Show Menu

ABG Cheat Sheet (DRAFT) by

aCNP CheatSheet

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Respir­atory System (Acid) CO2 is a volatile acid

•The respir­atory system can effect a change in 15-30 minutes
Decrease your respir­atory rate (hypov­ent­ila­tion) you retain CO2 (acid) therefore increasing your CO2 (acid)
Increased respir­atory rate (hyper­ven­til­ation) "blow off" CO2 (acid) therefore decreasing CO2 acid

The Renal System (Base)

Renal System (Base)
• Kidneys rid the body of the nonvol­atile acids H+ (hydrogen ions) and maintain a constant bicarb (HCO3).
• Bicarb­onate is the body’s base
Kidneys try to adjust for this by excreting H+ and retaining HCO3- base.
Respir­atory System will try to compensate by increasing ventil­ation to blow off CO2 (acid) and therefore decrease the Acidosis.
• Have excess H+ and decreased HCO3- causing a decrease in pH.
H+ decreases and you have excess (or increased) HCO3- base.
• The kidneys excrete HCO3- (base) and retain H+ to compensate.
• The respir­atory system tries to compen­sates with hypove­nti­lation to retain CO2 (acid) to decrease the alkalosis
• The renal system takes several hours to days to have an effect.

The Land of the ABG

The Last Name
• First, look at her pH (normal is 7.35 - 7.45)
• If her pH is < 7.35; her name is ACIDOSIS
• If her pH is > 7.45; her last name is ALKALOSIS
• NOTE: To have an absolutely perfect last name; her pH needs to be 7.40. So, keep in mind that if her pH is 7.35 - 7.39 she’s thinking about marrying into the ACIDOSIS family. If her pH is 7.41 - 7.45 she’s thinking about marrying into the ALKALOSIS family
The First Name
• Look at her pH again.
• If it is 7.35 - 7.45 (normal) then her first name is COMPEN­SATED.
• If the pH is < 7.35 or > 7.45 then her first name is UNCOMP­ENS­ATED.
The Middle Name
• First you need to look at the CO2 and HCO3-. Remember : normal CO2 35 - 45; and HCO3- 22 - 26. 1.
• The middle name will either be Respir­atory or Metabolic. 2.
• If the CO2 is < 35 or > 45 her middle name is RESPIR­ATORY. 3.
• If the HCO3- is < 22 or > 26; her middle name is METABOLIC.
The Family Feud
pH and HCO3- are "­kissin’ cousin­s" they like to go in the same direction
• CO2 is the "­black sheep" pH runs the opposite direction when it sees him Coming. THEREFORE:
• Decreased pH with decreased HCO3-: ACIDOSIS
• Increased pH with increased HCO3-: ALKALOSIS
Decreased pH with increased CO2-: ACIDOSIS
Increased pH with decreased CO2-: ALKALOSIS

Metabolic Acidosis

• pH < 7.35 (Normal: 7.35 - 7.45) HCO3- < 22 (normal: 22 – 26)
Increased H+, excess loss of HCO3-
• Overpr­odu­ction of organic acids (starv­ation, ketoac­idosis, increased catabo­lism)
• Impaired renal excretion of acid (renal failure)
• Abnormal loss of HCO3- (diarrhea, biliary fistula, Diamox)
• Ingestion of acid (salic­ylate overdose, oral anti-f­reeze)
Signs and Symptoms
• CNS depression (confusion to coma)
• Cardiac Dysrhy­thmias (elevated T wave, wide QRS to ventri­cular stands­till)
• Electr­olyte abnorm­alities (elevated K+, Cl-, Ca2+)
• Flushed skin (arter­iolar dilita­tion)
• Nausea
Treatment (treat the underlying cause)
• NaHCO3- (sodium bicarb­onate) based on ABGs only and with caution
• IV fluids and insulin for DKA
• Dialysis for renal failure
• Antibi­otics, increased nutrition for tissue catabolism
• Increased cardiac output and tissue perfusion for low CO states
• Rehydrate, monitor I and O
• Treat dysrhy­thmias, support hemody­namic and respir­atory status

Metabolic Alkalosis

• pH > 7.45 (Normal: 7.35 - 7.45) HCO3- > 26
• Loss of H+ or increased HCO3-
• Loss of K+ (diarrhea, vomiting)
• Ingestion of large amounts of bicarb­onate (antacids, resusc­ita­tion)
• Prolonged use of diuretics (distal tubule lose ability to reabsorb Na+ and Cl- therefore NaCl); Ammonia is in the urine and then binds with H+
Signs and Symptoms
• Similar to the disease process
• Diapho­resis
• Nausea and Vomiting
• Increase neurom­uscular excita­bility (Ca2+ binds with protein)
• Shallow breathing (respi­ratory compen­sation)
• EKG changes (increased QT, sinus tachyc­ardia)
• May also see confusion progre­ssing to lethargy to coma
• Electr­olyte abnorm­ality (decreased Ca2+), normal or decreased K+, increased base excess on the ABG
Treatment (treat the underlying cause)
• Replace potassium (KCl) losses in 0.9% NaCl (rehyd­rates and increases HCO3- excretion)
• Diamox (aceta­zol­amide, increases HCO3-e­xcr­etion)
• Monitor neuro status, re-orient, seizure precau­tion, monitor I and O


• pH < 7.35 (Normal: 7.35 - 7.45) CO2 > 45 (Normal: 35 – 45)
Hypove­nti­lation • Depression of the Respir­atory Center (sedat­ives, narcotics, drug overdose, CVA, cardiac arrest, MI).
• Respir­atory muscle paralysis (spinal cord injury, Guilli­an-­Barre, paraly­tics).
• Chest wall disorders (flail chest, pneumo­tho­rax).
• Disorders of the lung parenchyma (CHF, COPD, pneumonia, aspira­tion, ARDS).
• Alteration in the function of the abdominal system (diste­nsion)
Signs and Symptoms
•CNS depression (decreased LOC)
•Muscle twitching which can progress to convul­sions
•Dysrh­yth­mias, tachyc­ardia, diapho­resis (related to hypoxia secondary to hypove­nti­lation)
•Flushed skin
•Serum electr­olyte abnorm­alities including elevated K+ (potassium leaves the cell to replace the H+ buffers leaving the cell)
•Physi­cally stimulate the patient to improve ventil­ation
•Vigorous pulmonary toilet (chest PT, coughing and deep breathing, inspir­ometer, respir­atory treatments with bronch­odi­lators)
•Mecha­nical ventil­ation (to increase the respir­atory rate and tidal volume)
•Reversal of sedatives and narcotics
•Antib­iotics for infections
•Diuretics for fluid overload
•NOTE: beware of NaHCO3- sodium bicarb­ona­te—can compensate and cause metabolic alkalosis. Also, if patient has been hypoxic and this is a lactic acidosis; NaHCO3- can be dangerous)

Respir­atory Alkalosis

pH > 7.45 (Normal: 7.35 - 7.45) CO2 < 35 (Normal: 35 – 45)
Alveolar Hyperv­ent­ilation
•Psych­ogenic (fear, pain, anxiety)
•CNS stimul­ation (brain injury, ETOH, early salicylate poisoning, brain tumor)
•Hyper­met­abolic states (fever, thyrot­oxi­cosis)
Hypoxia (high altitude, pneumonia, heart failure, pulmonary embolism)
•Mecha­nical overve­nti­lation (ventilator rate too fast)
Signs and Symptoms
•Pares­thesias (numb fingers /toes, circum­oral, carpal pedal spasms and tetany)
•Tinnitus (ringing in the ears)
•Elect­rolyte abnorm­alities (decreased Ca+, K+)
Treatment (treat the underlying cause)
•Sedatives or analgesics
•Corre­ction of hypoxia (possible diuretics, mechanical ventil­ation to also decrease respir­atory rate and decrease the tidal volume)
•NOTE: patients with brain injury may need hyperv­ent­ilation
•Antip­yretics for fever
•Treat hypert­hyr­oidism
•Breathe into a paper bag for hyperv­ent­ilation