An 8 month female baby presented with 1 day h/o lethargy. She had vomited several times. Her drug addict mother said she appeared "intoxicated".O/E: baby was obtunded but she was easily arousable and muscle tone was normal. RR = 60/min. Pupils are normal. BP was 112/62.Ix: Na+= 135 K+ = 4.2 ,Glucose 5.9 mmol/l , Cl- = 116 ,Urinalysis: pH = 5.0; negative for glucose & ketones, positive for calcium oxalate crystals. ABG: pH = 7.19, pCO2 = 20, PO2 = 100 , HCO3 = 6.2 ?

Impoant points in history: * Drug addict mother * Tachypnea * Pupils normal - no CNS depression by opioids * Calcium oxalate crystal - d/t ethylene glycol poisoning Ethylene glycol poisoning - leads to - acute tubular necrosis ABG: pH = 7.19, pCO2 = 20, PO2 = 100 , HCO3 = 6.2 Calculation: Anion gap: Na - (Cl- + HCO3) = 135-(116+6) = 135-122 = 13 pH is 7.19 acidic.(normal pH 7.35-7.45) pCO2 is 16( low )that cannot explain acidotic PH (normal pco2 40) HCO3 is 6.2 which is low that explain low pH. therefore acidic pH is metabolic problem.i.e.metabolic acidosis in this CASE compensation is going on which is hyperventilation leading to CO2 washout.low PCo2 since is PH is not normalised so paial compensation From ABG: metabolic acidosis paially compensated. expected PCO2 =15+HCO3=15+6=21 actual PCO2 is almost equal to expected value this implies compensation is going fine.