Summary of the Approach to ABGs<br />Check the pH<br />Check the pCO2<br />Select the appropriate compensation formula<br />Determine if compensation is appropriate<br />Check the anion gap <br />AG=NA – (HCO3 + CL):12±4<br />If the anion gap is elevated, check the delta-delta<br />G:G Ratio =Δ AG (12-AG) Δ HCO3 (24-HCO3)<br />If a metabolic acidosis is present, check urine pH<br />Generate a differential diagnosis<br />
EXPECTED CHANGES IN <br />ACID-BASE DISORDERS <br />From: THE ICU BOOK - 2nd Ed. (1998) [Corrected]<br />
Case: 1<br />An elderly woman from a nursing home was transferred to hospital because of profound weakness and areflexia. <br />Her oral intake had been poor for a few days. <br />Current medication was a sleeping tablet which was administered by nursing staff as needed.<br />
Comments<br />About 90% of cases of metabolic alkalosis are due to: <br />diuretic therapy <br />loss of gastric secretions (vomiting or nasogastric suction)<br />The urine chloride at 74mmol/l is <br /> very high in this patient<br /><ul><li>Chloride UN-responsive metabolic alkalosis.
What blood pressure ???</li></li></ul><li>CASE: 2<br />A 20 year old student presents with excessive vomiting after binge drinking.<br />ABG:<br /> pH= 7.50, <br />pCO2 =44, <br />pO2= 100<br />Metabolic panel:<br /> Na= 138,<br />Cl =100,<br /> HCO3= 30<br />
CASE: 3<br />46 year old man with progressive CKD on conservative management <br />(baseline BUN 40, Creat 4.0) <br />is admitted after episode of vomiting attributed to food poisoning.<br />He is orthostatic on exam and appears “dehydrated”<br />Nephrology called to dialyze<br />Renal fellow: Why’s his HCO3 so high?<br />Resident: High? It’s 25, and the pH is 7.40. Now come in and dialyze him!<br />
CRF>>>>>>>HIGH AG M.AC<br />VOMITING>>>>>>>METABOLIC ALKALOSIS<br />FROM tow above disorders<br />/ we can explanation why PH,HCO3 in normal limites?<br />Thereby we should calculate AG in all cases<br />
CASE:4<br />45 year old woman with long history of EtOH abuse comes into ED with 3 days of nausea and vomiting.<br />She lives on the streets and is very disgeveled appearing.<br />She stopped drinking 3 days ago because she felt sick<br />