One problem is a lipemic blood samples; the cloudy, opaque or “strawberry milkshake” appearance is from fat in the bloodstream. Triglycerides greater than 1000 mg per dL (11.3 mmol per L) can easily cause this appearance. Or your patient may simply have eaten a large fatty meal a few hours before having the blood sample drawn.
Another component of blood that creates a milky appearance is chylomicrons - a combination of fat globules and protein. This combination occurs in the small intestine, and moves through the intestinal walls into the lymph vessels. These vessels ascend to the upper thorax, merge into the thoracic duct which joins the left subclavian vein. The chylomicrons travel in the bloodstream until they are either stored or metabolized for energy. Given the close proximity of the thoracic duct and the CVAD tip location, it is easy to see why a blood sample drawn from a CVAD may be more likely to appear cloudy or milky.
White blood cells and platelets may clump together to form a cellular aggregate. They may appear white or opaque and do not disperse when the container is rotated or shaken. Visible white particles composed of lipid or fat material may also appear in blood samples in patients with hypercholesterolemia. Studies of white particulate matter in stored blood have proven to be WBCs and platelets along with other cellular fragments.