Monday, March 26, 2007

A fevered Earth

I don’t know who first thought of describing global warming in terms of a fever, but when Al Gore used the language while testifying before Congress last week, it really caught my attention. By suggesting a medical nature to the problem, he moved it from the purview of physicists, engineers, and environmental scientists to that of the medical community. Are we not the ones trained for and equipped to handle fevers? At Gore’s invitation, I’d like to think about this problem from a medical perspective and see if doing so can contribute something to its understanding and management.

The most important thing we know about fevers is that they cannot be ignored; they are a surefire sign that something is wrong, and that’s why we regard the temperature as the first vital sign. It is a powerful tool for stratifying the severity of medical problems. Without a fever, a cough is merely a bronchial irritation, but with one it is a pneumonia. A swollen joint from trauma is not an emergency, unless it is accompanied by fever, in which case the joint is presumed to be septic and must urgently be drained. The body has a highly refined control mechanism for temperature, and when it runs off course it is not by accident: we are obliged to assume that some pathologic tampering has occurred. For hospitalized patients, the minimum work-up required for a fever includes a chest x-ray, urine analysis, urine culture, and blood culture. A persistent fever of unknown origin may lead to CT scans, lumbar punctures, ultrasound evaluations, white blood cell scans, and often will trigger the initiation of empiric antibiotics. These are not pleasant things; they are painful and costly. The consequences of an undiagnosed and untreated fever are simply too great, however, for a fever ever to be brushed off.

Some fevers are iatrogenic, or man-made. They are caused by reactions to medications or as a result of i.v. lines and foreign bodies, and they are the best fevers to have because they are easily reversible by stopping the medication or removing the foreign body (granted, if it’s your prosthetic heart valve that’s causing the fever it’s not a good thing). If somebody says wait, you can’t prove that the fever is iatrogenic, and if they are right, you worry more, because natural causes of fevers tend to be more severe and difficult to treat. Flesh-eating bacteria, for example, will not stop their feasting if you simply ask them nicely. A fever of unknown origin is particularly worrisome because it suggests a deep-seated occult infection or inflammatory disease. It lurks and taunts and wears down the patient and her physician, defying diagnosis and thereby defying all sense of security. Two diagnoses are unnecessary– a single diagnosis is sufficient with fever and allows your searching to stop, but without that diagnosis you can never reassure a patient that her fever is benign.

This brings us back to the Earth. The Earth’s fever is caused either by carbon dioxide, as Mr. Gore and many suggest, or not, as many others suggest. Let us hope that Mr. Gore is right. The consequences of an undiagnosed and untreated earthly fever are catastrophic, and if we are not able to identify the problem quickly and address it appropriately, we may very well have a disaster coming. The Earth’s fever must be assumed to be pathologic; with a fever the burden always lies upon the medical team to prove that the fever is benign, rather than with the patient to demonstrate that the fever is malignant. Can Joe Barton and James Inhofe really reassure us that global warming is harmless? If they are to do so, they must first be able to provide us with a diagnosis. I don’t mind that they cast doubt on carbon dioxide as the cause of global warming, but what disturbs me is that they seem to find those doubts reassuring. Those doubts should be terrifying. If carbon dioxide indeed is not the culprit, we must raise the alert and vigilantly renew our scientific efforts until the true diagnosis is found. Until then, carbon dioxide toxicity remains the best working diagnosis and we should treat it aggressively.

Barton, Inhofe, and others who deny that global warming is a serious problem find themselves in an awkward position that we encounter frequently in medicine: that of holding a stance that by the nature of its incredible convenience is inherently suspect. They find themselves in the position of the medical resident who, after evaluating a patient with headache and fever, decides that a lumbar puncture to rule out meningitis is not necessary. This resident, even though he may have made a perfectly valid clinical decision, will face close scrutiny in the morning simply by virtue of the fact that he chose a clinical pathway that let him avoid a difficult and time-consuming procedure. His judgment and integrity are called into question, and in knowing this, the resident in advance must make sure that he stands on very solid ground. I ask Barton and Inhofe to imagine themselves as this medical resident, and to evaluate their positions in the same way that he might.

With headache and fever, though, lumbar puncture and antibiotics are almost always necessary. It’s considered preferable to make the diagnosis by LP than by autopsy. With global warming also, the consequences of a missed diagnosis are so great that we must err on the side of over-treatment. With an issue so complex, we are unlikely ever to arrive at absolute certainty regarding its causes and very best plan of treatment. However, we cannot afford to let our doubts stall us; after Katrina, such inaction would be utterly inexcusable. Granted, time will reveal the true nature of the Earth's fever – whether it is a passing fancy or a trend, malignant or benign, curable or not. Learned from the other side, though, that knowledge would be oh so unsatisfying.