CREATE TABLE table_22591 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT)

What is the production code for episode 'surgery'?
SELECT "Production code" FROM table_22591 WHERE "Title" = 'Surgery'
SELECT "Production code" FROM "table_22591" WHERE "Title" = 'Surgery'