Page 1 of 3: FAQ: How to crack acid base questions?

tanmay_mehta · Credits: 16561 My Scrapbook My Reading List 3 Books

Acid-base is not as difficult as it seems if you follow a structured approach. Using the Henderson-Hasselbalch equation: [H+]∞ P CO2/[HCO3-], it is clear that either a rise in CO2 or a fall in bicarbonate will make the blood more acidic (i.e. H+ rises or pH lowers). When you are faced with an acid-base problem, or some arterial blood gas results, follow these steps:
1. Look at the pH first and establish if there is an acidosis or an alkalosis.
2. If there is a disturbance in pH, ask yourself if it can it be explained by a change in CO2, e.g. if you have identified an acidosis, is CO2 raised? If the pH change can be explained by a corresponding change in CO2 then the disturbance is respiratory. If not, then it is a change in bicarbonate that has caused the disturbance and you are dealing with a metabolic disorder.
3. Then look at whether compensation has taken place. Compensation in respiratory disturbances is simply an attempt by the renal system to bring pH back to normal. So look at bicarbonate and using the equation above establish whether bicarbonate has moved to bring the ratio back to normal, or in the opposite direction. In a compensated respiratory acidosis, bicarbonate would also rise.

zolt · Credits: 9171 My Scrapbook My Reading List 40 Books

Here's how i do it.
normal levels:
pH = 7.35 TO 7.45
pCO2 =35 TO 45
HCO3- = 22 to 28
now
1.if pH<7.35 = ACIDOSIS
if pH >7.45 =ALKALOSIS
2.In acidosis pCO2 IS INCREASED AND HCO3- IS DECREASED.
Viceversa in alkalosis.
3.now look where is the match ie:does pCO2 match or HCO3- matches with the corresponding metabolic abnormality(ie: acidosis or alkalosis)This will be the primary metabolic abnormality and the one which does not match will be the compensated one.
4.Remember pCO2 = RESPIRATORY
HCO3- = METABOLIC
5.Based on the above facts you have found out the metabolic abnormality.

tanmay_mehta · Credits: 16561 My Scrapbook My Reading List 3 Books

plz explain topic 3 more clearly

zolt · Credits: 9171 My Scrapbook My Reading List 40 Books

drada · Credits: 45652 My Scrapbook My Reading List 2 Books

hea,thanks both of u

tanmay_mehta · Credits: 16561 My Scrapbook My Reading List 3 Books

great help zolt

good buddy

keep it up

tanmay_mehta · Credits: 16561 My Scrapbook My Reading List 3 Books

SO LET ME SUM UP THE WHOLE TOPIC

ACID –BASE FUNDA’S
-----Acidosis-----------------(
(Lt.side) CO2 + H2O--------( H2CO3--------( H+ + HCO3- (Rt.side)
(----Alkalosis------------------

EXPECT FOR THE COMPENSATION, THE
BASIC RULE = ACIDOSIS= DECREASED PH / INCREASE [H+] / LOSS OF HCO3-
= ALKALOSIS= INCREASED PH / DECREASED [H+] / Decreased PCO2

Lung Compensate for==
1. For Metabolic Acidosis by Decreasing PCO2 (by Hyperventilation)
(2) For Metabolic Alkalosis by Increasing PCO2 (by Hypoventilation)

Kidney Compensate for==
(1) For Respiratory Acidosis by Increasing HCO3- Reabsorption.
(2) For Respiratory Alkalosis by Decreasing HCO3- Reabsorption.

Always look for [HCO3-] / [PCO2]==

(1) Uncompensated / simple conditions==( any one of these can be the fes. But only one of these…)
= Normal/ Increase
= Normal/ Decrease
= Increase/ Normal
= Decrease/ Normal
1. Compensated conditions==
= Increase/ Increase
= Decrease/ Decrease
1. Mixed i.e. (Both Respiratory and metabolic Acidosis or Alkalosis)==
i.e. Metabolic Acidosis and Respiratory Acidosis=[HCO3-]/ PCO2== Decrease/ Increase
Metabolic Alkalosis and Respiratory Alkalosis=[HCO3-]/ PCO2== Increase/ Decrease
Things to look for (in order)=
1. PH (N=7.38-7.44)
2. PCO2 (N=35—45)
3. [HCO3-] (N=21—30)
4. [HCO3-]/ PCO2

Respiratory Acidosis=simple/uncompensated
1. PH (N=7.38-7.44) == Decrease
2. PCO2 (N=35—45)== Increase
3. [HCO3-] (N=21—30)== Normal
4. [HCO3-]/ PCO2== Normal/ Increase

Respiratory Acidosis= compensated
1. PH (N=7.38-7.44)== Normal
2. PCO2 (N=35—45)== Increase
3. [HCO3-] (N=21—30)== Increase
4. [HCO3-]/ PCO2== Increase/ Increase

Respiratory Alkalosis=simple/uncompensated
1. PH (N=7.38-7.44)== Increase
2. PCO2 (N=35—45)== Decrease
3. [HCO3-] (N=21—30)== Normal
4. [HCO3-]/ PCO2== Normal/ Decrease

Respiratory Alkalosis= compensated
1. PH (N=7.38-7.44)== Normal
2. PCO2 (N=35—45)== Decrease
3. [HCO3-] (N=21—30)== Decrease
4. [HCO3-]/ PCO2== Decrease/ Decrease

Metabolic Acidosis=simple/uncompensated
1. PH (N=7.38-7.44)== Decrease
2. PCO2 (N=35—45)== Normal
3. [HCO3-] (N=21—30)== Decrease
4. [HCO3-]/ PCO2== Decrease/ Normal

Metabolic Acidosis= compensated
1. PH (N=7.38-7.44)== Normal
2. PCO2 (N=35—45)== Decrease
3. [HCO3-] (N=21—30)== Decrease
4. [HCO3-]/ PCO2== Decrease/ Decrease

Metabolic Alkalosis=simple/uncompensated
1. PH (N=7.38-7.44)== Increase
2. PCO2 (N=35—45)== Normal
3. [HCO3-] (N=21—30)== Increase
4. [HCO3-]/ PCO2== Increase/ Normal

Metabolic Alkalosis=Compensated
1. PH (N=7.38-7.44)== Normal
2. PCO2 (N=35—45)== Increase
3. [HCO3-] (N=21—30)== Increase
4. [HCO3-]/ PCO2== Increase/ Increase

zolt · Credits: 9171 My Scrapbook My Reading List 40 Books

absolutrly. Great effort to simplify this this thing.

tanmay_mehta · Credits: 16561 My Scrapbook My Reading List 3 Books

let's discuss causes of acidosis and alklosis......

zolt · Credits: 9171 My Scrapbook My Reading List 40 Books

ok
here's the imp. one.(asked in exams)
causes of metabolic acidosis with increased anion gap:
uremia
DKA
Phenformin toxicity
Iron tablets
Lactic acidosis
Salicylate toxicity
Alchohol toxicity

with Normal anion gap:
diarrhoea
Ureterosigmoidoscopy

		Sign In New User? Sign Up Sign in to access your control panel and messenger!
				TechZone \| SpiderNevi \| HowTo? \| Scrapbook!