Tag Archives: abg

Hi Mr PaCO2. | Resp acid: Hi CO2, resp alk Low CO2. (hi paco2 lo, lo ph hi, lo bicarb hi)

Resp acidosis: COPD
Raised CO2 and acid = Lack of ventilation = RESP ACIDOSIS. COPD/asthma. Status. MG.

Met acidosis:
DKA ==> Metabolic acidosis. Low bicarb and acid. if Low CO2 –> resp compensation.
Raised AG: Lactate, Ketoacidosis, Ureamia from renal failure, poisoning e.g. salicycates or anti-freeze.
No increase in AG – lost bicarb and raised Cl e.g. RTA or severe diarrhoea.

Respiratory alkalosis –> Low Co2 and high PH –> Hyperventiliation (which causes low serum Ca.)
Resp alkalosis: PE, Pneumonia, anaemia, high altitude hypoxia, meningitis, anxiety. Early asp overdose = resp alkalosis with hyperventilation.

Met alk: VOM! (Co2 tends not to correct this.)
Vom. Diuretics (low K+ –> met alk; cf resp alk –> low Ca). Conn’s.

Resp acid = raised CO2. Resp alk = low Co2.

Resp acidosis (hi Co2):
a) Lungs COPD/CF/Pulm oedema. b) Opiates. c) MS/Guillian-barre.
Treat with NIPPV/IPPV/Naloxone etc.

Metabolic acid (lo bicarb):
RF/DKA/Lactate/DIARRHOEA. (Ergo, compensate via resp alk).

Resp alk (lo Co2):
Hyperventilation (PE, acute aspirin!), Hypoxia. Head injury. Tx: O2.

Met alk (hi bicarb):
Vomiting of protons/GI fistula – loss of protons. Diuretics causes metabolic alkalosis as does vomiting, while diarrhoea causes metabolic acidosis.
Met alk: Compensate badly by BRADYPNEOA – low RR.

-3 BE = acid! +3 BE = alk. Alkalosis give rise to Spasm/low K+.
If PCO2 abnormal = resp issue; if bicarb abnormal = met issue.
Compensation: patient’s cannot over-compensate. FiO2 of 0.4 if on 40% venturi.


Hi PaCo2 Lo (Hi-Lo’s smoking bar) 6 to 4.5
Lo Bicarb Hi 22-26
Lo pH Hi 7.35-7.45

If on same side: cause. If other side: compensation.

ABG – Hi CO2 = Acidosis. Lo CO2 = Alkalosis i.e. co2 is like anti-bicarb.

Site, Size, Shape, Surface, Skin, Scar. Tenderness, Temperature, Transillumination. 
ROME – Resp opp, Metabolic equal. Direction of pH and CO2/HCO3.
Big spleen = Malaria/cMl/Myelofibrosis.

High Anion Gap: KUSSMAL

– dKA
– Uraemia
– Salicylates
– Sepsis
– Methanol
– Alcoholic ketoacidosis
– Lactate.



C – CO/HCN; A – Alcoholic ketoacidosis; T – Toluene


Etyhlene glycol

Normal anion gap – USED CARB – i.e. used up bicarb. RTA/DIARRHOEA/FISTULA!


U = Ureteroenterostomy
S = Small bowel fistula
E = Extra chloride
D = Diarrhea

C = Carbonic anhydrase inhibitors
A = Adrenal insufficiency/Acetazolamide/Addison’s
R = Renal tubular acidosis
P = Pancreatic fistula

Lots of saline can cause hyperchloremic metabolic acidosis with normal anion gap

Not sure about this:

Respiratory if pH is up and Paco2 is down or if pH down and Paco2 is up
Metabolic if pH and HCO3 are both up or if pH and HCO3 are both down
Compensating if Paco2 and HCO3 both up or if pH and Hco3 both are down
Mixed if Paco2 up and HCO3down or if Paco2 down and HCO3 is up