Run-StoredProcedureWithOutVar.ps1

# CREATE PROCEDURE DemoSp
# 	-- Add the parameters for the stored procedure here
# 	@in int, 
# 	@out int out
# AS
# BEGIN
# 	SET NOCOUNT ON;
# 	select @out = @in * 2;
#     SELECT @in, @out

# END

function Run-StoredProcedureWithOutVar($inValue) {
    $statement = @"
DECLARE @outVar bigint;
EXEC a_db1.dbo.[DemoSp] @in = '${inValue}'
    , @out = @outVar output;
SELECT @outVar as arbitraryOutVar
"@
    $params = @{
        Query = $statement -f $inValue
    }
    $results = Invoke-Sqlcmd -Serv localhost -U sa -P TheDemo @params -Verbose
    write-Host "In value: [$inValue]; Out value: [$($results.arbitraryOutVar)]"
}

Run-StoredProcedureWithOutVar 33