You are scheduled to anesthetize a 67-yr-old woman for a lower abdominal resection of a rectal cancer. She has a history of coronary artery disease, hypertension, obesity, and insulin-dependent diabetes mellitus. A previous anesthetic 6 mo before for a laparoscopic cholecystectomy was, according to the patient, uneventful. You have no previous anesthetic record to refer to. She proves to be a difficult IV stick, but you manage to put a 20-gauge IV in her hand. You sedate her and take her to the operating room. Prior to induction of anesthesia, you place an arterial line in the patient’s right radial artery. This is connected to a pressure transducer containing 1,000 U heparin in 500 ml of normal saline. Thereafter, you position the patient sitting up and place an epidural for postoperative pain relief. The test dose is negative and, again, the patient is placed supine. Anesthesia is induced uneventfully with etomidate, sufentanil, vecuronium, and isoflurane in air. Because the patient has very poor IV access, you elect to put in a central line. A right internal jugular catheter is placed uneventfully and is seen to work well. The surgery starts and you elect to send an arterial blood sample to the laboratory for estimation of the usual parameters, including blood sugar. To your dismay you note that white “clumps” precipitate out of the sample. You repeat the test and fi nd the same result. However, blood from the central line does not show any “clumps.” You are wondering if you should be worried about this and if so why?