John Fiske Brown Associates, Inc.

 Blood is thicker than water.

 by L.L. Wickham, Ph.D.

Exactly what is the thickness of blood and what does it have to do with forensic consulting?  Density, specific gravity, and viscosity are measurements associated with the “thickness” of fluids.  Changes in the consistency or flow behavior of blood can determine whether a person dies of a heart attack, a stroke, or massive trauma.   Rheology, the study of flow behavior, considers a variety of blood components and physical measurements in order to understand which limiting factors may be responsible for whether blood flows, clots, sediments, aggregates or hemorrhages (bleeds).  A person may be predisposed to bleed or clot before an accident thereby affecting the extent and outcome of injury.  An investigation of medical records in combination with accident reconstruction can determine the importance of physiological variations and external factors on outcomes.

The percentage of red and white cells, packed cell volume or hematocrit, the number and types of proteins and fats in the plasma, the number of platelets, and the amount of oxygen in the red cells are examples of normal variations that affect flow, clotting and aggregation of blood.  Medications, diet, physical activity, and environmental factors also affect blood flow dynamics (hemorheology) and can determine the extent of injuries or whether a person survives.  Obviously, aspirin and anticoagulants will predispose a person to hemorrhage but there are many lesser-known contributors. Smoking prevents red cells from receiving oxygen and chemical changes cause blood cells to change shape and “adhesiveness” resulting in aggregation, coagulation, and sedimentation blood.  This can increase the blood’s viscosity making it flow slower or coagulate creating a vicious circle of increasing cellular oxygen deprivation spiraling towards hypoxia, asphyxia, and possible infarct (i.e. a heart attack or cerebral stroke).  Alcohol can cause dehydration due it’s diuretic effect resulting in a higher packed cell volume and viscosity but it also causes dilation of blood vessels, flushing and chemical changes resulting in predisposition to bruising and bleeding.  Hypothermic injury and death after excessive drinking in cold environments is often due, in part, to some of these effects.  Cases involving excessive bleeding and bruising in people taking over the counter dietary supplements such as fish oil are increasing with the popularity of homeopathy and the rising cost of prescription drugs.  Laypersons and a surprising number of clinicians can be unaware of dosage effects of many readily available products. Unsaturated fatty acids can be of great benefit to promote general health as well as prevent clotting and inflammation.  However, if a person is already predisposed to bleed or takes excessive amounts it can be detrimental.  Gingko biloba, a plant extract taken for purported memory and cognition enhancement, can have similar effects.   Some hemorrhagic stroke cases have involved the standard practice of advising anticoagulants (e.g. aspirin) to those with high cholesterol and/or high blood pressure without knowledge of their blood aggregation capabilities.   Many antidepressants and antibiotics can also increase bruising and bleeding.  Conversely, there are also many foods, supplements and drugs that can increase blood aggregation.  Some medication combinations have synergistic effects and the number of cases where patients are taking several drugs simultaneously is also increasing.  In one recent case, a patient took over 60 drugs; more than a dozen were within a time period of combined effect.  Blood flow behavior changes constantly in an individual and depends on many more factors than can be discussed in this forum.  Whether blood flows like water or honey, as Faust proclaimed: “Blood is a most remarkable juice”.