Arterial Blood Gas

Acid Base Balance

Anion gap = Na - (HCO3- + Cl-) + (4-albumin) * 2.5

low albumin means more H+ is ionized and anion gap is actually larger

Low albumin means calcium is not bound

More acidic means more ionized calcium

More alkalotic means less ionized calcium - > tetany

<0.4 Hyperchloremic Anion gap metabolic Acidosis

0.4 - 0.8 High anion gap metabolic acidosis and non anion gap metabolic acidosis

1-2 uncomplicated high anion gap metabolic acidosis

>2 metabolic acidosis with preexisting elevated HCO3 (metabolic alkalosis or respiratory acidosis)

https://www.youtube.com/watch?v=9u7bUhKkeUI

Correcting for albumin is not helpful:

https://emcrit.org/pulmcrit/mythbusting-correcting-the-anion-gap-for-albumin-is-not-helpful/

ethylene glycol, propylene glycol has osmolar gap > 10

compensating for AGMA? 

Winter's formula PCO2 = 1.5 * HCO3 + 8 +/- 2

PCO2 30 - 34

AGMA + respiratory acidosis or not

https://www.mdcalc.com/calc/91/serum-osmolality-osmolarity

delta delta is there an additional acid base disturbance on top of anion gap metabolic acidosis. calculate is there anion gap metabolic acidosis

delta-delta = AGMA + NAGMA + metabolic alkalosis??

1 2 3 4 5 Rule

Simple table to calculate metabolic compensation in respiratory acidosis and alkalosis (aka the 1-2-3-4-5 rule)

• Respiratory Acidosis: Increased PaCO2. For every 10mmHg rise should have INCREASE in HCO3 by 1 (acute) or 4 (chronic) as compensation
• Respiratory Alkalosis: Decreased PaCO2. For every 10mmHg rise should have DECREASE in HCO3 by 2 (acute) or 5 (chronic) as compensation,
• 
  

https://litfl.com/acid-base-disorders/

Alveolar - Arterial gradient

normal = age /4 + 4

PAO2 = FiO2 * (760-47) - PaCo2/0.8

PaO2 arterial via blood gas

PF ratio

Taco, paco, peco, paco

Dead space = Tidal volme * (PaCo2 - PECO2) / (PaCo2)

normal Tidal volume 500

Normal Dead space 150

Ve = Vt * RR

Va = (Vt - Vd) * RR

How to perform

ABG syringe, for an adult, use a 20-gauge, 2.5-inch needle for a femoral sample and a 22 gauge, 1.25-inch needle for a radial artery puncture, Also 23 gauge and 25 gauge needle can be used. A 23 gauge syringe may be used as it allows faster filling than 25 gauge one, but does not affect more pain to the patient 

Converting between ABG and VBG