> There are tens of thousands of procedure and drug codes (things that are done or given) and tens of thousands of diagnostic codes (reasons justifying the procedure), creating a space well into the quadrillions of possible routine combinations.

10^5 * 10^5 = 10^10 which is tens of billions, not quadrillions

That said, a combinatorial space can be simply represented as a tuple of two columns (10^5, 10^5) instead of having to map every possible (including nonsensical) permutation.

Increase for three or four dimensions.