Host Defenses

Sharp End

There will be two final readings:

1)The first is aimed at students planning to go into emergency medicine:

Is it possible that some common things we do in the emergency room are ill-advised because they interfere with host defenses?

The reading below includes a couple of short articles on the downsides of emergency interventions, activated charcoal for overdoses, fluids for trauma, and oxygen for chest pain. Consider blood clotting. It is clear that the mechanisms involved in hemostasis have been subjected to natural selection ever since the ancient circulatory system first emerged. As a result, blood clotting during trauma is a tightly regulated process with highly complex gene expression, platelet activity, clotting factor production, fibrinogen activation, and immune activation. Is it possible that IV fluids might disturb some of these processes? Perhaps IV fluids treat the doctor more than the patient, making us feel better because of improvements blood pressure and pulse. Meanwhile,  fluids can worsen hemostasis, increasing the risk of deadly hemorrhage.

I explored this issue in an article published last year in The Sharp End, an emergency medicine publication edited by my colleague Andy Brainard MD.

For the complete article and some very thought provoking articles about other well-intentioned but ill-advised medical interventions :Read More Here: The Sharp End

2) This second article is aimed as students going into behavioral health.

The topic of this article is the smoke detector principle, a concept described by Randy Nesse to explain why certain individuals seem prone to over-reacting to non-existent threats, as in panic disorder. As I wrote in “A clinical perspective on evolutionary medicine” with Mark Schwartz:

Other host defenses include the capacity to respond to pain and anxiety, thus limiting exposure to danger. Nesse observed that aversive symptoms, such as anxiety and panic, seem to afflict many people out of proportion to any potential threat. He argues that natural selection has shaped defensive responses that are akin to a smoke detector: highly sensitive to potential fires, but prone to frequent false alarms (Nesse and Williams 1994). In this signal-detection metaphor, a low threshold for activation of the fight-or-flight response, though energetically costly during a false alarm (anxiety or panic attack), can prevent the far higher fitness cost of being killed by a predator or conspecific. What appears to be “over-expression” could instead be the outcome of optimal regulation of a defense trait. Frequent false alarms can be expected when (1) the cost of a defense is less than the cost of the danger, (2) threats are unpredictable across time and space, and (3) signals conveying danger are imperfect (Nesse 2001).

Click here to read more about the smoke detector principle

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