Need to split in form of key & value

[ZERO_COOL]

I am getting event as below.
"rusage" => [
[0] "",
[1] "[mem=10000,mem=5000,VCS-BASE-RUNTIME=1]"
],

I want the value of mem as res_mem higher one among two keys with "mem" as new field.

output:
{
res_mem = 10000
}