A child presents with diarrhea and peripheral circulatory failure. The arterial pH is 7, pCO2 15 & pO2 76. Most appropriate:

a. Soda bicarb infusion.

b. Bolus of Ringer Lactate.

c. Bolus of HES.

d. 5% dextrose soln.

Calculate plasma osmolality:

Na-125, Glu- 108, BUN- 140

a. 300

b. 306

c. 312

d. 318

Normal anion gap- FUSED CARS

In patients with a normal anion gap the drop in HCO₃⁻ is compensated for almost completely by an increase in Cl⁻ and hence is also known as hyperchloremic acidosis.

The HCO₃⁻ lost is replaced by a chloride anion, and thus there is a normal anion gap.

FUSED CARS 


Fistula (pancreatic)
Uretogastric conduits
Saline administration
Endocrine (hyperparathyroidism)
Diarrhea


Carbonic anhydrase inhibitors (acetazolamide)
Ammonium chloride
Renal tubular acidosis
Spironolactone

High anion gap Acidosis

A CAT PILES MUD:

Alcohol abuse

Carbon monoxide or Cyanide
Aspirin
Toluene

Paraldehyde/ Polyethylene glycol
Iron/ Isoniazid
Lactic acidosis
Ethylene glycol
Starvation

Methanol
Uremia
Diabetic ketoacidosis.

Anion Gap

The anion gap is the difference in the measured cations and the measured anions in serum, plasma, or urine.

It is calculated by subtracting the serum concentrations of chloride and bicarbonate(anions) from the concentrations of sodium plus potassium (cations):

= ( [Na⁺] + [K⁺] ) − ( [Cl⁻] + [HCO₃⁻] )

The average anion gap for healthy adults is  8 -12 mEq/L.

Plasma osmolality

Normal human reference range of osmolality in plasma is about 275-299 milli-osmoles per kilogram.

To calculate plasma osmolarity use the following equation :

• = 2 x Na⁺ + Glucose +  BUN 
                                   18            2.8
  
  where [Glucose] and [BUN] are measured in mg/dL.

Simplifications are sometimes used:

• = 2[Na⁺] + [Glucose]/20 + BUN/3 - 2