Hartmanns solution

Hartmann Compound Sodium Lactate is what the bag reads.

Weirdly, MIMS lists this as a pregnancy category C substance, which demonstrates the usefulness of that ranking.

Hartmanns is still essentially normal saline, garnished with small amounts of calcium and potassium. The key difference is the sodium compound.

Of the 9 or so grams, 3.17g is contributed by sodium lactate, a slightly salty-tasting substance which Wikipedia introduces as a meat preservative.

No, you shouldn’t expect this lactate to contribute to lactic acidosis. There is no H+ ion. That spot is taken by the sodium ion. The lactate also will not buffer any additional hydrogen ions (it can, but only at a pH of 4.0).

Contents of Hartmanns compound sodium lactate

The concept of replacing sodium lactate instead of sodium chloride is sound, because what you really want to replace is sodium.

Sodium will hang around in the extracellular fluid and its presence there will fatten up your intravascular volume. The excess chloride in contrast is worse than useless. So, one can give the sodium complexed with lactate instead. The lactate is in equilibrium with pyruvate; its metabolic fate is to be incorporated into the citric acid cycle, consuming a hydrogen ion and thus decreasing total body acidity (as the other metabolic byproduct is carbon dioxide, which escapes into the atmosphere)

The short term effect therefore is the same as giving normal saline; but the long term effect is alkalinizing.

Yes, the metabolism of lactate is "nutrition", of a sort.
One litre of Hartmanns will provide you with 9 calories, roughly equivalent to 200g of raw bok choy.
Yum.

References

From MIMS online, via CIAP; using Baxter Full PI data sheets. Those PI documents are word for word what you will find on the bags.  Additionally, the anaesthesiauk website has this page, with a summary of the relevant details. To find out more about the pH of intravenous solutions, you could pay JAMA for this article.