Q. Patient is brought in by paramedics after being found unconscious in a parking lot. Pt. presents with blunt head trauma and it is later determined that he syncopated after donating blood and subsequently smoking weed. What effect does blood donation have on the body?

A. Red blood cells (RBCs) contain iron; as a result, blood donation removes some iron from the donor’s body. The body needs iron from either preexisting iron stores or iron from previously consumed food to make new RBCs. If the iron level gets too low following donation, the body will not be able to make new RBCs, and the donor can possibly become anemic. Most people with low iron stores have no symptoms; however, some may have fatigue, decreased exercise capacity, lightheadedness, dizziness, or low blood pressure. Smoking weed will also lower blood pressure, among other physiological effects. These two circumstances (period following blood donation + substance use) may both have contributed to decreased BP levels in the pt, causing him to ultimately fall unconscious. Resources: http://www.ncbi.nlm.nih.gov/pubmed/18466177, http://bloodcenter.stanford.edu/donate/iron.php