Post on 30-Dec-2015
description
ABG INTERPRETATIONABG INTERPRETATION
By: Dr. Ashraf Al Tayar, By: Dr. Ashraf Al Tayar, MD,MRCP(I), MD,MRCP(I),
Assistant Consultant Critical Care, Assistant Consultant Critical Care, KKNGH.KKNGH.
ABG Interpretation: Comprises 4 steps.ABG Interpretation: Comprises 4 steps.
• Determine the process• Determine the primary disorder• Sharpen the diagnosis• Determine compensation
I. Step 1:
Use pH to determine
Acidosis - < 7.35
Alkalosis - > 7.45
II. Determine metabolic vs. Respiratory Metabolic disorders: - pH changes in same direction as PCO2 and HCO3
- Metabolic acidosis pH PCO2 HCO3
- Metabolic alkalosis pH PCO2 HCO3
Respiratory disorders:
- pH change in opposite direction of
HCO3 and PCO2
- Respiratory acidosis
pH
PCO2
HCO3
- Respiratory alkalosis
pH
PCO2
HCO3
- Calculate the AG
- Calculate Osm. Gap
- Calculate Urinary AG
Sharpen the DiagnosisSharpen the Diagnosis
AG:
Na – ( CL + HCO3)
normal 10 (+/-) 2
• AG:
- Paraproteinaemia
- Hyperchloraemia
- Hypoalbumenaemia
( AG 2.5 / 1 gm /dL in albumin)
- Hypermagnesaemia
- Hyponatraemia
AG : Metabolic acidosis (DD) (MUDPILERS)
Methanol
Uremia
DKA
Paraldehyde
Isopropyl alcohol – Isoniazide
Lactic acid
Ethylene glycol
Rhabdomyolosis
Salycylate
Normal AG Metabolic acidosis (Hyperchloremia)Normal AG Metabolic acidosis (Hyperchloremia)
A. Hypokalemia- Diarrhea- Urethral diversion- RTA- Mineralocorticorticoid deficiency- CAI: Acetazolamide
B. Hyperkalemia- Renal failure (Early)- Renal disease: SLE
Amylodosis Sickle cell
- Sulphur toxicity
Urine AG
- < - 10
extra renal causes
- > + 10
Renal causes
Osmolal Gap- measured serum osm. – calc. osm.
normal (10 – 15)OG DD:( MEDIE )MethanolEthylene glycolDiuretic : MannitolIsoprophyl alcoholEthanol
Determine CompensationDetermine Compensation
Metabolic acidosis
PCO2 = 40 + BE
Metabolic alkalosis
PCO2 = 40 + 0.6 X BE
Respiratory acidosis
Acute :HCO3 = PCO2 – 40 / 10 + 24
Chronic : HCO3 = PCO2 – 40 / 3 + 24
Respiratory alkalosis:Acute : 40 – PCO2 / 5 + 24
Chronic: 40 – PCO2 / 2 + 24
Example 1:
pH: 7.07
PCO2: 28
HCO3: 8
SBE: - 20
Example 2:
pH : 7.33
PCO2 : 20
HCO3 : 12
BE : 12
Example 3
pH : 7.48
PCO2 : 28
HCO3: 22
BE : 2
Effects of Acid base changeEffects of Acid base change Acidosis alkalosis
CVS Inotropy Inotropy Conduction- defect Altered coronary flow Arterial VD Digoxin toxicity Venous VD
Oxygen Delivery O2 Hb binding Affinity 2, 3 DPG 2, 3 DPG
Neuromuscular Resp. dep NM excitability Sensorium Encephalopathy Seizures
Resp. depElectrolytes Hyper K+ Hypo K+
Hyper Ca+ Hypo Ca+ Hyperuricaemia Hypophosphatemia
THANK YOU