 The Components  pH / PaCO 2 / PaO 2 / HCO 3 / O 2 sat / BE  Desired Ranges  pH  PaCO mmHg  PaO mmHg  HCO  O 2 sat %  Base Excess - +/-2 mEq/L

 Aids in establishing a diagnosis  Helps guide treatment plan  Aids in ventilator management  Improvement in acid/base management allows for optimal function of medications  Acid/base status may alter electrolyte levels critical to patient status/care

 When to order an arterial line --  Need for continuous BP monitoring  Need for multiple ABGs  Where to place -- the options  Radial  Femoral  Brachial  Dorsalis Pedis  Axillary

 The body produces acids daily  15,000 mmol CO 2  mEq Nonvolatile acids  The lungs and kidneys attempt to maintain balance

 Assessment of status via bicarbonate-carbon dioxide buffer system  CO 2 + H 2 O H 2 CO 3 HCO H +  ph = log ([HCO 3 ] / [0.03 x PCO 2 ])

 ACIDS  Acidemia  Acidosis Respiratory  CO 2 Metabolic  HCO 3  BASES  Alkalemia  Alkalosis Respiratory  CO 2 Metabolic  HCO 3

  ph,  CO 2,  Ventilation  Causes  CNS depression  Pleural disease  COPD/ARDS  Musculoskeletal disorders  Compensation for metabolic alkalosis

 Acute vs Chronic  Acute - little kidney involvement. Buffering via titration via Hb for example pH  by 0.08 for 10mmHg  in CO 2  Chronic - Renal compensation via synthesis and retention of HCO 3 (  Cl to balance charges  hypochloremia) pH  by 0.03 for 10mmHg  in CO 2

  pH,  CO 2,  Ventilation   CO 2   HCO 3 (  Cl to balance charges  hyperchloremia)  Causes  Intracerebral hemorrhage  Salicylate and Progesterone drug usage  Anxiety   lung compliance  Cirrhosis of the liver  Sepsis

 Acute vs. Chronic  Acute -  HCO 3 by 2 mEq/L for every 10mmHg  in PCO 2  Chronic - Ratio increases to 4 mEq/L of HCO 3 for every 10mmHg  in PCO 2  Decreased bicarb reabsorption and decreased ammonium excretion to normalize pH

  pH,  HCO 3  hours for complete activation of respiratory compensation   PCO 2 by 1.2mmHg for every 1 mEq/L  HCO 3  The degree of compensation is assessed via the Winter’s Formula  PCO 2 = 1.5(HCO 3 ) +8  2

 Metabolic Gap Acidosis  M - Methanol  U - Uremia  D - DKA  P - Paraldehyde  I - INH  L - Lactic Acidosis  E - Ehylene Glycol  S - Salicylate  Non Gap Metabolic Acidosis  Hyperalimentation  Acetazolamide  RTA (Calculate urine anion gap)  Diarrhea  Pancreatic Fistula

  pH,  HCO 3   PCO 2 by 0.7 for every 1mEq/L  in HCO 3  Causes  Vomiting  Diuretics  Chronic diarrhea  Hypokalemia  Renal Failure

 Patients may have two or more acid-base disorders at one time  Delta Gap Delta HCO 3 = HCO 3 + Change in anion gap >24 = metabolic alkalosis

 Start with the pH  Note the PCO 2  Calculate anion gap  Determine compensation

 An ill-appearing alcoholic male presents with nausea and vomiting.  ABG / 41 / 85 / 22  Na- 137 / K- 3.8 / Cl- 90 / HCO

 Anion Gap = ( ) = 25  anion gap metabolic acidosis  Winters Formula = 1.5(22) + 8  2 = 39  2  compensated  Delta Gap = = = 37  metabolic alkalosis

 22 year old female presents for attempted overdose. She has taken an unknown amount of Midol containing aspirin, cinnamedrine, and caffeine. On exam she is experiencing respiratory distress.

 ABG / 19 / 123 / 14  Na- 145 / K- 3.6 / Cl- 109 / HCO  ASA level mg/dL

 Anion Gap = ( ) = 19  anion gap metabolic acidosis  Winters Formula = 1.5 (17) + 8  2 = 34  2  uncompensated  Delta Gap = = = 26  no metabolic alkalosis

 47 year old male experienced crush injury at construction site.  ABG / 32 / 96 / 15  Na- 135 / K-5 / Cl- 98 / HCO / BUN- 38 / Cr- 1.7  CK- 42, 346

 Anion Gap = ( ) = 22  anion gap metabolic acidosis  Winters Formula = 1.5 (15) + 8  2 = 30  2  compensated  Delta Gap = = = 27  mild metabolic alkalosis

 1 month old male presents with projectile emesis x 2 days.  ABG / 40 / 98 / 30  Na- 140 / K- 2.9 / Cl- 92 / HCO

 Metabolic Alkalosis, hypochloremic  Winters Formula = 1.5 (30) + 8  2 = 53  2  uncompensated