Mendoza, Donn Paulo; Mendoza, Gracielle; Mendoza, Trisha; Mindanao, Malvin Ace, Miranda, Maria Carmela; Molina, Ramon Miguel; Monzon, Jerry West; Morales, Arriane; Musni, Merwen Mitchel; Nallas, Anna Pauline; Naval Ayne Rangel C7 HISTORY 45 y/o, female Diabetic 4 days of acute illness Fever (39.5 C) Chills, myalgia Diarrhea Denied taking any medications, drugs nor alcohol Physical Examination Vital Signs BP 84/52 (supine) PR 118 bpm RR 42 bpm Mucous membranes- dry Neck veins- flat No edema Abdomen- distended, firm, mildly tender Hyperactive bowel sounds Blood Indices Hgb 15.5 g/dL Hct 48% WBC count 22,800 Segmented neutrophils 66% Bands 23% LABORATORY RESULTS Serum Na meq/L Serum K 4.2 meq/L Serum Cl meq/L HCO3 10.0 meq/L BUN 28.0 mg/dL Serum Creatinine 2.4 mg/dL Glucose mg/dL Ketones none Lactate 3.0 meq/L pH 7.39 pCO2 17.0 mmHg Arterial blood sample pH < 7.40 HCO3 < 24 Metabolic acidosis pCO2 < 40 pCO2 > 40 Respiratory acidosis HCO3 > 24 pH > 7.40 HCO3 >24 Metabolic alkalosis pCO2 > 40 pCO2 < 40 Respiratory alkalosis HCO3 < 24 Acid-base disturbance Metabolic Acidosis Compensated pH 7.39 (normal) HCO3 10.0 meq/L pCO2 17.0 mmHg Lactate 3.0 meq/L Steps in acid base diagnosis Obtain arterial blood gas (ABG) and electrolytes simultaneously Compare [HCO 3 - ] on ABG and electrolytes to verify accuracy Calculate anion gap (AG) Know four causes of high-AG acidosis ketoacidosis lactic acid acidosis renal failure toxins Steps in acid base diagnosis Know two causes of hyperchloremic or nongap acidosis bicarbonate loss from GI tract renal tubular acidosis Estimate compensatory response Compare AG and HCO 3 - Compare change in [Cl - ] with change in [Na + ] Rule of Thumb: Metabolic acidosis PaCO 2 = (1.5x HCO 3 - ) + 8 or PaCO 2 will 1.25 mmHg per mmol/L in HCO 3 - or PaCO 2 = HCO Rule of Thumb Metabolic alkalosis PaCO 2 will 0.75 mmHg per mmol/L in HCO 3 - or PaCO 2 will 6 mmHg per 10 mmol/L in HCO 3 - or PaCO 2 = HCO Rule of Thumb Respiratory alkalosis Acute: HCO 3 - will 2 mmol/L per 10 mmHg in PaCO 2 Chronic: HCO 3 - will 4 mmol/L per 10 mmHg in PaCO 2 Rule of Thumb Respiratory Acidosis Acute: HCO 3 - will 1 mmol/L per 10 mmHg in PaCO 2 Chronic: HCO 3 - will 4 mmol/L per 10 mmHg in PaCO 2 Pattern of Compensatory Changes DisorderpHHCO3PaCO2 Metabolic Acidosis Low Metabolic Alkalosis High Respirator y Alkalosis HighLow Respirator y acidosis LowHigh Anion Gap represents the concentration of all the unmeasured anions in the plasma concentrations are expressed in units of milliequivalents/liter (mEq/L) NV: 8-16 mEq/L Major Clinical Uses of the Anion Gap To signal the presence of a metabolic acidosis and confirm other findings Help differentiate between causes of a metabolic acidosis: high anion gap versus normal anion gap metabolic acidosis. To assist in assessing the biochemical severity of the acidosis and follow the response to treatment Anion Gap Key Fact: Hypoalbuminaemia causes a low anion gap Albumin is the major unmeasured anion and contributes almost the whole of the value of the anion gap. Every one gram decrease in albumin will decrease anion gap by 2.5 to 3 mmoles. A normally high anion gap acidosis in a patient with hypoalbuminaemia may appear as a normal anion gap acidosis. This is particularly relevant in Intensive Care patients where lower albumin levels are common. A lactic acidosis in a hypoalbuminaemic ICU patient will commonly be associated with a normal anion gap. Anion Gap With potassium = ( [Na + ]+[K + ] ) ( [Cl ]+[HCO 3 ] ) = ( ) (108+10) = 24.2 mEq/L - HIGH Without potassium = ( [Na + ] ) ( [Cl ]+[HCO 3 ] ) = (138) (108+10) = 20.0 mEq/L - HIGH Anion Gap Sodium - (chloride + bicarbonate) High Anion Gap Acid retention Examples: Lactic Acidosis: most common Ketoacidosis Advanced Renal Failure Drug and Toxin Induced Normal Anion Gap Hyperchloremic acidosis GI or renal Loss of bicarbonate Impaired renal acid secretion Reabsorption of Chloride Examples: Diarrhea Renal Tubular Acidosis Carbonic Anhydrase Inhibition HIGH ANION GAP Lactic Acidosis Increase in plasma lactate Secondary to poor tissue perfusion (Type A) Aerobic disorders (Type B) Ketoacidosis Increase fatty acid metabolism Accumulation of ketoacids (Acetoacetate & - hydroxybutyrate) Diabetic ketoacidosis, alcoholic ketoacidosis HIGH ANION GAP Drug and toxin induced Salicylates: ketones, lactate, salicylate ethylene glycol: glycolate, oxalate Methanol or formaldehyde: Formate Advanced Renal failure: Sulfate, phosphate, urate HIGH ANION GAP Advanced RF # of functioning nephrons Dec. NH4+ prod. and excretion Failure to balance w/ net acid production Inc. anion gap DIARRHEA loss of HCO3 along w/ vol. depletion Metabolic acidosis and hypokalemia renal synthesis and excretion of NH4 NORMAL ANION GAP RENAL TUBULAR ACIDOSIS (GFR bet. 20 and 50 mL/min) # of functioning nephrons Proximal RTA: HCO3 tubular reabsorption OR Distal RTA: acid excretion renal synthesis and excretion of NH4 OTHER CAUSES OF NORMAL ANION GAP Carbonic anhydrase inhibition Drug-induced hyperkalemia (With renal insufficiency) Treatment Depends primarily on the cause Need to control diabetes with insulin High Anion Gap Acidosis Treatment Diabetic Ketoacidosis Fluid resuscitation with isotonic saline IV regular insulin High Anion Gap Acidosis Treatment Lactic Acidosis Alkali therapy acute acidemia to improve cardiac function and lactate utilization Infuse sufficient NaHCO3 to raise arterial pH to no more than 7.2 over minutes Treatment Metabolic acidosis may also be treated directly If the acidosis is mild - administration of intravenous fluids may be all that is needed If the acidosis is very severe - bicarbonate may be given intravenously However, bicarbonate provides only temporary relief and may cause harm Treatment Potential Complications of Bicarbonate Therapy o Volume overload o Hypokalemia o CNS acidosis o Hypercapnia o Tissue hypoxia Continuous monitoring of pH and electrolytes