What causes lactic acidosis and life threatening bp drop for 6hours. icu 2 days. unknown infection. blood culture neg. wbc 16 now 13 1wk later?

Lactic acidosis/ BP: Lactic acidosis + BP drop = sepsis or SIRS- systemic inflammatory response . Pain? Age? May be infection-bacteria, aerobic or anerobic, Check urine, CXR , CT for gallbladder, diverticulitis, appendicitis, abscess, pancreatitis, check for autoimmune process- allergic reaction, ischemia, thiamine def , alcohol, DM, meds: metformin, ASA, methanol, ethylene glycol, retroviral, INH, CO. F/u/ w/ doc