Alok Agrawal MD FASN FNKF Clinical Associate Professor WSU Dayton Ohio Arterial Blood Gas ABGs necessary to correctly diagnose AB disorders Interpret ABG s in conjunction with history PE and labs ID: 775360
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Slide1
Diagnosis of Acid Base Disorders
Alok Agrawal, MD, FASN, FNKF
Clinical Associate Professor
WSU, Dayton, Ohio
Slide2Arterial Blood Gas
ABG’s - necessary to correctly diagnose AB disorders
Interpret ABG s in conjunction with history, PE and labs
TCo2 in the chemistry panel - more accurate
pCO2 >55, primary respiratory acidosis always present
AG> 20, primary metabolic acidosis always present
Slide3AB Disorders- Definitions
Acidemia
: pH < 7.38
Alkalemia
: pH > 7.42
Acidosis
: pathologic process increasing H+
Alkalosis
: pathologic process decreasing H+
Mixed Disorders
: combination of 2 or more primary disorders
Compensation
: physiologic processes that cause pH to move towards normal due to buffering
Slide4STEP 1
Check pH
RespiratoryAcidosis
Metabolic Acidosis
Metabolic Alkalosis
Respiratory Alkalosis
< 7.40
> 7.40
Metabolic
Acidosis
Respiratory
Acidosis
Metabolic
Alkalosis
Respiratory
Alkalosis
STEP 2
Check pCO2
< 40
> 40
Metabolic
Acidosis
Respiratory
Acidosis
> 40
< 40
Metabolic
Alkalosis
Respiratory
Alkalosis
Slide5STEP 3
Choose Formula
MetabolicAcidosis
pCO2 = 1.5 (HCO3¯ ) + 8
± 2
Respiratory
Acidosis
For every
Ý
of 10 in pCO2:pH ¯ by 0.08 (Acute) 0.03 (Chronic)HCO3¯ by 1 mEq/l (Acute) 4 mEq/l (Chronic)
Metabolic
Alkalosis
pCO2 = 0.9 (HCO3¯ ) +16
Respiratory
Alkalosis
For every
ß
of 10 in pCO2:
pH
by 0.08 (Acute) 0.03 (Chronic)HCO3¯ ¯ by 2 mEq/l (Acute) 5 mEq/l (Chronic)
STEP 4
Identify other disorders
STEP 5
Check Anion Gap
STEP 6
Check Urine pH
STEP 7
Generate a differential
diagnosis
Slide6Normal pH
pCO2 < 36 , HCO3 < 21
mixed respiratory alkalosis and metabolic acidosis
pCO2> 44, HCO3> 27
mixed respiratory acidosis and metabolic alkalosis
pCO2 ~ 40, HC03~ 24 (with anion gap)
mixed metabolic acidosis and metabolic alkalosis
Slide7Simple metabolic acidosis
anion gap
Slide8Na 140
Cl 105
Cations
Anions
K 5
Ca 5
Mg 2
HCO3 25
PO4/SO4 2
Organic acids 4
Proteins 16
Proteins 16
These anions= 22
These cations =
12
Anion gap is
Unmeasured anions
Unmeasured cations
22 – 12 = 10
Anion gap is calculated
Na – (Cl + HcO3) or
140 – 130 = 10
Slide9Increased Anion gap acidosis
Methanol
Uremia
DKA
Paraldehyde ingestion, propylene glycol
Alcohol, Acetaminophen (pyroglutamic acid)
Lactic acidosis
Ethylene glycol
Salicylate , Starvation ketoacidosis
Slide10Causes of Low Anion Gap
Decreased Unmeasured Anion
hypoalbuminemia
Increased Unmeasured Cation
myeloma- IgG, light chains, marked hypercalcemia and hypermagnesemia
Pseudohyperchloremia
li intoxication, Bromism
Slide11Normal anion gap acidosis
Diarrhea
Ureteral diversion
RTA, Renal failure chronic- early
Hippurate (toulene), Hyperalimentation (AA, sulfur)
Acetazolamide, ammonium chloride, topiramate
Miscellaneous - pancreatic fistula, post hypocapnia,
- dilutional (IVF)
Slide12Acquired Distal RTA
Auto-immune disorders
Sjogrens, PBC
Hypercalciuria and Nephrocalcinosis
Hyperpara, hypervitaminosis D
Drugs
Ampho B, ifosfomide, lead, li, tetracycline, toulene
TI Diseases
Slide13Osmolal Gap
Measured Osm- Calculated Osm
ethylene glycol
methanol
propylene glycol
isopropranolol
Slide14Lactic Acidosis
Type A -Shock - Acute severe hypoxia - Acute severe anemia
Type B
- Metformin
- Malignancy
- Thiamine deficiency
- Cyanide
- NRTI
- Zyvox
Slide15Delta AG- Delta HCO3 Ratio
Ratio 1-2
: High anion gap acidosis
Ratio > 2
: HAG acidosis and metabolic alkalosis
Ratio < 1
: HAG acidosis and NAG acidosis
: DKA with ketone excretion
: CKD with anion excretion but H+
retention
Slide16Simple metabolic alkalosis
Slide17Saline responsive metabolic alkalosis
Diuretics
Adenoma
Miscellaneous- IV penicillin, Barter’s syndrome
Posthypercapnia
Emesis
NG suction
Slide18Saline unresponsive metabolic alkalosis
Licorice ingestion
Exogenous steroids
Alkali ingestion with low GFR
Cushing syndrome
Hyperaldosteronism
Slide19Slide20THANK YOU
Slide21Case 4a
72 yr old female with brain tumor has MS changes. Comatose with Kussmaul’s respirations. CT- IC hemorrhage with midline shifts
130/4.0/103/20
7.56/20/20
pH: 7.0
Slide22Simple acute respiratory alkalosis
Slide23Case 4b
Same patient after 2 days with same breathing pattern
136/4.5/110/14
7.46/21/15
pH : 6.5
Slide24Simple chronic respiratory alkalosis (fully compensated)
Slide25Case 4c
What if history was not known?
136/3.9/109/15
7.47/21/15
pH 6.0
Slide26Case 4c
simple chronic respiratory alkalosis
mixed acute respiratory alkalosis and metabolic acidosis
Slide27Case 4d
ABG done 12 hours after 4a and before 4b
7.52/21/17
Slide28Respiratory alkalosis in which
compensation not complete
Slide29Case 5
20 yr old male in ER - bottle of pills
140/3.5/104/8/18/1.0/90
7.35/15/8
pH: 5.0
Slide30Mixed elevated gap metabolic acidosis and respiratory alkalosis
Slide31Case 6a
57 year old with history of smoking has DOE
143/4.0/105/27
7.37/50/25
pH 5.0
Slide32simple chronic respiratory acidosis
Slide33Case 6b
One month later with respiratory distress. Has wheeze with respiratory rate of 33
142/3.9/100/33
7.29/61/33
pH : 5.0
Slide34Mixed acute on chronic respiratory acidosis
Slide35Case 7
45 year old diabetic patient with obtundation
140/5.5/97/20/20/1.1
7.01/80/20
pH : 5.0
Slide36Mixed acute respiratory acidosis elevated gap metabolic acidosis and metabolic alkalosis
Slide37Case 8
78 yr old NH pt. with vomiting for several days and fever, increasing SOB for few hours. RR is 35/mt . RLL consolidation.
138/4.2/97/28
7.69/20/26
pH:8.0
Slide38Mixed acute respiratory alkalosis and metabolic alkalosis
Slide39Case 9
20 yr old diabetic with nausea, vomiting for several days and now with fever and SOB over 8 hours
148/4.0/95/24/ 26/1.2/610
7.59/26/24
pH : 8.0, ketones
Slide40Respiratory alkalosis, metabolic alkalosis and elevated gap metabolic acidosis
Slide41Case 10
47 yr old alcoholic presents with vomiting after binge drinking for past 2 days. Swallowed large no. of diazepam pills 1 hour prior and is lethargic. RR- 8/mt and is unresponsive
136/4.4/85/29/21/1.0
7.27/62/29
pH: 5.0
Slide42Respiratory acidosis, elevated gap acidosis and metabolic alkalosis
Slide43Case 11
65 with COPD, CHF has increasing SOB,wheezing for 4 hrs. Currently on furosemide.
140/3.8/90/37/20/1.1
7.40/60/37
pH: 5.0
Slide44Mixed acute on chronic respiratory acidosis and a metabolic alkalosis
Slide45Case 12
27 yr old diabetic with SOB for 1 hour. Nausea, increased urination for 2 days. did not take insulin for 2 days. Hypercoagulable state diagnosed in hospital
136/3.6/102/12/10/1.1/700
7.40/20/13
pH: 5.0, ketones +
Slide46Mixed elevated gap metabolic acidosis and respiratory alkalosis
Slide47