
Step 3
If PaCO2 >40 mm Hg subtract half of the above difference and if <40 mmHg add the whole difference to 7.40
Therefore, in the above example, since PaCO2 is greater than 40, half of the difference i.e. 0.66/2 = 0.33 will be subtracted from 7.40
7.40 - 0.33 = 7.07 is the predicted respiratory pH
Step 4
Find the difference between measured and predicted respiratory pH
7.17 - 7.07 = 0.10
Step 5
Move the decimal by two places to the right: 0.10 becomes 10.0
Step 6
Multiply the above value by 2/3:
10 x 2/3 = 6.6
But, the ABG report shows the BE = 5.6 because Haemoglobin and others as buffer have reduced the BE from 6.6 to 5.6 mmol/L.
Base excess/deficit of +/- 2 mEq/L is normal.
Severe metabolic acidosis is associated with a base deficit of -10 mEq/L
A positive number is called a base excess and indicates a metabolic alkalosis.
A negative number is called a base deficit and indicates a metabolic acidosis.
....the above ABG example shows: BE = 5.6 mmol/L and in actuality, bicarbonate is in excess (base excess) due to HCO3 (38 mmol/L) being generated from high PaCO2 = 106 mmHg and does not require Sodibicarb to be administered, though the pH is 7.17, rather simply requires to be hyperventilated to correct the respiratory acidosis.
....the following equation clarifies that in the above ABG, high PaCO2 has generated high amounts of HCO3:
CO2 + H2O = H2CO3 = H + HCO3.
Therefore, this patient does not need to be given Sodibicarb, which can cause intracellular acidosis by releasing CO2, 20 times more soluble than O2, further depressing the CNS; the low pH will get corrected eventually by hyperventilation using Facemask BiPAP if counscious or IPPV following intubation if unconscious!
....the same patient in the above example is showing correction of pH in the second ABG report attached below, simply by hyperventilation using Facemask BiPAP without Sodibicarb!
Acid Base:
https://media.lanecc.edu/users/driscolln/RT127/Softchalk/Acid_Base_Lesson/Acid_Base_Lesson10.html
DESCRIPTION OF pH OR
"ACID-BASE STATUS" IN THE BLOOD:
http://www.anaesthesia.med.usyd.edu.au/resources/lectures/acidbase_mjb/description.html
....it requires to know pH, which stands for "potential of hydrogen ion" and is defined as the negative logarithm to the base 10 of hydrogen ion concentration.
....normal pH is 7.35 - 7.45 and the normal hydrogen ion concentration is 40 nmol/L.
....Base excess/deficit of +/- 2 mEq/L is normal. A positive number is called a base excess and indicates a metabolic alkalosis and a negative number is called a base deficit and indicates a metabolic acidosis.
Base Excess / Base Deficit
---------------------------
Calculation of the base excess or deficit is a way of quantifying HCO3 requirement!
...."Base excess is the quantity of base (HCO3 mEq/L) that is above or below the normal range of buffer base in the body (22 -28 mEq/L). This cannot be calculated from PCO2 and pH alone as the hemoglobin also contributes to the buffer base. One can use the Siggaard-Andersen nomogram to estimate base excess or deficit. Another way is to estimate using the following calculations:"
For example: taking the real figures from an ABG report attached below:
pH 7.17
PCO2 106
PO2 86
BE 5.6
HCO3 38
SaO2 94
Step 1
Find the difference between normal and measured PaCO2 in the ABG report above:
40 - 106 = 66.0 mmHg
Step 2
Move the decimal by two places to the left:
66.0 becomes 0.66
Step 3
If PaCO2 >40 mm Hg subtract half of the above difference and if <40 mmHg add the whole difference to 7.40
Therefore, in the above example, since PaCO2 is greater than 40, half of the difference i.e. 0.66/2 = 0.33 will be subtracted from 7.40
7.40 - 0.33 = 7.07 is the predicted respiratory pH
Step 4
Find the difference between measured and predicted respiratory pH
7.17 - 7.07 = 0.10
Step 5
Move the decimal by two places to the right: 0.10 becomes 10.0
Step 6
Multiply the above value by 2/3:
10 x 2/3 = 6.6
But, the ABG report shows the BE = 5.6 because Haemoglobin and others as buffer have reduced the BE from 6.6 to 5.6 mmol/L.
Base excess/deficit of +/- 2 mEq/L is normal.
Severe metabolic acidosis is associated with a base deficit of -10 mEq/L
A positive number is called a base excess and indicates a metabolic alkalosis.
A negative number is called a base deficit and indicates a metabolic acidosis.
....the above ABG example shows: BE = 5.6 mmol/L and in actuality, bicarbonate is in excess (base excess) due to HCO3 (38 mmol/L) being generated from high PaCO2 = 106 mmHg and does not require Sodibicarb to be administered, though the pH is 7.17, rather simply requires to be hyperventilated to correct the respiratory acidosis.
....the following equation clarifies that in the above ABG, high PaCO2 has generated high amounts of HCO3:
CO2 + H2O = H2CO3 = H + HCO3.
Therefore, this patient does not need to be given Sodibicarb, which can cause intracellular acidosis by releasing CO2, 20 times more soluble than O2, further depressing the CNS; the low pH will get corrected eventually by hyperventilation using Facemask BiPAP if counscious or IPPV following intubation if unconscious!
....the same patient in the above example is showing correction of pH in the second ABG report attached below, simply by hyperventilation using Facemask BiPAP without Sodibicarb!
Acid Base:
https://media.lanecc.edu/users/driscolln/RT127/Softchalk/Acid_Base_Lesson/Acid_Base_Lesson10.html
DESCRIPTION OF pH OR
"ACID-BASE STATUS" IN THE BLOOD:
http://www.anaesthesia.med.usyd.edu.au/resources/lectures/acidbase_mjb/description.html
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