ACID-BASE DISORDERS. NITIN BHATT, M.D. DIRECTOR, I.C.U. VAMC, RENO . ACID_BASE DISORDERS. 12000 to 15000 mEq of volatile acids are produced daily by body and excreted as CO2 by lungs
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NITIN BHATT, M.D.
METABOLIC ACIDOSIS = HCO3 <24 OR Anion Gap >12
METABOLIC ALKALOSIS = HCO3 >24
RESPIRATORY ALKALOSIS = PCO2 <40 or PCO2 less than expected for primary metabolic abnormality.
RESPIRATORY ACIDOSIS = PCO2 >40 or PCO2 higher than expected for primary metabolic abnormality.
HIGH ANION GAP (>12-20) always indicates primary metabolic acidosis.
We do not compensate for abnormality of one system with compensation by the same system( MET OR RESP).
MET. ACIDOSIS LOWER HCO3 LOWER PCO2
MET. ALKALOSIS HIGHER HCO3 HIGHER PCO2
RESP. ACIDOSIS HIGHER PCO2 HIGHER HCO3
RESP. ALKALOSIS LOWER PCO2 LOWER HCO3
REMEMBER: compensatory response never brings the pH back to normal, therefore, if the pH is in acidic direction, it tells you that the process or processes in acidic direction are the primary disorders.
ACUTE: 10 INCR. IN PCO2 LEADS TO 1 INCR. IN HCO3
CHRONIC: 10 INCR. IN PCO2 LEADS TO 3-3.5 INCR. IN HCO3
ACUTE; 10 DECR. IN PCO2 LEADS TO 2 DECR. IN HCO3
CHRONIC 10 DECR. IN PCO2 LEADS TO 4-5 DECR. IN HCO3
PCO2 = LAST 2 DIGITS OF pH
1 MEQ INCR. IN HCO3 LEADS TO 0.6-0.7 INNCR. IN PCO2
HENDERSON HASSELBALCH EQUATION
Ph = Pk + log HCO3/ H2CO3
Rearranging the above per Kassier and Bliech
H = 24 X PCO2/HCO3 ( H= Hydrogen ion conc.)
H at normal pH of 7.40 is 40 Nanamol/Liter
therefore, 40 = 24 X 40 (PCO2)/24(HCO3)
SYSTEMATIC ANALYSIS OF ACID-BASE DISORDER
Proximal RTA, acetazolamide,coumarin/ Distal RTA
Diarrhea, Pancreatic fistula, Biliary drainage
Ureterosigmoidostomy, Ileal bladder
HYPERKALEMIC OR NORMOKALEMIC
( saline responsive )
Chloride wasting diarhhea
Colonic villous adenoma
Remote diuretic therapy
Poorly reabsorbed anions
Greater than 20 mEq/l
( saline unresponsive )
Exogenous steroids/ Licorice
Adrenal 11 or 17 hydroxylase defects
Liddle`s /Barter`s syndromes
K and Mg deficiency
Milk alkali syndromeUrinary chloride in metabolic alkalosis
An acutely ill 50 yr. old woman with a history of vomiting x 4 days is brought to E.R. P/E shows profound lethargy, P= 120, RR=12, BP 80/50. Lab: Na=140, K=3.3, Cl=85, HCO3=25, PCO2=41 and pH=7.40.
Most likely acid-base disorder is
A) metabolic acidosis
B) metabolic alkalosis
C) respiratory acidosis and metabolic alkalosis
D) respiratory alkalosis
E) metabolic acidosis and metabolic alkalosis
A 65 yr old homeless woman who collapsed in a pub is brought to E.R. P/E: comatose,P=120,BP=58/40.IV N.S. started 10 min.earlier,Pt. Now intubated. I.V. bicarbonate was given with fluids, and Dopamine was started but hypotension persists
Hct=36%, Glu=85, Na=138, K=3.3, Cl=97, HCO3=35, BUN=25, Cr.=1.2,
Urine pH=6.8, Urine Cl=8 meq/L and Urine K=42 meq/L