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