Week 7: Choices, Choices...

Berenstein, Sos, Cobra, Pig-tail, Amplatz, Bentson, stiff-angled glide. This list of names may have the slight flavor of a membership roster of a motorcycle gang, but these devices are actually just a few of the many types of catheters and wires that make up the toolbox of an interventional radiologist.  At any given moment during a procedure the physician must decide which of the many different options to select for the job at hand.  I have found that medicine is full of choices, the selection of the right medical device, choosing the right drug, or the decision to go ahead with a treatment or not.  As I shadowed my clinical mentor this week, I tried to find out the reasons behind some the medical choices that he and his fellow physicians make every day.

Early in the week I met a patient exhibiting severe leg edema (swelling), pain and a feeling of heaviness, all symptoms indicative of venous obstruction in the lower extremities.  As my mentor specializes in thrombosis (clotting) and venous disease, I had seen several such patients throughout the summer.  Unfortunately, this particular patient had a problem. The patient had previously had a kidney removed and the one that was remaining was not functioning as well as it should. The contrast agent used ubiquitously by radiologists and interventional radiologists in particular, is toxic to the kidneys, and therefore the use of contrast was contraindicated for this patient.  My mentor left the patient with a choice: they could go ahead with the procedure, potentially risking renal damage that would require dialysis treatments, or avoid the procedure completely and the patient would have to live with the current symptoms.  There are, of course, alternatives to the contrast agent, in particular CO₂ gas.  However, CO₂ is not nearly as effective as highlighting thrombosis and stenosis as contrast and a distinct possibility existed that relying exclusively on CO₂ could mean the procedure was impossible to perform.  There really was no obvious choice and no medical data that could suggest what the most optimal decision would be.  It came down to a question that only the patient could answer: were the symptoms of the venous disease effecting the patient’s quality of life to an extent that the risk was worth taking?

Even if the patient decided to continue with the procedure numerous choices and decisions still remained.  Depending on the type of obstruction, i.e. thrombosis or simple occlusion due to compression of the vein, different methods would be employed to improve blood flow.  Within the realm of thrombosis, many different types of medical devices and techniques could be used to remove the blood clot.  One of the most effective devices for clearing a thrombosis is known as Angiojet.  The device employs a powerful vortex to disrupt the clot and enable it to be removed.  Unfortunately, the same vortex lyses red blood cells releasing factors into the blood stream, which are extremely harmful to the kidneys.  With the patient’s weakened renal system, the use of Angiojet was out of the question.   Another device I have seen implemented several times by IR physicians is known as Penumbra.  It is simply a vacuum pump that can be used to suck a blood clot straight out of a patient’s vein.  Unlike Angiojet, the Penumbra does not risk harming the patient’s kidneys, however, it has its own problems.  Most notably, while useful for small, localized clots such as those commonly seen in pulmonary embolism, the Penumbra seems to be less effective against extensive thrombosis.  Ultrasound had shown that for this particular patient the clot extended from the patient’s popliteal vein (knee) all the way into the common iliac vein in the pelvis, suggesting that the Penumbra would be of limited utility.  Yet a third option is a class of devices that are designed to mechanically break apart thrombosis with a rapidly spinning wire.  There are multiple variations of this device, but at least some of them can actually induce additional thrombosis by causing damage to the endothelial cells lining the blood vessels, thus making the problem worse. In addition, a variety of other treatment options exist, each with advantages and disadvantages.  It was up to my mentor to use his experience to select the most optimal option for the particular patient’s needs.

Once a thrombolysis (clot breakdown) or thrombolectomy (clot removal) is performed, anticoagulation medication (blood thinners) is prescribed for nearly every patient to help remove residual clot and ensure that the thrombosis does not return.  This decision is almost reflexive, yet a variety of different drugs exist, requiring another careful consideration of several options.  One of the oldest anticoagulation medications, called Coumadin (trade name Warfarin), is actually rat poison.  In rats, this drug causes massive internal bleeding, but a failed suicide attempt revealed that in humans, Coumadin has the potential to save lives by preventing the formation of blood clots.  One of the unique aspects of Coumadin is that vitamin K acts as an antidote and can rapidly neutralize the drug’s effects.  Lovanox is another anticoagulant.  It can be extremely effective at preventing thrombosis, but it must be administered via injection and has the potential to harm the kidneys.  A second drug that requires injection is Heparin.  Heparin is a protein naturally found in the body.  Unlike Lovanox, it doesn’t harm the kidneys, but it is not easy to obtain and so its use is typically restricted to hospitals.  Modern molecular biology research has resulted in a class of anticoagulants that target specific points in the clotting cascade including apixaban (Eliquis) and rivaroxaban (Xarelto).  No one drug can be said to be appropriate for all cases.  Every person responds differently to different chemicals requiring physicians to be flexible with their prescriptions, changing a patient’s medication if necessary to accommodate their response.  This is part of the reason physicians need to follow up with their patients: to understand whether the prescribed therapy has been effective.

Naturally a physician cannot force a patient to stick with a particular drug regimen.  The patient has the choice to follow the physicians orders, to ignore medical advice, or do something in between.  This freedom results in one of the largest outstanding problems in modern day medicine, known as patient compliance.  This week I attended a thrombosis board, a sort of conference for doctors in different fields to discuss several peculiar thrombosis patients and together decide upon the most optimal therapy for these patients.  One patient discussed, upon whom my mentor had performed a thrombolysis earlier in the summer, had suddenly stopped taking the prescribed anticoagulants halfway through the assigned time period.  This change has the potential to greatly increase the patient’s risk for thrombosis, yet at this point this is nothing the doctors can do beyond a strong recommendation that the patient return to using the medication. 

The choices that must be made every day in medicine by physicians, nurses, other clinicians and even the patient’s themselves are as diverse as disease types.  Unfortunately there is often not enough knowledge or information available to know which choice is the right one, or even what the best available option is.  It is up to biological researchers to continue to build upon the knowledge that currently exists to enable more intelligent decisions to be made and to biomedical engineers to design devices that can provide information that will help identify the best choice.  Often times, the more knowledge we gain, the more we realize how little we actually understand.  The quest for knowledge is a never-ending battle against the infinite complexities of nature, but it is one that I am eager to help fight.