Monday: 3 heroin overdoses. Most interesting tattoo to date: a lion-headed man having 'relations' with a monkey while a nude woman crawled around on all fours beneath them.
Tuesday: no cases. Gave a presentation on non-
cardiogenic pulmonary edema in heroin OD.
***Warning: gratuitous physiology lecture ahead ***
Basically about 80-90% of the fatal
OD's have this pink frothy fluid fill their lungs, sometimes to the degree that it comes out their nose and mouth. Why? The answer isn't fully known, despite this phenomenon being first described by Sir William
Osler in 1880.
From a physiologic standpoint, there are several reasons that fluid can be in the lungs. It can come from 2 possible places, from the lungs themselves or from the outside world. If water is introduced through the airway, as in drowning or near drowning, then obviously the lungs can have fluid in them. Fluid can also come from within the lungs themselves. Blood flows through the lungs from pulmonary arteries, to capillaries, then to pulmonary veins. If the venous drainage is diminished, then the fluid backs up and leaks out of the capillaries because the hydrostatic pressure is increased, thus causing edema. This is
analogous to kinking a hose, and water leaking out of the body of the hose. A situation which would cause this is failure of the left side of the heart, which normally
receives its blood from the lungs. This would be an example of "
cardiogenic" pulmonary edema, because it is caused ultimately by the heart. The inability of the left heart to pump causes fluid to back up and leak.
The foamy pulmonary edema seen in heroin overdose however, is non-
cardiogenic i.e. does not originate from intrinsic problem with the heart. There are several schools of thought as to what causes it. First, a word as to non-
cardiogenic causes of pulmonary edema. The pulmonary capillaries are where gas exchange takes place, where oxygen enters the blood and carbon dioxide leaves. By necessity, the membranes separating blood from air are thin, so that the gasses can move easily. If these membranes are damaged or rendered more permeable, then contents of blood can leak out. Blood is made up of primarily water, but also has proteins and of course red blood cells. If the holes in the pulmonary capillary membrane are small, then only water and protein leaks out. If the holes are bigger, then red blood cells themselves can leak out, tinging the fluid pink or even red, depending on how much blood
extravasates (leaves the circulation).
What causes holes these holes then? Histamine is one postulated player in this little drama. Most people are familiar with the effects of histamine through allergies. With hay fever or seasonal allergies, the eyes and nose have clear discharge, and sneezing is commonly a symptom. The clear runny discharge is caused in part by histamine which makes the blood vessels in the nose dilate, causing congestion. The blood vessels are also rendered more permeable, so they leak fluid, contributing to the runny nose (not the only component of the nasal discharge however). This is why you take anti-histamines like
Claritin or Zyrtec to alleviate hay fever symptoms. So, we see that histamine is able to make blood vessels more permeable and leaky. There is lots of histamine present in the lungs, so one thought is that histamine released in the lungs causes the pulmonary capillaries to be more leaky and causes fluid to leak from the blood vessels into the airway.
How does histamine relate to heroin though? Heroin is an opioid, which means that it is a synthetic derivative of morphine, which is the natural derivative of the
Papaver Somniferum poppy, the source for opium. Opiates of all kinds can cause release of histamine in varying degrees. Morphine is especially known for this, histamine is responsible for the itchy sensation some people encounter when they
receive morphine. Since heroin is
diacetyl morphine (morphine with two synthetically added
acetyl groups. I won't bore you with more organic chemistry). So, heroin, which is a synthetically modified morphine, can cause histamine release in the lungs, which increases permeability of the blood vessels, causing pulmonary edema.
(For the medical purists, I acknowledge that this is a simplification. The bulk of my readers are lay people married to medical students.
For some reason, they are also afraid to post comments when I post.)
*** End of gratuitous physiology lecture ***
Wednesday: Car accident. Luxury sedan v. semi truck.
Thursday: No cases
Friday: Heroin OD, GI bleed secondary to duodenal ulcer, questionable pancreatic/ GI neoplasm.
AND FOLKS, THUS ENDETH MY MEDICAL SCHOOL RESPONSIBILITIES.
48 months of studying, lectures, clinical responsibilities has come to an end. I now have 5 weeks before we move, and begin internship in June.
