Isotonic bicarb is useful when you are trying to fluid resuscitate a patient with a severe normal anion gap metabolic acidosis. This is especially true in rhabdomyolysis where alkalinisation of the urine prevents ferrihemate and myoglobin precipitation and cast formation. 1.35% NaHCO3 is isotonic.
The total volume will be 1000 mls and contain 13.44 g of NaHCO3 i.e. 1.35%. This solution is not shelf stable in a plastic fluid bag and should be used within 12 hours.